Yes. Agreed. With yours and Dino's explanation, I understand why LISP needs those "more specific" prefixes. The original wording just doesn't seem straightforward enough.
OK. I'll keep track of them for your future revision. Thanks, Richard -----Original Message----- From: Joel Halpern Direct [mailto:[email protected]] Sent: Wednesday, October 21, 2015 3:41 PM To: Richard Li; LISP mailing list list Subject: Re: [lisp] looking for clarifications on rfc 6830 Looking at the text, there are two different references. The first part talks about "a Map-Request with n EID that best matches any EID-prefix MUST be returned." This is correct. The Map-Reply must include the EID-prefix which best-matches the EID from the request. The grammar is a bit awkward in trying to say that if any other prefixes need to be returned along with that, they need to go in the same Map-Reply message. But the text is not incorrect. And the later text makes it clear that the prefixes that must be included are the more-specific prefixes within the best-match. The current structure is important in part because conceptually there may be other reasons why a set of prefixes need to be sent. Still, I would ask that you help us keep track of the fact that thsi third paragraph of 5.3 could be worded better. Yours, Joel On 10/21/15 6:16 PM, Richard Li wrote: > Thanks for your answers. > > Speaking about the Best-Match Prefixes, the RFC asks for returning all > best-matched prefixes. For the example in the RFC, The prefix > 10.1.2.0/24, for example, is NOT a best-match prefix, but the RFC > still wants to return it. This is exactly where the confusion comes > from. > > After reading your explanation, it comes to my mind that it is better > off to introduce a concept like "more specific" and "less-specific". > > 10.1.2.0/24 is "more specific" than 10.1.0.0/16, and 10.0.0.0/8 is > "less-specific" than 10.1.0.0/16. > > Using "more specific", the RFC could be rephrased as something like > this: It will return the best-match prefix and all prefixes that are > more specific than the best-match prefix. > > For the example in the spec, a Map-Request for EID 10.1.5.5 would > cause a Map-Reply with a record count of 3 to be returned with mapping > records for EID-Prefixes 10.1.0.0/16, 10.1.1.0/24, and 10.1.2.0/24, > since 10.1.0.0/16 is the best-match prefix and the other two are more > specific than the best-match prefix. > > Does the above make sense? > > Richard > > > -----Original Message----- From: Joel M. Halpern > [mailto:[email protected]] Sent: Monday, October 19, 2015 12:02 PM > To: Richard Li; LISP mailing list list Subject: Re: [lisp] looking for > clarifications on rfc 6830 > > Thank you for reading RFC 6830 carefully. My understanding of the > answers to your questions is in line below. Yours, Joel > > On 10/19/15 2:43 PM, Richard Li wrote: >> Hi Folks, >> >> I have read RFC 6830. I have a few points I could not figure them out >> by myself. Appreciated if you could clarify them. >> ... >> 3.Best-Match Prefixes >> >> Page 35, Section 6.1.5: >> >> A Map-Request for EID 10.1.5.5 would cause a Map-Reply with a record >> count of 3 to be returned with mapping records for EID-Prefixes >> 10.1.0.0/16, 10.1.1.0/24, and 10.1.2.0/24. >> >> Take a look at the EID prefixes in binary: >> >> 00001010.00000000.00000000.00000000 (10.0.0.0/8) >> >> 00001010.00000001.00000000.00000000 (10.1.0.0/16) >> >> 00001010.00000001.00000001.00000000 (10.1.1.0/24) >> >> 00001010.00000001.00000010.00000000 (10.1.2.0/24) >> >> 00001010.00000001.00000101.00000101 (10.1.5.5/32) >> >> Performing the best match of 10.1.5.5/32 against the EID prefix >> database, we will have only 10.1.0.0/16. > > I am not sure what your question is here. The reason the extra > entries (beyond 10.1.0.0/16 have to be returned is not that one of > them matches the request. Youa re correct, and the text agrees, that > there is only one entry matching 10.1.5.5/32. The reason the extra > entries need to be returned is that in the absence of those entries, > later packets which match those other entries will be misdirected. Is > the text insufficiently clear about the reason for sending the > additional entries? If so, can you suggest text improvement for us to > use in the next revision? > >> >> Thanks, >> >> Richard >> >> >> >> _______________________________________________ lisp mailing list >> [email protected] https://www.ietf.org/mailman/listinfo/lisp >> _______________________________________________ lisp mailing list [email protected] https://www.ietf.org/mailman/listinfo/lisp
