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PATH Open Issues. Dean Willis SIP WG IETF 53. Scenario. I. FCP. UA1. Fire Wall. P. R. Visited Net. Home Net. UA2. REGISTER Path. I. FCP. UA1. Fire Wall. P. R. UA2. INVITE Path. I. FCP. UA1. Fire Wall. P. R. UA2. Problem.
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PATH Open Issues Dean WillisSIP WG IETF 53
Scenario I FCP UA1 FireWall P R VisitedNet HomeNet UA2
REGISTER Path I FCP UA1 FireWall P R UA2
INVITE Path I FCP UA1 FireWall P R UA2
Problem • How does Home Network direct INVITE through FCP on visited network • DNS magic? Requires PTR -> SRV mapping • REGISTER magic • Contact Modification by FCP (E2E Bad) • RecordRoute on REGISTER
Proposal • Record-Route on REGISTER • Store this route in registrar database • Apply as outbound Route header from home proxy
Issue: Header Name • Can’t call header record-Route as this is explicitly disallowed by bis text. • Propose “Path” as header name based on suggestion from 3GPP CN1 • Other Suggestions: RegisterRecordRoute, etc. • Discussion?
Issue: Security • Subject to manipulation by intermediate proxies. • With intermediate proxy, UA can’t directly authenticate identity of Registrar. • Path may encourage (or allow) use of network designs that require intermediate proxies. • Is this a “new” problem?
Issue: Transparency • OPES suggests it is not a good idea to insert things in a processing path without the consent of the requestor • Path: header is returned to UA, which then gains visibility on insertions. • Is this adequate?