Re: flow control description in draft

[Ian Swett <[e-mail]>]

On Fri, Jul 28, 2017 at 11:18 AM, Subodh Iyengar <[e-mail]> wrote:

> The flow control language in the draft is a bit confusing right now, and I
> could use a bit more clarity on the intention
>
> For example in MAX_DATA and MAX_STREAM_DATA the data is defined as
>
> "A 64-bit unsigned integer indicating the maximum amount of data that can
> be sent on the entire connection, in units of 1024 octets. That is, the
> updated connection-level data limit is determined by multiplying the
> encoded value by 1024."
>
> This seems like it means that flow control is advertised in terms of
> number of bytes that you can send from that moment.
>

> However from the Flow control section:
>
> "A receiver sends MAX_DATA or MAX_STREAM_DATA frames to the sender to
> advertise additional credit by sending the absolute byte offset in the
> connection or stream which it is willing to receive."
>
> I think that we definitely mean offset here in both cases, i.e.
>
> MAX_DATA = sum of max offset of all streams that are allowed
>
> MAX_STREAM_DATA = max offset on a stream
>
>
> Yes, that's what the spec means.  I thought it was fairly clear, but if
you think it's confusing, a PR to improve the wording would be appreciated.


> Let's say the conn flow control limit of the receiver is 50. All units in
> multiples of 1024.
>
> initial state of receiver
> stream1 -->  [0, 10]
> stream2 -->  [0, 20]
>
> stream3 -->  [0, 20]
>
>
> So the sender has consumed his entire flow control window. Then the
> receiver consumes 10 (*1024) bytes from stream1:
>
> stream1 ---> (10, 10)
>
> stream2 ---> [0, 20]
>
> stream3 ---> [0, 20]
>
>
> so now the conn window has 10 (*1024) bytes remaining, what does the
> receiver send in their update:
>
>
> MAX_DATA = 10
>
> or
>
> MAX_DATA = 60
>
>
> I think we mean 60 here. It makes it much easier to maintain the flow
> control in that case.
>
>
> Subodh
>
>
>