Introduction to ATM 1 NW97_EMEA_314. 2 Characteristics of ATM Uses small, fixed-sized cells Connection-oriented Supports multiple service types Applicable

Introductionto ATM

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Characteristics of ATM

• Uses small, fixed-sized cells

• Connection-oriented

• Supports multiple service types

• Applicable to LAN and WAN

Cells

Voice

Data

Video

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ATM Standards Now Ready

1991 1992 1993 1994 1995 1996

IISPIISP• Static ATM routingStatic ATM routing• SVC interoperabilitySVC interoperability

PNNIPNNI• Dynamic ATM routingDynamic ATM routing

Traffic ManagementTraffic Management• Available Bit Rate (ABR)Available Bit Rate (ABR)

Signalling 4.0Signalling 4.0

UNI 2.0UNI 2.0• Cell formatCell format• Physical layersPhysical layers

ATM ForumATM ForumFoundedFounded

UNI 3.0UNI 3.0• SignallingSignalling• Traffic policingTraffic policing

LAN LAN EmulationEmulation

Test Beds and Pilots

Early Adopters

Small-Scale Production Networks

Large-Scale Large-Scale ATM InternetworksATM Internetworks

1997

VTOAVTOAMPOA MPOA

ATM Forum FoundersCisco Systems

SprintNet/Adaptive

Northern Telecom

“Anchorage Accord”

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ATM Reference Model

ATM ATM Adaptation LayerAdaptation Layer

(AAL)(AAL)

ATM LayerATM Layer

Physical LayerPhysical Layer

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ATM Reference Model


(AAL)(AAL)

ATM LayerATM Layer


Two Sublayers:

• Transmission Convergence (TC)Framing

HEC

• Physical Media Dependent (PMD)Physical media coding

Physical Layer

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ATM Transmission Media

SDH SONET Rate—Mbps

STM-1STM-1

STM-4STM-4

STM-8

STM-16

STS-1/OC-1

STS-3/OC-3STS-3/OC-3

STS-12/OC-12STS-12/OC-12

STS-24/OC-24

STS-48/OC-48

51.84

155.52155.52

622.08622.08

1,244.16

2,488.32

ATM SDH/SONET Rates Chart

• CCITT (Consultative Committee for International Telephony and Telegraph)

• ITU (International Telecommunications Union)

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Physical LayerDataDataRateRate

(Mbps)(Mbps)

DS1DS1E1E1J2J2

1.5441.5442.0482.0486.236.23

FramingFraming MediaMedia

Multi-Multi-ModeModeFiberFiber

Single-Single-ModeModeFiberFiber

CoaxialCoaxialCableCable

UTP–5UTP–5 UTP–3UTP–3 STPSTP

XX

(TP)(TP)

(TP)(TP)

ATM25ATM25STS 1STS 1STS3c/STM1STS3c/STM1

25.625.651.851.8155155 XX

STS 12c/STM4STS 12c/STM44B/5B (TAXI)4B/5B (TAXI)8B/10B8B/10B(Fiberchannel)(Fiberchannel)

622622100100155155

= = StandardizedStandardized

= Proposed/In Progress= Proposed/In ProgressXX


(AAL)(AAL)

ATM LayerATM Layer


DS3DS3E3E3E4E4

45453434

139139

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ATM Reference Model

• Cell header insertion/removal

• Cell Relay

• Multiplexes/demultiplexes cells of different connections


(AAL)(AAL)

ATM LayerATM Layer


ATM Layer

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Creating Cells from PacketsDest.

AddressSource

AddressData

FrameCheck

PayloadPayloadHeaderHeader

Packet

Cells




5 Byte5 ByteHeaderHeader

48 Byte48 BytePayloadPayload

ATM Cell

53Bytes

SARSegmentation and Reassembly

Segmentation Happens at Source

Reassembly Happens at Destination

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ATM Cell Header

ATM Cell



53 Bytes

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ATM Cell Header Details

GFCGFC Generic Flow ControlUNI Cells Only!

VPI/VCIVPI/VCI Identifies VirtualPaths and Channels

PTIPTI Payload Type Identifier3 Bits:

1. User/Control Data2. Congestion3. Last Cell

CLPCLP Cell Loss Priority Bit

HECHEC Header Error Check8 Bit CRC

ATM NNINNI Cell


VPI (12)VPI (12)

VCI (16)VCI (16)

PTIPTI CLPCLP

HECHEC

ATM UNI UNI Cell


GFC (4)GFC (4)VPI (8)VPI (8)

VCI (16)VCI (16)

PTIPTI CLPCLP

HECHEC

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ATM Switches

• ATM switch performs cell-relay using connection identifiers

Virtual Channel Identifier (VCI)

Virtual Path Identifier (VPI)

• ATM layer in ATM switches translates VPI/VCI values

• VPI/VCI value unique only per interface, may be re-used elsewhere in network

ATM Switch

22

33

29 6464

Output

2929

45InputPort

1

2

11

33

VPI/VCI

29

45

6464

2929

Port

2

1

33

11

VPI/VCI

45

29

2929

6464

11

Virtual Path and Virtual Channels

ATM Physical Link

Virtual Path(VP)

Contains Multiple VCs

Virtual Channel Connection(VCC) or

Virtual Path Connection (VPC) is end-to-end

Virtual Channel(VC)

Logical PathBetween ATM End Points

Virtual Channels (VC)

Virtual Channels (VC)

E1E3

STM-1STM-4

Virtual Path (VP)

Virtual Path (VP)

Connection Identifier = VPI/VCIVPI/VCI

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VP and VC Switching

VCI 1 VCI 2 VCI 3 VCI 4

VPI 2VPI 2VPI 3VPI 3VPI 1VPI 1

VPI 2VPI 2

VPI 3VPI 3

VPI 5

VPI 1VPI 1

VPI 4

Port 1Port 1

Port 2Port 2

Port 3Port 3

VCI 1

VCI 2

VCI 1

VCI 2

VP Switch

VC Switch

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ATM Signalling

• UNI = User-to-Network Interface

• NNI = Network-to-Network Interface

• Cell header content varies depending on who’s talking to whom

TokenRing

Public UNIaka B-ICI

UNI

NNI

NNI

NNI

Public ATM Network

Private ATM Network

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ATM Signalling: The UNI

• UNI 3.0 and UNI 3.1—Provide SVC capability at the UNI

UNI 3.0 and 3.1 not interoperablenot interoperable because they use different data link signalling protocols:

Q.SAAL vs. SSCOP

• Sig 4.0Multicast

Better QoS

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ATM Connection Types

• PVC, SVC, and Soft PVC

• Point-to-point and Multipoint

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Connection Types

Connectionless: Packet Routing

• Path 1 = S1, S2, S6, S8

• Path 2 = S1, S4, S7, S8

• Data can take different pathand can arrive out of order

Connection Oriented: Cell Switching

• VC = S1, S4, S7, S8

• Data takes the same path and arrives in sequence

S2 S6

S4 S7

S3 S5

S1 S8

1

1

1

2 2

2

S2 S6

S4 S7

VC

S1 S8S3 S5

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Permanent Virtual Circuit (PVC)

• VPI/VCI tables in network equipment updated by administrator

AA

BB

DD

CC

InputInput OutputOutputPortPort VPI/VCIVPI/VCI PortPort VPI/VCIVPI/VCI

1 33 3 02

22 1515 33 1414

1 64 3 29

3 29 1 64


11 2929 33 4545

22 5252 44 1515

1 64 3 29

3 29 1 64


11 4545 22 1616

2 52 1 29

1 64 3 29

3 29 1 64

2929

3030

1010

1616

1515

45451414

4343


11 1616 22 4343

33 1414 44 1010

1 64 3 29

3 29 1 64

1

2

4 2

3

32

4

12

3

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Switched Virtual Circuit (SVC)

• Dynamically setup and tear down connections

BB

DD

1

2

4 1

3

32

4

12

UNIUNISignallingSignalling

NNINNISignallingSignalling CC



1 64 3 29

3 29 1 64


2 52 1 29

1 64 3 29

3 29 1 64


1 29 3 45

1 64 3 29

3 29 1 64


1 64 3 29

3 29 1 64AA

3

11 2929 33 4545

11 4545 22 1616 11 1616 22 4343

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Soft PVC

• PVC established manually across UNI UNI and dynamically across NNINNI

B

D

1

1

2

NNINNISignallingSignalling



1 64 3 29

3 29 1 64


2 52 1 29

1 64 3 29

3 29 1 64


1 29 3 45

1 64 3 29

3 29 1 64


1 64 3 29

3 29 1 64

3


11 2929 33 4545

11 1616 22 4343

CC

AA

Point-to-Point and Multipoint

“Root” “Leaves”

• Point-to-pointUni-directional orbi-directional traffic

• Point-to-multipointUni-directional(root-to-leaves) only

UNI 3.1: Only Root can add leafs

Sig 4.0: Leaf Initiated Joins

• Multipoint-to-point

VC-Merge and Funnel Join

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ATM Reference Model

Two Sublayers:

• Convergence Sublayer (CS)

• Segmentation and Reassembly (SAR)


(AAL)(AAL)

ATM LayerATM Layer


ATM Adaption Layer (AAL)

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ATM Adaptation Layer—AAL

SAR

CS

AALPBX


(AAL)(AAL)

ATM LayerATM Layer


AAL = CS + SAR• CS—assigns different AAL’s/QoS for different traffic types

• SAR—cell <-> packet

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ATM Adaptation LayerServiceService

CategoriesCategoriesClassClass


(AAL)(AAL)

ATM LayerATM Layer


Bit RateBit Rate ConnectionConnectionModeMode

TimingTimingConcernConcern

ApplicationApplicationExamplesExamples

• Bandwidth andBandwidth andthroughput guaranteedthroughput guaranteed

• Good for voice Good for voice and videoand video

AAL1AAL1AA CBRCBR(Constant)(Constant)

also VBRalso VBR

Connection-Connection-OrientedOriented

YesYes

• Best effort bandwidth Best effort bandwidth and throughputand throughput

• Good for live video,Good for live video,multimedia, multimedia, LAN-to-LANLAN-to-LAN

AAL2AAL2BB VBRVBR(Variable)(Variable)VBR-ATVBR-AT

andandVBR-NRTVBR-NRT


YesYes

• Best effort withBest effort withcongestion feedbackcongestion feedback

• Reliable delivery Reliable delivery of bursty traffic ifof bursty traffic iflatency okaylatency okay

AAL5AAL5CC ABRABR(Available)(Available)

also UBRalso UBR


NoNo

• No guaranteeNo guarantee• For SMDS/LANFor SMDS/LAN

AAL3/4AAL3/4DD UBRUBR(Un-(Un-

specified)specified)

Connection-Connection-lessless

NoNo

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AAL• AAL criteriaAAL criteria

Traffic parameters

QoS parameters

• The AAL’s

AAL1—CBR

AAL2—VBR

AAL3/4—UBR

AAL5—ABR/UBR

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AAL Criteria

• Traffic ParametersPeak cell rate

Sustainable cell rate

Maximum burst size

Minimum Cell Rate

• Quality of ServiceDelay

Cell loss

Contract

Contract

ContractContractATM Network

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AAL Criteria Traffic Parameters

• Peak Cell Rate—PCRPCR—Maximum data rate a connection can handle without losing data

• Sustainable Cell Rate—SCRSCR—Average ATM cell throughput the application is permitted

• Maximum Burst Size—MBSMBS—Size of themaximum burst of contiguous cells that can be transmitted

• Minimum Cell Rate—MCRMCR—Rate of anapplication’s ability to handle latency

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AAL Criteria QoS—Delay

• Maximum Cell Transfer Delay—MCTDMCTD How long the network can take to transmit a cell from one endpoint to another

• Cell Delay Variation Tolerance—CDVTCDVT Line distortion caused by change in interarrival times between cells aka jitter

QoS—Cell Loss• Cell Loss Ratio—CLRCLR

Acceptable percentage of cells that the network can discard due to congestion

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ATM Quality of Service

• Constant Bit-Rate (CBR)

• Variable Bit-Rate (VBR)Real time (RT-VBR)

Non-real time (nRT-VBR)

“Bandwidth-on-demand”

Traffic contracts

QOS guarantees

• Available Bit-Rate (ABR)

• Unspecified Bit-Rate (UBR)

No QOS guarantees

Bursty, unpredictable traffic

Need to minimize cell loss

Guaranteed Service

Best Effort

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The AAL’sAAL1—Constant Bit Rate (CBR)also VBR

Real Time Voice and VideoReal Time Voice and Video

Overhead

1 Byte1 Byte



QoSTraffic Parameter

LOWLOW HIGHHIGH

Tolerance

Cell DelayCell DelayCell LossCell Loss

PCRPCRPeak Cell Rate

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The AAL’sAAL2—Variable Bit Rate

Packetized Voice/Video, SNAPacketized Voice/Video, SNA

(VBR-RT/VBR-NRT)

Overhead


LOWLOW HIGHHIGH

Tolerance

1–481–48BytesBytes


1–47 Byte1–47 BytePayloadPayload

Cell DelayCell Delay(NRT)(NRT)Cell Delay (RT)Cell Delay (RT)

PCRPCR

SCRSCRPeak Cell Rate

Sustainable Cell Rate

MBSMBSMaximum Burst Size Cell LossCell Loss

AAL2 beingupdated

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The AAL’sAAL3/4—Unspecified Bit Rate (UBR)

Public WAN—SMDSPublic WAN—SMDS

Overhead




LOWLOW HIGHHIGHNo GuaranteesSend and Pray

Tolerance

Cell LossCell LossCell DelayCell Delay

4 Bytes

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The AAL’sAAL5—Available Bit Rate (ABR)also UBR

LAN Interconnect for DataLAN Interconnect for Data

Overhead

• No celloverhead

• Uses congestionfeedbackinstead




LOWLOW HIGHHIGH

PCRPCR

MCRMCR

Peak Cell Rate

Minimum Cell Rate

Tolerance

Cell LossCell Loss Cell DelayCell Delay

Last Cell Header has End of Message

(EOM) Bit

HH

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A Day in the Life of a CellATM Payload Processing

TCPTCP

IPIP

LLC/SNAPLLC/SNAP

AALAAL

ATMATM

PHYPHY

TCP PacketTCP Packet

IP DatagramIP Datagram

AddAdd 5 Byte Headers with VPI/VCI and CLP 5 Byte Headers with VPI/VCI and CLP

App DataApp DataTCP HeaderTCP HeaderIP HeaderIP HeaderLLCLLC

App DataApp DataTCP HeaderTCP HeaderIP HeaderIP Header

App DataApp DataTCP HeaderTCP Header

ConvergenceConvergenceSublayer (CS)Sublayer (CS)

SARSAR

App DataApp DataTCP HeaderTCP HeaderIP HeaderIP HeaderLLCLLCQoS +QoS +

Put in 48 Byte Cells—SAR into PDUPut in 48 Byte Cells—SAR into PDU

Transmission Convergence (STS, STM, DS)Transmission Convergence (STS, STM, DS)

Physical Media (MMF, SMF, STP, UDP,…Physical Media (MMF, SMF, STP, UDP,…

A Day in the Life of a CellTraversing the Network

ATM SwitchATM Switch

PPHHYY

AATTMM

Port 1

PPHHYY

AATTMM

Port 2

PortPort VPIVPI VCIVCI

11 11 5151

22 33 3939

ATM Layer

ATM SwitchATM Switch

PPHHYY

AATTMM

Port 1

PPHHYY

AATTMM

Port 2

PortPort VPIVPI VCIVCI

11 22 3737

22 11 5151

ATM Layer

PPHHYY

AATTMM

AAAALL

PPHHYY

AATTMM

AAAALL

VPI 2VCI 37

VPI 3VCI 39

NNI

UNI

UNI

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Traffic Management

• Why traffic management?

• Traffic control techniques

• AAL5/ABR congestion feedback

• Buffers are your friend

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Why Traffic Management?

• Proactively combat congestion

• Provision for priority control

• Maintain well-behaved traffic

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Ethernet (1500 Bytes) = 32 Cells

FDDI (4470 Bytes) = 96 Cells

IP over ATM–1577 (9180 Bytes) = 192 Cells

Why Traffic Management?

• Lose one cell and the rest are useless

• Need to re-transmit 32+ cells for one cell lost

• Congestion collapseCongestion collapse is the result

TCP/IP Packet

X

Cell LossCell Loss—Data’s Critical Enemy

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Traffic Control Techniques

• Connection management—Acceptance

• Traffic management—Policing

• Traffic smoothing—Shaping


Connection Management Connection Admission Control (CAC)

ATM Network

I want a VC:X MbpsY DelayZ Cell Loss

CACCACCan I Support this Reliably without

Jeopardizing Other Contracts

Noor

Yes, Agree to aTraffic Contract

Guaranteed QoS Request

ContractContract

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Traffic ManagementUsage Parameter Control (UPC) aka PolicingPolicing

ATM Network

You areNot in Conformancewith the Contract.What Should the

Penalty Be??

• PASSPASS• MARK CLP BITMARK CLP BIT• DROPDROP

?DECISION??DECISION?

Contract

REBELREBELAPPLICATIONAPPLICATION

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Traffic Control TechniquesTraffic Management

• CLP Control—When congested dropdrop markedmarked cells

• Public UNI—Generic Cell Rate Algorithm (GCRA)

00 00 00 00 1 00MarkedMarked

UPC

• PASSPASS• MARK CLP BITMARK CLP BIT• DROPDROP

?DECISION??DECISION?DDrroopp

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• Intelligent Packet Discard—IPDIPD

• Discard cells from same ‘bad’ packet

• Tail packet discard

• Maximize “GoodputGoodput”

Traffic Management

3 2

00 00 00 00 1 00MarkedMarked

UPC

DDrroopp

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Benefit of Packet Discard

Switch without Packet Discard

Switch with Intelligent Packet Discard

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Congestion Control

ATM/Switch

66

11 00

55

44

Output BufferEOMEOM

UPCUPC

77 33 22 11

XX

Intelligent Tail Packet Discard

Output Queue

EOMEOM

EPD Threshold

EOMEOM

Early Packet Discard

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• Traffic shaper at customer site

• Changes traffic characteristics

• Leaky bucket algorithm

Private ATM Network Public ATM Network

Shaped DataActual Data

I Want to Comply With My

Contract. So, I Will Smooth/Shape

My Traffic

Go Ahead,

Make My Day

Sh

ap

er

Traffic Smoothing

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Additional Congestion ControlAvailable Bit Rate (ABR)

Feedback

B

C

A

Z

LightStream

LightStream

Must Minimize Must Minimize Feedback DelayFeedback Delay

Feedback Mechanisms Feedback Mechanisms Must be Integrated into Must be Integrated into

Switch HardwareSwitch Hardware

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Three ABR Schemes

Explicit Rate ModeExplicit Rate ModeMost SophisticatedMost Sophisticated

Ideal for WAN NetworksIdeal for WAN Networks

Complexity/Cost

Eff

icie

ncy Relative Rate ModeSimple and Efficient

Ideal Campus Networks

EFCI ModeEFCI ModeBackward CompatibilityBackward Compatibility

High LatencyHigh Latency

LightStream 1010 Family

StrataComSwitchFamily

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• EFCI Marking—Explicit Forward Congestion IndicatorCongestion flag set on forward cells only

Destination end-system sends RM cells back to source

AAL5/ABR Congestion Feedback

SourceSource

DestinationDestination

ForwardForward

RMRM RMRM

BackwardBackward

EFCI Set EFCI Set

XX XX

XX XX

CongestionCongestionExperiencedExperiencedSlow DownSlow Down

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• Relative rate marketingSwitches can set congestion flag in backward RM cells

SourceSource


ForwardForward

BackwardBackward



RMRM XX

RMRM

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• Explicit rate marketingSwitches can tell source at exactly what rate to transmit

SourceSource


ForwardForward

BackwardBackward



RMRM

RMRM

Congestion ExperiencedCongestion ExperiencedSlow Down X AmountSlow Down X Amount

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• VS/VD—Virtual source/virtual destinationBreaks the feedback loop into separate segments

Shortens length of feedback loop

SourceSource


ForwardForward

BackwardBackward

Congestion Congestion ExperiencedExperiencedSlow DownSlow Down

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• Absorb traffic bursts from simultaneous connections

• Switches schedule traffic based on priority of traffic according to QoS

• Switch must reallocate buffers as the traffic mix changes

• Effective bufferingEffective buffering maximizes throughput of usable cells as opposed to raw cells (aka goodputaka goodput)

Buffers Are Your Friend

ATM Addressing Formats• Public network will use

E.164 numbers

• ATM Forum defined new ATM private-network address formats:

Modelled on NSAPs

AFIAFI

DCCDCC

E.164E.164

ESIESI

DSPDSP

ICDICD

SELSEL

Authority and Format Identifier Authority and Format Identifier

Data Country Code Data Country Code

ISDN (Telephone) NumberISDN (Telephone) Number

End System Identifier (IEEE)End System Identifier (IEEE)

High Order Part of DSPHigh Order Part of DSP

International Code DesignatorInternational Code Designator

NSAP SelectorNSAP Selector

E.164 ATM Address Format45

AFI DCC ESI SEL

DCC ATM Address Format39

DSP

AFI ICD ESI SEL

ICD ATM Address Format47

DSP

AFI ICD ESI SELDSPE.164

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Possible Addressing Plan

. . .

San Jose Main47.0091.8000.1122.0001

San Jose South47.0091.8000.1122.0002

Chelmsford47.0091.8000.1122.0101

Building A47.0091.8000.1122.0001.01

Building O47.0091.8000.1122.0001.0F

Building O, 1st Floor47.0091.8000.1122.0001.0F.01

Building O, 2nd Floor47.0091.8000.1122.0001.0F.02

level 56

level 72

level 80

level 72level 72

level 88level 88

level 80

cisco corporate network47.0091.8000.1122Cisco ICD

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Address Registration in ATMGoal: No Manual Configuration

• Integrated Local Management Interface (ILMI) eliminates need for manual configuration—autoconfiguration

• ATM end-point sends “SNMP format” queries

• End Station Identifier (ESI) and hierarchical prefix included in ATM address

ATM End Station ATM Switch

MAC Address (ESI)

ATM Address Prefix

ILMI Protocol

UNI

ILMIMIB

LECS Address

Or

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ATM Routing

• Now ATM switch-based:

IISP

PPNI Phase 1

What Is Path Determination?

Source

Destination

Source

Destination

• Traditionally router-based:

RIP

IGRP

OSPF

EIGRP

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IISP

• Interim Inter-switch Signalling Protocol (IISP)Static route defined in ATM switches

Dynamic call setup via UNI signalling

Suitable for small ATM networks

UNI 3.1/3.0for SVC

UNI 3.1/3.0

Port 1

Port 2


BB

PrimaryPrimary

Port 1Port 1

SecondarySecondary

Port 2Port 2

A

B

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PNNI

• Distributes reachability and topology information between switches

• Dynamic re-routing around failures

• Routing for reachability based on OSPF

• Peer groups are analogous to an OSPF area

• PNNI allows hierarchical organization of network

A Routing Protocol

PGPG

PG

PGPG

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PNNI

• PNNI—provides a path that satisfies the request QoS

• Negotiates metrics such as AvCR, MCTD, MCLR

• Uses Connection Admission Control (CAC)

• Uses Crankback for re-routing to alternate path

A Signalling Protocol

B.2

B.6

B.3

B.5B.4

B.1Re-Route

C.2

C.1 C.3

A.1A.3

A.2

Link B.3–B.6 does Not have Sufficient AvCR

A

B

C

Crank-Back

Source

Destination

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PNNI Hierarchy

A Group of Peer Groups

A Group of ATM Switches

(Peer Group)

An ATM Switch

PG

PG

PG

PG

PGSwitchSwitch

SwitchSwitch SwitchSwitch

SwitchSwitch SwitchSwitch

SwitchSwitch

IFIFCardCard

SwitchingSwitchingFabricFabric

IFIFCardCard

IFIFCardCard

IFIFCardCard IFIF

CardCard

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ATM Internetworking

• Challenges

• RFCs1483, 1577, and NHRP

• LANE and MPOA

• IP Multicasting

• Quality of Service

• Tag and MPLS

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ATM Internetworking

• MAC address to ATM address resolution

• No Standard ATM API

The ChallengesExisting and NewExisting and New

ApplicationsApplications

Network AddressNetwork Address

ATM AddressATM Address ATM AddressATM Address

MAC AddressMAC Address

APIAPI

??????

NewNewApplicationsApplications

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ATM Internetworking

• Multiple layers of addressing

ATM AddressesATM Addresses

Direct-AttachedStations

Ethernet Ethernet

Router or Switch

Router or Switch

Network Addresses,Network Addresses,MAC AddressesMAC Addresses

ATMNetwork

Overlay Model

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ATM Internetworking

• Encapsulation method used by other protocols

• Two methods:LLC/SNAP—(Logical Link Control/Sub-Network Access Protocol)

VC Multiplexing—(Virtual Circuit Multiplexing)

RFC 1483 Multiprotocol Encapsulation over ATM AAL5

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ATM Internetworking

• Routing Table maps final destination to next hop network address

• Address Resolution table maps next-hop network address to ATM address—setup manually by network administrator

• Signalling creates ATM VC between routers

ATMNetwork

DA-138.20.10.45

Routing TableRouting Table

AddressAddressResolutionResolution

TableTable 138.20.10.X

138.20.1.1 138.20.1.2

RFC 1483—Example

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ATM Internetworking

• LIS—Logical IP subnet—an IP subnet

• ARP Server—maintains IP address to ATM address mappings

• One ARP Server per LIS

• No cut-through to alleviate router hops

RFC 1577—Classical IP and ARP over ATM

LIS 1LIS 1 LIS 2LIS 2

ARP ServerARP ServerSubnet 2Subnet 2

ARP ServerARP ServerSubnet 1Subnet 1

ATMNetwork

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ATM Internetworking

• Routing table maps final destination to next-hop

• ATM ARP Server maps next-hop IP address to ATM addresses

• Signalling creates VC and data is passed

RFC 1577—Example

ATMNetwork

DA–138.20.10.45

Routing TableRouting Table

138.20.10.X

138.20.1.1 138.20.1.2

ARP ServerARP Server

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Next Hop Resolution Protocol

• Allows direct connections between LIS’s across cloud (LIS = Logical IP Subnet)

• Next hop requests passed between Next Hop Servers (NHS)

NHRPResponse

Next Hop Server

NHS1

NHS2 NHS3

NHS4

LIS 1 LIS 2 LIS 3 LIS 4

Direct ConnectionNHRPQuery

ATMNetwork

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ATM Internetworking

• Hides ATM to upper layers

• Makes ATM look like Ethernet/Token Ring

• Supported in NICs, LAN switches, ATM routers

• Allows ATM hosts connectivity with legacy LANs

Emulated LAN (ELAN) Segment

Today’s Physical LAN Segment

ATM Network

LANE 1.0

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Why ATM LAN Emulation (LANE)?

• Standards-based Virtual LAN (VLAN) support over ATM

ATM-attached hosts can be in several VLANs at once

• No disruption to current protocols and applications

• Integrates desktop LANs with ATM-attached serversMost users can stay on switched Ethernet or Token Ring

• Evolution pathCan utilize high-speed advantages of ATM now

Can exploit ATM QOS and service integration benefits in future

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ATM InternetworkingLANE—Basics

• Uses SVC’s to establish conversations

• Uses RFC 1483 to transport LAN traffic

BUS—Broadcast andUnknown Server forData FloodingATM

LES—LAN EmulationServer for AddressResolution

LECS—LAN EmulationConfiguration Serverfor Initialization

LEC—LAN Emulation Client

LAN Emulation

Phy Phy Phy Phy

SSCOPSSCOP

Q.2931Q.2931

NNI Convg

P-NNI

TCP

IP

SSCOPSSCOP

Q.2931Q.2931

SSCOP

Q.2931

NNINNI Convg Convg

P-NNIP-NNI

SSCOPSSCOP

Q.2931Q.2931

ATM Switch ATM Switch ATM Host/Router

AAL 5 AAL 5

RFC 1483 Encapsulation

AAL 5

ATM ATM ATM

Phy

ATM

Phy

ATMPhy

UNISignal-

ing

ATM Routing (P-NNI Protocol)

Virtual LANs (LAN Emulation)

Native Mode Routing Protocols

NNISignal-

ing

UNISignal-

ing

ATM Host/Router

TCP

IP

RFC 1483 Encapsulation

AAL 5

ATM

Phy

MACMAC

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LANE—Fully Configured

LECS LES BUS

Data Direct VCs

Cisco Specific

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Routing Contains Broadcasts

• Restores processor performance

• Routes unicast between Virtual LANs

ARPARP

SAPSAP

ZIPZIPOSPF

OSPFRIPRIP Broadcasts/Multicasts

Per Second

Broadcasts/MulticastsPer Second

ARPARP ZIPZIPRIPRIP OSPFOSPF SAPSAP

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LANE/VLAN InternetworkingWithin ELAN

Layer 2 Switching

ATM Switch ATM Router

Between ELANs

Layer 3 Switching

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LUNIv2

• Better efficiencyReduced VC consumption via optional LCC multiplexing

Optional, more efficient distribution of multicast

• Better use of ATM QoSABR and signalling 4.0 features

Supports emerging IEEE 802.1q/p Class of Service (CoS)

• Used within MPOA

• LNNI with redundancy still in-progress

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ATM Internetworking

Resultant DirectResultant DirectCut-Through between Cut-Through between

Different VLANsDifferent VLANs

MPSMPS

MPC

• For seamless transport of layer 3 protocols across ATM networks

• Goes beyond LANE by allowing direct ATM connectivity between hosts in different subnets

• Architecture consists of edge devices and route servers

• MPC—MPOA client—edge device

• MPS—MPOA server—route server

MPOA—Multi-Protocol over ATM

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MPOA for Inter-VLAN “Cut-Through”

Resultant DirectCut-Through Between

Red and Blue

1. Initially packets routed between Emulated LANs (VLANs)

2. L3 cut-through forwarding info given to edge devices

3. Inter-VLAN traffic via resultant direct “cut-through” connection

Use this L3 Cut-Through

for Red to Blue

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MPOA Goals

• Enable L3 protocols to exploit ATM

• Direct VCs between devices on different subnets

Access to ATM QOS; L3-to-ATM QOS integration

• Other MPOA goalsSeparate forwarding from route calculation functions

Benefit: Lower-cost L2/L3 forwarders vs. a full router in LAN switches

Require no changes in legacy-attached hosts

Leverage/integrate work by other groups (e.g. LANE, IETF, IEEE)

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MPOA Service Basics (Phase 1)

MPOA Server (MPS)Config Server Initialization

(Uses LECS)

Connectionless Unicast Forwarding

MPOA Clients (MPC)

Default Forwarder

Address Resolution and Can Initiate theForwarding of Infoto MPOA Clients

Route Server

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MPOA—Query and Response

ATMNetwork

Subnet A

MPOA Server

Edge Devices

OSPF, EIGRP, etc

MPOA Server

MPOA Server

MPOA Queryand Response

Resultant DirectCut-Through VC

Emulated LAN BEmulated LAN BEmulated LAN AEmulated LAN A

Subnet B

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MPOA—Router Initiated

ATMNetwork

Subnet A

MPOA Server

Edge Devices

OSPF, EIGRP, etc

MPOA Server

MPOA Server

Emulated LAN BEmulated LAN BEmulated LAN AEmulated LAN A

Subnet B

Use thisL3 Cut-Through

for A to B

‘MPOA Trigger’

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MPOA: LAN or WAN?

• Uses LANE for intra-VLAN connectivity

• No QoS or granular IP Multicast support

• Result: Less efficient use of WAN bandwidth

• Options more suitable: RFC-1577/NHRP, Tag/MPLS, RFC-1483 bridging

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Approaches to ATM Multicast

• Some applications require a “connectionless” multicast/broadcast service from ATM (e.g. ARP)

• AAL 5 cannot handle intermixing of cells!

Multicast Server Meshed Point-to-Multipoint

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PIM to ATM FlowsReceives only

selectedvideo feeds

Receives onlyrequested feedspt-mpt VCCs for PIM info

and routing updates(Static Map)

HeadendRouter

PIM driven pt-mptVCC for Group 1

PIM driven pt-mptVCC for Group 2

Group 1

Group 2

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Goal: QoS Support over ATM Backbone

QOS Request QOS Guarantee

End-to-End ApplicationEnd-to-End Application

““Middleware” — Network Layer ProtocolsMiddleware” — Network Layer Protocols

QOS Request QOS Guarantee

Routers LAN SwitchingATM SwitchesATM Switches

ATM Host

Ethernet/ Token Ring HostEthernet/ Token Ring Host

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Video over ATM OptionsVideo StreamVideo Stream (MPEG, M-JPEG, H.323, other)

LAN Emulation

IPIP

MAC MAC ProtocolsProtocols

ATMATM AAL5

Native Mode

IPIP

ATMATM AAL5

CircuitCircuitEmulationEmulation

ATMATM AAL1

Circuit Emulation

ATMATM AAL1/5

Video over ATM

CBR UBRUBR/ABR

/VBRUBR/ABR

/VBR

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Benefits Large Routed Backbones

• Layer 2 ATM core with routers

• Signalling performance issues

• All routers are neighbors

• 1 link failure = N2 peer failures

• Scalability is limited

• Tag switching core with tag routers

• Tag switches are routing peers

• All packets tagged—per edge or prefix

• Minimizes signalling overhead

• Increased scalability

Without Tag SwitchingWithout Tag Switching With Tag SwitchingWith Tag Switching

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Tag Switching Operation

3. Packets tag switched through network

2. Tag Edge Router (TER) applies tags to all packets

4. Tag edge router removes tags and forwards

1a. Routing protocols determine reachability (e.g. OSPF, EIGRP)

1b. Tag Distribution Protocol (TDP) assigns tags to destinations

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Tag Switching and QOS Overview

• QoS-tag optionsPrecedence tagging (CoS)

RSVP flows individually tagged

• QoS-tag operation basics

Initial packet QoS classification

Tag applied based on classification

Tag switched through network

Traffic Elasticity

Bandwidth

E-MailE-Mail

FTPFTP

Video

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Tag Switching and ATM Services

• ATM services for real-time services

PNNI/UNI signalling

Voice trunking

Circuit Emulation (CES)

• Tag switching for data trafficOffloads signalling-intensive traffic

Reduces call set-up dependencies

Co-Existing on Same Platform! (Ships in Night)

ATM

IPFR

ATM

FR

IP IP

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Tag Switching Standardization

• Multiprotocol Label Switching (MPLS) is the IETF working group for Tag Switching and similar proposals

• Two main proposals - Tag Switching and ARIS - are very similar

• Cisco is proceeding with Tag development now, software upgrades to full MPLS standard when it exists

• Tag, ARIS, Internet-Drafts are widely available, anyone can implement them

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Voice Integration

• Success of ATM will depend in part on fulfilling promise of multiservice integration

• Migration of corporate and service provider voice to ATM backbone results in cost savings

• Standards exist and hardware is becoming available

• Looking forward, Voice and Telephony over ATM (VTOA) and Voice over IP will co-exist

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Voice Architecture

ATM(Campus or WAN)

Voice Server(enables ‘Virtual’ PABX)

‘Legacy’PABX

Implements VTOA Interworking

Implements VTOA Interworking

ATM-connected PABXImplements VTOA

Analog/Digital

E1

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SecurityOptions at Layers 2 and 3

Problem:

Solution:

Firewall

UntrustedHost

ATM VCC

No Layer 3Screening Possible

Layer 3 Screening PossibleIPsec will play an important role

TrustedHost

Mustimplementscreening

Closed User Groups and NSAP filtering a solution for closed communities (VPNs)

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The Wonderful World of AcronymsAAL—ATM Adaptation Layer

AAL1—See CBRAAL1—See CBR

AAL2—See VBR

AAL3/4—See UBRAAL3/4—See UBR

AAL5—See ABR

ABR—Available Bit RateABR—Available Bit Rate

API—Application Programmer Interface

B-ICI—B-ISDN Inter-Carrier InterfaceB-ICI—B-ISDN Inter-Carrier Interface

BUS—Broadcast and Unknown Server

CAC—Connection Admission ControlCAC—Connection Admission Control

CBR—Constant Bit Rate

CCITT—Consultative Committee for International Telephony and TelegraphCCITT—Consultative Committee for International Telephony and Telegraph

CDVT—Cell Delay Variation Tolerance

CLP—Cell Loss PriorityCLP—Cell Loss Priority

CLR—Cell Loss Ratio

CS—Convergence SublayerCS—Convergence Sublayer

EFCI—Explicit Forward Congestion Indicator

ELAN—Emulated LANELAN—Emulated LAN

GCRA—Generic Cell Rate Algorithm

GFC—Generic Flow ControlGFC—Generic Flow Control

HEC—Header Error Check

IISP—Interim Inter-Switch Signalling ProtocolIISP—Interim Inter-Switch Signalling Protocol

ILMI—Interim Local Management Interface

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The Wonderful World of AcronymsIPD—Intelligent Packet DiscardIPD—Intelligent Packet Discard

LANE—Local Area Network Emulation

LEC—LAN Emulation ClientLEC—LAN Emulation Client

LES—LAN Emulation Server

LECS—LAN Emulation Configuration ServerLECS—LAN Emulation Configuration Server

LIS—Logical IP Subnet

MBS—Maximum Burst SizeMBS—Maximum Burst Size

MCR—Minimum Cell Rate

MCTD—Maximum Cell Transfer DelayMCTD—Maximum Cell Transfer Delay

MPC—MPOA Client (aka Edge Device)

MPOA—Multi-Protocol Over ATMMPOA—Multi-Protocol Over ATM

MPS—MPOA Server (aka Router Server)

NNI—Network-to-Network InterfaceNNI—Network-to-Network Interface

OC—Optical Carrier

PCR—Peak Cell RatePCR—Peak Cell Rate

PMD—Physical Media Dependent

PNNI—Private Network-to-Network InterfacePNNI—Private Network-to-Network Interface

PTI—Payload Type Identifier

PVC—Permanent Virtual CircuitPVC—Permanent Virtual Circuit

Q.SAAL—aka Q.2100—Signalling ATM Adaptation Layer

RFC1483—Multiprotocol Encapsulation over AAL5RFC1483—Multiprotocol Encapsulation over AAL5

RFC1577—Classical IP and ARP over ATM

RM—Resource ManagementRM—Resource Management

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The Wonderful World of AcronymsSAR—Segmentation and Reassembly

SDH—Synchronous Digital HierarchySDH—Synchronous Digital Hierarchy

SONET—Synchronous Optical Network

STM—Synchronous Transport ModeSTM—Synchronous Transport Mode

STS—Synchronous Transport Signal

SCR—Sustained Cell RateSCR—Sustained Cell Rate

SVC—Switched Virtual Circuit

SSCOP—Signalling Specific Convergence ProtocolSSCOP—Signalling Specific Convergence Protocol

TC—Transmission Convergence

UBR—Unspecified Bit RateUBR—Unspecified Bit Rate

UNI—User-to-Network Interface

UPC—Usage Parameter ControlUPC—Usage Parameter Control

VBR-NRT—Variable Bit Rate-Non-Real Time

VBR-RT—Variable Bit Rate-Real TimeVBR-RT—Variable Bit Rate-Real Time

VC—Virtual Circuit (or sometimes Virtual Connection)

VCC—Virtual Channel ConnectionVCC—Virtual Channel Connection

VCI—Virtual Channel Identifier

VC Switch—Virtual Circuit SwitchVC Switch—Virtual Circuit Switch

VP—Virtual Path

VPC—Virtual Path ConnectionVPC—Virtual Path Connection

VPI—Virtual Circuit Identifier

VP Switch—Virtual Path SwitchVP Switch—Virtual Path Switch

VS/VD—Virtual Source/Virtual Destination

Documents

Introduction to ATM 1 NW97_EMEA_314. 2 Characteristics of ATM Uses small, fixed-sized cells Connection-oriented Supports multiple service types Applicable