Multiprotocol Encapsulation over ATM
Multiprotocol Encapsulation over ATM is specified in RFC 2684. It defines two mechanisms for identifying the
RFC 2684 describes two
In
In LLC Encapsulation the hosts use a single virtual circuit for multiple protocols. This has the advantage of allowing all traffic over the same circuit, but the disadvantage of requiring each packet to contain octets that identify the protocol type, which adds overhead. The scheme also has the disadvantage that packets from all protocols travel with the same delay and priority.
RFC 2684 specifies that hosts can choose between the two methods of using AAL5. Both the sender and receiver must agree on how the circuit will be used, and the agreement may involve manual configuration. Furthermore, the standards suggest that when hosts choose to include type information in the packet, they should use a standard
The AAL5 trailer does not include a type field. Thus, an AAL5 frame is not self-identifying. This means that either the two hosts at the ends of a virtual circuit must agree a priori that the circuit will be used for one specific
See also
- Asynchronous Transfer Mode (ATM)
- Point-to-Point Protocol over ATM (PPPoA)
- Broadband Remote Access Server