Traffic engineering
152 Avaya Application Solutions IP Telephony Deployment Guide
Again,
Table 22: Inbound COI matrix for the Uniform Distribution model in Example 2: Uniform
Distribution model
on page 151 and
Table 23: Outbound COI matrix for Uniform Distribution
Model in Example 2: Uniform Distribution model
on page 152 are constructed without
considering overflow traffic.These tables imply that the Site 1 PSTN trunks carry 98 Erlangs (49
inbound and 49 outbound) of traffic, the Site 2 trunks carry 36 Erlangs, and the Site 3 trunks
carry 16 Erlangs. Applying the standard Erlang loss model with a P01 GOS to each of the three
sites implies that at least 116 trunks are needed in Site 1, at least 49 trunks are needed in Site
2, and at least 26 trunks are needed in Site 3. Note that this constitutes a total of 191 trunks, as
opposed to the estimate of 171 trunks that was obtained without sizing the three trunk groups
separately. A total of 171 could be used to attain an overall grade of service of P01, but that
would induce a large amount of intersite traffic. The use of 191 total trunks, distributed between
the three sites as specified above, ensures that at least 99% of the calls are guaranteed to be
intrasite.
In some cases, there might be factors that justify overengineering the trunk groups. For
example, a customer who is based in North America most likely leases T1 trunk facilities
between each of its sites and the appropriate COs. In this example, it might be reasonable to
use five T1 facilities (that is, 120 DS0 channels) for Atlanta, three T1 facilities (that is, 72 DS0
channels) for Boston, and two T1 facilities (that is, 48 DS0 channels) for Cleveland. This yields
an overall GOS much better than P01, and at the same time, the use of standardized equipment
reduces costs. In fact, the use of Erlang’s loss formula implies a blocking probability of 0.004 in
Atlanta, and negligible blocking probabilities (that is, several orders of magnitude better than
P01) for the other two sites. These extremely low-blocking probabilities justify the assumption
that intersite trunk traffic (overflow traffic) is negligible in this example.
Finally, the entries for the intercom COI matrix must be determined. Of the 195 Erlangs of
station usage in that site, 49 Erlangs are associated with inbound calls, and 49 Erlangs are
associated with outbound calls. That leaves 195 - 49 - 49 = 97 Erlangs of station usage in the
Atlanta site for intercom calls. Similarly, there are 72 - 18 - 18 = 36 Erlangs of station usage in
the Boston site for intercom calls, and 34 - 8 - 8 = 18 Erlangs of station usage in the Cleveland
site for intercom calls.
Table 23: Outbound COI matrix for Uniform Distribution Model in
Example 2: Uniform
Distribution model
Outbound CUR
To trunks in Site __
1
2
3
From stations in Site
____
1
49 Erlangs
0
0
2
0
18 Erlangs
0
3
0
0
8 Erlangs
Summary of Contents for Application Solutions
Page 1: ...Avaya Application Solutions IP Telephony Deployment Guide 555 245 600 Issue 3 4 1 June 2005 ...
Page 20: ...About This Book 20 Avaya Application Solutions IP Telephony Deployment Guide ...
Page 21: ...Issue 3 4 1 June 2005 21 Section 1 Avaya Application Solutions product guide ...
Page 22: ...22 Avaya Application Solutions IP Telephony Deployment Guide ...
Page 106: ...Call processing 106 Avaya Application Solutions IP Telephony Deployment Guide ...
Page 124: ...Avaya LAN switching products 124 Avaya Application Solutions IP Telephony Deployment Guide ...
Page 139: ...Issue 3 4 1 June 2005 139 Section 2 Deploying IP Telephony ...
Page 140: ...140 Avaya Application Solutions IP Telephony Deployment Guide ...
Page 186: ...Traffic engineering 186 Avaya Application Solutions IP Telephony Deployment Guide ...
Page 204: ...Security 204 Avaya Application Solutions IP Telephony Deployment Guide ...
Page 228: ...Avaya Integrated Management 228 Avaya Application Solutions IP Telephony Deployment Guide ...
Page 274: ...Reliability and Recovery 274 Avaya Application Solutions IP Telephony Deployment Guide ...
Page 275: ...Issue 3 4 1 June 2005 275 Section 3 Getting the IP network ready for telephony ...
Page 276: ...276 Avaya Application Solutions IP Telephony Deployment Guide ...
Page 356: ...Network recovery 356 Avaya Application Solutions IP Telephony Deployment Guide ...
Page 366: ...Network assessment offer 366 Avaya Application Solutions IP Telephony Deployment Guide ...
Page 367: ...Issue 3 4 1 June 2005 367 Appendixes ...
Page 368: ...Appendixes 368 Avaya Application Solutions IP Telephony Deployment Guide ...
Page 394: ...Access list 394 Avaya Application Solutions IP Telephony Deployment Guide ...
Page 414: ...DHCP TFTP 414 Avaya Application Solutions IP Telephony Deployment Guide ...