Gcac; Addressing; Iisp Overview; Supported Uni Signalling Versions - Cabletron Systems 9A656-04 Configuration Manual

Chapter 4: Signalling and Routing

4.3.4 GCAC

GCAC (generic Call Admission Control) is used by switches supporting PNNI to increase the
chances that a requested connection can be supported by all switches in the determined path.
Since each ATM switch in the path may perform CAC in a different way, it is necessary for a
generic CAC to examine the current state of the network topology (via current topology state
information provided by the PNNI protocol) to determine if the switches will be able to
support a requested connection. This is part of the PNNI 1.0 specification, and all ATM
switches supporting PNNI 1.0 will perform GCAC. Through this process, the first switch will
attempt to route the call to switches that it estimates will be able to meet the QoS
requirements, reducing the chances of crankback occurring extensively throughout the
network, thereby making the network more efficient.

4.3.5 Addressing

PNNI switches advertise their reachable addresses to the other members of their peer groups.
Whenever possible, these addresses are summarized. This is done via advertising one or more
common address prefixes that the range of addresses share. This restricts the amount of data
PNNI switches produce when advertising their addressing information and reduces the size of
the address database. If there are any addresses that can not be summarized, the full addresses
are advertised to the peer group members.
4.4

IISP OVERVIEW

IISP, also referred to as PNNI Phase 0, ensures ATM switch vendor inter-operability across the
ATM network using legacy (pre-PNNI 1.0) ATM switches. IISP requires static routes to be
configured between switches. The SmartSwitch 9500 supports IISP 3.0, 3.1 and 4.0 protocol
stacks on each interface. Each interface may be configured by the user via the MIB commands
covered in the following sections, but may also be autoconfigured.

4.4.1 Supported UNI Signalling Versions

The 9A686-04 supports the following UNI Signalling specifications for IISP connections:
• UNI 3.0
• UNI 3.1
• UNI 4.0

4.4.2 UNI Sides

The 9A686-04 supports both network and user side UNI Signalling for IISP connections.
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