1 CSE 591-S04 (lect 14) Interconnection Networks (notes by Ken Ryu of Arizona State) l Measure –How quickly it can deliver how much of what’s needed to the right place reliably and at good cost and value l Performance Metrics –latency: time for the first bits to arrive –bandwidth: sustained volume of communication –connectivity: how far is the furthest neighbor –hardware cost: can we afford to build this thing? –reliability: can links fail and the system still run? –functionality: “for free” features combining messages fault tolerance l Options –topology –operation mode (synchronous or asynchronous) –switching strategy (circuit, store-and-forward, cut- through) –control strategy (central or distributed)

2 CSE 591-S04 (lect 14) Static Connection Topologies (1) l Topology determines –degree, connections, distance (latency) –routing, cost-performance l Fully Connected Nodes l Star l Tree

3 CSE 591-S04 (lect 14) Static Connection Topologies (2) l Mesh and Ring l Hypercube l Shuffle Exchange

4 CSE 591-S04 (lect 14) Multistage Switching Networks l several stages between source and destination l provide different options in –cost –wires –blocking probability l can be combined into many hybrid options

5 CSE 591-S04 (lect 14) Omega Networks l log n (M) stages for M nodes and n by n cross bars l message block if the required output link is not available

6 CSE 591-S04 (lect 14) Benes networks l additional stages to reduce blocking l can route any disjoint src/dest pairs wo blocking –but must know requests in advance

7 CSE 591-S04 (lect 14) Dynamic (Fat) Trees l Tree: Disproportionate share of traffic l Idea: more resources near the root –Charles Leiserson l Used in CM-5 –More switches near the root – l Theory –Given a size, the best network of the size –Proof : Leiserson’s Fat tree paper

8 CSE 591-S04 (lect 14) Interconnection: Combining l Try to reduce hot spots in a communication network –combine requests for the same location really cache line l Use topology of the network to match comm ops –broadcast flood network - everyone sends to everyone else form a broadcast tree –reduction put arithmetic operations into switches CM-5 fast hardware for and,or,min,max