Vijay, On 27 Jun 2011, at 17:23, Vijay K. Gurbani wrote:
> As individual ... > > In reference to [1], where we discuss whether or not there > should be a 1-1 relationship between an IP address and > a PID, and if it is not, how should we handle it? > > On 06/24/2011 10:46 AM, Ben Niven-Jenkins wrote: >> I think we should say something along the lines of what I suggest (it >> probably doesn't need to go in much, if any, more detail either) >> otherwise we risk interoperability issues where one client may >> interpret such a map as invalid while others do not. > > Ben: The bigger question to me is: is it indeed valid to have > a 1:N mapping between an IP address and a PID? If it is not, > then we leave this to the category of configuration errors and > not discuss how to handle it in the draft (the draft cannot > provide hedges against every MUST and MUST NOT). I have no issue with the current requirement that for a given IP address a client should be able to resolve one (and only one) PID via longest prefix matching and I'm not suggesting we change that. However I do think that a sentence or two on what it means when such a scenario happens is useful for interoperability. For example, if my client uses the network map service to obtain the complete network map and discovers that a particular IP address exists in two PIDs (i.e. a longest prefix match would return two PIDs), how is my client supposed to interpret the network map: a) Does it mean the entire network map is invalid and I should throw it all away? b) Does it mean those PIDs containing the duplicate IP address are invalid and I must disregard their complete contents but the rest of the map is useable? c) Does it mean that those PIDs containing the duplicate IP address are valid (along with the rest of the network map) provided I disregard the duplicate IP addresses? d) Does it mean I am allowed to make a local decision as to which PID is the correct PID for that IP address? IMO (a) & (b) require a client to fully validate the network map looking for duplicate IP addresses before using any portion of it can be considered useable. (c) & (d) allow a client to discover & recover from an inconsistency at "run time". Validating the entire network map before using it may not have a significant performance impact for an ALTO client in some P2P software where the number of PIDs and IP prefixes in the network map is likely to be small, however for some CDN use cases it could well be the case that there are thousands of PIDs and millions of individual prefixes in a single network map. A simple example would be if one wanted to represent in an ALTO network map a geo-location database containing the entire global routing table. Ben _______________________________________________ alto mailing list [email protected] https://www.ietf.org/mailman/listinfo/alto
