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An ATM network must establish a connection before two parties can send cells to each other. This is called a virtual circuit (VC). It can be a permanent virtual circuit (PVC), which is created administratively on the end points, or a switched virtual circuit (SVC), which is created as needed by the communicating parties.
A permanent virtual circuit (PVC) is a virtual circuit established for repeated/continuous use between the same DTE. In a PVC, the long-term association is identical to the data transfer phase of a virtual call. Permanent virtual circuits eliminate the need for repeated call set-up and clearing. Frame Relay is typically used to provide PVCs.
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 to send only one packets belonging to a ...
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.
ATM Adaptation Layer 5 (AAL5) is an ATM adaptation layer used to send variable-length packets up to 65,535 octets in size across an Asynchronous Transfer Mode (ATM) network. Unlike most network frames, which place control information in the header , AAL5 places control information in an 8-octet trailer at the end of the packet.
These virtual circuits reliably carry variable-length packets with data order preservation. DATAPAC in Canada was the first public network to support X.25, followed by TRANSPAC in France. [136] Asynchronous Transfer Mode (ATM) is another virtual circuit technology. It differs from X.25 in that it uses small fixed-length packets , and that the ...
An IP network is packet oriented; so if ATM is used as a core, packets must be encapsulated in cells and the destination address must be converted to a virtual circuit identifier. Some new types of optical fibre use a passive optical network subscriber loop such as GPON, with the edge device connecting to Ethernet for backhaul (telecommunications).
Circuit switched communication, for example the public switched telephone network, ISDN, SONET/SDH and optical mesh networks, are intrinsically connection-oriented communication systems. Circuit-mode communication provides guarantees that constant bandwidth will be available, and bit stream or byte stream data will arrive in order with constant ...