2004/id/draft-cohen-http-305-306-responses-00.txt



HTTP Working Group                                            Josh Cohen
Internet-Draft                             Netscape Communications Corp.
                                                         5 December 1996

                  HTTP/1.1 305 and 306 Response Codes

                    <draft-cohen-http-305-306-responses-00.txt>

Status of this Memo

   This document is an Internet-Draft.  Internet-Drafts are working
   documents of the Internet Engineering Task Force (IETF), its areas,
   and its working groups.  Note that other groups may also distribute
   working documents as Internet-Drafts.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet- Drafts as reference
   material or to cite them other than as ``work in progress.''

   To learn the current status of any Internet-Draft, please check the
   ``1id-abstracts.txt'' listing contained in the Internet- Drafts
   Shadow Directories on ftp.is.co.za (Africa), nic.nordu.net (Europe),
   munnari.oz.au (Pacific Rim), ds.internic.net (US East Coast), or
   ftp.isi.edu (US West Coast).

Abstract

   The HTTP/1.1 RFC specifies a response code '305 Use Proxy' which is
   intended to cause a client to retry the request using a specified
   proxy server.  This functionality is important, but underspecified in
   the current spec.  The spec does not specify for how long or which
   URLs the redirect applies to, or how proxies can deal with or
   generate similar responses.  This draft proposes a specification for
   both the 305 response and a new response, "306 Switch Proxy".


J. Cohen          HTTP/1.1 305 and 306 Response Codes           [Page 1]


INTERNET-DRAFT                                           5 December 1996


Summary

 1.0 Response Codes

  1.1 305 Use Proxy
  1.2 306 Switch Proxy
  1.3 506 Redirection Failed

 2.0 Headers

  2.1 Set-proxy:
  2.2 Location:

 3.0 Methods

  3.1 OPTIONS

 4.0 Operational Constraints

 5.0 Notes


1.0 Response Codes

 1.1 305 Use Proxy

   The 305 is generated by an origin server to indicate that the client,
   or proxy, should use a proxy to access the requested resource.

   The request SHOULD be accompanied by a 'Set-proxy' response header
   indicating what proxy is to be used. The client will parse the 'Set-
   proxy' header as defined below to decide how long, for what URLs it
   should use the specified proxy.

   If the 305 response is not accompanied by a 'Set-proxy' header, it
   MUST be accompanied by a 'Location' header.  The 'Location' header
   will specify a URL to the proxy.

   If both headers are present in the response, the client SHOULD use
   the 'Set-proxy' header only.

 1.2 306 Switch Proxy

   The 306 response is generated by a proxy server to indicate that the
   client or proxy should use the information in the accompanying 'Set-
   proxy' header to choose a proxy for subsequent requests.

   The 306 response code MUST be accompanied by the 'Set-proxy' response


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INTERNET-DRAFT                                           5 December 1996


   header.  The client or proxy will parse the 'Set-proxy' header to
   determine which proxy to use, how long to use it, and for which URLs
   to use it.

 1.3 506 Redirection Failed

   The 506 response is returned when a redirection fails or is refused
   by a proxy or client.  If the redirection response included a body,
   then it SHOULD be included in the 506 response.

2.0 Headers

 2.1 'Set-proxy' Response Header

           The 'Set-proxy' header is defined as:

           Set-proxy: "Set-proxy" ":" 1(
                   action #(parameters)
                   )

           parameters = #( ( "scope" "=" scopePattern ) |
                   ( proxyURI "=" URI ) |
                   lifetime )

           lifetime = ( "seconds"  "=" integer )
                   | ( "hits"      "=" integer )

           action =  ( "DIRECT"
                   | "IPL"
                   | "SET" )
                   ) ";"

           scopePattern = "*" | "-" | URIpattern

   An example header:
       Set-proxy: SET ; proxyURI = "http://proxy.me.com:8080/",
           scope="http://", seconds=5

 action

   The first item, "action" specifies the type or mode of the change.
   Possible modes are:


   DIRECT
    Attempt to connect directly, with no proxy


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   IPL
    Initial Program Load, the client or proxy should attempt to revert
    back to its default or initial proxy setting.  This is meant to
    instruct a client to re-fetch its proxy configuration, or PAC file.
    When set, the accompanying scope field MUST be "*" A client receiv-
    ing this response SHOULD prompt the user for confirmation.


    If accompanied by a 'proxyURI' parameter, a proxy or client MAY use
    the value as a URL containing a configuration to retrieve.  If a
    client  does so, it MUST prompt the user for confirmation.


   SET
    Set to parameter "proxyURI".  The client should use the URL speci-
    fied for "proxyURI" as the proxy.  If the SET mode is specified, the
    parameter, "proxyURI", MUST be present.

 Scope

    Scope refers to a URI prefix pattern that specifies which URIs are
    subject to this header setting.  URIs should be matched against the
    scope with this rule :

     The scope "*" means all requests
     The scope "-" means this EXACT URL ONLY

    Otherwise, the URL is compared with the scope after it is:


   *   truncated to the length of the scope


   *   domain names are set in reverse order.

     For example:

       scope = "http://com.foo.www/services/"

       URL "http://www.foo.com/services/express/2day.html"
       transformed: "http://com.foo.www/services/express/" (MATCH)

     Another example:

       scope = "http://com.ups/"      URL "http://www.ups.com/"  (MATCH)
       URL "http://www.fedex.com/" (FAIL)


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INTERNET-DRAFT                                           5 December 1996


     The lifetime parameter specifies how long the specified proxy
     should be used.  If lifetime is specified as "seconds" then the
     proxy setting remains in effect for 'integer' seconds.  If lifetime
     is specified in 'hits' then the proxy setting remains in effect for
     'integer' transactions.

 2.2 Location Header


     In the original HTTP/1.1 spec, the 'Location' header was used to
     indicate the proxy setting.  Its use is DEPRECATED by the 'Set-
     proxy' header in the context of a 305 response. All new implementa-
     tions MUST send the Set-proxy header.  Implementations MAY send the
     'Location' header so as to allow backward compatibility.


     If the 'Location' header is specified, it should contain a URI of
     the proxy.  If the Set-proxy header is not specified, the client
     should use this proxy for just one request, and only for the origi-
     nally requested exact URL.

 3.0 Methods


     A client or proxy receiving a 305 or 306, should use the OPTIONS
     method to determine if the server or proxy it is talking to actu-
     ally is an HTTP/1.1 server supporting 305 and 306 responses.


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INTERNET-DRAFT                                           5 December 1996


4.0 Operational Constraints


   * Both the 305 and 306 response codes are HOP by HOP.  A proxy server
     MUST not forward a 305 or 306 respose code (unless it generated the
     306).


   * A webserver MUST NOT send a 306 response under any circumstances


   * A proxy server MUST NOT generate a 305 response.


   * A client or proxy SHOULD NOT accept a 306 from a proxy that it
     learned of via a 305 response code.


   * A client or proxy MAY maintain state and allow a lifetime to extend
     beyond a session or restart.


   * A 'Set-proxy: IPL' SHOULD override any previous 'Set-proxy' header.


   * A 305 or 306 response MAY contain a body containing an explanation
     of the redirect for clients which do not understand the redirect


   * In the absence of any parameter, the following defaults should be
     used:

       lifetime = this transaction only
       scope = this exact URL only


   * When receiving a 305 response, the client or proxy will enforce the
     following rule with respect to the scope.

     The scope specified must be more restrictive than the transformed
     URL in question.

     Example: (in order of restrictiveness)

       http://com.ups.www/services/express/1day.html ( most restrictive)
             http://com.ups.www/ (all requests for only www.ups.com )
             http://com.ups ( all requests for ups.com )
             http://  ( for all http requests )


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INTERNET-DRAFT                                           5 December 1996


       *  ( all requests )

     If the scope returned with a 305 response is less restrictive than
     the requested URL, the client MUST prompt the user for confirmation
     before accepting the new proxy setting.


   * Since HTTP/1.0 proxies may unknowingly forward a 305 or 306
     response code that was generated maliciously or in good faith, the
     client must attempt to ascertain if the proxy with which it is
     directly communicating is HTTP/1.1 and if it supports the 'Set-
     proxy' header.  To determine this, the client or proxy should use
     the OPTIONS method to make a request check for this feature.


Security Considerations

     Great care should be taken when implementing client side actions
     based on the 305 or 306.  Since older proxies may unknowingly for-
     ward either of these reponses, clients should be prepared to check
     the validity.


   * Please read the section 'Operational Constraints'


   * A client or proxy MUST NOT accept a 305 response from a proxy.


   * A client or proxy MUST NOT accept a 306 response from an origin
     server.


   * When receiving a 306 response from a proxy, the client MUST verify
     that the proxy supports the 306 response with a METHODS request.

5.0 Notes

     Further specification is needed to define exactly how to use
     METHODs, or another mechanism to determin if set-proxy is sup-
     ported.

Author's Address

     Josh Cohen
     Netscape Communications Corporation
     501 E. Middlefield Rd
     Mountain View, CA 94043


J. Cohen          HTTP/1.1 305 and 306 Response Codes           [Page 7]


INTERNET-DRAFT                                           5 December 1996


     Phone (415) 937-4157
     EMail: josh@netscape.com


J. Cohen          HTTP/1.1 305 and 306 Response Codes           [Page 8]


1
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5
6
7	HTTP Working Group Josh Cohen
8	Internet-Draft Netscape Communications Corp.
9	5 December 1996
10
11	HTTP/1.1 305 and 306 Response Codes
12
13	<draft-cohen-http-305-306-responses-00.txt>
14
15	Status of this Memo
16
17	This document is an Internet-Draft. Internet-Drafts are working
18	documents of the Internet Engineering Task Force (IETF), its areas,
19	and its working groups. Note that other groups may also distribute
20	working documents as Internet-Drafts.
21
22	Internet-Drafts are draft documents valid for a maximum of six months
23	and may be updated, replaced, or obsoleted by other documents at any
24	time. It is inappropriate to use Internet- Drafts as reference
25	material or to cite them other than as ``work in progress.''
26
27	To learn the current status of any Internet-Draft, please check the
28	``1id-abstracts.txt'' listing contained in the Internet- Drafts
29	Shadow Directories on ftp.is.co.za (Africa), nic.nordu.net (Europe),
30	munnari.oz.au (Pacific Rim), ds.internic.net (US East Coast), or
31	ftp.isi.edu (US West Coast).
32
33	Abstract
34
35	The HTTP/1.1 RFC specifies a response code '305 Use Proxy' which is
36	intended to cause a client to retry the request using a specified
37	proxy server. This functionality is important, but underspecified in
38	the current spec. The spec does not specify for how long or which
39	URLs the redirect applies to, or how proxies can deal with or
40	generate similar responses. This draft proposes a specification for
41	both the 305 response and a new response, "306 Switch Proxy".
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58	J. Cohen HTTP/1.1 305 and 306 Response Codes [Page 1]
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65
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67	Summary
68
69	1.0 Response Codes
70
71	1.1 305 Use Proxy
72	1.2 306 Switch Proxy
73	1.3 506 Redirection Failed
74
75	2.0 Headers
76
77	2.1 Set-proxy:
78	2.2 Location:
79
80	3.0 Methods
81
82	3.1 OPTIONS
83
84	4.0 Operational Constraints
85
86	5.0 Notes
87
88
89	1.0 Response Codes
90
91	1.1 305 Use Proxy
92
93	The 305 is generated by an origin server to indicate that the client,
94	or proxy, should use a proxy to access the requested resource.
95
96	The request SHOULD be accompanied by a 'Set-proxy' response header
97	indicating what proxy is to be used. The client will parse the 'Set-
98	proxy' header as defined below to decide how long, for what URLs it
99	should use the specified proxy.
100
101	If the 305 response is not accompanied by a 'Set-proxy' header, it
102	MUST be accompanied by a 'Location' header. The 'Location' header
103	will specify a URL to the proxy.
104
105	If both headers are present in the response, the client SHOULD use
106	the 'Set-proxy' header only.
107
108	1.2 306 Switch Proxy
109
110	The 306 response is generated by a proxy server to indicate that the
111	client or proxy should use the information in the accompanying 'Set-
112	proxy' header to choose a proxy for subsequent requests.
113
114	The 306 response code MUST be accompanied by the 'Set-proxy' response
115
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127	header. The client or proxy will parse the 'Set-proxy' header to
128	determine which proxy to use, how long to use it, and for which URLs
129	to use it.
130
131	1.3 506 Redirection Failed
132
133	The 506 response is returned when a redirection fails or is refused
134	by a proxy or client. If the redirection response included a body,
135	then it SHOULD be included in the 506 response.
136
137	2.0 Headers
138
139	2.1 'Set-proxy' Response Header
140
141	The 'Set-proxy' header is defined as:
142
143	Set-proxy: "Set-proxy" ":" 1(
144	action #(parameters)
145	)
146
147	parameters = #( ( "scope" "=" scopePattern ) \|
148	( proxyURI "=" URI ) \|
149	lifetime )
150
151	lifetime = ( "seconds" "=" integer )
152	\| ( "hits" "=" integer )
153
154	action = ( "DIRECT"
155	\| "IPL"
156	\| "SET" )
157	) ";"
158
159	scopePattern = "*" \| "-" \| URIpattern
160
161	An example header:
162	Set-proxy: SET ; proxyURI = "http://proxy.me.com:8080/",
163	scope="http://", seconds=5
164
165	action
166
167	The first item, "action" specifies the type or mode of the change.
168	Possible modes are:
169
170
171	DIRECT
172	Attempt to connect directly, with no proxy
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187	IPL
188	Initial Program Load, the client or proxy should attempt to revert
189	back to its default or initial proxy setting. This is meant to
190	instruct a client to re-fetch its proxy configuration, or PAC file.
191	When set, the accompanying scope field MUST be "*" A client receiv-
192	ing this response SHOULD prompt the user for confirmation.
193
194
195	If accompanied by a 'proxyURI' parameter, a proxy or client MAY use
196	the value as a URL containing a configuration to retrieve. If a
197	client does so, it MUST prompt the user for confirmation.
198
199
200	SET
201	Set to parameter "proxyURI". The client should use the URL speci-
202	fied for "proxyURI" as the proxy. If the SET mode is specified, the
203	parameter, "proxyURI", MUST be present.
204
205	Scope
206
207	Scope refers to a URI prefix pattern that specifies which URIs are
208	subject to this header setting. URIs should be matched against the
209	scope with this rule :
210
211	The scope "*" means all requests
212	The scope "-" means this EXACT URL ONLY
213
214	Otherwise, the URL is compared with the scope after it is:
215
216
217	* truncated to the length of the scope
218
219
220	* domain names are set in reverse order.
221
222	For example:
223
224	scope = "http://com.foo.www/services/"
225
226	URL "http://www.foo.com/services/express/2day.html"
227	transformed: "http://com.foo.www/services/express/" (MATCH)
228
229	Another example:
230
231	scope = "http://com.ups/" URL "http://www.ups.com/" (MATCH)
232	URL "http://www.fedex.com/" (FAIL)
233
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246
247	The lifetime parameter specifies how long the specified proxy
248	should be used. If lifetime is specified as "seconds" then the
249	proxy setting remains in effect for 'integer' seconds. If lifetime
250	is specified in 'hits' then the proxy setting remains in effect for
251	'integer' transactions.
252
253	2.2 Location Header
254
255
256	In the original HTTP/1.1 spec, the 'Location' header was used to
257	indicate the proxy setting. Its use is DEPRECATED by the 'Set-
258	proxy' header in the context of a 305 response. All new implementa-
259	tions MUST send the Set-proxy header. Implementations MAY send the
260	'Location' header so as to allow backward compatibility.
261
262
263	If the 'Location' header is specified, it should contain a URI of
264	the proxy. If the Set-proxy header is not specified, the client
265	should use this proxy for just one request, and only for the origi-
266	nally requested exact URL.
267
268	3.0 Methods
269
270
271	A client or proxy receiving a 305 or 306, should use the OPTIONS
272	method to determine if the server or proxy it is talking to actu-
273	ally is an HTTP/1.1 server supporting 305 and 306 responses.
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305
306
307	4.0 Operational Constraints
308
309
310	* Both the 305 and 306 response codes are HOP by HOP. A proxy server
311	MUST not forward a 305 or 306 respose code (unless it generated the
312	306).
313
314
315	* A webserver MUST NOT send a 306 response under any circumstances
316
317
318	* A proxy server MUST NOT generate a 305 response.
319
320
321	* A client or proxy SHOULD NOT accept a 306 from a proxy that it
322	learned of via a 305 response code.
323
324
325	* A client or proxy MAY maintain state and allow a lifetime to extend
326	beyond a session or restart.
327
328
329	* A 'Set-proxy: IPL' SHOULD override any previous 'Set-proxy' header.
330
331
332	* A 305 or 306 response MAY contain a body containing an explanation
333	of the redirect for clients which do not understand the redirect
334
335
336	* In the absence of any parameter, the following defaults should be
337	used:
338
339	lifetime = this transaction only
340	scope = this exact URL only
341
342
343	* When receiving a 305 response, the client or proxy will enforce the
344	following rule with respect to the scope.
345
346	The scope specified must be more restrictive than the transformed
347	URL in question.
348
349	Example: (in order of restrictiveness)
350
351	http://com.ups.www/services/express/1day.html ( most restrictive)
352	http://com.ups.www/ (all requests for only www.ups.com )
353	http://com.ups ( all requests for ups.com )
354	http:// ( for all http requests )
355
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367	* ( all requests )
368
369	If the scope returned with a 305 response is less restrictive than
370	the requested URL, the client MUST prompt the user for confirmation
371	before accepting the new proxy setting.
372
373
374	* Since HTTP/1.0 proxies may unknowingly forward a 305 or 306
375	response code that was generated maliciously or in good faith, the
376	client must attempt to ascertain if the proxy with which it is
377	directly communicating is HTTP/1.1 and if it supports the 'Set-
378	proxy' header. To determine this, the client or proxy should use
379	the OPTIONS method to make a request check for this feature.
380
381
382	Security Considerations
383
384	Great care should be taken when implementing client side actions
385	based on the 305 or 306. Since older proxies may unknowingly for-
386	ward either of these reponses, clients should be prepared to check
387	the validity.
388
389
390	* Please read the section 'Operational Constraints'
391
392
393	* A client or proxy MUST NOT accept a 305 response from a proxy.
394
395
396	* A client or proxy MUST NOT accept a 306 response from an origin
397	server.
398
399
400	* When receiving a 306 response from a proxy, the client MUST verify
401	that the proxy supports the 306 response with a METHODS request.
402
403	5.0 Notes
404
405	Further specification is needed to define exactly how to use
406	METHODs, or another mechanism to determin if set-proxy is sup-
407	ported.
408
409	Author's Address
410
411	Josh Cohen
412	Netscape Communications Corporation
413	501 E. Middlefield Rd
414	Mountain View, CA 94043
415
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427	Phone (415) 937-4157
428	EMail: josh@netscape.com
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