02 ATM Principle

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Wireless Curriculum Development Section

ISSUE ORI000008 ATM Principle

4.2


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Confidential Information of Huawei.No Spreading without Permission. Security Level: Internal

Course Outline

Overview

Basic Concepts of ATM

ATM Protocol & Service Type

Basic Concepts of IPOA

ATM in CDMA2000 BSS


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To provide a high-speed , low delay

multiplexing and switching network to any type of

user traffic , such as voice support , data,or videoapplications.

Why do we need a new technology?


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What is ATM?

ATM for Telecommunications is Async hrono us Trans fe r Mode , (not Automatic Teller Machine!).

ATM is a technology that has transport, swi tch ing , ne twork

management , and customer services built into it right from the start.

In general, ATM means that traffic is carried in small, fixed-lengthpackets called cells.

A technology that integrates advantages of circuit switch and packet

switch .

ATM can support any type of user services, such as voice, data , or

video service .


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ATM Overview

53byte fixed length cell= 5Bytes cellheader+48Bytes payload.

ATM must set up virtual connection beforecommunication.

ATM network will confer with terminal onparameter of QoS before the connection isset up.

Contract

5-BytesHeader

48-BytesPayload


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Connectionless & Connection-oriented

Connectionless: Every packet istransferred from different routes, sothe receiving order of packetsdoesnt possibly depend on thesending order.

Connection-oriented : All packetsare transferred from the sameroute , so the receiving order ofpackets depends on the sendingorder. Time delay is fixed.


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Traditional Switch Models Characteristic

Circuit Switching Data is sent from the same route, so time delay is fixed High-speed switching Fixed rate

Packet Switching Support multi-rate switching

Take full advantage of bandwidth/waste of bandwidth Time delay is not fixed


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ATM Switch Models Characteristic

Bandwidth will be shared and statisticallymultiplexed, any users cell will not be sendperiodically.

Many types of service can be transferred in thesame time with high QoS.

Fixed length cell, so switch can be controlled byhardware and high-speed switching is easy to be

realized.


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Course Outline

Overview




ATM in CDMA2000 BSS


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ATM Cell


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ATM Cell

GFC ( Generic Flow Control): It is intended for control of a possible bus

system at the user interface and is not used at the moment.

VPI ( Virtual Path Identifier): The VPI contains the second part of the

addressing instructions and is of higher priority than the VCI.

VCI ( Virtual Channel Identifier): VCI in each case indicates a path section

between switching centers or between the switching center and the subscriber.

PTI ( Payload Type Identifier): Indicates the type of data in the information

field.

CLP ( Cell Loss Priority): Determines whether a cell can be preferentially

deleted or not in the case of a transmission bottleneck.HEC ( Header Error Control): Provided in order to control and, to some

extent, correct errors in the header data that may occur. The HEC is used to

synchronize the receiver to the start of the cell.


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VP and VC

Why two fields?

Consider VPI as a bundle of virtual

channels. (256 VPI on one link)

The individual virtual channels have

unique VCIs. The VCI values may

be reused in each virtual path.


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Port 1 VPI=2 VCI=37

VPI=3 VCI=39

NNI

UNI

UNI

ATM Cell Switching

ATM Switch

Port VPI VCI1 2 37

2 1 51Port 2

Port 1 ATM Switch

Port VPI VCI1 1 512 3 39

Port 2

ATM TerminalUser B

User A

ATM Network Node

Cell and usersdata changeeach other

VPI=1 VCI=51

ATM Network Node

ATM TerminalCell and usersdata changeeach other


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ATM Connections


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ATM Virtual Connection

UNI cellVPI =1VCI =1

UNI cellVPI =20VCI =30

NNI cellVPI =26VCI =44

NNI cellVPI =6

VCI =44 NNI cellVPI =2VCI =44

1

2

3

1

2

3

1

3 2

2

3 1

ATM Virtual ConnectionPort VPI VCI

1 26 442 2 44

Port VPI VCI

1 2 44

2 6 44

Port VPI VCI2 6 44

3 20 30

Port VPI VCI

1 1 12 26 44

A B

In order to exchange cells between A and B, several tables must be set up innetwork node where the cells passed. After these tables have been set up, all the

cells will be transferred along this route. This route is called Virtual Connection.


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Types of ATM Virtual Connection

According to the switching mode, ATMVirtual Connection can be classified :

VPC (Virtual Path Connection)

VCC (Virtual Channel Connection)

According to connection establishment,ATM Virtual Connection can be classified:

SVC(Switching Virtual Connection)

PVC(Permanent Virtual Connection)


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UNI cell

VPC and VCC

ATM terminal A C

ATM network node G UNI cell

NNI cell NNI cell VCswitching

VCC

VPC

VCC

UNI cell UNI cell

B D

For example: When E receives cells from A or B, which would betransferred to C or D, the VPI of these cells would be set touniform value in E. These cells would be received by G andswitched to F by VP switching. Then the cells will be delivered toC or D at F. It means that VPC has been set up between E and F,

whi l e VCC has been se t up among A, B , C and D.

E F

VPswitching

VCswitching


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Course Outline

Overview




ATM in CDMA2000 BSS


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ATM Sublayer Model

ATM Protocol Stack Model OSI Reference Model

User

PMD

TC

PHY

ATM

AALCS

SAR

Interfacemanage

ment

7 Application

6 Presentation

5 Session

4 Transport

3 Network2 Data link

1 Physical


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Two sublayers:

Transmission Convergence Sublayer (TC)transmission frame generation/recoveryProcessing HEC

cell delimitingtransmission frame adaptation

Physical Medium Dependent Sublayer(PMD)

Link codingNetwork physical medium

Function of ATM Physical Layer

AAL

ATM

PHY


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Cell switch

Quality of Service

Processing the cell header

Types of payload

Multiplexing /Demultiplexing ofdifferent connection cell

Function of ATM Layer

AAL

ATM

PHY


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Support services for user

Segment and reassemble

Complete the change betweenUser-PDU and ATM payload

Function of AAL layer

AAL

ATM

PHY


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Function of ATM AAL Overview

Function of ATM AAL:

Provide a high-speed,

low delay multiplexingand switching network

to support any type of

user service, such as

voice, data,or video

applications.

ATM Payload

ConstantBit Rate

DataBursts

VariableBit Rate

ATM Cell

Multiplexing

AAL SDU


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Types of AAL

In order to support different types of user services, there arefive types of AAL.

In Huaweis BSS, voice is transferred over AAL2 and restsignals are transferred over AAL5.

Service type A B C DBit rate constant variable variable variable

Real time YES YES NO NO

Connection mode Connection oriented connectionless

AAL AAL1 AAL2 AAL3/4 AAL5


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Service Types of ATM layer

CBR (Constant bit rate)

VBR-RT (Variable bit rate-real time)

VBR-NRT (VBR-non real time)

UBR (Unspecified bit rate)

ABR (Available bit rate)


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Service type in CDMA2000 BSS System

Variable bit rate real time( VBR-RT), such as voice

service in CDMA2000 BSS System. It is realized by

AAL2.

Variable bit rate non real time (VBR-NRT), such as

signaling and other service in CDMA2000 BSS System.

It is realized by AAL5.


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Course Outline

Overview




ATM in CDMA2000 BSS


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IPOA Protocal Stack

ATM network Physical layer

IP address is mapped to PVCor SVC

User application

ATM

AAL

IP

TCP/UDP

ATM

AAL

IP

TCP/UDP

IP packet is transferred toATM Payload

User application


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INARP in IPOA PVC Mode

Terminal A IP:192 .168 .1 .1

ATM Network

Terminal B IP:192 .168 .1 .2

PVC

Any IPOA terminal that wants to communicate with other terminalmust know the destination IP address. But how to know the IP address?PVC connecting the source and destination terminals should be set upfirst. For example: Terminal A must set up a PVC to B in order to knowthe IP address of B.


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ARP in IPOA PVC Mode

Terminal A will send InvATMARP information to request remote IPOA

client s (such as computer B) IP address. So does computer B.

Computer A IP:192 .168 .1 .1

ATM Network

Computer B IP:192 .168 .1 .2

PVC InvATMARP

InvATMARP

VPI VCI IP Address

1 33 . . .

XX YY . . .

VPI VCI IP Address

2 33 . . .

ZZ YY . . .


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Thereby, A and B establish the map table of IP address to PVC. Similarly, allthe IPs of the computers that answered the InvATMARP will be set to themap table.

Computer A IP:192 .168 .1 .1

ATM Network

Computer B IP:192 .168 .1 .2

PVC ACK

ACK

VPI VCI

1 33

XX YY

IP Address

192 .168 .1.2

xxx .xxx .xxx .xxx

VPI VCI

1 33

ZZ YY

IP Address

192 .168 .1.1

xxx .xxx .xxx .xxx


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For example: A will transfer a IP packet to B, and the IP packetwill be changed to AAL-PDUs first. When ATM layer receives AAL-PDU,it can find the PVC by map table and set VPI/VCI of ATM cell.Thereby, cells could be transferred to B by ATM network.

omputer A IP:192.168.1.1

ATM Network

Computer B IP:192.168.1.2

PVC ATM cell stream ATM cell stream

VPI VCI

1 33

XX YY

IP Address

192 .168 .1.2

xxx .xxx .xxx .xxx

VPI VCI

1 33

ZZ YY

IP Address

192 .168 .1.1

xxx .xxx .xxx .xxx


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Course Outline

Overview




ATM in CDMA2000 BSS

ATM i CDMA2000 BSS t L


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ATM in CDMA2000 BSS system LargeCapacity Configuration

ResourceManagement &

Packet ProcessingSubrack (CRPS)

IntegratedProcessing

Subrack (CIPS)

Optical fiber orseveral E1cables

BTS

BTS baseband frame

service/ signal-in-band AAL2 maintenance / signal-out-bandAAL5

Abis interface:signal-in-band/service AAL2

signal-out-band /maintenance AAL5 IPOAIf Abis interface is connected with several E1 cables,IMA mode will be adopted to transfer ATM cells.

BSC inside

Voice AAL2signal/data service:AAL5maintenance AAL5 IPOA

Connected to

MSC

Data ServiceProcessing

Subrack (CPMS)

Connected to

PDSN

Opticfiber

Opticfiber

Ethernetcable

cBSC

SwitchSubrack

GPS/Glonassreceiver

Opticfiber

IntegratedManagementSubrack (BAM)

ATM in CDMA2000 BSS System Small


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ATM in CDMA2000 BSS System SmallCapacity Configuration

several E1cables

BTS

BTS baseband frame

service/ signal-in-band AAL2 maintenance / signal-out-bandAAL5

Abis interface:signal-in-band/service AAL2

signal-out-band /maintenance AAL5 IPOAIf Abis interface is connected with several E1 cables,IMA mode will be adopted to transfer ATM cells.

BSC inside

Voice AAL2signal/data service:AAL5maintenance AAL5 IPOA

Connectedto MSC

Resource &PacketSubrack

IntegratedManagement

Subrack(BAM)

Connected to

PDSN

cBSC

GPS/GlonassReceiver

several E1cables or

Optic fiber

IntegratedProcessing

Subrack

Ethernetcable

LAN


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IMA Mode

PHY

IMA Group

PHY

PHY

PHY

IMA Group

PHY

PHY

Physical Link #1

Physical Link #0

Physical Link #2

Virtual ATM Link

If Abis interface is connected with several E1 cables, IMA mode will be

adopted to transfer ATM cells. In this way, cells of high speed ATM linkcould be transferred on several low speed physical links.

ATM Layer ATM Layer


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Summary

ATM Basics

ATM switching is cell switching,it has advantageof circuit switch and packet switch, connectionoriented .

ATM cell:53byte fixed length cell= 5Bytes cellheader+48Bytes payload

ATM switching

ATM switching has two types:VP and VC switch.

As a rule: only VPI has been changed in VPswitch,Both VCI and VPI have been changed inVC switch. VPI and VCI is only of effect betweenthe two ATM physical nodes.


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Questions

State ATM application in CDMA2000 BSSsystem?

What is the difference between SVC and PVC?

What is the difference between VP switchand VC switch?


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Documents

02 ATM Principle