Changeset 2065 for draft-ietf-httpbis/latest/p2-semantics.xml
- Timestamp:
- 29/12/12 08:22:04 (10 years ago)
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draft-ietf-httpbis/latest/p2-semantics.xml
r2064 r2065 2585 2585 <iref primary="true" item="Status Codes Classes" subitem="1xx Informational" x:for-anchor=""/> 2586 2586 <t> 2587 This class of status code indicates a provisionalresponse,2587 This class of status code indicates an interim response, 2588 2588 consisting only of the status-line and optional header fields, and is 2589 2589 terminated by an empty line. There are no required header fields for this … … 3628 3628 the message was originated, having the same semantics as the Origination 3629 3629 Date Field (orig-date) defined in <xref target="RFC5322" x:fmt="of" x:sec="3.6.1"/>. 3630 The field value is an HTTP-date, as defined in <xref target="http.date"/> ;3631 it &MUST; be sent inrfc1123-date format.3630 The field value is an HTTP-date, as defined in <xref target="http.date"/>, 3631 though a sender &MUST; generate a Date value in the rfc1123-date format. 3632 3632 </t> 3633 3633 <figure><artwork type="abnf2616"><iref primary="true" item="Grammar" subitem="Date"/> … … 3641 3641 </artwork></figure> 3642 3642 <t> 3643 Origin servers &MUST; include a Date header field in all responses, 3644 except in these cases: 3645 <list style="numbers"> 3646 <t>If the response status code is <x:ref>100 (Continue)</x:ref> or 3647 <x:ref>101 (Switching Protocols)</x:ref>, the response &MAY; include a 3648 Date header field, at the server's option.</t> 3649 3650 <t>If the response status code conveys a server error, e.g., <x:ref>500 3651 (Internal Server Error)</x:ref> or <x:ref>503 (Service Unavailable)</x:ref>, 3652 and it is inconvenient or impossible to generate a valid Date.</t> 3653 3654 <t>If the server does not have a clock that can provide a 3655 reasonable approximation of the current time, its responses 3656 &MUST-NOT; include a Date header field.</t> 3657 </list> 3658 </t> 3659 <t> 3660 A received message that does not have a Date header field &MUST; be 3661 assigned one by the recipient if the message will be cached by that 3662 recipient. 3663 </t> 3664 <t> 3665 Clients can use the Date header field as well; in order to keep request 3666 messages small, they are advised not to include it when it doesn't convey 3667 any useful information (as is usually the case for requests that do not 3668 contain a payload). 3669 </t> 3670 <t> 3671 The HTTP-date sent in a Date header field &SHOULD-NOT; represent a date and 3672 time subsequent to the generation of the message. It &SHOULD; represent 3673 the best available approximation of the date and time of message 3674 generation, unless the implementation has no means of generating a 3675 reasonably accurate date and time. In theory, the date ought to 3676 represent the moment just before the payload is generated. In 3677 practice, the date can be generated at any time during the message 3678 origination without affecting its semantic value. 3643 When a Date header field is generated, the sender &SHOULD; generate its 3644 field value as the best available approximation of the date and time of 3645 message generation. In theory, the date ought to represent the moment just 3646 before the payload is generated. In practice, the date can be generated at 3647 any time during message origination. 3648 </t> 3649 <t> 3650 An origin server &MUST-NOT; send a Date header field if it does not have a 3651 clock capable of providing a reasonable approximation of the current time. 3652 An origin server &MAY; send a Date header field if the response is in the 3653 <x:ref>1xx (Informational)</x:ref> or <x:ref>5xx (Server Error)</x:ref> 3654 class of status codes. 3655 An origin server &MUST; send a Date header field in all other cases. 3656 </t> 3657 <t> 3658 A recipient with a clock that receives a response message without a Date 3659 header field &MUST; record the time it was received and append a 3660 corresponding Date header field to the message's header block if it is 3661 cached or forwarded downstream. 3662 </t> 3663 <t> 3664 A user agent &MAY; send a Date header field in a request, though generally 3665 will not do so unless it is believed to convey useful information to the 3666 server. For example, custom applications of HTTP might convey a Date if 3667 the server is expected to adjust its interpretation of the user's request 3668 based on differences between the user agent and server clocks. 3679 3669 </t> 3680 3670 </section>
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