Subject: [core] HTTP/CoAP default embedded URI mapping: requirements

From: "Dijk, Esko" <[email-masked]>
Date: Wed, 8 May 2013 08:35:03 +0000

Dear all,

the authors of draft-castellani-core-http-mapping discussed solutions for a default URI mapping for reverse HTTP-to-CoAP cross-protocol proxies. In other words, how to embed a CoAP URI into a HTTP URI. Because multiple solutions were identified, we decided to draw up some requirements to compare any solutions that may be proposed.

Below is the current list of requirements (roughly from highest importance to lowest):

R1. Syntactic correctness of the HTTP URI (e.g. handle percent-encoding when needed);

R2. HTTP URI must be able include all elements of a CoAP URI
    (e.g. coap(s) scheme, hostname, host literals IPv4/IPv6, port, path, query components, characters allowed in CoAP URI)

R3. The mapping operation must produce a string that can be directly used by a proxy as input to the process of core-coap section 6.4. "Decomposing URIs into Options".

R4. HTTP URI should be easily readable/writable by humans, if possible;
    (e.g. easy to read the CoAP URI embedded in it; avoid multiple levels of percent encoding, etc.)

R5. HTTP cache friendliness of the mapping solution, i.e. maximize the caching of CoAP resources by HTTP intermediaries;
   (e.g. a solution where entire CoAP URI is provided as a single query parameter is bad in this respect)

R6. Normalised form: preferably there should be only one "normal"/default way to encode the URI
    (e.g. so that we don't end up with multiple different cache entries for the same CoAP resource in intermediaries.);

R7. HTTP URI should be as short as possible.

Any input on these requirements is welcome. We'll send a selection of our proposals to the list shortly.

Esko & co-authors

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