Re: [lisp] looking for clarifications on rfc 6830
Joel Halpern Direct <jmh.direct@joelhalpern.com> Wed, 21 October 2015 22:40 UTC
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To: Richard Li <renwei.li@huawei.com>, LISP mailing list list <lisp@ietf.org>
References: <F061CEB6876F904F8EA6D6B92877731C3900A80A@SJCEML701-CHM.china.huawei.com> <56253E35.6070309@joelhalpern.com> <F061CEB6876F904F8EA6D6B92877731C390122CA@SJCEML701-CHM.china.huawei.com>
From: Joel Halpern Direct <jmh.direct@joelhalpern.com>
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Date: Wed, 21 Oct 2015 18:40:51 -0400
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Subject: Re: [lisp] looking for clarifications on rfc 6830
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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:jmh@joelhalpern.com] 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 >> lisp@ietf.org https://www.ietf.org/mailman/listinfo/lisp >>
- [lisp] looking for clarifications on rfc 6830 Richard Li
- Re: [lisp] looking for clarifications on rfc 6830 Joel M. Halpern
- Re: [lisp] looking for clarifications on rfc 6830 Dino Farinacci
- Re: [lisp] looking for clarifications on rfc 6830 Richard Li
- Re: [lisp] looking for clarifications on rfc 6830 Dino Farinacci
- Re: [lisp] looking for clarifications on rfc 6830 Joel Halpern Direct
- Re: [lisp] looking for clarifications on rfc 6830 Richard Li