INtermediary-safe SIP session ID
charter-ietf-insipid-02-00

An end-to-end session identifier in SIP-based multimedia communication
networks refers to the ability for endpoints, intermediate devices,
and management and monitoring system to identify and correlate SIP
messages and dialogs of the same higher-level end-to-end
"communication session" across multiple SIP devices, hops, and
administrative domains. Unfortunately, there are a number of factors
that contribute to the fact that the current dialog identifiers
defined in SIP are not suitable for end-to-end session
identification. Perhaps the most important factor worth describing is
that in real-world deployments of Back-to-Back User Agents (B2BUAs)
devices like Session Border Controllers (SBC) often change the call
identifiers (e.g., the From-tag and To-tag that are used in
conjunction with the Call-ID header to make the dialog-id) as the
session signaling passes through.

An end-to-end session identifier should allow the possibility to
identify the communication session from the point of origin, passing
through any number of intermediaries, to the ultimate point of
termination. It should have the same aim as the From-tag, To-tag and
Call-ID conjunction, but should not be mangled by intermediaries.

A SIP end-to-end session identifier has been considered as possible
solution of different use cases like troubleshooting, billing, session
tracking, session recording, media and signaling correlation, and so
forth. Some of these requirements come from other working groups
within the RAI area (e.g., SIPRec). Moreover, other standards
organizations have identified the need for SIP and H.323 to carry the
same "session ID" value so that it is possible to identify a call
end-to-end even when performing inter working between protocols.

Troubleshooting SIP signalling end-to-end becomes impractical as
networks grow and become interconnected, including connection via
transit networks, because the path that SIP signalling will take
between clients cannot be predicted and the signalling volume and
geographical spread are too large.

This group will focus on two documents, the first document will
specify a SIP identifier that has the same aim as the From-tag, To-tag
and Call-ID conjunction, but is less likely to be mangled by
intermediaries. In doing this work, the group will pay attention to
the privacy implications of a "session ID", for example considering
the possibility to make it intractable for nodes to correlate "session
IDs" generated by the same user for different sessions. The second
document will provide for adding an indicator to the SIP protocol
which can be used to mark signalling as of interest to logging. Such
marking will typically be applied as part of network testing
controlled by the network operator and not used in regular client
signalling. However, such marking can be carried end-to-end including
the SIP terminals, even if a session originates and terminates in
different networks.