Computer network switches & their structures
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This document provides an overview of different types of switches and their structures used in computer networks. It discusses circuit switches, packet switches, and message switches. For structures, it covers space division switches like crossbar and multistage switches. It also discusses time division and time-space-time switches. Specific switch designs covered include Banyan switches, which route packets based on header bits, and Batcher-Banyan switches, which combine a Banyan network with a Batcher network to sort packets and reduce blocking.
![Space Division
• Number of cross points can be calculated as:
N/n (n×k) + k (N/n×N/n) + N/n (k×n)
= 2kN + 2k (N/n) = 2k [N+(N/n)]](https://image.slidesharecdn.com/computernetworkswitchstructure-200706191806/85/Computer-network-switches-their-structures-14-320.jpg)
Computer network switches & their structures
- 1. Computer network SWITCHES AND THEIR STRUCTURES Presented By: Sweta Kumari Barnwal Assistant Professor Arka Jain University Jamshedpur, Jharkhand
- 2. INDEX • Switch • Structure of Switches Circuit Switch Space Switch Time Division Switch Packet Swich Banyan Switch Batcher Banyan Switch Message Switch
- 3. SWITCH It is a mechanism used to interconnect links and form a large network. It is a multi-input, multi-output device that transfers packets from an input to one or more outputs. It is the technique by which nodes control or switch data to transmit it between specific points on a network. Switch is basically of three types: Circuit Switch Packet Switch Message Switch
- 4. SWITCH A switch adds the star topology to the set of possible network structures has several attractive properties: Despite the fact that a switch has a fixed number of data sources and yields, which restrains the quantity of hosts that can be associated with a solitary switch, enormous systems can be worked by interconnecting various switches. We can associate changes to one another and to has utilizing highlight point joins, which ordinarily implies that we can manufacture systems of huge geographic degree. Adding a new host to the network by connecting it to a switch does not necessarily reduce the performance of the network for other hosts already connected.
- 5. CIRCUIT SWITCH In This network, resources (bandwidth) is divided into pieces and bit delay is constant during a connection. The dedicated path/circuit established between sender and receiver provides a guaranteed data rate. Data can be transmitted without any delays once the circuit is established. Telephone system network is the one of example of Circuit switching. • In Circuit switching transmission takes place in three steps: Connection Establishment, Data Transmission and Connection Termination. • Advantages: committed transmission channel is established between the transmitter & receiver, which gives a guaranteed data rate, there is no delay in data flow because of the dedicated transmission path. • Disadvantages: takes long time to establish connection, more bandwidth is required in setting up of dedicated channels, cannot be used to transmit any other data even if the channel is free as the connection is dedicated in circuit switching.
- 7. PACKET SWITCH • A network used for data transmission in which a message is divided into a number of parts (called packets/datagrams) which are sent independently, over whatever route is optimum for each packet, and reassembled at the destination. • Packet Switching works on Store and Forward technique while switching the packets; while forwarding the packet each hop first store that packet then forward. • As we know that the Data is divided into number of small packets to reduce the Total Delay. so, what do you think? Larger the number of packets, smaller the Delay? No, Actually this is not True. • Actually there exist a threshold value at which the Total time decreases and if we increase the number of Packets after that limit, Total time starts increasing. Initially the time is decreasing for some limit and after that time is going to increase. • If the number of Packets are very large then it may take time more than the time taken by the transmission of single packet.
- 9. MESSAGE SWITCH • Before packet switching was introduced, it was a technique developed as an alternate to circuit switching. In message switching, end users communicate by sending and receiving messages that included the entire data to be shared. Messages are the smallest individual unit. Also, the sender and receiver are not directly connected. There are a number of intermediate nodes transfer data and ensure that the message reaches its destination. Message switched data networks are hence called hop-by-hop systems. • It provides two important features: • Store and forward – The intermediate nodes have the responsibility of transferring the entire message to the next node. Therefore each node must have storage capacity. A message will only be delivered if the next hop and the connected link both are available, otherwise it’ll be stored indefinitely. A store-and-forward switch forwards a message only if sufficient resources are available and the next hop is accepting data. This is called the store- and-forward property. • Message delivery – This implies wrapping the entire information in a single message and transferring it from the source to the destination node. Each message must have a header that contains the message routing information, including the source and destination.
- 10. MESSAGE SWITCH
- 11. STRUCTURE
- 12. SPACE DIVISION • In this network path is separated from each other spatially. • It was specially designed for analog networks but currently used in both analog as well as in digital. Cross Bar Switch • It consist n×m input and output lines with a control switch (transistor) controlled by Control Station. • Total Number of Cross Points = n × m • It is inefficient, because in practice less than 25% of the cross points are in used at a particular instant of time. Rest are in idle condition.
- 13. SPACE DIVISION Multistage Switch • In this limitation of cross bar switch has removed out. • Here crossbar switches are combined in several (normally 3) stages. • In a single crossbar switch only one row/column is active at a time> Hence required N×N cross points. • For increasing multipath inside the switch, we have required more number of cross points. • Middle stage cross points can be accessed by multiple cross points available at the entry (1st) & exit (3rd) stages. • In a 3 stage switch the number of cross points are • This number of cross points is much smaller than the number of cross points required in Crossbar switch. • In Single stage switch blockage never occurs, but in this there may be a chance of blocking during heavy traffic = 2kN + k (N/n) 2
- 14. Space Division • Number of cross points can be calculated as: N/n (n×k) + k (N/n×N/n) + N/n (k×n) = 2kN + 2k (N/n) = 2k [N+(N/n)]
- 15. Time Division • On analyzing Multistage switch the minimum number of required cross points are still very huge. • In Time Division structure inside the switch there is a use of Time-Division- Multiplexing (TDM) technique. • The very popular technique is called TSI (Time-slot-Interchange). • It works on Store & Forward technique, Hence delay occurs. • It consist RAM for storing data coming from transmitter and on the basis of decision of control unit sent to the receiver.
- 16. Time Space Time Division • Taking the advantages of space division & time division, there was the new technique had come in light. • It reduces the number of cross points as well as amount of delay. • Multistage switch can be designed as TST Switch.
- 17. Banyan switch The Banyan switch has a switching control built into the switch itself. • It consist a network of 2×2 switch. • Every packet (messages) that comes into the Banyan switch has a header that contains a bit indicating what its destination is (either 0 or 1).The header is usually the first bit of the packet (message) • If the switch reads the bit and it has value 0, it sends the packet to its upper output (which is marked with 0 in the figure) • If the switch reads the bit and it has value 1, it sends the packet to its lower output (which is marked with 1 in the figure). • By connecting these simple Banyan switching elements in series and parallel, it is possible to route packets in more complicated ways depending on the desired routes to establish. • In this structure also problem of blocking is available. • If two packets arrive at the same switch destined for the same output port, a collision will occur. • If all packets are sorted in ascending order upon arrival to a banyan network, no collisions will occur!
- 18. Banyan Switch • Input 1 is sending data (101) to Output 5. • Input 7 is sending data (001) to Output 1.
- 19. Batcher-Banyan Switch • It also consist 2 × 2 switches network. • Attach a batcher network back-to-back with a banyan network. • Every packet (messages) that comes into the Banyan switch will come through Batcher Switch has a header that contains a bit indicating what its destination is (either 0 or 1).The header is usually the first bit of the packet (message) • If the switch reads the bit and it has value 0, it sends the packet to its upper output (which is marked with 0 in the figure) • If the switch reads the bit and it has value 1, it sends the packet to its lower output (which is marked with 1 in the figure). • The Batcher Network uses the properties of a Bitonic Sequence. A sequence of values is called Bitonic if it has a minimum or maximum value surrounded by monotonically ascending or descending values. A completely ordered sequence of values, whether ascending or descending, is Bitonic, as are (trivially) sequences of 2 or fewer values, and (degenerately) completely ordered sequences.
- 21. Thank you