ROUTING PROTOCOLS AND CONCEPTS

Routing Protocols and Concepts

Routing Protocols and Concepts

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a) Caching dramatically improved the performance of Array's TMX3000, doubling its transaction rate and halving its latency when compared against the same tests run without caching. NetScaler's performance improved in terms of latency, but the improvement in sessions and HTTP gets per second was negligible. Array's menu of caching options is not as broad as that of NetScaler, which has clearly put a lot of effort into offering a flexible, highly configurable caching scheme that improved performance, albeit not as much as the improvement seen by the Array device when caching is on. F5 needs to weigh the breadth and depth of its forthcoming caching offering if it expects to compete with NetScaler in this focused area.

b) Reactive routing protocols like DSR and AODV do not scale well with the network size. The scalability problem arises from excessive routing overhead, high delay, unreliable data transfer and energy inefficiency. A reactive routing protocol generates a large number of overhead control messages in the network during the route discovery process (Das et al., 2001).

c) Excessive overhead packets cause contention and collision in the wireless medium and occupy a significant portion of useful bandwidth (Tseng et al., 2002). Hence, the performance of a network is adversely affected. Discovering multiple paths by using fewer overhead control messages is one of the objectives of a multipath routing protocol. Another performance problem of a reactive routing protocol is high end-to-end packet delay. This delay arises from an inefficient path selection, unfair load distribution and high overhead.

d) The multipath routing protocols discussed in the previous section have their own advantages and disadvantages. Choosing a suitable multipath routing protocol is a very challenging task and must take into consideration the following factors: (1) the size of a network, (2) the lifetime of a network, (3) environmental conditions and (4) types of applications.

e) The size of a network affects the performance of routing protocol. A small network consisting of less than 100 nodes does not affect the performance of the routing protocol. When a network gets larger, a large number of nodes participate in network operation and generate a large number of overhead packets in the network.

f) In such an environment, there are high interference and noise levels. Reliable multipath routing protocols mentioned in Tsirigos et al. (2001), Yao et al. (2003), Li and Cuthbert (2004), Carthy and Grigoras (2005), Wang et al. (2005), Xue and Nahrstedt (2003), Valera et al. (2003) and Lou (2005) are good candidates for this kind of network. Although reliable data communication is the main design issue of this type of multipath routing, a reliable multipath routing protocol has some problems too.

For example, multipath routing protocols mentioned in Tsirigos et al. (2001), Lou (2005) and Mao et al. (2005) distribute packets among more than one path. These packets travel different paths to a destination. Thus, they take different periods of time to travel from source to ...