VC-MUX
Encyclopedia
Virtual circuit multiplexing or VC-MUX is one of the two (the other being LLC
encapsulation) mechanisms for identifying the protocol carried in ATM Adaptation Layer 5
(AAL5) frames specified by RFC 2684, Multiprotocol Encapsulation over ATM
.
With virtual circuit multiplexing, the communicating hosts agree on the high-level protocol for a given circuit. It has the advantage of not requiring additional information in a packet, which minimizes the overhead. For example, if the hosts agree to transfer IP, a sender can pass each datagram directly to AAL5 to transfer, nothing needs to be sent besides the datagram and the AAL5 trailer. This tends to reduce fragmentation overhead (e.g., an IPv4
datagram containing a TCP
ACK-only packet with neither IP nor TCP options exactly fits into a single cell). The chief disadvantage of such a scheme lies in duplication of virtual circuits: a host must create a separate virtual circuit for each high-level protocol if more than one protocol is used. Because most carriers charge for each virtual circuit, customers try to avoid using multiple circuits because it adds unnecessary cost.
It is commonly used in conjunction with PPPoE
and PPPoA
which are used in various xDSL implementations.
Logical Link Control
The logical link control data communication protocol layer is the upper sub-layer of the data link layer in the seven-layer OSI reference model...
encapsulation) mechanisms for identifying the protocol carried in ATM Adaptation Layer 5
ATM Adaptation Layer 5
ATM Adaptation Layer 5 is an ATM adaptation layer used to send variable-length packets up to 65,535 octets in size across an Asynchronous Transfer Mode network....
(AAL5) frames specified by RFC 2684, Multiprotocol Encapsulation over ATM
Multiprotocol Encapsulation over ATM
Multiprotocol Encapsulation over ATM is specified in RFC 2684. It defines two mechanisms for identifying the protocol carried in ATM Adaptation Layer 5 frames....
.
With virtual circuit multiplexing, the communicating hosts agree on the high-level protocol for a given circuit. It has the advantage of not requiring additional information in a packet, which minimizes the overhead. For example, if the hosts agree to transfer IP, a sender can pass each datagram directly to AAL5 to transfer, nothing needs to be sent besides the datagram and the AAL5 trailer. This tends to reduce fragmentation overhead (e.g., an IPv4
IPv4
Internet Protocol version 4 is the fourth revision in the development of the Internet Protocol and the first version of the protocol to be widely deployed. Together with IPv6, it is at the core of standards-based internetworking methods of the Internet...
datagram containing a TCP
Transmission Control Protocol
The Transmission Control Protocol is one of the core protocols of the Internet Protocol Suite. TCP is one of the two original components of the suite, complementing the Internet Protocol , and therefore the entire suite is commonly referred to as TCP/IP...
ACK-only packet with neither IP nor TCP options exactly fits into a single cell). The chief disadvantage of such a scheme lies in duplication of virtual circuits: a host must create a separate virtual circuit for each high-level protocol if more than one protocol is used. Because most carriers charge for each virtual circuit, customers try to avoid using multiple circuits because it adds unnecessary cost.
It is commonly used in conjunction with PPPoE
Point-to-Point Protocol over Ethernet
The Point-to-Point Protocol over Ethernet is a network protocol for encapsulating Point-to-Point Protocol frames inside Ethernet frames. It is used mainly with DSL services where individual users connect to the DSL modem over Ethernet and in plain Metro Ethernet networks...
and PPPoA
Point-to-Point Protocol over ATM
The Point-to-Point Protocol over ATM is a network protocol for encapsulating PPP frames in AAL5. It is used mainly with DOCSIS and DSL carriers....
which are used in various xDSL implementations.