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.

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