NASA/TM--97-206297

Enhancing End-to-End Performance of

Information Services Over Ka-Band

Global Satellite Networks

Kul B. Bhasin, Daniel R. Glover, William D. Ivancic, and Thomas C. vonDeak

Lewis Research Center, Cleveland, Ohio

Prepared for the

Third Ka Band Utilization Conference

sponsored by the IIC-Istituto Internazionale delle Comunicazioni

Sorrento, Italy, September 15-18, 1997

National Aeronautics and

Space Administration

Lewis Research Center

December 1997

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ENHANCINGEND-TO-ENDPERFORMANCEOFINFORMATIONSERVICES

OVERKA-BANDGLOBALSATELLITENETWORKS

KulB.Bhasin,DanielR.Glover,WilliamD.Ivancic,andThomasC.vonDeak

NationalAeronauticsandSpaceAdministration

Lewis Research Center

21000 Brookpark Road

Cleveland, Ohio 44135 U.S.A

(216) 433-3676, (216) 433-2847, (216) 433-3494, (216) 433-3277

(216) 433-8705 (FAX)

bhasin@lerc.nasa.gov, dglover @lerc.nasa.gov, wivancic@lerc.nasa.gov, tvondeak@lerc.nasa.gov

1. ABSTRACT

The Internet has been growing at a rapid rate as the key medium to provide information services such as e-mail,

WWW and multimedia etc., however its global reach is limited. Ka-band communication satellite networks are

being developed to increase the accessibility of information services via the Internet at global scale. There is

need to assess satellite networks in their ability to provide these services and interconnect seamlessly with

existing and proposed terrestrial telecommunication networks.

In this paper the significant issues and requirements in providing end-to-end high performance for the delivery of

information services over satellite networks based on various layers in the OSI reference model are identified.

Key experiments have been performed to evaluate the performance of digital video and Internet over satellite-like

testbeds. The results of the early developments in ATM and TCP protocols over satellite networks are

summarized.

2. INTRODUCTION

NASA has been at the forefront of telecommunications technology and Ka-Band experimentation through the

Advanced Communications Technology Satellite Program (ACTS) conducted at the NASA Lewis Research

Center in Cleveland, Ohio. In addition to this activity NASA has now partnered with the satellite industry to

address the issues concerning seamless interoperability between satellite and terrestrial networks in the emerging

GII. Interoperability becomes an issue whenever the standards used on one side of a network interface are

incompatible with network conditions on the other side of the interface or become significantly inefficient in their

operation. This is the case with many aspects of the ATM and Internet protocols. This paper outlines the issues

that are currently recognized and being addressed by NASA with its industry partners.

The depiction in Figure 1 outlines the complexity and scope of the issues between satellite and terrestrial

communications in a top level format. Some of the key features that come to light are that:

High DIta .4 / Z .............. / I "_ A

Wireline Networks Access Networks Wireless Networks

FIGURE 1 - Top Level Reference Model

NASA/TM--97-206297 1
1. Low-Earth-Orbit, Middle-Earth-Orbit, andGeosynchronous-Earth-Orbit (LEO/MEO/GEO) satellites will

provide a wide range of data rates to a variety of implementation scenarios ranging from low data rate mobile

users served by a LEO satellite constellation to SONET supporting fixed earth stations served by a single

GEO satellite.

2. The LEO/MEO/GEO satellite configurations may directly interconnect with one another utilizing intelligent

on-board switching electronics.

3. The various implementation scenarios will have to seamlessly interconnect with each other and the terrestrial

networks in order to achieve the goals of the GII.

The methodology of addressing the large scope of interoperability has been to develop reference models and

identify the key interoperability issues at each of the layers and its respective interfaces (Figure 2). In recognition

of the two driving protocols of the GII, ATM and TCP/IP, the protocol stack models are ATM, TCP/IP over

ATM, and TCP/IP residing directly on the physical layer. The remainder of the paper is therefore divided into

ATM and TCP/IP issues.

I Application Layer I

I ATM Layer I

Physical Layer

(Hardware Radio Link)

I Application Layer I

I TCP/IP Layer I

I ATM Layer I

Physical Layer

(Hardware Radio Link)

I Application Layer I

TCP/IP Layer ]

Physical Layer I

(Hardware Radio Link)

FIGURE 2 - Layers of Examination by Protocol Stack

3. ATM ISSUES

Asynchronous Transfer Mode (ATM) is a protocol originally conceived by the telecommunication industry to

handle multimedia traffic over wide area networks (WANs). The protocol is a connection oriented cell switched 1

protocol developed for fiber optic systems which have near-error-free performance characteristics. The protocol

encompasses features of both the data link layer and the routing layer, layers 2 and 3 of the Open Systems

Interface (OSI) model.

The main features of ATM are guaranteed quality of service (QoS), ease of switching and multimedia compliant.

The ATM cell structure of 53 bytes - a 5 byte header and 48 byte payload - was designed for high bandwidth

implementations with low switching and routing overhead. The 5 byte header of each cell contains all the

information necessary for the end-to-end delivery of the cell. If the header of the cell is corrupted beyond the

corrective abilities of the included 1 byte CRC check then the cell is discarded. The small header and limited

routing rules allow the switching to be performed in high speed hardware. The small size of the ATM cell - 53

bytes - allows small internal buffers to be used in the switches keeping cell delay and jitter to a minimum.

The main requirements of ATM are: a near-error-free link, fixed cell size and order of cells must be maintained.

These requirements directly effect the design of satellite and wireless networks that wish to utilize ATM.

The following interrelated issues must be addressed for ATM to be utilized over satellite (and other wireless)

links:

• Quality of Service

• Traffic Management and Congestion Control

• Routing

• Handover

• Signaling

• Multicasting

] We defined cell switching as a subset of packet switching where all packets are of one fixed size.

NASA/TM--97-206297 2
, Security

, CommonAirInterface

Qualityof Service

Quality of service is application dependent. Voice quality may be acceptable with bit error rates of 10E-6 or

higher. Medical imaging may find 10E-7 acceptable as file transfers are not delay sensitive and the high-level

protocols will resolve any problems resulting from non-error free transmission. Thus, the question to be resolved

is: "What link quality will the satellites have to provide in order to be globally interoperable with terrestrial

systems?"

The Satellite Networks and Architectures Branch (SN&AB) performed QoS measurements using an EF-Data

SDM-9000 IDR Modem [1]. The results presented here indicate that the requirements for all classes of ATM

service as proposed in ITU-T Draft Recommendation 1.356" may not be accommodated by transmission services

designed to just comply with ITU-T Recommendation G.826, such as the IDR service as specified in Tables 2

and 3, IDR Performance, p. 36A, Intelsat Earth Station Standard IESS-308 (Rev. 7A). For certain classes of

ATM it will be necessary to augment the error performance of the basic IDR service through the use of the

optionally specified Reed-Solomon outer codec or other link enhancer schemes. The results presented here do

not include such performance enhancing techniques. Figure 3 also illustrates the satellite link availability

requirements as contained in ITU-R S. 1062 with the ATM current and proposed QoS requirements of ITU-T

1.356, B-ISDNATM Layer Cell Transfer Performance. Notice that there is potential for an order of magnitude or

more improvement required for the QoS requirements for stringent telecommunication applications such as

compressed data and video. Also note that as the QoS requirements increase, the link availability decreases.

1 E+O0

1.E-01

1 .E-02

1E..03

E

1 .E-04

I_.

I .E-05

0

:E

1E-06

1.E-07

1 E-08

1 E-09

1.E-10 1 .E-_

ATM CER, CLR Results for 45 Mbps IDR Modem (w/o R-S)

Comparlmon with 5.1062 and proposed 1.356

°More stin_.ent values are for turther study in current draft of 1.356

"1

/

i Sli_BERII i /

-" /

i •/'_ -- •-- CER I

___., ....

_ cuR" I

1, E.-08 1 .E.-07 1 .E-05 1 .E-05 1 .E-04 1 .E-03 1 E-O;'

BER

FIGURE 3

Recent experimental result using MPEG-2 compressed digital video indicate that the MPEG-2 decoders

temporarily loose synchronization at CLRs and CERs in the order of 1.0E-7 and 4.0E-7 respectively [2]. As an

example, the movie, "Apollo 13," was video taped to get some idea of the long term Quality of Service

requirements. An EF-Data SDM 9000 45 Mbps QPSK modem was configured to utilize 3/4 convolutional

coding (without the Reed-Solomon code activated) at an Eb/No of 8.0 dB which corresponds to a 2.0E-8 BER,

5.0E-7 Cell Error Ratio, and 4.0E-8 Cell Loss Ratio. In 2 hours and 20 minutes, there were at least 12

identifiable errors, block errors or loss of synchronization. Video was also recorded using combined 3_

convolutional coding and Reed-Solomon block coding resulting in a BER, CLR, and CER of approximately

1.0E-8, 4.5E-7 and 5.5E-7 respectively. Block errors and synchronization losses averaged approximately four to

*As agreed to at the ITU-T Study Group 13 Rapporteur's meeting held in Lannion, France, 13-17 November

1995.

NASA/TM--97-206297 3
sixperhalfhour.Thus,onewouldexpecttheCLRandCERrequirement tobeatleast1.0E-8and1.0E-7or

betterdependingonthecustomer'sacceptancelevel.

Traffic Management and Congestion Control

The SN&AB is funding Sterling Software Inc. to investigate ATM traffic management and congestion control

issues related to satellite systems. The principle investigator is Dr. Raj Join at Ohio State University [3].

Recent work has addressed Optimization of performance of TCP/IP over satellite ATM networks and switch

algorithms. Of particular interest has been Dr. Jain and Seong-Cheol Kim's work regarding segment-by-segment

congestion control know as "virtual source/virtual destination" (VS/VD). This control scheme is advantageous to

long delay links as - in the limit - each segment may be independently controlled [Figure 4].

ExplicitForward Congestion Inf0rmation_

Resource Management

Explieit Forward Congestion Inf0rmation_

Resource Management

FIGURE 4 - Segment-by-Segment Control

Additional work is being performed by Dr. Jain and his colleagues regarding Internet protocols over ATM over

satellite including TCP (Transmission Control Protocol) over UBR (Unavailable Bit Rate) and TCP over ABR

(Available Bit Rate). The key parameters being studied are the performance with limited buffers, and buffer

requirements for zero loss. Various algorithms are also under investigation such as Early Packet Discard, Fast

Retransmit Recovery and fair buffer allocation.

Routing

Route selection in the emerging ATM networks is based on the capabilities of the "Private Network-Network

Interface Specification Version 1.0" (PNNI 1.0) [4] and its forthcoming antecedents. The protocol defines the

distribution of topology information between switches and clusters of switches. This information is used to

compute paths through the network. A second protocol within PNNI is defined for signalling, that is message

flows, used to establish point-to-point and point-to-multipoint connections across the ATM network. This

signalling protocol is based on the ATM Forum UNI signalling, with mechanisms added to support source

routing, crankback, and alternate routing of call setup requests in case of connection setup failure.

The interconnection of satellite networks with ATM networks will require that the satellite networks participate

in the routing protocols. At this time NASA Lewis Research Center is planning a set of experiments [5] to be

completed in the summer of 1997 that will:

1. Establish a baseline network for studying the issues related to the signalling operation of a hybrid

satellite/terrestrial network.

2. Determine signalling parameters issues related to supporting "normal" network and user services that are

required in a hybrid satellite/terrestrial network.

3. Collect data from the baseline network under various ope(ating conditions including that of when a terrestrial

or satellite link is abnormally disabled (network survivability).

I-Iandover

Handover is the mechanism that supports the mobility of a network device, its network links, and its active

connections. The ATM specification for handover is currently in development in the ATM Forum Wireless

ATM working group [6]. There are three types of handover that are required to be designed for in satellite

networks:

NASA/TM--97-206297 4
1.End-user tosatellite

2. satellitetosatellite

3. satellitetonetworkaccesspoint

It is anticipatedthatthethreetypesof handoverswill operateindependently of oneanotherin orderto be

compatiblewiththehandoverprotocolenvisionedin theATM Forum.A keyelementof thehandover

mechanismis thereroutingof activecircuits. Thiselementalsodependson thePNNIprotocolfor

implementation. WithintheATMForumothermechanisms suchasFaultTolerance[7][8],andConnection

Modify[9]willalsorelyonthereroutemechanism. All ofthesemechanisms arecriticaltotheoptimaloperation

ofahybridsatellite-terrestrial network.

AcontributiontotheATMForumhasbeenmadebyNASALewisResearchCentertodefineagenericreroute

protocolthatis applicableto themechanisms of Handover,FaultTolerance, andConnectionModify[10.]

Additional contributionsonthesubjectwillbesubmittedbyNASAtotheATMForum.

Signaling

NASAforeseessomeissuesregardingnetworkmanagement adcontrolsignalingforsomesatellitearchitectures

includingLEOandMEOnetworks, andTMDAandMulti-beamsystems.Signalingmustbemaintainedinorder

tomaintainroutingstatusandcongestionnotification.Thismustbedesignedintothenetworksandsatellitesparticularlyforonboardprocessingsatellites.

Multieasting

NASAforeseesmulticastingasanareathatsatelliteshaveatremendous advantageinoverterrestrial networksin

thattheroutingtreestructureshouldbesignificantlysmallerutilizinga satellitenetworkfor broadcast and

multicast servicessuchasthe"pushservices,"applicationsthatpushinformationtointegratedusers-alsoknown

asnetcastingapplications. Thisareamustbeexploitedforsatellitesto beaviablecompetitorintheInternet

environment. Muchworkisbeingdonebytheterrestrial telecommunication industryregardingIPmulticasting,

ATMmulticastingandintegratingIPmulticastingwithATM. Thismustbefollowedcloselytoensuresatellite

friendlyimplementations.

Security

Securityis alwaysanissuefornetworkingandmoresoforATMbecauseof its structure.SinceATMwas

developedforeasyof switchingviatheheader, it iseasyto filteroffmessages bymonitoringtheheader.For

free-spacecommunications, thisisadifficultproblem.Theheadercannotbescrambledormodifiedforsecurity

astheswitching,routing,andheadererrorcontrolwill becompromised. Therefore, ATMsecuritymustake

placeinthepayload.Avarietyofgroupsareworkingthisproblem.TheUSmilitaryisamajorfundingsource

forsuchactivityastheywishtoutilizeATMtechnologywithintheirnetworks.

CommonAir Interface

A newgenerationof satellitesystemsarebeingdesigned,evelopedanddeployedfor arangeof services--

fixed,mobileandbroadcast.Examplesof suchsystemsincludegeosynchronous, lowearthorbitandmedium

earthorbitmobilesystems, aswellasKa-bandgeosynchronous andlowearthorbitsystemsfor highspeed

services.Anumberof thesesystemsareenvisionedto beregionalandglobal.Asetofcommonairinterface

standardsforthesesystemswillbebeneficial fromthepointofviewofinteroperability.

A standardssubcommitteeproject,CommonAir InterfaceforSatelliteSystems, hasbeenapprovedby the

Communications andInteroperabilitySectionof theTelecommunications IndustryAssociation's (TIA)Satellite

Communications Division[11]. Theworkwill becarriedoutin anewworkinggroupto beformedunder

standardssubcommittee TR-34.1.Thesatellitesystemsto beconsideredwill rangefromsatellitepersonal

communications sytemstobroadbandsatellitesystems.

TR-34.1isalsoinvolvedinotherareasofcommunications andinteroperability. Itsspecificworkinggroupsare

WirelessAsynchronous TransferMode(ATM),InternetoverSatellite,ATMSpeech, ATMTrafficManagement

andCongestionControl,ATMQualityofServiceandHybridReferenceModels.

NASA/TM--97-206297 5
4. TRANSPORT LAYER ISSUES

Satellite research in the Internet protocol stack known as TCP/IP has tended to focus on the Transmission

Control Protocol (TCP) since it is the basis for World Wide Web traffic and is the standard protocol for reliable

transport. There are several approaches to dealing with TCP over satellite links including spoofing, protocol

conversion, caching, and TCP extensions [12]. We have concentrated on TCP extensions as being the most

general solution to interoperability. There are three main issues which need to be addressed in using TCP over

satellite: 1) Use of Long, Fat Network (LFN) extensions, and 2) Inefficiencies in the slow start and congestion

avoidance algorithms, and 3) Loss recovery.

The issue of the use of LFN extensions is basically one of implementation. The LFN extensions were designed to

allow TCP steady-state operation over high bandwidth-delay product connections and have existed (and been

discussed and slightly modified) for many years [13, 14]. They are an optional TCP extension and are not

necessarily available in a particular TCP implementation. The product of the round trip time for a connection

and its data rate is known as the bandwidth-delay product. A high bandwidth-delay product connection can result

from a very high data rate just as well as from a high delay, thus LFN extensions are needed for high data rate

terrestrial connections as well as for satellite connections.

A key part of the LFN extensions is the window scaling option or "large windows." TCP is a sliding window

protocol and the size of the window determines the maximum throughput of a TCP connection. The size of the

window should be equal to the bandwidth-delay product for full utilization of a channel in steady-state.

Without the LFN extensions, the maximum window size for TCP is 64 KB. The typical default value for the

window size in a particular implementation might be 8 KB. Window scaling allows as much as a 1 GB window

if both ends of the connection support the option.

Table 1 shows a comparison of bandwidth*delay products for examples of terrestrial and satellite delays. The

LFN extensions are not even needed for a typical low rate satellite connection and it is not until an individual

satellite connection gets up to around 1 Mbps that they are needed. Table 2 shows that even for short terrestrial

links, LFN extensions will be necessary as data rates increase. The 10 Mbps entry of 52 ms means that a

terrestrial cross-country link of 10 Mbps with a round trip time of 80 ms (>52 ms) will require LFN extensions to

utilize the full bandwidth of the link. Thus, as data rates increase everywhere, LFN extensions will have to

become more prevalent in TCP implementations.

TABLE 1 - Comparison of 80 ms and 560 ms bandwidth-delay products

RATE RTT B*D LFN

(bps_ _sec) _b_es)

33600 0.08 336 N

3360(3 0.56 2352 N

12800(3 0.08 1280 N

12800(3 0.56 8960 N

1550000 0.08 15500 N

1550000 0.56 108500 Y

10000000 0.08 100000 Y

10000000 0.56 700000 Y

1.55E+08 0.08 1550000 Y

1.55E+08 0.56 1.1E+07 Y

NASA/TM---97-206297 6
TABLE2-RoundtriptimestomatchthemaximumTCPwindowsizewithoutscalingoption

RATE RTTforB*D=64KB

Cb0s) _sec)

33600 15.604

128000 4.096

1550000 0.338

10000000 0.052

1.55E+08 0.003

6.22E+08 0.001

In addition to scaled windows, LFN extensions provide a timestamps option which is used for the Round Trip

Time Measurement and for Protect Against Wrapped Sequences algorithms. A selective acknowledgment

(SACK) option was defined as part of the original LFN extensions, but was split out to be technically addressed

as a separate topic and has only recently been published [15]. SACK could be used to improve TCP performance

over noisy links [ 16]. Although the SACK RFC describes how to implement selective acknowledgments, it does

not describe a retransmit strategy beyond existing congestion avoidance, so further research is needed for SACK

implementation.

The second issue is a research problem as opposed to an implementation problem and is concerned with the

dynamic behavior of TCP as it starts up a connection or deals with lost packets. With a long round trip time, the

slow start and congestion avoidance algorithms built into TCP to combat network congestion operate very

slowly. Slow start is used to ramp a TCP connection up onto the network when it is first established, and it is

also sometimes used (followed by an even slower algorithm called congestion avoidance) when a packet is lost

indicating congestion.

It can be shown [17] that the time spent in slow start from the beginning of a connection to steady-state in the

absence of losses is

t = R log2 (W) (1)

where t is the time spent in slow start, R is the round trip time, and W is the size of the window in packets (with

delayed acknowledgments, which are commonly used, the time will be longer than the value given by equation

1). The key thing to recognize from equation 1 is that the time spent in slow start is proportional to the round trip

time. For a geosynchronous satellite connection of, say, 560 ms round trip time, the slow start time compared to

a terrestrial cross-country connection of, say, 80 ms will be seven times as long. Similarly, time spent in

congestion avoidance over that same geosynchronous satellite link will be around seven times longer than that

terrestrial cross-country connection (starting from similar initial conditions).

For small file transfers, such as are now typical on the World Wide Web (WWW) [ 18], a connection will not get

out of the slow start phase before all the data has been sent. With the move to HTTP 1.1, the Web will move to

larger file transfers which may allow connections to get through slow start or at least use more of the available

bandwidth. Efforts are also underway to speed up slow start. One proposal being put before the IETF is for a

larger initial window of up to 4KB. The results of testing and simulation thus far indicates that this modification

will not hurt the network [ 19]. This will shave a couple of round trip times off a transfer.

Studies have shown that multiple connections (in the range of 4 to 8) allow an application to utilize more of the

available bandwidth [20], but this is not looked upon by the networking community in general as a "fair"

solution. Multiple connections can be thought of as allowing more aggressive start-up and less aggressive

congestion control [21]. Some WWW browsers currently allow multiple connections to be established.

A problem for noisy links with TCP's congestion handling algorithms is that TCP uses packet loss as an

indication of congestion and throttles back on the transmission rate when a packet is lost. The best way to avoid

the inefficiencies of congestion avoidance is not to needlessly invoke it. SACK could help in lost packet cases,

NASA/TM--97-206297 7
butfurtherresearchisneededtodevelopways of discriminating between packet loss and congestion. TCP works

best over low error rate links like fiber. A case can even be made that error rates on high data rate/long delay

links should be even lower than those on fiber for TCP to work efficiently [22].

5. CONCLUDING REMARKS

Although this paper has outlined the major issues concerning seamless interoperability between satellite and

terrestrial networks in the emerging GII it in fact only touches the first layer of complexity that needs to be

addressed. Every year additional telecommunication services are envisioned that are by and large incompatible

with the unique transmission characteristics of satellite. The role of satellites in the emerging global information

infrastructure is critical to provide information services to anyone, anywhere, at anytime which makes the issue of

interoperability between satellite and terrestrial networks critical. To address the interoperability issue it is

important that satellite and terrestrial telecommunication standards for the GI evolve simultaneously. The

product of this involvement will lead to enhanced end-to-end global information services in the developing global

information market.

6. REFERENCES

1. Ivancic, W. and Bobinsky, E: "ATM QoS at 45 Mbps using a Satellite Emulator: Laboratory

Measurements", GlobeCom 97 Proceedings, pg. 532.1, November 1997.

2. Ivancic, W. and Frantz, B., Spells, M.: "MPEG-2 Over ATM Over Satellite QoS Experiments: Laboratory

Tests," to be published in September 1997.

3. www.cis.ohio-state.edu, August 1997.

4. ATM Forum PNNI Working Group, af-pnni-0055.0000, "Private Network-Network Interface Specification

Version 1.0" (PNNI 1.0), March 1996.

5. ATM Forum WATM Working Group, ATM Forum LTD-WATM-01.02, "Living List Document of

Wireless ATM Working Group," April 1997.

6. vonDeak, T.: ATDnet-ACTS-MAGIC Experiment (#118-k): "Assessment of Hybrid Satellite/Terrestrial

Networks on ATM Signalling," <http://www.cgrg.ohio-state.edu/other/actsgsn/aamll8-k.html>, January,

1997.

7. Hitoshi M., et al.: "Proposal for a Working Document for Fault Tolerance in PNNI," ATM Forum

Contribution 97-0321, April 1997.

8. Kushi, K. M. and Spiegel, E. M.: "Signalling Procedures for Fault Tolerant Connections," ATM Forum

Contribution 97-0391R1, April 1997.

9. Wiles, M. and Cherukuri, R.: "Connection Modify," ATM Forum Contribution 97-0321, April 1997.

l 0. vonDeak, T.: "Generic Reroute Mechanism," ATM Forum 97-0651, July 1997.

11. Peterson, J.: '_l'IA Press Release on New Work - Common Air Interface for Satellite", Memorandum to

Committee T1, Telecommunications Industry Association, July 3l, 1997.

12. Yongguang, Z., De Lucia; D., Ryu; B., and Dao, S. K.: "Satellite Communications in the Global Internet -

Issues, Pitfalls, and Potential," INET'97.

13. Jacobson, V. and Braden, R.: "TCP Extensions for Long-Delay Paths," RFC 1072, October 1988.

14. Jacobson, V., Braden, R., and D. Borman: "TCP Extensions for High Performance," draft-ieff-tcplw-highperformance-00.txt, February 1997.

15. Mathis, M., Mahdavi, J., Floyd, S., and Romanow, A.: "TCP Selective Acknowledgment Options," RFC

2018, October 1996.

16. Allman, M., Hayes, C., Kruse, H., and Ostermann, S.: "TCP Performance over Satellite Links." Proceedings

of the Fifth International Conference on Telecommunications Systems, Nashville, TN, March, 1997.

17. Jacobson, V.: "Congestion Avoidance and Control," Computer Communication Review, vol. 18, no. 4, pp.

314-329, August 1988.

18. Mah, B. A.: "An Empirical Model of HTTP Network Traffic," Proceeding of INFOCOM'97, in Kobe,

Japan, April 7-11, 1997.

19. Allman, M., Hayes, C., and Ostermann, S.: "An Evaluation of TCP Slow Start Modifications," Submitted to

Computer Communication Review.

20. Allman, M., Kruse, H., and Ostermann, S.: "An Application-Level Solution to TCP's Satellite

Inefficiencies," Proceedings of the First International Workshop on Satellite-Based Information Services

(WOSBIS), Rye, New York, November 13, 1996.

21. Allman, M: "Improving TCP Performance Over Satellite Channels," Master's Thesis, Ohio University, June

1997.

22. Partridge, C. and Shepard, T. J.: "TCP/IP Performance over Satellite Links," Submitted to IEEE Network.

NASA/TM--97-206297 8

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December 1997 Technical Memorandum

4. TITLE AND SUBTITLE 5. FUNDING NUMBERS

Enhancing End-to-End Performance of Information Services Over Ka-Band

Global Satellite Networks

e. AUTHOR(S)

Kul B. Bhasin, Daniel R. Glover, William D. Ivancic, and Thomas C. vonDeak

7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES)

National Aeronautics and Space Administration

Lewis Research Center

Cleveland, Ohio 44135-3191

9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES)

National Aeronautics and Space Administration

Washington, DC 20546-0001

WU--632-50-5A-00

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REPORT NUMBER

E - 10994

10. SPONSORING/MONITORING

AGENCY REPORT NUMBER

NASA TM--97-206297

11. SUPPLEMENTARY NOTES

Prepared for the Third Ka Band Utilization Conference sponsored by the IIC-Instituto Internazionale delle Comunicazioni,

Sorrento, Italy, September 15-18, 1997. Responsible person, William D. Ivancic, organization code 5610,

(216) 433-3494.

12a. DISTRIBUTION/AVAILABILITY STATEMENT

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Subject Category: 17 Distribution: Nonstandard

This publication is available from the NASA Center for AeroSpace Information, (301) 621-0390.

12b. DISTRIBUTION CODE

13. ABSTRACT (Maximum 200 words)

The Internet has been growing at a rapid rate as the key medium to provide information services such as e-mall, WWW

and multimedia etc., however its global reach is limited. Ka-band communication satellite networks are being developed

to increase the accessibility of information services via the Internet at global scale. There is need to assess satellite

networks in their ability to provide these services and interconnect seamlessly with existing and proposed terrestrial

telecommunication networks. In this paper the significant issues and requirements in providing end-to-end high performance for the delivery of information services over satellite networks based on various layers in the OSI reference model

are identified. Key experiments have been performed to evaluate the performance of digital video and Intemet over

satellite-like testbeds. The results of the early developments in ATM and TCP protocols over satellite networks are

summarized.

14. SUBJECT TERMS

Ka-band; Networking; TCP/IP; ATM

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18. SECURITY CLASSIFICATION

OF THIS PAGE

Unclassified

19. SECURITYCLASSIFICATION

OF ABSTRACT

Unclassified

15. NUMBER OF PAGES

14

16. PRICE CODE

A03

20. LIMITATION OF ABSTRACT

Standard Form 298 (Rev. 2-89)

Prescribed by ANSI Std. Z39-18

298-102