ATM and the Internet Over Satellite Networks by pengxuebo

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									               ATM and the Internet Over
                  Satellite Networks

                              Prakash Chitre
                          COMSAT Laboratories
                          Clarksburg, MD 20871
                              (301) 428-4167
                   e-mail: prakash.chitre@comsat.com




ATM & INTERNET 7/99 1
                  ATM and Internet Via Satellite


          I     ATM Via Satellite: Key Challenges
          I     ATM Over (Point-to-point) Satellite
                Links
          I     Internet Over (Point-to-point)
                Satellite Links
          I     ATM/Internet Satellite Mesh
                Networks
          I     Conclusions

ATM & INTERNET 7/99 2
             ATM Via Satellite: Key Challenges
I   Providing Fiber-like Quality (Cell Loss Ratio and Cell Error
    Ratio)
      ! Time-varying bit error rates and bit error distribution
I   Effect on Throughput Performance due to Geosynchronous
    Satellite Delay
      ! ATM Traffic Management, Congestion Control
      ! End-to-end protocols, e.g., TCP
I   Efficient Bandwidth Use
      ! ATM and other ATM related protocols (such as ATM speech) are
        not bandwidth efficient
      ! Satellite resources are relatively expensive
      ! Dynamic Bandwidth-on-Demand Concepts
I   Meeting Cell Delay Variation QoS Requirements
      ! Satellite TDMA framing can result in unacceptable cell delay
        variation

ATM & INTERNET 7/99 3
            Seamless Integration of Satellite
               and Terrestrial Networks




      I     Satellite link transparent to the end user

      I     Service provisioning in a cost-efficient manner




ATM & INTERNET 7/99 4
                         Steps for Achieving
                        Seamless Integration




                        I   Modify existing standards
                        I   Develop new standards
                        I   New Satcom interfaces
                        I   New satellite networks




ATM & INTERNET 7/99 5
                   Service Specific Connection
                    Oriented Protocol (SSCOP)




                    I   SSCOP is the basic protocol for error
                        recovery in ATM

                    I   Very efficient over satellite links even
                        at gigabits per second




ATM & INTERNET 7/99 6
                    Communications and Interoperability
                            Section/TR 34.1
Major Accomplishments
I   Established a liaison with ATM Forum Wireless ATM Group for the
    joint development of satellite ATM network architectures, protocols,
    mobility standards
I   Worked closely with Internet Engineering Task Force (IETF) for
    internet protocols to work well over satellite
     ! TCPSAT Group has been established
I   ATM traffic management (TM 4.0)
     ! Modifications to accommodate satellite delay were approved by ATM Forum
I   ATM speech
     ! Worked with ATM Forum to develop ATM speech standards to be bandwidth
          efficient
I   Common air interface for satellite systems
     ! Standardize common air interfaces for a range of satellite systems from satellite
          personal communications systems to broadband satellite systems


    ATM & INTERNET 7/99 7
         Asynchronous Transfer Mode (ATM)
                  over Satellite




ATM & INTERNET 7/99 8
       COMSAT ATM Link Accelerator - ALA

                        G Provides fiber-like quality over satellite links for ATM
                          traffic

                        G Improved BER (10-9 or better), very low cell loss ratio
                            ! Cell header and payload protected using
                              powerful FEC codes
                            ! Adaptive FEC to maximize bandwidth utilization
                                  I FEC overhead 0% to 8%, depending on

                                     link quality
                                  I Idle cells stripped off

                            ! Interleaving to combat burst errors
                                  I Can correct up to 72 octet burst errors


                        G Prioritized traffic management
                             ! High priority, low jitter for CBR and VBR traffic
                                (e.g., video)
                             ! Low priority, large buffers for ABR traffic
                                (e.g., LAN data)

                        G Lossless data compression for ABR traffic on selected
                          VCs
                            ! Can double effective throughput

                        G Selectable T1, E1, DS-3, E3, RS-449 ATM interface

                        G Satellite interface up to 8 Mb/s




ATM & INTERNET 7/99 9
                            CLA-2000/ATM Performance v/s BER


                          1E+00
                          1E-02
Cell Loss + Error Ratio




                          1E-04
                          1E-06                                                                  Without ALA
                          1E-08
                          1E-10
                          1E-12
                          1E-14
                          1E-16               With ALA
                          1E-18
                          1E-20
                              1E-01   1E-02    1E-03     1E-04   1E-05      1E-06     1E-07   1E-08   1E-09    1E-10

                                                           Bit E rror Ra t e ( burs t y )




  ATM & INTERNET 7/99 10
                   Example Operational Network
                                   UUNet
                                   Backbone

                                                     Miami
                                              Cisco
                                              Router         ATM
                                                             Switch
                                                       DS3
                                                                                                                             34 Mb/s

                                      Puerto Rico            DS3 Undersea Cable
                                     ATM
                         34 Mb/s     Switch      DS3
                                     Cisco                     ALA/ALE
                                     Router
                                                 DS3                 Aa m
                                                                     l
                                                                     r

                                                                   Po e
                                                                    wr
                                                                                        C MS T A L - 0 0
                                                                                        O A
                                                                                       L DDs a
                                                                                       Ci  p y
                                                                                           l
                                                                                                 A2




                                     ATM
                                     Switch                        l r
                                                                   Aa
                                                                  Po e
                                                                   wr
                                                                     m
                                                                                         S
                                                                                     C O MA T A A 2 0
                                                                                        s l y
                                                                                    L CDi p a
                                                                                              L- 0




                                                       E3

                                     Argentina                                                                                         10 Mb/s
                                                                ALA/ALE
                                                        E3                   l r
                                                                             Aa m

                                                                            Po e
                                                                             wr
                                                                                                             A
                                                                                                        C O MS T A L - 0 0
                                                                                                        C s l y
                                                                                                        L DDp a
                                                                                                                   A2




                                       ATM
                                       Switch                                                                A     A2
                                                                                                        C O MS T A L - 0 0
                                                                                                        C s l y
                                                                                                        L DDp a
                                                                             Aa m
                                                                             l r




                                                E3
                                                                             wr
                                                                            Po e




                                       Cisco
                                       Router



                                   South American
                                   Backbone



ATM & INTERNET 7/99 11
       TCP/IP Issues for Satellite Networks


 I    TCP window size
 I    Buffer requirements at end nodes and routers
 I    Slow start
 I    Effect of bit errors
 I    Retransmission strategy
 I    Congestion control strategy
 I    Queue management



ATM & INTERNET 7/99 12
              Maximum Throughput for Single
               TCP Connection as a Function
                     of Window Size




ATM & INTERNET 7/99 13
                           Current Work on TCP
                              Enhancements



                    I    Random Early Discard (RED)
                         scheme
                    I    Selective Ack (SACK)
                    I    Fast retransmit recovery
                         enhancements
                    I    Slow start enhancements



ATM & INTERNET 7/99 14
                                             COMSAT Link Accelerator/
                                            Internet - CLA-2000/Internet

                                                                                                                                                              G IP Routing over satellite and wireless links
                                                                                                                                                              G Provides fiber-like quality over satellite links
                                                                                                                                                              G Improved BER (10-11 or better)
                                                                                                                                                                    ! Packets protected using powerful Reed-
                                                                                                                                                                      Solomon coding
                                                                                                                                                                    ! Interleaving to combat burst errors
                                                                                                                                                                           I Can correct 640 bit burst error
       10BaseT     Modem                                                                                                                 10BaseT
       Ethernet                       RS-449                                                                                             Ethernet
       Hub                            0 - 4 Mbit/ s                                                                                      Hub                  G Bandwidth Expansion
                        Al
                         m
                        o r
                        Pw
                              CSA2
                              M
                              OAL 0
                               l
                              Ci
                              Dp
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                                                                                                                       Am
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                                                                                                                                                                   ! Adaptive Coding based on Measured Error rate
                        COMSAT
                  10BaseT
                         CLA/IP
                                                                                                                    COMSAT
                                                                                                                     CLA/IP                                        ! Reed-Solomon coding overhead 0% - 7%
                                                                                                                                                              G Lossless Data Compression Option
                                                                                                                                                                    ! 2:1 compression ratio typical
                                                                                                                                              Internet              ! Up to T1 link rate
                                                                                                                                                              G RED Queue Management
                                                                                                                                                              G TCP Proxy (Spoofing)
                                                                                                                                                              G Satellite Interface, RS449, up to 4 Mbit/s symmetric
                                        CLA-2000/Internet                                                                                                     G Support for asymmetric rate links, low-speed links
                                                                                                                                     Satellite/WAN Port
                                                                                                                                     RS-449, up to 4 Mbit/s
                                                                                       COM   A
                                                                                             S       AL A   2 0 0



                                                                                   C     i
                                                                                        DD   l
                                                                                             p   y




                                                                          l
                                                                          A    m




                                                                        Po w   r




Ethernet/IP Port
10BaseT
                                                           T    -   0
                                                      L   s a
                                                a r

                                                  e




           ATM & INTERNET 7/99 15
                                               CLA-2000/Internet Usage



                                                                                      CLA-2000/Internet as Router using Ethernet



10BaseT     Modem                                                     10BaseT
Ethernet                       RS-449                                 Ethernet
Hub                            0 - 4 Mbit/ s                          Hub
                       OAL 0
                       CSA2
                       M
                       Dp
                       Ciy
                         l                                    A
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                                                              M A0
                                                             COAL 2
                  m
                 Al                                           i l
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                 Pw                                     Am
                                                        l
                                                        Pr
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                                                        o




                  COMSAT                             COMSAT
                   CLA/IP                             CLA/IP
           10BaseT




                                                                           Internet




                                                                                                                      Modem
                                                                                                                                             RS-449
                                                                                                            Router                                                                Router
                                                                                                                                             0 - 4 Mbps
                                                                                                                                     S 2
                                                                                                                                     M A
                                                                                                                                     A
                                                                                                                                    COAL 0
                                                                                                                                    CDl
                                                                                                                                     p
                                                                                                                                    Di y                               OS L 2
                                                                                                                                                                         A 0
                                                                                                                                                                       C MA A 0
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                                                                                                                        COMSAT                               COMSAT
                                                                                                                     CLA-2000/Internet                    CLA-2000/Internet
                                               CLA-2000/Internet as Transparent                                  Serial Link
                                                                                                                 0 - 8 Mbps
                                               Frame Processor using Serial Port
                                                                                                                                                                                       Internet




   ATM & INTERNET 7/99 16
             CLA/Internet TCP-Proxy Overview


 User Workstation /                                                                                         User Workstation /
      Server                   CLA-2000/Internet                                                                 Server
                                                                               CLA-2000/Internet


      Applns.                       TCP Proxy                                        TCP Proxy                      Applns.

       TCP                     TCP          TCP                                TCP           TCP                    TCP

       IP                      IP           IP                                 IP            IP                      IP

      Ethernet                Ethernet   Satt. Link                         Satt. Link     Ethernet              Ethernet
                                         Layer                              Layer

                                                                                                   TCP Window =
             TCP Window =                                                                           4 - 64 kbytes
                                                      TCP Window =
              4 - 64 kbytes                             256 kbytes
                                                                                                      Internet




Most PCs, workstations use TCP window size of 8 - 24 kbytes
Limits throughput per connection over geo satellites to 128 - 384 kbps
Max. TCP window size allowed = 64 kbytes (RFC 1323 enhancements allow larger sizes)

TCP Proxy enables full link rate throughput per connection
CLA-2000/IP uses TCP with large windows over satellite segment (RFC 1323)
Connection set-up/tear-down not spoofed

   ATM & INTERNET 7/99 17
          CLA/Internet TCP-Proxy Overview



   User Workstation /                                                                                     User Workstation /
        Server                     CLA-2000/Internet                                                           Server
                                                                               CLA-2000/Internet


         Applns.                         TCP Proxy                                  TCP Proxy                      Applns.

          TCP                      TCP          TCP                            TCP           TCP                   TCP
           IP                       IP           IP                            IP            IP                     IP

         Ethernet                  Serial     Satt. Link                    Satt. Link
                                              Layer                                       Serial                 Ethernet
                                                                            Layer


                   TCP Window =                                                                    TCP Window =
                     4-64 kbytes                           TCP Window =                              4-64 kbytes
                                                             256 kbytes
                      Internet                                                                        Internet




Most PCs, workstations use TCP window size of 8 - 24 kbytes
Limits throughput per connection over geo satellites to 128 - 384 kbps
Max. TCP window size allowed = 64 kbytes (RFC 1323 enhancements allow larger sizes)

TCP Proxy enables full link rate throughput per connection
CLA-2000/IP uses TCP with large windows over satellite segment (RFC 1323)
Connection set-up/tear-down not spoofed

     ATM & INTERNET 7/99 18
           CLA/Internet TCP-Proxy Mechanism


                                                                                                                                                           S
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                                                                                                                                                           A




                                                                                                                             CLA-2000/Internet
                                                                                                                                                           i y
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                                                      Cisco
                                                                    M 2
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                                                                                                 Internet                                                         Internet
                                   Internet                               Internet
            Internet
                                                                                                Data
                                                                                          1     (1kbyte)
                                                                                          2
      1 Data (1kbyte)          1                                                          3
      2                        2                                                     32 ms4             1
      3                        3                                                          5             2
                                                      Data (1kbyte)                       6
32 ms 4                        4
                                                                                          7
                                                                                                        3                            Data (1kbyte)
      5                 500 ms 5                                                                        4
      6                        6                                                          8
                                                                                                        5
      7                        7                                                                        6
      8                        8                                                                        7
                                                                                                        8                                              Data
                                                                                                    Ack 9                                            1 (1kbyte)
                                                                                                        1
                                                                                                                                                     2
               Ack                                                                                      0                     500 ms                 3          32 ms
                                                                                                                                                     4
                                                                                                                                                     5
                                                                                                                                                     6
                                                                                                                                                     7
                                                                                                                                                     8

                                                                    Ack
       W = 8 kbytes
       Throughput                                                                                                                                                    Ack
         = 8 kbytes/32 ms                                                                                                1
         = 2 Mbps                                                                                                        2
                                                                                                                         8    Ack
                                              W = 8 kbytes
                                              Throughput                                                      W = 128 kbytes        W = 8 kbytes
                                               = 8 kbytes/500 ms                                              Throughput            Throughput
                                                                                              W = 8 kbytes                           = 8 kbytes/32 ms
                                               = 128 kbps                                     Throughput        = 128 kbytes/500 ms
                                                                                                                = 2 Mbps             = 2 Mbps
                                                                                               = 8 kbytes/32 ms
                                                                                               = 2 Mbps




 ATM & INTERNET 7/99 19
                      CLA/Internet Single TCP Connection
                                 Performance
                    2000
                    1800
                    1600                                        CLA, r = 2.048 Mbps
  Throughput Kbps




                    1400                                       W = 8 kB

                    1200
                    1000
                                              Cisco, r = 2.048 Mbps
                    800                      W = 192 kB
                    600
                    400                                                Cisco, r = 2048 kbps
                    200                                               W = 8 kB
                      0
                       1.E-09   1.E-08    1.E-07      1.E-06          1.E-05       1.E-04     1.E-03

                                                       BER

                       Single Connection, Large Data Transfer (20 - 40 min)
                       Sun Solaris 2.6
                       One-way Delay=250 ms



ATM & INTERNET 7/99 20
                   CLA-2000/IP Performance




ATM & INTERNET 7/99 21
                                                                 Throughput Gain Ratio
                                  TC




                                                           0.5
                                                                        1.5
                                                                                         2.5




                                                       0
                                                                 1
                                                                                2
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ATM & INTERNET 7/99 22
                                    st
                                      sc
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                                            t
                                       HT
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                                                                                           BER=10-4




                                      W
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                                                                                           BER=10-8




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                                                                                                               Measurements




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                                                                                                          CLA/Internet Compression
                              Linkway 2000



         I Multiservice Platform for Bandwidth-on-Demand Multimedia
               applications
         I Multicarrier, Multirate, TDMA Mesh Network
         I ATM, IP, Frame Relay, ISDN, SS7 Interfaces
         I Internet Routing (RIP, OSPF, BGP)
         I Automatic Adaptive Bandwidth Assignment
         I Various Terminal Sizes in a Single Interoperable Network
         I Highly Integrated Board Including Modem in the Indoor Unit




ATM & INTERNET 7/99 23
                                LINKWAY Overview




On Demand High Speed Access for
! Virtual Private Networks               ! Multimedia & Video Teleconferencing
! Multinational Corporate Networks       ! Internet Service Providers

       ATM & INTERNET 7/99 24
                         Bandwidth Management




                    I Fixed Bandwidth Allocation


                    I Dynamic Bandwidth Allocation




ATM & INTERNET 7/99 25
                  Dynamic Bandwidth Allocation
                           Algorithm




                   I Adaptive to Traffic Changes


                   I Fair Assignment




ATM & INTERNET 7/99 26
                         Internet Routing Protocols



         I Routing Information Protocol (RIP)

         I Open Shortest Path First (OSPF)

         I Border Gateway Protocol (BGP)




ATM & INTERNET 7/99 27
                            Conclusions


       New generation of satellite link and networking
       products from COMSAT:

               G Provides high quality ATM and Internet Services
                 over satellite links

               G Provides efficient use of satellite bandwidth

               G Meets customer demands




ATM & INTERNET 7/99 28

								
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