Lecture 6 7 8

# Lecture 6 7 8 - 1.4 Network Models 1.4 Network Models Now...

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1.4 Network Models usc-ee-den-ee555-200901-silvester section 1.4 1 1.4 Network Models Now suppose we have a communication network of nodes. Each node is a router and has an output buffer for each link leaving that node. Example: 4 node network 1 3 2 4 1 3 2 4 1,2 2,1 4,3 3,4 4,1 1,4 3,1 2,3 1.4 Network Models usc-ee-den-ee555-200901-silvester section 1.4 2 1.4.1 Traffic Matrix Define traffic matrix of flow between source s and destination d : { } sd γ = Γ in packets per second. It is often convenient to represent this with a scale factor outside the matrix so that the elements of the matrix represent the fraction of flow between s and d . For our example, let us assume that the traffic pattern is uniform, i.e. the same amount of traffic flows between any pair of nodes (not allowing a node to talk to itself, even though they sometimes do!) Then, = Γ 0 12 / 1 12 / 1 12 / 1 12 / 1 0 12 / 1 12 / 1 12 / 1 12 / 1 0 12 / 1 12 / 1 12 / 1 12 / 1 0 γ and the total network traffic or load is just γ . 1.4.2 Flow Matrix Based on the routing algorithm (or table or matrix) we can compute the flows (in packets per second) on each link, F . Define sd ij f as the flow on link ( i,j ) due to [ s,d ]

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