Panasonic 1200N User Manual

Page of 256
Glossary
P
Centillion 1200N ATM Switch User Manual
B-59
NTP 297-8103-903
PNNI Routing Hierarchy 
The hierarchy of peer groups used for PNNI routing. 
PNNI Topology State Packet 
A type of PNNI Routing packet that is used for flooding PTSEs among logical 
nodes within a peer group. 
POH 
Path Overhead: A maintenance channel transmitted in the SONET overhead 
following the path from the beginning multiplexer to the ending demultiplexer. 
This is not implemented in SONET Lite. 
Point-to-Multipoint Connection 
A Point-to-Multipoint Connection is a collection of associated ATM VC or VP 
links, with associated endpoint nodes, with the following properties: 
 One ATM link, called the Root Link, serves as the root in a simple tree topology. 
When the Root Node sends information, all of the remaining nodes on the 
connection, called Leaf Nodes, receive copies of the information. 
Each of the Leaf Nodes on the connection can send information directly to the 
Root Node. The Root Node cannot distinguish which Leaf is sending 
information without additional (higher layer) information. (See note below for 
User Network Interface (UNI) 4.0 support) 
The Leaf Nodes cannot communicate directly to each other with this connection 
type. 
Note: UNI 4.0 does not support traffic sent from a Leaf to the Root. 
Point-to-Point Connection 
A connection with only two endpoints. 
Port Identifier 
The identifier assigned by a logical node to represent the point of attachment of a 
link to that node. 
Partial Packet Discard (PPD)
Partial Packet Discard (PPD) is a congestion control technique that drops all of the 
ATM cells in a Classical IP over ATM packet. When congestion occurs and any 
one cell of a particular frame is dropped, PPD discards the rest of the cells (since 
the frame is errored and will need to be sent again anyway).