Cac-Bl Description - Avaya MCC1 Maintenance Procedures

Additional maintenance procedures
Call Admission Control-Bandwidth Limitation

CAC-BL description

In order to ensure Quality of Service for Voice over IP calls, there is a need to limit overall VOIP traffic
on WAN links. The Call Admission Control-Bandwidth Limitation feature of Communication Manager
allows the customer to specify a VOIP bandwidth limit between any pair of IP network regions, and then
to deny calls that need to be carried over the WAN link that exceed that bandwidth limit.
In Communication Manager, a geographic area of high bandwidth availability, for example the LAN, or
Campus, is described as an IP network region. IP network regions are generally connected to other
regions by much lower bandwidth WAN facilities. Bandwidth within a single network region is
considered infinite. Bandwidth between a pair of network regions is clearly finite.
Using existing IP network region administration, a customer may presently configure different voice
codec sets that allow voice quality to be optimized within areas with high bandwidth inter-connectivity,
or allows efficient bandwidth utilization across areas of low bandwidth inter-connectivity. The existing
codec set configurations for intra and inter-region connectivity do not, however, allow explicit bandwidth
limits to be set. Through existing IP trunking mechanisms, IP trunk VOIP traffic can be limited to
discrete numbers of calls.
With the introduction of S8700 media servers and gateways, IP bandwidth is now also consumed for
inter-gateway/ inter-PN calls, as well as IP trunk calls. Prior to the introduction of CAC-BL, there was no
way at the present time to limit the bandwidth used for inter-gateway/inter-PN calls. Nor is there a way to
limit the bandwidth used by IP telephones to other IP telephones or gateways. Today, when the available
bandwidth is exceeded, new calls are allowed to go through, which may degrade the voice quality of the
new calls and existing calls, as well.
The CAC Bandwidth Limitation feature allows explicit static bandwidth limits to be administered for all
inter-region IP bearer connections. The administered bandwidth limits operate on all IP bearer
connections. Bandwidth limits can be administered in terms of:
• Kbit/sec WAN facilities
• Mbit/sec WAN facilities
• Explicit number of connections
• No limit
IP network region pairs may be considered to be directly connected, or indirectly connected. Indirectly
connected region pairs are connected through other directly connected region pairs. In this phase of the
CAC Bandwidth Limitation feature, Communication Manager will only allow administration of one path
between non-adjacent IP network regions, if needed. In many instances, the network can be modeled as
though non-adjacent IP network regions are directly connected.
The CAC Bandwidth Limitation feature monitors the voice traffic bandwidth utilization across the
various WAN links based on algorithms computed for each voice connection that goes over those links
(using various parameters such as codec selection).
When the bandwidth limit is reached between any two regions, the feature does not allow any additional
IP connections between those regions. Communication Manager re-routes the call according to existing
administration:
• A coverage path
• Searching for another agent
• The next trunk group in a route pattern
378 Maintenance Procedures
December 2003