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 –accessibility the same as carrying protocol (say, SIP) LbyV-SMIME: encapsulated in S/MIME –Targeted to one (logical) receiver

Scenarios LIS V or R LoST V V or R

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

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

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

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

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

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

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