Content-Length SHOULD be sent

[mnot@…]

Currently, p1 says:

When a message is allowed to contain a message body, does not have a Transfer-Encoding header field, and has a payload body length that is known to the sender before the message header section has been sent, the sender should send a Content-Length header field to indicate the length of the payload body as a decimal number of octets.

This unqualified SHOULD leads people to convoluted readings of the spec where Content-Length is required to be sent on a GET request.

[mnot@…]

Proposal:

--8<-- The Content-Length header indicates the size of a message body as a decimal number of octets. The sender SHOULD set Content-Length if:

o the message is allowed to contain a body, o the Transfer-Encoding header field is not included, and o the size of the message body is known at the time that headers are sent.

Messages that do not define a meaning for the body MAY either omit the Content-Length header field or include a value of 0. -->8--

[fielding@…]

From [2034]:

Clarify when Content-Length SHOULD be sent. Addresses #420

[fielding@…]

The suggested text does not consider all requirements. I have rewritten those parts that needed clarifying.