Re: Gen-ART LC review of draft-ietf-isis-node-admin-tag-08
Pushpasis Sarkar <pushpasis.ietf@gmail.com> Tue, 03 May 2016 05:07 UTC
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Subject: Re: Gen-ART LC review of draft-ietf-isis-node-admin-tag-08
To: Peter Yee <peter@akayla.com>, draft-ietf-isis-node-admin-tag.all@ietf.org
References: <00ef01d1a2bc$1e6a0130$5b3e0390$@akayla.com> <57278FB0.9090901@gmail.com> <019901d1a4f5$78f91e70$6aeb5b50$@akayla.com>
From: Pushpasis Sarkar <pushpasis.ietf@gmail.com>
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Date: Tue, 03 May 2016 10:37:14 +0530
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Hi Peter, Please find comments inline.. Thanks and Regards, -Pushpasis On Tuesday 03 May 2016 10:07 AM, Peter Yee wrote: > Pushpasis, > > See my replies below prefaced with PEY>. > > Thanks. > -Peter > > -----Original Message----- > From: Pushpasis Sarkar [mailto:pushpasis.ietf@gmail.com] > Sent: Monday, May 02, 2016 10:35 AM > To: Peter Yee; draft-ietf-isis-node-admin-tag.all@ietf.org > Cc: gen-art@ietf.org; ietf@ietf.org > Subject: Re: Gen-ART LC review of draft-ietf-isis-node-admin-tag-08 > > Hi Peter, > > Once again many many thanks for the detailed review comments. Please find > few comments inline. Unless otherwise there is a counter-comment the comment > is accepted and will be addressed in the next version to be uploaded soon. > > Thanks and Regards, > -Pushpasis > > On 4/30/16 2:11 PM, Peter Yee wrote: >> I am the assigned Gen-ART reviewer for this draft. The General Area >> Review Team (Gen-ART) reviews all IETF documents being processed by >> the IESG for the IETF Chair. Please treat these comments just like >> any other last call comment. For background on Gen-ART, please see >> the FAQ at <http://wiki.tools.ietf.org/area/gen/trac/wiki/GenArtfaq> >> >> Document: draft-ietf-isis-node-admin-tag-08 >> Reviewer: Peter Yee >> Review Date: April 27, 2016 >> IETF LC End Date: April 29, 2016 >> IESG Telechat date: May 5, 2016 >> >> Summary: This draft is basically ready for publication as a Standards >> Track RFC, but has some issues that should be fixed/considered before > publication. >> [Ready with issues] >> >> This draft defines a means to carry additional per-node administrative >> tags with the IS-IS protocol. These tags can be used along with local >> policy to simplify the management of routing and path selection. This >> specification gives informative examples of such tag usage but does >> not otherwise prescribe the meaning of the tags. >> >> This review was generated prior to the release of draft -09 (but not >> keyed in until April 29th), but many of the issues and nits noted >> below remain in draft -09. Obviously, some of my comments no longer >> apply. I'll address draft -09 specifically for the telechat review, >> but you should look at the points here prior to that review to save >> time. Given that draft -09 substantially reduces Section 5, I've >> removed my comments regarding that section as well as in a few other > places. >> Major issues: None >> >> Minor issues: >> >> Page 4, last partial paragraph: the number 63 is given for the maximum >> number of per-node administrative tags that can be carried in a sub-TLV. >> Given the maximum length of a sub-TLV is 250 octets (and 2 octets are >> otherwise used by type and length), I would argue that the correct >> number here is 62 (62*4 = 248). Also, I would delete the text starting at > "and". >> In all cases, when more than 62 tags are used, a single sub-TLV will >> not provide sufficient space. > [Pushpasis] AFAIK, maximum length of sub-TLV is 255 (because length field if > 1 byte). If you take out 2 bytes for length and value, we have > 253 bytes left.. 253 divided by 4byte = 63 (63x4=252).. Let me know if my > understanding is wrong. > > PEY>RFC 4971 (Section 2) gives this text: "Set of optional sub-TLVs (0-250 > octets)". My interpretation was that the Router CAPABILITY TLV can have a > length of 5-255 octets, of which 4 are the router ID and 1 is the flags, > leaving up to 250 octets for the sub-TLVs. [PS2] You are totally right.. I overlooked the structure of the Rtr Cap Tlv itself. I will make the changes. >> Page 5, 1st partial paragraph, 1st full sentence: Sub-TLV values are >> given here as cumulative. Is there any need or desire to be able to >> subtract tags? How would a router disassociate itself from a tag that >> was no longer relevant to the router? This ability is implied in >> Section 4.3, 2nd paragraph, but that conflicts with the statement >> given here. In general, I believe the ability to reset the flooded >> tags associated with a router or to delete a tag is underspecified. > [Pushpasis] Assuming the comment is on the following sentence.. > "Such occurrence of the 'Node > Administrative Tag' sub-TLV does not cancel previous announcements, > but rather is cumulative." > > The reference here to "previous announcements" is not the ones received in > the previous instances of the same LSP fragment but to the ones received in > other TLVs in same or different LSP fragments originated by the same > router... What it essentially mean is that if a router originates 3 > node-admin-tag TLVs in three different LSP fragments.. the later ones do not > cancel/override the previous ones but are rather considered all together.. > in an additive manner.. Perhaps I will add a line or two clarify the same.. > I also see RFC7777 has altogether removed the stanza in the final RFC > edition.. Will that be fine too with you for this draft? > > PEY> Alignment with RFC 7777 makes sense, given that the general concept is > to do the same thing for each of the routing protocols. > > Alternatively, I can propose the following clarifying text... If it makes > any sense to you :) > > "Such occurrence of a > 'Node Administrative Tag' sub-TLV, found in a LSP fragment received > recently, does not cancel > the one(s) received in any recent versions of other LSP fragments > originated by the same > router. Instead, all the 'Node Administrative Tag' sub-TLVs found in > all the LSP fragments > originated by the same originating router, should be treated as > cumulative." > > PEY> That's less satisfying because it requires some definition of recent. > It also doesn't seem to solve my cumulative issue in that if an originating > router sends some number of Node Administrative Tag sub-TLVs, the receiving > router doesn't seem to have a way of knowing when to flush or reset them > unless the definition of recent implies this or something in IS-IS makes it > obvious when the old tags are no longer relevant and new tags should not be > accumulated with the old ones. > >> Page 6, 1st partial paragraph, 1st sentence: Care to define >> "reasonably small"? Previously, the ability to send more than 63 (or >> perhaps 62, see >> above) tags was specified in section 3.1. What's the limit to >> reasonableness? (Not that an exact number seems to matter at all for >> the purposes of this specification, which is agnostic to the specific >> number or the use of the tags.) > [Pushpasis] I see the only way to resolve this comment is by removing the > stanza being referred to in the last comment.. > > PEY> Yeah, that's the problem with words that require interpretation. :-) [PS2] Will remove it then.. > >> Page 6, Section 4.3, 2nd paragraph: This paragraph implies that a >> large set (greater than 62 at least) of sub-TLVs will have to be sent >> in multiple Router CAPABILITY TLVs and those TLVs must(?) occur in a >> single Link-State PDU. Or how is the receiving router to know that it >> has the complete set of tags? Also, the implication seems to be that >> while section 3.1 indicates a strictly cumulative capability, there >> must be someway of terminating those cumulative changes and allowing a > reset. What is that signaling mechanism? > [Pushpasis] This is dealt with ISIS LSP fragment generation and reception.. > A typical ISIS implementation will be able to figure out any given point > whether it has received all the fragments originated by a originating router > or not. Please refer to ISO-10589 for more details.. > There are no extra requirements imposed by this draft in this regard. > > PEY> So Section 3.1 indicates accumulation of tags until the IS-IS > implementation determines that it has received all fragments. That's fine. > Then I would indicate in Section 3.1, if you elect to keep that text, that > completion of fragment reception terminates the cumulative action and new > fragments will restart the accumulation. Or just align with RFC 7777, drop > the cumulative statement, and my comment will seem moot and tiresome. ;-) [PS2] I see now why RFC7777 chose to drop the text :)
- Gen-ART LC review of draft-ietf-isis-node-admin-t… Peter Yee
- Re: Gen-ART LC review of draft-ietf-isis-node-adm… Pushpasis Sarkar
- Re: Gen-ART LC review of draft-ietf-isis-node-adm… Pushpasis Sarkar
- RE: Gen-ART LC review of draft-ietf-isis-node-adm… Peter Yee
- Re: Gen-ART LC review of draft-ietf-isis-node-adm… Pushpasis Sarkar