Call Usage Rates - Avaya Application Solutions Deployment Manual

Traffic engineering
Additional design criteria
Each site is to have a suitable number of PSTN trunks (which terminate on PNs in Atlanta
and Boston, and on the G350 Media Gateways in Cleveland).
This is a general business application (for example, no Call Center agents), where the
average usage per station is assumed to be 0.11 Erlangs, and the average call duration is
assumed to be 200 seconds.
Each site consists of a single Network Region, and all three Network Regions are
interconnected in the sense of the IRCM matrix.
One-third of all calls are intercom calls (that is, calls between two stations), one-third are
inbound PSTN trunk calls, and one-third are outbound PSTN trunk calls.
Preliminary calculations
Based on the assumption of 0.11 Erlangs per station,
endpoint type
Table 20: Example 1 station usage by endpoint type
Endpoints
DCP Telephones
IP Telephones
Analog stations
Road Warriors
Analog stations administered
to G350 Media Gateways

Call usage rates

In the previous section, station usages and overall endpoint usages, including both stations and
trunks, were discussed. The overall endpoint usage is sometimes referred to as port usage rate
(PUR). The term station usage rate (SUR) applies when referring only to the stations. In
general, a traffic usage rate, when expressed in Erlangs, represents the average number of
busy servers in a given server group. So, SUR represents the average number of stations in a
particular group that are simultaneously in use, while PUR represents the average number of
endpoints, including stations and trunks, in a particular group that are simultaneously in use.
146 Avaya Application Solutions IP Telephony Deployment Guide
shows the total station usage for each station category in the system.
Table 20: Example 1 station usage by
Atlanta Boston
(Erlangs) (Erlangs)
60 20
120 50
12 2
3
Cleveland
(Erlangs)
30
4