Re: [Last-Call] [v6ops] Tsvart last call review of draft-ietf-v6ops-ipv6-ehs-packet-drops-05
Brian E Carpenter <brian.e.carpenter@gmail.com> Wed, 07 April 2021 22:34 UTC
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To: Tom Herbert <tom@herbertland.com>, "Rob Wilton (rwilton)" <rwilton@cisco.com>
Cc: Gorry Fairhurst <gorry@erg.abdn.ac.uk>, IPv6 Operations <v6ops@ietf.org>, "draft-ietf-v6ops-ipv6-ehs-packet-drops.all@ietf.org" <draft-ietf-v6ops-ipv6-ehs-packet-drops.all@ietf.org>, "last-call@ietf.org" <last-call@ietf.org>, "tsv-art@ietf.org" <tsv-art@ietf.org>, Fernando Gont <fgont@si6networks.com>
References: <161366727749.10107.14514005068158901089@ietfa.amsl.com> <e41f3484-f816-e185-2d99-94323c8da732@si6networks.com> <CALx6S34qSxGijVcs229bAL5gMhMvMNYUXm3yEmrg6wxUiUAiaA@mail.gmail.com> <bf83d228-25bc-21bb-f984-d58ead6bf492@si6networks.com> <CALx6S35Kh-QAXJDAucuw5Wty37MBiwS=pqQknMZ+15b7D5Sn8A@mail.gmail.com> <34e78618-cb28-71a1-a9d3-7aec38032659@si6networks.com> <CAO42Z2zqD9_d2Fbr25Y2CV1GdzYKd167yf5DHeHna7V66pF65A@mail.gmail.com> <0bd316ac-1789-f4c6-d280-943ad6e60309@si6networks.com> <CALx6S34dMEEJ+OPUu_=FW1Y5AQuvAaHzBPEe448S7rfbMmHN_w@mail.gmail.com> <CEFDF511-9255-4913-840D-50CCBC2B7B17@gmail.com> <CALx6S36_w+zxyUt0DzQ9NKBs+SAPZDNhs_sqLBwi+qneOPSS5A@mail.gmail.com> <ef2bd4f5-3b1e-b88c-ec8f-dd9a2f9a60ba@si6networks.com> <CALx6S349X7fQR=9Dj+n5X7ovXsSjLYibv-C-+bL0nkWsYP5NGA@mail.gmail.com> <MN2PR11MB43668EDA6209CA6AF3BCC5EEB5759@MN2PR11MB4366.namprd11.prod.outlook.com> <CALx6S3447SJwdRPoG_BaXS=ihBe1xA84vxcCev1y2K4xqMYZaQ@mail.gmail.com>
From: Brian E Carpenter <brian.e.carpenter@gmail.com>
Organization: University of Auckland
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Date: Thu, 08 Apr 2021 10:34:38 +1200
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Subject: Re: [Last-Call] [v6ops] Tsvart last call review of draft-ietf-v6ops-ipv6-ehs-packet-drops-05
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On 08-Apr-21 03:20, Tom Herbert wrote: ... > So my fundamental concern with this draft is that it is an entirely > qualitative description of a well known problem, however a qualitative > analysis is insufficient input for moving extension headers forward. > In the draft, there are several reasons suggested as to why routers > might drop packets, however there is no indication of the relative > occurrence frequency of these. That seems to call for a fairly major measurement project by an organisation like CAIDA or RIPE Labs, with collaborative ISPs. While that is a perfectly good idea, it would presumably take a couple of years to get data. I personally don't see it as a valid reason to hold up this draft. Maybe the authors should add a note about the need for data. > Also, there are parameterizations > mentioned such as in the state that routers might drop if the chain is > "too long", there is no analysis on exactly what "too long" commonly > is (a couple of sizes for parsing buffers are mentioned but without > reference which is another frustration of mine with this draft). A > quantified analysis of the problem would delve into implementations > and deployment thereby providing actionable data. Note this is not the > same as making recommendations, I am just asking for the operational > data as part of the analysis from which we could derive guidance or > new protocol requirements. Again, I don't see how that can be done without a major and organised effort. The issue of buffer sizes may also involve proprietary information, which is another difficulty. Again, it is neither quick nor easy to get data. Regards Brian > Tom > > > Tom > >> >> Regards, >> Rob >> >> >>> -----Original Message----- >>> From: v6ops <v6ops-bounces@ietf.org> On Behalf Of Tom Herbert >>> Sent: 10 March 2021 02:03 >>> To: Fernando Gont <fgont@si6networks.com> >>> Cc: Gorry Fairhurst <gorry@erg.abdn.ac.uk>; IPv6 Operations >>> <v6ops@ietf.org>; draft-ietf-v6ops-ipv6-ehs-packet-drops.all@ietf.org; >>> last-call@ietf.org; tsv-art@ietf.org >>> Subject: Re: [v6ops] [Last-Call] Tsvart last call review of draft-ietf- >>> v6ops-ipv6-ehs-packet-drops-05 >>> >>> On Tue, Mar 9, 2021 at 4:03 PM Fernando Gont <fgont@si6networks.com> >>> wrote: >>>> >>>> On 9/3/21 19:07, Tom Herbert wrote: >>>> [...] >>>>> >>>>> Yes, ACLs on transport layer ports are common requirements, however >>>>> the problem arises from related requirements that arise due to the >>>>> limitations of routers to be able to locate the transport layer >>>>> information in a packet. An example of such an implied requirement >>>>> from this draft is "don't send packets with IPv6 header chains that >>>>> are too long because some routers can't parse deep enough into packets >>>>> to find the transport layer ports due to implementation constraints >>>>> (like limited size parsing buffer)". >>>> >>>> You seem to be reading more from the document than what we actually said >>>> in the document. >>>> >>>> There are no requirements in this document. We simply explain things >>>> operators need to do, what are the associated limitations in real-world >>>> devices, and what's the likely outcome. >>>> >>>> That's not an implied requirement, but simply a description of facts. >>>> >>> It's obvious that the implied or at least inferred requirement is that >>> if a host wants to increase the probability of packets making it to >>> the destination then they should not make header chains too long. This >>> would also be an obvious interoperability requirement, i.e. if I make >>> my header chains too long then packets will be dropped and my host >>> stack is not interoperable with some elements in the network. >>> >>>> >>>> >>>>> While the rationale for the >>>>> requirement may make sense, the problem, at least from the host stack >>>>> perspective of trying to send packets with low probability they'll be >>>>> dropped, is that a requirement that "don't IPv6 header chains that are >>>>> too long" is is useless without any quantification as exactly to what >>>>> "too long" might be. >>>> >>>> "too long" for the processing device(s). You don't know what devices >>>> will process your packets, hence cannot even guess what "too long" might >>>> mean. >>>> >>>> What you know for sure is that the longer the chain, the lower the >>>> chances of your packets surviving -- as per RFC7872. >>>> >>> That seems to me more like an assumption than a proven fact. To prove >>> it we'd need the data that correlates the length of the chain with >>> probability of drop, or alternatively, one could survey common router >>> implementations' capabilities and similarly extrapolate the >>> correlation. If we had this data then we could derive a meaningful >>> quantified requirement for both what routers are expected to process >>> and what hosts can expect. RFC7872 doesn't really have sufficient data >>> to make this correlation, and besides that it is not current. >>> >>> In any case, this draft qualitatively describes why routers are >>> droppings. Which I suppose is good, but, given that information, I >>> don't see much that helps host developers that are sending packets in >>> the network and are trying to go beyond sending packets that conform >>> to the least common denominator of plain TCP/IP. >>> >>> Tom >>> >>>> Thanks, >>>> -- >>>> Fernando Gont >>>> SI6 Networks >>>> e-mail: fgont@si6networks.com >>>> PGP Fingerprint: 6666 31C6 D484 63B2 8FB1 E3C4 AE25 0D55 1D4E 7492 >>>> >>>> >>>> >>>> >>> >>> _______________________________________________ >>> v6ops mailing list >>> v6ops@ietf.org >>> https://www.ietf.org/mailman/listinfo/v6ops > > _______________________________________________ > v6ops mailing list > v6ops@ietf.org > https://www.ietf.org/mailman/listinfo/v6ops >
- [Last-Call] Tsvart last call review of draft-ietf… Gorry Fairhurst via Datatracker
- Re: [Last-Call] Tsvart last call review of draft-… Fernando Gont
- Re: [Last-Call] Tsvart last call review of draft-… Brian E Carpenter
- Re: [Last-Call] Tsvart last call review of draft-… Fernando Gont
- Re: [Last-Call] [Tsv-art] Tsvart last call review… Gorry Fairhurst
- Re: [Last-Call] Tsvart last call review of draft-… Brian E Carpenter
- Re: [Last-Call] [v6ops] Tsvart last call review o… Tom Herbert
- Re: [Last-Call] Tsvart last call review of draft-… Fernando Gont
- Re: [Last-Call] [v6ops] Tsvart last call review o… Fernando Gont
- Re: [Last-Call] [Tsv-art] Tsvart last call review… Fernando Gont
- Re: [Last-Call] Tsvart last call review of draft-… Nick Hilliard
- Re: [Last-Call] Tsvart last call review of draft-… Gorry Fairhurst
- Re: [Last-Call] [v6ops] Tsvart last call review o… Tom Herbert
- Re: [Last-Call] [v6ops] Tsvart last call review o… Nick Hilliard
- Re: [Last-Call] Tsvart last call review of draft-… Nick Hilliard
- Re: [Last-Call] [v6ops] Tsvart last call review o… Tom Herbert
- Re: [Last-Call] [v6ops] Tsvart last call review o… Nick Hilliard
- Re: [Last-Call] [v6ops] Tsvart last call review o… Fernando Gont
- Re: [Last-Call] [v6ops] Tsvart last call review o… Tom Herbert
- Re: [Last-Call] [v6ops] Tsvart last call review o… Nick Hilliard
- Re: [Last-Call] [v6ops] Tsvart last call review o… Tom Herbert
- Re: [Last-Call] [v6ops] Tsvart last call review o… Fernando Gont
- Re: [Last-Call] [v6ops] Tsvart last call review o… Fernando Gont
- Re: [Last-Call] [v6ops] Tsvart last call review o… Nick Hilliard
- Re: [Last-Call] [v6ops] Tsvart last call review o… Tom Herbert
- Re: [Last-Call] [v6ops] Tsvart last call review o… Fred Baker
- Re: [Last-Call] [v6ops] Tsvart last call review o… Nick Hilliard
- Re: [Last-Call] [v6ops] Tsvart last call review o… Tom Herbert
- Re: [Last-Call] [v6ops] Tsvart last call review o… Fernando Gont
- Re: [Last-Call] [v6ops] Tsvart last call review o… Mark Smith
- Re: [Last-Call] [v6ops] Tsvart last call review o… Joseph Touch
- Re: [Last-Call] [v6ops] Tsvart last call review o… Fernando Gont
- Re: [Last-Call] [v6ops] Tsvart last call review o… Tom Herbert
- Re: [Last-Call] [v6ops] Tsvart last call review o… Fernando Gont
- Re: [Last-Call] [v6ops] Tsvart last call review o… Joseph Touch
- Re: [Last-Call] [v6ops] Tsvart last call review o… Mark Smith
- Re: [Last-Call] [v6ops] Tsvart last call review o… Fred Baker
- Re: [Last-Call] [v6ops] Tsvart last call review o… Tom Herbert
- Re: [Last-Call] [v6ops] Tsvart last call review o… Fernando Gont
- Re: [Last-Call] [v6ops] Tsvart last call review o… Tom Herbert
- Re: [Last-Call] [v6ops] Tsvart last call review o… Rob Wilton (rwilton)
- Re: [Last-Call] [v6ops] Tsvart last call review o… Nick Hilliard
- Re: [Last-Call] [v6ops] Tsvart last call review o… Tom Herbert
- Re: [Last-Call] [v6ops] Tsvart last call review o… Brian E Carpenter
- Re: [Last-Call] [v6ops] Tsvart last call review o… Fernando Gont
- Re: [Last-Call] [v6ops] Tsvart last call review o… Fernando Gont
- Re: [Last-Call] [v6ops] Tsvart last call review o… Tom Herbert
- Re: [Last-Call] [v6ops] Tsvart last call review o… Tom Herbert
- Re: [Last-Call] [v6ops] Tsvart last call review o… Fernando Gont
- Re: [Last-Call] [v6ops] Tsvart last call review o… Tom Herbert
- Re: [Last-Call] [v6ops] Tsvart last call review o… Tom Herbert
- Re: [Last-Call] [v6ops] Tsvart last call review o… Fernando Gont
- Re: [Last-Call] [v6ops] Tsvart last call review o… Rob Wilton (rwilton)
- Re: [Last-Call] [v6ops] Tsvart last call review o… Tom Herbert
- Re: [Last-Call] [v6ops] Tsvart last call review o… Timothy J. Salo
- Re: [Last-Call] [v6ops] Tsvart last call review o… Tom Herbert
- Re: [Last-Call] [v6ops] Tsvart last call review o… Brian E Carpenter
- Re: [Last-Call] [v6ops] Tsvart last call review o… Fernando Gont