Hierarchical Proportional Routing
We have shown that proportional routing schemes alleviate congestion in the network by distributing load among multiple “good” paths instead of overloading a single “best” path. However these schemes assume that each router in the network is aware of the topology and the state of the whole network. This is referred to as flat routing and under flat routing, each router participates in link state updates and maintains detailed information about the entire network. This introduces significant burden on every router and as the size of the network grows, the overhead at each router increases tremendously. To provide a scalable solution, hierarchical routing is suggested [43, 4] as an alternative to flat routing. To make the proportional routing schemes scale well to large networks we need to extend them to provide hierarchical routing.
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