Cabletron Systems BRIM-A6 manual Permanent and Switched Virtual Channels, ATM Protocol

ATM Protocol

B.3.2 PERMANENT AND SWITCHED VIRTUAL CHANNELS

ATM networks use two different types of Virtual Channels – Permanent Virtual Channels (PVCs) or Switched Virtual Channels (SVCs). The difference between PVCs and SVCs exists in the channel set-up.

PVCs are pre-configured by an administration function, and are usually established for long term use. After setting-up this channel, nothing else is required by the network to transfer information between the two established points. This type of virtual channelling is established through a local or remote management interface.

SVCs use a signaling and network switching procedure to set up dynamically. In other words, SVCs establish “on the fly,” as needed for a particular service, are used to transmit on the short term, and then terminated. Each time a specific channel is established, a routing protocol comes into play providing LAN-style operation and management.

B.4 ATM PROTOCOL

Existing PTM transmission technologies (Ethernet, Token Ring, FDDI) adhere to the International Organization for Standardization (ISO) Open System Interconnection (OSI) model. This seven layer model provides a consistent hierarchy of rules for developing system connection standards. In essence, OSI is a framework on which protocols for particular network types are based. It is important to note that the OSI model is different from the ATM model.

A user’s perception of how a network operates is that it provides a direct link to another device. In reality, the information that the user sees is routed through the layers represented in the following models. Each layer modifies the information a user is either sending or receiving, according to the standards or protocol established for each individual layer.

BRIM-A6 User’s Guide Page B-5