atm and the internet over satellite networks · atm & internet 7/99 1 atm and the internet over...
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ATM & INTERNET 7/99 1
ATM and the Internet OverSatellite Networks
Prakash ChitreCOMSAT LaboratoriesClarksburg, MD 20871
(301) 428-4167e-mail: [email protected]
ATM & INTERNET 7/99 2
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 & INTERNET 7/99 3
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
ATM & INTERNET 7/99 4
Seamless Integration of Satelliteand Terrestrial Networks
n Satellite link transparent to the end user
n Service provisioning in a cost-efficient manner
ATM & INTERNET 7/99 5
Steps for AchievingSeamless Integration
n Modify existing standards
n Develop new standards
n New Satcom interfaces
n New satellite networks
ATM & INTERNET 7/99 6
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
ATM & INTERNET 7/99 7
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
ATM & INTERNET 7/99 9
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
ATM & INTERNET 7/99 10
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
ATM & INTERNET 7/99 11
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
ATM & INTERNET 7/99 12
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
ATM & INTERNET 7/99 14
Current Work on TCPEnhancements
n Random Early Discard (RED)scheme
n Selective Ack (SACK)n Fast retransmit recovery
enhancementsn Slow start enhancements
ATM & INTERNET 7/99 15
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
ATM & INTERNET 7/99 16
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
ATM & INTERNET 7/99 17
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
ATM & INTERNET 7/99 18
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
ATM & INTERNET 7/99 19
Cisco
CLA/Internet TCP-Proxy Mechanism
12345678910
128
500 ms
Data (1kbyte)
Ack
W = 8 kbytes Throughput = 8 kbytes/32 ms = 2 Mbps
W = 128 kbytes Throughput = 128 kbytes/500 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
W = 8 kbytes Throughput = 8 kbytes/32 ms = 2 Mbps
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
ATM & INTERNET 7/99 20
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
ATM & INTERNET 7/99 22
CLA/Internet CompressionMeasurements
0
0.5
1
1.5
2
2.5
3
TCP a
ck
Canter
bury
Corpu
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C pro
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Site cn
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real-
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Th
rou
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ain
Rat
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BER=10-4 BER=10-8
ATM & INTERNET 7/99 23
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
ATM & INTERNET 7/99 24
LINKWAY Overview
On Demand High Speed Access forF Virtual Private Networks
F Multinational Corporate Networks
F Multimedia & Video Teleconferencing
F Internet Service Providers
ATM & INTERNET 7/99 25
Bandwidth Management
n Fixed Bandwidth Allocation
n Dynamic Bandwidth Allocation
ATM & INTERNET 7/99 26
Dynamic Bandwidth AllocationAlgorithm
n Adaptive to Traffic Changes
n Fair Assignment
ATM & INTERNET 7/99 27
Internet Routing Protocols
n Routing Information Protocol (RIP)
n Open Shortest Path First (OSPF)
n Border Gateway Protocol (BGP)