High-Level Data Link Control by pengxiuhui

VIEWS: 8 PAGES: 291

									       Wide Area Network
•   WAN protocols
•   WAN solutions
•   Interface and cabling
•   configuration
  High-Level Data Link Control
• HDLC is the most important data link
  control protocol
• Widely used which forms basis of other
  data link control protocols
• Most WAN protocols use HDLC as data
  link control protocols
        HDLC Station Types
• Primary station (Unbalanced)
   – Controls operation of link
   – Frames issued are called commands
   – Maintains separate logical link to each secondary
     station
• Secondary station
   – Under control of primary station
   – Frames issued called responses
• Combined station (Balanced)
   – May issue commands and responses
   HDLC Link Configurations
• Unbalanced
  – One primary and one or more secondary
    stations
  – Supports full duplex and half duplex
• Balanced
  – Two combined stations
  – Supports full duplex and half duplex
    HDLC Transfer Modes (1)
• Normal Response Mode (NRM)
  – Unbalanced configuration
  – Primary initiates transfer to secondary
  – Secondary may only transmit data in response
    to command from primary
  – Used on multi-drop lines
  – Host computer as primary
  – Terminals as secondary
    HDLC Transfer Modes (2)
• Asynchronous Balanced Mode (ABM)
  – Balanced configuration
  – Either station may initiate transmission without
    receiving permission
  – Most widely used
  – No polling overhead
    HDLC Transfer Modes (3)
• Asynchronous Response Mode (ARM)
  – Unbalanced configuration
  – Secondary may initiate transmission without
    permission form primary
  – Primary responsible for line
  – rarely used
            Frame Structure
• Synchronous transmission
• All transmissions in frames
• Single frame format for all data and control
  exchanges
Frame Structure Diagram
                      Flag Fields
•   Delimit frame at both ends
•   01111110
•   May close one frame and open another
•   Receiver hunts for flag sequence to synchronize
•   Bit stuffing used to avoid confusion with data
    containing 01111110
    –   0 inserted after every sequence of five 1s
    –   If receiver detects five 1s it checks next bit
    –   If 0, it is deleted
    –   If 1 and seventh bit is 0, accept as flag
    –   If sixth and seventh bits 1, sender is indicating abort
 Bit Stuffing

• Example with
  possible errors
                 Address Field
• Identifies secondary station that sent or will
  receive frame
• Usually 8 bits long
• May be extended to multiples of 7 bits
   – LSB of each octet indicates that it is the last octet (1) or
     not (0)
• All ones (11111111) is broadcast
            Control Field
• Different for different frame type
  – Information - data to be transmitted to user (next
    layer up)
     • Flow and error control piggybacked on information
       frames
  – Supervisory - ARQ when piggyback not used
  – Unnumbered - supplementary link control
• First one or two bits of control filed identify
  frame type
• Remaining bits explained later
Control Field Diagram
               Poll/Final Bit
• Use depends on context
• Command frame
  – P bit
  – 1 to solicit (poll) response from peer
• Response frame
  – F bit
  – 1 indicates response to soliciting command
          Information Field
• Only in information and some unnumbered
  frames
• Must contain integral number of octets
• Variable length
    Frame Check Sequence Field
•   FCS
•   Error detection
•   16 bit CRC
•   Optional 32 bit CRC
            HDLC Operation
• Exchange of information, supervisory and
  unnumbered frames
• Three phases
  – Initialization
  – Data transfer
  – Disconnect
          Supervisory Frames
•   Receive Ready       --- RR
•   Receive Not Ready   --- RNR
•   Reject              --- REJ
•   Selective Reject    --- SREJ
         Unnumbered Frames
• Control operations
• Set up and take down communications link
• Maintenance
          The unnumbered format.
SABME (Set        1111P110 C     Request logical connection
Asynchronous
Balanced Mode)
DM (Disconnect    1111F000 R     Unable to establish or maintain logical
Mode)                            connection
UI (Unnumbered    1100P000 C     Used for unacknowledged information
Information)                     transfer
DISC              1100P010 C     Terminate logical connection
(Disconnect)
UA (Unnumbered    1100F110 R     Acknowledge SABME or DISC
Ack )
FRMR (Frame       1110F001 R     Unacceptable frame report
Reject )
XID (Exchange     1111*101 C/R Exchange identification information
Identification)
               Operations

• Connection Establishment
  – SABME ---->
  –        <----- UA
• Data Transfer
  – I-frames and
  – S-frames for flow and error control.
• Disconnect
  – Either entity can issue a DISC.
Examples of Operation (1)
Examples of Operation (2)
 Point to Point Data Link Control
• one sender, one receiver, one link: easier
  than broadcast link:
   – no Media Access Control
   – no need for explicit MAC addressing
   – e.g., dialup link, ISDN line
• popular point-to-point DLC protocols:
   – PPP (point-to-point protocol)
   – HDLC: High level data link control
PPP Design Requirements [RFC 1557]
  • packet framing: encapsulation of network-layer
    datagram in data link frame
     – carry network layer data of any network layer
       protocol (not just IP) at same time
     – ability to demultiplex upwards
  • bit transparency: must carry any bit pattern in the
    data field
  • error detection (no correction)
  • connection liveness: detect, signal link failure to
    network layer
  • network layer address negotiation: endpoint can
    learn/configure each other’s network address
          PPP non-requirements
•   no error correction/recovery
•   no flow control
•   out of order delivery OK
•   no need to support multipoint links (e.g.,
    polling)
    Error recovery, flow control, data re-ordering
            all relegated to higher layers!|
              PPP Data Frame
• Flag: delimiter (framing)
• Address: does nothing (only one option)
• Control: does nothing; in the future possible
  multiple control fields
• Protocol: upper layer protocol to which frame
  delivered (eg, PPP-LCP, IP, IPCP, etc)
           PPP Data Frame
• info: upper layer data being carried
• check: cyclic redundancy check for error
  detection
                 Byte Stuffing
• “data transparency” requirement: data field must
  be allowed to include flag pattern <01111110>
   – Q: is received <01111110> data or flag?


• Sender: adds (“stuffs”) extra < 01111110> byte
  after each < 01111110> data byte
• Receiver:
   – two 01111110 bytes in a row: discard first byte,
     continue data reception
   – single 01111110: flag byte
            Byte Stuffing
flag byte
pattern
in data
to send




                flag byte pattern plus
                stuffed byte in
                transmitted data
       PPP Data Control Protocol
Before exchanging network-
  layer data, data link peers
  must
• configure PPP link (max.
  frame length,
  authentication)
• learn/configure network
  layer information
   – for IP: carry IP Control
     Protocol (IPCP) msgs
     (protocol field: 8021) to
     configure/learn IP
     address
           Other DLC Protocols
             (LAPB,LAPD)
• Link Access Procedure, Balanced (LAPB)
  – Part of X.25 (ITU-T)
  – Subset of HDLC - ABM
  – Point to point link between system and packet
    switching network node
• Link Access Procedure, D-Channel
  –   ISDN (ITU-D)
  –   ABM
  –   Always 7-bit sequence numbers (no 3-bit)
  –   16 bit address field contains two sub-addresses
       • One for device and one for user (next layer up)
   Other DLC Protocols (LLC)
• Logical Link Control (LLC)
  – IEEE 802
  – Different frame format
  – Link control split between medium access layer (MAC)
    and LLC (on top of MAC)
  – No primary and secondary - all stations are peers
  – Two addresses needed
     • Sender and receiver
  – Error detection at MAC layer
     • 32 bit CRC
  – Destination and source access points (DSAP, SSAP)
        Other DLC Protocols
         (Frame Relay) (1)
• Streamlined capability over high speed
  packet switched networks
• Used in place of X.25
• Uses Link Access Procedure for Frame-
  Mode Bearer Services (LAPF)
• Two protocols
  – Control - similar to HDLC
  – Core - subset of control
          Other DLC Protocols
           (Frame Relay) (2)
•   ABM
•   7-bit sequence numbers
•   16 bit CRC
•   2, 3 or 4 octet address field
    – Data link connection identifier (DLCI)
    – Identifies logical connection
• More on frame relay later
   Other DLC Protocols (ATM)
• Asynchronous Transfer Mode
• Streamlined capability across high speed
  networks
• Not HDLC based
• Frame format called “cell”
• Fixed 53 octet (424 bit)
• Details later
                     X.25
• 1976
• Interface between host and packet switched
  network
• Almost universal on packet switched networks and
  packet switching in ISDN
• Defines three layers
   – Physical
   – Link
   – Packet
            X.25 - Physical
• Interface between attached station and link
  to node
• Data terminal equipment DTE (user
  equipment)
• Data circuit terminating equipment DCE
  (node)
• Uses physical layer specification X.21
               X.25 - Link
• Link Access Protocol Balanced (LAPB)
  – Subset of HDLC
  – Point to point link between system and packet
    switching network node
              X.25 - Packet
• External virtual circuits
• Logical connections (virtual circuits)
  between subscribers
X.25 Use of Virtual Circuits
        Virtual Circuit Service

• Virtual Call
  – Dynamically established
• Permanent virtual circuit
  – Fixed network assigned virtual circuit
Virtual Call
Packet Format
             Multiplexing
• DTE can establish 4095 simultaneous
  virtual circuits with other DTEs over a
  single DTC-DCE link
• Packets contain 12 bit virtual circuit number
Virtual Circuit Numbering
      Flow and Error Control
• HDLC at the link layer
• Sliding window at the VC layer
                Packet Sequences
• Complete packet sequences
• Allows longer blocks of data across network with
  smaller packet size without loss of block integrity
• A packets
   – M bit 1, D bit 0
• B packets
   – The rest
• Zero or more A followed by B
               Reset and Restart
• Reset
   –   Reinitialize virtual circuit
   –   Sequence numbers set to zero
   –   Packets in transit lost
   –   Up to higher level protocol to recover lost packets
   –   Triggered by loss of packet, sequence number error,
       congestion, loss of network internal virtual circuit
• Restart
   – Equivalent to a clear request on all virtual circuits
   – E.g. temporary loss of network access
Asynchronous Transfer Mode
         (ATM)
          Protocol Architecture
• Similarities between ATM and packet switching
   – Transfer of data in discrete chunks
   – Multiple logical connections over single physical
     interface
• In ATM flow on each logical connection is in
  fixed sized packets called cells
• Minimal error and flow control
   – Reduced overhead
• Data rates (physical layer) 25.6Mbps to
  622.08Mbps
Protocol Architecture (diag)
     ATM Logical Connections
• Virtual channel connections (VCC)
• Analogous to virtual circuit in X.25
• Basic unit of switching
• Between two end users
• Full duplex
• Fixed size cells
• Data, user-network exchange (control) and
  network-network exchange (network management
  and routing)
• Virtual path connection (VPC)
    – Bundle of VCC with same end points
ATM Connection Relationships
     Call
Establishment
 Using VPs
         VP/VC Characteristics
• Quality of service
• Switched and semi-permanent channel
  connections
• Call sequence integrity
• Traffic parameter negotiation and usage
  monitoring

• VPC only
   – Virtual channel identifier restriction within VPC
               ATM Cells
• Fixed size
• 5 octet header
• 48 octet information field
• Small cells reduce queuing delay for high
  priority cells
• Small cells can be switched more efficiently
• Easier to implement switching of small cells
  in hardware
ATM Cell Format
                Header Format
• Generic flow control
   – Only at user to network interface
   – Controls flow only at this point
• Virtual path identifier
• Virtual channel identifier
• Payload type
   – e.g. user info or network management
• Cell loss priority
• Header error control
     Generic Flow Control (GFC)
• Control traffic flow at user to network interface (UNI)
  to alleviate short term overload
• Two sets of procedures
   – Uncontrolled transmission
   – Controlled transmission
• Every connection either subject to flow control or not
• Subject to flow control
   – May be one group (A) default
   – May be two groups (A and B)
• Flow control is from subscriber to network
   – Controlled by network side
Single Group of Connections (1)
• Terminal equipment (TE) initializes two variables
   – TRANSMIT flag to 1
   – GO_CNTR (credit counter) to 0
• If TRANSMIT=1 cells on uncontrolled connection
  may be sent any time
• If TRANSMIT=0 no cells may be sent (on
  controlled or uncontrolled connections)
• If HALT received, TRANSMIT set to 0 and
  remains until NO_HALT
Single Group of Connections (2)
• If TRANSMIT=1 and no cell to transmit on any
  uncontrolled connection:
  – If GO_CNTR>0, TE may send cell on controlled
    connection
     • Cell marked as being on controlled connection
     • GO_CNTR decremented
  – If GO_CNTR=0, TE may not send on controlled
    connection
• TE sets GO_CNTR to GO_VALUE upon
  receiving SET signal
  – Null signal has no effect
        Header Error Control
• 8 bit error control field
• Calculated on remaining 32 bits of header
• Allows some error correction
HEC Operation at Receiver
     Cell Based Physical Layer
• No framing imposed
• Continuous stream of 53 octet cells
• Cell delineation based on header error
  control field
Cell Delineation State Diagram
     ATM Service Categories
• Real time
  – Constant bit rate (CBR)
  – Real time variable bit rate (rt-VBR)
• Non-real time
  – Non-real time variable bit rate (nrt-VBR)
  – Available bit rate (ABR)
  – Unspecified bit rate (UBR)
          Real Time Services
• Amount of delay
• Variation of delay (jitter)
        ATM Adaptation Layer
• Support for information transfer protocol not
  based on ATM
• PCM (voice)
   – Assemble bits into cells
   – Re-assemble into constant flow
• IP
   – Map IP packets onto ATM cells
   – Fragment IP packets
   – Use LAPF over ATM to retain all IP infrastructure
      Adaptation Layer Services
•   Handle transmission errors
•   Segmentation and re-assembly
•   Handle lost and mis-inserted cells
•   Flow control and timing
               Frame Relay
•   Designed to be more efficient than X.25
•   Developed before ATM
•   Larger installed base than ATM
•   ATM now of more interest on high speed
    networks
Frame Relay Background - X.25
•   Call control packets, in band signaling
•   Multiplexing of virtual circuits at layer 3
•   Layer 2 and 3 include flow and error control
•   Considerable overhead
•   Not appropriate for modern digital systems
    with high reliability
     Frame Relay - Differences
• Call control carried in separate logical connection
• Multiplexing and switching at layer 2
   – Eliminates one layer of processing
• No hop by hop error or flow control
• End to end flow and error control (if used) are
  done by higher layer
• Single user data frame sent from source to
  destination and ACK (from higher layer) sent back
 Advantages and Disadvantages
• Lost link by link error and flow control
  – Increased reliability makes this less of a
    problem
• Streamlined communications process
  – Lower delay
  – Higher throughput
• ITU-T recommend frame relay above
  2Mbps
          User Data Transfer
• One frame type
  – User data
  – No control frame
• No inband signaling
• No sequence numbers
  – No flow nor error control
                    Objectives
Upon completion of this chapter, you will
be able to perform the following tasks:
• Explain the advantages and disadvantages of various
  WAN connection types
• Select the appropriate WAN connection types to
  interconnect multiple sites
• Select the equipment that will suit the specific needs of
  each site
• select the proper equipment
                                                         77
      Remote Access Overview



                     Service provider




– Remote access networks connect sites
– Connection requirements vary depending on
  user requirements and cost
          WAN Connection Types
                   Synchronous serial
Dedicated


                   Asynchronous serial, ISDN

                            Telephone
Circuit-switched             company




                    Synchronous serial

Packet-switched              Service
                             provider
      Dedicated Connections




– Links are continuously available
Dedicated Serial Connections

           EIA/TIA-232, EIA/TIA-449,
           V.35, X.21, EIA-530

     CSU/DSU
                          CSU/DSU




    CSU/DSU
                          CSU/DSU
   Circuit Switching Connections
                                                   File
                                                  server


                  Telephone
                   company
                   network

                                                  E-mail
                                                  server



– Circuit switching requires call setup and call teardown
– Circuit switching is used in the telephone company networks
  and works like a telephone call
   Asynchronous Circuit-Switched
           Connections

          EIA/TIA-                  Modem
            232       Telephone
                       company
                       network        EIA/TIA-
             Modem                      232


                                  Modem




– Connections are made only when traffic dictates a
  need
Circuit-Switched ISDN
     Connections
  BRI
          NT1
                            ISDN
                  Switch   service
  PRI                      provider
        CSU/DSU
   Packet-Switched Connections
                Synchronous
                serial
      CSU/DSU
                                   Synchronous
                                   serial

                                         CSU/DSU
      CSU/DSU




– VCs are established
– Packet-switched networks generally share
  bandwidth, but the cost is cheaper than a
  leased line
            Typical WAN Protocols
                       PPP, HDLC, SLIP
Dedicated



                          PPP, SLIP

Circuit-switched           Telephone
                            company



                    X.25, Frame Relay, ATM

                           Service
Packet-switched            provider
 PPP Encapsulation
            Multiple protocol
            encapsulations using NCPs
            in PPP

TCP/IP
                                PPP
IPX                         encapsulation
Appletalk




                          Link setup and control
                            using LCP in PPP
X.25 and Frame Relay
   Encapsulations



        Frame Relay,
            X.25
Connection Selection
  Considerations
–   Availability
–   Bandwidth
–   Cost
–   Ease of management
–   Application traffic
–   Quality of service and reliability
–   Access control
 Selecting WAN Configuration Types
                     Delay-
                  sensitive            ISDN, VoFR, VoATM
                voice/video


                       File
   Increasing      transfer   Analog          Or            Or
  Bandwidth                   dialup
                                             ISDN          Frame
Requirements                                               Relay
                    Client/
                    server


                    E-mail
                                  Analog dialup

                  Terminal
                 emulation    0          1           2             3+
                                             Hours/Day
WAN Connection Speed
    Comparison

                   Leased line, Frame Relay

                      ISDN—PRI

        X.25, ISDN—BRI

  Asynchronous
         Dialup

9.6k    56/64 kbps 128 kbps    E1/T1    E3/T3

       Theoretical Maximum WAN Speeds
       WAN Connection Summary
Connection Type Applications
                High control, full bandwidth, high-cost enterprise
Leased lines
                networks, and last-mile access
                Medium control, shared bandwidth, medium-cost
Frame Relay     enterprise backbones; branch sites
ISDN            Low control, shared bandwidth, more bandwidth
                than dialup
                Low control, shared bandwidth, variable cost-
Asynchronous
dialup          effective for limited use connections, high
                reliability
X.25            Low control, shared bandwidth, variable cost-
                effective for limited use connections like DDR
            Company Sites
                                       Central site,
                                       headquarters,
                                       enterprise




                          ISDN/
Windows                   analog
          Modem
 95 PC                                       Packet-switched
                                                 service
 Telecommuter site,
 small office/home
 office (SOHO),
 mobile (remote
 telecommuters)
                      Remote site,
                      remote office/
                      branch office
                      (ROBO)
                                                               93
    Central Site
   Considerations
                            Central site,
                            headquarters,
                            enterprise




                          ISDN/
                          analog            Packet-
                                            switched
                                             service




– Must provide access to multiple users and control
  the network costs
                                                       94
Branch Office Considerations


                 ISDN/                Packet-
                 analog              switched
                                      service




               Remote site,
               remote office/
               branch office
               (ROBO)

– Must be able to access the central site
                                                95
                   Telecommuter Site
                    Considerations

                       ISDN/           Packet-
                       analog         switched
Windows    Modem                       service
 95 PC
     Small office/
 home office (SOHO),
   mobile (remote
   telecommuters)




– Must access company information on demand
  from various remote locations
                                                 96
Determining the Appropriate
Interfaces—Fixed Interfaces
      Fixed-configuration router
Determining Appropriate Interfaces—
        Modular Interfaces
                             Serial WAN interface card




1-Ethernet 2-WAN interface
card module                                Modular-configuration router




               8-port A/S serial module
                      Summary
After completing this chapter, you should
be able to perform the following tasks:

 • Determine if each site is a central site, branch office, or
   telecommuter site

 • Select the products that will suit the specific needs of
   each site

 • select the proper equipment

                                                            99
              Review Questions

• Identify the types of WAN connections discussed in this
  chapter and the appropriate protocols used on each
  connection.

• Describe the considerations when implementing a WAN
  connection at a central site, branch office, and
  telecommuter site.

• Identify available equipment designed for a telecommuter
  site, a branch office, and a central site.
         Assembling and
        Cabling the WAN
          Components

3-101
                     Objectives
Upon completion of this chapter, you will
be able to perform the following tasks:

• Identify and connect necessary components to connect a central
  site router to other users

• Identify and connect necessary components to connect a branch
  office router to other sites

• Identify and connect necessary components to connect a
  telecommuter site router to other sites

• Identify and connect necessary components to connect a
  mobile user to other sites                                102
        Typical Network Topology
                                                               Central site
                                                 Modem



                                                                                       AAA server
                         BRI
                                                         PRI
                                                                              Serial
                                       ISDN/analog

Windows 95 PC   Modem          Async                                           Frame Relay
                                                                                  service
     Telecommuter site
                                          BRI



                                                               Serial




                                       Branch office



                                                                                                    103
      Central Site Router Equipment
 4-port serial WAN network module   Digital modem network module




Module                                                             Module
 slot 3                                                            slot 2

Module                                                             Module
 slot 1                                                            slot 0




  1-port CT1/PRI-CSU network         1-Ethernet 2-WAN card
  module                             slot network module
  Branch Office Router Equipment
   1600 router—
   front view



                                                            Serial WAN
                                                         interface card


  1603 router—rear view




Ethernet    Ethernet      ISDN BRI   Console Flash
10BaseT     AUI                              card slot
          Telecommuter Site Router
                 Equipment
   760 router—
   front view



  766 router—
  rear view




Console                                       Power switch
   Ethernet      ISDN
                            Phone 2   Power connector
   10BaseT       BRI
                         Phone 1
                 S/T
                     ISDN
                     BRI U
                    Assembling the Network
                                                                                     Central site
                                                                                     Cisco 3600
                   Cisco 700
                                                               Modem        Serial           Ethernet
                                                        1                   RS232
                                     2
Windows 95 PC   Ethernet                                                                                  AAA server
                                         BRI (RJ-45)   RJ-11
                                                                                                     Serial V.35, X.21, RS232,
                                                                             T1 (E1) for PRI         EIA/TIA-449, EIA-530

                                                  ISDN/analog
                                                                             RJ-48 (DB-15)                                   5
                                                                              3 or 4
                  Internal PC       RJ-11                                                            Frame Relay
                  modem
                                1                                                                       service
         Telecommuter site
                                                            BRI (RJ-45)

                                                               2
                                                                                       Serial V.35, X.21, RS232,
                                                                                       EIA/TIA-449, EIA-530
                                                                   Serial
                                                                                             5
                                                   Cisco 1600
                                                 Branch office



                                                                                                                       107
                Verifying Central Site
                     Installation
                                 Enable LED   MICA module bank LEDs




  CN/LP, RXC, RXD,
TXC, and TXD LEDs                                                     Enable
                                                                      LED




                                 Enable
                                 LED




  Remote Alarm, Local Alarm, Loopback,         Activity Link
  and Carrier Detect LEDs                         LED LED
       Verifying Branch Office
             Installation


     System power
                    System OK   Serial   CONN LED




• The system power and OK LEDs indicate the
  router is on and has successfully booted
   Verifying Telecommuter Site
           Installation
Ready LED




• The ready LED indicates the router is on
  and has passed its self tests
                      Summary
After completing this chapter, you should
be able to perform the following tasks:
• Identify and connect necessary components to connect a central
  site router to other users

• Identify and connect necessary components to connect a branch
  office router to other sites

• Identify and connect necessary components to connect a
  telecommuter site router to other sites

• Identify and connect necessary components to connect a
  mobile user to other sites
                                                            113
             Review Questions


• Which cables are necessary to make the proper physical
  asynchronous serial, ISDN, and synchronous serial
  connections?

• How can you verify that you properly installed a network
  module into a modular router?
 Configuring Asynchronous
Connections to a Central Site
       with Modems
                Objectives


Upon completion of this chapter, you
will be able to perform the following tasks:
• Configure an access server for an attached modem
• Use reverse Telnet to configure an external modem
• Configure a modem using autoconfigure
                        Chapter Activities
                                                                  Central site
                                                    Async
                Cisco 700



                                                                                      AAA server
                            BRI

                                                            PRI                  Frame Relay
                                          ISDN/analog

Windows 95 PC   Modem             Async                                           Frame Relay
        Small office                                                                service

                                             BRI



                                                                  Frame Relay




                                          Branch office
    A Typical Modem Connection
                                        Telco                              Modem
     Modem
                      Switch                             Switch

                                                                                   Host




Digital      Analog                   Digital                     Analog     Digital
                               PCM-encoded analog data
      The DTE-DCE Interface

  EIA/TIA-232             EIA/TIA-232
    or X.21                 or X.21



DTE         DCE        DCE              DTE



 • DTE = Data terminal equipment
 • DCE = Data communications equipment
    Modem Signaling—Data
      DTE                            DCE




Data     TxD   2                2   TxD
      {
transfer RxD   3                3   RxD
Ground GRD     7                7   GRD

                   DB-25 pins
           Asynchronous communication
                           P bits per packet

   Start     0       1       1       0        1      0       0      Stop
    bit                                                              bit



Ideal
RX Clock

Actual
RX Clock

 Asynchronous communications sometimes used for links with short packets.
      Modem Control Example
Two ways to terminate an existing connection:
• DTE-initiated
  —Access server drops DTR
  —Modem must be programmed to terminate connection on loss of
   DTR and restore to saved settings in its NVRAM
• DCE-initiated
  —Access server detects Carrier Detect (CD) low and
   terminates connection
  —Modem must be programmed so that CD reflects the state of the
   carrier
          Modem Operation
TxD                                                  RxD

            Buffer      Flow control   Buffer
CTS                                                  RTS
                         Compress
      Compressor        Decompress
                                       Compressor

       Packetizer        Checksum       Packetizer
      (error control)   Retransmit     (error control)

   Modulator/                           Modulator/
  demodulator                          demodulator
           DTE-to-DTE Wiring

            TxD    2        2    TxD
Data
transfer    RxD    3        3    RxD
            GND    7        7    GND

Hardware     RTS   4        4    RTS
flow control
             CTS   5        5    CTS
Modem       DTR    20       20   DTR
control
            DSR    6        6    DSR

               Null modem cable
            (with DB-25 connectors)
              Error Control and Data
              Compression Standards
                                                 Data



• Error detection/correction
   — Microcom Networking Protocol (MNP)   • Data compression
       • MNP 2–4 in public domain            — MNP 5: 2:1 ratio
       • MNP 10 for cellular                 — V.42bis: 4:1 ratio
   — CCITT V.42
       • LAP-M
       • MNP 4
  Modem Modulation Standards
     DCE                                      DCE


• ITU standards:
  – V.22: 1200 bps
                                  • Proprietary methods:
  – V.22bis: 2400 bps               – V.32 terbo: 19.2 kbps

  – V.32: 9600 bps                  – V.fast: 28.8 kbps

  – V.32bis: 14.4 kbps              – V.FC: 28.8 kbps

  – V.34: 28.8 kbps                 – K56Flex: 56 kbps

  – V.34 annex 1201H: 33.6 kbps     – X2: 56 kbps

  – V.90: 56 kbps
Modem Speeds and Compression

             4:1                   4:1
         Compression           Compression
            ratio                 ratio


DTE       DCE                    DCE            DTE

                   28.8 kbps
 115.2 kbps                            115.2 kbps



 • The speeds and compression ratios shown
   assume ideal conditions
                         Theoretical Speeds
                                              Maximum speed with 4:1
                 Speed                        V.42bis compression
  V.90           56000                                  224000



  V.34     28800                     115200


   V.32 19200                76800
  turbo

V.32bis   14400          57600


  V.32    9600    38400


                                                  bps
    Maximum Capacity/Data Rate
  Shannon Capacity:
            C  B log 2 (1  S / N )
Bandwidth of link                  Signal-to-Noise ratio

For example:
    Bandwidth of telephone link from telephone to a
     typical home is approx 3300Hz – 300Hz = 3kHz
    Signal-to-noise ratio is approx 30dB = 10log10(S/N)
    Therefore, C = 3000*log2(1001) ~= 30kb/s
     Connecting to the Modem

Forward connection to a router to login
                     Basic
                  telephone
                    service



                              Asynchronous line




Reverse connection
to a modem to configure it
   Configuring PPP and
Controlling Network Access
   with PAP and CHAP
                   Objectives

Upon completion of this chapter, you
will be able to perform the following
tasks:
• Configure PPP between a central site and a remote site
• Configure PAP or CHAP authentication
• Verify and troubleshoot a PPP link
                       Chapter Activities
                                                    Async         Central site
                Cisco 700                                         Cisco 3640



                                                                                      AAA server
                            BRI

                                                            PRI                  Frame Relay
                                          ISDN/analog

Windows 95 PC   Modem             Async                                           Frame Relay
                                                                                    service
        Small office
                                             BRI



                                                                  Frame Relay



                                           Cisco 1600
                                          Branch office
   Remote Node Connections
Novell IPX
   TCP/IP
AppleTalk

                PPP
   TCP/IP      SLIP
               ARAP



AppleTalk
OSI layer
             PPP Architecture
    3               Upper-layer protocols
                    (such as IP, IPX, AppleTalk)

             Network Control Protocol (NCP)
              (specific to each network-layer protocol)
    2
                Link Control Protocol (LCP)
            High-Level Data Link Control (HDLC)
                         Physical Layer
    1
               (such as EIA/TIA-232, V.24, V.35, ISDN)
                  Autoselect
            Autoselect     Yes        Parse start sequence for each
 User
dials in       on?                          enabled protocol

             No                  CR      PPP         SLIP        ARAP
                                         frame       frame       frame
            Start EXEC
           (or dedicated
               mode)                  Start      Start       Start
                                      PPP        SLIP        ARAP

                                       (Start as if run from EXEC)
     Enabling PPP and Async
      Interface Commands
Router(config-if)#encapsulation {ppp | slip}

• Defines encapsulation type

Router(config-if)#async mode dedicated

• Places the line in dedicated PPP/SLIP mode
                    OR
Router(config-if)#async mode interactive

• Places the interface in interactive mode
  (allows an EXEC process)
 Async Interface Commands for
          Addressing
Router(config-if)#peer default ip address
             {address | pool pool-name | dhcp}
• Assigns an IP address to a remote node

Router(config-if)#async dynamic address

• Allows a remote user to specify the IP address

Router(config-if)#ip unnumbered type number

• Configures the asynchronous interface to be
  unnumbered
            PPP LCP Options
                                        PAP or CHAP

Authentication              PSTN/ISDN




Callback            PSTN/ISDN




                         Data

Compression


Multilink

                   Bundle
                PPP Authentication
                                        Check
                                         local            Pass
                                       database


                             Local
                  Determine                                       Start
Incoming PPP                                  Fail
                authentication                       Disconnect
  negotiation      method                                         PPP
                            Security
                             server
                                        Query
                                       security
                                        server            Pass
                                       database
                     No
                authentication
         PPP Negotiating PAP
           Authentication
 Remote user                          Access server
    John                                 Cisco1
                      Run PPP            Local user
                                          database
                      Use PAP
Inputs name and                       username john
password when                         password urbiz
prompted            “john, urbiz”

                   Accept or reject



                  • One-way PAP
    Configuring PAP Example
 Left                                                 Right
                        PSTN/ISDN
router                                                router



                              hostname right
hostname left
                              int async 0
int async 0
                              encapsulation ppp
encapsulation ppp             ppp authentication PAP
ppp authentication PAP        ip add 10.0.0.2 255.255.255.0
ip add 10.0.0.1               dialer-map ip 10.0.0.1
255.255.255.0                   name left 555-4321
                              ppp pap sent-username right
dialer-map ip 10.0.0.2
                                password right1
  name right 555-2345
ppp pap sent-username left
  password left1

                         • Two-way PAP
PPP Using CHAP Authentication
Remote user                               Access server
  John                  Run PPP              Cisco1
                                            Local user
                        Use CHAP             database

Name: john        Request for challenge   username john
Password: urbiz                           password urbiz
                        Challenge

                        Response

                     Accept or reject


                  • One-way CHAP
        CHAP in Action—Call
              User dials in
766-1
                              3640-1
  CHAP in Action—Challenge
          User dials in
766-1
                              3640-1


        01 id random 3640-1
    CHAP in Action—Response
                  User dials in
 766-1
                                      3640-1


user pass
3640-1 pc1      01 id random 3640-1



 MD5

         hash
   CHAP in Action—Response
            (cont.)
                        User dials in
 766-1
                                                3640-1


user pass
3640-1 pc1         01 id random 3640-1



                02 id     hash          766-1
 MD5

         hash
  CHAP in Action—Verification
                         User dials in
  766-1
                                                     3640-1

user pass                                        user     pass
3640-1 pc1          01 id random 3640-1          766-1    pc1




                 02 id    hash           766-1
                                                         MD5
  MD5

          hash                                      =?         hash
          CHAP in Action—Result
                        User dials in
 766-1
                                                    3640-1
user pass                                       user    pass
3640-1 pc1         01 id random 3640-1          766-1   pc1




                02 id    hash           766-1
                                                    MD5
 MD5
                                                          hash
         hash
                   03 id “Welcome in”
  Configuring CHAP Example
 Left                                                        Right
                             PSTN/ISDN
router                                                       router


                                         hostname right
   hostname left                         username left password
                                           sameone
   username right password
     sameone                             int async 0
   int async 0                           encapsulation ppp
   encapsulation ppp                     ppp authentication CHAP
   ppp authentication CHAP
 PPP Callback Implementation
       Considerations
                                              Callback
        Callback
                                               server
         client         Initiating call



   Hold-queue started

                                               Rotary group
        Callback                                    (all busy)
         client



                        Client called
                                          X
                                               Callback
                                                server

Return call is not made if:
• The last interface is in use when callback is attempted
• A DDR interesting packet used last available interface
     Asynchronous Callback
      Operation Flowchart
  Call
             Authenticate
Autoselect      CHAP              Hangup
 protocol




              Callback            Authen.
                            Yes    OK?

                                      No

                                   End
            PPP Callback Operation
   Callback client                                  Callback server




              Call initiation   1
                                2   Call acknowledgment
       User authentication      3
                                4   Server-to-client dial string identified
Initiating call disconnected    5
                                6   Client called
            Authentication      7
                                8
                      Connection proceeds
  Asynchronous Callback Global
          Commands
Router(config)#username username
     [password password]
     [callback-dialstring phone-number]
     [callback-line line-number]
     [callback-rotary rotary-group-number]




          • On the callback server
       Asynchronous Callback
      Line/Interface Commands

Router(config-if)#ppp callback accept

Router(config-if)#ppp callback initiate

Router(config)#line line-number
Router(config-line)#callback forced-wait seconds
Router(config-line)#script callback script-name

           • On the callback server
         Configuring a PPP Callback
                   Server
         Callback client                            Callback server



          Dallas 10.1.1.8 5555678
                                                  Plano 10.1.1.7 5551234

    Plano(config)#interface s2
1   Plano(config-if)#ip address 10.1.1.7 255.255.255.0
    Plano(config-if)#encapsulation ppp
2   Plano(config-if)#dialer callback-secure
3   Plano(config-if)#dialer map ip 10.1.1.8 name Dallas class dial1 5555678
    Plano(config-if)#dialer-group1
4   Plano(config-if)#ppp callback accept
5   Plano(config-if)#ppp authentication chap
    !
    Plano(config)#map-class dialer dial1
6   Plano(config-map-class)#dialer callback-server username
7   Plano(config-map-class)#dialer hold-queue timeout 60
      Configuring a PPP Callback
                Client
      Callback client                      Callback server



      Dallas 10.1.1.8 5555678
                                         Plano 10.1.1.7 5551234




    Dallas(config)#interface s0
    Dallas(config-if)#ip address 10.1.1.8 255.255.255.0
1   Dallas(config-if)#encapsulation ppp
2   Dallas(config-if)#dialer map ip 10.1.1.7 name Plano 5551234
    Dallas(config-if)#dialer-group 1
3   Dallas(config-if)#ppp callback request
4   Dallas(config-if)#ppp authentication chap
         Supported Compression
              Algorithms
               Compression                 Decompression
                                128 kbps

128–384 kbps                  Compressed            128–384 kbps
                                 data




                 Data
                                       • Predictor
                 2:1 to 3:1
                Compression
                                       • Stacker
                    ratios
                                       • MPPC
                                       • TCP header
  Configuring Compression
Router(config)#int s2
Router(config-if)#compress {predictor | stac | mppc}


 • Interface compression algorithms
Router(config)#int async 2
Router(config-int)#ip tcp header-compression


Router(config)#int async 2
Router(config-int)#ip tcp header-compression passive

• TCP header
Why Use Multilink PPP?
                    Not Cisco
                      Brand
           Bundle
                        X

   Cisco
  access
  server


           Bundle

                      Cisco
                     access
                     server
Multilink PPP Operation
          LCP option negotiation

                   MRRU




                  Bundle




• Synchronize multiple PPP data streams
                  Summary

After completing this chapter, you should
be able to perform the following tasks:
• Configure PPP between a central site and a remote site
• Configure PAP or CHAP authentication
• Verify and troubleshoot a PPP link
     Review Questions


• What are the LCP options for PPP?
• Describe why PPP callback is important.
• Describe how CHAP provides security.
           An Introduction to X.25
                             X.25 cloud
LAN                                                      LAN
protocol                                                 protocol

           X.25                                  X.25
                   Virtual
                   circuit

            •   IP                  •   DECnet
            •   AppleTalk           •   ISO-CLNS
            •   Novell IPX          •   Compressed TCP
            •   Banyan VINES        •   Bridging
            •   XNS
           X.25 Protocol Stack
    OSI Reference Model   X.25 Protocol
7        Application            •

6        Presentation           •

5          Session              •

4         Transport             •

3         Network              X.25       3

2         Data Link           LAPB        2

1          Physical          Physical     1
           X.25 DTE and DCE
       Public data network (PDN)
              X.25           X.25
X.25 DTE      DCE            DCE        X.25 DTE




– X.25 DTE—Usually a subscriber's router or PAD
– X.25 DCE—Usually a PDN's switch or concentrator
                Identifying the PAD
               Public data network (PDN)

        PAD
                    DCE                     DCE


          DTE    X.25                             X.25
                                                         DTE host

Asynchronous
terminals



       – PAD collects data and outputs it into X.25 packets
X.25 (X.121) Addressing Format
   4 decimal digits      Up to 10 or 11 decimal digits

  Data network ID code     Network terminal number




   – Addressing set by service provider
        X.25 Address Resolution
                                                          Token
                          X.25                             Ring




               ARP                                X.25 map


ETH Destination Source           X.25   Source   Destination
                         IP                        X.121          IP
       MAC       MAC                    X.121
IP network
                X.25 Encapsulation                           IP network




                                 X.25




              Data-link
              frame         X.25
              (LAPB) (L2)   header (L3)   IP datagram (L3)



     – Protocol datagrams are reliably carried inside LAPB
       frames and X.25 packets
        X.25 Virtual Circuits




Switched virtual circuits   Permanent virtual circuits
       (SVCs)                      (PVCs)


 – Numbering for up to 4095 VCs per X.25 interface
             SVC Usage
            IPX




     Host




– SVCs may be combined to improve throughput for a
  particular protocol
Single-Protocol Virtual Circuits
                                              IPX
                                              TCP/IP
                                              AppleTalk
        Host




  – Each network-layer protocol is
    associated with its own virtual circuit
Multiprotocol Virtual Circuits
                                        IPX
                                        TCP/IP
                                        AppleTalk
    Host




 – Multiple protocols are carried within a virtual
   circuit to a single destination
 – A maximum of nine protocols may be
   mapped to a host
   X.25 Configuration Tasks




– Interface configuration
  – Select X.25 DTE or DCE encapsulation
  – Configure parameters for X.25 network attachment
  – Map protocol address to X.121 address
  – Additional configuration steps
Configuring X.25 SVCs—Steps 1
  Step 1     and 2
  Router(config-if)#encapsulation x25 [dte | dce]



     – Defines encapsulation type

 Step 2

  Router(config-if)#x25 address x.121-address
     – Establishes interface address
   Configuring X.25 SVCs—Step 3
Router(config-if)#x25 map protocol address x.121-address [options]



   – Specifies how a single protocol reaches a destination

 or
Router(config-if)#x25 map protocol address [protocol2 address2]*
x.121-address [options]

   – Specifies how multiple protocols reach a single
     destination using one SVC
Configuring X.25 SVC Example
 Central(config)#interface serial 1                      Central     site
 Central(config-if)#encapsulation x25
 Central(config-if)#x25 address 311082194567
 Central(config-if)#ip address 10.60.8.1 255.255.248.0
 Central(config-if)#x25 map ip 10.60.8.2 311082191234 broadcast


         Central site                               Branch office
 Token                  S1                     S0
  Ring
                               X.25
     IP address: 10.60.8.1              IP address: 10.60.8.2
     X.121 address: 311082194567        X.121 address: 311082191234

Branch(config)#interface serial 0                      Branch       office
Branch(config-if)#encapsulation x25
Branch(config-if)#x25 address 311082191234
Branch(config-if)#ip address 10.60.8.2 255.255.248.0
Branch(config-if)#x25 map ip 10.60.8.1 311082194567 broadcast
Configuring X.25 SVC Example
 Central(config)#interface serial 1                      Central    site
 Central(config-if)#encapsulation x25
 Central(config-if)#x25 address 311082194567
 Central(config-if)#ip address 10.60.8.1 255.255.248.0
 Central(config-if)#x25 map ip 10.60.8.2 311082191234 broadcast
 Central(config-if)#x25 map ip 10.60.8.3 311082198901 broadcast


         Central site                               Branch office
 Token                  S1                     S0
  Ring
                               X.25
     IP address: 10.60.8.1              IP address: 10.60.8.2
     X.121 address: 311082194567        X.121 address: 311082191234

                                                    Branch office


                                        IP address: 10.60.8.3
                                        X.121 address: 311082198901
 Configuring X.25 PVCs—Steps 1
               to 3
Step 1
Router(config-if)#encapsulation x25 [dte | dce]

  – Defines encapsulation type
Step 2
 Router(config-if)#x25 address x.121-address
  – Establishes interface address
Step 3
Router(config-if)#x25 pvc circuit protocol address
[protocol2 address2]* x.121-address [options]


  – Specifies how protocols reach a destination using a PVC
Configuring X.25 PVC Example
 Central(config)#interface serial 1                      Central site
 Central(config-if)#encapsulation x25
 Central(config-if)#x25 address 311082194567
 Central(config-if)#ip address 10.60.8.1 255.255.248.0
 Central(config-if)#x25 pvc 4 ip 10.60.8.2 311082191234 broadcast


         Central site                                Branch office
 Token                  S1                      S0
  Ring
                                  X.25
                                                        PVC 4
    IP address: 10.60.8.1                IP address: 10.60.8.2
    X.121 address: 311082194567          X.121 address: 311082191234

Branch(config)#interface serial 0                      Branch office
Branch(config-if)#encapsulation x25
Branch(config-if)#x25 address 311082191234
Branch(config-if)#ip address 10.60.8.2 255.255.248.0
Branch(config-if)#x25 pvc 3 ip 10.60.8.1 311082194567 broadcast
Additional X.25 Configuration
            Tasks



 – Configure interface for X.25 Layer 3 parameters
    –   Virtual circuits
    –   Packet size
    –   Window size
    –   Window modulus
  Configuring X.25 VC Ranges
                 Range   Default       Command
PVCs            1–4095             x25 pvc circuit


SVC
Incoming only   1–4095    0        x25 lic circuit
                1–4095    0        x25 hic circuit
SVC
Two-way         1–4095    1        x25 ltc circuit
                1–4095    1024     x25 htc circuit
SVC
Outgoing only   1–4095    0        x25 loc circuit
                1–4095    0        x25 hoc circuit
Configuring X.25 Packet Sizes
 Router(config-if)#x25 ips bytes



         – Specifies default incoming packet size



 Router(config-if)#x25 ops bytes
         – Specifies default outgoing packet size
     Configuring Window Parameters

Router(config-if)#x25 win packets   Router(config-if)#x25 wout packets

  – Specifies default unacknowledged
    packet limits


Router(config-if)#x25 modulo modulus

  – Defines packet-level window counter limit
Additional X.25 Configuration
Options Example
                                   X.25
                                  network

           S0




  Router(config)#interface serial 0
  Router(config-if)#encapsulation x25

  Router(config-if)#x25   address 311082198756
  Router(config-if)#x25   ips 1024
  Router(config-if)#x25   ops 1024
  Router(config-if)#x25   win 7
  Router(config-if)#x25   wout 7
Verifying X.25 Configuration
CentralA#sh int s 3/1
Serial3/1 is up, line protocol is up
Hardware is CD2430 in sync mode
Internet address is 10.140.1.1/24
MTU 1500 bytes, BW 128 Kbit, DLY 20000 usec, rely 255/255, load 1/255
Encapsulation X25, loopback not set
X.25 DTE, address 311010100101, state R1, modulo 8, timer 0
Defaults: idle VC timeout 0
cisco encapsulation
input/output window sizes 2/2, packet sizes 128/128
Timers: T20 180, T21 200, T22 180, T23 180
Channels: Incoming-only none, Two-way 1-1024, Outgoing-only none
RESTARTs 1/0 CALLs 0+0/0+0/0+0 DIAGs 0/0
LAPB DTE, state CONNECT, modulo 8, k 7, N1 12056, N2 20
T1 3000, T2 0, interface outage (partial T3) 0, T4 0
VS 5, VR 3, tx NR 3, Remote VR 5, Retransmissions 0
Queues: U/S frames 0, I frames 0, unack. 0, reTx 0
IFRAMEs 5/3 RNRs 0/0 REJs 0/0 SABM/Es 0/1 FRMRs 0/0 DISCs 0/0
Last input 00:00:29, output 00:00:29, output hang never
Last clearing of "show interface" counters never
Queueing strategy: fifo
Output queue 0/40, 0 drops; input queue 0/75, 0 drops
5 minute input rate 0 bits/sec, 0 packets/sec
5 minute output rate 0 bits/sec, 0 packets/sec
<Output Omitted>
        Laboratory Exercise: Visual
                Objective            Central site
                                      Cisco 3640


                                      S3/1
              X.121 address: 31101010XXX1           X.25


                                                      X.25
                                                     service


                         S0
X.121 address: 31101010XXX2          X.25


                  Cisco 1600
                 Branch office
                 Summary
•After completing this chapter, you should be
able to perform the following tasks:
• Configure an X.25 WAN connection
• Assign X.121 addresses to router interfaces and map
  higher-level addresses to X.25 addresses
• Verify X.25 configuration in the router
             Review Questions

• Explain the difference between an X.25 DTE and DCE.
• Assume you want an IP connection over an X.25 link.
  What must you do to map the network layer address to
  the X.121 address?
• How can you limit traffic by lowering the amount of
  acknowledgements sent across the X.25 link?
    Using ISDN and DDR
Technologies to Enhance Remote
         Connectivity
                Objectives
• Upon completion of this chapter, you will
  be able to complete the following tasks:
  – Select BRI or PRI service for a particular
    application
  – Identify Q.921 and Q.931 signaling and call
    sequences
  – Configure ISDN BRI
  – Configure ISDN PRI
  – Configure ISDN DDR
                       Chapter Activities
                                                Async
                                                              Central site



                                                                                  AAA server
                        BRI

                                                        PRI                  Frame Relay
                                      ISDN/analog

Windows 95 PC   Modem         Async                                           Frame Relay
                                                                                service
        Small office
                                         BRI



                                                              Frame Relay




                                      Branch office
Asynchronous Versus ISDN
                     SW   SW

           Channel             Channel
            bank                bank


  • Analog converted to digital and back


                     SW   SW




           • Digital end-to-end
 ISDN Services and Channelized
          E1 and T1
 2B

  D
      {
             BRI
                            56/64 kbps
                            56/64 kbps
                            16 kbps      }   144 kbps




                                                              }
             23B (T1) or                                64 kbps     T1 1.544 Mbps
              30B (E1)                                  each
                                      PRI                                 or
                    D                                   64 kbps     E1 2.048 Mbps
                                                                    (includes sync)


31 64 kbps
 channels
                 E1
                                  }   2.048 Mbps
                                      (includes sync)


                             24
                           DS0s               T1
                                                            }     1.544 Mbps
                                                                  (includes sync)
            BRI Call Processing

            1                      ISDN         3
                             service provider
Q.931 signaling                                 Q.931 signaling
                                       4



                                2    SS7




                B channel
                D channel/SS7 signaling
    BRI Functional Groups and
        Reference Points
                   S               T                U

        TE1              NT2              NT1             LE

   ISDN terminal       Customer        Local loop       ISDN local
     equipment          premises       terminator        exchange
                       switching
                       equipment
        R

  TE2       TA                                          U.S. demarcation

Non-ISDN Terminal                      Non-U.S. demarcations
 terminal adapter
equipment
   Physical Representation of BRI
  To non-ISDN
              Reference Points
  device (TE2)                                              To ISDN
                                                            service

          R                 S/T              U
                  TA                 NT1
                           4-wire          2-wire
                           circuit         circuit   Wall
        S/T bus                                      jack

 ISDN                  S/T bus
phone                                 S/T interface as a
              Cisco ISDN
                                     multipoint connection
                router
PRI—Layer 1 Standards and
    Reference Points

      S/T              U
              CSU/
TE                            LE
              DSU
     ITU-T           ITU-T
      I.430           I.431
                      ANSI
                     T1.601
          ISDN Protocol Layers
             D Channel           B Channel

Layer 3     DSS1 (Q.931)           IP/IPX

                              HDLC/PPP/FR/
Layer 2     LAPD (Q.921)
                                 LAPB

Layer 1         I.430/I.431/ANSI T1.601
  BRI Layer 1—I.430 Framing
 NT         TE Frame
1 1    8    1 1 1 1 1   8    1 1 1   8    1 1 1   8    1 1 1




F L    B1   L D L F L   B2   L D L   B1   L D L   B2   L D L


  TE        NT Frame
1 1    8    1 1 1 1 1   8    1 1 1   8    1 1 1   8    1 1 1




F L    B1   E D A F F   B2   E D S   B1   E D S   B2   E D S
               ISDN Layer 2
    TEI/SAPI       Daisy-chain
                   S/T bus
                                      ISDN
    TEI/SAPI                     LE
                   NT1




– ITU-T Q.920 and Q.921
– Defines logical link between TE/TA and NT2/LE
– Carries Layer 3 D-channel messages
ISDN Layer 3—D Channel Q.931

                  Q.931
TE        NT1                  LT       ET

                               ISDN switch (LE)


• Q.931 defines call control between the TE
  and local switch
            Q.931 Messaging—Call Setup
       Calling       Example          Called
       party                                                                  party
           Setup
Time




                           Setup
                    acknowledge
                             Call
                      proceeding                        Setup
                                         ISDN
                                        service                 Call proceeding
                                        provider                       Alerting
                         Alerting
                                                                      Connect
                         Connect
           Connect
           acknowledge                                  Connect
                                                        acknowledge

                                ISDN                ISDN
                               switch              switch
       Q.931 Messaging—Call Teardown
                  Example
Calling party                                                              Called party
                                                              Disconnect
                Disconnect
Time




                                                               Release


                Released                ISDN
                                       service                Released
                                       provider

                                                           Release complete

           Release complete



                               ISDN                ISDN
                              switch              switch
                     DDR Operation
                                  No
Incoming packet     Interesting
                         ?

                           Yes                                      No
                                                        Connected
                                                            ?
              Yes                 No
                    Connected
                        ?                          No        Yes
                                       Interface
                                          up?
         Reset
          Idle                     Yes
         Timer
                                                   No
                                       Phone #
                                          ?
                                  Yes
                                        Dial

                      Send
          Using DDR with ISDN
1.
          BRI or
                            ISDN
           PRI                                4.   Remote
     2.                    service                  router
           3.              provider



1. Packet arrives
2. Switch packet to DDR interface,
   determine if interesting
3. If interesting, dial DDR destination via ISDN
4. Connect to remote router
ISDN Configuration Tasks

                  ISDN



– Global configuration
   –Select switch type
   –Specify traffic to trigger DDR call
– Interface configuration
   –Select interface specifications
   –Configure ISDN addressing
– Optional feature configuration
ISDN Configuration Commands
 – Set global parameters with this command:
    • isdn switch-type
 – Set interface parameters with these commands:
    • encapsulation ppp (CHAP and Multilink PPP)
    • ip address
    • isdn spid1
Selecting the ISDN Switch Type
 Router(config)#isdn switch-type switch-type


Router(config-if)#isdn switch-type switch-type



– Specifies the type of ISDN switch with which the
  router communicates
– Global or interface command
      Setting Interface Protocols
 Router(config-if)#encapsulation {ppp | hdlc}

• Selects framing for that ISDN BRI


 Router(config-if)#ppp authentication
                          {pap | chap | ms-chap}

• Selects PPP authentication type
     Setting SPIDs if Necessary
 Router(config-if)#isdn spid1 spid-number [ldn]

• Sets a B channel SPID required by many
  service providers


Router(config-if)#isdn spid2 spid-number [ldn]

• Sets an SPID for the second B channel
             DDR Configuration Tasks
Interesting traffic
                          Dial destination
arrives
                 BRI or
                              ISDN
                 PRI         service
                                                Remote
                             provider
                                                 router



           1. Define interesting traffic
           2. Assign interesting traffic definition
              to ISDN interface
           3. Define destination
           4. Define call parameters
     Defining Interesting Traffic
 Router(config)#dialer-list dialer-group-number
   protocol protocol-name {permit | deny}
   list access-list-number

• Defines interesting packets for DDR
• Associated with the dialer group assigned to the interface

 Router(config-if)#dialer-group group-number

• Assigns an interface to the dialer access group
  specified in the dialer-list command
       Using Access Lists for DDR
 Router(config)#access-list access-list-number {permit|deny}
   {protocol | protocol-keyword }
   {source source-wildcard | any}
   {destination destination-wildcard | any}
   [protocol-specific-options] [log]


• Gives tighter control over “interesting” traffic and
  uses standard or extended access lists


 Router(config)#dialer-list dialer-group list access-list-
   number

• Associates an access list with a dialer access group
   Defining Destination Parameters


Router(config-if)#dialer map protocol next-hop-address
   [name hostname] [broadcast] dial-string



• Defines how to reach a remote ISDN destination
Setting Default/Static Routes
                         TCP/IP
Static route is toward
the remote site




 Default route is
 toward cloud
            Setting Static Routes
Router(config)#ip route 172.108.0.0 255.255.0.0 192.254.35.2




              BRI 0
                                                      172.108.0.0

                                       192.254.35.2
            Setting Default Routes
Router(config)#ip route 172.254.50.0 255.255.255.0 172.254.45.1

Router(config)#ip default-network 172.254.50.0

Router(config)#ip route 0.0.0.0 0.0.0.0 172.254.45.1




                        172.254.45.2   172.254.45.1
                                                      172.254.50.0


         172.254.30.0
     Setting Route Redistribution
                                                 172.108.0.0




                                                   10.0.0.1

Router(config)#router igrp 109
Router(config-router)#network 172.108.0.0
Router(config-router)#redistribute static
Router(config)#ip route 192.150.42.0               10.0.0.2
       255.255.255.0 10.0.0.2


• This router advertises static
  routes to other routers                   192.150.42.0
  Deactivating Routing Updates on
            an Interface

Router(config)#router igrp 100
Router(config-router)#passive-interface bri0

                                               BRI 0




  • Does not broadcast routes on
    that interface
    Configuring a Simple ISDN Call
              10.170.0.1
                                                            10.170.0.2
    Cisco-a              NT1
                                                   NT1        Cisco-b
                                    ISDN
    E0       BRI 0
                       5105551234                         BRI 0
                                      4085554000                  E0

         192.168.2.1                                     192.168.1.1


–   Use PPP encapsulation
–   All IP traffic to destination triggers ISDN call
–   Carrier uses a 5ESS basic rate switch
–   Service provider assigns connection parameters
Configuration Example, Cisco-a
            10.170.0.1                  4085554000
              BRI 0                      10.170.0.2
                            ISDN
        Cisco-a
                                               Cisco-b
                                                         192.168.1.1

hostname Cisco-a
isdn switch-type basic-5ess
username Cisco-b password samepass
interface bri 0
  ip address 10.170.0.1 255.255.0.0
  encapsulation ppp
  dialer idle-timeout 300
  dialer map ip 10.170.0.2 name Cisco-b 4085554000
  dialer-group 1
  ppp authentication chap
!
ip route 192.168.1.0 255.255.255.0 10.170.0.2
dialer-list 1 protocol ip permit
    Configuration Example, Cisco-b
                 5105551234
                  10.170.0.1              10.170.0.2
                                             BRI 0
                               ISDN
              Cisco-a
                                                Cisco-b
192.168.2.1

  hostname Cisco-b
  isdn switch-type basic-5ess
  username Cisco-a password samepass
  interface bri 0
    ip address 10.170.0.2 255.255.0.0
    encapsulation ppp
    dialer idle-timeout 300
    dialer map ip 10.170.0.1 name Cisco-a 5105551234
    dialer-group 1
    ppp authentication chap
  !
  ip route 192.168.2.0 255.255.255.0 10.170.0.1
  dialer-list 1 protocol ip permit
   Access Lists and DDR for ISDN              10.170.0.2
                           4085554000
      10.170.0.1
                                                        192.168.1.1
                        ISDN            NT1   Cisco-b
                       Service                10.170.0.3
      BRI 0
              NT1     Provider
Cisco-a

                           4085551234                   192.168.3.1
                                        NT1
                                              Cisco-c



   – Cisco-a allows all IP traffic except Telnet and FTP to
     trigger ISDN calls to Cisco-b, and access subnet
     192.168.1.0
      Access List Configuration
         Example, Cisco-a            4085554000
                                      10.170.0.2 Cisco-b
            10.170.0.1
  Cisco-a                                                  192.168.1.1
                           ISDN
            BRI 0         Service    4085551234
                          Provider    10.170.0.3 Cisco-c
                                                           192.168.3.1


hostname Cisco-a
isdn switch-type basic-dms100
username Cisco-b password samepass
username Cisco-c password samepass
interface bri 0
 ip address 10.170.0.1 255.255.0.0
 encapsulation ppp
dialer idle-timeout 300
dialer map ip 10.170.0.2 name Cisco-b 4085554000
dialer map ip 10.170.0.3 name Cisco-c 4085551234
dialer-group 2
ppp authentication chap
(continued on next figure)
    Access List Configuration
    Example, Cisco-a (cont.)       4085554000
                                    10.170.0.2 Cisco-b
          10.170.0.1
Cisco-a                                                  192.168.1.1
                         ISDN
          BRI 0         Service    4085551234
                        Provider    10.170.0.3 Cisco-c
                                                         192.168.3.1


 ip route 192.168.1.0 255.255.255.0 10.170.0.2
 ip route 192.168.3.0 255.255.255.0 10.170.0.3
 access-list 101 deny tcp any any eq ftp
 access-list 101 deny tcp any any eq telnet
 access-list 101 permit ip any any
 dialer-list 2 protocol ip list 101
Optional ISDN Configurations
                        ISDN
                  service provider




–   Specify Multilink PPP or BOD
–   Enable caller ID screening
–   Configure rate adaptation
–   Called number answer
          B Channel Aggregation
64 kbps     B1
                     With BOD
                     or MP
                                     Speed
                                     Limit
                                      128
64 kbps     B2
                                     kbps

– Available on all Cisco IOS platforms with ISDN
– Accomplished via Cisco proprietary BOD or
  Multilink PPP
            Cisco Proprietary BOD
                        B1

  Traffic              Buffer      ISDN
              Router
                        B2




Router(config)#int bri0
Router(config-if)#dialer load—threshold load
       B Channel Aggregation Using
             Multilink PPP
     Data in                                                  Data out
                 B1    A1           ISDN           B1    A1
B      A                                                            B    A
                              service provider
                B2    A2                          B2    A2


           Sequencing and                          Sequencing and
            fragmentation                            reassembly


Router(config)#int bri0
Router(config-if)#dialer load-threshold load [inbound | outbound | either]
Router(config-if)#ppp multilink
 Configuring Multilink PPP
– MLP can be configured on:
  •   Asynchronous serial interfaces
  •   Synchronous serial interfaces
  •   Basic Rate Interfaces (BRI)
  •   Primary Rate Interfaces (PRI)
Configuring Multilink PPP (cont.)
                  Rotary group




                                      ISDN


 Router(config-if)#ppp multilink

• Enables Multilink PPP on a dialer rotary group

 Router(config-if)#dialer load-threshold load
            [outbound | inbound | either]

• Defines the threshold to bring up another link
Configuring Multilink PPP (cont.)

                                   ISDN


Router(config)#interface bri0
Router(config-if)#no ip address
Router(config-if)#encapsulation ppp
Router(config-if)#ppp multilink
Router(config-if)#dialer idle-timeout 30
Router(config-if)#dialer load-threshold 128 either
 Configuring Multilink PPP (cont.)
                         Rotary group




                                                ISDN

Router(config)#interface dialer1
Router(config-if)#ip address 10.10.10.7 255.255.255.0
Router(config-if)#encapsulation ppp
Router(config-if)#dialer idle-timeout 30
Router(config-if)#dialer map ip 10.10.10.8 name Router 81012345678901
Router(config-if)#dialer load-threshold 128 either
Router(config-if)#dialer-group 1
Router(config-if)#ppp authentication chap
Router(config-if)#ppp multilink
    Caller Identification Screening
                                                Compare with
                        Call setup message     allowed numbers
                          with local ISDN                ISDN
                                               Router
                              numbers                   number
                                   5551234       A     5551234


                    ISDN
Router A                                        Router B
                                 Accept call




  – Extra level of call management
  – Call not set up (or charged) until acceptance
  – An alternative: PPP encapsulation and CHAP
   Configuring Caller ID Screening


 Router(config-if)#isdn caller number
• Enables caller ID screening
Selecting ISDN Rate Adaptation

                             64 kbps
    BRI 0   64 kbps
                      ISDN         BRI 0
                                   BRI 1
            56 kbps
                                56 kbps




– Configured for outgoing calls
– Requested lower speed from call is honored
– Assigned on a per-destination basis
      Configuring Rate Adaptation


 Router(config-if)#dialer map protocol next-hop-address
   [name name] [speed speed] [broadcast] [dial-string]

• Negotiates speed for calls to a destination
     Configuring Called-Number
              Answer
Router(config-if)#isdn answer1 [called-party-number]

                        or
Router(config-if)#isdn answer2 [called-party-number]


• Sets the number to allow the interface to
  respond/answer
      Monitoring PPP on BRI
BranchF#sh int bri 0 1
BRI0:1 is up, line protocol is up
  Hardware is BRI
  MTU 1500 bytes, BW 64 Kbit, DLY 20000 usec, rely 255/255, load 1/255
  Encapsulation PPP, loopback not set, keepalive set (10 sec)
  LCP Open
  Open: IPCP, CDPCP
  Last input 00:00:02, output 00:00:02, output hang never
  Last clearing of "show interface" counters never
  Input queue: 0/75/0 (size/max/drops); Total output drops: 0
  Queueing strategy: weighted fair
  Output queue: 0/1000/64/0 (size/max total/threshold/drops)
     Conversations 0/1/256 (active/max active/max total)
     Reserved Conversations 0/0 (allocated/max allocated)
  5 minute input rate 0 bits/sec, 0 packets/sec
  5 minute output rate 0 bits/sec, 0 packets/sec
     45 packets input, 1448 bytes, 0 no buffer
     Received 45 broadcasts, 0 runts, 0 giants, 0 throttles
     0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort
     45 packets output, 1444 bytes, 0 underruns
     0 output errors, 0 collisions, 0 interface resets
     0 output buffer failures, 0 output buffers swapped out
     3 carrier transitions
Monitoring ISDN BRI D Channel
•BranchF#sh int bri 0
•BRI0 is up, line protocol is up (spoofing)
• Hardware is BRI
• Internet address is 10.155.0.1/24
• MTU 1500 bytes, BW 64 Kbit, DLY 20000 usec, rely 255/255, load
1/255
• Encapsulation PPP, loopback not set
• Last input 00:00:04, output never, output hang never
• Last clearing of "show interface" counters never
• Input queue: 0/75/0 (size/max/drops); Total output drops: 0
• Queueing strategy: weighted fair
• Output queue: 0/1000/64/0 (size/max total/threshold/drops)
•     Conversations 0/1/256 (active/max active/max total)
•     Reserved Conversations 0/0 (allocated/max allocated)
• 5 minute input rate 0 bits/sec, 0 packets/sec
• 5 minute output rate 0 bits/sec, 0 packets/sec
•     680 packets input, 3651 bytes, 0 no buffer
•     Received 223 broadcasts, 0 runts, 0 giants, 0 throttles
•     0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort
•     680 packets output, 3697 bytes, 0 underruns
•     0 output errors, 0 collisions, 5 interface resets
•     0 output buffer failures, 0 output buffers swapped out
•     3 carrier transitions
Monitoring ISDN BRI B Channels
BranchF#sh int bri 0 1 2
BRI0:1 is up, line protocol is up
  Hardware is BRI
  MTU 1500 bytes, BW 64 Kbit, DLY 20000 usec, rely 255/255, load 1/255
  Encapsulation PPP, loopback not set, keepalive set (10 sec)
  LCP Open
  Open: IPCP, CDPCP
  Last input 00:00:01, output 00:00:01, output hang never
  Last clearing of "show interface" counters never
  Input queue: 0/75/0 (size/max/drops); Total output drops: 0
  Queueing strategy: weighted fair
  Output queue: 0/1000/64/0 (size/max total/threshold/drops)
      Conversations 0/1/256 (active/max active/max total)
      Reserved Conversations 0/0 (allocated/max allocated)
  5 minute input rate 0 bits/sec, 0 packets/sec
  5 minute output rate 0 bits/sec, 0 packets/sec
      82 packets input, 2844 bytes, 0 no buffer
      Received 82 broadcasts, 0 runts, 0 giants, 0 throttles
      0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort
      82 packets output, 2838 bytes, 0 underruns
      0 output errors, 0 collisions, 0 interface resets
      0 output buffer failures, 0 output buffers swapped out
      5 carrier transitions
(output omitted)
        Monitoring ISDN BRI
Router#show isdn status
The current ISDN Switchtype = basic-5ess
ISDN BRI0 interface
    Layer 1 Status:
        ACTIVE
    Layer 2 Status:
        TEI = 65, State = MULTIPLE_FRAME_ESTABLISHED
    Layer 3 Status:
        1 Active Layer 3 Call(s)
    Activated dsl 0 CCBs = 1
        CCB:callid=2, sapi=0, ces=1, B-chan=1
    Total Allocated ISDN CCBs = 1
            Verifying Multilink PPP
Router#show ppp multilink
Bundle rudder, 3 members, first link is BRI0: B-Channel 1
0 lost fragments, 8 reordered, 0 unassigned, sequence 0x1E/0x1E rcvd/sent
Bundle dallas, 4 members, first link is BRI2: B-Channel 1
0 lost fragments, 28 reordered, 0 unassigned, sequence 0x12E/0x12E rcvd/sent
Verifying Multilink PPP (cont.)
Router# show interface bri0 1
BRI0: B-Channel 1 is up, line protocol is up
  Hardware is BRI
  MTU 1500 bytes, BW 64 Kbit, DLY 20000 usec, rely 255/255, load 1/255
  Encapsulation PPP, loopback not set, keepalive not set
  lcp        = OPEN      multilink = OPEN
  ipcp       = OPEN
  Last input 0:05:51, output 0:05:52, output hang never
  Last clearing of "show interface" counters never
  Input queue: 0/75/0 (size/max/drops); Total output drops: 0
  Output queue: 0/64/0 (size/threshold/drops)
      Conversations 0/1 (active/max active)
      Reserved Conversations 0/0 (allocated/max allocated)
  5 minute input rate 0 bits/sec, 0 packets/sec
  5 minute output rate 0 bits/sec, 0 packets/sec
      15 packets input, 804 bytes, 0 no buffer
      Received 0 broadcasts, 0 runts, 0 giants
      0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort
      14 packets output, 806 bytes, 0 underruns
      0 output errors, 0 collisions, 19 interface resets, 0 restarts
      0 output buffer failures, 0 output buffers swapped out
      1 carrier transitions
      Troubleshooting Multilink PPP
BranchF#debug dialer
BranchF#ping 10.115.0.135

Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 10.115.0.135, timeout is 2 seconds:

BRI0: Dialing cause ip (s=10.155.0.1, d=10.115.0.135)
BRI0: Attempting to dial 6000
%LINK-3-UPDOWN: Interface BRI0:2, changed state to up
dialer Protocol up for BR0:2.
%LINEPROTO-5-UPDOWN: Line protocol on Interface BRI0:2, changed state to
up!!!!
Success rate is 80 percent (4/5), round-trip min/avg/max = 32/34/36 ms
BranchF#
BRI0: rotary group to 6000 overloaded (1)
BRI0: Attempting to dial 6000
%ISDN-6-CONNECT: Interface BRI0:2 is now connected to 6000 CentralF
 Troubleshooting Multilink PPP
            (cont.)



                      Bundle


• CHAP/PAP/caller ID on answering router?
• Dialer load threshold on one router?
• Fair queuing turned on?
      ISDN debug Commands
Router#debug isdn q921

 – Shows data link layer messages (Layer 2) on the D
   channel between the access router and the ISDN
   switch

Router#debug isdn q931

• Shows call setup and teardown of ISDN
  network connections (Layer 3) between the
  access router and the ISDN switch
  Configuration Tasks for PRI
                                              23B (T1) or
   T1/E1                          PRI         30B (E1)

                                               D




– Select the PRI switch type
– Specify T1/E1 controller, framing, and line coding for
  the facility
– Set PRI group timeslots for T1/E1 and indicate the
  speed used
– Specify the interface on the router that
  you will configure for DDR
      ISDN PRI Configuration


Router(config)#isdn switch-type switch-type

• Configures the ISDN PRI switch type

Router(config)#controller {t1 | e1}
          {slot/port | unit-number}

• Configures the ISDN PRI controller
  T1/E1 Controller Parameters
Router(config-controller)#framing
 {sf | esf | crc4 | no-crc4}
• Selects the framing type on the controller
 Router(config-controller)#linecode
  {ami | b8zs | hdb3}

• Selects the line-code type on the controller
 Router(config-controller)#clock source
   {line [primary | secondary] | internal}

• Specifies the T1 clock source
          Additional ISDN PRI
         Configuration Parameters
 Router(config-controller)#pri-group [timeslots range]

• Specifies ISDN PRI on the T1 or E1 controller

 Router(config)#interface serial {slot/port: | unit:}{23 | 15}

• Specifies the serial port for the PRI D channel

 Router(config-if)#isdn incoming-voice modem

• Switches incoming analog calls to internal modems
  PRI Configuration Example
   Cisco 3600

                             5ESS   ISDN
                  T1 PRI


isdn switch-type primary-5ess
!
controller t1 0/0
pri-group timeslots 1-24
framing esf
linecode b8zs
clock source line
!
interface serial 0/0:23
ip address 192.168.11.2 255.255.255.0
isdn incoming-voice modem
Laboratory Exercise: Visual
        Objective
                                    Central site
            ISDN
                            PRI



         BRI           ISDN, PPP,
                       CHAP, DDR




       Branch office
                   Summary
• After completing this chapter, you should be able
  to perform the following tasks:
   – Select BRI or PRI service for a particular
     application
   – Identify Q.921 and Q.931 signaling and call
     sequences
   – Configure ISDN BRI
   – Configure ISDN PRI
   – Configure ISDN DDR
        Review Questions
– Compare ISDN BRI with ISDN PRI.
– If you are not sure what your ISDN switch
  type is, where would you obtain this
  information?
– What are Q.921 and Q.931?
    Establishing a
  Dedicated Frame
Relay Connection and
 Controlling Traffic
        Flow
                  Objectives
• Upon completion of this chapter, you will be able to
  perform the following tasks:
   – Configure Frame Relay
   – Configure Frame Relay subinterfaces
   – Configure Frame Relay traffic shaping
   – Verify Frame Relay operation
                  Chapter Activities
                                                Async         Central site




                                                                                  AAA server
                        BRI

                                                        PRI                  Frame Relay
                                      ISDN/analog

Windows 95 PC   Modem         Async                                           Frame Relay
                                                                                service
        Small office
                                         BRI



                                                              Frame Relay




                                      Branch office




                                                                                               261
          Frame Relay Overview
                                    DCE or Frame
                                    Relay switches


DTE or             CSU/DSU
  CPE
routers



          Token   Frame Relay
           Ring    works here


      – Virtual circuits make connections
      – Connection-oriented service
       Frame Relay Operation
                                                             10.1.1.1
                                     PVC
              CSU/DSU
                         DLCI=500




                                                Inverse ARP or
                ARP                            Frame Relay map


ETH Destination Source   IP         Frame Destination       IP
       MAC       MAC                Relay DLCI (500)    (10.1.1.1)


– Get locally significant DLCIs from your Frame Relay
  provider
– Map your network addresses to DLCIs
Frame Relay Signaling
LMI
500=Active                PVC
400=Inactive   DLCI=500

 CSU/DSU
  DLCI=400
                 PVC


   Keepalive


 •Cisco supports three LMI standards:
   – ANSI T1.617 Annex D
   – ITU-T Q.933 Annex A
   – “The gang of four”
Configuring Basic Frame Relay

 Central                                                Branch




Central(config)#interface Serial1
Central(config-if)#ip address 10.16.0.1 255.255.255.0
Central(config-if)#encapsulation frame-relay
           Configuring Address Mapping
                   Central site
                                                            VC        Branch
               Central                                                Branch
                                  VC                                  10.16.0.2/24


DLCI to Branch=110
DLCI to Non-Cisco=120                                                 Non-Cisco
10.16.0.1/24                                                          10.16.0.3/24

 Central(config)#interface Serial1
 Central(config-if)#ip address 10.16.0.1 255.255.255.0
 Central(config-if)#encapsulation frame-relay
 Central(config-if)#bandwidth 56
 Central(config-if)#frame-relay map ip 10.16.0.2 110 broadcast
 Central(config-if)#frame-relay map ip 10.16.0.3 120 broadcast ietf
          Verifying Frame Relay Operation
Router#show interface serial 0
Serial0 is up, line protocol is up
Hardware is CD2430 in sync mode
MTU 1500 bytes, BW 128 Kbit, DLY 20000 usec, rely 255/255, load 1/255
Encapsulation FRAME-RELAY, loopback not set, keepalive set (10 sec)
LMI enq sent 112971, LMI stat recvd 112971, LMI upd recvd 0, DTE LMI up
LMI enq recvd 0, LMI stat sent 0, LMI upd sent 0
LMI DLCI 1023 LMI type is CISCO frame relay DTE
FR SVC disabled, LAPF state down
Broadcast queue 0/64, broadcasts sent/dropped 32776/0, interface broadcasts 14
Last input 00:00:00, output 00:00:03, output hang never
Last clearing of "show interface" counters never
Input queue: 0/75/0 (size/max/drops); Total output drops: 0
Queueing strategy: weighted fair
<Output Omitted>



    – Displays line, protocol, DLCI, and LMI information
         Verifying Frame Relay Operation
                      (cont.)
Router#show frame-relay pvc 110

PVC Statistics for interface Serial0 (Frame Relay DTE)

DLCI = 110, DLCI USAGE = LOCAL, PVC STATUS = ACTIVE, INTERFACE = Serial0

input pkts 14055 output pkts 32795 in bytes 1096228
out bytes 6216155 dropped pkts 0 in FECN pkts 0
in BECN pkts 0 out FECN pkts 0 out BECN pkts 0
in DE pkts 0 out DE pkts 0
out bcast pkts 32795 out bcast bytes 6216155

<Output Omitted>




    – Displays PVC traffic statistics
        Verifying Frame Relay Operation
                     (cont.)
Router#show frame-relay map
Serial0 (up): ip 10.140.2.1 dlci 120(0x78,0x1C80), dynamic,
         broadcast,, status defined, active




  – Displays the route maps, either static or dynamic
         Verifying Frame Relay Operation
                      (cont.)
Router#show frame-relay lmi

LMI Statistics for interface Serial0 (Frame Relay DTE) LMI TYPE = CISCO
Invalid Unnumbered info 0 Invalid Prot Disc 0
Invalid dummy Call Ref 0 Invalid Msg Type 0
Invalid Status Message 0 Invalid Lock Shift 0
Invalid Information ID 0 Invalid Report IE Len 0
Invalid Report Request 0 Invalid Keep IE Len 0
Num Status Enq. Sent 113100 Num Status msgs Rcvd 113100
Num Update Status Rcvd 0 Num Status Timeouts 0



    – Displays LMI information
Verifying Frame Relay Operation
             (cont.)
Router#debug frame-relay lmi
Serial3/1(in): Status, myseq 214
RT IE 1, length 1, type 0
KA IE 3, length 2, yourseq 214, myseq 214
PVC IE 0x7 , length 0x6 , dlci 130, status 0x2 , bw 0
Serial3/1(out): StEnq, myseq 215, yourseen 214, DTE up
datagramstart = 0x1959DF4, datagramsize = 13
FR encap = 0xFCF10309
00 75 01 01 01 03 02 D7 D6

Serial3/1(in): Status, myseq 215
RT IE 1, length 1, type 1
KA IE 3, length 2, yourseq 215, myseq 215
Serial3/1(out): StEnq, myseq 216, yourseen 215, DTE up
datagramstart = 0x1959DF4, datagramsize = 13
FR encap = 0xFCF10309
00 75 01 01 01 03 02 D8 D7


 – Displays LMI debug information
      Verifying Frame Relay Operation
                   (cont.)

Router#sh frame map
Serial0 (up): ip 10.140.2.1 dlci 120(0x78,0x1C80), dynamic,
         broadcast,, status defined, active
Router#clear frame-relay-inarp
Router#sh frame map
Router#

   – Clears dynamically created Frame Relay maps
Selecting a Frame Relay Topology
                           Full mesh




Partial mesh




                  Star (hub and spoke)
Reachability Issues with Routing
            Updates
                      Circuit #21
      Routing     1                               B
      update                                  B
                      Circuit #22
        A         2
                                              CC


                      Circuit #23
                  3
                                              D
                                              D




 – Broadcast traffic must be replicated for
   each active connection
 Resolving Reachability Issues
                          Physical    Subnet A
 Logical interface        interface
 S0.1                S0               Subnet B
 S0.2
 S0.3
                                      Subnet C

– Split horizon can cause problems in NBMA
  environments
– A single physical interface simulates multiple
  logical interfaces
– Subinterfaces can resolve split horizon issues
     Configuring Subinterfaces
–Multipoint
  – Subinterfaces act as default NBMA network
  – Can save subnets because uses single subnet
  – Good for full-mesh topology
–Point-to-point
  – Subinterfaces act as leased line
  – Each point-to-point connection requires its own subnet
  – Good for star or partial-mesh topologies
        Configuring Subinterfaces Example
                                                       10.17.0.1                      10.17.0.2
                                          Central                                     S0
                                                       S0.2-DLCI=110

                                                                                       110
                                                 10.18.0.1                            Branch
                                                 S0.3-DLCI=120
                                                 S0.3-DLCI=130                        10.18.0.2
                                                                                      S0
Central(config)#<Output Omitted>
Central(config-if)#interface Serial0                                                   120
Central(config-if)#no ip address                                                      Branch
Central(config-if)#encapsulation frame-relay
!                                                                         10.18.0.3
Central(config)#interface Serial0.2 point-to-point                        S0
Central(config-subif)#ip address 10.17.0.1 255.255.255.0
Central(config-subif)#frame-relay interface-dlci 110                    130
!                                                                      Branch
Central(config)#interface Serial0.3 multipoint
Central(config-subif)#ip address 10.18.0.1 255.255.255.0
Central(config-subif)#frame-relay interface-dlci 120
Central(config-subif)#frame-relay interface-dlci 130
!
<Output Omitted>
         Frame Relay Traffic Shaping
                 Overview
                     Frame Relay cloud

                                         T1
           56 kbps



Branch office                                 Central site
Frame Relay Traffic Flow
     Terminology
   Local
   access
   loop=T1           I am congested.
     BECN                              Local
                                       access
                                       loop=64 kbps




             Traffic flow




                    Bc=64 kbps
     CIR=32 kbps
                      T1
            Frame Relay Traffic Flow
               Terminology (cont.)
                               Discard
       Bc + B e                                         Discard frame

                                                      DE=1
Bits




            Bc


                                                       DE=0



                  Frame 1      Frame 2   Frame 3   Frame 4
                            Time (T=Bc/CIR)
 Why Use Traffic Shaping over
       Frame Relay?
                         Frame Relay
                            cloud
          56 kbps                               T1



Branch      Bottleneck                                     Central
 office                                                     site

                                        I need to reduce
                                       the pace at which
                                         I send packets.
  Why use Traffic Shaping over
     Frame Relay? (cont.)
                    Frame Relay cloud



          56 kbps                       T1


Branch                                       Central
 office                                       site
 Configuring Frame Relay Traffic
    Shaping—Steps 1 and 2

Router(config)#map-class frame-relay map-class-name


– Enters map class configuration mode so you can define
  a map class
Configuring Frame Relay Traffic
   Shaping—Step 2 (cont.)
Router(config-map-class)#frame-relay traffic-rate average [peak]


  – Defines the average and peak rates

      or

Router(config-map-class)#frame-relay adaptive-shaping becn


     – Specifies that the router fluctuates the sending rate
       based on the BECNs received
  Configuring Frame Relay Traffic
   or
      Shaping—Step 2 (cont.)
Router(config-map-class)#frame-relay custom-queue-list number


     – Specifies a custom queue list

        or

Router(config-map-class)#frame-relay priority-group number


     – Specifies a priority group
 Configuring Frame Relay Traffic
Step 3Shaping—Steps 3 to 5
 Router(config-if)#encapsulation frame-relay

   – Enables Frame Relay on an interface
Step 4
 Router(config-if)#frame-relay traffic-shaping


   – Enables Frame Relay traffic shaping on an interface

Step 5
 Router(config-if)#frame-relay class map-class-name


   – Maps the map class to virtual circuits on the interface
                 Traffic Shaping Rate
                Enforcement Example
                           Frame Relay cloud
Branch office
                9.6 kbps
                                                    T1
        Egress point

                                                            Central site
                9.6 kbps
Branch office
                                        I need to send
                                       packets at the CIR
                                          for each VC.
    Configuring Traffic Shaping
    Rate Enforcement Example   Frame Relay cloud
  Branch office

                                                          T1

                                                                Central site
  Branch office
Central(config)#interface Serial2
Central(config-if)#no ip address
Central(config-if)#encapsulation frame-relay
Central(config-if)#frame-relay traffic-shaping
Central(config-if)#frame-relay class branch
!
…
!
Central(config)#map-class frame-relay branch
Central(config-map-class)#frame-relay traffic-rate 9600 18000
 Traffic Shaping BECN Support
            Example
                    Frame Relay cloud



          56 kbps                               T1


Branch                                                        Central
 office                                                        site


                                        I need to adjust my
                                           transmit speed
                                        because of BECNs.
         Configuring Traffic Shaping
          BECN Support Example
                                   Frame Relay cloud



                56 kbps                                       T1


    Branch                                                         Central
     office                                                         site


Central(config)#interface serial 0
Central(config-if)#no ip address
Central(config-if)#encapsulation frame-relay
Central(config-if)#frame-relay traffic-shaping
Central(config-if)#frame-relay class becnnotify
!
…
!
Central(config)#map-class frame-relay becnnotify
Central(config-map-class)#frame-relay adaptive-shaping becn
               Configuring Traffic Shaping
                   Queuing Example
interface Serial0                          !
 no ip address                             map-class frame-relay slow_vcs
 encapsulation frame-relay                  frame-relay traffic-rate 4800 9600
 frame-relay lmi-type ansi                  frame-relay custom-queue-list 1
 frame-relay traffic-shaping               !
 frame-relay class slow_vcs                map-class frame-relay fast_vcs
!                                           frame-relay traffic-rate 16000 64000
interface Serial0.1 point-to-point          frame-relay priority-group 2
 ip address 10.128.30.1 255.255.255.248    !
 ip ospf cost 200                          access-list 100 permit tcp any any eq 2065
 bandwidth 10                              access-list 115 permit tcp any any eq 256
 frame-relay interface-dlci 101            !
!                                          priority-list 2 protocol decnet high
interface Serial0.2 point-to-point         priority-list 2 protocol ip normal
 ip address 10.128.30.9 255.255.255.248    priority-list 2 default medium
 ip ospf cost 400                          !
 bandwidth 10                              queue-list 1 protocol ip 1 list 100
 frame-relay interface-dlci 102            queue-list 1 protocol ip 2 list 115
 class fast_vcs                            queue-list 1 default 3
!                                          queue-list 1 queue 1 byte-count 1600 limit 200
 interface Serial0.3 point-to-point        queue-list 1 queue 2 byte-count 600 limit 200
 ip address 10.128.30.17 255.255.255.248   queue-list 1 queue 3 byte-count 500 limit 200
 ip ospf cost 200
 bandwidth 10
 frame-relay interface-dlci 103
           Verifying Frame Relay Traffic
                      Shaping
CentralA#sh frame-relay pvc

PVC Statistics for interface Serial3/1 (Frame Relay DTE)

DLCI = 110, DLCI USAGE = LOCAL, PVC STATUS = ACTIVE, INTERFACE = Serial3/1.1

 input pkts 35       output pkts 40         in bytes 4324
 out bytes 6684       dropped pkts 0         in FECN pkts 0
 in BECN pkts 0        out FECN pkts 0          out BECN pkts 0
 in DE pkts 0        out DE pkts 0
 out bcast pkts 25     out bcast bytes 5124
 Shaping adapts to BECN
 pvc create time 00:12:55, last time pvc status changed 00:12:55
Laboratory Exercise: Visual
        Objective
                        Central site
                         Cisco 3640


                         S3/1
                                       Frame Relay


         S0
                                       Frame Relay
                                         service
                   Frame Relay
    Cisco 1600
   Branch office
                   Summary
After completing this chapter, you should
be able to perform the following tasks:
   –   Configure Frame Relay
   –   Configure Frame Relay subinterfaces
   –   Configure Frame Relay traffic shaping
   –   Verify Frame Relay operation
           Review Questions
– What is a DLCI and how is it used to route Frame Relay
  traffic?
– Why would you use Frame Relay subinterfaces?
– List and describe three Frame Relay traffic shaping
  features.

								
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