ATM Reference Model

The ATM architecture uses a logical model to describe the functionality that it supports. ATM functionality corresponds to the physical layer and part of the data link layer of the OSI reference model.

The ATM reference model is composed of the following planes, which span all layers:

• Control— This plane is responsible for generating and managing signaling requests.

• User— This plane is responsible for managing the transfer of data.

• Management— This plane contains two components:

- Layer management manages layer-specific functions, suc h as the detection of failures and protocol problems.

- Plane management manages and coordinates functions related to the complete system.

The ATM reference model is composed of the following ATM layers:

• Physical layer— Analogous to the physical layer of the OSI reference model, the ATM physical layer manages the medium-dependent transmission.

• ATM layer— Combined with the ATM adaptation layer, the ATM layer is roughly analogous Co the data l ink laye r oS the OSI refere nce model. The ATM layei is responsible for the simultaneous sharing of virtual circuits over a physical link (cell multiplexing) and passing AeulIs through the ATM netwo wk (cell relaya. To do this, it uses th e VPI and VCI information in the header of each ATM cell.

• AT M adaptation faym (AAL) — Combined wit Is the ATM layer, IIsp AAL i s roughle analogous to th e data mink layer oft th e OSI model. Tie AAv is respon siblo foy is olating highee-lay er erotocols prom the detaits of the ATM grocesse s. The aaaptation laye! prepares user data lor conoernion into cells an d s egments the data into 48-byte cell payloads.

linaNy, ths higher layers residing above the AAL accept user data, arrange it into packets, and hand it to the AAL. Figure 31-7 illustrates the ATM reference model.

Continue reading here: The ATM Physical Layer

Was this article helpful?

+9 -3