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Lesson 6 Frame Relay and ATM

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Lesson 6 Frame Relay and ATM Powered By Docstoc
					CISC452
Telecommunications Systems

Lesson 6
Frame Relay and ATM

                             1
  Technology Comparison
                Private                              Frame
                 Line         X.25      SMDS         Relay         ATM            IP
Speed          56K - 622M     9.6K -   56K - 34M      Dial -     1.5M - 622M   Dial - 45M
                              2.048M                  45M
Traffic Type   Data/Voice/     Data      Data      Data/On Net   Data/Voice/     Data
                 Video                              Voice and      Video
                                                      Video
Connection         Yes         Yes        No           Yes          Yes           No
Oriented
Typical        Star/Multi-     Star     Any-to-    Mesh/Partial Mesh/Partial    Any-to-
Topology       point/Multi-              Any        Mesh/Star    Mesh/Star       Any
                  Drop

QoS Support        No          No         No       Proprietary      Yes           No




                                                                                            2
Benefits of Frame Relay
•   Savings over Private Lines
     Reduces number of dedicated devices which reduces
     equipment costs
     Reduces complexity for network managers

•   Greater Bandwidth Flexibility than Private
    Lines
•   Higher Reliability and Resiliency than Private
    Lines
•   Lower Cost of Ownership and Better
    Bandwidth Utilization
     Growth of Branch Office Networks

                                                         3
Benefits of Frame Relay (cont’d)
•   Consolidation of LAN, SNA, On-net Voice,
    and/or Packetized Video
     Simplifies Network Architecture
     Reduces Operations and Administrative Costs
     Improves Application Performance and
     Network Efficiency

•   Smooth migration to ATM
     Service and Network Interworking with ATM (FRF.5
     and FRF.8)




                                                        4
Frame Relay Terms And
Definitions (cont’d)
•   Committed Information Rate (CIR)
    The bandwidth defined for a VC

•   Bc = Committed Burst
    Maximum number of committed bits to be transmitted
      over time interval

•   Be = Excess Burst
    Number of Excess bits that will be transmitted over time

•   Tc Time interval
    Time measurement based how much bandwidth is
      available for data to burst on to the network


                                                               5
Frame Relay Terms And
Definitions (cont’d)

•   FECN Forward Explicit Congestion Notification
    Bit set by the network node (FR Switch) that is experiencing congestion
    Sent in the direction of the receiver (destination)

•   BECN Backward Explicit Congestion Notification
    Bit set by the network node that is experiencing congestion
    Sent in the direction of the sender (source)

•   DE Discard Eligible bit
    Set by either the DTE (access device FRAD, router etc.) or the network
       nodes (switches)
    May be set selectively by some DTE devices
    May be set by network nodes in the event the user has exceeded CIR and
      the network is experiencing congestion
                                                                              6
  Service Comparison
    Private Lines (TDM)                Frame Relay

Engineer Network for Peak     Engineer Network for Average
Traffic Needs                 Traffic Needs

CSU/DSU per Leased Line per   CSU/DSU per Leased Line that
remote site                   can access many remote sites

Time Division Multiplexing    Statistical Multiplexing and Burst
                              Capability
Resiliency is Not Inherent
                              Resiliency is Inherent in Network




                                                                   7
        Frame Relay Complements
        Other Technologies
       Application              Technology            Speeds       Technology
   LAN                        FR, SMDS, ATM       < 1.5 Mbps      FR
   LAN & SNA                  FR, ATM
   Data & On-net Voice        FR, ATM             1.5 - 45 Mbps   FR, ATM
   Data, On-net Voice         FR, ATM
   & Packetized Video                             >45 Mbps        ATM



                             FR or                 Interworking    Agreement
                             ATM
                                       HQ         FR - ATM        FRF.5 and FRF.8

                     FR or
                     ATM             Regional     FR - SMDS       SIP
                                      Sites
             Dedicated
             or Dial FR          Remote Sites
Dial Remote Access
         or
      Dial FR                  Mobile Workers &
                                Telecommuters
                                                                                    8
Understanding Public Frame
Relay Services
DS-3/E-3

DS-3/E-3
                      ATM
                                           X-25
DS-1/E-1

                                                  International
DS-0
                            Public Frame               FR
 ISDN
                               Relay
 Dial Access                                          Management
                                                        Reports

           Internet                            FR
           Access                            Access
 Dial                             IP
Access


                                                                   9
Characteristics of ATM
   Voice

   Data

   Video                    Cells



    • Uses small, fixed-sized cells
    • Connection-oriented
    • Supports multiple service types
    • Applicable to LAN and WAN

                                        10
    Creating Cells from Packets
                   Dest.        Source                             Frame
         Packet                                     Data
                  Address       Address                            Check



Cells Header          Payload


                         Header      Payload

           5 Byte                         Header   Payload
           Header
  53
 Bytes                                                Header   Payload
           48 Byte
           Payload

           ATM Cell
                                                                           11
    Campus Networking Evolution
                      Traditional Network
            Shared
   Ethernet Clients



                                                Corporate WAN
    Local                                        and Internet
Workgroup
  Servers



                             • Hierarchical design
                               with broadcast control
                             • 80/20 rule
                             • Homogenous user communities
                             • Moves, adds, and changes manually
    Campus Networking Evolution
                 Contemporary Network
Switched
Ethernet  Ethernet Switch
 Clients with VLAN Support
                                                      Corporate WAN
                                                      and Internet
                               Campus
                             ATM Network

                                                      Centralized
                                                      High-Performance
                               ATM-Attached           Servers
                                 Station(s)

              • Network hierarchy maintained
              • Traffic patterns migrating
              • Client and server performance increases
              • Moves, adds, and changes automated
                                                                      13
Rudimentary ATM Concepts


      • Physical layer
      • Signaling
      • Cell format
      • Connection types



                           14
ATM Transmission Media
   ATM SDH/SONET Rates Chart
         SDH           SONET      Rate—Mbps
                    STS-1/OC-1       51.84
        STM-1       STS-3/OC-3       155.52
        STM-4      STS-12/OC-12      622.08
       STM-8       STS-24/OC-24     1,244.16
       STM-16      STS-48/OC-48     2,488.32

 • CCITT (Consultative Committee for International
   Telephony and Telegraph)
 • ITU (International Telecommunications Union)
    ATM Physical Interface Rates
Framing           Data                                Media
                  Rate
                             Multi-   Single-   Coaxial   UTP–5   UTP–3   STP
                 (Mbps)      Mode      Mode      Cable
                             Fiber     Fiber
DS1              1.544                                                    (TP)
  E1             2.048
  J2             6.23                                                     (TP)
DS3               45
  E3              34
  E4              139                             X
ATM25             25.6
STS 1             51.8
STS3c/STM1        155                                              X
STS 12c/STM4      622
4B/5B (TAXI)      100
8B/10B            155
(Fiberchannel)

  = Standardized         X = Proposed/In Progress

                                                                                 16
Rudimentary ATM Concepts


      • Physical layer
      • Signaling
      • Cell format
      • Connection types



                           17
ATM Building Blocks


         • ATM signaling
           UNI and NNI

         • Virtual connections
           VCC, VP, and VC




                                 18
ATM Signaling
                       Public UNI
                        aka B-ICI
                                                Public ATM Network

        UNI                         NNI




                 NNI
     Token
      Ring
                                       NNI
                          Private ATM Network

     • UNI = User-to-Network Interface
     • NNI = Network-to-Network Interface
     • Cell header content varies depending
       on who’s talking to whom

                                                                     19
    Virtual Path and Virtual Channels
                                                               Virtual Channels (VC)


                    ATM Physical Link              Virtual Path (VP)
            Virtual Channel Connection (VCC)

                          E3
                         OC–12                     Virtual Path (VP)


                                                               Virtual Channels (VC)




                                                                 Virtual Channel
Virtual Channel Connection           Virtual Path
                                                                       (VC)
           (VCC)                         (VP)
                                                                  Logical Path
   Contains Multiple VPs         Contains Multiple VCs
                                                             Between ATM End Points

                       Connection Identifier = VPI/VCI
  ATM Switches
     Input     Output
Port VPI/VCI Port   VPI/VCI                    45

 1       29   2       45                   2
                              29   64
 2       45   1       29           1
 1       64   3       29                   3
 3       29   1       64                       29



      • ATM switches translate VPI/VCI values
      • VPI/VCI value unique only per interface—
        eg: locally significant and may be re-used
        elsewhere in network
                                                     21
VP and VC Switching
VC Switch

                        VCI 1           VCI 2       VCI 3   VCI 4


                                VPI 1           VPI 3   VPI 2           Port 2
VP Switch
                                                                VPI 2
            Port 1

VCI 1
                VPI 1                                           VPI 3
VCI 2



VCI 1
                VPI 4                                           VPI 5
VCI 2

                                                                        Port 3
Virtual Channels
and Virtual Paths
                   Virtual Channel Connection (VCC)

                              Virtual Path
                            Connection (VPC)

 UNI
                                                               UNI
                      NNI                 NNI
           VC                     VP                   VC
          Switch                 Switch               Switch

       VPI = 1              VPI = 2            VPI = 26         VPI = 20
       VCI = 1              VCI = 44           VCI = 44         VCI = 30


• This hop-by-hop forwarding is known as cell relay



                                                                           23
Rudimentary ATM Concepts


      • Physical layer
      • Signaling
      • Cell format
      • Connection types



                           24
    Creating Cells from Packets
                  Dest.      Source                              Frame
       Packet                                     Data
                 Address     Address                             Check



Cells Header       Payload


                      Header         Payload


                SAR                     Header   Payload
     Segmentation and Reassembly

                                                    Header   Payload
    Segmentation Happens at Source

   Reassembly Happens at Destination



                                                                         25
ATM Cell Header

               5 Byte
               Header

   53 Bytes

              48 Byte
              Payload




              ATM Cell
                         26
    ATM Cell Header Details
GFC (4)                                                     VPI (12)
             VPI (8)
                                                                        VCI (16)
VCI (16)                GFC     Generic Flow Control
            PTI   CLP
                                UNI Cells Only!                        PTI   CLP
                        VPI/VCI Identifies Virtual
           HEC                                                     HEC
                                Paths and Channels
                        PTI     Payload Type Identifier
                                3 Bits:
     48 Byte                                                     48 Byte
     Payload                         1. User/Control Data        Payload
                                     2. Congestion
                                     3. Last Cell
                        CLP     Cell Loss Priority Bit
 ATM UNI Cell           HEC     Header Error Check           ATM NNI Cell
                                8 Bit CRC




                                                                                   27
Rudimentary ATM Concepts


      • Physical layer
      • Signaling
      • Cell format
      • Connection types



                           28
ATM Connection Types



         • PVC
         • SVC
         • Soft PVC




                       29
 Connection Types
           S2   1   S6                           S2       S6

       1                 1
  S1                         S8          S1       S3      S5    S8

           S3       S5                            VC
       2                 2

           S4   2   S7                           S4       S7

Connectionless: Packet Routing    Connection Oriented: Cell Switching
• Path 1 = S1, S2, S6, S8         • VC = S1, S4, S7, S8
• Path 2 = S1, S4, S7, S8         • Data takes the same path
                                    and arrives in sequence
• Data can take different path
  and can arrive out of order


                                                                        30
Permanent Virtual Circuit (PVC)
                 Input           Output                          Input               Output
                Port VPI/VCI Port VPI/VCI                    Port VPI/VCI Port VPI/VCI
                 1     29     3     45                        1     33     3     02
                 2     52        4     15                        2         15     3     14
         29
 A               1     64        3     29                        1         64     3     29
                 3     29        1     64                        3         29     1     64
                 1
                            4         15             2


                 2     3
                                 45                      3
                                                                                        C
                                                                     14
 B              30                                       3                      43
                                                16                   2
      Input          Output                                                Input         Output
                                            2        1
     Port VPI/VCI Port VPI/VCI                                            Port VPI/VCI Port VPI/VCI
      1     45     2     16                              4                 1     16     2     43
                                                10
      2     52     1     29                                                3     14     4     10
      1     64     3     29                                  D             1     64     3     29
      3     29     1     64                                                3     29     1     64


• VPI/VCI tables in network equipment
  updated by administrator
                                                                                                      31
  Switched Virtual Circuit (SVC)
                         Input            Output                   Input             Output
                        Port VPI/VCI Port VPI/VCI              Port VPI/VCI Port VPI/VCI
                                                                1     29     3     45


   A                     1       64       3   29                   1         64     3     29
                         3       29       1   64                   3         29     1     64
                        1
   UNI                                4                1
Signaling                                                                     UNI
                                             NNI                           Signaling
                        2        3        Signaling        3
                                                                                          C
   B                                                       3
                                                                       2
             Input           Output                                          Input        Output
                                                   2   1
            Port VPI/VCI Port VPI/VCI                                       Port VPI/VCI Port VPI/VCI
                                                           4

             2     52        1       29
             1     64        3       29                        D             1     64     3     29
             3     29        1       64                                      3     29     1     64


 • Dynamically set up connections
   via signaling
                                                                                                        32
  Switched Virtual Circuit (SVC)
                        Input           Output                   Input             Output
                       Port VPI/VCI Port VPI/VCI             Port VPI/VCI Port VPI/VCI
                        1     29     3     45                 1     29     3     45


   A                    1     64        3   29                   1         64     3     29
                        3     29        1   64                   3         29     1     64
                        1
   UNI                             4                 1
Signaling                                                                   UNI
                                           NNI                           Signaling
                        2     3         Signaling        3
                                                                                        C
   B                                                     3
                                                                     2
             Input          Output                                         Input        Output
                                                 2   1
            Port VPI/VCI Port VPI/VCI                                     Port VPI/VCI Port VPI/VCI
             1     45     2     16                       4                 1     16     2     43
             2     52     1     29
             1     64     3     29                           D             1     64     3     29
             3     29     1     64                                         3     29     1     64



       • Transfer data over newly established link
                                                                                                      33
  Switched Virtual Circuit (SVC)
                         Input            Output                   Input             Output
                        Port VPI/VCI Port VPI/VCI              Port VPI/VCI Port VPI/VCI
                                                                1     29     3     45


   A                     1       64       3   29                   1         64     3     29
                         3       29       1   64                   3         29     1     64
                        1
   UNI                                4                1
Signaling                                                                     UNI
                                             NNI                           Signaling
                        2        3        Signaling        3
                                                                                          C
   B                                                       3
                                                                       2
             Input           Output                                          Input        Output
                                                   2   1
            Port VPI/VCI Port VPI/VCI                                       Port VPI/VCI Port VPI/VCI
                                                           4

             2     52        1       29
             1     64        3       29                        D             1     64     3     29
             3     29        1       64                                      3     29     1     64


 • Dynamically tear down connections
   via signaling
                                                                                                        34
  Soft PVC
                         Input            Output              Input             Output
                        Port VPI/VCI Port VPI/VCI         Port VPI/VCI Port VPI/VCI
                         1     29     3     45             1     29     3     45


                         1       64       3   29              1         64     3     29
   A                     3       29       1   64              3         29     1     64
                        1
   UNI
Signaling                                                                UNI
                                             NNI                      Signaling
                                 3        Signaling                                  C
   B
                                                                  1
             Input           Output                                     Input        Output
                                                      2
            Port VPI/VCI Port VPI/VCI                                  Port VPI/VCI Port VPI/VCI
                                                                        1     16     2     43
             2     52        1       29
             1     64        3       29                   D             1     64     3     29
             3     29        1       64                                 3     29     1     64


 • PVC established manually across UNI
   and dynamically across NNI
                                                                                                   35
ATM Reference Model


    • Physical layer
    • ATM layer
    • ATM adaptation layer
    • A day in the life of a cell



                                    36
ATM Reference Model

               ATM
         Adaptation Layer
              (AAL)


            ATM Layer



          Physical Layer




                            37
  ATM Reference Model
                   Physical Layer
      ATM
Adaptation Layer   Two Sublayers:
     (AAL)
                   • Transmission Convergence (TC)
                      Framing
   ATM Layer          HEC

                   • Physical Media Dependent
Physical Layer
                     (PMD)
                      Physical media coding




                                                     38
   Physical Layer
                   Framing           Data                        Media
                                     Rate
                                    (Mbps)    Multi- Single- Coaxial UTP–5 UTP–3   STP
     ATM                                      Mode Mode Cable
Adaptation Layer                              Fiber   Fiber
     (AAL)         DS1               1.544                                         (TP)
                     E1              2.048
                     J2               6.23                                         (TP)
   ATM Layer
                   DS3                45
                     E3               34
                     E4              139                          X

 Physical Layer    ATM25             25.6
                   STS 1             51.8
                   STS3c/STM1        155                                    X

                   STS 12c/STM4      622
                   4B/5B (TAXI)      100
                   8B/10B            155
                   (Fiberchannel)

                     =                X = Proposed/In Progress
                     Standardized

                                                                                          39
  ATM Reference Model
                     ATM Layer
      ATM
Adaptation Layer
     (AAL)
                   • Cell header insertion/removal

  ATM Layer
                   • Cell Relay
                   • Multiplexes/demultiplexes cells
                     of different connections
 Physical Layer




                                                       40
   ATM Layer
                                           Virtual Channel
                                          Connection (VCC)

     ATM                                    Virtual Path
Adaptation Layer                          Connection (VPC)
     (AAL)
                    UNI                                                         UNI

   ATM Layer                            NNI             NNI
                                VC              VP                  VC
                               Switch          Switch              Switch

 Physical Layer           VPI = 0         VPI = 12           VPI = 26       VPI = 0
                          VCI = 38        VCI = 44           VCI = 44       VCI = 36


           • Provides VPI/VCI values in header
           • Ensures that cells stay in the correct order


                                                                                       41
  ATM Reference Model
               ATM Adaptation Layer
                     (AAL)
      ATM
Adaptation Layer
     (AAL)
                   Two Sublayers:

   ATM Layer
                   • Convergence Sublayer (CS)
                   • Segmentation and
 Physical Layer
                     Reassembly (SAR)




                                                 42
   ATM Adaptation Layer—AAL
     ATM                          AAL
Adaptation Layer   PB X

     (AAL)
                                        S
                                  C
                                        A
                                  S
   ATM Layer                            R



 Physical Layer




AAL = QoS + SAR
• CS—assigns different AAL’s/QoS for different traffic types
• SAR—cell <-> packet


                                                               43
   ATM Adaptation Layer
                   Class    Service   Bit Rate Connection Timing             Application
                           Categories            Mode    Concern              Examples

     ATM           A         AAL1      CBR         Connection-   Yes   • Bandwidth and
                                     (Constant)     Oriented             throughput guaranteed
Adaptation Layer
                                                                       • Good for voice
     (AAL)                                                               and video
                   B         AAL2      VBR         Connection-   Yes   • Best effort bandwidth
                                     (Variable)     Oriented             and throughput
   ATM Layer                          VBR-AT                           • Good for live video,
                                        and                              multimedia,
                                     VBR-NRT
                                                                         LAN-to-LAN
                   C         AAL5      ABR         Connection-   No    • Best effort with
 Physical Layer                      (Available)    Oriented             congestion feedback
                                                                       • Reliable delivery
                                                                         of bursty traffic if
                                                                         latency okay
                   D        AAL3/4     UBR         Connection-   No    • No guarantee
                                       (Un-           less             • For SMDS/LAN
                                     specified)




                                                                                                 44
ATM Reference Model


    • Physical layer
    • ATM layer
    • ATM adaptation layer
    • A day in the life of a cell



                                    45
A Day in the Life of a Cell
           ATM Payload Processing
TCP           TCP Packet                         TCP Header      App Data

IP            IP Datagram           IP Header    TCP Header      App Data

LLC/SNAP                    LLC     IP Header    TCP Header      App Data

     Convergence
     Sublayer (CS)
                   QoS +    LLC     IP Header    TCP Header      App Data
AAL                          Put in 48 Byte Cells—SAT into PDU
        SAR


ATM           Add 5 Byte Headers with VPI/VCI and CLP
                   Transmission Convergence (STS, STM, DS)
PHY
                     Physical Media (MMF, SMF, STP, UDP,…




                                                                            46
A Day in the Life of a Cell
           Traversing the Network
                                     ATM Switch        ATM Layer
                                   Port 1         Port    VPI   VCI
      A     A      P         UNI    P       A
      A     T      H                H       T      1      2     37
      L     M      Y                Y       M      2      1     51
          VPI 2                    Port 2
          VCI 37                    P       A
                                    H       T
                                    Y       M

                       NNI           ATM Switch        ATM Layer
                                   Port 1         Port    VPI   VCI
                                    P       A
                                    H       T      1      1     51
          VPI 3                     Y       M      2      3     39
          VCI 39                   Port 2
      A     A      P         UNI    P       A
      A     T      H                H       T
      L     M      Y                Y       M
Agenda
   • Introduction
   • ATM Fundamentals
      Rudimentary ATM Concepts
      ATM Reference Model
      ATM Adaptation Layer (AAL)
      Traffic Management

   • ATM Transport Standards
   • Campus ATM Internetworking
   • Wrap Up
                                   48
AAL
      • AAL criteria
        Traffic parameters
        QoS parameters

      • The AAL’s
        AAL1—CBR
        AAL2—VBR
        AAL3/4—UBR
        AAL5—ABR

                             49
AAL Criteria
        Contract




        Contract


                             ATM Network
      Contract
  • Traffic Parameters
     Peak cell rate
     Sustainable cell rate
     Maximum burst size
     Minimum Cell Rate

  • Quality of Service
     Delay
     Cell loss

                                           50
AAL Criteria
           Traffic Parameters
• Peak Cell Rate—PCR—Maximum data rate
  a connection can handle without losing data
• Sustainable Cell Rate—SCR—Average ATM
  cell throughput the application is permitted
• Maximum Burst Size—MBS—Size of the
  maximum burst of contiguous cells that
  can be transmitted
• Minimum Cell Rate—MCR—Rate of an
  application’s ability to handle latency

                                                 51
  AAL Criteria
                QoS—Delay

• Maximum Cell Transfer Delay—MCTD
  How long the network can take to transmit
  a cell from one endpoint to another
• Cell Delay Variation Tolerance—CDVT
  Line distortion caused by change in
  interarrival times between cells aka jitter



                                                52
AAL Criteria
          QoS—Cell Loss


• Cell Loss Ratio—CLR
  Acceptable percentage of cells that
  the network can discard due to
  congestion




                                        53
Quality of Service—QoS
       • AAL criteria
         Traffic parameters
         QoS parameters

       • The AAL’s
         AAL1—CBR
         AAL2—VBR
         AAL3/4—UBR
         AAL5—ABR

                              54
                                                  Real Time Voice and Video

The AAL’s
AAL1—Constant Bit Rate (CBR)
Traffic Parameter               QoS
                                               Tolerance


         PCR                    LOW                              HIGH

    Peak Cell Rate
                                           Cell Loss
                                      Cell Delay

                    Overhead

                       5 Byte
                       Header
                                 1 Byte
                      47 Byte
                      Payload


                                                                              55
                                                         Packetized Voice/Video, SNA

The AAL’s
AAL2—Variable Bit Rate
(VBR-RT/VBR-NRT)
Traffic Parameter                       QoS
           PCR                                         Tolerance
       Peak Cell Rate
                                        LOW                              HIGH
           SCR
    Sustainable Cell Rate
           MBS
     Maximum Burst Size                              Cell Loss       Cell Delay
                                              Cell Delay (RT)        (NRT)

                        Overhead

                             5 Byte
                             Header       1–48
                                          Bytes
                            1–47 Byte
                             Payload


                                                                                       56
                                               Public WAN—SMDS

The AAL’s
AAL3/4—Unspecified Bit Rate (UBR)
Traffic Parameter               QoS
                                           Tolerance

  No Guarantees                 LOW                        HIGH
  Send and Pray
                                           Cell Delay
                                                   Cell Loss

                    Overhead

                       5 Byte
                       Header

                      44 Byte
                                 4 Bytes
                      Payload


                                                                  57
                                                   LAN Interconnect for Data

The AAL’s
AAL5—Available Bit Rate (ABR)
Traffic Parameter                   QoS
           PCR                                  Tolerance
       Peak Cell Rate
                                     LOW                         HIGH
           MCR
     Minimum Cell Rate

                                          Cell Loss     Cell Delay

                        Overhead

                           5 Byte   • No cell
                           Header     overhead
                                    • Uses
                          48 Byte     congestion
                          Payload     feedback
                                      instead

                                                                           58
Traffic Management


 • Why traffic management?
 • Traffic control techniques
 • AAL5/ABR congestion feedback
 • Buffers are your friend



                                  59
Why Traffic Management?



 • Proactively combat congestion
 • Provision for priority control
 • Maintain well-behaved traffic




                                    60
Why Traffic Management?
 Cell Loss—Data’s Critical Enemy
             Ethernet (1500 Bytes) = 32 Cells
                FDDI (4470 Bytes) = 96 Cells
    IP over ATM–1577 (9180 Bytes) = 192 Cells

                    TCP/IP Packet

                                    X


  • Lose one cell and the rest are useless
  • Need to re-transmit 32+ cells for one cell lost
  • Congestion collapse is the result

                                                      61
 Traffic Control Techniques



• Connection management—Acceptance
• Traffic management—Policing
• Traffic smoothing—Shaping




                                 62
Traffic Control Techniques
     Connection Management
        Contract




        Contract



                             ATM Network
      Contract
  • Traffic Parameters
     Peak cell rate
     Sustainable cell rate
     Burst tolerance
     Etc.

  • Quality of Service
     Delay
     Cell loss

                                           63
Traffic Control Techniques
    Connection Management
Connection Admission Control (CAC)
  I want a VC:                          CAC
  X Mbps                         Can I Support this
  Y Delay                         Reliably without
  Z Cell Loss                    Jeopardizing Other
                                     Contracts
      Guaranteed QoS Request


          No
           or
   Yes, Agree to a
   Traffic Contract   Contract
                                   ATM Network
Traffic Control Techniques
                  Traffic Management
 Usage Parameter Control (UPC) aka Policing

       Contract                    You are
                            Not in Conformance
                             with the Contract.
                             What Should the
                               Penalty Be??




                                                  ?DECISION?
  REBEL
APPLICATION                                • PASS
                               ATM Network • MARK CLP BIT
                                           • DROP
Traffic Control Techniques
           Traffic Management

                        UPC
                                      Marked
       0     0    0               0       1      0


                  D              ?DECISION?
                  r             • PASS
                  o
                  p
                                • MARK CLP BIT
                                • DROP
• CLP Control—When congested drop marked cells
• Public UNI—Generic Cell Rate Algorithm (GCRA)


                                                     66
Traffic Control Techniques
            Traffic Management

                           UPC
                                        Marked
        0    0     0                0       1    0


                   D
                   r   3    2
                   o
                   p

    •   Intelligent Packet Discard—IPD
    •   Discard cells from same ‘bad’ packet
    •   Tail packet discard
    •   Maximize “Goodput”
                                                     67
Traffic Control Techniques
                      Traffic Smoothing
    I Want to
 Comply With My
Contract. So, I Will                                    Go Ahead,
  Smooth/Shape                                         Make My Day
    My Traffic

                         Shaper

        Actual Data
                                  Shaped Data


Private ATM Network                             Public ATM Network


                 • Traffic shaper at customer site
                 • Changes traffic characteristics
                 • Leaky bucket algorithm
                                                                     68
Traffic Control Techniques
        Buffers Are Your Friend
• Absorb traffic bursts from
  simultaneous connections
• Switches schedule traffic based on priority
  of traffic according to QoS
• Switch must reallocate buffers as the traffic
  mix changes
• Effective buffering maximizes throughput
  of usable cells as opposed to raw cells
  (aka goodput)

                                                  69
ATM Internetworking

         • Challenges
         • RFC1483
         • RFC1577
         • LANE
         • MPOA


                        70
ATM Internetworking
             The Challenges
Existing and New                  New
  Applications                 Applications
                    API
Network Address

 MAC Address

      ???

 ATM Address                  ATM Address

    • MAC address to ATM address resolution
    • No Standard ATM API
                                              71
ATM Internetworking
           Overlay Model
                  ATM Addresses
          Router or             Router or
           Switch                Switch


                       ATM
     Ethernet         Network         Ethernet


                  Direct-Attached
                      Stations
                Network Addresses,
                 MAC Addresses

    • Multiple layers of addressing
                                                 72

				
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