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Resource sizing
Issue 6 January 2008 199
Signaling resources
The TN799DP C-LAN and the TN2312BP (IPSI) circuit packs are the primary signaling traffic
bearing components residing within a port network. Both have finite internal resources such as
sockets and data-link connection identifiers (DLCIs) for assignment to and use by endpoints. In
addition, both components, being circuit packs, have firmware running on processors with finite
capacities to process signaling traffic. Therefore resource sizing the IPSI and the C-LAN
involves both tracking the sockets/DLCIs and the signaling traffic throughput.
The TN799DP C-LAN circuit pack provides the interface for a signaling channel between an IP
endpoint and a packet bus (which ultimately interfaces with the Avaya server). When an IP
endpoint, G250 MG, G350 MG, or G700 MG registers to a C-LAN circuit pack, it allocates a TCP
socket dedicated to that endpoint or gateway, for as long as it remains registered. C-LAN
sockets are also required for the support of certain adjuncts.
Each C-LAN circuit pack has a finite number of C-LAN sockets. The total number of C-LAN
circuit packs that are required to support a particular system depends on the total required
number of C-LAN sockets, which in turn depends on the total number of IP endpoints, G250/
G350/G700 MGs, and adjuncts. An individual C-LAN circuit pack can support endpoints in
different Network Regions, even those that are not administered to communicate with each
other.
Sizing the TN2312BP IPSI circuit packs is a fairly straightforward process. The number of IPSI
circuit packs that are required in the system depends on the total number of C-LAN sockets that
are required, and the number of ISDN D-channels in the system. Specifically, each IPSI circuit
pack supports up to a combined total of 2,480 C-LAN sockets and ISDN D-channels. This is a
system-wide constraint, as opposed to a site-by-site constraint. For an IP-PNC system, each
PN must house exactly one IPSI circuit pack, neglecting duplicated IPSI circuit packs for
enhanced reliability. Therefore, if the C-LAN sockets and the ISDN D-channels indicate a need
for more IPSI circuit packs than the required number of PNs to support the TDM usage, more
PNs are needed (note that placing two active IPSI circuit packs in a single PN is not permitted).
In other words, the number of PNs must be large enough to fulfill both the TDM and the IPSI
requirements.
In a system utilizing a circuit-switched center stage an IPSI circuit pack is not required in each
port network. However, there are restrictions pertaining to how many port networks can be
supported by a single IPSI circuit pack.
If the number of port networks needs to be increased to satisfy the IPSI requirements, then the
TDM and media processing engineering processes must be redone (since an increased
number of port networks implies an increase in inter-port-network traffic). This is an iterative
process.
In addition to counting sockets and DLCIs in allocating C-LANs and IPSIs, a separate,
independent traffic engineering process involves modeling the signaling message traffic through
them. The rate of message traffic depends primarily on the call traffic at the endpoints and MGs
signaling through the sockets/DLCIs. Each call generates a certain amount of messages
between the endpoints and the server. The exact number and sizes of the messages depends
on the protocols involved. Combining the messages per call with a call rate gives estimates of