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. 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
