Thread: Asynchronous Transfer Mode (ATM)

Asynchronous Transfer Mode (ATM) is a technology that has developed since 1990 ATM is a broadband multiplexing scheme which allows the multiplexing of widely differing types of digital signals into a common digital stream. It provides primary mechanism for switching broadband ISDN (BISDN) and hence, discussion of ATM inherently involves BISDN.
Unlike traditional packet switching, ATM uses a fixed-frame structure called a cell. The ATM cell is 53 octets (in ATM bytes are called octets) long, of which 48 octets comprise the message and 5 octets the header. The cell structure was chosen for two reasons. The relatively small cell size reduces queuing delay for high priority cells in the event of congestion. Fixed-size cells may be switched more efficiently since the switch need not look for an end-of-cell indication.



The header consists of several portions:

• Generic flow control (GFC)—This is a flag, which allow the bidirectional control of cell flow (data) to the network in the event the network becomes congested. It allows the user to define the traffic characteristics of the data that the network is to accommodate.

• Virtual path identifier (VPI)—This defines the virtual network path that will be used for routing cells across the network.

• Virtual channel identifier (VCI)—This is identifies the specific virtual channel/circuit (set of time slots) on which the cells will be carried between the point where the VCI is assigned and the point at which it is terminated or translated to new VCI.

• Payload type (PT)—This 1-bit field specifies whether the information carried in the information field is user data or network data.

• Cell loss priority (CLP)—This 1-bit field provides information to the network as to whether or not the cell may be discarded in the event of network congestion CLP=1 indicates that the cell may be discarded; CLP=0 indicates the cell may not be discarded unless to alternative exists

.

• Header error-control—A CRC field using the check polynomial
  
  
  
  It is used error detection and provides capability for single error correction and very low probability of undetected burst errors of magnitude greater than 1.

ATM Cell header field (user -to- network interface)



ATM cell header field (network -to- node interface)

Let us consider the concept of some what further. Virtual means that the connection is via a time slot as opposed to a fixed pair of wires. A virtual channel connection (VCC) connects to endpoints by means of the concatenation of a series of virtual Channel (VC) links. A virtual channel link is identified a by a VCI. A new VCI is assigned whenever the virtual channel link is switched. A virtual path connection (VPC) consists of the concatenation of a series of virtual path (VP) links, each consisting of a group of virtual channel link. Each virtual link is identified by a VPI, which is a common to all virtual channels in virtual path link. Within the VPC, each VCC is identified by a unique VCI. VCCs may have the same VCI within different VPCs. When a virtual path is switched, virtual channel remain unchanged and when virtual channel is switched virtual channel is also switched.



VP/VC link structure

• ATM Structure
• ATM is structured layer, as are many data transmission protocols. The ATM protocol model is pictured like that.
  
  
  ATM structure

• ATM services Classes
• ATM can be dividing by little service class like Class A, B, C, D in the basis of bit rate, connection mode, Timing synchronization. In one chart it can be easily describable.
  
  
  

• ATM categories—ATM has few categories like
• 1.Continues bit rate service with reserved peak bandwidth
• 2.Variable bit rte with reserved bandwidth.
• 3.Variable-bit-rate service without reserved bandwidth
• 4.Reserved burst bandwidth.

• Application of ATM
• Perhaps the most significant application of ATM is broadband ISDN (BISDN). The two technologies have developed in close parallel. Other applications include video-on-demand, SMDS, video conferencing, and DS3 switching.

[It has taken too much time to write and draw the pic few sentence error can be possible]

Really great work rupu...

Kudos...

Repo for you!!! :thumbup1:

I haven't red this fully. Shall complete it soon or later.

great post rupu :clap:
Will stick this thread

@ smoothvibes
Hope you won't delete this link as not needed !!!!

The only thing i ask you is to take efforts to explain rather than posting links. Links can not help everytime.

Yes i will delete this link too coz it is already explained above.

Originally Posted by essbebe

Better to COPY/PASTE , with minor edits, rather than quote the source of the article.
Are you not encouraging Plagiarism ?

Did anyone think i have copy/pasted from any other site ? then they are thinking wrong i never read that article which was provided earlier in this thread my source is in the base of analog & digital books.Which note was not available in net before and also i have drawn all the image in paint never made any editing of such internet note..Now this is technical thing obviously it will be quite similar in all same topic note but please give the link from where i have copy pasted.
What plagiarism ?
I never say i have invented such theory only i have explained it according to book .

I don't have the scanner and also that note was too big i have taken the and providing now i think now someone become happy

This is my link(i have taken it in my mobile camera)
i have attached it as .rar file
or
Never

I did not make any copy-paste from other site i have written & drawn picture basically from analog & digital communication book (only intention to write a short note from a big explanation for better understand). Some one can say it's identical like such link but please reply others that is ATM explanation can be totally different in each and other note ? after all basic technical explanation of the ATM obviously the same. I don't want to say any more those who know me very well they can understand that i have written it only for share the topic nothing else.
I have written this note in my B.Tech(as ECE student) and obviously teacher never recognize it as 'Plagiarism'
Please read B.P Lathi modern digital & analog communication system (2004 edition).382-389 page all thing will be clear.

wow... rupu, that was a brilliant post. Didn't know about these things before. Thanks for sharing such a useful post.

essbebe I have deleted all your posts from this thread as all of your doubts and comments are baseless, i checked all the pics added by rupu and suggest you too to check that .rar file. I am not sure why you are spending your 23 hours and 58 minutes everyday in searching links on google, yahoo or other search engines. If a person really need links to then he/she can go for google or yahoo search anytime, please mind that people don't come to forums to check links they come here to share knowledge.

Whatever rupu posted above is true and is in his own words, as rupu already said that definition of ATM can not be changed in every book or tutorial so i think you also know the standards.

I request you not to push down anyone's efforts like this with your links and if you really want to contribute to community then please start putting efforts in writing posts rather then posting links everywhere.

I have no doubt on your online search skills but that is not what people look for.

At last i would love to tell you not to post reply of this post coz if in case i will find any reply in this thread anymore then will delete it without even reading.
thanks

Rupu great effort mate, repo already added in your account. Keep it up

well really a great post. quite useful information for us people