Inverse Multiplexing for ATM
Encyclopedia
IMA is a standardized technology used to transport ATM traffic over a bundle of T1
T-carrier
In telecommunications, T-carrier, sometimes abbreviated as T-CXR, is the generic designator for any of several digitally multiplexed telecommunications carrier systems originally developed by Bell Labs and used in North America, Japan, and South Korea....

 or E1
E-carrier
In digital telecommunications, where a single physical wire pair can be used to carry many simultaneous voice conversations by time-division multiplexing, worldwide standards have been created and deployed...

 cables, also known as IMA Group. This allows for gradual increase in line capacity, where implementing a high-capacity solution (e.g. optical fiber
Optical fiber
An optical fiber is a flexible, transparent fiber made of a pure glass not much wider than a human hair. It functions as a waveguide, or "light pipe", to transmit light between the two ends of the fiber. The field of applied science and engineering concerned with the design and application of...

) is not deemed feasible. The maximum number of cables in an IMA Group is 32, bringing the total data rate to roughly 64 Mbit/second. The standard specification was initially approved by The ATM Forum in July 1997, and was later updated to version 1.1 in March 1999.

ATM cell insertion happens in the round robin fashion and is transparent for the terminal equipment
Terminal equipment
In telecommunication, the term terminal equipment has the following meanings:* Communications equipment at either end of a communications link, used to permit the stations involved to accomplish the mission for which the link was established....

 on the ends of the link. IMA inverse multiplexing functionality requires some overhead (ICP or IMA Control Protocol cells, typically one ICP cell in every IMA frame—commonly 128 cells in length—and in CTC or Common Transmit Clock mode, an ICP stuff cell must be inserted after every 2048 cells), and an IMA sublayer on the physical layer
Physical layer
The physical layer or layer 1 is the first and lowest layer in the seven-layer OSI model of computer networking. The implementation of this layer is often termed PHY....

.

See also

  • The ATM Forum IMA specification, version 1.1, http://broadband-forum.org/ftp/pub/approved-specs/af-phy-0086.001.pdf
  • Inverse Multiplexing
    Inverse multiplexer
    An inverse multiplexer allows a data stream to be broken into multiple lower data rate communication links. An inverse multiplexer differs from a demultiplexer because the multiple output streams from the former stay inter-related, whereas those from the latter are unrelated...

  • http://www.cisco.com/en/US/tech/tk39/tk356/technologies_configuration_example09186a0080174992.shtml
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