255-700-239
3-13
PacketStar
®
PSAX 4500 Multiservice Media Gateway User Guide
, Issue 2
Release 8.0.0
Chapter 3 System Features
User Interfaces
PNNI provides a method for signaling used to establish point-to-point and
point-to-multipoint connections across ATM networks. PNNI is based on the
ATM Forum UNI signaling, with mechanisms added to support source rout-
ing, crankback and alternate routing of all call setup requests in case of con-
nection setup failure.
The path selections for specific calls are based on route options provided by
PNNI messages. Load sharing between parallel paths is addressed by the
route determination algorithm, which provides options for such factors as
load sharing, cost, and override options.
Phase 3 of the Private Network-Network Interface feature enhancement
includes the additions of functionality from the ATM Forum PNNI standard
af-pnni-0055.000 Annex F
,
Hierarchy Configuration
, and
Appendix G, Minimum
Subsets
(all border node capable switching systems features). Ten hierarchal
levels are supported.
The PSAX 4500 allows up to 65,535 nodes (2 MB of memory), 100 PNNI
links per interface, 20 PNNI summary addresses, 50 PNNI advertised routes,
and 20 administrative weight entries per PNNI route.
PNNI Features
Supported by the
PSAX Systems
The following is a list of PNNI features supported for the PSAX systems:
•
Multiple peer group hierarchy
•
Alternate routing as a result of crankback
•
CBR, rt-VBR, nrt-VBR, and UBR service
•
Hello protocol
•
Peer group leader election algorithm
•
Point-to-point SVC and SPVC connections
•
Point-to-multipoint SVC and SPVC connections
•
Transfer of incoming extended Quality of Service (QoS)
•
End-to-end transit delay parameters to outgoing PNNI interfaces
•
Topology database synchronization
•
PNNI topology state element (PTSE) aging within topology databases
•
Summation and advertising of reachable addresses
•
Source path selection and generic connection admission control (GCAC)
PNNI Peer Group
Dynamics
PNNI performs these functions:
•
Simplifies the configuration of large networks because it allows ATM
switches to automatically learn about their neighbors and to distribute call
routing information dynamically.
•
Allows switches to be arranged in a hierarchy, where each level represents
one or more switches. A cluster of switches at the same level is called a
peer group. Link-state topology updates circulate within a peer group.
•
Allows up to 10 levels in a hierarchy but does not require them. It is also
possible to deploy PNNI with one peer group encompassing all switches
within a network.
