Nziga 118
Figure 7.64 CWND – 10Mb – 10ms – DSDV – Tahoe – 80 KM/H
Nziga 119
Figure 7.65 CWND – 10Mb – 5ms – DSDV – Reno – 60 KM/H
Nziga 120
Figure 7.66 CWND – 10Mb – 5ms – DSDV – Reno – 80 KM/H
Nziga 121
Figure 7.67 CWND – 10Mb – 5ms – DSDV – Newreno – 60 KM/H
Nziga 122
Figure 7.68 CWND – 10Mb – 10ms – DSDV – Newreno – 80 KM/H
Nziga 123
Figure 7.69 CWND – 10Mb – 5ms – DSDV – Fack – 60 KM/H
Nziga 124
Figure 7.70 CWND – 10Mb – 10ms – DSDV – Fack – 80 KM/H
Nziga 125
Figure 7.71 CWND – 10Mb – 5ms – DSDV – Sack – 60 KM/H
Nziga 126
Figure 7.72 CWND – 10Mb – 10ms – DSDV – Sack – 80 KM/H
Nziga 127
Figure 7.73 CWND – 10Mb – 2ms – DSDV – Vegas – 60 KM/H
Nziga 128
Figure 7.74 CWND – 10Mb – 10ms – DSDV – Vegas – 80 KM/H
Nziga 129
Let us now focus on Round Trip Time behavior of the communication at different
speeds for the MN. To demonstrate the impact of the MN’s speed on the RTT, we are
inserting below the RTT graphs at the following conditions:
-
10 Mb – 5 ms - 60 KM/H
-
10 Mb – 5 ms - 80 KM/H
For each flavor of the TCP (Figure 7.75 to Figure 7.86). The reader can confirm some
improvements when the MN is moving at the speed of 60 KM/H because the RTT
becomes more stable.
Nziga 130
Figure 7.75 RTT – 10Mb – 5ms – DSDV – Tahoe – 60 KM/H
Nziga 131
Figure 7.76 RTT – 10Mb – 5ms – DSDV – Tahoe – 80 KM/H
Nziga 132
Figure 7.77 RTT – 10Mb – 5ms – DSDV – Reno – 60 KM/H
Nziga 133
Figure 7.78 RTT – 10Mb – 5ms – DSDV – Reno – 80 KM/H
Nziga 134
Figure 7.79 RTT – 10Mb – 5ms – DSDV – Newreno – 60 KM/H
Nziga 135
Figure 7.80 RTT – 10Mb – 5ms – DSDV – Newreno – 80 KM/H
Nziga 136
Figure 7.81 RTT – 10Mb – 5ms – DSDV – Fack – 60 KM/H
Nziga 137
Figure 7.82 RTT – 10Mb – 5ms – DSDV – Fack – 80 KM/H
Nziga 138
Figure 7.83 RTT – 10Mb – 5ms – DSDV – Sack – 60 KM/H
Nziga 139
Figure 7.84 RTT – 10Mb – 5ms – DSDV – Sack – 80 KM/H
Nziga 140
Figure 7.85 RTT – 10Mb – 5ms – DSDV – Vegas – 60 KM/H
Nziga 141
Figure 7.86 RTT – 10Mb – 5ms – DSDV – Vegas – 80 KM/H
Nziga 142
CHAPTER 8
CONCLUSION AND FUTURE WORK
8.1 Conclusion
Wireless networks present a challenge for an efficient data transport. Researchers
have been and are still working in order to find a way to improve the wireless network at
the transport level of the Internet stack. Proposals have been made, but each one of them
presents some limitations:
-
Snoop performs badly when long or frequent disconnections are common.
-
Indirect TCP (I-TCP) violates TCP semantics. The sender can receive an ACK
for a packet even before it gets to the receiver. What if it gets lost after that or
the base station crashes? Moreover, I-TCP does not handle handoff.
-
Explicit Congestion Notification (ECN) and Explicit Lost Notification (ELN)
sound efficient, but are difficult to implement.
-
Fast retransmit accommodates only losses due to the handoff and not those on
wireless link.
-
New Transport Control Protocols for the wireless (Wireless TCP, Wave and
Wait protocol, TCP-Probing) have not been implemented yet.
Mobility changes important assumptions on which the wired network operates,
suffering from delays and losses that are not related to congestion. Reliable transport
protocols that will be able to differentiate motion-related packet losses from congestionrelated packet-losses do not exist yet. The situation suggested an in depth study of the
behavior of all the transport control protocols available on the network simulator NS-2 in
order to understand how they work on the wireless network using a mobile host.
Nziga 143
No such approach has been taken so far. We performed our simulation on a topology
where a correspondent fixed host is communicating with a mobile host.
TCP Tahoe, Reno, Newreno, Vegas, Fack and Sack have been involved, using
different bandwidth values for the communication (1 Mb, 5.5 Mb and 10 Mb). Diverse
values have been considered to simulate the congestion level on the link layer (2 ms, 5
ms and 10 ms). We also considered many speeds for the mobile node, but only three were
kept for our analysis in this thesis (40 KM/H, 60 KM/H and 80 KM/H). Surprisingly, the
results were unpredictable most of the time. This leads us to really understand that there
is a deep difference between the wireless network and the wired network as far as TCP is
concerned.
Researchers cannot presume that the more efficient a TCP flavor is on the wired
network, the least worst it will be on the wireless network. Moreover, we found that it is
not always true contrary to scientists assumptions, that the less congested the connection,
the more packets are received by the mobile node from a fixed correspondent host.
Fortunately, a proposition can emerge from our research in order to maximize a
throughput of a communication on a wireless link with a mobile host. It appears that,
from now until the time a good TCP is found for a wireless network using a mobile node,
three TCP flavors can be used: Tahoe, Fack and Sack. Reno, Newreno and Vegas should
not be selected. When the mobile node decides to perform such communication, its speed
should be set and maintained at 60 KM/H. If the mobile host is moving during the
network communication either at 40 KM/H or at 80 KM/H, it will receive few packets
from its correspondent, and even be disconnected. In a zone where the line is too
Nziga 144
congested, TCP Tahoe and Fack are more advisable. We hope a publication of a paper on
the results of this thesis will prompt another approach in the solution search.
8.2 Future work
In this thesis, we have performed our simulation using one fixed host
communicating with one mobile host. In order to confirm the results of this thesis, the
future work could be to perform the same tests using a mobile host communicating with
another mobile host.
Nziga 145
LIST OF REFERENCES
Allman, Mark, Sally Floyd, and Craig Partridge.1998. “Increasing TCP’s Initial
Window,” Internet Engineering Task Force RFC 2414; available from
http:// www.ietf.org/rfc.html; Internet; accessed 22 February 2003.
Allman, Mark, Vern Paxon, and Richard Stevens. 1999. “TCP Congestion Control,”
Internet Engineering Task Force RFC 2581; available from
http:// www.ietf.org/rfc.html; Internet; accessed 22 February 2003.
Bakre, Ajay, and Rutgers Badrinath. 1995. “I-TCP: Indirect TCP for Mobile hosts,”
Proceedings of the 15th International Conference On Distributed Computing
Systems (ICDCS).
Bakre, Ajay, and Rutgers Badrinath. 1995. “Handoff and system support for Indirect
TCP/IP,” Proceedings of the 2nd USENIX (Unix-like Systems) Symposium Mobile
and Location-Independent Computing.
Balakrishnan, Hari, Srinivasan Seshan, and Randy Katz. 1996. “A comparison of
mechanisms for improving TCP performance over wireless links,” Proceedings
of Association for Computing Machinery (ACM) Special Interest Group on Data
Communication (SIGCOMM). Palo Alto, CA: 256-269.
Balakrishnan, Hari, Srinivasan Seshan, and Randy Katz. 1996. “Improving reliable
transport and handoff performance in cellular wireless networks,” Proceedings of
Association for Computing Machinery (ACM) Special Interest Group on Data
Communication (SIGCOMM).
Balakrishnan, Hari, Srinivasan Seshan, Elan Amir, and Randy Katz. 1995. “Improving
TCP/IP Performance Over Wireless Networks,” Proceedings of Association for
Computing Machinery (ACM) - Mobile Computing and Networking (MobiCom).
Balakrishnan, Hari, Venkata N. Padmanabhan, Srinivasan Seshan, and Randy Katz. 1997.
“A Comparison of Mechanisms for Improving TCP Performance over Wireless
Links,” Proceedings of Institute of Electrical and Electronics Engineers /
Association for Computing - Machinery Transactions Networking.
Braden, Robert, 1989. “Requirements for internet hosts - Communication Layers,”
Internet Engineering Task Force RFC 1122; available from http://
www.ietf.org/rfc.html; Internet; accessed 22 February 2003.
Brakmo, Lawrence S., Sean W. O’Malley, and Larry L. Peterson. 1994. “TCP Vegas:
New Techniques for Congestion Detection Avoidance,” Special Interest Group on
Data Communication.
Nziga 146
Brown, Kevin and Suresh Singh. “M-TCP: TCP for Mobile Cellular Networks,”
Computer Communication Review, 27, no. 5 (1997).
Carceres, Ramon, and Liviu Iftode. “Improving the performance of reliable
transport protocols in mobile computing environments,” Institute of Electrical and
Electronics Engineers Journal on Selected Areas in Communications, 13 (1995).
Chung, Jae, and Mark Claypool. “NS Overview” available from http://
nile.wpi.edu/NS/overview.html; Internet; accessed 22 February 2003.
Deering, Stephen, 1991. “ICMP Router Discovery Messages,” Internet Engineering Task
Force RFC 1256; available from http:// www.ietf.org/rfc.html; Internet; accessed
22 February 2003.
DeSimone, Antonio, Mooi Choo Chuah, and On Ching Yue. 1993. “Throughput
Performance of Transport-Layer Protocols over Wireless LANs,” Proceedings of
Institute of Electrical and Electronics Engineers -Global Telecommunications
(GLOBECOM).
Fall, Kevin and Sally Flyod. 1996. “Simulated –based Comparisons of Tahoe, Reno and
Sack TCP,” Institute of Electrical and Electronics Engineers / Association for
Computing Machinery - Computer Communication Review.
Floyd, Sally, “TCP and Explicit Congestion Notification,” Institute of Electrical
and Electronics Engineers / Association for Computing Machinery - Computer
Communication Review, 24 no. 5 (1994).
Information Sciences Institute (ISI).”The Network Simulator – ns-2,” available from
http:// www.isi.edu/nsnam/ns/; Internet; accessed 22 February 2003.
Jacobson, Van, Robert Braden, and David Borman. 1992. “TCP Extensions for High
Performance,” Internet Engineering Task Force RFC 1323; available from
http:// www.ietf.org/rfc.html; Internet; accessed 22 February 2003.
Jiang, Hai, Shixin Cheng, and Xuan Chen. 2001. “TCP Reno and Vegas in wireless
Ad hoc Networks,” Institute of Electrical and Electronics Engineers International Conference on Communications, 1(2001): pp.132-136.
Karjalainen, Hanna-Maija , 2000. “Ad Hoc Routing- an Overview,” available from
http://www.tcm.hut.fi/Opinnot/Tik110.551/2000/papers/overview.html
Internet; accessed 22 February 2003.
Nziga 147
Kumar, Anurag. 1996. “Comparative Performance Analysis of Versions of TCP in a
Local Network with a Lossy Link,” Proceedings of Institute of Electrical and
Electronics Engineers / Association for Computing Machinery - Transactions of
Networking.
Kurose, James F., and Keith W. Ross. 2001.Computer Networking – A Top-Down
Approach Featuring the Internet, 2nd Edition. Boston: Addison-Wesley.
Lee, William C. Y., 1993. Mobile Communications Design Fundamentals, 2nd Edition.
Indianapolis: John Wiley and Sons.
Mathias, Matt, and Jamshid Mahdavi. 1996a. “TCP Selective Acknowledgement
Options,”Internet Engineering Task Force RFC 2018;available from
http:// www.ietf.org/rfc.html; Internet; accessed 22 February 2003.
Mathias, Matt, and Jamshid Mahdavi.. 1996b. “Forward Acknowledgement: Refining
TCP Congestion Control,” Proceedings of Association for Computing Machinery
Special Interest Group on Data Communication (SIGCOMM).
Mathias, Matt, Jamshid Mahdavi, Sally Floyd, and Allyn Romanow. 1996. “TCP
Selective Acknowledgement Options,” Internet Engineering Task Force RFC
1072; available from http:// www.ietf.org/rfc.html; Internet; accessed
22 February 2003.
Parsa, Christian, and Jose Joaquin Garcia-Luna-Aceves. 1999a. “Improving TCP
Performance over Wireless Networks at the Link Layer,” Proceedings of Mobile
Networks and Applications.
Parsa, Christian, and Jose Joaquin Garcia-Luna-Aceves. 1999b. “Improving TCP
Congestion Control over Internets with Heteregeneous Transmission Media,”
Proceedings of Institute of Electrical and Electronics Engineers –
International Conference on Network Protocols (ICNP).
Paxon, Vern, “Automated packet trace analysis of TCP implementations,”
Proceedings of Applications, Technologies, Architectures, and Protocols for
Computer Communication (Special Interest Group on Data Communication -97),
27(1997): 167-180.
Paxon, Vern, and Mark Allman. 2000. “Computing TCP’s retransmission timer,”
Internet Engineering Task Force RFC 2988; available from
http:// www.ietf.org/rfc.html; Internet; accessed 22 February 2003.
Pentikousis, Kostas, 2000. “TCP in Wired-Cum-Wireless Environments,” Institute of
Electrical and Electronics Engineers - Communications Surveys, Fourth Quarter;
available from http://comsoc.org/pubs/surveys; Internet; accessed 22 February
2003.
Nziga 148
Pentikousis, Kostas, Hussein Badr, and Bilal Kharmah. 2001. “TCP with ECN:
Performance Gains for large TCP transfers,” SBCS-TR-2000/01, Department of
Computer Science, SUNY at Stony Brook.
Perkins, Charles, 1996a. “IP Mobility Support,” Internet Engineering Task Force RFC
2002; available from http:// www.ietf.org/rfc.html; Internet; accessed 22 February
2003.
Perkins, Charles, 1996b. “Mobile Networking with Mobile IP,” available from
http://www.computer.org/internet/v2n1/perkins.htm; Internet; accessed 22
February 2003.
Perkins, Charles, 1996c. “IP Encapsulation Within IP,” Internet Engineering Task Force
RFC 2003; available from http://www.ietf.org/rfc.html; Internet; accessed
22 February 2003.
Perkins, Charles, 1996d. “Minimal Encapsulation Within IP,” Internet Engineering Task
Force RFC 2004; available from http:// www.ietf.org/rfc.html; Internet; accessed
22 February 2003.
Postel, Jon. 1981. “Transmission Control Protocol” Internet Engineering Task Force
RFC 793; available from http:// www.ietf.org/rfc.html; Internet;
accessed 22 February 2003.
Ramakrishnan, Krishna, Sally Floyd, and David Black. 2001.”The Addition of Explicit
Congestion Notification (ECN) to IP,” available from
http://www.ietf.org/internet-drafts/draft-ietf-tsvwg-ecn-03.txt; Internet; accessed
22 February 2003.
Royer, Elizabeth, and Chai Toh. 1999. “A Review of Current Routing Protocols for Ad
Hoc Mobile Wireless Networks,” Proceedings of Institute of Electrical and
Electronics Engineers - Personal Communications.
Sinha, Prasun, Thyagarajan Nandagopal, Narayanan Venkitaraman, Roghupathy
Sivakumar, and Vaduvur Bharghavan. 1999. “WTCP: A Reliable Transport
Protocol for Wireless Wide-Area Networks” Proceedings of
Association for Computing Machine – Mobile Computing and Networking.
Slatimoski, Zoran D., and Aristotel M. Tentov. 2001. “Performance Modeling of Tahoe
and Vegas Implemention of TCP,” available from
http://www.wbmt.tudelft.nl/pto/research/conferences/Proceedings/Sci2001/Papers
pdf/P001603.PDF; Internet; accessed 22 February 2003.
Nziga 149
Slim, J. Hadi and Uddin Ahmed. 2000. “Performance Evaluation of Explicit Congestion
Notification (ECN) in IP Networks,” Internet Engineering Task Force RFC 2884;
available from http:// www.ietf.org/rfc.html; Internet; accessed 22 February 2003.
Tabbane, Sami. 2000. Handbook of Mobile Radio Networks. Norwood: Artech House
Mobile Communications Library.
Tsaoussidis, Vassilis, Hussein Badr, and Rohit Verma. 2000. “Wave and Wait Protocol
(WWP): Low energy, High Throughput for Mobile IP-Devices,” Proceedings of
the 8th Institute of Electrical and Electronics Engineers - Conference Networks
Protocols.
Tsaoussidis, Vassilis, and Hussein Badr. 2000. “TCP-Probing: Toward an error Control
Schema with Energy and Throughput Performance Gains,” Japan: Proceedings
of the 8th Institute of Electrical and Electronics Engineers Conference Network
Protocols.
Wang, Zhen, and Jan Crowcroft. 1991. “A new Congestion Control Scheme: Show Start
and Search (TriS),” Computer Communication Review, 21(1): 32-43.