On 2/14/18 3:45 PM, Or Gerlitz wrote: > On Tue, Feb 13, 2018 at 5:21 PM, David Ahern <dsah...@gmail.com> wrote: >> On 2/13/18 5:42 AM, Ido Schimmel wrote: >>> On Tue, Feb 13, 2018 at 01:03:14PM +0200, Or Gerlitz wrote: >>>> On Tue, Feb 13, 2018 at 2:05 AM, David Ahern <dsah...@gmail.com> wrote: >>>>> Hardware supports multipath selection using the standard L4 5-tuple >>>>> instead of just L3 and the flow label. In addition, some network >>>>> operators prefer IPv6 path selection to use the 5-tuple. >>>> >>>> The HW supports using flow label and AFAIK that is the preferred approach >>>> by the community (?) >>>> >>>>> To that end, add support to IPv6 for multipath hash policy >>>> >>>> so a question comes up if/what are the disadvantaged >>>> to support 5-tuple. E.g Tom was commenting that such DPI is problematic >>>> when multiple IPv6 header extensions are used. >> >> Pros and cons to both approaches (L3 only or L4). We (Cumulus Networks) >> use L4 5-tuple hash for both IPv4 and IPv6. When I asked around various >> experts all of them gave me a puzzled look as to why I was asking the >> question. Basically, the unanimous response was of course it is an L4 hash. > > how the various systems you are dealing with do with traffic that involves > ipv6 extension headers? what about environments with GRE? in ipv4 GRE > fabrics are just broken for ECMP, in ipv6 they can fly with flow label but > will crash again with L4 hash. >
If you like your ecmp hash algorithm, you can keep your ecmp hash algorithm. This gives users a choice; it is not a requirement to move from L3 only to L4. Further, this makes IPv6 on par with IPv4 with a choice between L3 and L4 and allows users to decide what works best for them.