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Questions and Answers
What is a key characteristic of the routing mechanism borrowed from DSR?
What is a key characteristic of the routing mechanism borrowed from DSR?
What typically causes TCP throughput degradation in ad hoc networks?
What typically causes TCP throughput degradation in ad hoc networks?
What is one proposed enhancement approach to improve TCP performance in wireless networks?
What is one proposed enhancement approach to improve TCP performance in wireless networks?
What issue arises from the misinterpretation of packet loss in ad hoc networks?
What issue arises from the misinterpretation of packet loss in ad hoc networks?
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How does the use of proxy nodes enhance TCP performance in wireless networks?
How does the use of proxy nodes enhance TCP performance in wireless networks?
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What type of routing protocol is DSDV?
What type of routing protocol is DSDV?
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Which protocol requires periodic updates of routing information?
Which protocol requires periodic updates of routing information?
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Which statement about DSR is true?
Which statement about DSR is true?
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In terms of routing overhead, how does DSR compare to DSDV?
In terms of routing overhead, how does DSR compare to DSDV?
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What is a primary characteristic of the AODV routing protocol?
What is a primary characteristic of the AODV routing protocol?
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How does the average end-to-end delay of DSDV compare to that of DSR?
How does the average end-to-end delay of DSDV compare to that of DSR?
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Which is a key disadvantage common to both DSDV and DSR?
Which is a key disadvantage common to both DSDV and DSR?
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What does the source node do in DSR during the routing process?
What does the source node do in DSR during the routing process?
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Study Notes
Wireless Mobile & Multimedia Networking - Ad-hoc Networks 4
- Course code: 7COM1076
- Lecturer: Dr Tazeen Syed
- Email: [email protected]
Outline
- Performance comparison of DSDV & DSR
- Ad-hoc On-Demand Distance Vector (AODV)
- TCP Performance in ad hoc networks
- Enhancement Approaches
DSDV Table-Driven Routing Protocols
- Table-driven / proactive routing protocol
- Enhanced version of Bellman-Ford routing protocol
- Routing information must be updated periodically
- Brute force approach
- Each node maintains routing information for all known destinations
- Connectivity information needs periodical update throughout the whole network
- Maintains routes which aren't used
Dynamic Source Vector (DSR) Routing Protocol
- On-demand / reactive routing protocol
- Execute the path-finding process and exchange routing information only when a path is required from a source to a destination
- No periodic routing updates or routing information exchange
- Source routing
- Route discovery is initialized by the source node
- The source node determines the complete sequence of nodes to forward a packet
Performance Comparison
- Routing set-up delay:
- DSDV - short
- DSR - long
- Reason for the difference: [no specific reason given in the slides]
- Routing overhead:
- DSDV - heavy
- DSR - not as heavy as DSDV
- Reason for the difference: [no specific reason given in the slides]
- Route length:
- DSDV - short
- DSR - long
- Reason for the difference: [no specific reason given in the slides]
- Average end-to-end delay:
- DSDV - low
- DSR - high
- Reason for the difference: [no specific reason given in the slides]
- Suitability for high mobility ad hoc networks: neither protocol is ideal
Ad hoc On-Demand Distance Vector (AODV)
- Ad hoc on-demand distance vector (AODV) routing protocol
- Target for large ad hoc networks (10,000 to 100,000 nodes)
- Combination of DSR and DSDV
- Borrows basic on-demand mechanism of Route Discovery and Route Maintenance from DSR
- Uses hop-by-hop routing, sequence numbers, and periodic beacons from DSDV
- Maintains only active routes
TCP Performance in Ad Hoc Networks
- TCP throughput degradation in ad hoc networks
- Adaptation of TCP to congestion causes problems in the wireless domain
- High packet loss and variable latency in wireless domains
- TCP may respond with slow start
- Reduced bandwidth utilization due to retransmissions of lost packets
- Misinterpretation of packet loss
- Frequent path breaks
- Effect of path length
- Uni-directional path
Enhancement Approaches
- Getting feedback from the network to TCP source
- Split approach – Long TCP connection separated into small TCP connections, separate congestion control and end-to-end reliability
- Proxy nodes buffer packets from source, send local acknowledgements to the source
- Enhanced throughput
- Improved fairness
References
- "Ad Hoc Wireless Networks, architectures and protocols" by C. Siva Ram Murthy and B. S. Manoj (1st edition)
- Sections 7.5.2 and 9.5.2 [of the cited book]
- J. Broch, D.A. Maltz, B.D. Johnson, Y. Hu and J. Jetcheva, "A Performance comparison of multi-hop wireless ad hoc routing protocols," Proceedings of the 4th annual ACM/IEEE International conference on Mobile Computing and Networking (1998), pages 85–97.
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Description
This quiz focuses on ad-hoc networks, examining the performance of DSDV and DSR protocols, as well as the AODV routing protocol. It also explores TCP performance in ad-hoc settings and various enhancement approaches. Test your understanding of these concepts and their applications in wireless mobile networking.
