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RFC 7540, "Hypertext Transfer Protocol Version 2 (HTTP/2)", May 2015

Note: This RFC has been obsoleted by RFC 9113

Note: This RFC has been updated by RFC 8740

Source of RFC: httpbis (wit)

Errata ID: 5249
Status: Rejected
Type: Technical
Publication Format(s) : TEXT

Reported By: Vasiliy Faronov
Date Reported: 2018-02-01
Rejected by: Alexey Melnikov
Date Rejected: 2018-09-04

Section 3.2.1 says:

     HTTP2-Settings    = token68

It should say:

     HTTP2-Settings    = [ token68 ]


An initial SETTINGS frame is explicitly allowed by Section 3.5 to be empty. The payload of an empty SETTINGS frame is an empty sequence of octets, whose base64url encoding is an empty string. Thus, the HTTP2-Settings header field ought to permit an empty string as value. But the ABNF for "token68" does not match an empty string.
Martin Thomson wrote:

The observation is correct. However, I'm not sure that this is the
solution I would choose. I'm not sure, but I think that an empty
header field would cause problems. Maybe the right conclusion to draw
here is that you have to include at least one setting if you use this
header field.


Agreement in the WG to reject the erratum as proposed, but a better fix might be proposed separately.

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