40 System description
The Leader, Backup Leader, Follower,and DCHIP cards communicate
through their ELAN network interfaces. For more information, see "Internet
Protocols and ports used by IP Trunk 3.01 (and later)" (page 130).
Follower
A Follower card is a Media Card 32-port trunk card and/or an ITG-Pentium
24-port trunk card which converts telephone signals into data packets and
data packets into telephone signals. For outgoing calls, Follower cards
provide dialed number-to-IP address translation.
Active Leader
The Active Leader card is an IP trunk card that acts as a point of contact for
all other Meridian 1/CS 1000 systems in the network.
The Active Leader card is responsible forthe following:
•distributing incoming H.323 calls to each registered Follower card in
its node and balancing load among the registered cards for incoming
IP calls
•IP addresses for other cards in its node (see "Interactions among card
functions" (page 44))
•serving as a time server for all IP trunk cards in its node
•performing network monitoring for outgoing calls in its node
•voice processing
All calls from a remote VoIPgateway node are first presented to the Active
Leader card. The Leader card maintains a resource table of all the IP trunk
cards in its node. The Active Leader card consults its internal IP trunk card
resource table to determine which card has the most idle channels and is
the least busy. Based on that information, the Active Leader card selects
the card to receive the new call.
In a multi-card IP Trunk3.01 (and later) node, the Active Leader is busier
than the Follower cards. As a result, the channels on the Follower cards
are used first. Only after most of the channels on the Follower cards and
Backup Leader card are in use does the Active Leader card assign an
incoming call to itself.
After a channel on a card has been selected, the Active Leader sends a
message to the selected IP trunk card telling it to reserve a channel for the
new call. The Active Leader redirects the call to the selected IP trunk card.
All subsequent messages are sent directly from the remote VoIP gateway
node to the selected card.
Nortel Communication Server 1000
IP TrunkFundamentals
NN43001-563 02.01 Standard
Release 5.5 21 December 2007
Copyright© 2007, Nor tel Networks
.