Mitel SX-2000 - Manual (Page 232)

SX-200 General Information Guide
218 Revision A 50003510
customers with high traffic could give users enough speech paths by installing large PBXs with
more ports and thus more speech paths.
The introduction of digital systems replaced speech paths with call connections and channels.
Using time division multiplexing, a single piece of wire could now carry up to 32 simultaneous
conversations. The result was a system that was physically smaller but able to carry many
more calls. These systems were often referred to as non-blocking, implying that all users of
the system could be placing calls at the same time, and a lack of system resources would not
prevent any of these calls from being completed.
To improve system efficiency, PBXs are normally engineered so callers are competing for
limited system resources such as trunks. This contention allows the system to make better use
of trunks by scheduling callers on each trunk. Most users are unaffected by this as a higher
percentage of traffic in a system is traditionally with inside parties. Key Systems force users to
manually select outgoing lines as most of their traffic is external calls.
Another factor which must be considered is traffic peaks. Although most system analysis is
done using average traffic, maximum peaks must also be identified. If traffic in any period
exceeds these specified maximums, system performance will likely degrade, and
over-competition for resources may result. Once traffic drops below this peak, the system will
provide normal performance. When purchasing a system, ratings for system peak capacities
should be determined for your configuration rather than using the average figures for the product
line.
Here are some facts about the SX-200 EL/ML system relating to traffic.
(a) The systems provide for at least 200 simultaneous call connections. This means that 200
stations can talk to 200 other stations or trunks before call connections could create
blocking.
(b) In peripheral digital bays the concentration of ports to channels is 96:90. This means that
if only 90 devices are installed in a digital bay there is no possibility of blocking on channels.
Adding Datasets could increase the number of devices to the point where some blocking
for channels could occur. Statistically, however, there should be limited performance
impact.
(c) To withstand peaks in traffic, Mitel Networks rates its switches according to line size using
the very heavy traffic patterns stipulated in ATT0048.
Mitel Networks also tests the systems to ensure that they can withstand twice the traffic specified
for the line-size of the switch. This is to ensure that peak traffic will not impact system
performance under normal conditions.
The SX-200 EL/ML system also contains a traffic measurement package to help monitor actual
traffic patterns. This traffic information must be considered when additional lines and trunks
are added to an existing system. For example, information on dial tone delays may indicate a
need for additional receiver modules. Console pegs can indicate the need for additional console
positions. Trunk usage reports can indicate the need for additional trunks.
Use the traffic report figures as guidelines. Specific departments or trunks may not follow the
averages of the rest of the system. This should be understood and analyzed to ensure that
your system can meet the needs of all users.