Re: QUIC idle timeouts and path idle timeouts

[Ian Swett <[e-mail]>]

This is a real problem, but I'm unsure what the best way to approach it is.

I think you're suggesting that a large server operator could try to infer
NAT timeouts for clients of different IP prefixes and communicate that to
the client as a suggested keepalive/ping timeout?  I'm curious about how to
infer NAT timeouts?  Our servers detect a dead connection, but I'm not sure
how to tell what the reason is and more specifically the NAT timeout?
Sometimes devices just drop off the network.

As you may know, Chrome will send a PING as a keepalive after 15 seconds of
idle only if there are outstanding requests (ie: hanging GETs).  The number
was chosen somewhat arbitrarily and is certainly not optimal, but it did
fix some use cases where hanging GETs were otherwise failing.

Thanks, Ian

On Wed, Jul 24, 2024 at 5:55 PM Martin Thomson <[e-mail]> wrote:

> The intent of the idle timeout was to have that reflect *endpoint*
> policy.  That is, it is independent of path.
>
> It's certainly very interesting to consider what you might do about paths
> and keep-alives (or not).  But that's a separable problem.  Having a way
> for endpoints to share their information about timeouts might work, but I
> worry that that will lead to wasteful keepalive traffic.  How would we
> ensure that keepalives are not wasteful?
>
> Is there a better way, such as a quick connection continuation?
>
> On Wed, Jul 24, 2024, at 11:24, Lucas Pardue wrote:
> > Hi folks,
> >
> > Wearing no hats.
> >
> > There's been some chatter this week during IETF about selecting QUIC
> > idle timeouts in the face of Internet paths that might have shorter
> > timeouts, such as NAT.
> >
> > This isn't necessarily a new topic, there's past work that's been done
> > on measurements and attempts to capture that as in IETF documents. For
> > example, Lars highlighted a study of home gateway characteristics from
> > 2010 [1]. Then there's RFC 4787 [2], and our very own RFC 9308 [3]
> >
> > There's likely other work that's happened in the meantime that has
> > provided further insights.
> >
> > All the discussion got me wondering whether there might be room for a
> > QUIC extension that could hint at the path timeout to the peer. For
> > instance, as a server operator, I might have a wide view of network
> > characteristics that a client doesn't. Sending keepalive pings from the
> > server is possible but it might not be in the client's interest to
> > force it to ACK them, especially if there are power saving
> > considerations that would be hard for the server to know. Instead, a
> > hint to the peer would allow it to decide what to do. That could allow
> > us to maintain a large QUIC idle timeouts as befitting of the
> > application use case, but adapt to the needs of the path for improved
> > connection reliability.
> >
> > Such an extension could hint for each and every path, and therefore a
> > benefit to multipath, which has some addition path idle timeout
> > considerations [4].
> >
> > Thoughts?
> >
> > [1] - https://dl.acm.org/doi/10.1145/1879141.1879174
> > [2] -  https://www.rfc-editor.org/rfc/rfc4787.html
> > [3] - https://www.rfc-editor.org/rfc/rfc9308.html#section-3.2
> > [4] -
> >
> https://www.ietf.org/archive/id/draft-ietf-quic-multipath-10.html#name-idle-timeout
>
>