1 / 36

Chapter 18. Virtual Circuit Switching: Frame Relay and ATM

Chapter 18. Virtual Circuit Switching: Frame Relay and ATM. 18.1 Virtual Circuit Switching 18.2 Frame Relay 18.3 ATM. Wide area network and switching methods. Circuit switching. Create a real circuit (dedicated line) between source and destination Physical layer technology.

adsila
Download Presentation

Chapter 18. Virtual Circuit Switching: Frame Relay and ATM

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Chapter 18. Virtual Circuit Switching:Frame Relay and ATM 18.1 Virtual Circuit Switching 18.2 Frame Relay 18.3 ATM Computer Networks

  2. Wide area network and switching methods Computer Networks

  3. Circuit switching • Create a real circuit (dedicated line) between source and destination • Physical layer technology Computer Networks

  4. Packet Switching: Datagram Approach • Mostly used in the network layer • Routing (selecting the best route for a packet) is performed at each router Computer Networks

  5. Packet Switching: Virtual Circuit Approach • Packets (frames) are switched along a pre-determined path from source to destination • Data link layer technology Computer Networks

  6. Virtual Circuit Identifier • Virtual circuit network has two addresses • Global address which is unique in the WAN • Virtual circuit identifier which is actually used for data transfer • VCI has switch scope; it is used between two switches • Each switch can use its own unique set of VCIs Computer Networks

  7. VCI Phases • Two approaches for the VC setup • Permanent virtual circuit (PVC) • Switched virtual circuit (SVC): setup, data transfer, teardown Computer Networks

  8. Data Transfer Phase • All switches need to have a table entry for the virtual circuit Computer Networks

  9. Data Transfer using VCI Computer Networks

  10. SVC Setup: Request and Acknowledgment Computer Networks

  11. Frame Relay • Frame Relay is a virtual circuit wide area network • VCIs in Frame Relay are called DLCI(Data Link Connection Identifier)s Computer Networks

  12. Frame Relay Features • Frame relay operates at a higher speed. It can easily be used instead of a mesh of T-1 or T-3 lines • Frame relay operates just the physical and data link layers. It is good as a backbone to provide services to protocols that already have a network layer protocol, such as Internet • It allows bursty data • It allows a frame size of 9000 bytes accommodating all LAN frame sizes • It is less expensive than other traditional WANs • It has error detection at the data link layer only. There is no flow control pr error control Computer Networks

  13. Frame Relay vs. T-line Network Computer Networks

  14. Frame Relay vs. X.25 Network Computer Networks

  15. Frame Relay Layers Computer Networks

  16. Comparing Layers: X.25 & Frame Relay Computer Networks

  17. Frame Relay Frame Computer Networks

  18. Congestion Control • Frame relay requires congestion control, because • Frame Relay does not have a network layer • No flow control at the data link layer • Frame Relay allows the user to transmit bursty data • Congestion avoidance • Two bits in the frame are used • BECN(Backward Explicit Congestion Notification) • FECN(Forward Explicit Congestion Notification) • Discarding: Traffic control Computer Networks

  19. BECN Computer Networks

  20. FECN Computer Networks

  21. Four Cases of Congestion Computer Networks

  22. ATM • Asynchronous Transfer Mode • ATM is the cell relay protocol • ATM uses asynchronous TDM • Cells are transmitted along virtual circuits Computer Networks

  23. Multiplexing using Cells • The variety of packet sizes makes traffic unpredictable • A cell network uses the cell as the basic unit of data exchange • A cell is defined as a small, fixed-sized block of information • Cells are interleaved so that non suffers a long delay • A cell network can handle real-time transmissions • Network operation is more efficient and cheaper Computer Networks

  24. Synchronous vs. Asynchronous TDM Computer Networks

  25. Virtual Connection • Connection between two endpoints is accomplished through • Transmission path (TP) • Virtual path (VP) • Virtual circuit (VC) • A virtual connection is defined by a pair of numbers: VPI and VCI Computer Networks

  26. VPI and VCI: Hierarchical Switching Computer Networks

  27. Identifiers and Cells Computer Networks

  28. VP Switch and VPC Switch Computer Networks

  29. ATM Layers Computer Networks

  30. ATM Layer and Headers Computer Networks

  31. Application Adaptation Layer (AAL) • Convert data from upper-layer into 48-byte data units for the ATM cells • AAL1 – constant bit rate (CBR) video and voice • AAL2 – variable bit rate (VBR) video and voice • AAL3/4 – connection-oriented/connectionless data • AAL5 • Sequencing and error control mechanisms are included in the upper layers • SEAL (Simple and Efficient Adaptation Layer) Computer Networks

  32. AAL1 Computer Networks

  33. AAL2 Computer Networks

  34. AAL3/4 Computer Networks

  35. AAL5 Computer Networks

  36. ATM LAN • Connectionless versus connection-oriented • Physical addresses versus virtual connection identifiers • Multicasting and broadcasting delivery Computer Networks

More Related