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LbyV and LbyR Henning Schulzrinne
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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
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Scenarios LIS V or R LoST V V or R
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Issues Insertion Updates if target moving Size/overhead Mid-stream insertion Privacy policies Reliability Security –Encryption –Integrity
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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
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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
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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
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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
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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
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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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