Satellite networking

TCP Enhancement for Satellite Networks, Using TCP Spoofing as the mitigating

strategy

Student Numbers: John Philip (09063609)Dhanunjay (10006419)Femi Oyewole (09063048)

Under The Guidance Of Professor: Dr Ifiok Otung.

Introduction

To enhance the data throughput of TCP over satellite links, there are strategies proposed in which we are using TCP Spoofing.

Long Feedback Delay

Round Trip Time. (Luis, Datum, & Mark, 1999) (Metz, 1999)

Feedback delay on a GEO satellite channel affect the throughput. (Luis, Datum, & Mark, 1999) (Metz, 1999)

Variable RTTs

It occurs in elliptical satellite orbits and this arise when the ground station is transferred to another satellite in the constellation. (Luis, Datum, & Mark, 1999) (Metz, 1999)

However if not properly performed this satellite link characteristic, Varying RTT could result in packet loss and this may as well cause a reduction in the TCP sender transfer rate. (Luis, Datum, & Mark, 1999) (Metz, 1999)

Transmission Errors

Due to RF interference, atmospheric conditions like noise, weak signals and so on, Satellite channels exhibit signs of high bit-error rate. (Luis, Datum, & Mark, 1999) (Metz, 1999)

TCP sender mis-construement of non delivered and un acknowledged data packet. (Luis, Datum, & Mark, 1999) (Metz, 1999)

Effect will be diminution in CWND and resultant reduction in the overall throughput. (Luis, Datum, & Mark, 1999) (Metz, 1999)

Asymmetric Routing

This occur in two ways and it is due to the expense of the ground station equipment being used to send data to the satellites. (Luis, Datum, & Mark, 1999) (Metz, 1999)

In both cases, a resulting bandwidth asymmetry can effect ACK starvation. Hence, the sender will not be able to feed satellite channel in a steady-order style or manner.

(Luis, Datum, & Mark, 1999) (Metz, 1999)

Large Bandwidth-Delay Product

The delay-bandwidth product (DBP) primarily defines the amount of data that a protocol should have “in flight”.

BDP= Bandwidth x Round Trip Time

Therefore TCP sender and receivers must be very proficient and capable of handling and keeping larger packets (unacknowledged data) in flight.

Hence, BDP is a function of the TCP data transfer window (Luis, Datum, & Mark, 1999) (Metz, 1999) (Yun, Gerard, & Erina, 2002)

TCPAllows us to use an unreliable network in a reliable way. (Luis, Datum,

& Mark, 1999) Ensures flow control of packets of information or data, for which a

smooth to and fro conveyance of data could be established between two ends. (Luis, Datum, & Mark, 1999)

(Source: Johnston, 2006)

TCP Operation

(Source: Gregor,2002)

Operation of TCP (Contd.)

(Source: Zhang, 1996)

Congestion Flow Control

(Source: Gregor,2002)

Spoofing

Literarily, Spoofing can be said to mean an act of deception. It could also be termed as a means or way of imitating an identity of another entity, be it a thing, unit, person, body or creature. (Palter, 2004)

Protocol Spoofing It is used as a data compression technique to improve throughput

levels and thereby increase performance. (Minoli, 2009)

TCP SpoofingThe introduction of the high delay and error prone satellite link into a

network, using protocols primarily designed for terrestrial networks, creates significant performance degradation.

It entails the installation of a spoofing device (say router) on the same side of the satellite link. (Palter, 2004)

TCP Spoofing (Mechanism)

(Source: Zhang, 1996)

Merits of TCP SpoofingSpoofing is beneficial for large file transfers. (Minoli, 2009)

Spoofing increases the data throughput as observed by the data sender, for smaller transfer sizes. (Minoli, 2009)

TCP spoofing breaks the concept of end-to-end semantics because the sender may think a segment has arrived at the destination while it is actually still in transit. This is acceptable in many applications, such as WWW browsing through proxy. (Minoli, 2009)

DemeritsSpoofing creates a second bottleneck, which thereby increases the

number of dropped data packets, which however result in the degradation of the performance. (Minoli, 2009)

If in a heterogeneous network, if the acknowledgement, depending on the routing, shunts the spoofer and gets to the sender, the spoofer then resends the same data again and again, which leads to the collapse of the connection. (Palter, 2004)

Graphical Illustration showing Effect and Performance improvement with TCP Spoofing.

(Minoli, 2009)

Summary and ConclusionApplication of spoofing on TCP is relatively easy to implement in

satellite transmission equipment and it requires no changes to the end systems.

However, spoofing can still cause broken connections when data that has been acknowledged is lost, and it does not improve TCP’s response to bit errors .

Overall, spoofing is not completely safe, since it only provides limited performance benefits, and could be avoided especially if there were a better enhancement option to be considered.

Acronyms

ACK- Acknowledgement BDP- Bandwidth Delay Product CWND- Congestion Window GEO- Geosynchronous Earth Orbit LEO- Low Earth Orbit RTT- Round Trip Time SST- Slow Start Threshold TCP- Transmission Control Protocol

References Gregor, V. B. Network Quality Of Service, 2002. Disponivel em: <

http://www.site.uottawa.ca/~bochmann/CourseModules/NetworkQoS/index.html>. Acesso em: 20 January 2011.

Kenny, S. Q. (2002). Network Protocols and Performance. High Performance Networks , 4-5.

Luis, A. S., Datum, R. G., & Mark, A. (1999, January). Enhancing TCP Over Satellite Channels. Retrieved January 14, 2011, from http://www.faqs.org/rfcs/rfc2488.html

Metz, C. (1999, Jan). Satellite Network Performance. Retrieved Jan 14, 2011 from http://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=00747326&tag=I

Minoli, D. (2009). Satellite Systems Engineering in an IPv6 Environment. Auerbach Publications.

Palter, D. (2004). Satellite and the Internet: Challenges and Solutions. Los Angeles: Satnews Publishers Inc.

Yun, F. H., Gerard, M., & Erina, F. (2002). Service Efficient Network Interconnection Via Satellite. West Sussex: John Wiley & Sons Ltd.

Zhang, Y. (1996). Issues, Pitfalls, and Potential. Satellite Communications in the Global Internet , 6-7.

Thank you