Re: Unidirectional streams PR

[Christian Huitema <[e-mail]>]

On 6/28/2017 6:23 PM, Ian Swett wrote:

> I updated my PR(#656 <https://github.com/quicwg/base-drafts/pull/656>)
> today, sorry for the delay.  I attempted to address the issues
> identified with text.  Some may prefer more tweaks to the state
> diagram, which are also possible, so I'm open to suggestions.
>
> In the meantime, I've been considering other alternatives, including
> variations on Mike's direction and a variation of the "Do Nothing"
> option which involved the application signaling to the transport that
> streams of a certain sort(ie: server to client for server push) were
> unidirectional, as GQUIC does today.  Overall, I think the approach
> I've outlined does a good job of iterating on existing deployment
> experience and adding explicit signaling for unidirectional streams
> instead of implicit signaling at the application layer.  There are
> pros and cons to both explicit and implicit signaling, but I think
> explicit signaling is more complete and less prone to application error.
>

I understand how to handle concurrent stream limits with plain
bidirectional streams or with plain unidirectional streams, but things
are not so clear when we start mixing models by adding a unidirectional
option to bidirectional or vice versa. In the clean models, we can count
the number of streams initiated by one entity and not yet closed. But in
the mixed models, what do we count, exactly?

For example, let's suppose that in an unidirectional stream model, the
client creates a stream that also "implies" a stream creation in the
other direction. Does this implied stream count against the server limit
or the client limit?

Or vice versa. Suppose that in a bidirectional stream model the client
creates a stream that is declared as actually unidirectional. And
suppose that this stream is immediately closed -- a stream frame with
both the FIN bit and the PR 656 UNI bit set. This stream counts against
the client's number of concurrent streams, but it is immediately closed
by both parties. Does it count as zero?
-- 

Christian Huitema