Re: IPv6 Anycast has been killed by LINUX patch in 2016 - who cares?

[Toerless Eckert <[e-mail]>]

Sure, that is the basic recommendation,
but let me play devils advocate (linux developer):

rfc6437: "However, a flow is not necessarily 1:1 mapped to a transport connection"

Aka: what linux does is a perfect lightweight form of
MP_TCP just without the overhead of different IP addresses
or port numbers to identify different flows. Just different
IPv6 flow labels. And in MP-TCP it would of course be perfectly
legitimate to use two flows sequentially, e.g.: when one flow
has RTO issues, using the second flow. Thats just a transport
protocol policy choice.

In other words: linux does not violate this SHOULD because it really
uses two different flows.

Cheers
    Toerless

On Sat, Aug 07, 2021 at 06:37:52PM +0300, Töma Gavrichenkov wrote:
> Peace,
> 
> On Sat, Aug 7, 2021, 6:19 PM Toerless Eckert <[e-mail]> wrote:
> 
> > Do our RFCs say or imply anything about whether or not hosts can change
> > the IPv6 flow label field of a single flow during the lifetime
> > of a flow (MUST, SHOULD, MAY, ... MAY NOT, SHOULD NOT, MUST NOT)
> >
> 
> Well, it is, of course, sort of implied that the flow label is attached to
> the particular flow.
> 
> As per normative references, RFC 6437 goes (underscores are mine):
> 
> > It is therefore RECOMMENDED
> > that source hosts support the flow label by setting the flow label
> > field for _all_packets_of_a_given_flow_ to the _same_value_ chosen from
> > an approximation to a discrete uniform distribution.
> 
> --
> Töma
> 
> >

-- 
---
[e-mail]