URI authority resolution

["Wachob, Gabe" <gwachob@visa.com>]

Dave McAlpin had suggested we want to come up with a better method for resolution for XRIs with URI authorities (ie DNS or IP addresses) than the current method of converting the XRI into a HTTP URL and performing the HTTP protocol on the new HTTP URI.

I do not believe we have discussed an alternative resolution mechanism, so here's my proposal:

1) Take the authority identifier (an IP address or DNS name) and construct a HTTP URI that consists of "http://"; + the dns name or IP address. 

2) Perform an HTTP GET on the resulting HTTP URL

3) The result of the HTTP GET will be a XRIDescriptor as would normally be returned per XRI Authority resolution, possibly signed.

For example, resolving the authority for xri://wachob.com/foo would cause a HTTP GET to http://wachob.com which would result in the XRID for xri://wachob.com

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An enhancement to consider would be the use of SRV records (when available) when a DNS name is used. The publication of an SRV record would be optional, but would allow more flexibility on the part of the authority. The process would then be:

1) Take the authority identifier which is a DNS name. (if an IP address, then use the above algorithm) 

2) Add _xria._http._tcp to the front of the DNS name (as per SRV spec - RFC 2782 http://zvon.org/tmRFC/RFC2782/Output/index.html)

3) The resulting domain name and port number (from the resulting SRV record) would be used to construct a HTTP URL. Note that the domain name could be "xri-specific" allowing use of a generic domain name in the XRI, but resulting in a HTTP request (step 4) to a XRI-authority specific URL. If the SRV record doesn't exist, then just construct the HTTP URL as in the above algorithm. 

4) Perform an HTTP GET on the resulting HTTP URL (constructed from the SRV resolution)

5) The result of the HTTP GET will be a XRIDescriptor as would normally be returned per XRI Authority resolution, possibly signed.

So, for example, resolving the authority for xri://wachob.com/foo would be cause the following steps:

1) Resolve _xria._http._tcp.wachob.com SRV record, resulting in host xri-auth.wachob.com port 80

2) Perform HTTP GET to xri-auth.wachob.com on port 80 which would result in the XRID for xri://wachob.com

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Please let me know what people think about these proposals and whether they are worth the effort to include in the resolution specification.

	-Gabe

__________________________________________________ 
gwachob@visa.com
Chief Systems Architect
Technology Strategies and Standards
Visa International 
Phone: +1.650.432.3696   Fax: +1.650.554.6817