Advanced Computer Architecture - Lecture 42: Networks and clusters. This lecture will cover the following: multistage interconnect network; switch topologies with centralized switch topology, distributed switch topology; cluster; tree network topology; hypercube network topology;...
CS 704 Advanced Computer Architecture Lecture 42 Networks and Clusters (Networks Topology and Internetworking Cont’d) Prof Dr M Ashraf Chughtai Today’s Topics Recap: Switch Topologies Cont’d Centralized Switch Topology Distributed Switch Topology Cluster Summary MAC/VU-Advanced Computer Architecture Lecture 42 Networks and Clusters (2) Recap: Lecture 41 Last time we discussed: The formation of generic interconnection networks and their categorization; The networks communication model, performance, media, software, protocols, subnet and networks topologies Here, we noticed that a generic interconnection network comprises: MAC/VU-Advanced Computer Architecture Lecture 42 Networks and Clusters (2) Recap: Lecture 41 – – – – Computer nodes (host or end system) H/W and S/W interface Links to the interconnection network and Communication subnet The interconnections are classified based on the number of processors or nodes and the distance between them as: – Local Area Network-LAN – Wide Area Network-WAN – System Area Network-SAN MAC/VU-Advanced Computer Architecture Lecture 42 Networks and Clusters (2) Recap: Lecture 41 The interconnect communication model shows that two machines are connected via two unidirectional wires with a FIFO (queue) at the end to hold the data The communication software separates the header and trailer from the message and identifies the request, reply, their acknowledgments and error checking codes The communication protocols suggest the sequence of steps to reliable communication MAC/VU-Advanced Computer Architecture Lecture 42 Networks and Clusters (2) Recap: Lecture 41 The network performance that defines the latency of the message as the sum of the: Sender overhead, time to flight, receiver overhead and the ratio of the message size to the bandwidth We also discussed the properties and performance of interconnect network media or link – the unshielded twisted pair (UTP), coaxial cable and fiber optics MAC/VU-Advanced Computer Architecture Lecture 42 Networks and Clusters (2) Recap: Lecture 41 At the end we discussed the formation of busbased and switch-based communication subnets and introduced the network topologies Here, we observed that the bus-based LAN or Ethernet is the simplest way to interconnect more than two computers sharing a single media However, the interconnect sharing media are challenging as it requires coordination and … MAC/VU-Advanced Computer Architecture Lecture 42 Networks and Clusters (2) Recap: Lecture 41 … arbitration when more than one computer needs the same media simultaneously Alternative to sharing media is to use a switch to provide a dedicated line to all destinations in order; and facilitates point-to-point communication much faster than the shared media A switch provides unidirectional interconnection of input to any one of multiple output terminals MAC/VU-Advanced Computer Architecture Lecture 42 Networks and Clusters (2) Recap: Lecture 41 The switch that facilitates unidirectional interconnection of every processor to all the processors in the network is referred to as the non-blocking switch The Crossbar switch is typical example of nonblocking switch; an is employed in the centralized switching topology Last time we discussed the crossbar topology in detail and noticed that a crossbar uses n2 switches to interconnect n processors in a network MAC/VU-Advanced Computer Architecture Lecture 42 Networks and Clusters (2) Recap: Lecture 41 Here the routing, to establish interconnection between two node at a time, depends on the addressing style i.e., source-based routing where message specifies the path to the destination or destination-based routing where the message simply contains the destination address and a program running in the switch selects the port to take for a given destination MAC/VU-Advanced Computer Architecture Lecture 42 Networks and Clusters (2) 10 K-ary n-cube Network Topology 64 = 43 [4-ary 3-cube) (3 cube is a 16 nodes binary hypercube) MAC/VU-Advanced Computer Architecture Lecture 42 Networks and Clusters (2) 49 Comparing Network Topologies The relative cost and performance of topologies discussed, based on the bisection bandwidth and number of links for 64 nodes network is given in the table here Evaluation Bus Category Ring 2D Torus Fully Connected Performance: Bisection Bandwidth 16 1024 Cost Ports/switch N/A Total Links MAC/VU-Advanced Computer Architecture 64 128 192 2080 Lecture 42 Networks and Clusters (2) 50 Comparing Network Topologies Here, bus is used as the standard reference at unit cost, all transfers are done by taking the time units equal to the number of messages Where as the fully connected network has all nodes at equal distance therefore the number of links and ports per switch are maximum and all transfers are done in parallel taking only unit time The nodes for ring topology are differing distances MAC/VU-Advanced Computer Architecture Lecture 42 Networks and Clusters (2) 51 Comparing Network Topologies Here, bus is used as the standard reference at unit cost, all transfers are done by taking the time units equal to the number of messages Where as the fully connected network has all nodes at equal distance therefore the number of links and ports per switch are maximum and all transfers are done in parallel taking only unit time The nodes for ring topology are differing distances MAC/VU-Advanced Computer Architecture Lecture 42 Networks and Clusters (2) 52 Internetworking Internetworking deals with the communication of computers on independent and incompatible networks reliably and efficiently The software standards are the basic enabling technologies of internetworking (Transmission Control Protocol/Internet Protocol) TCP/IT is the most popular internetworking standard The detailed discussion on Internetworking is beyond the scope of this course MAC/VU-Advanced Computer Architecture Lecture 42 Networks and Clusters (2) 53 Cluster Internetworking deals with the communication of computers on independent and incompatible networks reliably and efficiently The software standards are the basic enabling technologies of internetworking (Transmission Control Protocol/Internet Protocol) TCP/IT is the most popular internetworking standard The detailed discussion on Internetworking is beyond the scope of this course MAC/VU-Advanced Computer Architecture Lecture 42 Networks and Clusters (2) 54 Thanks and Allah Hafiz MAC/VU-Advanced Computer Architecture Lecture 42 Networks and Clusters (2) 55 Summary Today, we discussed an intermediate class of network interconnect which lies between crossbar and bus-based networks, referred to as the Multistage Switch network topology A multistage centralized switch is built from number of large switch boxes, placed at number of stages to interconnect all of the nodes Here, The number of identical stages (Ns) in the network having n nodes and switches in each stage are of size m x m is as given as: MAC/VU-Advanced Computer Architecture Lecture 42 Networks and Clusters (2) 56 Multistage Interconnection Topology MAC/VU-Advanced Computer Architecture Lecture 42 Networks and Clusters (2) 57 Multistage Interconnection Topology And, the number of switches per stage is n/m Thus, the total number of switches used in multistage network of n nodes is n/m log m n i.e., its cost is O(n log n) as compared O(n2 ) for crossbar To understand the design and working of multistage networks, let us consider Omega Network, depicted here, as a typical implementation of multistage network MAC/VU-Advanced Computer Architecture Lecture 42 Networks and Clusters (2) 58 Omega Topology Here, nodes (processors), are addressed using 3bit code and stages of 2x2 crossbar switches 000 001 000 001 010 011 010 011 100 101 100 101 110 111 110 111 number of identical stages [log2 8] = And, switches per stage [n/m] = 8/2 =4 MAC/VU-Advanced Computer Architecture Lecture 42 Networks and Clusters (2) 59 Omega Topology: Multistage Interconnect 000 001 S2 S1 S0 000 001 010 011 010 011 100 101 100 101 110 111 110 111 let us see how the switches at each stage operate to establish connection Note that for the 8-nodes Omega Network the node address is of bits, which is equal to number of stages of the switch MAC/VU-Advanced Computer Architecture Lecture 42 Networks and Clusters (2) 60 Omega Network: Example Here, the 3-bit code a2a1a0 represents stages of the network, as stage S2S1S0, from left to right To find the connection pattern XOR the source and destination, e.g., Src (010) dest (110) then XOR results 100 Cross (S2) Straight (S1) Straight (S0) The switch connections are shown Green Circles MAC/VU-Advanced Computer Architecture Lecture 42 Networks and Clusters (2) 61 Omega Network: Example Thus, the generalized rule to find the switch connection can be summarized as For the stage i IF the source and destination differ in ith bit THEN ELSE connection Cross the switch in the ith stage” Connection is Straight in the ith stage” MAC/VU-Advanced Computer Architecture Lecture 42 Networks and Clusters (2) 62 Characteristics of Omega There exist an single path from source to destination, thus contrary to the non-blocking crossbar network, the omega network is blocking network This is shown here as: - the path 010 110 (red) and - the path 110 100 (blue) have blockage as the S2 for 110 has to wait till 010 has passed otherwise it results in collision MAC/VU-Advanced Computer Architecture Lecture 42 Networks and Clusters (2) 63 ... MAC/VU -Advanced Computer Architecture Lecture 42 Networks and Clusters (2) 25 Parameters of Interconnect Performance Measure MAC/VU -Advanced Computer Architecture Lecture 42 Networks and Clusters. .. MAC/VU -Advanced Computer Architecture Lecture 42 Networks and Clusters (2) 34 Fully Connected: Performance Metrics B C A D MAC/VU -Advanced Computer Architecture Lecture 42 Networks and Clusters. .. MAC/VU -Advanced Computer Architecture Lecture 42 Networks and Clusters (2) 48 K-ary n-cube Network Topology 64 = 43 [4-ary 3-cube) (3 cube is a 16 nodes binary hypercube) MAC/VU -Advanced Computer Architecture