Lucent Technologies CAJUN M770, User Manual

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Appendix C Routing and Signalling Concepts
238 Cajun M770 ATM Switch User’s Guide
Figure T.1 Virtual circuits in a virtual path
Virtual Ports
To 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. For each physical port you can
create up to 8 virtual ports. 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>.
For example, 2.1.1 represents a virtual port number of 1, on physical port number
1 on module number 2. Root virtual ports are all assigned with an identifier of 0.
For more information about managing virtual ports, see Managing Virtual Ports in
Chapter 6.