Network topology Definition Advantages and Disadvantages Bus based network All processors access a common bus for exchanging data, The distance between any two nodes is 1 in a bus. The bus also provides a convenient broadcast media. The bandwidth of the shared bus is a major bottleneck as the number of nodes increases. The demand of a bus bandwidth can be reduced by making the majority of the data accessed is local to the node and remote data is accessed by the bus. Crossbars A crossbar network uses an p×m grid of switches to connect p inputs to m outputs in a non-blocking The cost of crossbar network at which p processors connected to b databank increases as the number of processing nodes increases , this leads to memory access blocking. Multistage Networks This network consists of multiple stages; these stages connect number of inputs/outputs. Accessing a memory location may block other accesses to another memory location by another processor, this is called blocking multistage network Completely Connected Network Each processor is connected to every other processor. The hardware complexity is not realizable for large values of p. This network is ideal in the sense that a node sends a message to other node directly in a single step. Star Connected Network Every node is connected only to a common node at the center; Distance between any pair of nodes is 1. The central node becomes a bottleneck. Linear Arrays In a linear array, each node has two neighbors, one to its left and one to its right. If the nodes at either end are connected, we refer to it as a 1-D torus or a ring. Meshes, and k-d Meshes A generalization to 2 dimensions has nodes with 4 neighbors, to the north, south, east, and west called 2 dimensional mesh. A further generalization to d dimensions has nodes with 2d neighbors. Hypercubes The distance between any two nodes is at most log p. Each node has log p neighbors. The distance between two nodes is given by the number of bit positions at which the two nodes differ. Tree-Based Networks The distance between any two nodes is no more than 2logp. Links higher up the tree potentially carry more traffic than those at the lower levels. For this reason, a variant called a fat-tree, fattens the links as we go up the tree. How to send a message in a tree based network? To route a message in a tree the source node sends the message up the tree until reaches the root of the smallest sub tree containing both the source and destination.

Network topology Definition Advantages and … topology Definition Advantages and Disadvantages Bus based network All processors access a common bus for exchanging data, The distance

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Network topology Definition Advantages and Disadvantages

Bus based network

All processors access a common bus for exchanging data,The distance between any two nodes is 1 in a bus. The busalso provides a convenient broadcast media.

The bandwidth of the shared bus is a major bottleneck as thenumber of nodes increases.The demand of a bus bandwidth can be reduced by making themajority of the data accessed is local to the node and remote data isaccessed by the bus.

CrossbarsA crossbar network uses an p×m grid of switches to connectp inputs to m outputs in a non-blocking

The cost of crossbar network at which p processors connected to bdatabank increases as the number of processing nodes increases ,this leads to memory access blocking.

Multistage NetworksThis network consists ofmultiple stages; these stagesconnect number of inputs/outputs.

Accessing a memory location may block other accesses to anothermemory location by another processor, this is called blockingmultistage network

CompletelyConnected Network

Each processor is connected to every other processor. The hardware complexity is not realizable for large values of p. Thisnetwork is ideal in the sense that a node sends a message to othernode directly in a single step.

Star ConnectedNetwork

Every node is connected only to a common node at thecenter; Distance between any pair of nodes is 1.

The central node becomes a bottleneck.

Linear ArraysIn a linear array, each node has two neighbors, one to itsleft and one to its right. If the nodes at either end areconnected, we refer to it as a 1-D torus or a ring.

Meshes, and k-dMeshes

A generalization to 2 dimensions has nodes with 4neighbors, to the north, south, east, and west called 2dimensional mesh.A further generalization to d dimensions has nodes with 2dneighbors.

Hypercubes

The distance between any two nodes is at most log p.Each node has log p neighbors.The distance between two nodes is given by the number ofbit positions at which the two nodes differ.

Tree-Based Networks

The distance between any two nodes is no more than2logp.

Links higher up the tree potentially carry more traffic than those atthe lower levels.For this reason, a variant called a fat-tree, fattens the links as we goup the tree.How to send a message in a tree based network?To route a message in a tree the source node sends the message upthe tree until reaches the root of the smallest sub tree containingboth the source and destination.

Page 2: Network topology Definition Advantages and … topology Definition Advantages and Disadvantages Bus based network All processors access a common bus for exchanging data, The distance

Classification of interconnection networks: (a) a static network; and (b) a dynamic network.

Page 3: Network topology Definition Advantages and … topology Definition Advantages and Disadvantages Bus based network All processors access a common bus for exchanging data, The distance

Bus-based interconnects (a) with no local caches; (b) with local memory/caches.

A completely non-blocking crossbar network connecting p processors to b memory banks.

Page 4: Network topology Definition Advantages and … topology Definition Advantages and Disadvantages Bus based network All processors access a common bus for exchanging data, The distance

The schematic of a typical multistage interconnection network.

Page 5: Network topology Definition Advantages and … topology Definition Advantages and Disadvantages Bus based network All processors access a common bus for exchanging data, The distance

(a) A completely-connected network of eight nodes; (b) a Star connected network of nine nodes.

Linear arrays: (a) with no wraparound links; (b) with wraparound link.

Two and three dimensional meshes: (a) 2-D mesh with no wraparound; (b) 2-D mesh with wraparound link (2-D torus); and (c) a 3-D meshwith no wraparound.