Inverse multiplexing for ATM

from Wikipedia, the free encyclopedia

Inverse Multiplexing for ATM (IMA) is a standardized data transfer process from the telephony . Data is transmitted in the form of ATM cells over a bundle of ISDN lines according to the E1 or DS1 / T1 standard.

In the case of parallel transmission over several lines, the data is split up using a demultiplexer and then put back together again using a multiplexer . IMA allows a step-by-step increase or decrease in the line capacity if several E1 / DS1 lines are available and the use of another transmission technology such as fiber optics is not possible. The maximum number of lines is 32, which corresponds to a total rate of 64 or 48 Mbit / s.

The draft standard was presented by the ATM Forum in July 1997 and the final version 1.1 was released in March 1999. It introduces the IMA protocol , which is part of the physical layer and is therefore below the ATM layer.

The transfer of the ATM cells takes place in the round robin process and is done transparently for the end devices on both sides. The trunk group is referred to as an IMA group , the individual trunks as IMA links . The cell stream is divided into IMA frames with usually 128 cells. Each IMA frame contains a cell, the ICP cell (IMA Control Protocol) with information about the group and link states of the sending side.

Links can be added or removed without losing any cells. An interruption in a line is automatically recognized by the IMA layer, which then automatically removes the link from the connection control. If the line can be used again, the link is reactivated.

IMA will u. a. used in cellular networks to connect base stations .

literature

Web links