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Subject: Re: [nfsv4] NFS over QUIC
From:   Chuck Lever <chucklever@gmail.com>
In-Reply-To: <20200904003242.GB4788@fieldses.org>
Date:   Thu, 3 Sep 2020 20:53:23 -0400
Cc:     Linux NFS Mailing List <linux-nfs@vger.kernel.org>,
        NFSv4 <nfsv4@ietf.org>, stfrench@microsoft.com
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 <20200904003242.GB4788@fieldses.org>
To:     Bruce Fields <bfields@fieldses.org>
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> On Sep 3, 2020, at 8:32 PM, Bruce Fields <bfields@fieldses.org> wrote:
> 
> On Thu, Sep 03, 2020 at 07:48:19PM -0400, Chuck Lever wrote:
>> Hi Bruce-
>> 
>>> On Sep 3, 2020, at 5:52 PM, J. Bruce Fields <bfields@fieldses.org> wrote:
>>> 
>>> I've been thinking about what might be required for NFS to run over
>>> QUIC.
>>> 
>>> Also cc'ing Steve French in case he's thought about this for CIFS/SMB.
>>> 
>>> I don't have real plans.  For Linux, I don't even know if there's a
>>> kernel QUIC implementation planned yet.
>>> 
>>> QUIC uses TLS so we'd probably steal some stuff from the NFS/TLS draft:
>>> 
>>> 	https://datatracker.ietf.org/doc/draft-cel-nfsv4-rpc-tls/
>> 
>> The link to the latest version of that document is
>> 
>> https://datatracker.ietf.org/doc/draft-ietf-nfsv4-rpc-tls/
>> 
>>> For example, section 4.3, which explains how to authenticate on top of
>>> an already-encrypted session, should also apply to QUIC.
>> 
>> Most of the document's content will be re-used for defining
>> RPC-over-QUIC, for example the ALPN defined in Section 8.2.
>> Lars Eggert, a chair of the QUIC WG, has been helping guide
>> the RPC-over-TLS effort with an eye towards using QUIC for
>> RPC when QUIC becomes more mature.
>> 
>> I thought the plan was to write a specification of RPC-over-
>> QUIC as a new RPC transport type with a netid and uaddr along
>> with a definition of the transport semantics (a la TI-RPC).
>> The document would need to explain record marking, peer
>> authentication, how to use multi-path and multi-stream support,
>> and so on.
>> 
>> Making NFS work on that transport should then be straightforward
>> enough that perhaps additional standards work wouldn't be
>> necessary.
> 
> Oh, OK, good.  Sounds like you're way ahead of me, then, I didn't know
> there was a plan.

That's all there is for the moment! :-)


> --b.
> 
>>> QUIC runs over UDP, so I think all that would be required to negotiate
>>> support would be to attempt a QUIC connection to port 2049.
>>> 
>>> The "Transport Layers" section in the NFS RFCs:
>>> 
>>> 	https://tools.ietf.org/html/rfc5661#section-2.9
>>> 
>>> requires transports support reliable and in-order transmission, forbids
>>> clients from retrying a request unless a connection is lost, and forbids
>>> servers from dropping a request without closing a connection.  I'm still
>>> vague on how those requirements interact with QUIC's connection
>>> management and 0-RTT reconnection.
>>> 
>>> https://www.ietf.org/id/draft-ietf-quic-applicability-07.txt looks
>>> useful, as a guide for applications running over QUIC.  It warns that
>>> connections can time out fairly quickly.  For timely callbacks over NFS
>>> sessions, that means we need the client to ping the server regularly.
>>> Sounds like that's what they do for HTTP/QUIC to make server push
>>> notifications work:
>>> 
>>> 	https://tools.ietf.org/html/draft-ietf-quic-http-09#section-5
>>> 
>>> 	HTTP clients are expected to use QUIC PING frames to keep
>>> 	connections open.  Servers SHOULD NOT use PING frames to keep a
>>> 	connection open.  A client SHOULD NOT use PING frames for this
>>> 	purpose unless there are responses outstanding for requests or
>>> 	server pushes.
>>> 
>>> QUIC allows multiple streams per connection--I wonder how we might use
>>> that.  RFC 5661 justifies the requirement for an ordered transport with:
>>> 
>>> 	Ordered delivery simplifies detection of transmit errors, and
>>> 	simplifies the sending of arbitrary sized requests and responses
>>> 	via the record marking protocol.
>>> 
>>> So as long as we don't try to split a single RPC among streams, I think
>>> we're OK.  Would a stream per session slot be reasonable?  I'm not sure
>>> what the cost of a stream is.
>>> 
>>> Do we need to add a new universal address type so the protocol can
>>> specify QUIC endpoints when necessary?  (For server-to-server-copy, pnfs
>>> file layouts, fs_locations, etc.)  All QUIC needs is an IP address and
>>> maybe a port, so maybe the existing UDP/TCP addresses are enough?
>> 
>> --
>> Chuck Lever
>> chucklever@gmail.com

--
Chuck Lever
chucklever@gmail.com