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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 l.jpg

TLMN 625 Spring 03Class 9

High Speed Networks

FRAME RELAY

ATM

SONET(WDM)


Preliminaries service interfaces and delivery l.jpg
PreliminariesService Interfaces and Delivery

  • DS1 - 1.544 Mbps

  • DS3 - 45 Mbps

  • OC3 - 155 Mbps

  • OC12 - 622 Mbps

  • OC refers to optical

14


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What is Broadband?

1.5 Megabits/second

and greater


Broadband services l.jpg
Broadband Services

  • Circuit switched (leased) T1,T3

  • Frame Relay

  • Gigabit Ethernet

  • ATM




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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


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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)


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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




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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.


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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


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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



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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



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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.


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FRAD in ACTION

Port to

Network

FRAD

Router

Packets


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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


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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


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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?


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


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Web site for next figure (FECN, BECN)

http://www.visualnetworks.com/products/frame/uptroubsh.htm

http://www.visualnetworks.com/products/frame/vuppvc.htm


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Frame Relay (FECN, BECN)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


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ATM Characteristics (FECN, BECN)

  • 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


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cells (FECN, BECN)

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


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Choice of ATM (FECN, BECN)

  • 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


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Voice (FECN, BECN)

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


Slide32 l.jpg

48 Bytes (FECN, BECN)

5 Bytes

Header

Payload

Figure 9.1


Slide33 l.jpg

ATM Cell (FECN, BECN)

Virtual Circuits (VC), Virtual Paths (VP)


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ATM SERVICE CLASSES (FECN, BECN)


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VOICE OVER ATM Before IP (FECN, BECN)

  • 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


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Cell Tax (FECN, BECN)


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SONET (FECN, BECN)


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SONET/ATM/Traffic (FECN, BECN)


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SONET / ATM (FECN, BECN)Slide 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


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SONET/ ATM (FECN, BECN)Slide 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


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Questions (Frame Relay): (FECN, BECN)

  • 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?


Questions atm l.jpg
Questions (ATM) (FECN, BECN)

  • Which type of traffic is isochronous?

    • Video,data, images, LANs

  • Packetized voice uses which type of application service?

    • CBR,VBR,UBR,ABR