1 / 42

Frame Relay

Frame Relay. Nirmala Shenoy Information Technology Department Rochester Institute of Technology. Frame Relay. Purpose Faster transmission Virtual circuit technology Data rates up to 2.048 Kbps to the end user Network Data rates – 44.376 Mbps – T3 lines

enan
Download Presentation

Frame Relay

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. Frame Relay Nirmala Shenoy Information Technology Department Rochester Institute of Technology updated 12/2001

  2. Frame Relay • Purpose • Faster transmission • Virtual circuit technology • Data rates up to 2.048 Kbps to the end user • Network Data rates – 44.376 Mbps – T3 lines • Assumes smart end systems & reliable media • No error & flow control in the network • High data rates at low costs updated 12/2001

  3. Frame Relay • Purpose • Replacement for a number of leased T1 lines • Virtual private networks • Lower costs for similar resources • Wide Area coverage – interconnect LANs • Ideally suited to bursty traffic updated 12/2001

  4. Frame Relay • Purpose • Bursty traffic updated 12/2001

  5. Frame Relay • Advantages • High data rates & access rates • Lower 2 layers- ideal for backbone networks • Support bursty data • Maximum frame size – 9000 bytes • Less expensive technology • Can be used on lease or on requirement basis updated 12/2001

  6. Frame Relay • Disadvantages • Not high enough data rates • Variable length frames • Not suited to time sensitive applications updated 12/2001

  7. Frame Relay • Topology updated 12/2001

  8. Frame Relay • Topology – virtual circuits updated 12/2001

  9. Frame Relay • Topology – virtual circuits • At the Data link layer • DLCI – Data Link Connection Identifier • PVCs and SVCs • Different connections get different DLCI • Local significance • DLCIs within the network updated 12/2001

  10. Frame Relay • Route table at FR switch updated 12/2001

  11. Frame Relay • Layers • Core data link function – LAPF • Simplified HDLC updated 12/2001

  12. Frame Relay • LAPF – PDU • Flag • Address field • DLCI • C/R (command response bit) not used • EA – extended address bit • FECN • BECN • DE - Drop eligibility bit updated 12/2001

  13. Frame Relay • LAPF – PDU • Information • FCS – Frame check sequence • Flag updated 12/2001

  14. Frame Relay • LAPF – PDU • EA bit – useful for extended address capability • 0 signifies – another address byte to follow • FECN • Forward explicit congestion notification • Warning to receiver of message that there is congestion along the direction of flow updated 12/2001

  15. Frame Relay • LAPF – PDU • BECN – • Notify sender that there is congestion in a direction opposite to the information flow • Use response frames going in reverse direction • Use predefined DLCI connection 1023 • FECN & BECN inform end systems of network congestion updated 12/2001

  16. Frame Relay • FECN & BECN updated 12/2001

  17. Frame Relay • Discard Eligibility bit • This frame can be dropped during congestion • A congestion control mechanism updated 12/2001

  18. Frame Relay • Traffic Control - Attributes • Committed burst size – Bc • Eg 400kbs for 4 seconds • During the 4 second period – max traffic 400kbs • Committed information rate • Average rate • Bc/T (T –predefined period for burst) • CIR = 400/4 = 100kbs/sec updated 12/2001

  19. Frame Relay • Traffic Control - Attributes • Excess burst size – Be • Bits in excess of Bc that can be sent in T • May not be transferred under congestion updated 12/2001

  20. Frame Relay • Traffic Control updated 12/2001

  21. Frame Relay • Traffic Control • Forwarding of traffic • Fast forward • Leaking CIR • Traffic control via leaky bucket updated 12/2001

  22. Frame Relay • Traffic Control • Control of output from leaky bucket – leak rate • Timer (T) and counter for counting bits sent updated 12/2001

  23. Frame Relay • Traffic Control – leaky bucket updated 12/2001

  24. Frame Relay • Traffic Control • Use of the DE bit • User setting • Network setting, based on Bc, Be • May not be used • Policing & Traffic shaping updated 12/2001

  25. Frame Relay • Service class categorization • Be only – all data can be dropped on congestion • CIR and Bc, • User sets DE flag, network will discard these frames under severe network congestion if exceeding Bc • CIR, Bc and Be • Network will tag Be traffic and drop if severe congestion updated 12/2001

  26. Frame Relay • UNI NNI inter-working • ANSI T1.617 updated 12/2001

  27. Frame Relay • UNI NNI inter-working • Messages • SE - Status Enquiry • S – Status • FS – full status on all PVCs • Use of Unnumbered Information frames of HDLC – DLCI = 0 updated 12/2001

  28. Frame Relay • NNI operations • Adding a PVC notification • Detection of PVC deletion • UNI, NNI failures • PVC segment availability • Link verification • Node verification updated 12/2001

  29. Frame Relay • Typical Bellcore PVC service • Exchange Access Frame Relay XA-FR • Defined between LEC (Local Exchange Carrier) and IC(Interchange Carrier) • FR-ICI interface • Consistent service – end-to-end PVC, UNI to UNI updated 12/2001

  30. Frame Relay • XA-FR topology updated 12/2001

  31. Frame Relay • XA-FR • Service parameters at FR-ICI –compliant frames • Performance objective • Delay • Accuracy • Availability updated 12/2001

  32. Frame Relay • XA-FR – delay • FR-UNI access rate • FR-ICI access rate • Frame size • Time the first bit placed on the UNI, till the last bit received at ICI < specified value for 95% of the frames updated 12/2001

  33. Frame Relay • XA-FR – accuracy • Number of errored frames • Number of lost frames • Number of extra frames • Compute • Frames not delivered ratio • Errored frames ratio • Extra frames ratio updated 12/2001

  34. Frame Relay • XA-FR – availability • Scheduled hours of service • Service availability • MTTSR – mean time to service restoration • MTBSO – mean time between service outages • Fraction of time in non-congestion notification state • Mean time between congestion notification st updated 12/2001

  35. Frame Relay • DLCI Values – two octet field • 0 – in channel signaling • 1-15 reserved • 16- 991 – assigned by FR connections • 992-1007 – layer management for bearer service • 1008-1022 – reserved • 1023 – in-channel layer management updated 12/2001

  36. Frame Relay • DLCI Values – • Global addressing – unique destination address • Semi-broadcast – copied to multiple routers updated 12/2001

  37. Frame Relay • Frame Relay SVC operation updated 12/2001

  38. Frame Relay • Frame Relay SVC operation • Set up information • DLCI • An explicit address • Requested end-to-end delay • Max frame size • Requested throughput (incoming & outgoing) • Requested Bc (incoming & outgoing) • Requested Be (incoming & outgoing) updated 12/2001

  39. Frame Relay • Quality of service options • Residual Error rate • Frame related • Switched virtual call establishment delay • Clearing delay • Premature disconnect updated 12/2001

  40. Frame Relay • Features of emerging technologies? • Bursty data & high bit rate (not so high?!) • Quality of Service addressed • Frame based – real time suitability? • Flow control – implicit & minimal • Drop traffic on congestion • Error control – no • Drop traffic on error • Payload integrity management – no • Band width on demand updated 12/2001

  41. Frame Relay • Summary • Extended use of HDLC technology • High speed WAN • Ideal to interconnect high speed LANs • Limitations • Speed • Frame size • Good backbone technology updated 12/2001

  42. Frame Relay • Summary • Lower costs • Operational • End user • Better sharing of resources • New service offering updated 12/2001

More Related