atm and the internet over satellite networks · atm & internet 7/99 1 atm and the internet over...

ATM & INTERNET 7/99 1

ATM and the Internet OverSatellite Networks

Prakash ChitreCOMSAT LaboratoriesClarksburg, MD 20871

(301) 428-4167e-mail: [email protected]


ATM and Internet Via Satellite

n ATM Via Satellite: Key Challengesn ATM Over (Point-to-point) Satellite

Linksn Internet Over (Point-to-point)

Satellite Linksn ATM/Internet Satellite Mesh

Networksn Conclusions


ATM Via Satellite: Key Challengesn Providing Fiber-like Quality (Cell Loss Ratio and Cell Error

Ratio)F Time-varying bit error rates and bit error distribution

n Effect on Throughput Performance due to GeosynchronousSatellite DelayF ATM Traffic Management, Congestion Control

F End-to-end protocols, e.g., TCP

n Efficient Bandwidth UseF ATM and other ATM related protocols (such as ATM speech) are

not bandwidth efficient

F Satellite resources are relatively expensive

F Dynamic Bandwidth-on-Demand Concepts

n Meeting Cell Delay Variation QoS RequirementsF Satellite TDMA framing can result in unacceptable cell delay

variation


Seamless Integration of Satelliteand Terrestrial Networks

n Satellite link transparent to the end user

n Service provisioning in a cost-efficient manner


Steps for AchievingSeamless Integration

n Modify existing standards

n Develop new standards

n New Satcom interfaces

n New satellite networks


Service Specific Connection Oriented Protocol (SSCOP)

n SSCOP is the basic protocol for errorrecovery in ATM

n Very efficient over satellite links evenat gigabits per second


Major Accomplishmentsn Established a liaison with ATM Forum Wireless ATM Group for the

joint development of satellite ATM network architectures, protocols,mobility standards

n Worked closely with Internet Engineering Task Force (IETF) forinternet protocols to work well over satellite

F TCPSAT Group has been established

n ATM traffic management (TM 4.0)F Modifications to accommodate satellite delay were approved by ATM Forum

n ATM speechF Worked with ATM Forum to develop ATM speech standards to be bandwidth

efficient

n Common air interface for satellite systemsF Standardize common air interfaces for a range of satellite systems from satellite

personal communications systems to broadband satellite systems

Communications and InteroperabilitySection/TR 34.1


Asynchronous Transfer Mode (ATM)over Satellite


COMSAT ATM Link Accelerator - ALA

l Provides fiber-like quality over satellite links for ATMtraffic

l Improved BER (10-9 or better), very low cell loss ratioF Cell header and payload protected using

powerful FEC codesF Adaptive FEC to maximize bandwidth utilization

n FEC overhead 0% to 8%, depending on link qualityn Idle cells stripped off

F Interleaving to combat burst errorsn Can correct up to 72 octet burst errors

l Prioritized traffic managementF High priority, low jitter for CBR and VBR traffic (e.g., video)F Low priority, large buffers for ABR traffic (e.g., LAN data)

l Lossless data compression for ABR traffic on selectedVCs

F Can double effective throughput

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

l Satellite interface up to 8 Mb/s


Bit E rror Rat e (burs ty )

1E-201E-18

1E-161E-14

1E-121E-10

1E-081E-06

1E-041E-021E+00

1E-101E-091E-081E-071E-061E-051E-041E-031E-021E-01

With ALA

Without ALA

CLA-2000/ATM Performance v/s BERC

ell L

oss

+ E

rro

r R

atio


M i a m i

Puer to R ico

Argent ina

Cisco Router ATM

Switch

34 Mb/s

Cisco Router

ATMSwitch

Cisco Router

ATMSwitch

ALA/ALE

ALA/ALE

ATMSwitch

DS3 Undersea Cable

E3

E3

DS3

DS3

DS3

E3

UUNetBackbone

Example Operational Network

34 Mb/s

10 Mb/s

CO M SA T A LA -2 00 0

LC D Di spl ay

Al ar m

P ow er

i

C O MS A T AL A- 20 00

L C D D s pl ay

Al arm

P ow er

C O M SA T A LA -2 00 0

LC D Ds pl ay

Al ar m

P ow er

C O M SA T A LA -2 00 0

LC D Ds pl ay

Al ar m

P ow er

South AmericanBackbone


TCP/IP Issues for Satellite Networks

n TCP window size

n Buffer requirements at end nodes and routers

n Slow start

n Effect of bit errors

n Retransmission strategy

n Congestion control strategy

n Queue management


Maximum Throughput for SingleTCP Connection as a Function

of Window Size


Current Work on TCPEnhancements

n Random Early Discard (RED)scheme

n Selective Ack (SACK)n Fast retransmit recovery

enhancementsn Slow start enhancements


COMSAT Link Accelerator/ Internet - CLA-2000/Internet

l IP Routing over satellite and wireless links

l Provides fiber-like quality over satellite links

l Improved BER (10-11 or better)F Packets protected using powerful Reed- Solomon codingF Interleaving to combat burst errors

n Can correct 640 bit burst error

l Bandwidth ExpansionF Adaptive Coding based on Measured Error rateF Reed-Solomon coding overhead 0% - 7%

l Lossless Data Compression OptionF 2:1 compression ratio typicalF Up to T1 link rate

l RED Queue Management

l TCP Proxy (Spoofing)

l Satellite Interface, RS449, up to 4 Mbit/s symmetric

l Support for asymmetric rate links, low-speed linksSatellite/WAN Port RS-449, up to 4 Mbit/s

Ethernet/IP Port 10BaseT

CLA-2000/Internet

10BaseT Ethernet Hub

Internet

RS-449 0 - 4 Mbit/s

10BaseT

Modem 10BaseT Ethernet Hub

COMSATCLA/IP

COMSATCLA/IP

T - 0

L s a

a r

e

C O M SA A L A 2 0 0

C D Di pl y

Al m

P o w r

C OMSA A LA 200C DDi ply

Al m

Pow r

COM SA ALA 200

CDD iplyA lm

Po wr


CLA-2000/Internet Usage

Router

Internet

RS-449 0 - 4 Mbps

Serial Link0 - 8 Mbps

Modem

COMSATCLA-2000/Internet

COMSATCLA-2000/Internet

Router

10BaseT Ethernet Hub

Internet

RS-449 0 - 4 Mbit/s

10BaseT

Modem 10BaseT Ethernet Hub

COMSATCLA/IP

COMSATCLA/IP

CLA-2000/Internet as Router using Ethernet

CLA-2000/Internet as TransparentFrame Processor using Serial Port

C OMSA A LA 200C DDi ply

Al mPow r

COM SA ALA 200CDD iply

A lm

Po wr

CO MSA AL A20 0CD Dip ly

Al m

P ow r

C OMSA A LA2 00

CD Dip lyAl m

Pow r


CLA/Internet TCP-Proxy Overview

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

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

Ethernet

TCP Proxy

TCP TCP

Ethernet

TCP Proxy

TCPTCP

Ethernet

IP

TCP

Applns.

IP

TCP

Applns.

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

Satt. LinkLayer

Satt. LinkLayer

User Workstation /Server

TCP Window = 4 - 64 kbytes

TCP Window = 256 kbytes

TCP Window = 4 - 64 kbytes

Ethernet

Internet

IP IP IPIP


CLA/Internet TCP-Proxy Overview

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

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

IP

TCP Proxy

IP

Serial

IP

TCP Proxy

TCP

IP

TCP

IP

TCP

Applns.

IP

TCP

Applns.

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

Satt. LinkLayer

Satt. LinkLayer

User Workstation /Server

Internet

Ethernet Serial Ethernet

TCP Window = 256 kbytes

TCP TCP

TCP Window = 4-64 kbytes

Internet

TCP Window = 4-64 kbytes


Cisco

CLA/Internet TCP-Proxy Mechanism

12345678910

128

500 ms

Data (1kbyte)

Ack

W = 8 kbytes Throughput = 8 kbytes/32 ms = 2 Mbps


12345678

32 ms

Data (1kbyte)

Ack 12345678

32 ms

Data (1kbyte)

Ack

12345678

500 msData (1kbyte)

Ack

W = 8 kbytes Throughput = 8 kbytes/500 ms = 128 kbps

12345678

32 ms

Data (1kbyte)

Ack

W = 8 kbytesThroughput = 8 kbytes/32 ms = 2 Mbps

InternetInternet Internet

Internet Internet

CLA-2000/Internet


COMSA ALA 200C DDip lyAlm

Pow r

COMS A A LA200CDDi ply

Al m

Pow r

COM SA A LA200CDD iply

A lmPow r

COMSA ALA 200C DDip ly

Alm

Pow r


CLA/Internet Single TCP Connection Performance

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

0

200

400

600

800

1000

1200

1400

1600

1800

2000

1.E-09 1.E-08 1.E-07 1.E-06 1.E-05 1.E-04 1.E-03

BER

Th

rou

gh

pu

t Kbp

s

Cisco, r = 2.048 Mbps

W = 192 kB

Cisco, r = 2048 kbps

W = 8 kB

CLA, r = 2.048 Mbps

W = 8 kB


CLA-2000/IP Performance


CLA/Internet CompressionMeasurements

0

0.5

1

1.5

2

2.5

3

TCP a

ck

Canter

bury

Corpu

s

C pro

g file

s

Postsc

ript

HTML

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d

Wind

ows .

exe

Unix .e

xe Ppt

Web

Site A

maz

on

Web

Site cn

nfn

pdf

real-

audio

real-

video gif jpe

g

zip fil

es

Th

rou

gh

pu

t G

ain

Rat

io

BER=10-4 BER=10-8


Linkway 2000

n Multiservice Platform for Bandwidth-on-Demand Multimediaapplications

n Multicarrier, Multirate, TDMA Mesh Network

n ATM, IP, Frame Relay, ISDN, SS7 Interfaces

n Internet Routing (RIP, OSPF, BGP)

n Automatic Adaptive Bandwidth Assignment

n Various Terminal Sizes in a Single Interoperable Network

n Highly Integrated Board Including Modem in the Indoor Unit


LINKWAY Overview

On Demand High Speed Access forF Virtual Private Networks

F Multinational Corporate Networks

F Multimedia & Video Teleconferencing

F Internet Service Providers


Bandwidth Management

n Fixed Bandwidth Allocation

n Dynamic Bandwidth Allocation


Dynamic Bandwidth AllocationAlgorithm

n Adaptive to Traffic Changes

n Fair Assignment


Internet Routing Protocols

n Routing Information Protocol (RIP)

n Open Shortest Path First (OSPF)

n Border Gateway Protocol (BGP)


Conclusions

New generation of satellite link and networkingproducts from COMSAT:

l Provides high quality ATM and Internet Servicesover satellite links

l Provides efficient use of satellite bandwidth

l Meets customer demands

atm and the internet over satellite networks · atm & internet 7/99 1 atm and the internet over...

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