ForeRunner ATM Switch Network Configuration Manual
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PNNI
CHAPTER 6
ATM Forum PNNI
PNNI (Private Network Node Interface or Private Network-to-Network Interface) is a scalable
protocol that defines both the routing and signalling standards for interoperability between
private ATM switches. PNNI simplifies large network topologies by organizing the nodes in a
network into smaller groups. Through this re-organization, PNNI reduces the amount of
topology information that those nodes must maintain.
This chapter provides an overview of FORE Systems’ implementation of ATM Forum PNNI
(hereafter referred to as PNNI), and its use in a multiple-switch network. To understand
PNNI, it is important to first understand how PNNI’s routing and signalling protocols work.
6.1 PNNI Routing Protocol
The PNNI routing protocol enables the distribution of topology and address reachability
information between switches and groups of switches. Reachability information is the data that
explains how to contact a single ATM address or a group of ATM addresses that are summa-
rized by a single prefix. This information is used to compute routes across the network. The
key elements of the PNNI routing protocol are as follows:
•
Hello Protocol
•
Database Exchange Protocol
•
Flooding Protocol
•
Path Computation
•
Hierarchical Routing
6.1.1 Hello Protocol
The Hello protocol is used to discover and verify the identity of neighbor nodes and to deter-
mine the status of the logical links to those nodes. Logical links between nodes in the same
peer group are called horizontal links. Hello packets are exchanged at regular intervals over
links connecting neighboring nodes. Initially, these packets are used to exchange identities
between the nodes and to determine if they belong to the same peer group. After that, Hello
packets are used as keep-alive messages for the links over which the packets are exchanged.
After a configured number of hello intervals have passed without receiving a hello message,
the link is declared to be down.
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Страница 144: ...3 58 ForeRunner ATM Switch Network Configuration Manual Configuring an Emulated LAN ...
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Страница 220: ...9 6 ForeRunner ATM Switch Network Configuration Manual Configuring Timing ...
Страница 300: ...D 24 ForeRunner ATM Switch Network Configuration Manual Configuring FramePlus Modules ...
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