Network, Computer and Programming Resources

Network - VCC (Virtual Channel Connection)

In ATM, a VCC is a logical connection between two entities (which may be users or networks). This is the basic switching level for ATM and is analogous to a virtual circuit (VC) in an X.25 network. VCCs have the following features: n May be switched (established as needed) or dedicated (semipermanent) n Preserve the order in which cells are transmitted; that is, if cells A, B, and C are transmitted in that sequence, they are received in the same order at the other end n Provide a quality of service (QoS) that is specified by parameters concerning such features as variations in cell delays and cell losses (in relation to total cells transmitted) n Have performance parameters that can be negotiated by the entities involved in a connection The parameters that apply for a VCC are specified in a traffic descriptor, also called a user-network contract. Although the details have not yet been standardized, a user-network contract is expected to specify values such as peak transmission rate and maximum burst length. A group of VCCs can be allocated for the same connection, to provide the desired bandwidth for the connection. This type of VCC cluster is known as a virtual path connection (VPC). All channels in a given VPC are routed together, which helps reduce management overhead. Certain VCCs in a VPC may be reserved for network use.