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Chapter 18 Frame Relay

Chapter 18 Frame Relay. Homework: p 452 38, 39, 51,52,53. Chapter 18 Frame Relay. Frame Relay Layers Frame Relay Operation Implementation. Frame Relay. A packet switching WAN technology developed to provide more efficient transmission than X.25. Frame Relay (continued).

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Chapter 18 Frame Relay

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  1. Chapter 18Frame Relay • Homework: • p 452 38, 39, 51,52,53

  2. Chapter 18Frame Relay • Frame Relay Layers • Frame Relay Operation • Implementation

  3. Frame Relay • A packet switching WAN technology developed to provide more efficient transmission than X.25.

  4. Frame Relay (continued) • Frame Relay operates in two layers. • Frame Relay has less overhead than X.25. • Frame Relay does not implement error and flow control. • Frame relay supports variable data transmission rate, Suitable for bursty traffic. • Frame Relay operates at speeds of 1.544 Mbps and 44.376 Mbps

  5. Frame Relay (continued) • Disadvantages of Frame Relay • Frame relay supports variable data transmission rate, not suitable for delay sensitive data • Frame Relay allows variable frame size of up to 9000 bytes • Congestion control must be implemented (variable data rate) • Not high enough data transmission rate

  6. X.25 Traffic

  7. Frame Relay Traffic

  8. Frame Relay Layers

  9. Frame Relay Operation • Frame Relay operates on two principals: • If there is any problem with the frame, discard it. • The end user systems are responsible for error recovery.

  10. Frame Relay Operation (continued) • Users are connected to a Frame Relay interface (DCE) through a router or a bridge (DTE).

  11. Frame Relay Operation (continued) • Frame Relay provides two types of connections : • Permanent virtual connections (PVC) • Switched virtual connections (SVC) • Virtual circuit address are used and are implemented at the data link layer. • Each circuit is identified by data link connection identifier (DLCI).

  12. Congestion • The condition of a network when there is not enough bandwidth to support the current traffic load. • Effect of congestion: • Decreases the throughout • Increases delay

  13. Congestion Control • Implicit • Explicit (used by Frame relay) • Backward explicit congestion notification (BECN) • Forward explicit congestion notification (FECN)

  14. Frame Relay Frame

  15. Congestion Control • Backward explicit congestion notification (BECN) • Switch can use the response frame to notify the sender. • Or • Switch can use a predefined connection to send a notification to sender.

  16. Congestion Control • Forward explicit congestion notification (FECN) • The receiver is notified of congestion. • The receiver can delay the acknowledgment therefore, forcing the sender to slow down.

  17. Leaky Bucket Algorithm

  18. Access Rate • The Access Rateof a connection is the maximum amount of bandwidth a customer will have available at any given time. • If user is connected to frame network over T1 then CIR is 1.54

  19. Committed Burst Size (Bc) • The Bcof a connection is the minimum amount of bandwidth a customer will have available over a period of time • Ex: 4k for 4 sec

  20. Committed Information Rate (CIR) • The CIRof a connection is the minimum amount of bandwidth a customer will have available at any given time.

  21. CIR • Bc =maximum committed burst amount of data that network agrees to transmit under normal condition, over time T. • Be =(excess burst size)maximum amount of data in excess of Bc that network will attempt to transmit under normal condition, over time T.(uncommitted) • Data in excess of Bc + Bewill be dropped

  22. Frame Relay Network

  23. Frame Relay Address

  24. Frame Relay Address

  25. Frame Relay Address

  26. Frame Relay Address

  27. Frame Relay Implementation Non Frame Relay networks connected to FR by means of Frame Relay assembler/ disassembler (FRAD)

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