What if? [was Re: Extension Header Insertion]
Brian E Carpenter <brian.e.carpenter@gmail.com> Tue, 10 December 2019 01:21 UTC
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Subject: What if? [was Re: Extension Header Insertion]
To: adrian@olddog.co.uk, 'Ron Bonica' <rbonica=40juniper.net@dmarc.ietf.org>, '6man' <6man@ietf.org>
References: <BN7PR05MB5699D9BA988F96E2F41CD390AE580@BN7PR05MB5699.namprd05.prod.outlook.com> <00dc01d5ae73$c361b450$4a251cf0$@olddog.co.uk> <dbcdeb1a-0091-da2b-20df-d991e6c06091@gmail.com>
From: Brian E Carpenter <brian.e.carpenter@gmail.com>
Organization: University of Auckland
Message-ID: <9bc47200-4fea-37ce-0ede-cbf6a5f70ea9@gmail.com>
Date: Tue, 10 Dec 2019 14:21:06 +1300
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So, let's assume that two consecutive SRH headers are allowed in the same packet. So the first one (an example from draft-ietf-6man-segment-routing-header-26) is: Segments Left=2 Last Entry=2 Flags=0 Tag=0 Segment List[0]=S3 Segment List[1]=S2 Segment List[2]=S1 and the second one is Segments Left=1 Last Entry=1 Flags=0 Tag=0 Segment List[0]=S4 Segment List[1]=S5 I made that up and it's obviously nonsense, but if this is allowed why aren't the rules for processing conflicting SRHs described in draft-ietf-6man-segment-routing-header-26? Do we need to recall it from the RFC Editor queue to be fixed? Regards Brian Carpenter On 10-Dec-19 14:02, Brian E Carpenter wrote: > On 09-Dec-19 22:33, Adrian Farrel wrote: >> Hi Ron, >> >> I think we can jump to a quick answer on this because draft-ietf-spring-srv6-network-programming-05 says: >> >> We assume that the SRH may >> be present multiple times inside each packet. >> >> Thus we may assume that the proponents of Extension Header insertion do think that it is acceptable to insert a second routing header into a packet that already has one. >> >> And 8200 is clear when it says: >> Each extension header should occur at most once, except for the >> Destination Options header, which should occur at most twice (once >> before a Routing header and once before the upper-layer header). > > That's "should", which in a non-RFC2119 document like RFC 8200, means "should". > It's not "must". So while I would prefer that the relevant SRH document justifies > the exception, there isn't a breach of a mandatory requirement. > >> So draft-ietf-spring-srv6-network-programming-05 includes a false assumption which need to be either removed or secured through an update to 8200. >> >> Ideally, I suppose, draft-ietf-6man-segment-routing-header would have contained the clarification that the SRH could be present multiple times > > Yes > >> (updating 8200 as it went). > > Unnecessary, IMHO. > > Brian > >> >> >> >> Cheers, >> >> Adrian >> >> >> >> *From:*ipv6 <ipv6-bounces@ietf.org> *On Behalf Of *Ron Bonica >> *Sent:* 09 December 2019 03:04 >> *To:* 6man <6man@ietf.org> >> *Subject:* Extension Header Insertion >> >> >> >> Folks, >> >> >> >> This question is posed primarily to the proponents of Extension Header insertion. >> >> >> >> Do you think that it is acceptable to insert a second routing header into a packet that already has one, so the resulting packet looks like the following: >> >> >> >> * IPv6 header >> * SRH >> * SRH >> * Upper-layer header >> >> >> >> Would this be common in TI-LFA? >> >> >> >> Ron >> >> >> >> >> >> Juniper Business Use Only >> >> >> -------------------------------------------------------------------- >> IETF IPv6 working group mailing list >> ipv6@ietf.org >> Administrative Requests: https://www.ietf.org/mailman/listinfo/ipv6 >> -------------------------------------------------------------------- >> >
- Extension Header Insertion Ron Bonica
- RE: Extension Header Insertion Adrian Farrel
- Re: Extension Header Insertion Darren Dukes (ddukes)
- Re: Extension Header Insertion Darren Dukes (ddukes)
- Re: Extension Header Insertion Tom Herbert
- RE: Extension Header Insertion Adrian Farrel
- Re: Extension Header Insertion Gyan Mishra
- RE: Extension Header Insertion Ron Bonica
- Re: Extension Header Insertion Brian E Carpenter
- What if? [was Re: Extension Header Insertion] Brian E Carpenter
- Re: What if? [was Re: Extension Header Insertion] Gyan Mishra
- Re: What if? [was Re: Extension Header Insertion] Gyan Mishra
- Re: What if? [was Re: Extension Header Insertion] Fernando Gont
- Re: What if? [was Re: Extension Header Insertion] Fernando Gont
- Re: What if? [was Re: Extension Header Insertion] Fernando Gont
- Re: Extension Header Insertion Stewart Bryant
- Re: What if? [was Re: Extension Header Insertion] Brian E Carpenter
- Re: What if? [was Re: Extension Header Insertion] Gyan Mishra
- RE: Extension Header Insertion Ron Bonica
- RE: What if? [was Re: Extension Header Insertion] Ron Bonica
- Re: What if? [was Re: Extension Header Insertion] Darren Dukes (ddukes)
- Re: What if? [was Re: Extension Header Insertion] Fernando Gont
- Re: What if? [was Re: Extension Header Insertion] Fernando Gont
- Re: Extension Header Insertion Fernando Gont
- Re: What if? [was Re: Extension Header Insertion] Brian E Carpenter
- Re: What if? [was Re: Extension Header Insertion] Warren Kumari
- Re: What if? [was Re: Extension Header Insertion] Fernando Gont
- Re: What if? [was Re: Extension Header Insertion] Fernando Gont
- Re: What if? [was Re: Extension Header Insertion] Gyan Mishra
- Re: What if? [was Re: Extension Header Insertion] Stewart Bryant
- Re: What if? [was Re: Extension Header Insertion] Jeff Tantsura
- Re: What if? [was Re: Extension Header Insertion] Brian E Carpenter
- Re: What if? [was Re: Extension Header Insertion] Gyan Mishra
- Re: What if? [was Re: Extension Header Insertion] Gyan Mishra
- Re: What if? [was Re: Extension Header Insertion] Jeff Tantsura
- Re: What if? [was Re: Extension Header Insertion] Gyan Mishra
- Re: What if? [was Re: Extension Header Insertion] Stewart Bryant