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Atm Versus Ip for Voice over Ip

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In this paper we mainly discuss about the technologies called asynchronous transfer mode(ATM) and internet protocol(IP).These are the two technologies that are having their own importance in today’s communication world of transmitting the voice and video signals over a network between a source and destination.We are about to see the main differences between these technologies and compare them theoretically and practically.An advanced software called OPNET modeler is used in comparing these two technologies for different parameters such as traffic issues,Queuing delays,quality of service(QOS),congestion,time of response etc.,

‘’NETWORK’’ this is the word that is well known by every individual of this generation as it has become their part of life right from the start of their day till it ends.After the evolving of internet there are many applications that came in to the existence producing different results in different applications where they are used and made the communication look easier from one part of the globe to the other.In any of the network topology the particular vendor will look for quality of service(QOS),reducing the congestion,etc., When dealing with voice and video transmission,there are particularly two technologies called asynchronous transmission mode(ATM) and internet protocol(IP).depending on the demand of the vendors,These two technologies have their own importance and are applicable in real time applications.

The foremost difference between these two technologies is that ATM technology depends on switching where as IP technology follows the routing method. Other than these two technologies there is other technology known as MPLS.This is known as the advanced version of the ATM.MPLS stands for multi protocol label switching and the function of the MPLS is to switch between the traffic and routers.This will help in speed,scalability and quality of service(QOS),the main problems that are faced in today’s communication world.This is not discussed in our paper. A detailed analysis on ATM and IP for different parameters is discussed and a comparison is done between these two technologies using OPNET modeler.In the next section we will have brief description about the asynchronous transfer mode and internet protocol. ASYNCHRONOUS TRANSFER MODE

Asynchronous Transfer Mode(ATM) is a technology that is required in transferring the data in terms of cells or packets that are of a fixed size.The size of the cell that are used with the ATM technology are small when compared with the carriers that are used with the other technologies.The function of the ATM is to transmit video,Audio and data belong to computer to the other computer over the same network.While transmitting the data from the source to the destination ATM creates fixed channel or route between them for the transfer of the data.This type of transmitting the data is completely different from TCP/IP in which the message is divided into packets that take different routes from the source to the destination.

Figure shows ATM network
There are three other terms that are to be discussed while having a brief description of ATM.They are
* Transfer mode
* Cell based transfer and
* Asynchronous transfer.
Transfer mode
ATM has features such that it is as speed as circuit switching and also more flexible as packet switching. The transfer mode in ATM is neither circuit switching nor packet switching.It adapts both the transfer modes and the main reason for this is it uses cells which are small sized frames. Cell based transfer

The ATM cell consists of fixed size frames and each frame consists of 53 bytes of data of them 5 bytes are dedicated to carry the header information and the remaining 48 bytes are to carry the information data.Each cell in the ATM is identified using virtual channel identifier(VCI) or virtual path identifier(VPI).ATM defines two different cell formats.They are UNI(user-network interference) cell format and NNI(network-network interference) cell format.But most of the vendors prefer to have UNI cell format. Asynchronous mode

It is defined as the reoccurrence of cells which contains the information that is non-periodic.

The ATM protocol is developed on the standards based by ITU.The function of the ATM network is that the data from higher layer is passed on to the lower ATM defined layers.From these the info is passed on to the physical layer through a physical medium.The ATM protocol reference model is divided into three different layers,They are ATM adaption layer,ATM layer,physical layer

ATM adaption layer
The ATM adaption layer(AAL) interfaces the higher layer protocols to the ATM layer.It relays ATM cells both from the upper layers and vice versa.When the information is received from the higher layers them AAL divides the data in to small segments and send them across the ATM.When data is received from the physical layer then the data that is in terms of small segments are collected and sent to higher layers via AAL. ATM layer

The function of the ATM layer is to provide the basic 53-byte cell format to the data that passed down by the AAL by defining it to 5-byte header and the remaining 48-byte as data payload. Physical layer

The function of the physical layer is that it act as a medium to transfer the data between the layer as shown in the figure.And around the physical medium a framing is done to keep the data content safe from the other external losses.

Internet Protocol(IP) is the primary network protocol used on the internet.It was developed in the early years of 1970’s and was used together with transport control protocol and referred as TCP/IP. The function of the internet protocol is to provide a unique address for the computer that are connected through a network.There are two versions present with the IP,They are IPV4 and IPV6.the basic difference between them is the length of the address.IPV4 have a four bytes(32bits) length of address where IPV6 has 16 bytes(128bits) address in length. The cell structure of the IP contains two parts they are

* IP header
* IP data

Figure shows typical Internet Protocol structure
Internet protocol is neither a architecture nor a designed set of protocols it is just a aet of protocols that are to followed for the transmission of data from source to destination. IP is a connectionless protocol and each time when the data packet travels it has create its own again to the destination address and has to reach it so every cell has got its own header space.And also the arrival of the packets may be not in uniform because as they follow connectionless path the timing may vary at the each packet arrival.Thus an acknowledgement are given to each packet at its header file.

ATM versus IP
Table.1.Differences between ATM and IP
In ATM routing is restricted for signaling messages (only cal setup period).| In IP each datagram is routed automatically.| It guarantees and offers good quality of service.| In IP Quality of service (QoS) is not highly offered and guaranteed. | Connection oriented| Connection less|

ATM can guarantee the order because virtual path is established before transmission.| IP cannot guarantee the order as there is no connection. Routing is done using IP address.| Links in ATM are highly reliable.| No reliability in links is provided in IP. | Rate of cell loss and cell corruption is less.| Cell loss may be high in transmission. | As cells move in a sequence, delays such as traffic and queuing are experienced. | Delays are less when compared to ATM networks as they transmit using specific addresses. | ATM follows switching in link layer.| IP follows routing in Network layer.| Congestion is less. | Congestion is more.|

Bandwidth efficiency is high. | Bandwidth usage is flexible.| Adaptive in nature.| Flexible and Robust.[5]|

Thus when both the networks are compared ATM is proved to be the most efficient network upon the internet protocol.The success of the ATM lies largely because of its ability to manage data traffic and using mostly IP over its network infrastructure. THEORETICAL ANALYSIS

Before going with a practical approach,we should have a look issues to be sorted out.Voice transmission is done through both the ATM and IP technologies but in a different way.both got its own strategies in transmitting the voice from source to the destination. When it comes through ATM it transmits the voice data in a sequential manner from source to the destination by establishing a virtual path between them.The data that is sent over this virtual path is routed in a sequence for avoiding some problems. But where as in internet protocol there will be no virtual connection between source and destination.An IP address is given to each of the system that are on the network.Based on the priority of the quality of service the packets containing data are received at the destination side.Now lets have a look which protocol is better in sending voice data.Both have some typical problems that are mentioned below.

* When compared in ATM traffic delay is more than IP.
* Baesd on the type of transmission both the protocols have got their own time of response and efficiency in transmitting the data.
* Congestion is more in IP when compared to ATM.

Congestion plays an exceptionally significant part in any sort of grid designing.So one needs to be carefull while composing a grid he needs to care for this sort of parameters while doing so.ATM will have less issue with congestion in light of the fact that the transmission of the information is finished with a virtual way in a consecutive path.But when discoursing on with the IP topology there is a considerable measure of blockage in light of the fact that it acclimates the most brief way for the transmission of the information from origin to the destination.Thus there needs to be an elective for this to be avoided.Seperate algoritms are improved in IP such that the transmission is finished by way of the longest way that are ready with in the topology.

Fig.5.Congestion in transmission path.
Theoretically we have seen that IP is far better ATM.and now lets have a look at the practical results that are obtained while performing the series of simulations using the OPNET modeler.

Practically we are about to analyze these ATM and IP networks by creating an example network topology.

Fig.6. An example network topology.
The above grid topology comprises of two diverse origins with routers and ends of the line in two number in each.There is in addition a message server to get messages and other server based stuff.we are to consolidation the profile,Applications and QOS based design settings for both ATM and IP separately.After all these settings DES is gathered for distinctive parameters that are sent over the grid topology from origin to the destination.Once the whole lot is associated and gathered we can run the situations (ATM & IP) by setting the recreation chance to and seed to 128.

After reproduction the effects might be gathered for needed parameter in both ATM and IP and investigate them regarding Queuing defer, Through Put and Utilization. OPNET SIMULATIONS
A. ATM Network:

Fig.7. ATM backbone network
The node model and link models for this ATM are also shown below.

Fig.8. Link model of ATM.
B. IP Network:

Fig.9. IP Link model.
After the networks are created, they are simulated for a particular period of time and results are collected in object statistics. VII. RESULTS
1. The below graph dissipates queuing delay exhibited by both the ATM and IP scenarios. Fig.10. Comparison of Queuing delay in IP and ATM. It decidedly shows that queuing postpone in ATM is more when contrasted with IP, however its differing straightly heightened then afterward diminishing, it is almost to zero which is extremely level when contrasted with ATM and is exponentially expanding. 2. The following figure shows packet delay in both the scenarios.

Fig.11. Packet delay variation
Coming to bundle defer it is exponentially expanding in both situations at the exact starting and has come to be steady in IP where as it is exponentially diminishing in ATM. Yet similarly ATM displays more bundle defer than IP. 3. The following figure shows Jitter delay in both ATM and IP scenarios.

Fig.12. Jitter delay
It is unmistakably recognized that in jitter defer there is no much distinction between ATM and IP yet just time passed in x hub of ATM yet straightly in y- pivot it is in the same run of 0.40. 4. The following graph shows the overall throughput of ATM and IP scenarios.

Fig.13. Throughput in ATM and IP
There is slight contrast between throughput in ATM and IP. Both are exponentially expanding and ending up being steady at certain indicate yet plainly it shows that throughput in ATM is coming to be reliable at 160, while in IP it is at 90. By this it might be inferred that Throughput in ATM is more. 5. The following figure shows the comparison of utilization in both scenarios.

Fig. 14. Point-to-point utilization
After itemized study and working of both situations (ATM and IP) systems topologies, it is inferred that IP is over decision ATM in deferral where as ATM is giving its best in throughput, usage, till close- to-close transmission, where as IP is best in Packet postpone and Queuing defer. Contrasting with the rate of the grids IP is quicker than ATM as the transmission in it is extremely speedy in IP as it utilizes IP location for conveyance of bundles as there is no virtual association between origin and end. There are likewise sure clogging issues in IP which are regulated utilizing tracking equations, and there is no clogging situation in ATM as switching of bundles is finished successively utilizing virtual way associations. Value of Service is profoundly ensured in ATM on the grounds that it is consistently straightforwardly relative to bundles gained where as in IP it is not abundantly ensured. As an on the whole, IP is best and chiefly utilized within numerous adventures, yards and so on. Both have their particular favorable circumstances and hindrances progressively requisitions and are generally suited for information, voice and movie transmissions.


1. Kasser, Sumith, 2007, “ATM Networks”, New York, Mc Graw-Hill. 2. Labrador, M.A, Banerjee. S, (2009). “Packet dropping policies for ATM and IP networks”. [Online]. 2(3). P.2-14.Available from: URL [Accessed: 16.12.2012]. 3. Sudhir Dixit, Ramjee Prasad, 2003, “Wireless IP and Building the Mobile Internet”, London, Architec House Publishers. 4. www.protocols.com/papers/voe.htm#voatm , accessed on 15th, December, 2012. 5. www.wand.net.nz/pubs/20/html/node23.html, accessed on 15th, December, 2012.

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