PGlossary
B-56 Centillion 1200N ATM Switch User Manual
NTP 297-8103-903
PDH
Plesiochronous Digital Hierarchy: PDH (plesiochronous means nearly
synchronous), was developed to carry digitized voice over twisted pair cabling
more efficiently. This evolved into the North American, European , and Japanese
Digital Hierarchies where only a discrete set of fixed rates is available, namely,
nxDS0 (DS0 is a 64 kbps rate) and then the next levels in the respective multiplex
hierarchies.
PDU
Protocol Data Unit: A PDU is a message of a given protocol comprising payload
and protocol-specific control information, typically contained in a header. PDUs
pass over the protocol interfaces which exist between the layers of protocols (per
OSI model).
Peer Entities
Entities within the same layer.
Peer Group Level
The number of significant bits in the peer group identifier of a particular peer group.
Peer Node
A node that is a member of the same peer group as a given node.
PES
Packetized Elementary Stream: In MPEG-2, afte r the media stream has been
digitized and compressed, it is formatted into packet s before it is multiplexed into
either a Program Stream or Transport Stream.
PG
Peer Group: A set of logical nodes which are grouped for purposes of creating a
routing hierarchy. PTSEs are exchanged among all members of the group.
PGI
Peer Group Identifier: A string of bits that is used to unambiguously identify a peer
group.
PGL
Peer Group Leader: A node which has been elected to perform some of the
functions associated with a logical group node.