Volker Hilt

1
Event Package for Session-Specific
Policiesdraft-hilt-sipping-policy-package-01

• Volker Hilt
• volkerh_at_bell-labs.com
• Gonzalo Camarillo
• Gonzalo.Camarillo_at_ericsson.com

2
Status

• Should have been submitted as a WG item.
• Changes
• Submitting confidential information in SDP is
  addressed in security section.
• Content disposition type for policies changed to
• Type session-policy
• Parameters descriptionlocal / remote
• Clarified use of SDP extensions.
• Policy server can keep using the extensions the
  UA has used but cant add additional extensions.
• Depends on Policy Framework draft.

3
Session Policy Framework Draftdraft-hilt-sipping-
session-policy-framework-01
Volker Hilt volkerh_at_bell-labs.com Gonzalo
Camarillo Gonzalo.Camarillo_at_ericsson.com Jonathan
Rosenberg jdrosen_at_cisco.com
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Status Open Issues

• Should have been submitted as a WG item.
• Major open issue
• Session-specific policies how to submit session
  information to the policy server?
• Session-specific Policy Model
• Submit session description to policy server.
• Return a policy decision in form of a (possibly
  modified) session description.

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Option 1 PUBLISH/SUBSCRIBE
INVITE
INVITE
UA A
UA B
Proxy A
SD
PUBLISH
SP
SD
SUBSCRIBE
Policy Server A
NOTIFY
SP
6
Option 1 Discussion (1)

• PUBLISH and SUBSCRIBE enables that different
  entities publish the session description (e.g. a
  proxy) and receive policies (e.g. the UA).
• UA A PS B P B UA
  B
• INV lto'gt INV lto', ps
  urigt
• ----------------------------gt-------------gt
• PUBLISH lto'gt
• lt-------------
• SUBSCRIBE
• lt----------------------------
• NOTIFY ltpogt
• ----------------------------gt
• There is a potential for deadlocks!

Waits for a NOTIFY with answer policy before it
can sent 200 OK!
Waits for 200 OK to publish answer!
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Option 1 Discussion (2)

• UA and policy server need to maintain/refresh two
  soft states (for PUBLISH and for SUBSCRIBE).
• Two states need to be correlated.
• Many cases that need to be covered by
  implementations
• Subscription before publish.
• Publish before subscribe.
• Subscribe without a publish following and vice
  versa.

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Option 2 SUBSCRIBE Bodies
INVITE
INVITE
UA B
Proxy A
UA A
SD
SP
SUBSCRIBE
SD
NOTIFY
Policy Server A
SP
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Discussion

• Session descriptions and policy decisions are
  coupled.
• No need to correlate two states.
• Fewer cases to handle.
• Simple message flow.
• Only one soft state to establish and maintain.
• SUBSCRIBE body is used to generated policy
  decision.

10
Next Steps

• Proposal
• Stay with current mechanism based on SUBSCRIBE
  only.
• Finalize drafts.