Appendix F Routing and Signalling Concepts
302 Avaya M770 ATM Switch User’s Guide
Figure F.1 Virtual circuits in a virtual path
Virtual PortsTo support terminating virtual paths, the M770 ATM Switch uses virtual ports.
Virtual ports are typically used for Virtual Port Muxing, or tunnelling, through
public networks.
A physical port contains several virtual ports and each virtual port can be
considered a port in its own right. When a physical port initializes, a default root
virtual port is created. Further virtual ports can be created when you need them.
Connections are set up between virtual ports, and you can perform operations on
virtual ports, such as enabling and disabling them.
The maximum number of non-root vports that can be defined in the system is 32.
The maximum number of vports (root vports plus non-root vports) that can be
defined on a physical port depends on the number of vpi bits configured for the
module.
For example, if the number of VPI bits is 3, then the maximum number of vports
that can be defined on a physical port is 8. That is, 1 root vport (0) and 7 non-root
vports (1-7).
A virtual port will use a single VPI or a range of VPIs for all calls set up through that
virtual port.
Note: Only the root virtual port can have a range of VPIs. Subsequent virtual ports
can only be assigned a single VPI.
A virtual port has a range of VPIs so that:
• It can support a larger number of circuits than it could on the basis of its VCI
range alone.
• It can contain several virtual paths that are to be tunnelled up to a certain point
in the network after which they will diverge.
A virtual port in the M770 ATM Switch is represented by:
<slot number>.<port number>.<virtual port number>.
Physical Link
Virtual Path
Virtual Circuits