Re: How to reset ALTSVC

On Tue, Mar 31, 2015 at 3:22 PM, Martin Thomson <>

> On 31 March 2015 at 13:51, Bence Béky <> wrote:
> > I would like to be able to construct HTTP/1.1 Alt-Svc headers and HTTP/2
> > ALTSVC frames that indicate that the client should forget all previously
> > discovered alternative services for that given origin.  (With the caveat
> > from the earlier "Alt-Svc alternative cache invalidation (ext#16)" thread
> > that they would only invalidate alternative services that came from the
> same
> > discovery mechanism.)  The most obvious way would be to send an Alt-Svc
> > header field with an empty value, or an HTTP/2 ALTSVC frame with an empty
> > Alt-Svc-Field-Value.  However, the current draft calls for at least one
> > alternative in Section 3, and a mandatory Alt-Svc-Field-Value field in
> > Section 4.  I propose to allow zero alternatives like this:
> >
> > Alt-Svc = *( alternative *( OWS ";" OWS parameter ) )
> >
> > and to make Alt-Svc-Field-Value optional.
> You could send a redirect-to-self value without changing the grammar
> too.

​Perhaps I'm not familiar enough with the spec, but what is

Or you could set the max-age to 0.  Or both.

Yeah, that's definitely an option, but it seems like a bit of a hack to me.​

​It seems like there should be an explicit mechanism to tell a client to
forget whatever Alt-Svc entries it has. Using ma=0 still implies setting
*some* sort of alternative, but in this case there is no valid alternative
to be specified, I think.

Received on Wednesday, 1 April 2015 03:17:41 UTC