INET framework extensions for TCP
Vegas and TCP Westwood
María Fernandez, Carlos T. Calafate,
Juan-Carlos Cano and Pietro Manzoni
http://www.grc.upv.es/
Computer Networks Group
Department of Computing Engineering,
Technical University of Valencia
SPAIN
Outline
2

Evolution of TCP

TCP in INET 2.0 / OMNeT++

Implementation

Simulation results

Conclusions & Future Work
Evolution of TCP
Initial proposal
RFC 675 (1974)
RFC 793 (1981)
General performance
improvements
Van Jacobson
(1988-90)
TCP Vegas (1994)
TCP SACK (1996)
TCP FACK (1996)
Congestion control
(1997)
.
.
.
Multipath (2011)
3
Wireless-specific
solutions
And many more…
I-TCP (1995)
Articles on TCP (WoK)
450
Snoop TCP (1995)
400
350
Mobile-TCP (1997)
300
250
WTCP (1999)
200
150
TCP Santa Cruz (2000)
100
50
TCP Westwood (2002)
TCP Veno (2003)
.
.
.
0
2003 2004 2005 2006 2007 2008 2009 2010 2011 2012
TCP in INET2.0 / OMNeT++
EXISTING…
4
NEW!!!
Implementation
TCP Vegas: cwnd management
TCP Westwood:
BW estimation
5
TCP Vegas: RTT & timeout
Simulation results
10 MiB file request

Evaluated scenario:
100 Mbit/s channel
Adjustable PER & Delay
client
Throughput - Delay
server
(PER = 0.5%)
Throughput - PER
3
(Delay = 1ms)
3.5
TCP Reno
TCP Vegas
TCP Westwood
TCP Reno
TCP Vegas
TCP Westwood
Ideal
3
2.5
2.5
Throughput (MBps)
Throughput (MBps)
2
1.5
1
2
1.5
1
0.5
0.5
0
5
10
15
20
25
30
Delay ms)

Original authors’ data:


6
Vegas improves Reno by about 46%
Westwood improves Reno by about 30%
0
0
0.5
1
1.5
2
2.5
3
PER (Packet Error Rate) (%)
3.5
4
4.5
5
Simulation results

Retransmission behavior
Retransmission Ratio - PER
Timeout Triggered Retransmissions - PER
8
2.5
TCP Reno
TCP Vegas
TCP Westwood
Timeout Triggered Retransmissions (%)
7
TCP Reno
TCP Vegas
TCP Westwood
Retransmission Ratio (%)
6
5
4
3
2
2
1.5
1
0.5
1
0
0
0
0.5
1
1.5
2
2.5
3
PER (Packet Error Rate) (%)
3.5
4
4.5
5
0
0.5
1
1.5
2
2.5
TCP Vegas reduces timeouts by retransmiting more data
 TCP Westwood: Reno efficiency with less less timeouts

7
3
PER (Packet Error Rate) (%)
3.5
4
4.5
5
Conclusions & Future Work
CONCLUSIONS
 The world is wireless!
BUT…
 The standard TCP protocol often offers a reduced performance in wireless
environments

Differences between wired and wireless networks (loss prone)
Although many alternatives to TCP have been proposed, INET 2.0/OMNeT++ only
includes standard TCP
 FIRST STEP: We implemented TCP Vegas and TCP Westwood for INET 2.0
 Experimental results show that:




The performance levels achieved agree with previously published results
Significant benefits are achieved for channels characterized by high losses or high delays (or both)
There is still a great margin for improvement  several research works on the topic
FUTURE WORK
 Develop new TCP variants for INET
 Develop new protocols, comparing against the most effective solutions available
8
Available for download
https://github.com/maferhe2/TCP-Vegas-Westwood
9
Thanks!

10
Questions?