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SIP Session Policies. Volker Hilt volkerh@bell-labs.com. History. Problem statement Enable the network to request the use of session policies from UAs. History draft-rosenberg-sipping-session-policy-00 draft-hilt-sipping-session-policy-00 draft-camarillo-sipping-policy-package-00

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Sip session policies

SIP Session Policies

Volker Hilt

volkerh@bell-labs.com


History
History

  • Problem statement

    • Enable the network to request the use of session policies from UAs.

  • History

    • draft-rosenberg-sipping-session-policy-00

    • draft-hilt-sipping-session-policy-00

    • draft-camarillo-sipping-policy-package-00

  • Session-Specific Intermediary Session Policies

    • draft-hilt-sipping-session-spec-policy-00

    • Created during a specific session.

    • Affect the current session.

  • Session-Independent Intermediary Session Policies

    • draft-hilt-sipping-session-indep-policy-00

    • Created outside of a session.

    • Affect selected sessions during a period of time.


Session independent policies 1
Session-Independent Policies (1)

Access Network

Policy Server

Home Domain

Policy Server

  • Overview

    • UAs subscribes to policies.

    • Policy documents conveyed

      through content indirection.

    • Defines a framework.

  • Open issues

    • Policy server discovery

      • Assumption: Session policies will most likely be provided by the access network domain and the home domain.

      • Policy server discovery would simplify deployment.

      • Issue: Current procedures overload user name “sessionpolicies”.

SUBSCRIBE

SUBSCRIBE

NOTIFY

NOTIFY

GET Policy

GET Policy


Session independent policies 2
Session-Independent Policies (2)

  • Open issues (cont.)

    • Policy documents

      • XCAP event package and XCAP-based documents.

        • Use the existing XCAP framework to deliver policies.

          • Define the general properties of policy documents.

        • But: XCAP event package assumes that the UAs know the path to the relevant documents.

      • XCAP-based policy documents.

        • Limits the number of protocols and document formats used in policy packages.

        • But: simple UAs may prefer plain HTTP and text documents.

      • Allow any policy document format.

  • How to proceed?


Session dependent policies 1
Session-Dependent Policies (1)

  • Overview

    • Policies are requested using MIO/MFO headers individually for each session during an offer/answer exchange.

    • Defines a framework.

  • Open issues

    • Preconditions

      • UAC may reject policies and terminate the session, which may cause “ghost rings” on the UAS side.

      • Use of precondition could prevent “ghost rings”.

    • Subsequent offer/answer exchanges

      • How to handle policies in subsequent offer/answer exchanges?

INVITE(offer) + MIO-1

INVITE(offer) + MIO-1 + MFO-1

MFO-1

MFO-1

MFO-2

OK(answer) + MIO-2 + MFO-1 + MFO-2

OK(answer) + MIO-2 + MFO-1

ACK + MFO-2

ACK + MFO-2

MFO-2


Session dependent policies 2
Session-Dependent Policies (2)

  • Open issues (cont.)

    • Two party consent vs. one party consent.

      • The current requirements are based on a two party consent model:

        • Both UAs need to know all policies (REQ-CON-1 and REQ-CON-2)

        • Proxies need to know the accepted policies (REQ-CON-5 and REQ-CON-6).

      • Two party consent requires a three pass policy exchange.

      • But: the third pass does not exist in “empty” INVITE and UPDATE flows.

      • Approach 1: Two party consent

        • Send policy information in a separate message (SUBSCRIBE/NOTIFY, INFO,...).

      • Approach 2: One party consent (as discussed for OPES in RFC3238)

        • Only one UA needs to know about and agree to a policies.

        • Since each UA can set up a session policy locally, one party consent does not change the current model.

        • Works with the two-way offer answer model.

  • How to proceed?