Cabletron Systems MMAC-Plus 9A128-01, Руководство по управлению

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9A128-01 and 9A129-01 Module Specific Information
Virtual Channels and Virtual Paths
Rather than addressing cells to a specific destination, as in a LAN, ATM addresses
cells to Virtual Channels (VCs) and/or Virtual Paths (VPs). This addressing takes
place in the header field of the ATM cell.
VCs and VPs are bi-directional (i.e., they transfer information in both directions
on a single channel or path), and are “set up” between devices on the ATM
network prior to transmission. Similar to WAN transmission, ATM technology
provides the ability to send several VCs together over a VP, and several VPs over
an ATM link segment.
Permanent and Switched Virtual Channels
ATM networks use two different types of Virtual Channels – Permanent Virtual
Channels (PVCs) and Switched Virtual Channels (SVCs). The difference between
PVCs and SVCs exists in the channel setup.
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 are established “on the fly,” as needed for a particular service,
used to transmit on the short term, and then terminated.