Avaya a500 사용자 가이드

Cajun A500 ATM Switch Overview

Cajun A500 ATM Switch User Guide

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Connection Admission Control (CAC)

The Cajun A500 software supports connections using UBR, CBR, and Variable Bit Rate 

non-real time (VBR-nrt) QoS classes concurrently. This integrates both voice and data 

switching traffic over a common Cajun A500 ATM platform. UBR is used to support the 

majority of data switching applications, such as LANE, Classical IP over ATM, and Virtual 

LANs (VLANs) over ATM. CBR and VBR-nrt will be used to support voice traffic 

connections.

In order to guarantee delivery of CBR and VBR-nrt cells through the switch fabric and to 

the outgoing port, the Cajun A500 uses CAC. The use of CAC ensures that an output 

port is not oversubscribed. For example, if port A1.1 currently has 95% of its outgoing 

bandwidth reserved for existing CBR connections and a connection request is made for 

10% of the port's bandwidth, the CAC rejects the request. However, if the request is 

made for 5% or less, the request is accepted. 

Note:  The CAC does not effect UBR traffic. UBR traffic is best effort and is never 

guaranteed to be delivered.

PNNI Functionality

The Cajun A500 PNNI supports the following:

U Single peer groups

U Separate virtual network routing domains

The Cajun A500 ATM Switch provides Private Network-to-Network Interface (PNNI), a 

dynamic routing protocol that manages and allocates network resources for SVCs in an 

ATM network. It keeps track of the current status of all switches and links in order to 

manage resources and dynamically creates routing tables in ATM switches. When an end 

station requests a connection with specific QoS parameters, PNNI is able to find a 

possible path (if any) satisfying the request and allocates the necessary resources in the 

network. 

PNNI enables the network to respond quickly to link failures, link recoveries, and 

changing network loads on any link. The network is able to adapt to changes in the 

addressing of a network or the topology of the network as switches are added or deleted.

Peer Groups

PNNI creates groups for the distribution of routing information through the network. 

These groups are called peer groups. A peer group should have topological significance in 

which all members of the group are in the same physical location.