Permanent Virtual Circuits; Switched Virtual Circuits - Cisco NM-1A-T3 - 1port Ds3 Atm Network Module User Manual

Configuring the Cisco NM-1A-T3/E3 Network Module
Each VC supports the following router functions:
•
•
•
•
By default, CEF switching is enabled on all ATM T3/E3 module interfaces. These switching features can
be turned off by using interface configuration commands. Flow must be explicitly enabled for each
interface.

Permanent Virtual Circuits

To use a permanent virtual circuit (PVC), configure the PVC in both the router and the ATM switch.
PVCs remain active until the circuit is removed from either configuration. When a PVC is configured,
all the configuration options are passed on to the OC-3 module. You can write these PVCs into NVRAM;
they are used when the system image is reloaded.
Some ATM switches might have point-to-multipoint PVCs that do the equivalent of broadcasting. A
point-to-multipoint PVC can be used as the sole broadcast PVC for all multicast requests.These
switching features can be turned off by using interface configuration commands. Flow must be explicitly
enabled for each interface.

Switched Virtual Circuits

ATM switched virtual circuit (SVC) service operates much like X.25 SVC service, although ATM allows
much higher throughput. Virtual circuits are created and released dynamically, providing user bandwidth
on demand. This service requires a signaling protocol between the router and the switch.
The ATM signaling software provides a method of dynamically establishing, maintaining, and clearing
ATM connections at the user-network interface (UNI). The ATM signaling software conforms to ATM
Forum UNI 3.0 or ATM Forum UNI 3.1, depending on what version is selected by interim local
management interface (ILMI) or configuration.
In UNI mode, the user is the router and the network is an ATM switch. This is an important distinction.
The Cisco router does not perform ATM-level call routing. Instead, the ATM switch does the ATM call
routing, and the router routes packets through the resulting circuit. The router performs as the user and
the LAN interconnection device at the end of the circuit, and the ATM switch performs as the network.
Network Layer Protocol ID (AAL5NLPID)
–
Integrated Local Management Interface (ILMI)
–
Switched Multimegabit Data Service (SMDS)
–
ITU/Q.2931 Signaling ATM Adaptation Layer (QSAAL)
–
Cisco AUTO PPP over AAL5 (aal5autoppp)
–
Cisco PPP over AAL5 (aal5ciscoppp)
–
Multiprotocol switching
Fast switching of IP packets
Flow, and Cisco Express Forwarding (CEF) switching of IP packets
Pseudo-broadcast support for multicast packets
Information About the Cisco ATM T3/E3 Network Module
Cisco IOS Release 12.4(15)T
3