TELECOM Digest OnLine - Sorted: Re: Call Forwarding and "Dialed Number" Information

Re: Call Forwarding and "Dialed Number" Information

r.e.d. (
Wed, 10 May 2006 16:29:36 GMT

It's been a long time since I've looked at this, but I think the
capability you want is supposed to be addressed by the ISDN
"Redirecting Number" Information Element.

Easier said than done. I have an August 1996 copy of AT&T Technical
Reference 41459, the ISDN Primary Rate Interface (PRI) Specification.
I don't know if it's been changed since then, but In Appendix 1,
Service Specific Capabilities it says:

1.5 Existing Capabilities Description
1.5.1 Call Processing Number Digits
The number digits supported are as specified in the Overview, with the
following exceptions: The description about the use of the Called
party subaddress, Calling party subaddress, Redirecting number, and
Connected number information elements is not applicable since these
information elements are not supported.

As to the main body of 41459, there are scattered references
throughout it to the Redirecting Number IE. Its applicability to the
cellular network I really don't know. VoIP people probably can speak
to this as well.

Some 41459 quotes:

PART III - Layer 3 Implementation Redirecting Number

The purpose of the Redirecting number information element is to
identify the number from which a call diversion or transfer was
invoked.(footnote 3) This information element may not be interpreted
by the network. Hence, the network may only need to recognize the
information element identifier. The maximum length of this
information element is 20 octets.

(footnote 3.) If Redirecting Number is user generated, then it is
transported as MA UUI and will not be interpreted by the network. If
it is network generated, then it is not transported as MA UUI and will
be interpreted by the network.

Note 3: At the redirecting user-network interface, the presentation
indicator is used for indicating the intention of the redirecting user
for the presentation of the redirecting number to the called user.
This may also be requested on a subscription basis. If octet 3a is
omitted, and the network does not support subscription information for
the redirecting number information restriction, the value "00 -
presentation allowed" is assumed.

Under Message Associated User-to-User Signaling (MA-UUI)

In addition to the User-user information element, the network may
treat the following information elements as user data information
elements when present in the appropriate messages (listed with their
MA UUI length restrictions):

- Called party subaddress (3-23 octets),
- Calling party subaddress (3-23 octets),
- High layer compatibility (3-5 octets),
- Low layer compatibility (3-16 octets),

- Redirecting number (3-17 octets),
- Locking Shift to Codeset 6 and any Codeset 6 information elements (1-129
octets), and
- Locking Shift to Codeset 7 and any Codeset 7 information elements (1-129

This all may not help much, but maybe it gives you a starting point.


Reply to "red99" (not "rednospam99")

Biren <> wrote in message

> I have a question about call forwarding and availability of "dialed
> number" (this could be applicable to both landline and GSM phones):

> Some user has set up his/her phone (with number A) to forward "all"
> incoming calls to a certain number B (using sequence *21*B# for GSM)
> and some caller C calls in A's number.

> Is there any way we can obtain "original dialed number" (i.e. A) at
> site B -- before deciding to respond to the forwared call? At site B,
> caller ID provides original caller (i.e. C) -- but can we correctly
> obtain "called id" by some means? Is it available at all?

> If number B is an 800 (or other toll-free) number with ANI/DNIS
> service, can we get the originally dialed number?

> Thanks.

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