What is Reverse Name lookup (RNL)?
Reverse number look-up is the process of mapping a
user’s number to a corresponding SIP-URI for the purpose
of routing calls over the IP network to multiple user
endpoints, including Office Communicator, the Office
Communicator Telephone Experience, and call-handling
options such as call forwarding and call answering.
Based on RNL result OCS decides if the call is outbound
When any internal user dials the number:
Services performs reverse number lookup on the
target phone number of each incoming call and matches
that number to the SIP-URI of the destination user.
Using this information, the Inbound Routing Component
forks the call to that user’s registered SIP endpoints.
User Services is a core component on all Front End
Servers and Directors.
dialed number should be normalized prior to performing
reverse number lookup. If the normalized number
matches the designated primary work number (see below
about Primary work number) of a user
with an Active Directory identity, the call is forked
to the endpoints associated with that user’s SIP-URI.
If the server does not find a match, which means the
target number is probably outside the enterprise, the
Outbound Routing component checks the caller’s phone
usage to determine if a call to that number is
authorized, and then either directs the call to the
appropriate media gateway or notifies the caller that
the call is not allowed.
an External User makes call to the internal user:
mediation Server Performs reverse number lookups to
resolve phone numbers from incoming calls arriving from
the media gateway to the corresponding SIP URI. After
Phone number numbers are resolved into SIP URIs, the
Mediation Server routes the call to the user’s home
See here the complete process...
communicator also do Reverse Name Lookup?
To resolve the Calling Party Number to a name,
Communicator first applies the number normalization
Regular Expressions configured in the Address Book
Service on the Office Communications Server 2007 pool on
the calling party Number. After that, Communicator 2007
matches the current E.164 format normalized Calling
Party Number with the phone numbers stored in Active
Directory or Outlook contacts. This functionality is
called Reverse Name Lookup. If Communicator 2007
successfully applies reverse number lookup and finds a
name that matches a Calling Party Number, this name is
presented to the user in the pop-up window and the
conversation window, instead of the Calling Party
CSTA implementations on PBX or IP PBX provide these
reverse number lookup functionalities. thus instead of
or in addition to the Calling Party number, a display
name is transmitted to communicator on an incoming call.
This display name is ignored by communicator 2007
because it is not possible for communicator 2007 to
verify the name.
is Primary Phone Number?
reverse number lookup, requires that each user be
associated with a primary phone number.
A Primary Phone Number must be:
• Globally unique or, in the case of internal
extensions, unique in the enterprise.
• Owned by and routable in the enterprise. Personal
numbers should not be used.
The Telephone number text box on the General
tab of the User Properties dialog should
contains the user’s main work number.
primary number is chosen, it must be:
Normalized to E.164 format, wherever possible.
• Copied to the Active Directory msRTCSIP-line
attribute (This is the same value what you enter in
Line URI field while enabling the user for Enterprise
Normalization of phone number at
the client end or server end?
When an External User (PSTN user)
makes call to the internal user.