Private and Public Calculation Plan Integration
Numbering affairs alter throughout the world. Altered countries use altered number
lengths and hierarchical affairs aural their borders. Also, telephony accessories manufacturers
and account providers use abnormal numbering. In an attack to standardize
numbering plans, the ITU developed the E.164 common prefix scheme.
Numbering plan affiliation from an centralized system, such as a VoIP and PBX system, to
the PSTN requires accurate planning. The hierarchical anatomy of the calculation plan and
the problems associated with capricious cardinal lengths in altered systems accomplish numbering
plan affiliation complex.
Following are some of the challenges you face with calculation plan integration:
■ Capricious cardinal lengths: Aural the IP network, application is accustomed to varying
number lengths that abide alfresco the IP network. Local, long-distance, key system,
and Centrex dialing from aural the IP arrangement ability crave chiffre manipulation.
■ Specialized services: Services such as Centrex and their equivalents about have
four-digit or five-digit numbers. Dialing from the PSTN into a clandestine VoIP network
and again out to a Centrex addendum can additionally crave all-encompassing chiffre manipulation.
■ Articulation mail: When a alleged affair cannot be reached, the arrangement ability accept to redirect
the alarm to articulation mail. Because the voice-mail arrangement can crave a altered numbering
plan than the endpoint telephones, adaptation is necessary.
■ Necessity of prefixes or breadth codes: It can be all-important to band or add breadth codes,
or prepend or alter prefixes. For example, rerouting calls from the IP arrangement to
the PSTN for abortion accretion can crave added digits.
■ International dialing consideration: Country codes and calculation affairs alter in
length aural countries. Dialing through an IP arrangement to addition country requires
careful consideration.
■ End user training and “ease of use”: As the calculation plan is actuality implemented,
time should be taken to alternation users on the new plan to abbreviate abashing as users
are switched over to the new plan. The added training the users get, the easier it is for
them to use the “new” system. Many VoIP implementations accept accustomed poor evaluations
by users, because users weren’t appropriately accomplished afore the arrangement switched
over to a new calculation plan.
Integration of Centralized and Public Calculation Affairs Example
Figure 6-12 shows how a aggregation integrates its centralized calculation plan with the external
public calculation plan.
354 Authorized Self-Study Guide: Cisco Articulation over IP (CVOICE)
San Jose
Austin
Access Cipher 5
51012
512...
1012
512...
PSTN
IP WAN
V V
V
Figure 6-12 Affiliation of Centralized and Public Calculation Plans
In this example, the PSTN will be acclimated as a advancement avenue for calls amid San Jose and
Austin. The afterward accomplish alarm how the San Jose router performs chiffre manipulation
based on the called route.
1. The San Jose addition dials the armpit admission cipher for Austin (5) followed by the fourdigit
extension cardinal of the destination buzz (1012).
2. The articulation aperture determines whether the alarm can be completed application the IP WAN
or whether it charge be baffled via the PSTN.
3. Chiffre abetment occurs based on the aisle chosen:
■ Band the armpit admission cipher and accelerate four digits if commutual the alarm beyond the IP
WAN.
■ Band the armpit admission cipher and prepend 1512 if commutual the alarm beyond the
PSTN.