Capacity Assignment

Once the network topology and the traffic load are known, we can assign link capacities for a specific routing algorithm subject to a total fixed cost. In the case of overlay networks, this refers to dimensioning the access link bandwidth at each MSN site, and interchangeably we call it the link dimensioning process in the later chapters. The capacity assignment in overlay networks differs fundamentally from the conventional approach, where the objective in the latter case is to minimize the average network delay by assigning link capacity in relation to its traffic load [#!kleinrock-net!#]. Here, we want to reduce the likelihood of blocking a session request by assigning more capacity to interface links that have higher traffic load. A session request is blocked if one of the session nodes does not have enough bandwidth left to support the session traffic originating, transiting and terminating at the node. In Chapter , we show that the total capacity required in an overlay network is fixed for a given traffic load and is so regardless of the routing strategies. Therefore, the hard part of the capacity assignment problem is to find the appropriate distribution of this total amount to individual nodes, and this distribution indeed depends entirely on the routing strategy in use.