Atm Principles

ATM PrinciplesATM Principles

V1.0

Data Customer Service Dept.

For Internal Use Only▲

<Confidential and Proprietary Information of ZTE Corporation ><Confidential and Proprietary Information of ZTE CORPORATION>

Internal Use Only▲

Course Objectives

• Grasp the Basic Concept of ATM• Grasp the Connection Type of ATM• Have A General Knowledge of ATM Cell Structure• Grasp ATM Cell Switching Principles• Have A General Knowledge of ATM Service Types




Course Outline

• Chapter 1 ATM Overview

• Chapter 2 Cell and Cell Switching

• Chapter 3 ATM Connection Type

• Chapter 4 ATM Service Adaptation and Service Type




Course Content

• Chapter 1 ATM Overview Section 1 ATM Features

Section 2 ATM Network Architecture

Section 3 ATM Protocol Reference Model


<Confidential and Proprietary Information of ZTE CORPORATION>

Late 1980s, telecom initiates a concept of ATM, aiming to integrate

voice, data and image via telecommunication networks.

In 1991, ATM is selected as the first choice to realize B-ISDN by

ITU-T.

Purpose of B-ISDN Use a uniform network to support current and future network services

Provide reliable network connection, valid network bandwidth and quality

of service (QoS).

the first choice to realize B-ISDN ATM: Asynchronous Transfer Mode

Include multiplexing, switching and transferring system

Brief Introduction of ATM



ATM Features

Statistical Time Division Multiplex, increase the channel utility

Apply small fixed-length cell (53 bytes, easy for hardware switching , high-speed,

large capacity)

Connection oriented (QoS guaranteed, low latency, support real-time service)

Support multiple service types (DDN, FR, Video, Voice, IP etc.)

Comprehensive flow-control measures (Traffic Engineering)

Cells

Voice

Data

Image



Synchronous Time Division Multiplex

Asynchronous Time Division Multiplex（ Statistical Multiplex）S

ynchronous T

ime

Divisio

n Multiplex

Synchron

ous Tim

e D

ivision M

ultiplex

Synchron

ous Tim

e D

ivision M

ultiplexS

ynchronous T

ime

Divisio

n Multiplex

Frame HeaderFrame Header

Statistical Multiplex



ATM Network

Connection oriented, having N2 Problem

Routing based upon Data-link Layer and VPI/VCI or identifier

Have congestion notification and cell-loss priority indication

QoS guarantee, real-time service guarantee

Relocation of ATM Network standardization process

IP Network

Connectionless, no N2 problem

Routing based upon Network Layer

and IP address

QoS guarantee

Comparison of ATM Network and IP Network



ATM Technical Features Summary

Integrate SwitchingIntegrate Switching

Integrate TransmissionIntegrate Transmission

Integrate ServiceIntegrate Service

Integrate ManagementIntegrate Management




Course Content






Network Architecture: assembly of network layer and protocolsProtocol Layer: to reduce the complexity of networks, network adopts layered

or hierarchical design. Each layer is established based upon the lower layer and

provide service to upper layer, but shield the details. Layer N of Source Host is

only able to communicate with peer layer of destination, the rules is called

Layer N protocol.

Layer N

Physical Media

Layer N-1

Layer 2

Layer 1 Layer 1

Layer 2

Layer N-1

Layer N

Host A Host BLayer N protocol

Layer N-1 protocol

Layer 2 protocol

Layer 1 protocol

Network Architecture



Physical Layer

Data-link Layer

Network Layer

Transport Layer

Session Layer

Presentation Layer

Application Layer

Internet Protocol Layer

TCP/DUP

OSI

TELNET

FTP

WWW

IPPHONE

TCP/IP

Physical Layer

Data-link Layer

Packet Layer

Upper Layer Protocol

X.25

Physical Layer

Q922 Core Layer

Upper Layer Protocols

Frame Relay ATM

Physical Layer

AAL LayerATM Layer

Upper Layer Protocols

ATM Network Architecture




Course Content






Upper Layer

ATM Layer

Physical Layer

User PlaneControl Plane

Plan

e M

anag

emen

t

Upper Layer

Layer

Man

agem

entATM AAL

ATM Protocol Reference Model

Management Plane



User PlaneTransfer user’s message, including service related protocols, data,

voice and video information.

Control PlaneUsed for signaling information, including establishing and tearing

down connections functions etc.

Management PlaneUsed to maintain network and execute operation. Layer

management is used to intra-layer management and plane is used to information interaction and management.

Planes and Functions of ATM protocol Reference Model



AAL Layer CS CPCS， SSCS

SAR Segment and Assembling

UNI

ATM Layer Generation and extracting of header VPI/VCI switching of Cell Multiplex and breakdown of Cell

Cell Rate Decoupling HEC Cell Delineation Physical Transmission Transmission frame AdaptationLayer Convergence Generation/Recovery of Transmission frame

Physical Media Bit timed, physical layerCPCS—common part convergence sub-layer; SSCS—service-specific convergence sub-layer

Sub-Layer and Functions ATM protocol Reference Model



AAL

ATM Layer

Physical Layer

Physical Layer:

Provide transmission channel to ATM cell, add trans

mission cost to cells from ATM layer to form continuou

s bit stream and get the valid cell from bit stream receiv

ed from physical media to transfer to ATM Layer.

Physical Layer includes two sub-layers:

TC: Transmission Convergence

---Framing

---HEC

PMD: Physical Media Dependent

---Physical Media Coding

ATM protocol Reference Model--Physical Layer



ATM Layer:

ATM Layer is above Physical Layer, making use

of the service provided by Physical Layer and

communicate with peer layer using cell as

message unit and provide services to AAL. ATM

Layer only identifies and processes cell header,

which is unrelated to physical media type and the

services being transferred by physical layer either.

Three Functions

Adding and removing cell header

Cell forwarding, GFC (Generic Flow Control )

Cell Multiplexing and de-multiplexing of various

connections

AAL

ATM Layer

Physical Layer

ATM protocol Reference Model--ATM Layer



GFC: Generic Flow Control, UNI Cell needs it

VPI/VCI: virtual path identifier / virtual channel identifier

PTI: Payload type identifier, 3bit

1. User /Control data2. Congestion3. Backward Cell

CLP: Cell Loss Priority

HEC: Cell header Error Check 8 bit CRC

ATM NNI Cell

48 BytePayload

VPI (12)VCI (16)

PTI CLP

HEC

ATM UNI Cell

48 BytePayload

GFC (4) VPI (8)

VCI (16)PTI CLP

HEC

ATM Cell (53 bytes)=5 bytes cell header+ 48 bytes Payload

ATM protocol Reference Model--ATM Layer



AAL is divided into two sub-layers CS: Convergence Sub-layer SAR: Segmentation and Reassembly

ATM Adaptation Layer (AAL) Above ATM Layer, AAL is related to

service, and process various services in

different ways, but it will divide the upper

layer information flows (various in length

and rate) into 48 bytes ATM SDU and

meanwhile reassembly ATM-SDU of

ATM Layer and retransmit to upper layer.

ATM Reference Model--AAL

AAL

ATM Layer

Physical Layer




Course Content

• Chapter 2 Cell and Cell Switching Section 1 Generation of ATM Cell

Section 2 Introduction of VC and VP

Section 3 ATM Cell Switching



ATM Payload Processing

TCP

IP

LLC/SNAP Data-link Layer

AAL

ATM

PHY

TCP Packet

IP Data

Add 5 bytes Cell Header ( VPI/VCI and CLP etc.)

App DataTCP HeaderIP HeaderLLC

App DataTCP HeaderIP Header

App DataTCP Header

CS

SAR

App DataTCP HeaderIP HeaderLLCcell tax

Divided into 48 bytes Cell, encapsulated into PDU

Data Transmission Format Conversion (STS, STM, DS)

Physical Media (MMF, SMF, STP, UDP,）

Generation of ATM Cell

RFC1483 defines two protocols encapsulated IP into AAL5: LLC/SNAP and VC-MUX



TokenRing

Public UNIB-ICI

UNI

NNI

NNI

NNI

ATM Public Network

ATM Private Network

UNI = User-to-network interface (public network UNI and Private network UNI) NNI = Network-to-network interface, generally is the interface of two switches B-ICI=Interface between two public networks, interface for two ATM networks for

different carriers. Cell header is changed with counterpart.

ATM Network and Interface



Destination Address

Source Address Data

Frame Check

PayloadCell

Header

packet

Cell

PayloadCell

Header

PayloadCell

Header

PayloadCell Header

SARSegmentation and Reassembly

Segment in initial point and reassembly in destination point

Packet-to-Cell Conversion




Course Content






ATM Physical Connection

VCC

A VP contains multiple VCs

A VCC contains multiple VPs

VC is the logical path for different ends of ATM Networks

VC

VC

E3 OC12

VP

VP

Connection Identifier = VPI/VCI

Virtual Path& Virtual Channel (VP&VC)

VCC: Virtual Channel Connection VP: Virtual Path VC: Virtual Channels




Course Content






2/91

ATM switches and resolves value of VPI/VCI Value of VPI/VCI for each port is unique

4/5

2/9

3

2

6/42/94/5

6/4

2/9

2

1

3

VPI/VCIPort

4/5

2/9

2/9

6/4

2

1

3

1

VPI/VCIPort

Input Output

1

ATM Switching



VCI 1 VCI 2 VCI 3 VCI 4

VPI 2VPI 3VPI 1

VPI 2

VPI 3

VPI 5

VPI 1

VPI 4

Port 1

Port 2

Port 3

VCI 1

VCI 2

VCI 1

VCI 2

VP Switching／ Cross Connection

VC Switching / Cross Connection

VCI 3

VCI 4

VCI 1

VCI 2

VP and VC Switching



Hop by hop forwarding shown above is Cell forwarding.

Virtual Channel Connection (VCC)

Virtual Path Connection (VPC)

VPSwitching

VC Switching

VCSwitching

NNI NNI

VPI = 2VCI = 44

VPI = 1VCI = 1

VPI = 26VCI = 44

VPI = 20VCI = 30

UNI UNI

Virtual Channel (VC) and Virtual Path (VP)



ATM SwitchingATM Switching

PPHHYY

AATTMM

Port 1

PPHHYY

AATTMM

Port 2

PortPort VPIVPI VCIVCI

11 11 5151

22 33 3939

ATM Layer

ATM SwitchingATM Switching

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

ATM Layer Completes Cell Switching




Course Content

• Chapter 3 ATM Connection Type



Connection Types of ATM: PVC (Permanent Virtual Circuit) SVC (Switching Virtual Circuit) Soft PVC (Soft-Permanent Virtual Circuit)

Connection Types

Connection-Oriented: ATM Cell Switching

VC = S1, S4, S7, S8

Data arrives via another path

S2 S6

S4 S7

VC

S1 S8S3 S5



Need manually update VPI/VCI table of network devices by administrators

A

B

D

C

Input Output

1 3/3 3 0/22 1/5 3 1/41 6/4 3 2/93 2/9 1 6/4

Input OutputPort VPI/VCI Port VPI/VCIPort VPI/VCI Port VPI/VCI

1 2/9 3 4/5

2 5/2 4 1/5

1 6/4 3 2/9

3 2/9 1 6/4

Input Output

Port VPI/VCI Port VPI/VCI

1 4/5 2 1/6

2 5/2 1 2/9

1 6/4 3 2/9

3 2/9 1 6/4

2/9

5/2

1/0

1/6

1/5

4/51/4

4/3

Input Output

Port VPI/VCI Port VPI/VCI1 1/6 2 4/3

3 1/4 4 1/0

1 6/4 3 2/9

3 2/9 1 6/4

1

2

4 2

3

32

4

12

3

Permanent Virtual Circuit (PVC)



Signaling establishes connections dynamically

B

D

1

2

4 1

3

3

2

4

12

C

Input Output


1 6/4 2 2/9

2 2/9 1 6/4

Input OutputPort VPI/VCI Port VPI/VCI

2 5/2 1 2/9

1 6/4 3 2/9

3 2/9 1 6/4

Input Output

1 2/9 3 4/5

1 6/4 3 2/9

3 2/9 1 6/4

Port VPI/VCI Port VPI/VCIInput Output


1 6/4 3 2/9

3 2/9 1 6/4

A

3

1

Switching Virtual Circuit (SVC)(1)

NNI Signaling

UNI Signaling

UNI Signaling



Transfer data on the latest established connections

B

D

1

2

4 1

3

32

412

C


1 2/9 3 4/5

1 6/4 3 2/93 2/9 1 6/4

A

3


1 6/4 3 2/93 2/9 1 6/4

1 2/9 3 4/5


2 5/2 1 2/91 6/4 3 2/93 2/9 1 6/4

1 4/5 2 1/6


1 6/4 3 2/93 2/9 1 6/4

1 1/6 2 4/3

1

Switching Virtual Circuit(SVC)(2)

NNI Signalin

g

UNI Signaling

UNI Signaling



Signaling release connections dynamically

B

D

1

2

4 1

3

32

4

12

C


1 6/4 3 2/9

3 2/9 1 6/4


2 5/2 1 2/9

1 6/4 3 2/9

3 2/9 1 6/4


1 2/9 3 4/5

1 6/4 3 2/9

3 2/9 1 6/4


1 6/4 3 2/9

3 2/9 1 6/4

A

31

Switching Virtual Circuit(SVC)(3)

NNI Signaling

UNI Signaling

UNI Signaling



SVC is established based upon PVC on UNI and dynamically established on NNI

Input OutputInput Output

B

D

1

1

2


1 6/4 3 2/9

3 2/9 1 6/4


2 5/2 1 2/9

1 6/4 3 2/9

3 2/9 1 6/4


1 2/9 3 4/5

1 6/4 3 2/93 2/9 1 6/4


1 6/4 3 2/9

3 2/9 1 6/4

3C

A

1 1/6 2 4/3

1 2/9 3 4/5

1

2

1

3

3

Soft PVC (Soft-Permanent Virtual Circuit)

NNI Signaling

UNI Signaling

UNI Signaling




Course Content

• Chapter 4 ATM Service Adaptation and Service Type Section 1 AAL Service Adaptation and Service Classification

Section 2 ATM Service Type Introduction

Section 3 IPoA Protocol and RFC1483



AAL Service Adaptation

In ITU-T I.362 Recommendation, services are classified into A, B,

C and D according to the following listed features:

Class A Service, has defined AAL1 protocol Class B Service, has defined AAL2 protocol Class C and D Services apply AAL3/4 protocol, and later simplified AAL3/4, defined AAL5 (C) protocol.

Class A Service

Class B Service

Class C Service

Class D Service

Source and Sink relation Timing

Required Required Not Required Not Required

Baud rate Constant Variable Variable Variable

Connection Mode Connection-Oriented

Connection-Oriented

Connection-Oriented

Connectionless



Class A:

Constant Bit Rate, Connection-Oriented service, requires timing between

source and destination sites

Typical service types include 64kbit/s voice and constant bit rate video service

As this type of service is similar to conventional circuit switched network, thus

called CES (Circuit Emulation Service).

Class B:

Variable Bit Rate, Connection-Oriented service, requires timing between

source and destination sites

Typical service is VBR compact video service

Class C and D:

VBR data service, not requires timing between source and destination sites

Class C is Connection-Oriented while Class D is Connectionless

AAL Service Classification



1 byte

5 ByteHeader

47 BytePayload

3 bytes

5 ByteHeader

45 BytePayload

5 ByteHeader

44 BytePayload

4 bytes

5 ByteHeader

48 BytePayload

no cost

AAL-1 Cell Tax AAL-2 Cell Tax

AAL-3/4 Cell Tax AAL-5 Cell Tax

AAL Cell Cost (Cell Tax)




Course Content






Service Standards Traffic Descriptor

QoS Parameters

Service Types Constant Bit Rate (CBR)

Variable Bit Rate (VBR)

Unspecified Bit Rate (UBR)

Available Bit Rate (ABR)

ATM Service Types



protocol

protocol

Protocol• Traffic Descriptor

Peak cell rateSustainable cell rateMaximum burst size Minimum Cell Rate

• Quality of Service (QoS)DelayCell Loss

ATM Network

ATM Service Standards



PCR: Peak Cell Rate

---Max data connection rate without data loss

SCR: Sustainable Cell Rate

---ATM cell average throughput in application process

MBS: Maximum Burst Size

---Maximum burst size of Cell

MCR: Minimum Cell Rate

---potential rate of application process

Traffic Descriptor



QoS Delay

MCTD (Maximum Cell Transfer Delay )

---Cell transfer time from one end to the other end of network

CDVT (Cell Delay Variation Tolerance)

---Cell line distortion caused by transmission

Cell Loss

LCR (Cell Loss Ratio)

--- Cell Loss Ratio caused by network congestion

Quality of Service



QoS

Traffic Descriptor

Application

CBR: Constant Bit Rate

Real-Time Voice and Image

Low High

Receiving State

Cell DelayCell Loss Rate

PCR

Peak Cell Rate

ATM Service Types--CBR



VBR-RT/VBR-NRT: Variable Bit Rate

QoS Traffic Descriptor

Low High

Receiving State

Cell Delay(Non-Real-Time)Cell Delay (Real-Time)

Peak Cell Rate

Sustainable Cell Rate

Maximum Burst SizeCell Loss

Packet-based Voice and Image

Application

ATM Service Types--VBR-RT/VBR-NRT



QoS Traffic Descriptor

UBR: Unspecified Bit Rate

Application

Data Transfer

Low High None

Receiving State

Cell LossCell Delay

ATM Service Type--UBR



ABR: Available Bit Rate

Apply CCS (Congestion Control Scheme )

QoS

Low High

Traffic Descriptor

Peak Cell Rate

Minimum Cell Rate

Receiving State

Cell Loss Cell Delay

LAN Data Interconnection

Application

ATM Service Type--ABR




Course Content






IPoA Protocol

IPOA(IP Over ATM) is a type of technology that transfer IP data packet over ATM-LAN.

It is a regulation that defines establishing connection between ATM terminals over ATM Network, especially the SVC (Switched Virtual Circuit) to perform IP data packet communication.



RFC1483R (Routing Encapsulation): describe the intern

et service (IP packet) carried on ATM AAL5 PDU.

RFC1483B (Bridge Encapsulation): describes that ATM

AAL5 PDU carries network internal (MAC Frames) service.

Two Types of Encapsulation in RFC 1483



RFC 1483R Protocol Structure



RFC 1483B Protocol Structure



Summary

What’s basic concept of ATM? Where is ATM in protocol stack? How many parts does ATM Cell consisted of? Wh

at are they? How does ATM perform Cell switching? How many service types does ATM include? What

are they?

Atm Principles

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