Ad-Hoc Networks 4 PDF

Wireless Mobile & Multimedia Networking 7COM1076 Ad-hoc Networks 4 Dr Tazeen Syed [email protected] Senior Lecturer School of Physics Engineering and Computer Science (SPECS) ...

Wireless Mobile & Multimedia Networking 7COM1076 Ad-hoc Networks 4 Dr Tazeen Syed [email protected] Senior Lecturer School of Physics Engineering and Computer Science (SPECS)  7COM1076 –Wireless Mobile & Multimedia Networking Outline ❑ Performance comparison of DSDV & DSR ❑ Ad-hoc On-Demand Distance Vector (AODV) ❑ TCP Performance in ad hoc networks ❑ Enhancement Approaches  7COM1076 –Wireless Mobile & Multimedia Networking 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 are never used.  7COM1076 –Wireless Mobile & Multimedia Networking 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.  7COM1076 –Wireless Mobile & Multimedia Networking Performance Comparison ▪ Routing set-up delay ▪ DSDV – short ▪ DSR–long ▪ Why? ▪ Routing overhead ▪ DSDV –heavy ▪ DSR –not as heavy as DSDV ▪ Why? ▪ Route length ▪ DSDV –short ▪ DSR –long ▪ Why? ▪ Average end – to -end delay ▪ DSDV –low ▪ DSR – high ▪ Why? Both not suitable for high mobility ad hoc networks  7COM1076 –Wireless Mobile & Multimedia Networking Ad hoc On-Demand Distance Vector (AODV) ▪ Ad hoc on-demand distance vector (AODV) routing protocol. ▪ Target for large ad hoc networks with 10,000 to 100,000 nodes. ▪ Essentially a combination of DSR and DSDV. ▪ Borrow the basic on-demand mechanism of Route Discovery and Route Maintenance from DSR. ▪ Use of hop-by-hop routing, sequence numbers, and periodic beacons from DSDV. ▪ Only active routes are maintained. ▪ What will you predict its performance?  7COM1076 –Wireless Mobile & Multimedia Networking TCP performance in ad hoc networks TCP Throughput Degradation in Ad-hoc Networks Adaptation of TCP to congestion causes a lot of problems in the wireless domain. Wireless domain has high packet loss and variable latency which may cause TCP to respond with slow start. BW utilisation is reduced due to retransmissions of lost packets. ▪ Misinterpretation of packet loss ▪ Frequent path breaks ▪ Effect of path length ▪ Uni-directional path  7COM1076 –Wireless Mobile & Multimedia Networking Enhancement Approaches ▪ Getting feedback from the network to TCP source. ▪ Split approach – Long TCP connection is separated into small TCP connections. Separate congestion control and end-to-end reliability. Proxy nodes will buffer the packets received from source and local acknowledgements are sent to the source. Enhanced throughput Improved Fairness  7COM1076 –Wireless Mobile & Multimedia Networking References ❑ Ad Hoc Wireless Networks, architectures and protocols. C. Siva Ram Murthy and B. S. Manoj, 1st edition. ▪ Sections 7.5.2 ▪ Sections 9.5.2 ❑ J. Broch, D.A.Maltz, B.D.Johnson, Y.Hu and J.Jetcheva. A Performance comparison of multi-hop wireless ad hoc routing protocols. In mobicom’98: Proceedings of the 4th annual ACM/IEEE International conference on Mobile Computing and Networking, pages 85-97,1998.  7COM1076 –Wireless Mobile & Multimedia Networking Any Thank you Questions? [email protected]