Re: [Int-area] Comments on draft-ietf-intarea-frag-fragile-06
Fred Baker <fredbaker.ietf@gmail.com> Tue, 29 January 2019 23:37 UTC
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From: Fred Baker <fredbaker.ietf@gmail.com>
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Date: Tue, 29 Jan 2019 15:37:46 -0800
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Cc: int-area <int-area@ietf.org>
To: Tom Herbert <tom@herbertland.com>
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Subject: Re: [Int-area] Comments on draft-ietf-intarea-frag-fragile-06
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> On Jan 29, 2019, at 11:45 AM, Tom Herbert <tom@herbertland.com> wrote: > > Hello, > > I have suggested text for the draft to address some previous comments > made on the list. > > Last paragraph in section 4.3: > > "This problem does not occur in stateful firewalls or Network Address > Translation (NAT) devices. Such devices maintain state so that they > can afford identical treatment to each fragment that belongs to a > packet. Do we have a list of such products? I'm unaware of one. Making a blanket statement such as this troubles me, because it seems to say that this is invariably true, and I don't know that it is or isn't. > Note, however, that stateful firewalls and NAT devices impose > the external requirement that all packets of a flow and fragments of a > packets for a flow must traverse the same stateful device; stateless > devices do not force this requirement." Here's an example of why blanket statements need to be qualified. If you take NPTv6 to be a form of NAT, it doesn't force route symmetry. > Section 4.5: > "IP fragmentation causes problems for some routers that support Equal > Cost Multipath (ECMP). Many routers that support ECMP execute the > algorithm described in Section 4.4 in order to perform flow based > forwarding; As far as I know, routers that hash fields in the IP header to select a en ECMP next hop do so because all packets in a flow will hash the same way (modulo the issues with the transport port number), not because they are doing per-flow forwarding. The do so explicitly to avoid having to maintain per-flow state and yet make all fragments of a message follow the same path. > therefore, the exhibit they same problematic behaviors > described in Section 4.4. In IPv6, the flow label may alternatively > used as input to the algorithm as opposed to parsing the transport > layer of packets to discern port numbers. The flow label should be > consistently set for a packets of flow including fragments, such that > a device does not need to parse packets beyond the IP header for the > purposes of ECMP." > > Add to section 7.3: > > "Routers SHOULD use IPv6 flow label for ECMP routing as described in [RFC6438]." > > _______________________________________________ > Int-area mailing list > Int-area@ietf.org > https://www.ietf.org/mailman/listinfo/int-area -------------------------------------------------------------------------------- Victorious warriors win first and then go to war, Defeated warriors go to war first and then seek to win. Sun Tzu
- [Int-area] Comments on draft-ietf-intarea-frag-fr… Tom Herbert
- Re: [Int-area] Comments on draft-ietf-intarea-fra… Tom Herbert
- Re: [Int-area] Comments on draft-ietf-intarea-fra… Fred Baker
- Re: [Int-area] Comments on draft-ietf-intarea-fra… Stewart Bryant
- Re: [Int-area] Comments on draft-ietf-intarea-fra… Stewart Bryant
- Re: [Int-area] Comments on draft-ietf-intarea-fra… Tom Herbert
- Re: [Int-area] Comments on draft-ietf-intarea-fra… Templin (US), Fred L
- Re: [Int-area] Comments on draft-ietf-intarea-fra… Stewart Bryant
- Re: [Int-area] Comments on draft-ietf-intarea-fra… Templin (US), Fred L
- Re: [Int-area] Comments on draft-ietf-intarea-fra… Stewart Bryant
- Re: [Int-area] Comments on draft-ietf-intarea-fra… Templin (US), Fred L
- Re: [Int-area] Comments on draft-ietf-intarea-fra… Stewart Bryant
- Re: [Int-area] Comments on draft-ietf-intarea-fra… Templin (US), Fred L
- Re: [Int-area] Comments on draft-ietf-intarea-fra… Brian E Carpenter
- Re: [Int-area] Comments on draft-ietf-intarea-fra… Stewart Bryant
- Re: [Int-area] Comments on draft-ietf-intarea-fra… Templin (US), Fred L