Question about prioritization state management

[laike9m]

I found the example in 5.3.4 Prioritization State Management very confusing.

In the previous paragraph, it says

Resources are shared between streams with the same parent stream, which means that if a stream in that set closes or becomes blocked, any spare capacity allocated to a stream is distributed to the immediate neighbors of the stream.

And in the following example:

Prior to the removal of stream A, if streams A and D are unable to proceed, then stream C receives all the resources dedicated to stream A.

It seems to me a bit contradictory, since A and B are neighbors with the same parent stream, then why doesn’t B share resources dedicated to A?

I know this question may seem dumb, but I do hope to get answers from the experts. Thank you.

[laike9m]

Yesterday I sent an email to ietf-http-wg-request@w3.org asking the same question, but got a reply saying:

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So I guess people can't really asking questions that way.

[martinthomson]

The mailing list is ietf-http-wg@w3.org and you can subscribe to that list using the links here: https://lists.w3.org/Archives/Public/ietf-http-wg/ Subscribing will let you send (and receive) email.

The answer is that A and B do share resources, but they share the resources of their parent. In the example, this node is not named, it might be the root of the tree.

You might be right about the example being confusing. If A is blocked, then its dependents (C and D) should not proceed. However, if A is complete, then C and D should receive any resources that would have been allocated to A. This probably needs an erratum.

[laike9m]

Thx Martin. Here's my understanding, correct me if I'm wrong:
There are two cases:

1. If A is blocked/closed but not removed from the tree, then B gets all resources that A owns.
2. If A is removed from the dependency tree, then B, C, D share the resources, each get 1/3.

[martinthomson]

Three cases:

1. If A is blocked, then B gets all resources that A owns.
2. If A is closed but not removed from the tree, C and D gets A's share (1/4 each, assuming equal weights).
3. If A is removed from the dependency tree, then B, C, D share the resources, each get 1/3 (assuming equal weighting for each).

The example talks about 2, but neglects to mention 1.

[laike9m]

case 2, Is it "removed" or "not removed"?

[martinthomson]

Oops, I meant not removed. Edited.

[laike9m]

Thx for this detailed explanation 👍