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.
![](https://nickvsnetworking.com/wp-content/uploads/2019/05/SIP_History-Info.png)
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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