ATM in a nutshell

Aside from the following concise presentation of ATM, an ATM Portal that includes an extensive tutorial and editorial comments on ATM from the RAD University "Dean" can be found on the RAD University website.

More about ATM:
Overview |  Cell format |  Connections |  Layers Architecture |  Service Categories |  Addressing


Overview

 

Asynchronous Transfer Mode (ATM) is a switching and multiplexing technology, intended to move various types of traffic (data, voice, video, audio) quickly and efficiently.

 

ATM has two levels: transport and switching.

In the transport level, ATM's performance is similar to any other digital communication technology.

It is in the switching level, however, where ATM brings remarkable results:

Normally, packets and frames require smart switches controlled by slow-moving software to move them through a network. When using ATM, however, small, uniformly sized cells move through switches without needing software assistance. The cells already know the route to take and do not need to slow down to look for road signs or stop to get directions. Here the true greatness of ATM really unveils.

 

 

Advantages


 

Among the many benefits ATM has, we can find the follows:

 

  • Scalability in distance (suitable for both WAN and LAN technologies).
  • Scalability in speed (from Mbs to Gbs ratios).
  • Suitable for multiple traffic types (data, voice, video, audio).
  • Enables new applications.
  • Supports many users.
  • Compatibility to various physical networks - it can be transported over wide variety of physical networks.
  • Simplified network management - by using the same technology for all levels of the network.
  • Incremental migration capability.
  • Standards based, resulting in a long architectural lifetime.

 

 

Disadvantages

 

On the other hand, ATM has also some disadvantages:

 

  • Overhead of cell header (5 bytes per cell).
  • Complex mechanisms for achieving QoS (Quality of Service).
  • High cost.

 

 

Basic points

 

ATM involves a few basic concepts:

  • Its cells are small enough to fit into spaces too small for larger packets or frames, thus enabling both speed and efficiency.
  • Traffic routes are preplanned.
  • Switching is done without the need for time-consuming software.
  • Payload error checking and correction is performed only at the destination node, not at every hop along the way.