- From: Adrien de Croy <adrien@qbik.com>
- Date: Wed, 03 Oct 2007 17:25:23 +1300
- To: HTTP Working Group <ietf-http-wg@w3.org>
- Message-ID: <470319B3.9030706@qbik.com>
hello all I've just submitted a revised draft, covering the issues (hopefully) Julian raised regarding parsing and internationalisation (for which I adopted the method used by the Warning header). Regards Adrien de Croy -- Adrien de Croy - WinGate Proxy Server - http://www.wingate.com
Network Working Group de Croy
Internet-Draft QBIK
Intended status: Standards Track October 3, 2007
Expires: April 3, 2008
Progress notifications for HTTP
draft-decroy-http-progress-03
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Copyright Notice
Copyright (C) The Internet Society (2007).
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Abstract
This document specifies extenions to HTTP to allow progress messages
for user-agents during lengthy transactions.
Table of Contents
1. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Introduction and motivation . . . . . . . . . . . . . . . . . 4
2.1 The need for progress information. . . . . . . . . . . . . . 4
2.2 Aim of this document . . . . . . . . . . . . . . . . . . . . 4
3. Header Field Definitions . . . . . . . . . . . . . . . . . . . 5
3.1 Progress . . . . . . . . . . . . . . . . . . . . . . . . . . 5
3.1.1 Client request . . . . . . . . . . . . . . . . . . . . . 5
3.1.2 1xx Responses. . . . . . . . . . . . . . . . . . . . . . 6
4. Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
4.1 Progress Intervals . . . . . . . . . . . . . . . . . . . . . 7
5. Example. . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
6. Compatibilty issues. . . . . . . . . . . . . . . . . . . . . . 9
7. Implementation Notes . . . . . . . . . . . . . . . . . . . . . 10
8. Security Considerations . . . . . . . . . . . . . . . . . . . 11
9. Notes & TODO . . . . . . . . . . . . . . . . . . . . . . . . . 12
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13
11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 14
11.1. Normative References . . . . . . . . . . . . . . . . . . . 14
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 15
Intellectual Property and Copyright Statements . . . . . . . . . . 16
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1. Terminology
The keywords "MUST", "MUST NOT", "REQUIRED", "SHOULD", "SHOULD NOT"
and "MAY" that appear in this document are to be interpreted as
described in [RFC2119]
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2. Introduction and motivation
2.1 The need for progress information
Increasingly, resource transfers using HTTP are subject to ever-
more complex processing, particularly by proxy servers. Processing
such as scanning resources for viruses at an HTTP proxy creates
special problems that cannot be resolved cleanly with the current
specification of HTTP.
Many types of processing require access to an entire message body.
This can take considerable time to accumulate depending on upstream
link bandwidth and/or other factors. It may not be safe to send
any part of the resource to the client until processing is complete.
Frequently problems occur where human users of client agents give up
waiting for visible progress, typically resulting in retries wasting
time and network resources.
Furthermore, some automated clients will give up waiting when no
resource data is received within a certain timeframe.
There is a clear need for upstream agents to be able to provide
timely progress notifications to downstream agents to enable them to
make proper decisions about whether it is appropriate to keep
waiting.
2.3 Aim of this document
This document aims to solve this problem by providing a defined
mechanism whereby intermediaries or server agents can provide
progress notifications back to the client agent (and the human user),
thereby avoiding inappropriate timeouts, and retries.
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3 Header field definitions
This document defines a new header field to indicate progress.
This field allows optional textual state indication as well as
requiring numeric indication of completeness.
3.1 Progress
The Progress field MAY appear in any request message sent by a client
or in any server or proxy-generated 1xx series of response messages.
The Progress field MUST not appear in any other series of response
messages.
A server that complies with this document upon receiving a request
containing a Progress field MUST provide an interim response message
(1XX) within a reasonable time period AND provide further periodic
updates until the final response to the request is sent.
A proxy that complies with this document upon receiving a request
containing a Progress field MUST forward the tag unchanged to any
upstream agent. The proxy however is responsible for providing
progress messages to the client, and in the event that no upstream
notifications are available, it MUST satisfy the client progress
notifications whilst it is still prepared to process the request.
The proxy SHOULD pass any 1XX messages back through to the
client unchanged.
Progress indication is worthless if it is not timely. A discussion
of timing is in section 4
The form of the field is defined below
3.1.1 Client request
Progress = "Progress" ":" interval
interval = 1*4DIGIT
; the time (s) within which the client expects a response
Example:
Progress: 10
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3.1.2 1xx Responses
Progress = "Progress" ":" prog-num [SP prog-text]
prog-text = quoted-string
prog-num = percent | (bytes-processed "/" bytes-total)
percent = "%" %d0-100
; integer percentage complete, 0 - 100
bytes-processed = number
bytes-total = number | "UNKNOWN"
The textual information is intended to be displayed verbatim to a
user in an area usually associated with progress indication. The
numeric-progress field can be used to display a progress bar and/or
show how much data has been received by an upstream proxy.
The prog-text SHOULD be in a natural language and character set that
is most likely to be intelligible to the human user receiving the
response. This decision MAY be based on any available knowledge. The
default language is English and the default character set is
ISO-8859-1. If a character set other than ISO-8859-1 is used, it MUST
be encoded in the prog-text using the method described in [RFC2047].
Examples:
Progress: 20480/UNKNOWN "Generating content"
This could be sent by a server to indicate progress of generation of
content.
Progress: 20480/UNKNOWN "Download in progress"
Could be sent by an upstream proxy that is retrieving a message body,
has received 20480 bytes, and doesn't know the content length.
Progress: 1200000/1200000 "Download complete, scanning"
Could be sent by an upstream proxy that has just completed retrieving
a message body, has received 1200000 of 1200000 bytes, and is about
to scan the content before sending it on to the client.
Progress: %25 "Scanning content for viruses"
Could be sent by an upstream proxy that is currently 25% through
virus scanning of a message body.
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4. Timing
4.1 Progress intervals
The client Progress header indicates a time in seconds which is the
time within which it expects a response (either final or interim
containing progress information). The server or proxy SHOULD use
this specified time as the initial time and periodic time for
updates, or choose another time. If the server chooses to use
another periodic interval, this should be one chosen with regard to
the usefulness of the interval to a waiting human, and it is
suggested that an interval of about 5 - 10 seconds would be
appropriate.
Agents generating progress notifications MAY choose to send a
notification whenever any significant change in state occurs.
However in the interests of bandwidth, agents SHOULD NOT send
progress notifications more frequently than once per second.
This includes an intermediary which may be generating notifications
and relaying notifications from upstream.
It is left up to the implementor of intermediaries to choose which
notifications they may choose to relay or generate themselves,
remembering that this is intended for a human user, but will be
useful to automated agents as well.
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5. Example
+-------------------+------------------------+--------------------+
| Client | Intermediary | Server |
+-------------------+------------------------+--------------------+
Connects to intermediary
->
GET http://www.wingate.com/bigfile.zip HTTP/1.1
Host: www.wingate.com
Progress: 10
->
GET /bigfile.zip HTTP/1.1
Host: www.wingate.com
Progress: 10
<-
HTTP/1.1 200 OK
Content-Length: 20000000
...
time elapses
<-
HTTP/1,1 102 Processing
Progress: 1000000/20000000 "Downloading"
time elapses
<-
HTTP/1,1 102 Processing
Progress: 20000000/20000000 "Downloaded, Scanning"
time elapses
<-
HTTP/1,1 102 Processing
Progress: %25 "Scanning"
time elapses
<-
HTTP/1,1 102 Processing
Progress: %75 "Scanning"
<-
HTTP/1.1 200 OK
Content-Length: 20000000
...
Transfers resource to client.
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6. Compatibilty issues.
None identified. RFC2616 already mandates that any agent must be
able to cope with multiple interim responses.
A server not understanding the Progress header in a request will
not generate progress notifications.
A client unaware of this document will not generate requests with
the Progress header.
A proxy not understanding the Progress header already should be
passing unknown headers through to upstream, and also passing back
1XX responses.
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7. Implementation Notes
Most user agents provide screen real-estate to display progress,
often in the "status bar" of the window. It is envisaged that the
progress notifications outlined in this document would be shown in
there.
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8. Security Considerations
No security issues identified with use of this proposal.
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9. Notes & TODO
* modified from version 00 to remove sections on flow control issues.
* modified from version 01 to allow for internationalisation of
strings, slight modification to syntax. Minor editorial changes.
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10. IANA Considerations
None.
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11. References
11.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2616] Fielding, R., Gettys, J., Mogul, J., Frystyk, H.,
Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext
Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999.
[RFC4559] Brezak, J. "SPNEGO-based Kerberos and NTLM HTTP
authentication in Microsoft Windows", RFC 4559, June 2006
[RFC2047] Moore, K., "MIME (Multipurpose Internet Mail Extensions)
Part Three: Message Header Extensions for Non-ASCII Text",
RFC 2047, November 1996.
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Author's Address
Adrien de Croy
Qbik New Zealand Limited
PO Box 3548
Shortland St
Auckland
New Zealand
Email: adrien@qbik.com
URI: http://www.wingate.com/
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Received on Wednesday, 3 October 2007 04:25:04 UTC