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LbyV and LbyR

LbyV and LbyR. Henning Schulzrinne. Definition. LbyR Consumers (recipients) of location information resolves URL and obtains location value LbyV Target (or proxy) inserts & delivers location value to all or some consumers in signaling path LbyV-plain: as-is

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LbyV and LbyR

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  1. LbyV and LbyR Henning Schulzrinne

  2. Definition • LbyR • Consumers (recipients) of location information resolves URL and obtains location value • LbyV • Target (or proxy) inserts & delivers location value to all or some consumers in signaling path • LbyV-plain: as-is • accessibility the same as carrying protocol (say, SIP) • LbyV-SMIME: encapsulated in S/MIME • Targeted to one (logical) receiver

  3. Scenarios LIS V or R V or R V LoST

  4. Issues • Insertion • Updates if target moving • Size/overhead • Mid-stream insertion • Privacy policies • Reliability • Security • Encryption • Integrity

  5. Insertion • LbyV • Can be inserted by end system • Can be inserted by proxy • Via data: URL in header • LbyR • Same • Via header addition • Same issues for privacy policies

  6. Privacy policies • Whenever LO is generated by third party, unclear how in-band privacy policies are configured • generator may not know intended use (pizza delivery vs. emergency call) • Issue for LbyR or LbyV proxy-insertion • may be solvable by configuration mechanism

  7. Updates for moving targets • LbyV • Target has to push (UPDATE, re-INVITE) • But it knows when location has changed significantly • May be difficult if inserted by proxy • LbyR • Receiver polls LIS or subscribes to LIS or target • Polling: may not know when location is changing

  8. Reliability • LbyR • Recipient needs protocol transaction to get LO • Thus, two points of failure • Impact on reliability depends on relative failure probabilities of the two parts • LbyV • “fate sharing”: no signaling without location • Thus, one point of failure

  9. Overhead • LIS likely close to target • Details depend on assumptions • Cost of one hop is constant or distance-dependent • LbyR: Each retrieval one additional protocol exchange • With headers, TCP setup, TLS, as applicable • LbyV: • Additional LO in message

  10. Access control • LbyR • Anybody who has access to reference • Unless • desired recipient has a security relationship with LIS AND • rule maker can access authorization upload policies to LIS • LbyV • Anybody who has access to value • Unless • Target can encrypt value for recipient • Single target: S/MIME, encrypted with recipient’s public key

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