Ad-hoc networking is a rather hot concept in computer communications. This means that there is much research going on and many issues that remains to be solved. Due to limited time, we have only focused on the routing protocols. However there are many issues that could be subject to further studies.
First of all, the simulator environment could be improved. These are just some of the improvements that could be made:
x More routing protocols, for instance TORA, ZRP and CBRP.
x Measurement of computing complexity.
Secondly, there are many issues related to ad-hoc networks that could be subject to further studies:
x Simulations which take unidirectional links into consideration.
x Some sort of analysis of whether many small control messages are more costly to send in terms of resources than fewer large control messages.
Sec [14] authentication headers will be deployed, as well as the necessary key management to distribute keys to the members of the ad-hoc network.
x Quality of Service (QoS): What needs are there for Quality of Service in an ad-hoc network? This is related to what the networks actually will be used for.
x Hand-over of real-time traffic between nodes. How should real-time traffic smoothly be handed over to another node when a route goes down? Should flooding be used before a route is found?
x Multicast: We have only looked at unicast routing. Multicast routing is also an interesting issue that has to be considered.
x Connecting ad-hoc networks to the Internet through access points: How do you connect an ad-hoc network to the Internet? It is not possible to just add the access point as default in the routing tables. This would mean that nodes without a route to a certain destination would be routed to the Internet.
x Mobile IP: Integration of mobile IP into ad-hoc networks.
x Addressing of hosts: How should the hosts in an hoc network be addressed? What happens if one ad-hoc network is partitioned in to two separate networks or two ad-ad-hoc networks are merged into one new larger ad-hoc network?
Figure 28: Different router identification approaches. From left to right: 3a, 3b, 3c.
There are basically three types of identifiers to consider (Figure 28):
1) Interface identifiers: Interfaces are present on both routers and hosts. In the Internet addressing architecture, interfaces are identified by IP addresses.
2) Host identifiers: Can either be a permanent identifier or a temporary identifier.
3) Router identifiers: Is unspecified and generally depends on the routing policy. There are three approaches to MANET router identification and addressing currently being considered:
a) Single IP address (AODV): Identifies a MANET node (both the router and the host) with a single IP address. This approach leaves several issues open:
x How to support sets or subnets of hosts attached to a MANET router?
x How to support the use of multiple wireless interfaces?
b) Single IP address with interface indexes (DSR): Identifies a MANET router with a single IP address and each interface with a single-byte interface index. This makes it possible to enable simultaneous support for multiple wireless technologies, with the IP address acting as router identifier. The problem with this scheme is that it is not IP in the classical sense where interfaces are identified by IP addresses. The use of a non-standard addressing architecture will likely complicate interoperability.
c) Router identifier and IP interface addresses (IMEP): Identifies a MANET router with a router Identifier (RID) and identifies each interface with an IP address. This approach can support sets or subsets of attached hosts and simultaneous use of multiple wireless technologies.
Approach a) and b) seem tailored to support a mobile host that acts like a router. Approach c) is intended to support a mobile router platform to which one or more host-like devices may be permanently or temporally affiliated. These approaches say nothing about how IP addresses are assigned to interfaces (on hosts or routers), or what the RID is and how it is assigned. This is a separate problem, although one which is related to routing.
8 References
[1] Dimitri Bertsekas and Robert Gallager, “Data Networks - 2nd ed”. Prentice Hall, New Jersey, ISBN 0-13-200916-1.
[2] Bommaiah, McAuley and Talpade. AMRoute, “Adhoc Multicast Routing Protocol”, Internet draft, draft-talpade-manet-amroute-00.txt, August 1998. Work in progress.
[3] Josh Broch, David A. Maltz, David B. Johnson, Yih-Chun Hu and Jorjeta Jetcheva, “A performance Comparison of Multi-hop Wireless Ad Hoc Network Routing Protocols”. Mobicom'98, Dallas Texas, 25–30 October, 1998.
[4] Josh Broch, David B. Johnsson, David A. Maltz, “The Dynamic Source Routing Protocol for Mobile Ad Hoc Networks”. Internet Draft, draft-ietf-manet-dsr-00.txt, March 1998. Work in progress.
[5] Scott Corson and Joseph Macker, “ Mobile Ad Hoc Networking (MANET): Routing Protocol Performance Issues and Evaluation Considerations”. Internet-Draft, draft-ietf-manet-issues-01.txt, March 1998. Work in progress.
[6] M.Scott Corson, S. Papademetriou, Philip Papadopolous, Vincent D. Park and Amir Qayyum, “An Internet MANET Encapsulation Protocol (IMEP) Specification”. Internet draft, draft-ietf-manet-imep-spec01.txt, August 1998. Work in progress.
[7] Kevin Fall and Kannan Varadhan, “ns notes and documentation”. The VINT project, UC Berkeley, LBL, USC/ISI, and Xerox PARC, May 1998. Work in progress.
[8] Zygmunt J. Haas and Marc R. Pearlman, “The Zone Routing Protocol (ZRP) for Ad Hoc Networks”, Internet draft, draft-ietf-manet-zone-zrp-01.txt, August 1998. Work in progress.
[9] IEEE Computer Society LAN MAN Standards Committee, “Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications”, IEEE Std 802.11-1997. The Institute of Electrical and Electronics Engineers, New York.
[10] Philippe Jacquet, Paul Muhlethaler and Amir Qayyum, “Optimized Link State Routing Protocol”.
Internet draft, draft-ietf-manet-olsr-00.txt, November 1998. Work in progress.
[11] Mingliang Jiang, Jinyang Li and Yong Chiang Tay, “Cluster Based Routing Protocol (CBRP) Functional specification”. Internet draft, draft-ietf-manet-cbrp-spec-00.txt, August 1998. Work in progress.
[12] David B. Johnson and David A.Maltz, “Dynamic source routing in ad hoc wireless networks”. In Mobile Computing, edited by Tomasz Imielinski and Hank Korth, chapter 5, pages 153-181. Kluwer Academic Publishers.
[13] David B. Johnson and David A. Maltz, “Protocols for adaptive wireless and mobile computing”. In IEEE Personal Communications, 3(1), February 1996.
[14] Stephen Kent and Randall Atkinson, “Security Architecture for the Internet Protocol”, Internet draft, draft-ietf-ipsec-arch-sec-07.txt, July 1998. Work in progress.
[15] Mobile Ad-hoc Networks (MANET). URL: http://www.ietf.org/html.charters/manet-charter.html.
[16] Vincent D. Park and M. Scott Corson, “Temporally-Ordered Routing Algorithm (TORA) Version 1:
Functional specification”. Internet draft, draft-ietf-manet-tora-spec-01.txt, August 1998. Work in progress.
[17] Vincent D. Park and M. Scott Corson, “A performance comparison of the Temporally-Ordered Routing Algorithm and Ideal Link-state routing”. In Proceedings of IEEE Symposium on Computers and Communication ’98, June 1998.
[18] Charles E. Perkins, “Mobility support, Mobile IP and Wireless Channel Support for ns-2”, presentation slides. URL: http://www.svrloc.org/~charliep/mobins2/, (1998-11-29). Work in progress.
[19] Charles E. Perkins, “Ad Hoc On Demand Distance Vector (AODV) Routing”. Internet draft, draft-ietf-manet-aodv-01.txt, August 1998. Work in progress.
[20] Charles E. Perkins, “Ad Hoc On Demand Distance Vector (AODV) Routing”. Internet draft, draft-ietf-manet-aodv-02.txt, November 1998. Work in progress.
[21] Charles E. Perkins, “Mobile Ad Hoc Networking Terminology”. Internet draft, draft-ietf-manet-term-00.txt, October 1997. Work in progress.
[22] Charles E. Perkins and Pravin Bhagwat, “Highly dynamic Destination-Sequenced Distance-Vector routing (DSDV) for mobile computers”. In Proceedings of the SIGCOM '94 Conference on Communications Architecture, protocols and Applications, pages234-244, August 1994. A revised version of the paper is available from http://www.cs.umd.edu/projects/mcml/papers/Sigcomm94.ps.
(1998-11-29)
[23] Larry L. Peterson and Bruce S. Davie, “Computer Networks - A Systems Approach”. San Francisco, Morgan Kaufmann Publishers Inc. ISBN 1-55860-368-9.
[24] Plummer, D., "An Ethernet Address Resolution Protocol - or - Converting Network Protocol Addresses to 48.bit Ethernet Address for Transmission on Ethernet Hardware", RFC-826, MIT, November 1982.
[25] Theodore S. Rappaport, “Wireless Communications: Principles and Practice”. New Jersey, Prentice Hall. ISBN 0-13-375536-3.
[26] Raghupathy Sivakumar, Prasun Sinha and Vaduvur Bharghavan, “Core Extraction Distributed Ad hoc Routing (CEDAR) Specification”, Internet draft, draft-ietf-manet-cedar-spec-00.txt, October 1998.
Work in progress.
[27] Martha Steenstrup, “Routing in communication networks”. New Jersey, Prentice Hall. ISBN 0-13-010752-2.
[28] Jerry Svedlund and Johan Köpman, “Routing protocols in wireless ad-hoc networks - An implementation study”. Uppsala: Uppsala University. Master thesis.
[29] D. L. Tennenhouse and D. Wetherall, “Towards an active network architecture”. In Multimedia Computing and Networking 96, San Jose, CA, Jan 1996.
[30] The CMU Monarch Project. “The CMU Monarch Projects Wireless and Mobility Extensions to ns”.
URL: http://www.monarch.cs.cmu.edu/. (1998-11-29). Work in progress.
Appendix A - Terminology
This appendix contains some terminology [21] that is related to ad-hoc networks.