Re: [PATCH 1/4] sunrpc: flag transports as using IETF approved congestion control protocols

Tom Talpey
2017-02-24T15:08:12Z

On 2/23/2017 3:55 PM, Jason Gunthorpe wrote:
> On Thu, Feb 23, 2017 at 03:33:53PM -0500, Tom Talpey wrote:
>
>> The key words are "IETF-approved". Mitigation and Interaction are
>> operational decisions, not protocol design.
>
> We are talking about this bit from RFC 3530 ?
>
> Where an NFS version 4 implementation supports operation over the IP
> network protocol, the supported transports between NFS and IP MUST be
> among the IETF-approved congestion control transport protocols, which
> include TCP and SCTP.
>
> This gives most of RDMA an out as it is not over the IP protocol. The
> only obvious troubled one is RoCEv2..

RFC7530 has updated this text somewhat, but it's similar, yes.

https://tools.ietf.org/html/rfc7530#section-3.1

The specification language specifically calls out IP-based transports,
which is why I mentioned that RoCEv1, being non-IP-based and not even
truly routable, could obtain a bye. But the NFS layer IMO should really
not be digging down to this level. I think it would be much better if
each transport could expose a relevant attribute, which NFS could
optionally inspect.

As you mention, RoCEv2 is a bit of a pickle. It's UDP/IP-based, and it
does have end-to-end congestion control, but technically speaking it
is not "IETF approved". I'm not sure what call to make there.

Tom.
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