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LoST Primer

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  1. LoST Primer Brian Rosen

  2. LoST (RFC5222) • Protocol to map a location and a “service urn” to a URI • Location is expressed with the “location information” part of a PIDF, essentially OGC GML point/polygon/circle/arcband • Service URN tells the server what service mapping is needed. We would use, e.g. urn:service:paws. Allows a LoST server to provide mappings for multiple services • Servers can use iteration or recursion to handle requests out of its service area

  3. LoST, con’t • LoST is defined as http transport with TLS using a Relax-NG schema • Originally defined to route emergency calls based on location to the right emergency call center (PSAP) • Now being extended to handle routing of other kinds of services (urn:service:pizza.pizzahut) • Full specification, with all the error conditions, referrals, formats, …

  4. Forest Guide • LoST servers are deployed in trees, with, roughly, nations at the top of the tree • For emergency services, next level might be state/province, and then possibly regional or local servers below that • The set of these trees is a “Forest” and there is a “Forest Guide” • The Forest Guide is used to handle a request that is out of service area of the tree • It refers (or recures) to another tree or another Forest Guide

  5. Forest Guides, con’t • The reason for Forest Guides is to avoid the “golden root” problem • Forest Guides are aware of each other and share coverage regions • “LoST Sync” is used to send coverage area to a Forest Guide and between Forest Guides

  6. Discovery of a LoST server • Could be configured • Could be discovered via DHCP

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