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lecture2829atmframerelay-180429142508 (1).pptx
- 1. 18.1 Virtual-Circuit Networks: Frame Relayand ATM Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
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- 3. 8.3 Taxonomy of switchednetworks
- 4. 8.4 CIRCUIT-SWITCHED NETWORKS A circuit-switchednetwork consists of a set of switches connected by physical links. A connection between two stations is a dedicated path made of one or more links. However, each connection uses only one dedicated channel on each link. Each link is normally divided into n channels by using FDM or TDM.
- 5. 8.5 A circuit-switched networkis made of a set of switches connected by physical links, in which each link is divided into n channels. Note
- 6. 8.6 Figure 8.3 Atrivial circuit-switched network
- 7. 8.7 In circuit switching,the resources need to be reserved during the setup phase; the resources remain dedicated for the entire duration of data transfer until the teardown phase. Note
- 8. 8.8 As a trivialexample, let us use a circuit-switched network to connect eight telephones in a small area. Communication is through 4-kHz voice channels. We assume that each link uses FDM to connect a maximum of two voice channels. The bandwidth of each link is then 8 kHz. Figure 8.4 shows the situation. Telephone 1 is connected to telephone 7; 2 to 5; 3 to 8; and 4 to 6. Of course the situation may change when new connections are made. The switch controls the connections. Example 8.1
- 9. 8.9 Figure 8.4 Circuit-switchednetwork used in Example 8.1
- 10. DATAGRAM NETWORKS In datacommunications, we need to send messages from one end system to another. If the message is going to pass through a packet-switched network, it needs to be divided into packets of fixed or variable size. The size of the packet is determined by the network and the governing protocol.
- 11. In a packet-switchednetwork, there is no resource reservation; resources are allocated on demand. Note
- 12. A datagram networkwith four switches (routers)
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- 15. FRAME RELAY Frame Relayis a virtual-circuit wide-area network that was designed in response to demands for a new type of WAN in the late 1980s and early 1990s. Prior to Frame relay, Some organizations were using a virtual circuit network called X.25that performed switching at network layer. X.25 has several drawbacks. 1.X.25 has law 64-kbps data rate. 2.X.25 has extensive flow and error control 3.Originally X.25 was designed for private use.
- 16. 18.16 Architecture : FrameRelay network Frame relay provides permanent virtual circuits and switched virtual circuits.
- 17. VCIs in FrameRelay are called DLCIs. VCI: Virtual circuits Identifier DLCIs :Data link connection Identifier Note Frame Relay is a virtual circuit network. A virtual circuit in a frame relay is identified by a number called a DLCI
- 18. Permanent Versus SwitchedVirtual Circuits A source and a destination may choose to have a permanent virtual circuit (PVC). In this case : The connection setup is simple. An outgoing DLCI is given to the source, and an incoming DLCI is given to the destination. PVC connections have two drawbacks. First, they are costly because two parties pay for the connection all the time even when it is not in use. Second, a connection is created from one source to one single destination. If a source needs connections with several destinations, it needs a PVC for each connection. An alternate approach is the switched virtual circuit (SVC). The SVC creates a temporary, short connection that exists only when data are being transferred between source and destination. An SVC requires establishing and terminating phases
- 19. Frame Relay layers AmericanNational Standards Institute - ANSI Data Link Layer : At the data link layer, Frame Relay uses a simple protocol that does not support flow or error control. It only has an error detection mechanism
- 20. Frame Relay operatesonly at the physical and data link layers. Note
- 21. Figure 18.3 FrameRelay frame
- 22. Frame Relay doesnot provide flow or error control; they must be provided by the upper-layer protocols. Note
- 23. Extended Address :Three address formats
- 24. FRAD FRAD : FrameRelay Assembler / Dissembler
- 25. ATM (Asynchronous TransferMode ) Asynchronous Transfer Mode (ATM) is the cell relay protocol designed by the ATM Forum and adopted by the ITU-T. ATM is a cell switched network.
- 26. 18.26 A cell networkuses the cell as the basic unit of data exchange. A cell is defined as a small, fixed-size block of information. Note
- 27. Figure Architecture ofan ATM network UNI : User to network Interface End points are connected through UNI to the switches in the network. NNI : Network to Network The Switches are connected through NNI.
- 28. Figure TP, VPs,and VCs Connection b/w two end point is accomplished through TP: Transmission Path VP: Virtual Path VC: Virtual Circuits
- 29. Figure Example ofVPs and VCs
- 30. Note that avirtual connection is defined by a pair of numbers: the VPI and the VCI. Note
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- 32. 18.32 Figure Virtual connectionidentifiers in UNIs and NNIs
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- 34. 18.34 Figure Routing witha switch
- 35. 18.35 Figure ATM layers AAL: Application Adaptation Layer
- 36. 18.36 Figure ATM layers AAL: Application Adaptation Layer Physical Layer Like Ethernet and wireless LANs, ATM cells can be carried by any physical layer carrier. ATM Layer The ATM layer provides routing, traffic management, switching, and multiplexing services. Application Adaptation Layer: ATM defines four versions of the AAL: AALl, AAL2, AAL3/4, and AAL5
- 37. 18.37 Figure ATM layersin endpoint devices and switches
- 38. Figure ATM layer TheATM layer provides routing, traffic management, switching, and multiplexing services.
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