ATM Network

Bob KlessigBob KlessigDirector, Systems MarketingDirector, Systems MarketingNew Hire Sales TrainingNew Hire Sales Training

R

ATM Data NetworkingATM Data Networking

29 May 1997 2

What You Will Hear (and hopefully What You Will Hear (and hopefully learn)learn)

• What is real and useful about ATM to customers What is real and useful about ATM to customers todaytoday

• The basic concepts of ATM with emphasis on The basic concepts of ATM with emphasis on data networkingdata networking

29 May 1997 3

AgendaAgenda• What’s Hype and What’s HotWhat’s Hype and What’s Hot

• ATM BasicsATM Basics– Executive Overview of ATMExecutive Overview of ATM– Physical LayerPhysical Layer– ATM LayerATM Layer– ATM Adaptation LayerATM Adaptation Layer– Non-UNI InterfacesNon-UNI Interfaces

• LAN EmulationLAN Emulation

• Service InterworkingService Interworking

• Data Networking FuturesData Networking Futures

29 May 1997 4






29 May 1997 5

HYPEHYPE

• Is infinitely scaleableIs infinitely scaleable

• Provides seamless LAN/WAN connectivityProvides seamless LAN/WAN connectivity

• Guarantees Quality of ServiceGuarantees Quality of Service

• Supports all forms of trafficSupports all forms of traffic

• Will be on every new PC motherboard in 18 Will be on every new PC motherboard in 18 months*months*

• Promotes world peacePromotes world peace

ATMATM

*Famous self-proclaimed industry guru in 1993.*Famous self-proclaimed industry guru in 1993.

29 May 1997 6

Data Bandwidth GrowthData Bandwidth Growth

Time

Traf

fic V

olum

e

LocalBackbone

• Growth in overall data trafficGrowth in overall data traffic– More end systemsMore end systems– More powerful end systemsMore powerful end systems– More bandwidth intensive More bandwidth intensive

applicationsapplications– More bandwidth to each end More bandwidth to each end

system, e.g., LAN switchingsystem, e.g., LAN switching

• More traffic hits the More traffic hits the campus/building backbonecampus/building backbone– Centralization of serversCentralization of servers– More non-local server traffic, More non-local server traffic,

e.g., intranet Webe.g., intranet Web

Today’s Hot Market for ATMToday’s Hot Market for ATM

29 May 1997 7

HOTHOT$0

$50

$100

$150

$200

$250

$300

1Q95

2Q95

3Q95

4Q95

1Q96

2Q96

3Q96

4Q96

1Q97

2Q97

3Q97

4Q97

US

Mill

ions

0%

10%

20%

30%

40%

50%

60%

Sequ

entia

l Qua

rter

ly G

row

th

High Speed ATM LAN Switch SalesHigh Speed ATM LAN Switch Sales

Source: Dell’Oro GroupSource: Dell’Oro Group

29 May 1997 8

Scalability: Small NetworkScalability: Small Network

12 Ethernets12 Ethernets

......12 ATM12 ATM

PortsPorts

Switch 2700Switch 2700

CELLplex 7000CELLplex 7000

Single ATM SwitchSingle ATM Switch(144 Ethernet Ports and 4 ATM Ports)(144 Ethernet Ports and 4 ATM Ports)

144

EthernetATM

0500

1000150020002500

$ pe

r Por

t

144

EthernetATM

Switched Ethernet Ports

906

2475

29 May 1997 9

Scalability: Large NetworkScalability: Large NetworkMulti-homed Star TopologyMulti-homed Star Topology

(1536 Switched Ethernet Ports and 64 ATM Ports)(1536 Switched Ethernet Ports and 64 ATM Ports)

8 ATM8 ATMPortsPorts

16 ATM16 ATMSwitchesSwitches 14

4

1536

EthernetATM

0500

1000150020002500

$ pe

r Por

t

144

1536

EthernetATM


1112

906

2475

2475

29 May 1997 10

Scalability: Humongous NetworkScalability: Humongous NetworkStar of Stars TopologyStar of Stars Topology

(23,040 Switched Ethernet Ports - 960 ATM Ports)(23,040 Switched Ethernet Ports - 960 ATM Ports)

1616

1515

1515

144

1536

2304

0

EthernetATM

0500

1000150020002500

$ pe

r Por

t

144

1536

2304

0

EthernetATM


1112

906

1126

2475

2475

2475

29 May 1997 11






29 May 1997 12

ATM Fundamental ConceptATM Fundamental ConceptAll communications are bursty.

VoiceEnergy

Time

SpeakingPause Listening

SpeakingPause

• Therefore, a high performance packet switching Therefore, a high performance packet switching network can carry all communications.network can carry all communications.

Voice example (similar behavior for video and data).

Average 40% activity

29 May 1997 13

ATM Cell (simplified)ATM Cell (simplified)

Header Payload

5 bytes 48 bytes

• Header contains information to allow cell to be Header contains information to allow cell to be forwarded to its destinationforwarded to its destination

29 May 1997 14

ATM VisionATM Vision

• ATM network moves cells (fixed length packets) ATM network moves cells (fixed length packets) with low delay and low delay variationwith low delay and low delay variation

• Devices at ends translate (e.g., segment and Devices at ends translate (e.g., segment and reassemble) between cells and original trafficreassemble) between cells and original traffic

• Communications cannot begin until a connection is Communications cannot begin until a connection is established through the ATM Networkestablished through the ATM Network

The Ultimate Integrated Services NetworkThe Ultimate Integrated Services Network

ATMATMNetworkNetwork

29 May 1997 15

Carrying Packet DataCarrying Packet Data


29 May 1997 16

Carrying a Bit StreamCarrying a Bit Stream

00101011

101010010101110000101011

01011100

10101001

01011100

00101011

110101000011101010010101

10101001


29 May 1997 17

Layered ArchitectureLayered Architecture

• PHY = Physical LayerPHY = Physical Layer• UNI = User Network InterfaceUNI = User Network Interface• AAL = ATM Adaptation LayerAAL = ATM Adaptation Layer• Different AAL protocols for different traffic types (e.g., data, video)Different AAL protocols for different traffic types (e.g., data, video)

AALAAL AALAAL

ATMATM ATMATM

PHYPHY PHYPHY

TerminalTerminal TerminalTerminalATM NetworkATM NetworkUNIUNI UNIUNI

29 May 1997 18

ATM InterfacesATM InterfacesClarkKent

PerryWhite

JimmyOlsen

LoisLane

PrivateUNI

PrivateNNI

PublicUNI

ATMDXI

B-ICI

UNIUNI User Network InterfaceUser Network Interface

FUNIFUNI Frame-based UNIFrame-based UNI

NNINNI Network Node InterfaceNetwork Node Interface

B-ICIB-ICI BISDN Inter-Carrier InterfaceBISDN Inter-Carrier Interface

DXIDXI Data eXchange InterfaceData eXchange Interface

Metropolis Data Services Inc.

Country Wide Carrier Services

PublicNNI

FUNIInspectorHenderson

29 May 1997 19






29 May 1997 20

Physical Layers - Private UNIPhysical Layers - Private UNI

Frame Format Bit Rate/Line Rate MediaCell Stream 25.6 Mbps/32 Mbaud UTP3†

STS-1 51.84 Mbps UTP3FDDI 100 Mbps/125 Mbaud MMF†

STS-3c,STM-1 155.52 Mbps UTP5†

STS-3c,STM-1 155.52 Mbps SMF†,MMF†, CoaxCell Stream 155.52 Mbps/194.4 Mbaud MMF,STP

STS-3c,STM-1 155.52 Mbps UTP3STS-12,STM-4 622.08 Mbps SMF,MMF

STS-48,STM-16 2.4 Gbps SMF***Standardization in progressStandardization in progress††Supported in 3Com productsSupported in 3Com productsSMF - Single Mode FiberSMF - Single Mode FiberMMF - Multi-Mode FiberMMF - Multi-Mode FiberUTP - Unshielded Twisted PairUTP - Unshielded Twisted PairSTP - Shielded Twisted PairSTP - Shielded Twisted Pair

29 May 1997 21

Physical Layers - Public UNIPhysical Layers - Public UNI

Frame Format Bit Rate/Line Rate MediaDS1 1.544 Mbps Twisted PairDS3 44.736 Mbps Coax†

STS-3c,STM-1 155.52 Mbps SMF†

E1 2.048 Mbps Twisted Pair,CoaxE3 34.368 Mbps CoaxJ2 6.312 Mbps Coax

IMA n 1.544 Mbps Twisted Pair†

††Supported in 3Com productsSupported in 3Com productsSMF - Single Mode FiberSMF - Single Mode FiberIMA - Inverse Multiplexing for ATMIMA - Inverse Multiplexing for ATM

29 May 1997 22

Two SublayersTwo Sublayers

Transmission Convergence Sublayer

Physical Layer Medium Dependent Sublayer

PMD:PMD:– Medium, line code, connectorsMedium, line code, connectors– Probably use existing standards and Probably use existing standards and

technologytechnologyTCS:TCS:

– Specific to the PMDSpecific to the PMD– Cell delineationCell delineation– Cell rate decoupling (inserting empty cells Cell rate decoupling (inserting empty cells

during idle periods)during idle periods)

29 May 1997 23

155 Mbps, SONET STS-3c (STM1)155 Mbps, SONET STS-3c (STM1)

9

Rows

270 bytes

9 bytes

Maintenance andoperations

1 SynchronousPayload Envelope

(1 column of overhead)125 sec

• 9 9 260 260 8/125 8/125 sec = 149.76 Mbps payloadsec = 149.76 Mbps payload

• Also known as STM1 (STM = Synchronous Transport Module)Also known as STM1 (STM = Synchronous Transport Module)

. . .

29 May 1997 24

SONET Cell DelineationSONET Cell Delineation

Peek ahead at the cell format

Header Payload

HEC (Header Error Check)

Coverage of the 1 byte HEC

• Receiver locks on 5 byte blocks thatReceiver locks on 5 byte blocks that– Satisfy the HEC calculationSatisfy the HEC calculation– Are separated by 48 bytesAre separated by 48 bytes

• HEC includes coset so that empty cell (first 4 bytes of header = 0) does HEC includes coset so that empty cell (first 4 bytes of header = 0) does not make HEC = 0not make HEC = 0

• Cell payload = 135.63 MbpsCell payload = 135.63 Mbps

29 May 1997 25

DS1 Cell DelineationDS1 Cell Delineation

• (24 bytes x 8 bits/byte)/125 (24 bytes x 8 bits/byte)/125 sec=1.536 Mbps of sec=1.536 Mbps of payloadpayload

• Cell delineation by HEC detection as with Cell delineation by HEC detection as with SONETSONET

• Cell payload=1.536 Mbps x (48/53)=1.391 MbpsCell payload=1.536 Mbps x (48/53)=1.391 Mbps

. . . F B B . . . B F B . . . B F . . .

Framing Bit

125 sec

24 bytes

29 May 1997 26

Inverse Multiplexing for ATM (IMA)Inverse Multiplexing for ATM (IMA)

IMAIMAFrom ATM LayerFrom ATM Layer IMAIMA

ParallelParallelDS1/E1 LinksDS1/E1 Links

To ATM LayerTo ATM Layer

• High speed WAN connectivity without STM1, DS3, or E3High speed WAN connectivity without STM1, DS3, or E3– STM1/DS3/E3 may not be availableSTM1/DS3/E3 may not be available– STM1/DS3/E3 may be very expensiveSTM1/DS3/E3 may be very expensive– STM1/DS3/E3 may be more bandwidth than necessarySTM1/DS3/E3 may be more bandwidth than necessary

• A key feature of for AccessBuilder 9600 and related A key feature of for AccessBuilder 9600 and related productsproducts

29 May 1997 27

Basic Operation of IMABasic Operation of IMA

Link 0Link 0

Link 1Link 1

Link 2Link 2

IMA Frame*IMA Frame*33669912121515171720202323262628283131

447710101313181821212424272729293232

558811111414161619192222252530303333

11

22

nn

o = 0o = 0

o = 5o = 5

o = 9o = 9

o = mo = m

o = 0o = 0

3434

3535

Data cell number n from original cell streamData cell number n from original cell stream

IMA Control Protocol cell with frame offset = mIMA Control Protocol cell with frame offset = m

*IMA Frame can be 32, 64, 128, or 256 cells*IMA Frame can be 32, 64, 128, or 256 cells

29 May 1997 28






29 May 1997 29

ATM UNI CellATM UNI Cell

Generic Flow Control Virtual Path Identifier

Virtual Path Identifier Virtual Channel Identifier

7 6 5 4 3 2 1 0

Virtual ChannelIdentifier

Virtual Channel Identifier

Payload Type Identifier CLP

Header ErrorCheck

Payload(48 bytes)

CLP = Cell Loss Priority

29 May 1997 30

Percent Overhead and Packetization Delayfor 64 Kbps Voice

020406080

100

0 20 40 60 80

Payload (bytes)

% O

verh

aed

0246810

Del

ay (m

s)

Overhead Delay

Packetization Delay Advantage of Packetization Delay Advantage of Small CellsSmall Cells

29 May 1997 31

Queuing Advantage of Small CellsQueuing Advantage of Small Cells

•••

100 byte message100 other active

connections45 Mbps

• Delay and delay Delay and delay variation are small variation are small for small for small messages e.g., a messages e.g., a digitized voice digitized voice samplesampleHigh overhead Wait for other cells

Just fits in one cell

29 May 1997 32

Why 53 Bytes?Why 53 Bytes?

64 + 5 32 + 4

48 + 5

• Compromise reached in CCITT Study Group Compromise reached in CCITT Study Group XVIII in June 1989XVIII in June 1989

29 May 1997 33

Virtual ConnectionsVirtual Connections

37 42

37 78

76

52

22

88

1

2

34

56

In Out Port VPI/VCI Port VPI/VCI Port VPI/VCI

1 0/37 3 0/763 0/76 1 0/37

1 0/42 5 0/52 2 0/37 6 0/22 2 0/78 4 0/88 6 0/36

Connection Table

VirtualVirtualChannelChannelIdentifierIdentifier

36

Bi-directionalBi-directional

Uni-directionalUni-directionalUni-directionalUni-directional

Pt-to-MultipointPt-to-Multipoint

{{

29 May 1997 34

Virtual Paths and Virtual ChannelsVirtual Paths and Virtual Channels

Physical LinkVirtual Path

Virtual Channel

29 May 1997 35

Virtual Paths and Virtual ChannelsVirtual Paths and Virtual Channels

VPI = 1

VPI = 2

VPI = 3

VPI = 4

VPI = 5

VPI = 6

VCI = 31VCI = 32

VCI = 31VCI = 40

VCI = 96VCI = 97

VCI = 55VCI = 57

VCI = 99VCI = 32

VCI = 96VCI = 97

ATM Switch or Network

• Bundles of Virtual Channels are switched via Virtual Bundles of Virtual Channels are switched via Virtual PathsPaths

• Virtual Path service from a carrier allows reconfiguration Virtual Path service from a carrier allows reconfiguration of Virtual Channels without service orders to carrierof Virtual Channels without service orders to carrier

29 May 1997 36

Cell Loss PriorityCell Loss Priority

• Cells with bit set should be discarded before those Cells with bit set should be discarded before those with bit not setwith bit not set

• Can be set by the terminalCan be set by the terminal

• Can be set by ATM switches for internal network Can be set by ATM switches for internal network controlcontrol– Virtual channels/paths with low quality of serviceVirtual channels/paths with low quality of service– Cells that violate traffic management contractCells that violate traffic management contract

• Key to ATM Traffic ManagementKey to ATM Traffic Management

29 May 1997 37

Traffic ManagementTraffic Management

• Problem: Providing quality of serviceProblem: Providing quality of service– How should ATM network resources be allocated to How should ATM network resources be allocated to

ensure good performance including preventing ensure good performance including preventing congestion, e.g., how many virtual channels should be congestion, e.g., how many virtual channels should be assigned to a particular transmission link?assigned to a particular transmission link?

• Solution: Traffic ManagementSolution: Traffic Management– Specify the traffic "contract" on each virtual Specify the traffic "contract" on each virtual

channel/pathchannel/path– Route (including rejecting setup request) each virtual Route (including rejecting setup request) each virtual

channel/path along a path with adequate resources channel/path along a path with adequate resources (Admission Control)(Admission Control)

– Mark (via Cell Loss Priority bit) for loss all cells that Mark (via Cell Loss Priority bit) for loss all cells that violate the contract (Traffic Policing)violate the contract (Traffic Policing)

29 May 1997 38

Generic Cell Rate AlgorithmGeneric Cell Rate Algorithm• For a sequence of cell arrival times, {tFor a sequence of cell arrival times, {tkk}, },

determines which cells conform to the traffic determines which cells conform to the traffic contractcontract

• A counter scheme based on two A counter scheme based on two parameters denoted GCRA(I,L)parameters denoted GCRA(I,L)– Increment parameter: IIncrement parameter: I

» affects cell rateaffects cell rate– Limit parameter: LLimit parameter: L

» affects cell bursts affects cell bursts

• ““Leaky bucket”Leaky bucket”– A cell that would causeA cell that would cause

the bucket to overflow isthe bucket to overflow isnon-conformingnon-conforming

I for each cell arrival

L + I

One unit leak per unit of time

29 May 1997 39

Cell Cell

Smooth TrafficSmooth Traffic

NoCell

Bucket fill just before and just after cell transmit time

GCRA(1.5, .5)

t+t-

1

2

t+t-

1

2

t+t-

1

2

t+t-

1

2

t+t-

1

2

Cell Cell

time

29 May 1997 40

5

10

t+t-

5

10

t+t-

5

10

t+t-

5

10

t+t-

5

10

t+t-

Cell Cell Cell

Bursty TrafficBursty Traffic

NoCell

NoCell

Bucket fill just before and just after cell transmit time

GCRA(4.5, 7)

time

29 May 1997 41

Payload Type IdentifierPayload Type Identifier

• Bit 3: Used to discriminate data cells from Bit 3: Used to discriminate data cells from operation, administration, maintenance cells.operation, administration, maintenance cells.

• Bit 2: Explicit Forward Congestion Indication - Bit 2: Explicit Forward Congestion Indication - used to indicate congestion in data cells (Bit 3 used to indicate congestion in data cells (Bit 3 = 0)= 0)– Used to effect flow control for Available Bit RateUsed to effect flow control for Available Bit Rate

• Bit 1: Carried transparently end-to-end in data Bit 1: Carried transparently end-to-end in data cellscells– Used by AAL5Used by AAL5

29 May 1997 42

ABR Congestion Control OverviewABR Congestion Control Overview

SourceSource DestinationDestination

Forward ResourceForward ResourceManagement CellsManagement Cells

interleaved with datainterleaved with data

Backward Resource Management CellsBackward Resource Management Cellsinterleaved with data, congestion indicatedinterleaved with data, congestion indicated

if incoming EFCI bits are setif incoming EFCI bits are set

Maximum Cell RateMaximum Cell Rate

Minimum Cell RateMinimum Cell Rate

RM cells receivedRM cells receivedwith no congestionwith no congestion

indicatedindicated

RM cells not receivedRM cells not receivedor have congestionor have congestion

indicatedindicated

RM cells receivedRM cells receivedwith no congestionwith no congestion

indicatedindicated

Source BehaviorSource Behavior

EFCI bit set if congestedEFCI bit set if congested

29 May 1997 43

Generic Flow ControlGeneric Flow Control

• Currently undefinedCurrently undefined

• Set to 0000Set to 0000BB

• Proposed future usesProposed future uses– Flow controlFlow control– Shared media multiple access Shared media multiple access

29 May 1997 44

Header Error CheckHeader Error Check

• Header error controlHeader error control– Detection mode: Discard cell when error detectedDetection mode: Discard cell when error detected– Correction mode (optional): Correct 1 bit errors else Correction mode (optional): Correct 1 bit errors else

discard when error detecteddiscard when error detected» Reduced cell loss in face of single bit errorsReduced cell loss in face of single bit errors» Reduced error detection for multiple bit errorsReduced error detection for multiple bit errors

• Cell delineation for SONETCell delineation for SONET

• Recalculated link-by-link because of VPI/VCI value Recalculated link-by-link because of VPI/VCI value changeschanges

29 May 1997 45

Permanent Virtual ConnectionsPermanent Virtual Connections

NetworkManagement

System

• Long setup time (especially with human intervention) means that Long setup time (especially with human intervention) means that connections are left active for long periods of time e.g., days, weeksconnections are left active for long periods of time e.g., days, weeks

• VPI/VCI tables setup in terminals and switchesVPI/VCI tables setup in terminals and switches

VPI/VCI

VPI/VCIVPI/VCIVPI/VCI

29 May 1997 46

Signaling Between Terminal and Signaling Between Terminal and SwitchSwitch

ATM Switch

CallProcessing

Signaling Channel(VPI/VCI = 0/5)

Signaling Channel(VPI/VCI = 0/5)

• Switch and terminal exchange signaling messages Switch and terminal exchange signaling messages using the predefined signaling channel, VPI/VCI = 0/5using the predefined signaling channel, VPI/VCI = 0/5

29 May 1997 47

Setting Up a Call - 1Setting Up a Call - 1

Setup

CallProceeding

A BA wants to communicate with B

• Setup messageSetup message– Call referenceCall reference– Called party addressCalled party address– Calling party addressCalling party address– Traffic characteristicsTraffic characteristics– Quality of serviceQuality of service

• Call proceeding messageCall proceeding message– Call referenceCall reference– VPI/VCIVPI/VCI

29 May 1997 48


Setup

CallProceeding

• Internal network processingInternal network processing– Resource availability checkingResource availability checking– Virtual channel or path routingVirtual channel or path routing– Function of the Network Node Interface (NNI)Function of the Network Node Interface (NNI)

29 May 1997 49


Setup

CallProceeding

Setup

Call Proceeding• Setup messageSetup message

– Call referenceCall reference– Called party addressCalled party address– Calling party addressCalling party address– Traffic characteristicsTraffic characteristics– Quality of serviceQuality of service– VPI/VCIVPI/VCI

• Call ProceedingCall Proceeding– Call referenceCall reference

• Called user deciding to Called user deciding to accept callaccept call

29 May 1997 50


Setup

CallProceeding

Setup

Call Proceeding

Connect Ack

Connect • Connect messageConnect message

– Call referenceCall reference– Indicates call acceptanceIndicates call acceptance

• Connect AcknowledgeConnect Acknowledge– Call referenceCall reference

29 May 1997 51


Setup

CallProceeding

Setup

Call Proceeding

Connect Ack

Connect

Connect Ack

Connect

• Calling party informed that call is available for user information exchangeCalling party informed that call is available for user information exchange

29 May 1997 52

ATM AddressingATM Addressing

• Private networksPrivate networks– 20 bytes20 bytes– Format modeled after OSI NSAP (Network Format modeled after OSI NSAP (Network

Service Access Point)Service Access Point)– Mechanisms for administration existMechanisms for administration exist– Hierarchical structure will facilitate virtual Hierarchical structure will facilitate virtual

connection routing in large ATM networksconnection routing in large ATM networks

• Public networksPublic networks– E.164 numbers (telephone numbers)E.164 numbers (telephone numbers)– Up to 15 digitsUp to 15 digits

29 May 1997 53

Private Address FormatsPrivate Address Formats

3939 DCCDCC Routing FieldsRouting Fields End System IDEnd System IDSSEELL

4747 ICDICD Routing FieldsRouting Fields End System IDEnd System IDSSEELL

4545 E.164 NumberE.164 Number Routing FieldsRouting Fields End System IDEnd System IDSSEELL

Data Country CodeData Country Code

International Code DesignatorInternational Code Designator

E.164 Private AddressE.164 Private Address

29 May 1997 54

Address RegistrationAddress Registration

3939 DCCDCC Routing FieldsRouting Fields End System IDEnd System IDSSEELL

4747 ICDICD Routing FieldsRouting Fields End System IDEnd System IDSSEELL

4545 E.164 NumberE.164 Number Routing FieldsRouting Fields End System IDEnd System IDSSEELL

Supplied bySupplied byATM NetworkATM Network

Supplied bySupplied byTerminalTerminal

• Information exchanged through Integrated Layer Information exchanged through Integrated Layer Management Interface (ILMI) messagesManagement Interface (ILMI) messages

• SEL byte ignored by ATM network and carried transparentlySEL byte ignored by ATM network and carried transparently

29 May 1997 55






29 May 1997 56

AAL 5 for Data NetworkingAAL 5 for Data Networking0 - 65535

Data

Pad

0 - 47 22Len

4 bytes

0

bytes

Not drawn to scale

Error detection fields

0

1

CRC

. . .

Last cell flag

• 48 bytes of data 48 bytes of data per cellper cell

• Uses a PTI bit to Uses a PTI bit to indicate last cellindicate last cell

• Only one packet Only one packet at a time on a at a time on a virtual virtual connectionconnection

48

48

29 May 1997 57






29 May 1997 58

ATM Data eXchange Interface (DXI)ATM Data eXchange Interface (DXI)

• HDLC Frames• HSSI, V.35 Physical

Layer

DTE(e.g., router)

DCE(e.g., CSU/

DSU)

• Cells • DS3, FDDI PHY,

SONET,...

• Segmentation/Reassembly Hardware

• Traffic Shaping Hardware

ATM Switch/Public Carrier ATM

ServiceUNIDXI

Frame Cells

• Provides access to ATM for installed equipmentProvides access to ATM for installed equipment

29 May 1997 59

NNINNI

Virtual Path Identifier

Virtual Path Identifier Virtual Channel Identifier

7 6 5 4 3 2 1 0

Virtual ChannelIdentifier

Virtual Channel Identifier

Payload Type Identifier CLP

Header ErrorCheck

Payload(48 bytes)

CLP = Cell Loss Priority

• Supports 2Supports 21212 Virtual Paths Virtual Paths

• Supports virtual connection routingSupports virtual connection routing– Distribution of topology informationDistribution of topology information– Distribution of resource availability Distribution of resource availability

informationinformation

• Public version being standardized Public version being standardized by ITU Tby ITU T

• Private version being specified by Private version being specified by ATM Forum Technical CommitteeATM Forum Technical Committee

Cell Format

29 May 1997 60

Private Network Node InterfacePrivate Network Node Interface• RoutingRouting

– Exchange of topology and resource informationExchange of topology and resource information– Virtual Route selection for new virtual connections Link Virtual Route selection for new virtual connections Link

State algorithm similar to OSPFState algorithm similar to OSPF

• SignalingSignaling– Admission control for new virtual connectionsAdmission control for new virtual connections– Connection setup and admission control across multiple Connection setup and admission control across multiple

switchesswitches– Virtual connection clearing across multiple switchesVirtual connection clearing across multiple switches

• Will replace Interim Inter-switch Signaling Protocol (IISP)Will replace Interim Inter-switch Signaling Protocol (IISP)

29 May 1997 61






29 May 1997 62

• Connection orientedConnection oriented

• ATM addressesATM addresses

• Unicast and point-to-Unicast and point-to-multipointmultipoint

• CellsCells

ATM Leaves a Hole for Data ATM Leaves a Hole for Data NetworkingNetworking

ATM

PHY

DataNetworkingProtocols

ATM

PHY

ATM

PHY

???? ????

DataNetworkingProtocols

???? ????

• ConnectionlessConnectionless

• MAC addressesMAC addresses

• BroadcastBroadcast

• Large framesLarge frames

29 May 1997 63

Stack Attack!Stack Attack!

Avoid Protocol Stack AttackAvoid Protocol Stack Attack

ATM

ModifiedIP

ATM

ModifiedIPX

ATM

ModifiedDECnet

...

• All modifications for incumbent protocols All modifications for incumbent protocols must be defined to deploy ATMmust be defined to deploy ATM

• Must cutover all protocols on first day of ATM Must cutover all protocols on first day of ATM deploymentdeployment

• Doubles the number of protocols until ATM is Doubles the number of protocols until ATM is ubiquitous end-to-endubiquitous end-to-end

• Not the path to a simple networkNot the path to a simple network

29 May 1997 64

LAN EmulationLAN Emulation

ATM

PHY

HigherLayersConnectionlessConnectionless

Protocol ServiceProtocol Service

LANEmulation

ATM

PHY

HigherLayers

LANEmulationConnection-orientedConnection-oriented

Protocol ServiceProtocol Service

ATM

PHY

The (first) ATM Forum solution*The (first) ATM Forum solution*

*Ratified in February 1995*Ratified in February 1995

ATMATM

29 May 1997 65

LAN Emulation ObjectiveLAN Emulation Objective

““The main objective of the LAN emulation service is to enable The main objective of the LAN emulation service is to enable existing applications to access an ATM network via protocol existing applications to access an ATM network via protocol stacks like APPN, NetBIOS, IPX, etc. as if they were running stacks like APPN, NetBIOS, IPX, etc. as if they were running over traditional LANs.”over traditional LANs.”

LAN Emulation Over ATM Specification - Version 1.0LAN Emulation Over ATM Specification - Version 1.0

29 May 1997 66

ATM Workgroup Protocol StacksATM Workgroup Protocol Stacks

PHYPHY

ATMATM

LANLANEmulationEmulation

DataDataProtocolProtocol

PHYPHY

ATMATM



PHYPHY

ATMATM

PHYPHY

ATMATMSwitchingSwitching

ConnectionlessConnectionlessProtocol ServiceProtocol Service

ATMATM

29 May 1997 67

PHYPHY

ATMATM



Legacy LAN Connection Protocol StacksLegacy LAN Connection Protocol Stacks

PHYPHY

ATMATM

LANELANE

PHYPHY

ATMATM

PHYPHY

ATMATMSwitchingSwitching

PHYPHY

MACMAC


PHYPHY

MACMAC

BridgingBridging

ATMATM

• Connectivity with Ethernet and Token Ring via translation bridgeConnectivity with Ethernet and Token Ring via translation bridge

• Small end systems unchanged and servers upgraded to ATMSmall end systems unchanged and servers upgraded to ATM

29 May 1997 68

Need to Segment Emulated LANsNeed to Segment Emulated LANs

155 Mbps155 Mbps

10 Mbps10 Mbps

5% LAN Broadcast Traffic:5% LAN Broadcast Traffic:.05 × 155 = 7.75 Mbps.05 × 155 = 7.75 Mbps

Ethernet CrushedEthernet Crushed

BridgeBridge

• Tune configuration to traffic patternsTune configuration to traffic patterns– Put communities of interest in separate emulated LANs Put communities of interest in separate emulated LANs

e.g., server and low-end PCse.g., server and low-end PCs– High end servers can belong to several emulated LANs High end servers can belong to several emulated LANs

to reduce number of serversto reduce number of servers– ““80-20 rule” becomes location independent80-20 rule” becomes location independent

• Policy e.g., keep the engineers off the finance networkPolicy e.g., keep the engineers off the finance network

29 May 1997 69

Emulated LANs with Server FarmEmulated LANs with Server Farm

EmulatedEmulatedLAN 1LAN 1


• Servers belong to both emulated LANsServers belong to both emulated LANs

• High performance for client server trafficHigh performance for client server traffic

ATMATM

29 May 1997 70

Connecting Emulated LANsConnecting Emulated LANs



• Router belongs to both emulated LANsRouter belongs to both emulated LANs

• Traffic between emulated LANs flows through Traffic between emulated LANs flows through router router

ATMATM

29 May 1997 71

Basic Approach to LAN EmulationBasic Approach to LAN Emulation

LAN Emulation ServiceLAN Emulation ServiceLUNILUNI

LUNILUNI

LAN EmulationServer

Broadcast andUnknown Server

LAN EmulationLAN EmulationClient(s)Client(s)


• Define interaction across Define interaction across the LAN Emulation UNI the LAN Emulation UNI (LUNI)(LUNI)

• Standard LAN Emulation Standard LAN Emulation ClientsClients

• Proprietary ServersProprietary Servers

• One client for each One client for each Emulated LAN in a deviceEmulated LAN in a device

29 May 1997 72

Broadcast/Multicast SupportBroadcast/Multicast Support

LAN Emulation ServiceLAN Emulation Service

Broadcast andUnknown Server



• Broadcast and Broadcast and Unknown Server Unknown Server serializes MAC framesserializes MAC frames

• Clients filter out MAC Clients filter out MAC frames not meant for frames not meant for themthem

Virtual Channel ConnectionsVirtual Channel Connections

29 May 1997 73

Unicast FramesUnicast Frames

LAN Emulation ServiceLAN Emulation Service

LAN EmulationServer



Client uses LAN Emulation Client uses LAN Emulation Server to find ATM Address Server to find ATM Address associated with destination associated with destination MAC addressMAC address

Client sets up virtual Client sets up virtual connection and transmits dataconnection and transmits data

11

22

11

22

29 May 1997 74

IP Over LANE ExampleIP Over LANE ExampleATM SwitchATM Switch(LES/BUS)(LES/BUS)

PCPCEthernet/ATMEthernet/ATMSwitch (LEC)Switch (LEC) ATM SwitchATM Switch ATM SwitchATM Switch

Server (LEC)Server (LEC)

IP ARPIP ARPARP RespARP Resp

LE ARPLE ARPLE ARP RespLE ARP RespDataData

DataDataDataDataDataDataDataData

Call SetupCall Setup

DataDataDataDataDataDataDataDataDataDataDataDataDataDataDataData

29 May 1997 75

EngineeringLEC 1

EngineeringLEC 2

EngineeringLEC 3

EngineeringLEC 4

Multiple Emulated LANsMultiple Emulated LANs

MarketingLAN Emulation

Server

MarketingBroadcast and

Unknown Server

MarketingLEC 1

MarketingLEC 2

MarketingLEC 3

MarketingLEC 4

EngineeringLAN Emulation

Server

EngineeringBroadcast and

Unknown Server

• Separate server functions Separate server functions for each emulated LANfor each emulated LAN

• A LEC is associated with a A LEC is associated with a single ELANsingle ELAN– Homed to appropriate Homed to appropriate

LES/BUSLES/BUS

• A physical device belonging A physical device belonging to multiple ELANs must to multiple ELANs must have a separate LEC for have a separate LEC for each ELANeach ELAN

29 May 1997 76

Intelligent LESIntelligent LES• LES can maintain a cache of <MAC Address, ATM LES can maintain a cache of <MAC Address, ATM

Address> bindingsAddress> bindings– Learned from Join Procedure as each LEC “attaches” to Learned from Join Procedure as each LEC “attaches” to

the LES and subsequent LEC registration requeststhe LES and subsequent LEC registration requests– LECs that are associated with bridges identify themselves LECs that are associated with bridges identify themselves

as a “proxy”as a “proxy”– MAC addresses “behind” proxies are not registered by MAC addresses “behind” proxies are not registered by

LES, i.e., not put into cacheLES, i.e., not put into cache

• LES responds to LE ARP if there is a cache hitLES responds to LE ARP if there is a cache hit

• Else, LES forwards LE ARP to all “proxy” LECsElse, LES forwards LE ARP to all “proxy” LECs

29 May 1997 77

LAN Emulation Configuration ServerLAN Emulation Configuration Server• Helps LEC get configuredHelps LEC get configured

– LEC sets up VCC to LECS and sends Configuration RequestLEC sets up VCC to LECS and sends Configuration Request– LECS returns Configuration Response with ATM address of appropriate LES plus other configuration informationLECS returns Configuration Response with ATM address of appropriate LES plus other configuration information– LEC sets up VCC to LES and joins ELANLEC sets up VCC to LES and joins ELAN– LEC uses LE ARP for all 1’s to obtain ATM address of BUSLEC uses LE ARP for all 1’s to obtain ATM address of BUS– LEC sets up VCC to BUSLEC sets up VCC to BUS

• LEC finds LECS by one of followingLEC finds LECS by one of following– LECS ATM address learned via ILMILECS ATM address learned via ILMI– ““Well known” ATM address for LECSWell known” ATM address for LECS– VPI/VCI = 0/17VPI/VCI = 0/17– Preconfigured in LECPreconfigured in LEC

29 May 1997 78






29 May 1997 79

Major Location(DS1 Access)

Major Location(DS1 Access)

Small Locations(DS0 Access)


PVC

Full mesh of PVCs not shown

Pre-ATM Scenario: Frame RelayPre-ATM Scenario: Frame Relay

Carrier Frame Relay Service

29 May 1997 80

Migration IssuesMigration Issues• ATM interfaces will first be attractive at the major ATM interfaces will first be attractive at the major

locationslocations– Integrating multiple access lines into few (one) will yield Integrating multiple access lines into few (one) will yield

significant cost savingssignificant cost savings» Access line is major part of tariffsAccess line is major part of tariffs» Reduces port costs on CPEReduces port costs on CPE» ATM UNI can support multiple servicesATM UNI can support multiple services

• Advantage will probably be lost if large number of small Advantage will probably be lost if large number of small locations must be also be migrated to ATM locations must be also be migrated to ATM

• Solution: service interworkingSolution: service interworking

29 May 1997 81

Multiple Services at the UNIMultiple Services at the UNI

Audio Conference

PBX-CO Trunk

GoliathNet SMDS

DaveNet Frame Relay

Video News Feed

ATM Virtual Channel Connection

Physical Link

29 May 1997 82

Service Interworking: Frame RelayService Interworking: Frame Relay

Major Location(DS3/STS3c Access)

Major Locationwith service multiplexer

(DS3/STS3c Access)



PVCs not shown - same as inoriginal configuration

PBX-CO trunk etc.

ATM UNI

29 May 1997 83

Frame Relay at the UNIFrame Relay at the UNI

Frame Relay PVC 1

PBX-CO Trunk

Frame Relay PVC 2

Frame Relay PVC 37

Frame Relay PVC 7

Physical Link

ATM Virtual Channel Connection

• Frame Relay PVCs mapped to ATM PVCsFrame Relay PVCs mapped to ATM PVCs– FECN, BECN to PTI mappingFECN, BECN to PTI mapping– Traffic ManagementTraffic Management– Etc.Etc.

• Protocol ratified by ATM Forum Technical Working Group (SAA Subgroup) and Frame Relay ForumProtocol ratified by ATM Forum Technical Working Group (SAA Subgroup) and Frame Relay Forum

29 May 1997 84

Frame Relay Access ConfigurationsFrame Relay Access Configurations

Frame Relay

CSU/DSU

CSU/DSU

ATM DXI

Frame Relay

Service Multiplexer

ATM UNI

29 May 1997 85






29 May 1997 86

LAN Emulation Version 2.0LAN Emulation Version 2.0• Bug fixes, minor enhancements for LUNIBug fixes, minor enhancements for LUNI

• Improved scalability and robustness via inter-server Improved scalability and robustness via inter-server protocol called LNNI (LAN Emulation Network Node protocol called LNNI (LAN Emulation Network Node Interface)Interface)

• QOS support including Available Bit RateQOS support including Available Bit Rate

• Special Multicast Service for improved multicastSpecial Multicast Service for improved multicast

• LLC multiplexing on DDVCCsLLC multiplexing on DDVCCs

• Backward compatible with LUNI 1.0Backward compatible with LUNI 1.0

29 May 1997 87

LANE v2.0 StatusLANE v2.0 Status

• Issued as two documentsIssued as two documents

• LUNI v2.0LUNI v2.0– Out for Letter BallotOut for Letter Ballot– Ratification in July or AugustRatification in July or August– Technically frozenTechnically frozen

• LANE Network-Network Interface (LNNI) v2.0LANE Network-Network Interface (LNNI) v2.0– Outstanding technical issuesOutstanding technical issues– Scheduled for completion by January 1998Scheduled for completion by January 1998

29 May 1997 88

LANE Version 2.0 Reference ModelLANE Version 2.0 Reference Model

LES 1BUS 1

LES 2BUS 2

LECS

LES-LES

BUS-BUS

LEC LEC LEC LEC

LUNI LUNI LUNI LUNI

LECS-LES/BUS LECS-LES/BUS

LECLEC LAN Emulation ClientLAN Emulation ClientLESLES LAN Emulation ServerLAN Emulation ServerBUSBUS Broadcast and Unknown ServerBroadcast and Unknown Server

LECSLECS LAN Emulation Configuration ServerLAN Emulation Configuration Server

LECSLECS-LECS

29 May 1997 89

LES/BUS Mesh InterconnectionLES/BUS Mesh Interconnection

• Extensive use of point-to-multipoint connections to Extensive use of point-to-multipoint connections to reduce LES/BUS complexityreduce LES/BUS complexity

• Simple rules to prevent loopingSimple rules to prevent looping

• This does not provide larger BUS capacityThis does not provide larger BUS capacity

LES/BUS 1LES/BUS 1

LECLEC LECLEC

LES/BUS 2LES/BUS 2

LECLEC LECLEC

LES/BUS 3LES/BUS 3

LECLEC LECLEC

29 May 1997 90

Will Use “Peer-Tree” ApproachWill Use “Peer-Tree” Approach

• Each peer node can be a mesh of servers or simply a dedicated tandem serverEach peer node can be a mesh of servers or simply a dedicated tandem server• External links can be connected to any LES/BUS in peer nodeExternal links can be connected to any LES/BUS in peer node• Spanning tree (re)constructed out of redundant linksSpanning tree (re)constructed out of redundant links• IETF Server Cache Synchronization Protocol used to maintain server data IETF Server Cache Synchronization Protocol used to maintain server data

coherencecoherence

WAN LinkWAN Link

LES/BUS 1LES/BUS 1 LES/BUS 2LES/BUS 2 LES/BUS 3LES/BUS 3 LES/BUS 1LES/BUS 1 LES/BUS 2LES/BUS 2 LES/BUS 3LES/BUS 3 LES/BUS 1LES/BUS 1 LES/BUS 2LES/BUS 2 LES/BUS 3LES/BUS 3

LES/BUS 1LES/BUS 1 LES/BUS 2LES/BUS 2 LES/BUS 3LES/BUS 3LES/BUS 1LES/BUS 1 LES/BUS 2LES/BUS 2 LES/BUS 3LES/BUS 3

29 May 1997 91

QoS in LANE v2.0QoS in LANE v2.0• Defined via abstract protocol service interface between “higher Defined via abstract protocol service interface between “higher

layer” and LANElayer” and LANE

• Higher layer can define a QoS by passing call setup Higher layer can define a QoS by passing call setup parameters in a “Define QoS” primitiveparameters in a “Define QoS” primitive– qos_handle (label allocated)qos_handle (label allocated)

• Higher layer passes unicast MAC frame to LANE with a Higher layer passes unicast MAC frame to LANE with a qos_handleqos_handle

• LANE attempts to send frame on DDVCC setup with setup LANE attempts to send frame on DDVCC setup with setup parameters implied by qos_handleparameters implied by qos_handle

• ABR is an example of QoSABR is an example of QoS

29 May 1997 92

Improved Multicast in LANE v2.0Improved Multicast in LANE v2.0

LECLEC LECLEC LECLEC LECLEC LECLEC

MCS1MCS1 MCS2MCS2• Special Multicast ServiceSpecial Multicast Service

– Colocated with BUSColocated with BUS– Allows clients to register for multicasts Allows clients to register for multicasts

(and not have to filter unwanted (and not have to filter unwanted multicasts)multicasts)

• Intelligent BUSIntelligent BUS– All multicasts sent to I-BUSAll multicasts sent to I-BUS– I-BUS forwards on proper point-to-I-BUS forwards on proper point-to-

multipoint based analysis of multicast multipoint based analysis of multicast addressaddress

• Both approaches look the same to LECsBoth approaches look the same to LECsLECLEC LECLEC LECLEC LECLEC LECLEC

I-BUSI-BUS

29 May 1997 93

LLC/SNAP MultiplexingLLC/SNAP Multiplexing

LECLEC

LECLEC

LECLEC

LECLEC

VCC MultiplexingVCC Multiplexing

DDVCCDDVCC

DDVCCDDVCCLECIDLECID MAC FrameMAC Frame

FormatsFormats

LECLEC

LECLEC

LECLEC

LECLEC

LLC/SNAP MultiplexingLLC/SNAP Multiplexing(DDVCCs only)(DDVCCs only)

DDVCCDDVCCLECIDLECID MAC FrameMAC FrameLLC/SNAPLLC/SNAP ELAN-IDELAN-ID

29 May 1997 94

LUNI v2.0 ComplianceLUNI v2.0 Compliance

Enhanced ConfigurationEnhanced Configuration MandatoryMandatoryExtended TLVsExtended TLVs MandatoryMandatoryARP-based TLVsARP-based TLVs MandatoryMandatoryExtended Abstract Service I/FExtended Abstract Service I/F Mandatory*Mandatory*QoSQoS OptionalOptionalMulticastMulticast OptionalOptionalLLC MultiplexingLLC Multiplexing OptionalOptionalUNI 4.0UNI 4.0 OptionalOptional

*Compliance not testable*Compliance not testable

29 May 1997 95

Multi Protocol Over ATM v1.0Multi Protocol Over ATM v1.0• MPOA Working Group formed in November 1994MPOA Working Group formed in November 1994

• Developed the MPOA “Cathedral”Developed the MPOA “Cathedral”– Unreasonable goalsUnreasonable goals– Poor articulation of technical approachPoor articulation of technical approach

• Pressure from early ATM adopters to solve the Big Fancy Pressure from early ATM adopters to solve the Big Fancy Router (BFR) problemRouter (BFR) problem

• Scaled back focus in August 1996Scaled back focus in August 1996– Solve BFR problem for IPSolve BFR problem for IP

• Out for Letter BallotOut for Letter Ballot– Ratification in July or AugustRatification in July or August

29 May 1997 96

BFR Bottleneck Emerges Again BFR Bottleneck Emerges Again

• Early ATM adopters (with many Early ATM adopters (with many subnets) experiencing poor subnets) experiencing poor client/server performanceclient/server performance– Low throughput for BFRLow throughput for BFR– Inter ELAN traffic limited to ½ of Inter ELAN traffic limited to ½ of

bandwidth of BFR ATM linkbandwidth of BFR ATM link– Multiple hops across ATM cloud Multiple hops across ATM cloud

is “ugly”is “ugly”– ““Our jobs are on the line.” - MIS Our jobs are on the line.” - MIS

managersmanagers

ELAN (= subnet)ELAN (= subnet)

Router on a StickRouter on a Stick

Big FancyBig FancyRouterRouter

29 May 1997 97

MPOA v1.0 ExampleMPOA v1.0 Example

SS DD

Router 1Router 1

EdgeEdgeDevice 1Device 1

ELAN AELAN A ELAN BELAN B ELAN CELAN C ELAN DELAN D

ATMATM

Router 2Router 2 Router 3Router 3

EdgeEdgeDevice 2Device 2

MPSMPS MPSMPS MPSMPS

MPCMPC MPCMPC

1111 NHRP Request:NHRP Request:

What is ATM address for D?What is ATM address for D?

11 11

22

22 Cach Imposition Protocol:Cach Imposition Protocol:Get ready for shortcut.Get ready for shortcut.

22

3333

33

33 NHRP Response:NHRP Response:Use address of ED2.Use address of ED2.

44

44 Shortcut VCC setupShortcut VCC setup

29 May 1997 98

SummarySummary

• Today’s benefit to customers from ATM is data Today’s benefit to customers from ATM is data networking bandwidth in the backbonenetworking bandwidth in the backbone

• ATM introduces many new concepts (and ATM introduces many new concepts (and acronyms) to data networkingacronyms) to data networking

R

Networks That Go the Distance™Networks That Go the Distance™

ATM Network

Documents

Transcript of ATM Network