DNS by linxiaoqin

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									               TELCOM 2110 - Today’s
                     Lecture
• Week 11 - 13 November 2000
     –    Designing for Change and Growth
     –    Domain Name serving
     –    Managing Address Assignments
     –    VLAN’s
     –    Enterprise Networks (WAN)
     –    Transmission Methods
     –    VPN’s

Week 11                   Telcom 2110       1
   Designing for Change and Growth




Week 11         Telcom 2110          2
                     Scaleable Designs
• Want to ensure any design is scaleable
• Want a flexible design that can be changed
• Issues to consider
     –    Cable plant
     –    Backbone equipment
     –    Network protocols
     –    Internet connectivity


Week 11                     Telcom 2110        3
                Scaleable Cable Plant
• Need to design for the long term, as cable
  plant is expensive and most likely will
  outlast most of the network equipment
• Need to balance aesthetics verses the ease
  of upgrading/repairing
     – if cable is behind wall verses hung from ceiling
• If I were designing from scratch - Fiber to
  the desktop gives the longest life

Week 11                  Telcom 2110                      4
          Scaleable Backbone Equipment
• Use modular chassis devices so you can add
  newer technologies without needing to
  replace the whole device
• Use one of the major players in the field to
  try and protect your investment
• Make sure to have expansion room both in
  backplane bandwidth, number of ports, and
  port bandwidth

Week 11             Telcom 2110              5
          Scaleable Network Protocols
• Used to have different protocols for each
  specific network
     – X.25, IPX for Novell
• With the advent and growth of the Internet,
  TCP/IP has taken over
     – Windows NT, Novell Version 5, Unix




Week 11                 Telcom 2110             6
          Scaleable Internet Connectivity
• When we plan or decide to connect our
  internal network to the Internet, we need to
  ensure that we can co-exist
• Need to discuss Domain Name Serving and
  Assigning Network Addresses




Week 11             Telcom 2110                  7
                      Network Growth
• Network growth can be caused by:
     –    Increased number of clients
     –    increased number of servers
     –    increase in the amount of traffic
     –    increase in the geographic area covered
     –    increased number of applications




Week 11                     Telcom 2110             8
                Network Growth Patterns
• There is no set formula for growth
• Network is affected by
     –    changes to traffic patterns
     –    server placement
     –    protocols used
     –    application types
     –    security functions



Week 11                     Telcom 2110   9
          Domain Name Serving




Week 11          Telcom 2110    10
               Name Serving
• DNS - Domain Name Serving
• WINS - Windows Internet Name Service




Week 11          Telcom 2110             11
          What does Name Serving Do?
• Converts a Name into an IP address
     – www.sis.pitt.edu is IP 136.142.116.10
• Converts an IP address into a Name
• DNS holds a registry of all IP addresses and
  the associated userID/hostnames




Week 11                 Telcom 2110            12
          ping HostB.training.microsoft.com




                         Domain Name               Router
                         System Server

                 1                                  2


              Name                          IP Address
            Resolution                       Resolved

                                       Domain Name =
                                       HostB.training.microsoft.com

Week 11                       Telcom 2110                             13
             Example of DNS - Request
NTW1 BACKUP DNS:Std Qry for www.test.com. of type Host Addr on class INET addr.
FRAME: Base frame properties
ETHERNET: ETYPE = 0x0800 : Protocol = IP: DOD Internet Protocol
    ETHERNET: Destination address : 02608C8D95F8
    ETHERNET: Source address : 02608C3B85C1
IP: ID = 0x4200; Proto = UDP; Len: 58                 To DNS Server
    IP: Source Address = 131.107.2.214
    IP: Destination Address = 131.107.2.216
UDP: Src Port: Unknown, (1035); Dst Port: DNS (53); Length = 38 (0x26)
DNS: 0x1:Std Qry for www.test.com. of type Host Addr on class INET addr.
    DNS: Query Identifier = 1 (0x1)
    DNS: DNS Flags = Query, OpCode - Std Qry, RD Bits Set, RCode - No error
    DNS: Question Entry Count = 1 (0x1)
    DNS: Answer Entry Count = 0 (0x0)
    DNS: Name Server Count = 0 (0x0)
    DNS: Additional Records Count = 0 (0x0)
    DNS: Question Section: www.test.com. of type Host Addr on class INET addr.
        DNS: Question Name: www.test.com.
                                               Question
        DNS: Question Type = Host Address
        DNS: Question Class = Internet address class


   Week 11                           Telcom 2110                        14
             Example of DNS - Reply
BACKUP NTW1 DNS Std Qry Resp. for www.test.com of type Host Addr class INET
   addr.
FRAME: Base frame properties
ETHERNET: ETYPE = 0x0800 : Protocol = IP: DOD Internet Protocol
    ETHERNET: Destination address : 02608C3B85C1
    ETHERNET: Source address : 02608C8D95F8
                                                      From DNS Server
IP: ID = 0xE49D; Proto = UDP; Len: 74
    IP: Source Address = 131.107.2.216
    IP: Destination Address = 131.107.2.214
UDP: Src Port: DNS, (53); Dst Port: Unknown (1035); Length = 54 (0x36)
DNS: 0x1:Std Qry Resp. for www.test.com. of type Host Addr on class INET addr.
DNS: Question Section: www.test.com. of type Host Addr on class INET addr.
    DNS: Question Name: www.test.com.
         DNS: Question Type = Host Address
         DNS: Question Class = Internet address class
    DNS: Answer section: www.test.com. of type Host Addr on class INET addr.
         DNS: Resource Name: www.test.com.
         DNS: Resource Type = Host Address
         DNS: Resource Class = Internet address class
         DNS: Time To Live = 3600 (0xE10)
         DNS: Resource Data Length = 4 (0x4)
                                                 ANSWER
         DNS: IP address = 131.107.2.100
    Week 11                            Telcom 2110                       15
          The Domain Name Space
• A hierarchical name space




Week 11            Telcom 2110    16
                                                       T he
                                                       R oot




         a p ra
                             com                o rg   gov              ed u         us          it




       i n -a d d r

                                   l lb e a n                  p i tt          cmu
                                                                                           pa




1 30                  136


                                                       www              c is
                                                                                     k12



                            1 42




 Week 11                                               Telcom 2110                              17
             The 3 top-level Domains
• apra
     – A special domain for address to name mappings
• generic
     – Seven 3-character domains. Sometimes called
       organizational domains
• country
     – 2 character country codes as found in ISO 3166



Week 11                 Telcom 2110                  18
                    Generic Domains

          D o m ain               D escr ip tio n
            co m      co m m er ical o r g an iz atio n
            ed u      ed u catio n al in stitu tio n s
            gov       o th er U .S . g o ver n m en t
             in t     in ter n atio n al o r g an iz atio n s
            m il      U S . Militar y
            n et      n etw o r k (IS P s)
            org       o th er o r g an iz atio n s



Week 11                     Telcom 2110                         19
                      Country Domains


          D o m ain              D escr ip tio n
             us       U n ited S tates
             uk       U n ited K in g d o m
             it       Italy
            zw        Zim b ab w e
             ae       U n ited Ar b E m ir ates



Week 11                       Telcom 2110          20
          Delegation of Responsibility

   The NIC maintains information about the
    top-level domains
   These are know as the Root Name Servers




Week 11             Telcom 2110               21
             The Root Name Servers

                        N am e                     Ad d r ess
          A.R O O T -S E R V E R S .N E T .    198.41.0.4
          B .R O O T -S E R V E R S .N E T .   128.9.0.107
          C .R O O T -S E R V E R S .N E T .   192.33.4.12
          D .R O O T -S E R V E R S .N E T .   128.8.10.90
          E .R O O T -S E R V E R S .N E T .   192.203.230.10
          F .R O O T -S E R V E R S .N E T .   192.5.5.241
          G .R O O T -S E R V E R S .N E T .   192.112.36.4
          H .R O O T -S E R V E R S .N E T .   128.63.2.53
          I.R O O T -S E R V E R S .N E T .    192.36.148.17
          J.R O O T -S E R V E R S .N E T .    198.41.0.10
          K .R O O T -S E R V E R S .N E T .   193.0.14.129
          L .R O O T -S E R V E R S .N E T .   198.32.64.12
          M.R O O T -S E R V E R S .N E T .    202.12.27.33


Week 11                           Telcom 2110                   22
                    The NIC

   The Network Information Center
   http://rs.internic.net
   Assigns both Domain Names and IP
    addresses
   Responsibility now been turned to the
    Private Sector - Network Solutions at
    www.networksolutions.com and now others
    such as AOL.
Week 11             Telcom 2110           23
                                   com


    Zone 1


             Microsoft                              Zone 3


                                                             MKTG
                    CORP
                                    Zone 2      Name
                  Name                          Server
                  Servers

                                           R&D
                         Name
                         Server


Week 11                           Telcom 2110                  24
          Local
                         Iterative
          Name Server
                         Queries
                                                       Root
                           2                           Name Server
                               3

                             4
                                                              gov
                                      5                       Name Server
                             6
             1
                   8
   Recursive                                       7
    Query


                                      whitehouse.gov
                        DNS
                                      Name Server
                        Client


Week 11                              Telcom 2110                        25
          Local Network use of DNS
• If you have an internal WEB server, you
  need to have a way for the users to find it
  using a common name vice its IP address
• Can by done by setting up a .host file or by
  by the WEB server configuration
• Can get information by using nslookup.exe
  on the host machine if supported (NT)


Week 11             Telcom 2110                  26
     Managing Address Assignments




Week 11          Telcom 2110        27
               Managing Address
                 Assignments
• We can use Static Addressing, where we
  assign each PC a IP address. Must be a
  valid one if the PC will be directly
  connected to the internet.
• Addresses can also can be managed by Host
     – BootP
     – DHCP



Week 11            Telcom 2110            28
                           BootP
• The bootstrap protocol
     – RFC 1542
• Allows the client PC to get its IP address
  from the server, the file to download, the
  Host IP address
     – used normally to boot a “dumb” terminal




Week 11                 Telcom 2110              29
                               BootP
• Requires maintenance of a database that
  maps
     –    IEEE
     –    IP addresses
     –    Hostnames
     –    other information (image files and such) is then
          loaded using another protocol (TFTP)



Week 11                     Telcom 2110                  30
                     DHCP
• Dynamic Host Configuration Protocol
     – RFC 1541




Week 11           Telcom 2110           31
                           DHCP
• Allow automatic registration of computer
  systems
• Allow the reuse of IP addresses
• Need three things for DHCP
     – need a DHCP server
     – routers must be able to forward DHCP
     – a DHCP client must be configured on the client


Week 11                 Telcom 2110                 32
Non-DHCP                                        DHCP
 Client                                         Client




                                                         IP Address1



                    IP Address2


                                                            DHCP Database
                                                             IP Address1
           DHCP                      DHCP                    IP Address2
           Client                    Server                  IP Address3




Week 11                           Telcom 2110                          33
            Understanding how DHCP
                     Works
• Typical process:
     – user turns on the endstation
     – endstation sends out a DHCP request to the
       network asking for an IP address
     – the DHCP request is a broadcast frame
     – the DHCP request floods the subnet, the router
       would fill in the Gateway IP and directs the
       request to the DHCP Server


Week 11                 Telcom 2110                     34
             Understanding how DHCP
                Works-Continued
     – the DHCP Server gets the request, and allocates
       an IP address for the client that fits the correct
       subnet
     – the DHCP Server sends the request frame back
       to the client
     – If the client accepts the IP, it send out a
       broadcast to allow it to use the IP address
     – the DHCP Server will acknowledge the request


Week 11                   Telcom 2110                  35
 DHCP Client                        DHCP Servers

               IP Lease Request


                 IP Lease Offer


               IP Lease Selection


                   IP Lease
               Acknowledgment




Week 11               Telcom 2110            36
            DHCPDISCOVER
     Source IP Address = 0.0.0.0
     Dest. IP Address = 255.255.255.255
     Hardware Address = 08004....




                                          IP Router



                               DHCPOFFER
                     Source IP Address = 131.107.3.24
                     Dest. IP Address = 255.255.255.255
                     Offered IP Address = 131.107.8.13
                     Client Hardware Address = 08004...
                     Subnet Mask = 255.255.255.0
   DHCP Client       Length of Lease = 72 hours           DHCP Server
                     Server Identifier = 131.107.3.24


Week 11                              Telcom 2110                    37
          DHCPREQUEST
  Source IP Address = 0.0.0.0
  Dest. IP Address = 255.255.255.255
  Hardware Address = 08004....
  Requested IP Address = 131.107.8.13
  Server Identifier = 131.107.3.24



                                        IP Router



                               DHCPACK
                    Source IP Address = 131.107.3.24
                    Dest. IP Address = 255.255.255.255
                    Offered IP Address = 131.107.8.13
                    Client Hardware Address = 08004...
                    Subnet Mask = 255.255.255.0
                    Length of Lease = 72 hours
  DHCP Client                                            DHCP Server
                    Server Identifier = 131.107.3.24
                    DHCP Option: Router = 131.107.8.1

Week 11                             Telcom 2110                    38
            DHCP Address Lease
• The client does not permanently own the
  assigned address, it is leased for a given
  amount of time, set by the
  acknowledgement frame sent by the DHCP
  Server
• Client gives it back based on logging off the
  network or expiration of the lease


Week 11             Telcom 2110               39
              Other DHCP issues
• Although, this system allows users to move
  a machine and to be assigned a new address,
  it becomes harder to track the user in the
  audit logs that use the IP address
• Security may be made harder when using
  DHCP vice static addresses
• Can use IPCONFIG utility to check status


Week 11            Telcom 2110             40
                     Proxy Servers
• A Proxy Server can be used in many
  different ways
     – Address conservation functions
     – Security Services




Week 11                 Telcom 2110     41
          Proxy Servers




Week 11     Telcom 2110   42
                 Proxy Server Basics
• Address Translation
     – Use Private (ex 192.168.X.X) on the client
       machines
     – Client will only communicate TCP/IP with
       Gateway unit, known as Proxy Server
     – Proxy Server translates Private IP address to
       allowed Internet IP addresses
     – Internet machines only see the Proxy server


Week 11                  Telcom 2110                   43
                 Proxy Server Basics
• Security Services
     – Inside machines are isolated from the Internet
     – Only exposure or compromise risk is the proxy
       server
     – Proxy server can log and track access made
       through it
     – Normally used in conjunction with a Firewall
       setup


Week 11                 Telcom 2110                 44
          Virtual Local Area Networks
                   (VLAN’s)




Week 11              Telcom 2110        45
                         VLAN’s
• Description
     – Group of devices on one or more physical
       LAN’s that are configured as they are logically
       attached to the same wire
     – May be located on different physical LAN
       segments
     – LAN’s based on LOGICAL instead of
       PHYSICAL connections


Week 11                  Telcom 2110                 46
                  VLAN Use
• Switches have the ability to support more
  than one subnet on a single switch
• Used to help alleviate traffic congestion
  without adding more bandwidth
• Used to separate out users into logical
  groups of workers, regardless of actual
  physical location


Week 11             Telcom 2110               47
                    VLAN Types
• Port Based - Configured at each switch port
     – Port X on Switch A belongs to VLAN 1
     – Port Y on Switch B belongs to VLAN 1
• MAC Address Based - Uses the end stations
  MAC address for VLAN Assignment
     – Host X MAC belongs to VLAN 1
     – Host Y MAC belongs to VLAN 1



Week 11                Telcom 2110            48
             VLAN Types (continued)
• Protocol Based - Uses LAN protocol to
  determine VLAN assignment
     – Host X uses IP and belongs to VLAN 1
     – Host Y uses IPX and belongs to VLAN 2
• Dynamic Based - A User Profile (stored as
  a database) determine VLAN assignment
     – When Host X logs in, the profile says to
       connect the user to VLAN 1

Week 11                  Telcom 2110              49
                  VLAN Strategies
• Three main ways to deploy a VLAN
     – At the User Level
     – At the Wiring Closet Level
     – AT the Distribution Switch Level




Week 11                 Telcom 2110       50
              User Level VLAN
• Users belong to a specific VLAN regardless
  of where they attach to the network
• User can “roam” on the network
• Beneficial when traffic stays on the VLAN
• However, broadcast traffic will follow the
  user



Week 11            Telcom 2110             51
                          User Level VLAN
Question:
                            ENTERPRISE                                          ENTERPRISE
                              SWITCH                                              SWITCH
What happens
when Host A
moves to a different
Workgroup Switch?            ROUTER                                              ROUTER




                          DISTRIBUTION                                       DISTRIBUTION
                             SWITCH                                             SWITCH




              WORKGROUP                  WORKGROUP             WORKGROUP                         WORKGROUP
                SWITCH                     SWITCH                SWITCH                            SWITCH




                                                     Host C                           Host B
                                                     VLAN 2        Host A             VLAN 1
                                                                   VLAN 1


                                                                   Broadcast Domain for VLAN 1




 Week 11                                             Telcom 2110                                             52
                       User Level VLAN
Broadcast
                         ENTERPRISE                                          ENTERPRISE
Domain follows             SWITCH                                              SWITCH

the movement
of Host A

                          ROUTER                                              ROUTER




                       DISTRIBUTION                                       DISTRIBUTION
                          SWITCH                                             SWITCH




           WORKGROUP                  WORKGROUP             WORKGROUP                         WORKGROUP
             SWITCH                     SWITCH                SWITCH                            SWITCH




             Host A                               Host C                           Host B
             VLAN 1                               VLAN 2                           VLAN 1



                                                                Broadcast Domain for VLAN 1




 Week 11                                          Telcom 2110                                             53
          Wiring Closet Level VLAN
• Provides a means for broadcast domain
  control
• Good when traffic mostly flows to
  enterprise servers
• People must be physically close together on
  same VLAN
• Broadcast traffic will not follow the user


Week 11             Telcom 2110             54
                        Wiring Closet VLAN
Question:
                          ENTERPRISE                                          ENTERPRISE
                            SWITCH                                              SWITCH
What happens
when Host A
moves to a different
Workgroup Switch?
                           ROUTER                                              ROUTER




                        DISTRIBUTION                                       DISTRIBUTION
                           SWITCH                                             SWITCH




            WORKGROUP                  WORKGROUP            WORKGROUP                          WORKGROUP
              SWITCH                     SWITCH               SWITCH                             SWITCH




                                                                                                   VLAN 1 based on
                                                                                                   Workgroup Switch

                                                   Host C                           Host B
                                                   VLAN 1        Host A             VLAN 1
                                                                 VLAN 1


                                                                 Broadcast Domain for VLAN 1


 Week 11                                           Telcom 2110                                                55
                        Wiring Closet VLAN
Broadcast
Domain stays              ENTERPRISE
                            SWITCH
                                                                           ENTERPRISE
                                                                             SWITCH
with the switch,
does not follow
Host A if it
moves to a                 ROUTER                                           ROUTER

different switch.
Host A belongs
to a new VLAN
                        DISTRIBUTION                                    DISTRIBUTION
                           SWITCH                                          SWITCH




            WORKGROUP                  WORKGROUP            WORKGROUP                       WORKGROUP
              SWITCH                     SWITCH               SWITCH                          SWITCH




                                                   Host C                        Host B          Host A
                                                   VLAN 1                        VLAN 1          VLAN 2



                                                              Broadcast Domain for VLAN 1



 Week 11                                            Telcom 2110                                           56
          Distribution Switch Level
                    VLAN
• Middle ground between User and Wiring
  Closet designs
• For traffic that goes to both enterprise and
  distributed services
• If users move but stay on the same
  distribution switch - Same VLAN
• If users move to different distribution
  switch - Different VLAN

Week 11              Telcom 2110                 57
              Distribution Switch VLAN
Question:
                          ENTERPRISE                                          ENTERPRISE
                            SWITCH                                              SWITCH
What happens
when Host A
moves to a different
Distribution
                           ROUTER                                              ROUTER
Switch?



                        DISTRIBUTION                                       DISTRIBUTION
                                                                                                   VLAN 1 based on
                           SWITCH                                             SWITCH               Distribution Switch


            WORKGROUP                  WORKGROUP            WORKGROUP                          WORKGROUP
              SWITCH                     SWITCH               SWITCH                             SWITCH




                                                   Host C                           Host B
                                                   VLAN 1        Host A             VLAN 1
                                                                 VLAN 1


                                                                 Broadcast Domain for VLAN 1


 Week 11                                           Telcom 2110                                                 58
            Distribution Switch VLAN
                          ENTERPRISE                                          ENTERPRISE
                            SWITCH                                              SWITCH

Broadcast Domain
follows Host A
since it stays on
the same                   ROUTER                                              ROUTER


distribution
switch.

                        DISTRIBUTION                                       DISTRIBUTION
                           SWITCH                                             SWITCH




            WORKGROUP                  WORKGROUP            WORKGROUP                          WORKGROUP
              SWITCH                     SWITCH               SWITCH                             SWITCH




                                                   Host C                           Host B          Host A
                                                   VLAN 1                           VLAN 1          VLAN 1



                                                                 Broadcast Domain for VLAN 1




 Week 11                                           Telcom 2110                                               59
              Why Use VLAN’s
• Say you want workers assigned to the same
  project to be group logically together for
  control of traffic but they are physically
  located in different physical areas - VLAN
• Say you want to divide up the broadcast
  domain in a large flat network without using
  a bunch of routers - VLAN


Week 11             Telcom 2110             60
           How Does Network Know
• So, how does the network know where to
  sent the data packets when a VLAN has
  been put into place?
     – Frames can be tagged with the VLAN
       information
     – IEEE 802.10 puts the VLAN information
       between the MAC and LAN address space



Week 11               Telcom 2110              61
          Enterprise Networks (WAN)




Week 11             Telcom 2110       62
          Enterprise Networks (WAN)
• Enterprise Networks connect several parts
  of the corporation into one complete
  network
• Called a Wide Area Network since it
  usually can span several cities and states
• Made up of LANs connected together using
  some form of telecommunications service


Week 11            Telcom 2110             63
             WAN Requirements
• WAN links will always be slower than the
  LAN links
• Addressing takes on more importance
• Will need a router to connect to the outside
  world




Week 11             Telcom 2110                  64
                         WAN Basics




                            LAN
                            Links



          This is our typical LAN that interconnects our
                    Computers at a Single Site
Week 11                     Telcom 2110                    65
                       WAN Basics




 Now, how do I     1



interconnect the
separate LANs?

   Week 11              Telcom 2110   66
          Transmission Methods




Week 11           Telcom 2110    67
              Transmission Methods
• Open Space Transmission
     – Microwave
     – Satellite
• Transmission Service
     – Circuit Switched
     – Dedicated Service
     – Packet Switched Services



Week 11                Telcom 2110   68
          Open Space Transmission
                 Microwave
                  Satellite




Week 11            Telcom 2110      69
          Microwave Open Space
              Transmission
• Earth Bound
• Uses microwave towers with directional
  antennas
• Point to Point arrangement
• 2 to 25 GHz
• Unobstructed path of 30 Miles maximum



Week 11           Telcom 2110              70
          Microwave Open Space
              Transmission




Week 11         Telcom 2110      71
                Satellite Open Space
                   Transmission
• Satellite in geosynchronous orbit
     – 22,300 miles above earth
• Signal Delay 1/4 second
• C, Ku, and Ka Bands
• Higher Frequency:
     – smaller equipment and less costly, But are most
       subject to attenuation caused by rain


Week 11                 Telcom 2110                  72
                           Satellite Open Space
                              Transmission

                               Satellite




                                                  Satellite dish




          Satellite dish




                           1




Week 11                             Telcom 2110                    73
          Transmission Service




Week 11          Telcom 2110     74
             Transmission Service
• What happens when we want our LAN to
  connect to the outside world
• I need to have a method to link the different
  sites together or link to a common network
  cloud like the Internet
• I will use some for of Transmission Service
  to make the connection


Week 11             Telcom 2110               75
          Transmission Service




              Third Party Network




Week 11             Telcom 2110     76
             Transmission Service Types
• Circuit Switched
     – Analog Circuit Switched Service
          • Dial Up Lines
     – Digital Circuit Switched Service
          • ISDN
          • ADSL
• Dedicated Service
     – T1/T3 Leased Line Service


Week 11                     Telcom 2110   77
             Transmission Service Types -
                     Continued
• Packet Switching Service
     –    X.25
     –    Frame Relay
     –    SMDS
     –    ATM
     –    Internet via an ISP




Week 11                     Telcom 2110     78
          Circuit Switched




Week 11        Telcom 2110   79
          Circuit Switched Services
• Sometimes called a “Metered” service
• Billed on a time-in-use basis
• Cost of the service my vary based on time
  of day or other algorithm
• For example: Long Distance Telephone
  calls



Week 11            Telcom 2110                80
            Circuit Switched Services
• Analog Dial-up Modems
     – 56 Kbps Maximum
     – Hard to get connections above 40 Kbps
• Digital Circuit Switched Service
     – ISDN
     – ADSL




Week 11                 Telcom 2110            81
                                  ISDN
• BASIC RATE INTERFACE (BRI)
     – One ISDN BRI line contains 3 channels
          • Two "Bearer" or B channels that carry switched
            voice, data, image transmission. One "Delta" or D
            channel that carries call set-up info (16 Kbps), but
            can also carry user packet data transmissions.
     – Bandwidth
          • 64 Kbps per Bearer channel for 128 Kbps total.
     – $120 Installation, $40 month + .02 cents min

Week 11                       Telcom 2110                          82
                                 ISDN
• PRIMARY RATE INTERFACE (PRI)
     – ISDN Primary (PRI) is an all digital service
       that consists of a 23B+ one D connections.
     – Bandwidth
          • With a total bandwidth of 1.544 Mbps, it is designed
            for transmission through a standard North American
            T-1 trunk
     – $700 installation, $300 per month



Week 11                      Telcom 2110                      83
                     ISDN Summary


          BRI ISDN                   PRI ISDN




Week 11                Telcom 2110              84
                    ASDL
• Asymmetric Digital Subscriber Line
  (ADSL)
• Up to 4x faster than T1 (~ 7Mbps)
• Normally use is for internet access(TCP/IP),
  download is faster service than upload
• Would not be used for WAN campus
  connections today but there are some moves
  afoot to standardize it so it could be

Week 11             Telcom 2110              85
          ASDL Example




Week 11     Telcom 2110   86
                 ASDL Pricing
•   Installation cost ~ $500
•   640K download $40 month - upload at 90K
•   1.6M download $60 month - upload at 90K
•   7.1M download $110 month - upload 680K




Week 11             Telcom 2110           87
                 ADSL Future
• The ADSL Forum is looking at methods to
  interconnect ADSL connections over wide
  areas using ATM.
• Looking to be able to use ATM benefits to
  set of VPN across the ATM backbone to
  support the corporate needs of high speed
  inter-links between corporate offices across
  the country
• RFC 2364 for TCP/IP over ATM
Week 11             Telcom 2110              88
          Dedicated Services




Week 11         Telcom 2110    89
              Dedicated Service
• Also called Leased Lines
• Billed at a fixed rate
• Rate based on pre defined factors, such as
  distance and bandwidth
• T-1 (1.544Mbps) or T-3 (45 Mbps) line
  leased from ATT is an example



Week 11             Telcom 2110                90
                    Dedicated Service
• Numerous Suppliers
     –    ATT
     –    MCI/Sprint
     –    Qwest
     –    Global Crossing
     –    GTE
     –    Level Three
     –    Frontier Networks

Week 11                   Telcom 2110   91
             Dedicated Service

                                              T-1
                                              Line
            Router


                                              Third Party
                                               Network
                                    CSU/DSU
                      Multiplexer
          Video




Week 11              Telcom 2110                       92
                 What is a CSU/DSU?
• Channel Service Unit (CSU).
     – Used to connect to a digital communications
       link. It is the termination point for the digital
       signal. Provides diagnostic loopback tests to
       check for potential transmission problems.
• Digital Service Unit (DSU).
     – It makes it possible to transmit digital data over
       digital channels. It converts signals from the
       LAN equipment into the bipolar digital signals
       used on digital lines.

Week 11                   Telcom 2110                      93
          T-1 Pricing




Week 11        Telcom 2110   94
          T-1 Pricing




Week 11       Telcom 2110   95
          Packet Switched Services




Week 11            Telcom 2110       96
          Packet Switched Service
• Provides for simultaneous connection to
  many different points following a mesh
  topology
• Most flexible service for organizations
  requiring connections to many different
  locations
• Can provide bandwidth on demand
• X.25, Frame Relay, SMDS, ATM

Week 11            Telcom 2110              97
                 X.25 Service
• Has provided packet switching service since
  the 1970’s
• Useful for light traffic loads
• Was normally used with terminals
  connecting to mainframes
• Considered too slow for LAN-to-LAN
  transmission


Week 11            Telcom 2110              98
                Frame Relay
• Frame Relay is a high performance WAN
  protocol
• Physical and data-link layer of OSI
• Early 1990s as an upgrade to X.25
• More efficient and easier to implement
• Flexible bandwidth support



Week 11           Telcom 2110              99
                      Frame Relay
• Frame Relay - Connection Oriented
     – 64 Kbps - $800 install, $175 month
     – T1 - $1000 install, $435 month




Week 11                 Telcom 2110         100
                           SMDS
• SMDS (Switched Multi-Megabit Data
  Service) - Connectionless Packet Switched
     – Bell Atlantic 56 Kbps - $600 install, $225 month
     – Bell Atlantic T1 - $1000 install, $550 month
     – Bell Atlantic 34Mbps - $2000 install, $2000
       month
• Alternative to leased lines
• 53 byte cells at DS1 and DS3
• Uses its own protocol
Week 11                 Telcom 2110                 101
             SMDS




Week 11   Telcom 2110   102
                        ATM
• ATM/Cell Relay delivers high-capacity
  transmission at speeds of 10 Mbps to 620
  Mbps to support simultaneous voice,
  data, and video exchanges within state-of-
  the-art telecommunications and
  computing environments
• We will discuss ATM details next week


Week 11             Telcom 2110                103
                         Internet
• Due to the explosive growth of the Internet,
  more companies are using it for WAN
  connectivity.
• Issues to consider:
     – Reliability- Is my data time sensitive?
     – Security- Who will be able to see my data?
• Can use a VPN across the internet to
  resolve some of these concerns

Week 11                 Telcom 2110                 104
                    Internet
• Remember, the Internet is IP, so you may
  not be able to use it for time sensitive
  material such a videoconferencing
• Cost is the biggest driver, two small T-1
  ones may only cost a few hundred dollars a
  month, vice a long haul T-1that could cost
  several thousand a month.


Week 11            Telcom 2110             105
                                  Internet Example

                        Long Haul T-1 Line Coast to Coast

                                   $5000 per Month
 City                                                                           City




          T-1 Line to Local ISP                         T-1 Line to Local ISP
                                     INTERNET
            $500 per Month                                  $500 per Month
 City                                                                           City




Week 11                                Telcom 2110                               106
          Service Level Agreements-SLA
• A Service Level Agreement is a document
  that guarantee a certain level of service for
  circuit services purchased from circuit
  providers such as ATT, Sprint, MCI,
  QWEST, GTE,…
• UUNET, MCI’s ISP guarantees 100%
  network availability with a maximum round
  trip latency of 85 msec.

Week 11             Telcom 2110              107
            Service Level Agreements-SLA
• A SLA will define performance for items
  such as:
     –    connection restoration time
     –    traffic latency
     –    data delivery rate
     –    network availability
     –    circuit establishment



Week 11                    Telcom 2110      108
          Monitoring WAN Traffic
• We have software to allow monitoring our
  WAN traffic
• Ensure both sides comply with SLA
• One package is by Visual Networks




Week 11            Telcom 2110               109
Monitoring WAN Traffic
Monitoring WAN Traffic
Monitoring WAN Traffic
Monitoring WAN Traffic

								
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