Hi Tom, > -----Original Message----- > From: Tom Herbert [mailto:[email protected]] > Sent: Tuesday, May 23, 2017 1:25 PM > To: Templin, Fred L <[email protected]> > Cc: Joe Touch <[email protected]>; [email protected] > Subject: Re: [Int-area] IPv6 fragmentation for IPv4 > > On Tue, May 23, 2017 at 1:13 PM, Templin, Fred L > <[email protected]> wrote: > > Joe, > > > >> -----Original Message----- > >> From: Int-area [mailto:[email protected]] On Behalf Of Templin, > >> Fred L > >> Sent: Tuesday, May 23, 2017 11:49 AM > >> To: Joe Touch <[email protected]>; [email protected] > >> Subject: Re: [Int-area] IPv6 fragmentation for IPv4 > >> > >> Hi Joe, > >> > >> > -----Original Message----- > >> > From: Joe Touch [mailto:[email protected]] > >> > Sent: Tuesday, May 23, 2017 11:01 AM > >> > To: Templin, Fred L <[email protected]>; [email protected] > >> > Subject: Re: IPv6 fragmentation for IPv4 > >> > > >> > Hi, Fred (et al.), > >> > > >> > On 5/23/2017 9:17 AM, Templin, Fred L wrote: > >> > > Joe, I wanted to run an idea by you. We all know that IPv4 > >> > > fragmentation has > >> > > problems because of the 16-bit ID field. So, why not insert an IPv6 > >> > > Fragment > >> > > Header between the IPv4 header and the upper layer protocol data, then > >> > > use IPv6-style fragmentation instead of IPv4 fragmentation? > >> > > >> > IPv4 fragmentation has several impediments: > >> > - small ID field > >> > - lack of a reassembly checksum > >> > - lack of a fixed-location flow ID > >> > > >> > Using IPv6-Frag as the next header solves only the first of these. The > >> > last is significant - putting a new header would defeat IPv4 flow ECMP > >> > even for the first fragment. > >> > >> ECMP gateways could be updated to look at the ULP headers > >> following the IPv6 Frag header in the first fragment. > >> > >> > IPv6 includes a flow field that serves this > >> > purpose. > >> > >> How does it work for plain-old IPv4 fragmentation? I would think > >> that ECMP gateways would look at the IP ID and try to associate > >> the fragments so they all get equal ECMP treatment, i.e., the > >> same as for vanilla IPv4. > > > > Here's another think - since the IPv6 Frag Header already has a > > 32-bit IP ID that we are using for fragmentation, and since we > > are asking the IPv4 header to set DF=1, the 16-bit IP ID field in > > the IPv4 header is available for use as a flow field - right? > > > Fred, > > I think this would over kill. Assuming fragmentation remains the rare > case, getting the ECMP hash over the addresses should be sufficient. > ECMP is a performance optimization, once you're fragmenting that's > already giving up a lot.
Yes, I don't disagree. But writing a hash of the 5-tuple in the IPv4 ID field of each fragment (and setting DF=1) shouldn't be so hard. Thanks - Fred > Tom > > > Thanks - Fred > > > >> Thanks - Fred > >> [email protected] > >> > >> > Joe > >> > >> _______________________________________________ > >> Int-area mailing list > >> [email protected] > >> https://www.ietf.org/mailman/listinfo/int-area > > > > > > _______________________________________________ > > Int-area mailing list > > [email protected] > > https://www.ietf.org/mailman/listinfo/int-area _______________________________________________ Int-area mailing list [email protected] https://www.ietf.org/mailman/listinfo/int-area
