The History Info extension defined in RFC7044 sets a way for an INVITE to include where the session (call) has been before that.
For example a call may be made to a desk phone, which is forwarded (302) to a home phone. The History Info extension would add a History Info header to the INVITE to the home phone, denoting the call had come to it via the desk phone.
Here the home phone can see the call first tried [email protected], at the same time tried [email protected] and [email protected] and [email protected], base don the index values.
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