Determine local carrier of the number called

I am interested in knowing how to determine the local carrier of the number called. Is there some sort of carrier identification code used for billing purposes of the number called? Thanks in advance.

Unlikely on ISDN. No on SIP. In any case, in some countries, the billing may be determined by the number dialled, not the final carrier, because of number portability.

Thanks for replying. I was hopeful that the SIP string segment “o=CARRIER 1310555235” was some sort of carrier code that could be referenced. Do you know off-hand what that is?

It is an SDP field, not a SIP one, which means it only relates to the RTP on the current hop, not to the final destination, unless it is being abused.

In fact, CARRIER is data, not a reserved word. It is a field defined as follows:

is the user’s login on the originating host, or it is "-"
if the originating host does not support the concept of user IDs.
The MUST NOT contain spaces.

The full o= lines syntax is:

  o=<username> <sess-id> <sess-version> <nettype> <addrtype>

nettype, addrtype and unicast-address all refer to the IP settings. see-id and sess-version are opaque numbers (except that sess-version must increase at certain times).