Siemens HiPath 8000, Administrator'S Manual

Page: 176 / 249

Alphabetical Reference
176
Dial Plan
The dial plan of the phone should not be confused with the dial plan of the
server. Phone documentation uses the term “number plan” for the serv-
er’s “dial plan”. The phone’s terminology usage is supported by standards
– RFC.
The purpose of the dial plan is to reduce or remove the post dialling delay
caused by other methods of determining end of dialling – either use of a
timer or pressing of a “done” key. Both alternatives are supported by the
phone: the timer defaults to 6 seconds and the done key is either the tick
or lifting the handset.
The dial plan makes a critical assumption about the number plan – it is pos-
sible to determine the total number of digits required from the leading dig-
its. It does support a variable range of lengths for a given set of initial digits,
but in this scenario it is not as efficient and brings some restrictions.
It is possible to create a SIP number plan which prevents effective use of
the dial plan. If it is desired to use a dial plan, it has to be considered when
the number plan is created. Dial plans are supported by other manufactur-
er’s SIP phones.
A well planned dial plan can significantly impact on a user’s perception of
the system. Absence of a dial plan gives the appearance of a slow system.
A bad dial plan gives a view more akin to “sometimes it’s very slow” – the
user sees both fast and slow responses.
The Make-up of a Dial Plan
Currently a dial plan is restricted to 48 entries. This figure was believed to
be “enough” while avoiding excessive searching.
Each entry consists of a number of fields:
• Leading digits – a string to match the dialled digits against. Both * & #
can be included. There is also the wildcard X to represent any single
digit. There is no “any sequence” value.
• Action(s) – Originally, there were two, but these have been joined by a
third.
– S – Send the digits when the maximum digits have been received or
if the timer expires after the minimum digits have been received or
on receipt of the terminator after the minimum digits.
– C – Check for other actions. Minimum and maximum must match the
length of the string. The timer is run at this point only; sending will
occur on expiry. If more digits are received, further entries will be
checked. It is possible to use C in combination with D and have no
timer.
– D – Give secondary dial tone when the leading digits match. This ac-
tion does not depend on later parameters. In theory, there is a choice
of 9 tones, but only digit 1 is currently valid. D can be used in combi-
nation with C or S.
• Minimum length – Automatic sending will not occur until at least this
many digits have been dialled.