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Questions on Frame Size

From: Shigeki Ohtsu <ohtsu@iij.ad.jp>
Date: Thu, 20 Jun 2013 14:32:45 +0900
Message-ID: <51C293FD.1040806@iij.ad.jp>
To: HTTP Working Group <ietf-http-wg@w3.org>
Hi,

The issues about frame size were discussed and might had some
agreements at SF interium but please let me ask some questions on the
current spec of "3.3.2 Frame Size" which is updated by
https://github.com/http2/http2-spec/commit/fd703b572cfc527582c0716e59f2c4044ae195a8

1. "For instance, individual DATA and HEADERS frames used to express
HTTP request and response messages (see Section 4) are not permitted
to exceed 16,383 octets of payload."

PUSH_PROMISE is not listed.
Is the data size of PUSH_PROMISE also limited to 16K or is it exceptional
for some reason?

2. "The absolute maximum amount of payload data any individual frame
 can contain is 65,535 octets. All implementations SHOULD be capable
 of receiving and minimally processing frames up to this size."

If PUSH_PROMISE has a 16K limit, the max frame size is still 64K,
however, any other frames besides DATA, HEADERS and PUSH_PROMISE
are only several octets at most.

Is it for the future extension not to change the frame length to 14bit?
If so, why the spec requires all implementations to support the 64K frame
 size only for the future extension?

Regards,
Received on Thursday, 20 June 2013 05:33:16 UTC

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