T – Com (Deutsche Telekom)




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T – Com (Deutsche Telekom)



















Source*:

T Com, T332-2 (Roland Jesske)

Title:

SIP History Info used for the interworking of PSTN/ISDN Supplementary Services


Abstract: This document discusses the History Info Draft and for what service interworking it can be used.


The Call forwarding services are not interworkable in a easy way because with regard to the History Header special rules must be built for the interworking to ISUP Parameters. E.G the interworking of Redirection counter to a Index number and vice versa.

There ar also many possible call constructions regarding the forwarding services. Within ISUP there are 4 Call Forwarding services specified in Q.732. The definition of and Stage 2 description are shown in Q.82.


Service definitions:
The Call Forwarding Unconditional supplementary service permits a served user to have the network send to another number all incoming calls for the served user’s number (or just those associated with a specified basic service). The served user’s originating service is unaffected. If this service is activated, calls are forwarded no matter what the condition of the termination.
The Call Forwarding on Busy supplementary service permits a served user to have the network send to another number all incoming calls for the served user’s number (or just those associated with a specified basic service) which meet busy at the served user’s ISDN number. The served user’s originating service is unaffected.
The Call Forwarding on No Reply supplementary service permits a served user to have the network send to another number all incoming calls for the serviced user’s number (or just those associated with a specified basic service) which meet no reply at the served user’s ISDN number. The served user’s originating service is unaffected.
The Call Deflection supplementary service permits a serviced user to, in real time, request that the network redirects an incoming call addressed to the served user’s ISDN number to another number. The served user’s originating service is
The possible identified scenarios with regard to the interworking are the following:
At I-IWU

Call Forwarding appears in SIP Network or in the ISDN Network

CFB, CFNR, CFU, CD
At O-IWU

Call Forwarding appears in SIP Network or in the ISDN Network

CFB, CFNR, CFU, CD
And of course several concatenations of Call forwarding.

One main Functionality of the SIP network that can be used for the Call forwarding is the History Header.


With regard to ISUP and the supplemtary Service description in Q.732 the following Messages and Parameters are used for the call forwarding services.

Address complete message


Optional backward call indicators

Generic notification indicators

Redirection number

Redirection number restriction indicator

Call diversion information

Answer message


Redirection number

Redirection number restriction indicator


Call progress message


Optional backward call indicators

Event indicator

Generic notification indicator

Call diversion information

Redirection number

Redirection number restriction indicator


Connect message


Redirection number restriction indicator

Initial address message


Redirecting number

Redirection information



Original called number



The following parameter fields and codes are used to support the call diversion supplementary service.

H

G

F

E

D

C

B

A




Event information  No Interworking needed




Bits




G F E D C B A




0

0

0

0

0

0

1

ALERTING




0

0

0

0

0011

1

0

PROGRESS




0

0

0

0

1

0

0

CFB (see Note)




0

0

0

0

1

0

1

CFNR (see Note)




0

0

0

0

1

1

0

CFU (see Note)




Bit




H




0

No indication




1

Presentation restricted (see Note)

NOTE – These codes are used in national networks and can be used on the international interface on bilateral agreement. If these codes are used and conflicting information is received compared to the generic notification indicator and the call diversion information parameter, the latter takes priority.

Forward call indicators




Bit




H G ISDN user part preference indicator




0

0

ISDN user part preferred all the way

Optional backward call indicators




Bit




B

Call diversion indicator




0

No indication




1

Call diversion may occur

Original called number

Redirection information




Bits




C B A Redirecting indicator




01

1

1

Call diverted




1

0

0

Call diverted, all redirection info presentation restricted




Bits




H G F E Original redirection reasons




0

0

0

0

Unknown




Bits




K J I Redirection counter




Bit




L

Reserved for national use




Bits




P O N M Redirecting reason Reason Header




0

0

0

0

Unknown/not available




0

0

0

1

User busy




0

0

1

0

No reply




0

0

1

1

Unconditional




0

10

0

0

Deflection during alerting




0

1

0

1

Deflection immediate response




0

1

1

0

Mobile subscriber not reachable

Redirecting number

Redirection number

Redirection number restriction indicator







Bits




B A Presentation restriction indicator Privacy Header Field




0

0

Presentation allowed




0

1

Presentation restricted




1

0

Spare




1

1

Spare




Bits




H G F E D C Spare

Generic notification indicator




Bits




G F E D C B A




1

1

1

1

0

1

1

Call is diverting

Call diversion information




Bits




C B A Notification subscription option Privacy Header Field




0

0

0

Unknown




0

0

1

Presentation not allowed




0

1

0

Presentation allowed with redirection Nb




0

1

1

Presentation allowed without redirection Nb




Bits




G F E D Redirecting reason Reason Header(new Reason Values needed)




0

0

0

0

Unknown/not available




0

0

0

1

User busy




0

0

1

0

No reply




0

0

1

1

Unconditional




0

1

0

0`

Deflection during alerting




0

1

0

1

Deflection immediate response




0

1

1

0

Mobile subscriber not reachable

The following sections shows the proposed interworking for several Call forwarding scenarios.




  1. Interworking at the O-IWU with call forwarding in SIP

  2. Interworking at the O-IWU with call forwarding in ISUP

  3. Interworking at the I-IWU with call forwarding in SIP

  4. Interworking at the I-IWU with call forwarding in ISUP


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