Switching - data communication
- 2. Objectives Switching Space division switching Time division switching Two dimensional switching Circuit switching Packet switching Hybrid switching Timing Network synchronization Routing and Traffic control
- 3. Introduction of Switching By consists of a series of interlinked nodes Data transfer from source to destination
- 4. Switching Technologies Space Division Time Division Two dimensional
- 5. Space-Division Switching Each input takes a different physical path in the switch matrix depending on the output. Provide a separate physical connection between inputs and outputs Transfer signal from a given input to specific output
- 6. Crossbar Switch As digits are dialed, the control element of the switch receives the entire address before processing it.
- 7. Crossbar Switch note: CROSSBAR arises from the use if crossing horizontal and vertical bars to select contacts on the cross-point. Step-by-Step and Crossbar Switching Systems use electro-mechanical components for both switching matrix and control elements.
- 8. Space-Division Switching (advantages and disadvantages) Advantage of space-Division Switch It is instantaneous Disadvantages of space division switch Limitation of this design is the number of crosspoints required With this number of crosspoints is impractical Switch is also inefficient
- 9. Time-Division Switching Uses time-division multiplexing Most popular technology time-slot interchange(TSI) Time-Slot Interchange Connecting four input lines to four output lines Each input line wants to send data to an output line according to the following pattern.
- 10. Time-Division Switching(cont.) The size of each location is the same as the single time slot Combines a TDM multiplexer, a TDM demultiplexer and a TSI TSI consisting of RAM with several memory location Advantage of Time-division switching Needs no crosspoints Disadvantage of Time-division switching Processing each connection creates delays.
- 11. Two Dimensional Switching Combination of space division switching and time division switching. Achieved both time slot interchange and sample switching trunks. Multistage switches of this sort can be designed as time-space- time (TST) switch and space-time-space (STS) switch. Main task is to interconnect an incoming time slot and an outgoing time slot. The unit responsible for this function is group switch.
- 12. Configuration of TST Combination of both Space and time division , we find Time and Space division The advantage of space- division switching is that it is instantaneous The advantage of time- division switching is that it needs no cross points.
- 13. Time-space-time switch combination consists of two time stages and one space stage. 12 inputs and 12 outputs. Instead of one time-division switch, it divides the inputs into three groups and directs them to three timeslot interchanges The last stage is a mirror image of the first stage. The middle stage is a space-division switch (crossbar). Fig: Time-space-time switch or two dimensional switch
- 14. Two Dimensional Switching features Low blocking probability Good implementation advantages More cost effective
- 15. Circuit Switched Networks A set of switches connect by physical links Only one channel dedicated on each link By dividing n channel by using FDM or TDM Dedicated route is established between the source and the destination The entire message is transferred through it. Fig : Circuit Switching
- 16. Circuit Switched Network’s Basic Elements End-Stations (or Terminals) Transmission Media Switching Nodes Phases of a Circuit Switching Circuit Establishment Data Transfer Circuit Disconnect Figure : Circuit Switched Network
- 17. Characteristic of a Circuit-Based Switch Blocking Switching Node -occurs when the switching matrix does not allow some input lines to be connected to output lines. -used on voice system Non-blocking Switching Node -allows all inputs to be connected to all outputs. -used for data connections.
- 18. Advantages and Disadvantages of Circuit Switching Advantages Provides a guaranteed data rate. Data is transmitted without any delay Suitable for long continuous transmission. Disadvantages Cause of dedicated connection ,it can’t transmit any other data ,even channel is free. Dedicated channels require more bandwidth. Establishing a physical link between the two stations is too long.
- 19. Packet Switched Networks A digital network technology that breaks up a message into fixed size packets for transmission Packets of different messages share the communication channel When traversing network switches , routers and other network nodes , packets are buffered and queued , resulting in variable delay and throughput depending on the traffic load in the network Each packet is then transmitted individually and can even follow different routers to its destination
- 20. Pictorial representation of Packet Switched Networks
- 21. Switching Technique of Packet Switched Networks Station breaks long message into packets Packets sent one at a time to the network Packets handled in two ways -Datagram approach -Virtual circuit approach
- 22. Datagram approach In a datagram network, each packet is treated independently of all others. Packets in this approach are referred to as datagram Each packet is separately addressed & treated as independent Figure explains the theory datagram transmission clearly.
- 23. Virtual Circuit approach Virtual circuit network is implemented at the data link layer A circuit switch network is implemented at physical layer Datagram is implemented at network layer A virtual network is a cross between a circuit switched network & a datagram network . It has some characteristics of both.
- 24. Advantages and disadvantages of Packet Switching
- 25. Hybrid Switching This switching format is a hybrid of packet and circuit switching and combines advantages of both. Based on synchronous slots Hybrid Transfer Mode(HTM) -QoS data on slots periodically -BE packets flows through the rest of slots Hybrid Switch - TDM switch + Packet switch
- 27. Advantages & Disadvantage of Hybrid Switching Advantages : Achieves this by taking advantage of the internet and its lower price points . Managed hybrid network can help add bandwidth Alleviate the strain on network capacity Disadvantages : Possible long wait to establish a connection during which no data can be transmitted. More expensive than any other switching techniques. A dedicated path is required for each connection.
- 28. The method used by the data communication system The destination recognizes the start of a data communication Reliably reads the information sent Timing
- 29. 1. Asynchronous Transmission 2. Synchronous Transmission Types of timing schemes
- 30. Send only 1 character at a time Character being the alphabet or number or control character Preceding each character is a start bit Ending each character is 1 or more stop bits Asynchronous Transmission
- 31. Send block of data at a time Each block is preceded by a Start Field Also have an end field Both have a special bit The block can contain up to 64,000 bits Synchronous Transmission
- 32. Known as "networks of coupled dynamical systems“ Allows to coordinate and schedule actions between stations Used in Ethernet and Internet protocol Network Synchronization
- 33. Sender/Receiver Synchronization Receiver/Receiver Synchronization Sender/Receiver(SR) synchronization A sender presents its time signal as a timestamp message to one recipients. Each receiver takes a timestamp at the arrival of this message. The sender and all receivers are synchronize when the steady condition reached. Types of network Synchronization
- 34. Types of network Synchronization (cont.) Receiver/Receiver(RR) synchronization • A sender transmits a broadcast message to numerous receivers. • The recipients timestamp the message upon gathering and exchange this information with different receivers that have taken the same message. • Just the receivers are synchronized and the sender stays unsynchronized
- 35. The purpose of moving packets across a network from one host to destination Performed by dedicated device called routers Each switch has a routing table Routing
- 36. Figure 3:Routing table Routing Table
- 37. Destination device address Neighbor routers for learning about remote network Possible routers to all remote network The best route with the shortest path to each remote network How the routing information can be verified and maintained Routing process
- 38. 1. Static routing 2. Dynamic routing Static Routing Static routing does not involve any change in routing table unless the network administrator changes or modify them manually. Dynamic Routing Dynamic routing is a superior routing technique. It alters the routing information according to the altering network circumstances by examining the arriving routing update message Routing Types
- 39. The process of managing, controlling or reducing the network traffic Particularly internet bandwidth Used by the network administrators Part of bandwidth management Necessary to measure the network traffic to determine the cause of network congestion Necessary for efficient use of datacenter network bandwidth and for maintaining service level agreements. Traffic control
- 40. Any Question?
- 41. THANKS to ALL