Nortel 1000 Description, Installation And Operation Manual page 137

ITG engineering guidelines Page 137 of 644
Additionally, the DCHIP card sends and receives all D-channel messages
from the system to all Follower cards. In a multi-card node, the DCHIP card
CPU real-time must be engineered to reserve enough capacity to successfully
transmit and receive D-channel messages.
Card role
IP Trunk cards have various roles. Each role is affected by the amount of
traffic in varying degrees. The following card roles are listed in order from
the most impacted by call volume to the least affected by call volume:
DCHIP card role
Generally, the number of available voice ports on the IP trunk card having the
DCHIP card must be engineered as either the number of cards per node and/or
the traffic rate per node increase. Single card nodes are a special case for
DCHIP functionality, as the DCHIP traffic both originates and terminates on
the same card. This is the opposite of a multi-card node configuration, where
the DCHIP traffic originates and terminates across the IP LAN. With IP
Trunk 3.01 (and later), there is no additional work for the DCHIP role
whether the calls are Gatekeeper-routed or not.
Leader card role
The Leader card plays a role in all call termination as the owner of the Node
IP address and the resource (port) availability manager for the node. The
Leader card also maintains the functionality for QoS probing generation and
termination for the node. For this reason, the number of available voice ports
on the Leader card must be engineered inversely to the total number of IP
Trunk 3.01 (and later) nodes with QoS enabled in the IP Trunk 3.01 (and
later) TLAN subnet. IP Trunk 3.01 (and later) registers and re-registers with
a Gatekeeper. Unless the Time To Live (TTL) value is extremely low (under
15 seconds), the TTL has a very minor effect on the Leader card.
Single card role
The role of the IP trunk card in a single card node should not be impacted by
real-time limitations. The only consideration that limits the capacity of a
single Card node is the number of QoS endpoints being monitored. This has
the same effect on single card nodes as it does on Leader cards. As for all
cards with voice channels, there is an increase in the amount of work involved
with Gatekeeper-routed calls. This increase in most cases, is not significant
enough to affect most customer configurations.
IP Trunk Description, Installation, and Operation