Asynchronous Transfer Mode Project

Yuba Raj Khadka 1801T3090156

ABSTRACT

The demands for the communication of data and internet in today’s business

environment are springing up every day. The applications having high-bandwidth like

video conferencing and graphics applications calls for efficient and fast transfer of

data.

Today’s networks are running out of bandwidth. The network users are

invariably calling for more bandwidth than their network is capable of. It was 1980’s

when the researchers in the telecommunications company started to look into the

other technologies for the following generation of high speed transfer of data, voice

and video and for the development of broadband ISDN (Integrated Services Digital

Network).ATM (Asynchronous Transfer Mode) was developed as the result of this

research.

Unlike Ethernet, Token ring and FDDI, ATM is a different recent technology,

capable of transferring data, voice and video simultaneously over the same line. For

today’s incorporated network system, it has become one of the most promising

solutions.

This project gives you the comprehensive overview of an ATM including its

architecture, reference model, present status on the management of traffic and new

developments like MPLS as well as the related technologies using the very ATM

protocol.

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1 INTRODUCTION

ATM (Asynchronous Transfer Mode) is a recent intricate cell multiplexing

and switching technology that is capable of transferring data, graphics, voice and data

simultaneously in real time over the same line across LAN (Local Area Network),

MAN and WAN. Due to its efficiency of use, it has become one of the most desirable

technologies in today’s world. So far as the speed of ATM is concerned, it can make

up to 10 Gbps making it one of the fastest network protocol ever been used. The data

in an ATM network in transferred in an asynchronous manner which entails that it can

transfer data when it can. The term Asynchronous also cites to the fact that, in the

circumstances of multiplexing transmission, cells which are allocated to the same

connection may show an irregular form as they are filled on the basis of the actual

requirements as shown in the below figure.

Fig: 1-Asynchronous and Synchronous Transfer Mode [14]

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ATM is an ITU-T (International Telecommunication Union-

Telecommunication) standard for cell relay where the information’s regarding data;

voices, graphics and video are showed in packets with small size called cells via

switched based network. Based on the rising standards for B-ISDN, ATM converts all

the incoming data into 53 bytes (5 header bytes and 48 bytes of data) cells.

ATM technology can transfer various types of data in a real time over the

same line which is because entire bandwidth is employed, as long as it is available. In

case of other network technologies, they do not allow every bandwidth to be utilized

once a specific function is initiated making it one of the fastest and efficient way for

transferring data, graphics, video, pictures and even the live streaming video and

audio.

ATM is a connection oriented network technology in a sense that they should

inform every switch about the traffic parameters and service requirements before

communications between two systems in a network. Every connection in an ATM

network is known as virtual channel or virtual circuit (VC). By determining the

number of VCs, the connections let the network to guarantee QoS (Quality of

Service).

Here is the figure of private ATM and public ATM network conveying voice,

video and data traffic

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Fig: 2- A private and Public ATM conveying

voice, video and data traffic [REF 8]

1.1 OBJECTIVES

The first objective of this project is to let know everyone that there is also a

network technology with higher speed characteristics besides frame relay and

Ethernet and other LAN networking technologies and it is called ATM

(Asynchronous Transfer Mode). And then you will know about the prominent features

and the benefits of ATM including its Quality of Service (QoS). Moreover, the basic

cell structures and cell header format, ATM network interfaces, ATM applications,

network topology and ATM protocol reference model are presented here in detail.

Lastly you will be knowing some of the parameters required to control and manage

bursty traffic in order to guarantee Q0S (Quality of Service).

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1.2 HISTORY AND DEVELOPMENTS [REF 4]

Before ATM, the networking world used to depend upon specialized network

service. Relying on those specialized network service bring out many problems like

Service Dependence, inefficiency and inflexibility. There were many different types

of services that used to depend on the specific type of network. Advancement of the

technology increased the complexity for networks to handle different types of services

and also inefficiency of resources raised because of the internal resources was not

available to other network.

ATM firstly known as Asynchronous Time Division Multiplexing was

designed to overcome the inefficiencies of classical TDM (Time Division

Multiplexing). The technique evolved for encrypting transatlantic conversation

between Churchill and Roosevelt was synchronous. The actual root of this technology

lies in the Bell Labs research project which was held in the late sixties. But was

emerged by ex-CCITTs (Committee Consultatif International Telephonique et

Telegraphique which is now known as ITU) study group in the mid-eighties.

By the year 1991, to pick up the pace for the development ATM Forum was

created by telecommunication vendors and a group of four computers with the motive

to develop the ATM products and services. Within last few years there is a dramatic

increase in the number of members in Forum and now it has more than 750 members.

They include users, computer industries and research organization, communications

and agencies.

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The task which was finished in November, 1995 was started in 1993 by

CCITT under the recommendations on ATM equipment functional operation and

network management. Its specifications are transfer up to its standard bodies for

approval due to this the Forum not being a standards body, the ITU-T recognized the

ATM Forum as a credible working group. The ATM Forum has originated entirely

new specification by extending standards for private network specific requirements.

Nowadays, ATM has achieved world-wide acceptance because it influences,

many segments of our society like, touching the consumer, public-service and

commercial markets. Due to its high speed and the integration of traffic types it

provides a single network for all traffic types with new application.ATM will operates

network management by using the same technology for all levels of the network.

ATM is protocol independent. ATM guarantees quality of service.ATM is designed to

be scalable and flexible in geographic distance. Multimedia will be one of the key

applications to use ATM. In the near future ATM is intended to be used as a backbone

for other existing services like frame relay. ATM supposed to improve LAN/Client -

Server architectures and LAN interconnection. ATM will provide the resources to

ease the network demands. Many of the details that are necessary to provide ATM

benefits are still in the standards process. ATM is much more emphasized in road than

communication so wide range of voice service will not be provided further down the

road, further more it is likely be replaced by another technology such as Wavelength

Division Multiplexing

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1.3 BASIC FEATURES OF ATM [REF 5] [REF 6]

Following are some of the basic features of ATM presented by ITU-T in I.150

recommendation:

ATM technology employs fixed sized packets called cells. Each cell

incorporates o a header and an information field, basically applied to find out

the virtual channel and also to carry out the sound routing. Due to the way of

ATM networks carrying voice traffic, simple fixed sized cells are used.

ATM is a connection oriented network technology in a sense that they should

inform every switch about the traffic parameters and service requirements

before communications between two systems in a network. Separate virtual

circuits are used to carry user information and signals.

ATM cells, information fields are conveyed transparently via the network

inside which no processing like error control are carried out.

Different service like data, video and voice can be carried through ATM, Even

the connectionless services. An adaptation function is furnished in order to

adapt different services so that every services information is fit into ATM

cells. The service particular functions like cell loss recovery, clock recovery

etc are possible only because of this adaptation function.

Some other magnificent principles of ATM are as follows: [REF 2]

ATM is a high speed connection oriented network that employs fiber optics

wire, switch with switched point to point connection and are connected to each

other and to the end stations.

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In order to pass traffic amongst two positions, it makes use of the virtual

networking concept.

With ATM network, one is able to transfer a broad range of classes of services

of multimedia like text, voice, video over a single network effectively.

The high data transfer speed (155 Mbps, 622 Mbps and even 2.5 Gbps)

supplied by the ATM network allows a high bandwidth distributed

applications due to which the applications like video conferencing

applications, applications using video on demand mechanisms are possible.

Unlike Ethernet, ATM does not share a wire. When a wire is shared, it

becomes overloaded since everybody uses it at the same time. However, in

ATM, every computer is directly connected to a switch.

It endorses both the basic approaches of switching amongst a single

incorporated switching mechanism. This makes ATM suitable for every

distributed application generating CBR and VBR traffic.

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1.4 BENEFITS OF ATM

High Quality of Service level (QoS)

Quality of Service (QoS)

In a networking concept, Quality of Service is a broad set of

networking techniques, standards and technologies to manage network traffic

in a cost-efficient way so that a high quality performance is ensured for the

critical applications. The major purpose of QoS is to enable the network

administrators use the available resources effectively and assure the ability of

network to give predictable results. For instance: QoS can be used in order to

prioritize network traffic for latency sensitive software’s like video and voice

applications. Delay (latency), error rate, uptime (availability) and throughput

(bandwidth) are some of the elements associated with the quality of service.

The networking technologies like Frame relay, ATM and even the primitive

LAN technologies like token ring and Ethernet endorses the mechanisms of

QoS.

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Network characteristics Descriptions

Reliability Percentage of packets discarded by a

router

Bandwidth The rate of carrying traffic by

network

Latency The delay in data transfer from source

to destination

Jitter Variation in latency

Fig: 3- networking elements associated with QoS

QoS is one of the prominent features of ATM. It was projected to

ameliorate QoS and usage on high traffic network. Fixed sized small cells and

no routing makes network to manage bandwidth more easily than the primitive

LAN technologies like Ethernet. Five broad service categories of ATM [CBR

(Constant Bit Rate), VBR (Variable Bit Rate), ABR (Available Bit Rate),

UBR (Unspecified Bit Rate), WUBR (Weighted Unspecified Bit Rate),] offer

a fine control over the parameters of network traffic which are managed and

requested.

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The networks in ATM are more cost efficient.

With ATM, you can use various applications on the same network making

your administration, operation, materials and operation costs lower.

Flexibility

Various classes of service in order to carry data, voice and video over a single

network are endorsed by the ATM networks. Moreover, ATM networks can

allocate every connection to cope with the precise demand of every

application. ATM networks are flexible in such a way that it can assure

bandwidth from the desktop from DS-1 to OC-12 in the United States while

E1, E3, OC-3 and DS-3 globally.

Scalability

Projected to spring up with your endeavor as your demands and necessities,

the ATM networks are able to connect to the networks of Frame relay and can

also support it to ATM service internationally. Likewise, various speeds are

available (DS3, DS1, OC3, NxDS1 and OC12). The good thing about the

ATM technology is that the internetworking with Ethernet, broadband and

frame relay can go smoothly.

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Manageability

The homogeneous network surroundings of ATM plays significant role to

improve the network reliability, flexibility and the performance. Also the

carrier’s network management platform takes into account the higher

manageability in reporting, troubleshooting and in many more.

Secure

The recovery of failure and the automatic configuration is possible in ATM

networks.

Some other benefits of ATM are as follows: [REF 6]

ATM networks offer high performance through switching of hardware.

For high traffic, ATM can render you the dynamic bandwidth.

Supports different classes of services needed for the purpose of multimedia

(voice and video).

The architecture of LAN and WAN are common in the ATM networks.

In compliance with international standards.

Like primitive telephony services, ATM technology is connection oriented.

Simplified network architecture

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1.5 ATM STANDARDS

ITU-T, IETF (Internet Engineering Task Force) and the ATM forum are

the three main groups responsible for determining the implementation standards for

ATM network.

1.5.1 ITU-T

The telecommunication standardization area of the ITU in 1988 developed

some standards for the network in ATM technology. In fact, ATM was developed

when the researchers in the very ITU Company were trying to find some solutions for

B-ISDN. The main purpose of ITU-T is to define the standards for telecommunication

services. The promising technologies like B-ISDN and SONET were developed by

ITU-T.

Fig: some of the ITU-T recommendations associating to ATM

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1.5.2 IETF

IETF define the standards for the internet. The team of the IETF organization

developed a number of standards for IP traffic over the networks in ATM. Below is

the chart showing the lists of RFCs required for the implementation of IP over ATM.

Fig: 4 – standards of IETF associating ATM.

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1.5.3 ATM Forum

Non-profit international team of ATM network software developers, hardware

developers and network service providers, ATM Forum comprises of the working

teams who develop and review the specifications of ATM technology. In order to use

ATM over private and public networks, the standards of ATM defined by ITU-T

organization were extended.

Fig: some of the specifications of ATM forum relating to ATM

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1.6 ATM APPLICATIONS

There are various pragmatic applications using ATM technology. ATM is going to be

the keystone network for various applications even for the information superhighway.

Following are some of the notable applications using ATM technology.

LANE (LAN emulation)

Access to internet, intranet and extranet (e-mail, text imaging, forms

processing)

Video and desktop conferencing

Communications of the multimedia

Packetized video and voice

VPI/WAN connectivity

E-commerce

LAN interconnection

Web hosting

ATM over satellite communications

ATM over wireless mobile computing

SNA (System Network Architecture)

Terminal-host (client-server) data

File transfer

Remote access

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1.7 ATM DEVICES AND THE NETWORKING ENVIRONMENT

[REF 5]

ATM is a multiplexing and cell-switching connection oriented technology

combing the advantages of both circuit switching and packet switching. It offers you

the bandwidth of few Mbps and can even reach up to many Gbps. Due to the

asynchronous nature of ATM, it is more effective than the technologies with

synchronous data transfer. TDM (Time Division Multiplexing) is the suitable example

of synchronous technologies.

In case of TDM, every user is allotted to a time slot. Other station cannot send

in that time slot which is shown in the fig: 4. the station can send as much as data only

if the time slot rises even if every time slots are free. To its contrary, if a station has

not anything to send at the time when time slot rises, the very time slot has to be sent

empty and become wasted.

Fig: 5- operation of normal TDM. [REF 5]

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However, in the case of ATM, on demand with the information referring to the

origin of the transmission held in the header of every ATM cell, time slots are

available.

Fig: 6- ATM multiplexing in asynchronous way. [REF 5]

Figure 6 depicts the way of multiplexing the cells from 3 inputs. Input 2 does

not have any data to transfer, so the slot is filled with a cell from third input which is

done by multiplexer. Output slot becomes empty only after all the cells are

multiplexed from input channel.

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1.8 ATM NETWORK INTERFACES

ATM network incorporates a set of central devices called ATM switches

which are in point to point connection to each other. Two basic types of interfaces are

supported by the ATM Switches. They are UNI (User Network Interface) and NNI

(Network-Network Interface).

The end systems of ATM like routers and hosts are connected to an ATM

switch by the UNI while two ATM switches are connected by NNI.

Depending on if the ATM switch is publicly owned or located at the client

premises and functioned by the telephone organization, NNI and UNI can be sub

grouped into private and public NNIs and UNIs.

A private switch and an endpoint of ATM are connected by a private UNI

while public UNIs links an endpoint of ATM or private switch to public switch.

Within the same public organization, a public NNI links two switches of ATM while

two ATM switches are connected amongst the very private organization are

connected by the private NNI.

Fig: 7- ATM network interfaces in public and private networks.[REF 8]

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1.9 NETWORK TOPOLOGY [REF 1]

The establishment of ATM Data Link Layer topology was carried out by

seeking for the exactly same sets of active VCs in any remote side’s VCs table of

ATM port associated to the same type of the local ATM port. This kind of topology is

also employed to the fundamental physical links. Based on the lowest active VCs, it

expects for harmony amongst participating ports VCs table. Using Cisco confidential

scheme, furthermore verifications are done where VC traffic signature of these ports

are compared. Significant amount of traffic is required for the Cisco confidential

scheme to work properly. Only same VPs OR same VCs are supported by this

mechanism but not the mixture of VPs on one side and VCs mixture on other side.

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2 HOW ATM WORKS?

2.1 ATM CELL BASIC STRUCTURE

As we have already mentioned that ATM transfers every data and information

in fixed sized small packets called ATM cells. Fixed sized small cells are used

because they are more fitted to transmit video and voice traffic. ATM cell comprises

cell header of 5-byte or octets and 48 bytes of user information also known as

payload. In order to support the virtual channel routing and virtual path and to carry

out the quick error check for cells which are corrupted, ATM network employs the

header field.

Fig: ATM cell basic format

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2.2 ATM CELL HEADER STRUCTURE

An ATM cell header is basically of two formats. They are NNI and UNI. In

order to communicate between ATM switches, NNI header is used while UNI header

is employed to communicate between ATM switches and ATM end points in ATM

private network. So we can conclude header is used to communicate amongst ATM

switches.

Here is the figure showing you the basic ATM cell, UNI cell and NNI cell.

Fig: ATM cell, ATM UNI cell and ATM NNI cell [REF 8]

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2.2.1 ATM CELL HEADER FIELDS [REF 5]

Including VPI (Virtual Path Identifier) and GFC (Generic Flow control) header

fields, various other fields are employed in ATM cell header fields. Following are

some of them which will summarize the ATM cell header fields show in the above

figure.

Virtual Path Identifier (VPI)

8 bits of VPI is in conjunction with the header field VCI. As it passes

through ATM switches on the path to its destination, it determines the coming

destination of a cell.

Generic Flow control (GFC)

4bits of GFC major function is to determine multiple stations sharing

the same ATM interface.GFC is generally not in use and its value is put to a

default value.

Virtual Channel Identifier (VCI)

16 bits of VCI is in conjunction with the header field VPI and does the same

function like that of VPI.

Congestion Loss Priority (CLP)

1 bit of this header field shows if the ATM cell has to be cast away

when there is utmost congestion as it passes via the network. The cells with

the CLP bit 1should be discarded in preference to the cell having CLP bit 0.

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Payload Type (PL)

3 bits of his header fields of ATM cell shows in the first bit if it

consists of control data or user data. The second bit shows over –crowding

when the cell consist user data and the third bit points if the cell in a series is

last representing a single frame of AAL5.

Header Error Control (HEC)

On the header itself, 4 bits of this header field of ATM cell estimates the

checksum.

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2.3 ATM PRPTOCOL REFERENCE MODEL

Based on the standards established by the ITU-T, ATM reference model or B-

ISDN protocol reference model main purpose is to clear up the functions performed

by the ATM networks by teaming them into a function specific, interrelated set of

planes and layers.

The ATM reference model incorporates the following planes. They are control plane,

user plane and management plane.

Control plane

This plane generates and manages requests of signaling.

User plane

Transfer of data is managed by this plane

Management plane

This plane is again sub grouped into two components. They are:

Layer management is responsible for the layer specific tasks like detecting

failures and the problems of protocol.

Plane management is responsible for managing and coordinating the

functions associated to the whole system.

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ATM reference model incorporates the following three layers:

Physical layer

Correspondent to the OSI (Open Systems Interconnection) reference

model, Physical layer, the physical layer of ATM is responsible for managing

the medium-dependent transmission.

.

ATM layer

Joined with the adaptation layer of the ATM reference model, ATM

layer slightly corresponds with the OSI model, data link layer. The major

function of ATM layer is to establish connections and to pass cells via the

ATM network. To perform this, it employs information in the header of every

cell.

ATM Adaptation layer (AAL)

Joined with the ATM layer of ATM reference model, ATM adaptation

layer is slightly analogous to the data link layer of the OSI reference model.

The main function of this layer is to isolate the protocols of the higher layer

from the details of the ATM processes.

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Here is the figure illustrating the ATM protocol reference model.

Fig: Relating ATM reference model with the lowest two layers of the OSI

reference model. [REF 8]

Now, let’s study above three layers of the ATM reference model in detail.

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2.3.1 ATM PHYSICAL LAYER

Following are the major functions of the ATM physical layer.

To convert cells into a stream of bit.

To control the transfer and the receipt of bits on the physical media.

To track the boundaries of ATM cell.

ATM Cells are bundled into the approp

riate frame types required for the physical device.

The ATM physical layer is further divided into two types: they are PMD (Physical-

medium-dependant) and TC (Transmission convergence) sub layer.

PMD

Following are the main functions of PMD sub layer.

It is responsible for synchronizing reception and transmission by sending and

receiving bits flowing continuously with related information of timing.

For the physical medium employed, it fixes the physical medium including

cable and connector.

SONET/SDH, DS-3/E3, 155 Mbps over STP cable and 155 Mbps over MMF

(Multimode Fiber) with 8B/10B encoding schemes are some of the examples of

the physical medium standards.

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TC

Following are the main functions of TC sub layer.

Responsible for maintaining boundaries of an ATM cell, allowing physical

medium to position cells amongst a bit stream. This is also known as cell

delineation.

Responsible for checking and generating header error control code to check

data which are valid.

Transmission frame adaptation bundles the acceptable frame into the specific

implementation of the physical layer.

Cell rate decoupling means the maintaining of synchronization.

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2.3.2 ATM ADAPTATION LAYER (AAL)

The main function of this layer is to support four service classes and to allow

available applications like CBR video and protocols like IP to run on top of ATM as

shown in the below figure.

Fig: AAL layer is only located at the edges of ATM network. [REF 9]

This very layer is only applied at the end point of an ATM network which

either could be an IP router or the host system. In this case, you can say it’s being

analogous to the transport layer situated in the internet protocol stack.

The ATM standards like ITU-T and ATM forum has presented some of the

AAL standards some of the crucial AALs endorsed by the above standardization of

AAL are as follows:

AAL 1: For constant bit rate (CBR) services and circuit emulation.

AAL 2: For variable bit rate (VBR) services.

AAL 5: For data ( IP datagram)

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The AAL is further divided into two sub layers. They are:

Segmentation and Reassembly (SAR)

SAR is located at the lower section of AAL. The packets are broken

down into cells during the transmission by this sub layer and they are again

kept together at the destination. Basically concerned with cells, this sub layer

is also able to add headers and trailers to the data units which are given to it

through CS in order to form user information.

Convergence sub layer (CS)

Service dependant Convergence sub layer plays crucial role to make

systems of ATM give various services and applications. It also accepts bit

streams from the application and breaks them unit of 44 or 48 bytes for

transmission.

The following figure shows you the way of AAL converting payloads or user

information into cells.

Fig: AAL converting user information into cells [REF 9]

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On the basis of types of data, various types of AAL layers are defined which are as

follows.

AAL 1

AAL 2

AAL ¾

AAL 5

AAL 1

This AAL is used to support service class A. Basically, the applications requiring

CBR like video and voice conferencing, 64 kbps voice uses this service. This is

known as isochronous. These applications are very sensitive to time and thus end to

end timing is predominant and has to be endorsed.

Fig: AAL 1 [REF4]

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AAL 2 [REF 3]

Initially, AAL2 was believed to endorse VBR (Variable Bit Rate) applications.

Packetized video and voice is the great example of such VBR applications. Although

AAL2 was thought in the early days of the development of ATM, it was not planned

but later on it came into action when the designers felt the need of AAL for voice

traffic. At the beginning they named that layer as AAL6 but soon they relabeled as

AAL 2. In the present context, AAL2 transport voice traffic and also allows various

small packetized video to be packed in a sing cell payload of 48 byte. This AAL is

used to support service class B.

Fig: AAL 2 [REF 4]

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AAL ¾

AAL 3 and AAL 4 were designed in order to support connection oriented data

traffic which does not contain delay constraints. These two layers too endorse VBR

applications like transfer of file. Soon,, the designers came to know that there was

only a few differences between AAL 3 and AAL 4. So both layers were combined to

form one AAL ¾. This service is no more in use now since it was replaced by the

simpler AAL 5. This AAL supports both service class C and D.

Fig: AAL ¾ [REF 4]

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AAL 5

This one is the common preferred AAL used in today world. AAL5 came into action

basically for the applications which do not have any delay constraints. IP traffic, FTP,

LAN and Network management are some of the applications in which AAL 5 was

implemented. Like, AAL ¾, AAL 5 also endorses the service classes C and D.

Fig: AAL 5 [REF 4]

Here is the table representing the four AALs along with their supported service

classes and QoS.

Fig: four AALs and their supported service class and QoS.

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2.3.3 ATM LAYER

This layer lies above the physical layer of the ATM Reference model.

Multiplexing, network management; routing, switching and traffic management are

the major functions of this layer. It accepts segments of 48 byte from the AAL sub

layers and then transforms them into cell of 53 byte by adding header of 5 byte. In this

way, this layer processes outgoing traffic. We have already mentioned above about

the format of ATM cell header.

Four major functions of ATM layer are as follows:

Multiplexing and de-multiplexing of ATM cell

This function includes cells multiplexing from individual VPs and VCs into a

resulting cell stream in the way it is transmitting.

GFC (Generic Flow Control)

ATM layer is responsible for controlling the flow of ATM traffic in a network

of customer. This function is defined at the UNI of B-ISDN and is no more in

use.

Generation and extraction

This function includes adding the proper ATM cell header to the cell

information field which is received from the AAL in the direction it is

transmitting. The values of VPI and VCI are received by translating from the

SAP identifier and the cell header is removed in the direction it is receiving.

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VPI/VCI translation

ATM layer perform this function at the nodes of ATM switching. ATM layer

translates the VPI field value of every incoming cell into a novel VPI value

which is going out. It translates VCI and VPI values into new values at VC.

Fig: virtual path and virtual channels [REF 3]

Fig: VPI and VCI switching [REF 3]

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2.4 ATM ADDRESSING

ATM addresses are required to endorse the employment of virtual connections

(VCs) through the whole ATM network.

Depending on the private or public ATM network, the type of ATM addresses

to be used is defined. ATM addresses are generally employs in order to set up VCs

within end points of ATM network.

Basically, ATM uses two types of addresses. They are E.164 addresses which

is telephony oriented and is proposed for use in public networks. Other one is AESAs

(end system addresses) which is aimed for use in private networks. E.164 address

cannot be more than 15 digits. For instance: 11 numbers are used in the Canada and

United States: 1-NPA-NXXX-ABCD, for example, 1-416-978-4765 where 1 is the

country code assigned by ITU , NPA, NXX and the final four digit number represents

area code, office code and the subscriber number respectively. Country code is

different for other countries with different format.

AESAs are based on the NSAP format having 20 bytes. ATM addresses having 20

byte length is composed of three different parts. Here is the figure showing you the

three parts of ATM addresses of 20 bytes.

Fig: three distinct parts of the 20 byte ATM addresses

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The AFI (Authority and Format Identifier) determines the type of NSAP, IDI

(International Domain Identifier) determines the allocation of address and

administration authority while DSP (Domain Specific Part) consist of information of

routing.

Following are three basic addressing formats used for the private networks:

DCC Address format

ICD Address format

E.164 Address format

DCC Address format

IDI is a Data Country Code (DCC) which determines various countries as

defined by ISO 3166. ISO National Member Authority in each country

distributes these addresses. For e.g.: DIN in Germany, ANSI in the USA and BSI

in the UK. Its AFI value is 39.

Fig: DCC Address format

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ICD Address format

In this format, IDI is an ICD (International Code Designer) which is

distributed by the ISO 6523 registration authority (British Standards Institute).

NSAPs of ICD are aimed for use by international organizations. Since, the number

of existing ICDs is limited, now it is so hard to obtain one. Its AFI value is 47.

Fig: ICD Address format

E.164 Address format

E.164 number is the IDI in this address format. This enable to use the E.164

addresses amongst the private ATM networks. Its AFI value is 45

Fig: NSAP E.164 address format

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The table given below shows the primary ATM addresses fields along with their

functions.

Address Fields Functions

AFI Determines the type of address

DCC Its value is 39 for DCC, 47 for ICD

AA Single byte specifies DSP of the address

Reserve Reserved for future use

RD 2 bytes of routing domain information

Area 2 bytes of area identifier

ESI 6 bytes of end system identifier

SEL I byte of NSAP selector

ICD 2 bytes of international code designator

E.164 8 bytes of ISDN telephone number

Fig: primary ATM addresses format fields [REF 1]

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3 ATM TRAFFIC MANAGEMENT [REF 3][REF 4][REF ]

An efficient and effective traffic control mechanisms is required in order to

guarantee the Quality of Service (QoS) utilizing the existing network resources to its

fullest and to deal with the potential errors that may occur amongst the network. The

functions given below make a framework for controlling and managing the

congestion and traffic in ATM networks. From the standpoint of ITU-T Rec. I.371:

these functions have to be employed in appropriate combinations.

Following traffic control methods should be applied in an ATM network:

Network Resource management (NRM)

Connection Admission Control (CAC)

Usage Parameter Control and Network Parameter Control (UPC/NPC)

Priority Control (PC)

Congestion Control (CC)

Fig: conﬁguration for traffic control and congestion control. (From ITU-T

Rec. I.371)

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Now, let’s study the above traffic control mechanism in detail.

3.1 Network Resource management (NRM)

Basically used in Broadband Networks, NRM deals with the distribution of

network resources in order to divide traffic in accordance with characteristics of

services. Virtual path techniques are used as a crucial tool to manage and control

traffic in an ATM network. They are also employed in statistical multiplexing for

separating traffic in order to prevent intervention of statistically multiplexed traffic

with other various traffics. For an instance: guaranteed bit rate traffic.

3.2 Connection Admission Control (CAC)

CAC is termed as the set of actions performed by the network during call

setup or call renegotiation phase in order to prevent itself from excessive input loads

like to establish if VP or VC connection can be rejected or accepted. Routing is the

suitable example of this CAC action.

3.3 User Parameter Control and Network Parameter Control (UPC/NPC)

UPC and NPC have the same functionalities on different interfaces. NPC

functions at NNI while UPC functions at UNI. UPC/NPC are the set of actions

performed by the network for controlling and managing traffic, on the basis of cell

routing validity and traffic offered at network access and user access respectively.

UPC/NPC main purpose is to protect network resources from unintentional

connection. This would affect the QoS of already established connection. After

accepting the connection by CAC, UPC/NPC controls the connection to assure if

traffic conforms to the traffic contract.

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3.4 Priority Control (PC)

In order to increase the performance of higher priority ATM cells, this PC

function of the network cast away the low priority cell and this is important for a

ATM network to manage the traffic efficiently.

3.5 Congestion Control (CC)

Sometimes the network resources become overloaded. This situation

typically refers to congestion. In this case, ATM network cannot guarantee the quality

of service to the connections which are already established and also to the connection

which are going to be established. ATM Congestion control means the set of steps

performed by the network to reduce the spread, intensity and the extent of the network

congestion.

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4 CONCLUSION

These days, you can find various networks available. However, in the

present era, ATM is a big concern due to its magnificent features which we have

already discussed above. With ATM, you can find a solution to the problems of the

current network. The good thing about ATM is its high speed features and its ability

to supports the traffic of different multimedia applications like data, voice and video

conferencing. All of these features of ATM is making it a compelling solution for

both WAN and LAN. With internationally deployment, ATM has been able to success

partially in the field of network technology but mostly used for IP traffic. However,

the latest new technologies like MPLS, DSL and FTTH have inherited the different

crucial concepts of ATM. ATM development and usage is sure to increase in the

future because “it meets emerging requirements for scalable transport of myriad end

user services, including data, voice and video”.

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5 ACKNOWLEDGEMENT

It is with great pleasure that I take the opportunity to thank my Lecturer Mr.

Gandip Khaling for his enthusiastic supervision, help, and guidance throughout the

work in this project.

I gratefully acknowledge his assistance in submitting recent references to

me. I have constantly benefited from his discussion and encouragement to

development of this work.

I would like also to thank all those they have helped, advised, and give

fruitful discussions during this work. Many thanks also are to the staff of Informatics

College.

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6 REFERENCES

1. [REF 1] Chapter 6, Asynchronous Transfer Mode, Cisco Active Network

Abstraction Technology Support and Information Model Reference Manual,

Version 3.6

http://www.cisco.com/en/US/docs/net_mgmt/active_network_abstraction/3.6/

master_tech/6atm.pdf

2. [REF 2] Asynchronous Transfer Mode (ATM) Network, Georgia Electronic

Scientific Journal: Computer Science and Telecommunications 2009, No .6

(23), Ojesanmi O. A,

http://gesj.internet-academy.org.ge/gesj_articles/1567.pdf

3. [REF 3] Asynchronous Transfer Mode (ATM), Arjan Durresi, Louisiana State

University

http://www1.cse.wustl.edu/~jain/papers/ftp/atm_chp.pdf

4. [REF 4] Asynchronous Transfer Mode: An overview, Scot A. Valcourt, ATM

consortium Manager, June 24, 1997

http://www.iol.unh.edu/services/testing/atm/training/ATM_Tutorial.pdf

5. [REF 5] Module 4 Switched Communication Network, Version 2 CSE IIT,

Kharagpur

http://nptel.iitm.ac.in/courses/Webcoursecontents/IIT%20Kharagpur/Compute

r%20networks/pdf/M4L6.pdf

6. [REF 6] Microsoft TechNet, How ATM works?, March 28, 2003

http://www.telecomspace.com/vop-atm.html

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7. [REF 7] International Technical Support Organization, Asynchronous

Transfer Mode (ATM) Technical Overview, October 1995

8. [REF 8] Asynchronous Transfer Mode Switching, Internetworking

technologies handbook

http://www.cisco.com/univercd/cc/td/doc/cisintwk/ito_doc/atm.pdf

9. [REF 9] Asynchronous Transfer Mode, Link Layer and Local Area Networks

http://www.cs.utexas.edu/~yzhang/Teaching/cs386m-f10/Readings/atm_kr.pdf

10. [REF 1O] Asynchrnonous Transfer Mode, TelecomSpace Telecom tutorial,

forum, latest trends, News

http://www.telecomspace.com/vop-atm.html

11. [REF 11] Main features of ATM (Asynchronous Transfer Mode),

Indiastudychannel.com, MuthuKumar, 28 Dec, 2009

http://www.indiastudychannel.com/resources/100608-Main-Features-ATM-

Asynchronous-Transfer-Mode.aspx

12. [REF 12] Asynchronous Transfer Mode ATM Network service Features and

Benefits, ATM bids,

http://www.atmbids.com/atm-features-and-benefits.shtml

13. [REF 13] ASYNCHRONOUS TRANSFER MODE, Fundamentals of

telecommunications, Roger L. Freeman, 1999

14. [REF 14] MULTIMEDIA APPLICATIONS OVER ASYNCHRONOUS

TRANSFER MODE (ATM) NETWORK, Eng. Ayman El-Sayed Ahmed El-

Sayed

15. [REF 15] ATM- Asynchronous Transfer Mode, Wireless/Networking,

Bradley Mitchell, 1999

http://compnetworking.about.com/od/networkprotocols/g/bldef_atm.htm

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7 TURNITIN REPORT

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