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Cisco VISM Installation and Configuration Guide
Release 3.0, Part Number OL-2521-01 Rev. D0, June 2004
Chapter3 VISM Functional Descriptio n
Embedded VISM Management Function

Connection Admission Control

The VISM connection admission control (CAC) feature calculates the effect of a new call on the
bandwidth utilization of the ATM PVC before a new call is either admitted or rejected.
Each call requires a connection between two endpoints and req uire s a ce rta in a mount of ba ndwi dth.
Bandwidth is expressed as cells per second (cps) and depends upon the fol lowing:
•Encapsulation method
•Coding/compression method
•Enabled/disabled VAD
CAC maintains a table of all currently active calls and their bandwidth requirements. When a new call
is requested, CAC calculates the total bandwidth requirements of all the current calls and adds the
bandwidth required by the newly requested call. The new total is then compared w ith the preprovisioned
bandwidth (cps) of the ATM PVC.
If the new bandwidth total exceeds the preprovisioned bandwidth of the PVC, the call requ est is rejected.
If the new bandwidth total is less than or equal to the preprovisioned bandwidth of the PVC, the call is
accepted.
You can specify the values of the following VAD parameters in the CAC algorithm:
•Over-subscription drop ratio
•Voice duty cycle
VAD parameter specification allows the CAC algorithm to take into account the bandwidth savings of
VAD and improves the CAC decision-making process. You can specify the values of these parameters at
the card level and at the logical channel level. The default condition is for CAC to be enabled.
Embedded VISM Management Function
VISM management tools allow you to do the following:
•Configure VISM features
•Provision connections
•Display VISM configurations
•Display VISM statistics
Use any of the following tools to manage and configure the VISM card:
•CLI—See Chapter 4, “Configuring VISM Features,” for a description of how to co nfigure VISM
using the CLI. See Chapter5, “CLI Commands,” for a description of the syntax for each CLI
command.
•Third-party Simple Network Management Protocol (SNMP) manager—Permits you t o display and
manipulate the individual MIB objects.
•Cisco WAN Manager (CWM) program—Provides a graphics-based interface on a UNIX
workstation.