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TLMN 625 Spring 03 Class 9

TLMN 625 Spring 03 Class 9. High Speed Networks FRAME RELAY ATM SONET(WDM). Preliminaries Service Interfaces and Delivery. DS1 - 1.544 Mbps DS3 - 45 Mbps OC3 - 155 Mbps OC12 - 622 Mbps OC refers to optical. 14. What is Broadband?. 1.5 Megabits/second and greater.

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TLMN 625 Spring 03 Class 9

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  1. TLMN 625 Spring 03Class 9 High Speed Networks FRAME RELAY ATM SONET(WDM)

  2. PreliminariesService Interfaces and Delivery • DS1 - 1.544 Mbps • DS3 - 45 Mbps • OC3 - 155 Mbps • OC12 - 622 Mbps • OC refers to optical 14

  3. What is Broadband? 1.5 Megabits/second and greater

  4. Broadband Services • Circuit switched (leased) T1,T3 • Frame Relay • Gigabit Ethernet • ATM

  5. WAN Interconnections via Leased Lines

  6. WAN Using Frame Relay

  7. What is Frame Relay ? • Public metropolitan and wide-area data service • Employs a shared public Network backbone or can be deployed as a private network • Packet-Switched, Connection-oriented, • Low to high speed: 56/64 Kbps, • 1.536 Mbps (DS1); 45 Mbps (DS3) • The protocol data units at Layer 3 are known as packets, while the Layer 2 protocol data units are called frames 3

  8. FRAME RELAY CHARACTERISTICS • Use: Connecting LANs over Wide Area • Uses Virtual Circuits, Cut- Through switching • Access Method- 56/64 kb/s to 1.544 Mb/s • Committed Service Agreements- • Committed Information Rate (CIR) • Committed Burst Rate (CBR) • Excess Burst Rate (EBR) • Packet size (User data usually 4 KB or less)

  9. Port The Role Of Virtual Circuits (VCs) • Provide Connectivity Between Locations • Each VC is Assigned a Committed Information Rate (CIR) • VC can Burst Above CIR to Handle Data Bursts and Peak Traffic Loads PVC PVC UNI PVC FR Switch

  10. Frame Relay Data Flow

  11. Packet Switched Data Flow X.25

  12. Frame Relay Switching Time A Frame Relay node can start switching traffic out onto a new line as soon as it has read the first two bytes of addressing information at the beginning of the frame. Thus a frame of data can travel end to end, passing through several switches, and still arrive at its destination with only a few bytes delay. These delays are small enough that network latency under Frame Relay is not noticeably different from direct leased line connections.

  13. Addressing • Data Link Connection Identifiers (DLCIs) • Numerical assignments identifying frame relay mapping addresses • Each VC has a unique DLCI (locally significant) • 10 bits are used for DLCIs for a maximum of 210 (1024) addresses per PVC (minimum of 1). DLCIs are provisioned in advance. • Customers are allowed to use 975 DLCI assignments 9

  14. Frame Relay Packet 8 7 6 5 4 3 2 1 8 7 6 5 4 3 2 1 • 10 bits for addressing (1024 DLCIs) • DE - Discard eligible bit 17

  15. Addressing (DLCI) 10

  16. Bursting • The ability to exceed CIR • Allows users to send two times the CIR into the Frame Relay network each one second interval • Frames exceeding CIR are marked discard eligible (DE) • Data over two times CIR is discarded before entering network 14

  17. CIR (Committed Information Rate) Concept

  18. FRAME RELAYPACKET ASSEMBLE/ DISASSEMBLE (FRAD) • Takes packets from other protocols and breaks them into pieces if necessary and then encapsulates the pieces. Reassembles at the other end.

  19. FRAD in ACTION Port to Network FRAD Router Packets

  20. Frame Relay Technology -Network Design Methodology • Collect Network Design Information • Traffic measurements for existing leased lines: point to point measurements - average peak rate, average rate, size of existing circuits • Traffic measurements for existing LANs: Avg. peak rate on LANs; estimate of % to travel over FR network. Calculate traffic for peak periods. • Applications and protocols: Identify delay sensitive applications and protocols and design VC/CIR appropriately 23

  21. Network Design Slide 2 • Choose Network Topology • Star, mesh, or hybrid • Size Access Circuits • Chart out using topology, average peak rates, future traffic growth • Choose CIR for PVCs • Activate Network

  22. Congestion Control Frame Relay • Frame Relay includes two one bit congestion control bits: • FECN -Forward Explicit Congestion Notification • BECN- Backward Explicit Congestion Notification • Use: Some vendors read the bits but do not act on them. Others use the bits to accumulate statistics on the network • Question: Why are they not used?

  23. Backward and Forward Congestion Notification in Frame Relay (FECN, BECN)Congestion occurring at Node B

  24. Web site for next figure http://www.visualnetworks.com/products/frame/uptroubsh.htm http://www.visualnetworks.com/products/frame/vuppvc.htm

  25. Frame Relay Service Agreements • Committed Information Rate (CIR) • Minimum Excess Burst Capacity • Average Round trip Latency • Maximum Round Trip Latency • Percentage of Successfully Delivered Frames • Total Downtime, Restoration Time

  26. ATM Characteristics • Uses 53 Byte fixed length packets • Designed for very fast efficient switching • “Isochronous” transmission, statistical multiplexing • Used for data, voice, multimedia • Is a Switched Virtual Circuit service

  27. cells cells cells … ATM/MULTIMEDIA Voice AAL A/D s1 , s2 … Digital voice samples Video Compression AAL A/D compressed frames picture frames Data AAL Bursty variable-length packets Figure 9.3

  28. Choice of ATM • Multimedia- Data, Voice, Image, Video • High overhead- 10%- • nullified possibly if bandwidth capacity not a limiting factor. Fiber not a problem, wireless a limit. • Good for WAN and networks with • classes of “quality of service” • Typical speeds: 155 Mb/s to 622 Mb/s

  29. Voice Data packets MUX Wasted bandwidth Images TDM 4 3 2 1 4 3 2 1 4 3 2 1 ATM ` 4 3 1 3 2 2 1 Figure 7.37

  30. 48 Bytes 5 Bytes Header Payload Figure 9.1

  31. ATM Cell Virtual Circuits (VC), Virtual Paths (VP)

  32. ATM SERVICE CLASSES

  33. VOICE OVER ATM Before IP • Carrying Voice in Cells • voice digitally encoded at 64Kbps (8-bit samples at 8KHz) [Note design before VOIP] • need full cell's worth of samples before sending cell • example: 1000-byte cells implies 125ms per cell (too long) • smaller latency implies no need for echo cancellors • Settled on compromise of 48 bytes: (32+64)/2

  34. Cell Tax

  35. SONET

  36. SONET/ATM/Traffic

  37. SONET / ATMSlide 1 • SONET is a telecommunications transport protocol based upon frames • SONET multiplexes several low speed links onto one high speed optical link • Standards for ATM over SONET have been defined

  38. SONET/ ATMSlide 2 • ATM can run over optical SONET but can also run over other framing/ transport mediums • SONET can transport ATM but it also possible for a corporation to lease an optical SONET link and transport a protocol other than ATM

  39. Questions (Frame Relay): • Who corrects errors in a frame relay service? • Why is the CIR associated with throughput for frame relay? [i.e. throughput is information bits/sec] • Do carriers sell public frame relay networks or services? What is the difference? • The maximum allowable bursting rate is limited by what parameters?

  40. Questions (ATM) • Which type of traffic is isochronous? • Video,data, images, LANs • Packetized voice uses which type of application service? • CBR,VBR,UBR,ABR

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