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<front> <front>
<title abbrev="Proxy-Status Header">The Proxy-Status HTTP Response Header Fi eld</title> <title abbrev="Proxy-Status Header">The Proxy-Status HTTP Response Header Fi eld</title>
<seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-proxy-status-08" /> <seriesInfo name="RFC" value="9209"/>
<author initials="M." surname="Nottingham" fullname="Mark Nottingham"> <author initials="M." surname="Nottingham" fullname="Mark Nottingham">
<organization>Fastly</organization> <organization>Fastly</organization>
<address> <address>
<postal> <postal>
<postalLine>Prahran</postalLine> <postalLine>Prahran</postalLine>
<postalLine>Australia</postalLine> <postalLine>Australia</postalLine>
</postal> </postal>
<email>mnot@mnot.net</email> <email>mnot@mnot.net</email>
<uri>https://www.mnot.net/</uri> <uri>https://www.mnot.net/</uri>
</address> </address>
</author> </author>
<author initials="P." surname="Sikora" fullname="Piotr Sikora"> <author initials="P." surname="Sikora" fullname="Piotr Sikora">
<organization>Google</organization> <organization>Google</organization>
<address> <address>
<email>piotrsikora@google.com</email> <email>piotrsikora@google.com</email>
</address> </address>
</author> </author>
<date/> <date year="2022" month="June" />
<area>Applications and Real-Time</area> <area>Applications and Real-Time</area>
<workgroup>HTTP</workgroup> <workgroup>HTTP</workgroup>
<keyword>Internet-Draft</keyword> <keyword>proxy</keyword>
<keyword>intermediary</keyword>
<keyword>reverse proxy</keyword>
<abstract> <abstract>
<t>This document defines the Proxy-Status HTTP field to convey the details of intermediary response handling, including generated errors.</t> <t>This document defines the Proxy-Status HTTP response field to convey th e details of an intermediary's response handling, including generated errors.</t >
</abstract> </abstract>
<note>
<name>Note to Readers</name>
<t><em>RFC EDITOR: please remove this section before publication</em></t>
<t>Discussion of this draft takes place on the HTTP working group mailing
list (ietf-http-wg@w3.org), which is archived at <eref target="https://lists.w3.
org/Archives/Public/ietf-http-wg/">https://lists.w3.org/Archives/Public/ietf-htt
p-wg/</eref>.</t>
<t>Working Group information can be found at <eref target="https://httpwg.
org/">https://httpwg.org/</eref>; source code and issues list for this draft can
be found at <eref target="https://github.com/httpwg/http-extensions/labels/prox
y-status">https://github.com/httpwg/http-extensions/labels/proxy-status</eref>.<
/t>
</note>
</front> </front>
<middle> <middle>
<section anchor="introduction" numbered="true" toc="default"> <section anchor="introduction" numbered="true" toc="default">
<name>Introduction</name> <name>Introduction</name>
<t>HTTP intermediaries (see <xref section="3.7" sectionFormat="of" target= "HTTP" format="default"/>) -- including both forward proxies and gateways (also known as "reverse proxies") -- have become an increasingly significant part of H TTP deployments. In particular, reverse proxies and Content Delivery Networks (C DNs) form part of the critical infrastructure of many Web sites.</t> <t>HTTP intermediaries (see <xref section="3.7" sectionFormat="of" target= "HTTP" format="default"/>) -- including both forward proxies and gateways (also known as "reverse proxies") -- have become an increasingly significant part of H TTP deployments. In particular, reverse proxies and content delivery networks (C DNs) form part of the critical infrastructure of many websites.</t>
<t>Typically, HTTP intermediaries forward requests towards the origin serv er (inbound) and then forward their responses back to clients (outbound). Howeve r, if an error occurs before a response is obtained from an inbound server, the response is often generated by the intermediary itself.</t> <t>Typically, HTTP intermediaries forward requests towards the origin serv er (inbound) and then forward their responses back to clients (outbound). Howeve r, if an error occurs before a response is obtained from an inbound server, the response is often generated by the intermediary itself.</t>
<t>HTTP accommodates these types of errors with a few status codes; for ex <t>HTTP accommodates these types of errors with a few status codes -- for
ample, 502 Bad Gateway and 504 Gateway Timeout. However, experience has shown th example, 502 (Bad Gateway) and 504 (Gateway Timeout). However, experience has sh
at more information is necessary to aid debugging and communicate what's happene own that more information is necessary to aid debugging and communicate what's h
d to the client. Additionally, intermediaries sometimes want to convey additiona appened to the client. Additionally, intermediaries sometimes want to convey add
l information about their handling of a response, even if they did not generate itional information about their handling of a response, even if they did not gen
it.</t> erate it.</t>
<t>To enable these uses, <xref target="header" format="default"/> defines <t>To enable these uses, <xref target="header" format="default"/> defines
a new HTTP response field to allow intermediaries to convey details of their han a new HTTP response field to allow intermediaries to convey details of their han
dling of a response. <xref target="params" format="default"/> enumerates the inf dling of a response. <xref target="params" format="default"/> enumerates the inf
ormation that can be added to the field by intermediaries, which can be extended ormation that can be added to the field by intermediaries, which can be extended
as per <xref target="register-param" format="default"/>. <xref target="error-ty per <xref target="register-param" format="default"/>. <xref target="error-types
pes" format="default"/> defines a set of error types for use when a proxy encoun " format="default"/> defines a set of error types for use when a proxy encounter
ters an issue when obtaining a response for the request; these can likewise be e s an issue when obtaining a response for the request; these can likewise be exte
xtended as per <xref target="register-error" format="default"/>.</t> nded per <xref target="register-error" format="default"/>.</t>
<section anchor="notational-conventions" numbered="true" toc="default"> <section anchor="notational-conventions" numbered="true" toc="default">
<name>Notational Conventions</name> <name>Notational Conventions</name>
<t>The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", " <t>
SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" i The key words "<bcp14>MUST</bcp14>", "<bcp14>MUST NOT</bcp14>", "<bcp14>REQU
n this document are to be interpreted as described in BCP 14 <xref target="RFC21 IRED</bcp14>", "<bcp14>SHALL</bcp14>", "<bcp14>SHALL
19" format="default"/> <xref target="RFC8174" format="default"/> when, and only NOT</bcp14>", "<bcp14>SHOULD</bcp14>", "<bcp14>SHOULD NOT</bcp14>", "<bcp14>
when, they appear in all capitals, as shown here.</t> RECOMMENDED</bcp14>", "<bcp14>NOT RECOMMENDED</bcp14>",
<t>This specification uses Structured Fields <xref target="STRUCTURED-FI "<bcp14>MAY</bcp14>", and "<bcp14>OPTIONAL</bcp14>" in this document are to
ELDS" format="default"/> to specify syntax and parsing, and ABNF <xref target="R be interpreted as
FC5234" format="default"/> as a shorthand for that syntax. The terms sf-list, sf described in BCP&nbsp;14 <xref target="RFC2119"/> <xref target="RFC8174"/>
-item, sf-string, sf-token, sf-integer and key refer to the structured types def when, and only when, they appear in all capitals, as shown here.
ined therein.</t> </t>
<t>This document uses the following terminology from <xref target="STRUC
TURED-FIELDS" section="3" sectionFormat="of" format="default"/> to specify synta
x and parsing: List, String, Token, Integer, and Byte Sequence.</t>
<t>Note that in this specification, "proxy" is used to indicate both for ward and reverse proxies, otherwise known as gateways. "Next hop" indicates the connection in the direction leading to the origin server for the request.</t> <t>Note that in this specification, "proxy" is used to indicate both for ward and reverse proxies, otherwise known as gateways. "Next hop" indicates the connection in the direction leading to the origin server for the request.</t>
</section> </section>
</section> </section>
<section anchor="header" numbered="true" toc="default"> <section anchor="header" numbered="true" toc="default">
<name>The Proxy-Status HTTP Field</name> <name>The Proxy-Status HTTP Field</name>
<t>The Proxy-Status HTTP response field allows an intermediary to convey a <t>The Proxy-Status HTTP response field allows an intermediary to convey a
dditional information about its handling of a response and its associated reques dditional information about its handling of a response and its associated reques
t. The syntax of this header field conforms to <xref target="STRUCTURED-FIELDS" t.</t>
format="default"/>.</t> <t>Its value is a List (see <xref section="3.1" sectionFormat="of" target=
<t>It is a List (<xref section="3.1" sectionFormat="comma" target="STRUCTU "STRUCTURED-FIELDS" format="default"/>). Each member of the List represents an i
RED-FIELDS" format="default"/>):</t> ntermediary that has handled the response. The first member represents the inter
<sourcecode type="abnf"><![CDATA[ mediary closest to the origin server, and the last member represents the interme
Proxy-Status = sf-list diary closest to the user agent.</t>
]]></sourcecode>
<t>Each member of the list represents an intermediary that has handled the
response. The first member of the list represents the intermediary closest to t
he origin server, and the last member of the list represents the intermediary cl
osest to the user agent.</t>
<t>For example:</t> <t>For example:</t>
<sourcecode type="http-message"><![CDATA[ <sourcecode type="http-message"><![CDATA[
Proxy-Status: revproxy1.example.net, ExampleCDN Proxy-Status: revproxy1.example.net, ExampleCDN
]]></sourcecode> ]]></sourcecode>
<t>indicates that this response was handled first by revproxy1.example.net (a reverse proxy adjacent to the origin server) and then ExampleCDN.</t> <t>indicates that this response was handled first by revproxy1.example.net (a reverse proxy adjacent to the origin server) and then ExampleCDN.</t>
<t>Intermediaries determine when it is appropriate to add the Proxy-Status <t>Intermediaries determine when it is appropriate to add the Proxy-Status
field to a response. Some might decide to append to it to all responses, wherea field to a response. Some might decide to append it to all responses, whereas o
s others might only do so when specifically configured to, or when the request c thers might only do so when specifically configured to or when the request conta
ontains a header field that activates a debugging mode.</t> ins a header field that activates a debugging mode.</t>
<t>Each member of the list identifies the intermediary that inserted the v <t>Each member of the List identifies the intermediary that inserted the v
alue, and MUST have a type of either sf-string or sf-token. Depending on the dep alue and <bcp14>MUST</bcp14> have a type of either String or Token. Depending on
loyment, this might be a service name (but not a software or hardware product na the deployment, this might be a service name (but not a software or hardware pr
me; e.g., "Example CDN"is appropriate, but "ExampleProxy" is not, because it doe oduct name; e.g., "ExampleCDN" is appropriate, but "ExampleProxy" is not because
sn't identify the deployment), a hostname ("proxy-3.example.com"), an IP address it doesn't identify the deployment), a hostname ("proxy-3.example.com"), an IP
, or a generated string.</t> address, or a generated string.</t>
<t>Parameters on each member (as per <xref section="3.1.2" sectionFormat=" <t>Parameters of each member (per <xref section="3.1.2" sectionFormat="of"
of" target="STRUCTURED-FIELDS" format="default"/>) convey additional information target="STRUCTURED-FIELDS" format="default"/>) convey additional information ab
about that intermediary's handling of the response and its associated request; out that intermediary's handling of the response and its associated request; see
see <xref target="params" format="default"/>. While all of these parameters are <xref target="params" format="default"/>. While all of these parameters are <bc
OPTIONAL, intermediaries are encouraged to provide as much information as possib p14>OPTIONAL</bcp14>, intermediaries are encouraged to provide as much informati
le (but see <xref target="security" format="default"/> for security consideratio on as possible (but see <xref target="security" format="default"/> for security
ns in doing so).</t> considerations in doing so).</t>
<t>When adding a value to the Proxy-Status field, intermediaries SHOULD pr <t>When adding a value to the Proxy-Status field, intermediaries <bcp14>SH
eserve the existing members of the field to allow debugging of the entire chain OULD</bcp14> preserve the existing members of the field to allow debugging of th
of intermediaries handling the request, unless explicitly configured to remove t e entire chain of intermediaries handling the request unless explicitly configur
hem (e.g., to prevent internal network details from leaking; see <xref target="s ed to remove them (e.g., to prevent internal network details from leaking; see <
ecurity" format="default"/>).</t> xref target="security" format="default"/>).</t>
<t>Origin servers MUST NOT generate the Proxy-Status field.</t> <t>Origin servers <bcp14>MUST NOT</bcp14> generate the Proxy-Status field.
<t>Proxy-Status MAY be sent as a HTTP trailer field. For example, if an in </t>
termediary is streaming a response and the inbound connection suddenly terminate <t>Proxy-Status <bcp14>MAY</bcp14> be sent as an HTTP trailer field. For e
s, Proxy-Status can only be appended to the trailer section of the outbound mess xample, if an intermediary is streaming a response and the inbound connection su
age, since the header section has already been sent. However, because it might b ddenly terminates, Proxy-Status can only be appended to the trailer section of t
e silently discarded along the path to the user agent (as is the case for all tr he outbound message since the header section has already been sent. However, bec
ailer fields; see <xref section="6.5" sectionFormat="of" target="HTTP" format="d ause it might be silently discarded along the path to the user agent (as is the
efault"/>), Proxy-Status SHOULD NOT be sent as a trailer field unless it is not case for all trailer fields; see <xref section="6.5" sectionFormat="of" target="
possible to send it in the header section.</t> HTTP" format="default"/>), Proxy-Status <bcp14>SHOULD NOT</bcp14> be sent as a t
<t>To allow recipients to reconstruct the relative ordering of Proxy-Statu railer field unless it is not possible to send it in the header section.</t>
s members conveyed in trailer fields with those conveyed in header fields, an in <t>To allow recipients to reconstruct the relative ordering of Proxy-Statu
termediary MUST NOT send Proxy-Status as a trailer field unless it has also gene s members conveyed in trailer fields with those conveyed in header fields, an in
rated a Proxy-Status header field with the same member (although potentially dif termediary <bcp14>MUST NOT</bcp14> send Proxy-Status as a trailer field unless i
ferent parameters) in that message.</t> t has also generated a Proxy-Status header field with the same member (although
potentially different parameters) in that message.</t>
<t>For example, a proxy identified as 'ThisProxy' that receives a response bearing a header field:</t> <t>For example, a proxy identified as 'ThisProxy' that receives a response bearing a header field:</t>
<sourcecode type="http-message"><![CDATA[ <sourcecode type="http-message"><![CDATA[
Proxy-Status: SomeOtherProxy Proxy-Status: SomeOtherProxy
]]></sourcecode> ]]></sourcecode>
<t>would add its own entry to the header field:</t> <t>would add its own entry to the header field:</t>
<sourcecode type="http-message"><![CDATA[ <sourcecode type="http-message"><![CDATA[
Proxy-Status: SomeOtherProxy, ThisProxy Proxy-Status: SomeOtherProxy, ThisProxy
]]></sourcecode> ]]></sourcecode>
<t>thus allowing it to append a trailer field:</t> <t>thus allowing it to append a trailer field:</t>
<sourcecode type="http-message"><![CDATA[ <sourcecode type="http-message"><![CDATA[
Proxy-Status: ThisProxy; error=read_timeout Proxy-Status: ThisProxy; error=read_timeout
]]></sourcecode> ]]></sourcecode>
<t>... which would thereby allow a downstream recipient to understand that <t>which would thereby allow a downstream recipient to understand that pro
processing by 'SomeOtherProxy' occurred before 'ThisProxy'.</t> cessing by 'SomeOtherProxy' occurred before 'ThisProxy'.</t>
<t>A client MAY promote the Proxy-Status trailer field into a header field <t>A client <bcp14>MAY</bcp14> promote the Proxy-Status trailer field into
by following these steps:</t> a header field by following these steps:</t>
<ol spacing="normal" type="1"><li> <ol spacing="normal" type="1"><li>
<t>For each member trailer_member of the Proxy-Status trailer field va lue: <t>For each member trailer_member of the Proxy-Status trailer field va lue:
</t> </t>
<ol spacing="normal" type="1"><li>Let header_member be the first (left -most) value of the Proxy-Status header field value, comparing the sf-token or s f-string character-by-character and without consideration of parameters.</li> <ol spacing="normal" type="1"><li>Let header_member be the first (left most) value of the Proxy-Status header field value, comparing the String or Toke n character by character without consideration of parameters.</li>
<li>If no matching header_member is found, continue processing the n ext trailer_member.</li> <li>If no matching header_member is found, continue processing the n ext trailer_member.</li>
<li>Replace header_member with trailer_member in its entirety, inclu ding any parameters.</li> <li>Replace header_member with trailer_member in its entirety, inclu ding any parameters.</li>
</ol> </ol>
</li> </li>
<li>Remove the Proxy-Status trailer field, if empty.</li> <li>Remove the Proxy-Status trailer field if empty.</li>
</ol> </ol>
<section anchor="params" numbered="true" toc="default"> <section anchor="params" numbered="true" toc="default">
<name>Proxy-Status Parameters</name> <name>Proxy-Status Parameters</name>
<t>This section lists parameters that can be used on the members of the Proxy-Status field. Unrecognised parameters MUST be ignored.</t> <t>This section lists parameters that can be used on the members of the Proxy-Status field. Unrecognised parameters <bcp14>MUST</bcp14> be ignored.</t>
<section anchor="error" numbered="true" toc="default"> <section anchor="error" numbered="true" toc="default">
<name>error</name> <name>error</name>
<t>The <tt>error</tt> parameter's value is an sf-token that is a Proxy <t>The <tt>error</tt> parameter's value is a Token that is a proxy err
Error Type. When present, it indicates that the intermediary encountered an iss or type. When present, it indicates that the intermediary encountered an issue w
ue when obtaining this response.</t> hen obtaining this response.</t>
<t>The presence of some Proxy Error Types indicates that the response <t>The presence of some proxy error types indicates that the response
was generated by the intermediary itself, rather than being forwarded from the o was generated by the intermediary itself, rather than being forwarded from the o
rigin server. This is the case when, for example, the origin server can't be con rigin server. This is the case when, for example, the origin server can't be con
tacted, so the proxy has to create its own response.</t> tacted, so the proxy has to create its own response.</t>
<t>Other Proxy Error Types can be added to (potentially partial) respo <t>Other proxy error types can be added to (potentially partial) respo
nses that were generated by the nses that were generated by the
origin server or some other inbound server. For example, if the forward connecti on abruptly closes, an intermediary might add Proxy-Status with an appropriate e rror as a trailer field.</t> origin server or some other inbound server. For example, if the forward connecti on abruptly closes, an intermediary might add Proxy-Status with an appropriate e rror as a trailer field.</t>
<t>Proxy Error Types that are registered with a 'Response only generat <t>Proxy error types that are registered with a 'Response only generat
ed by intermediaries' value of 'true' indicate that they can only occur on respo ed by intermediaries' value of 'true' indicate that they can only occur in respo
nses generated by the intermediary. If the value is 'false', the response might nses generated by the intermediary. If the value is 'false', the response might
be generated by the intermediary or an inbound server.</t> be generated by the intermediary or an inbound server.</t>
<t><xref target="error-types" format="default"/> lists the Proxy Error <t><xref target="error-types" format="default"/> lists the proxy error
Types defined in this document; new ones can be defined using the procedure out types defined in this document; new ones can be defined using the procedure out
lined in <xref target="register-error" format="default"/>.</t> lined in <xref target="register-error" format="default"/>.</t>
<t>For example:</t> <t>For example:</t>
<sourcecode type="http-message"><![CDATA[ <sourcecode type="http-message"><![CDATA[
HTTP/1.1 504 Gateway Timeout HTTP/1.1 504 Gateway Timeout
Proxy-Status: ExampleCDN; error=connection_timeout Proxy-Status: ExampleCDN; error=connection_timeout
]]></sourcecode> ]]></sourcecode>
<t>indicates that this 504 response was generated by ExampleCDN, due t o a connection timeout when going forward.</t> <t>indicates that this 504 response was generated by ExampleCDN due to a connection timeout when going forward.</t>
<t>Or:</t> <t>Or:</t>
<sourcecode type="http-message"><![CDATA[ <sourcecode type="http-message"><![CDATA[
HTTP/1.1 429 Too Many Requests HTTP/1.1 429 Too Many Requests
Proxy-Status: r34.example.net; error=http_request_error, ExampleCDN Proxy-Status: r34.example.net; error=http_request_error, ExampleCDN
]]></sourcecode> ]]></sourcecode>
<t>indicates that this 429 Too Many Requests response was generated by <t>indicates that this 429 (Too Many Requests) response was generated
r34.example.net, not the CDN or the origin.</t> by r34.example.net, not the CDN or the origin.</t>
<t>When sending the error parameter, the most specific Proxy Error Typ <t>When sending the error parameter, the most specific proxy error typ
e SHOULD be sent, provided that it accurately represents the error condition. If e <bcp14>SHOULD</bcp14> be sent, provided that it accurately represents the erro
an appropriate Proxy Error Type is not defined, there are a number of generic e r condition. If an appropriate proxy error type is not defined, there are a numb
rror types (e.g., proxy_internal_error, http_protocol_error) that can be used. I er of generic error types (e.g., proxy_internal_error, http_protocol_error) that
f they are not suitable, consider registering a new Proxy Error Type (see <xref can be used. If they are not suitable, consider registering a new proxy error t
target="register-error" format="default"/>).</t> ype (see <xref target="register-error" format="default"/>).</t>
<t>Each Proxy Error Type has a Recommended HTTP Status Code. When gene <t>Each proxy error type has a recommended HTTP status code. When gene
rating a HTTP response containing <tt>error</tt>, its HTTP status code SHOULD be rating an HTTP response containing the <tt>error</tt>, its HTTP status code <bcp
set to the Recommended HTTP Status Code. However, there may be circumstances (e 14>SHOULD</bcp14> be set to the recommended HTTP status code. However, there may
.g., for backwards compatibility with previous behaviours, a status code has alr be circumstances (e.g., for backwards compatibility with previous behaviours, a
eady been sent) when another status code might be used.</t> status code has already been sent) when another status code might be used.</t>
<t>Proxy Error Types can also define any number of extra parameters fo <t>Proxy error types can also define any number of extra parameters fo
r use with that type. Their use, like all parameters, is optional. As a result, r use with that type. Their use, like all parameters, is optional. As a result,
if an extra parameter is used with a Proxy Error Type for which it is not define if an extra parameter is used with a proxy error type for which it is not define
d, it will be ignored.</t> d, it will be ignored.</t>
</section> </section>
<section anchor="next-hop" numbered="true" toc="default"> <section anchor="next-hop" numbered="true" toc="default">
<name>next-hop</name> <name>next-hop</name>
<t>The <tt>next-hop</tt> parameter's value is an sf-string or sf-token that identifies the intermediary or origin server selected (and used, if contac ted) to obtain this response. It might be a hostname, IP address, or alias.</t> <t>The <tt>next-hop</tt> parameter's value is a String or Token that i dentifies the intermediary or origin server selected (and used, if contacted) to obtain this response. It might be a hostname, IP address, or alias.</t>
<t>For example:</t> <t>For example:</t>
<sourcecode type="http-message"><![CDATA[ <sourcecode type="http-message"><![CDATA[
Proxy-Status: cdn.example.org; next-hop=backend.example.org:8001 Proxy-Status: cdn.example.org; next-hop=backend.example.org:8001
]]></sourcecode> ]]></sourcecode>
<t>indicates that cdn.example.org used backend.example.org:8001 as the next hop for this request.</t> <t>indicates that cdn.example.org used backend.example.org:8001 as the next hop for this request.</t>
</section> </section>
<section anchor="next-protocol" numbered="true" toc="default"> <section anchor="next-protocol" numbered="true" toc="default">
<name>next-protocol</name> <name>next-protocol</name>
<t>The <tt>next-protocol</tt> parameter's value indicates the ALPN pro <t>The <tt>next-protocol</tt> parameter's value indicates the Applicat
tocol identifier <xref target="RFC7301" format="default"/> of the protocol used ion-Layer Protocol Negotiation (ALPN) protocol identifier <xref target="RFC7301"
by the intermediary to connect to the next hop when obtaining this response.</t> format="default"/> of the protocol used by the intermediary to connect to the n
<t>The value MUST be either an sf-token or sf-binary, representing a T ext hop when obtaining this response.</t>
LS Application-Layer Protocol Negotiation (ALPN) Protocol ID (see <eref target=" <t>The value <bcp14>MUST</bcp14> be either a Token or Byte Sequence rep
https://www.iana.org/assignments/tls-extensiontype-values/tls-extensiontype-valu resenting a TLS ALPN Protocol ID (see <eref brackets="angle" target="https://www
es.xhtml#alpn-protocol-ids">https://www.iana.org/assignments/tls-extensiontype-v .iana.org/assignments/tls-extensiontype-values#alpn-protocol-ids"/>). If the pro
alues/tls-extensiontype-values.xhtml#alpn-protocol-ids</eref>). If the protocol tocol identifier is able to be expressed as a Token using ASCII encoding, that f
identifier is able to be expressed as an sf-token using ASCII encoding, that for orm <bcp14>MUST</bcp14> be used.</t>
m MUST be used.</t>
<t>For example:</t> <t>For example:</t>
<sourcecode type="http-message"><![CDATA[ <sourcecode type="http-message"><![CDATA[
Proxy-Status: "proxy.example.org"; next-protocol=h2 Proxy-Status: "proxy.example.org"; next-protocol=h2
]]></sourcecode> ]]></sourcecode>
<t>Note that the APLN identifier is being used here to identify the pr otocol in use; it may or may not have been actually used in the protocol negotia tion.</t> <t>Note that the ALPN identifier is being used here to identify the pr otocol in use; it may or may not have been actually used in the protocol negotia tion.</t>
</section> </section>
<section anchor="received-status" numbered="true" toc="default"> <section anchor="received-status" numbered="true" toc="default">
<name>received-status</name> <name>received-status</name>
<t>The <tt>received-status</tt> parameter's value indicates the HTTP s <t>The <tt>received-status</tt> parameter's value indicates the HTTP s
tatus code that the intermediary received from the next hop server when obtainin tatus code that the intermediary received from the next-hop server when obtainin
g this response.</t> g this response.</t>
<t>The value MUST be an sf-integer.</t> <t>The value <bcp14>MUST</bcp14> be an Integer.</t>
<t>For example:</t> <t>For example:</t>
<sourcecode type="http-message"><![CDATA[ <sourcecode type="http-message"><![CDATA[
Proxy-Status: ExampleCDN; received-status=200 Proxy-Status: ExampleCDN; received-status=200
]]></sourcecode> ]]></sourcecode>
</section> </section>
<section anchor="details" numbered="true" toc="default"> <section anchor="details" numbered="true" toc="default">
<name>details</name> <name>details</name>
<t>The <tt>details</tt> parameter's value is an sf-string containing a dditional information not captured anywhere else. This can include implementatio n-specific or deployment-specific information.</t> <t>The <tt>details</tt> parameter's value is a String containing addit ional information not captured anywhere else. This can include implementation-sp ecific or deployment-specific information.</t>
<t>For example:</t> <t>For example:</t>
<sourcecode type="http-message"><![CDATA[ <sourcecode type="http-message"><![CDATA[
Proxy-Status: proxy.example.net; error="http_protocol_error"; Proxy-Status: proxy.example.net; error="http_protocol_error";
details="Malformed response header: space before colon" details="Malformed response header: space before colon"
]]></sourcecode> ]]></sourcecode>
</section> </section>
</section> </section>
<section anchor="register-param" numbered="true" toc="default"> <section anchor="register-param" numbered="true" toc="default">
<name>Defining New Proxy-Status Parameters</name> <name>Defining New Proxy-Status Parameters</name>
<t>New Proxy-Status Parameters can be defined by registering them in the <t>New Proxy-Status parameters can be defined by registering them in the
HTTP Proxy-Status Parameters registry.</t> "HTTP Proxy-Status Parameters" registry.</t>
<t>Registration requests are reviewed and approved by Expert Review, as <t>Registration requests are reviewed and approved by Expert Review, per
per <xref section="4.5" sectionFormat="comma" target="RFC8126" format="default"/ <xref section="4.5" sectionFormat="comma" target="RFC8126" format="default"/>.
>. A specification document is appreciated, but not required.</t> A specification document is appreciated but not required.</t>
<t>The Expert(s) should consider the following factors when evaluating r <t>The expert(s) should consider the following factors when evaluating r
equests:</t> equests:</t>
<ul spacing="normal"> <ul spacing="normal">
<li>Community feedback</li> <li>Community feedback</li>
<li>If the value is sufficiently well-defined</li> <li>If the value is sufficiently well defined</li>
<li>Generic parameters are preferred over vendor-specific, application <li>Generic parameters are preferred over vendor-specific, application
-specific or deployment-specific values. If a generic value cannot be agreed upo -specific, or deployment-specific values. If a generic value cannot be agreed up
n in the community, the parameter's name should be correspondingly specific (e.g on in the community, the parameter's name should be correspondingly specific (e.
., with a prefix that identifies the vendor, application or deployment).</li> g., with a prefix that identifies the vendor, application, or deployment).</li>
<li>Parameter names should not conflict with registered extra paramete <li>Parameter names should not conflict with registered extra paramete
rs in the Proxy Error Type Registry.</li> rs in the "HTTP Proxy Error Types" registry.</li>
</ul> </ul>
<t>Registration requests should use the following template:</t> <t>Registration requests should use the following template:</t>
<ul spacing="normal"> <dl>
<li>Name: [a name for the Proxy-Status Parameter that matches key]</li <dt>Name:</dt>
> <dd>[a name for the Proxy-Status parameter that matches key]</dd>
<li>Description: [a description of the parameter semantics and value]< <dt>Description:</dt>
/li> <dd>[a description of the parameter semantics and value]</dd>
<li>Reference: [to a specification defining this parameter; optional]< <dt>Reference:</dt>
/li> <dd>[to a specification defining this parameter; optional]</dd>
</ul> </dl>
<t>See the registry at <eref target="https://iana.org/assignments/http-p <t>See the registry at <eref target="https://www.iana.org/assignments/ht
roxy-status">https://iana.org/assignments/http-proxy-status</eref> for details o tp-proxy-status" brackets="angle"/> for details on where to send registration re
n where to send registration requests.</t> quests.</t>
</section> </section>
<section anchor="error-types" numbered="true" toc="default"> <section anchor="error-types" numbered="true" toc="default">
<name>Proxy Error Types</name> <name>Proxy Error Types</name>
<t>This section lists the Proxy Error Types defined by this document. Se <t>This section lists the proxy error types defined by this document. Se
e <xref target="register-error" format="default"/> for information about definin e <xref target="register-error" format="default"/> for information about definin
g new Proxy Error Types.</t> g new proxy error types.</t>
<t>Note that implementations might not produce all Proxy Error Types. Th <t>Note that implementations might not produce all proxy error types. Th
e set of types below is designed to map to existing states in implementations, a e set of types below is designed to map to existing states in implementations an
nd so may not be applicable to some.</t> d therefore may not be applicable to some.</t>
<section anchor="dns-timeout" numbered="true" toc="default"> <section anchor="dns-timeout" numbered="true" toc="default">
<name>DNS Timeout</name> <name>DNS Timeout</name>
<ul spacing="normal"> <dl>
<li>Name: dns_timeout</li> <dt>Name:</dt>
<li>Description: The intermediary encountered a timeout when trying <dd>dns_timeout</dd>
to find an IP address for the next hop hostname.</li> <dt>Description:</dt>
<li>Extra Parameters: None.</li> <dd>The intermediary encountered a timeout when trying to find an IP
<li>Recommended HTTP status code: 504</li> address for the next-hop hostname.</dd>
<li>Response only generated by intermediaries: true</li> <dt>Extra Parameters:</dt>
<li>Reference: [this document]</li> <dd>None</dd>
</ul> <dt>Recommended HTTP Status Code:</dt>
<dd>504</dd>
<dt>Response Only Generated by Intermediaries:</dt>
<dd>true</dd>
<dt>Reference:</dt>
<dd>RFC 9209</dd>
</dl>
</section> </section>
<section anchor="dns-error" numbered="true" toc="default"> <section anchor="dns-error" numbered="true" toc="default">
<name>DNS Error</name> <name>DNS Error</name>
<ul spacing="normal"> <dl>
<li>Name: dns_error</li> <dt>Name:</dt>
<li>Description: The intermediary encountered a DNS error when tryin <dd>dns_error</dd>
g to find an IP address for the next hop hostname.</li> <dt>Description:</dt>
<li> <dd>The intermediary encountered a DNS error when trying to find an
<t>Extra Parameters: IP address for the next-hop hostname.</dd>
</t> <dt>Extra Parameters:</dt>
<ul spacing="normal"> <dd><t><br/></t>
<li>rcode: A sf-string conveying the DNS RCODE that indicates th <dl>
e error type. See <xref section="3" sectionFormat="comma" target="RFC8499" forma <dt>rcode:</dt>
t="default"/>.</li> <dd> A String conveying the DNS RCODE that indicates the error t
<li>info-code: A sf-integer conveying the Extended DNS Error Cod ype. See <xref section="3" sectionFormat="comma" target="RFC8499" format="defaul
e info-code. See <xref target="RFC8914" format="default"/>.</li> t"/>.</dd>
</ul> <dt>info-code:</dt>
</li> <dd>An Integer conveying the Extended DNS Error Code INFO-CODE.
<li>Recommended HTTP status code: 502</li> See <xref target="RFC8914" format="default"/>.</dd>
<li>Response only generated by intermediaries: true</li> </dl>
<li>Reference: [this document]</li> </dd>
</ul> <dt>Recommended HTTP Status Code:</dt>
<dd>502</dd>
<dt>Response Only Generated by Intermediaries:</dt>
<dd>true</dd>
<dt>Reference:</dt>
<dd>RFC 9209</dd>
</dl>
</section> </section>
<section anchor="destination-not-found" numbered="true" toc="default"> <section anchor="destination-not-found" numbered="true" toc="default">
<name>Destination Not Found</name> <name>Destination Not Found</name>
<ul spacing="normal"> <dl>
<li>Name: destination_not_found</li> <dt>Name:</dt>
<li>Description: The intermediary cannot determine the appropriate n <dd>destination_not_found</dd>
ext hop to use for this request; for example, it may not be configured. Note tha <dt>Description:</dt>
t this error is specific to gateways, which typically require specific configura <dd>The intermediary cannot determine the appropriate next hop to us
tion to identify the "backend" server; forward proxies use in-band information t e for this request; for example, it may not be configured. Note that this error
o identify the origin server.</li> is specific to gateways, which typically require specific configuration to ident
<li>Extra Parameters: None.</li> ify the "backend" server; forward proxies use in-band information to identify th
<li>Recommended HTTP status code: 500</li> e origin server.</dd>
<li>Response only generated by intermediaries: true</li> <dt>Extra Parameters:</dt>
<li>Reference: [this document]</li> <dd>None</dd>
</ul> <dt>Recommended HTTP Status Code:</dt>
<dd>500</dd>
<dt>Response Only Generated by Intermediaries:</dt>
<dd>true</dd>
<dt>Reference:</dt>
<dd>RFC 9209</dd>
</dl>
</section> </section>
<section anchor="destination-unavailable" numbered="true" toc="default"> <section anchor="destination-unavailable" numbered="true" toc="default">
<name>Destination Unavailable</name> <name>Destination Unavailable</name>
<ul spacing="normal"> <dl>
<li>Name: destination_unavailable</li> <dt>Name:</dt>
<li>Description: The intermediary considers the next hop to be unava <dd>destination_unavailable</dd>
ilable; e.g., recent attempts to communicate with it may have failed, or a healt <dt>Description:</dt>
h check may indicate that it is down.</li> <dd>The intermediary considers the next hop to be unavailable; e.g.,
<li>Extra Parameters: None.</li> recent attempts to communicate with it may have failed, or a health check may i
<li>Recommended HTTP status code: 503</li> ndicate that it is down.</dd>
<li>Response only generated by intermediaries: true</li> <dt>Extra Parameters:</dt>
<li>Reference: [this document]</li> <dd>None</dd>
</ul> <dt>Recommended HTTP Status Code:</dt>
<dd>503</dd>
<dt>Response Only Generated by Intermediaries:</dt>
<dd>true</dd>
<dt>Reference:</dt>
<dd>RFC 9209</dd>
</dl>
</section> </section>
<section anchor="destination-ip-prohibited" numbered="true" toc="default "> <section anchor="destination-ip-prohibited" numbered="true" toc="default ">
<name>Destination IP Prohibited</name> <name>Destination IP Prohibited</name>
<ul spacing="normal"> <dl>
<li>Name: destination_ip_prohibited</li> <dt>Name:</dt>
<li>Description: The intermediary is configured to prohibit connecti <dd>destination_ip_prohibited</dd>
ons to the next hop IP address.</li> <dt>Description:</dt>
<li>Extra Parameters: None.</li> <dd>The intermediary is configured to prohibit connections to the ne
<li>Recommended HTTP status code: 502</li> xt-hop IP address.</dd>
<li>Response only generated by intermediaries: true</li> <dt>Extra Parameters:</dt>
<li>Reference: [this document]</li> <dd>None</dd>
</ul> <dt>Recommended HTTP Status Code:</dt>
<dd>502</dd>
<dt>Response Only Generated by Intermediaries:</dt>
<dd>true</dd>
<dt>Reference:</dt>
<dd>RFC 9209</dd>
</dl>
</section> </section>
<section anchor="destination-ip-unroutable" numbered="true" toc="default "> <section anchor="destination-ip-unroutable" numbered="true" toc="default ">
<name>Destination IP Unroutable</name> <name>Destination IP Unroutable</name>
<ul spacing="normal"> <dl>
<li>Name: destination_ip_unroutable</li> <dt>Name:</dt>
<li>Description: The intermediary cannot find a route to the next ho <dd>destination_ip_unroutable</dd>
p IP address.</li> <dt>Description:</dt>
<li>Extra Parameters: None.</li> <dd>The intermediary cannot find a route to the next-hop IP address.
<li>Recommended HTTP status code: 502</li> </dd>
<li>Response only generated by intermediaries: true</li> <dt>Extra Parameters:</dt>
<li>Reference: [this document]</li> <dd>None</dd>
</ul> <dt>Recommended HTTP Status Code:</dt>
<dd>502</dd>
<dt>Response Only Generated by Intermediaries:</dt>
<dd>true</dd>
<dt>Reference:</dt>
<dd>RFC 9209</dd>
</dl>
</section> </section>
<section anchor="connection-refused" numbered="true" toc="default"> <section anchor="connection-refused" numbered="true" toc="default">
<name>Connection Refused</name> <name>Connection Refused</name>
<ul spacing="normal"> <dl>
<li>Name: connection_refused</li> <dt>Name:</dt>
<li>Description: The intermediary's connection to the next hop was r <dd>connection_refused</dd>
efused.</li> <dt>Description:</dt>
<li>Extra Parameters: None.</li> <dd>The intermediary's connection to the next hop was refused.</dd>
<li>Recommended HTTP status code: 502</li> <dt>Extra Parameters:</dt>
<li>Response only generated by intermediaries: true</li> <dd>None</dd>
<li>Reference: [this document]</li> <dt>Recommended HTTP Status Code:</dt>
</ul> <dd>502</dd>
<dt>Response Only Generated by Intermediaries:</dt>
<dd>true</dd>
<dt>Reference:</dt>
<dd>RFC 9209</dd>
</dl>
</section> </section>
<section anchor="connection-terminated" numbered="true" toc="default"> <section anchor="connection-terminated" numbered="true" toc="default">
<name>Connection Terminated</name> <name>Connection Terminated</name>
<ul spacing="normal"> <dl>
<li>Name: connection_terminated</li> <dt>Name:</dt>
<li>Description: The intermediary's connection to the next hop was c <dd>connection_terminated</dd>
losed before complete response was received.</li> <dt>Description:</dt>
<li>Extra Parameters: None.</li> <dd>The intermediary's connection to the next hop was closed before
<li>Recommended HTTP status code: 502</li> a complete response was received.</dd>
<li>Response only generated by intermediaries: false</li> <dt>Extra Parameters:</dt>
<li>Reference: [this document]</li> <dd>None</dd>
</ul> <dt>Recommended HTTP Status Code:</dt>
<dd>502</dd>
<dt>Response Only Generated by Intermediaries:</dt>
<dd>false</dd>
<dt>Reference:</dt>
<dd>RFC 9209</dd>
</dl>
</section> </section>
<section anchor="connection-timeout" numbered="true" toc="default"> <section anchor="connection-timeout" numbered="true" toc="default">
<name>Connection Timeout</name> <name>Connection Timeout</name>
<ul spacing="normal"> <dl>
<li>Name: connection_timeout</li> <dt>Name:</dt>
<li>Description: The intermediary's attempt to open a connection to <dd>connection_timeout</dd>
the next hop timed out.</li> <dt>Description:</dt>
<li>Extra Parameters: None.</li> <dd>The intermediary's attempt to open a connection to the next hop
<li>Recommended HTTP status code: 504</li> timed out.</dd>
<li>Response only generated by intermediaries: true</li> <dt>Extra Parameters:</dt>
<li>Reference: [this document]</li> <dd>None</dd>
</ul> <dt>Recommended HTTP Status Code:</dt>
<dd>504</dd>
<dt>Response Only Generated by Intermediaries:</dt>
<dd>true</dd>
<dt>Reference:</dt>
<dd>RFC 9209</dd>
</dl>
</section> </section>
<section anchor="connection-read-timeout" numbered="true" toc="default"> <section anchor="connection-read-timeout" numbered="true" toc="default">
<name>Connection Read Timeout</name> <name>Connection Read Timeout</name>
<ul spacing="normal"> <dl>
<li>Name: connection_read_timeout</li> <dt>Name:</dt>
<li>Description: The intermediary was expecting data on a connection <dd>connection_read_timeout</dd>
(e.g., part of a response), but did not receive any new data in a configured ti <dt>Description:</dt>
me limit.</li> <dd>The intermediary was expecting data on a connection (e.g., part
<li>Extra Parameters: None.</li> of a response) but did not receive any new data in a configured time limit.</dd>
<li>Recommended HTTP status code: 504</li> <dt>Extra Parameters:</dt>
<li>Response only generated by intermediaries: false</li> <dd>None</dd>
<li>Reference: [this document]</li> <dt>Recommended HTTP Status Code:</dt>
</ul> <dd>504</dd>
<dt>Response Only Generated by Intermediaries:</dt>
<dd>false</dd>
<dt>Reference:</dt>
<dd>RFC 9209</dd>
</dl>
</section> </section>
<section anchor="connection-write-timeout" numbered="true" toc="default" > <section anchor="connection-write-timeout" numbered="true" toc="default" >
<name>Connection Write Timeout</name> <name>Connection Write Timeout</name>
<ul spacing="normal"> <dl>
<li>Name: connection_write_timeout</li> <dt>Name:</dt>
<li>Description: The intermediary was attempting to write data to a <dd>connection_write_timeout</dd>
connection, but was not able to (e.g., because its buffers were full).</li> <dt>Description:</dt>
<li>Extra Parameters: None.</li> <dd>The intermediary was attempting to write data to a connection bu
<li>Recommended HTTP status code: 504</li> t was not able to (e.g., because its buffers were full).</dd>
<li>Response only generated by intermediaries: false</li> <dt>Extra Parameters:</dt>
<li>Reference: [this document]</li> <dd>None</dd>
</ul> <dt>Recommended HTTP Status Code:</dt>
<dd>504</dd>
<dt>Response Only Generated by Intermediaries:</dt>
<dd>false</dd>
<dt>Reference:</dt>
<dd>RFC 9209</dd>
</dl>
</section> </section>
<section anchor="connection-limit-reached" numbered="true" toc="default" > <section anchor="connection-limit-reached" numbered="true" toc="default" >
<name>Connection Limit Reached</name> <name>Connection Limit Reached</name>
<ul spacing="normal"> <dl>
<li>Name: connection_limit_reached</li> <dt>Name:</dt>
<li>Description: The intermediary is configured to limit the number <dd>connection_limit_reached</dd>
of connections it has to the next hop, and that limit has been passed.</li> <dt>Description:</dt>
<li>Extra Parameters: None.</li> <dd>The intermediary is configured to limit the number of connection
<li>Recommended HTTP status code: 503</li> s it has to the next hop, and that limit has been exceeded.</dd>
<li>Response only generated by intermediaries: true</li> <dt>Extra Parameters:</dt>
<li>Reference: [this document]</li> <dd>None</dd>
</ul> <dt>Recommended HTTP Status Code:</dt>
<dd>503</dd>
<dt>Response Only Generated by Intermediaries:</dt>
<dd>true</dd>
<dt>Reference:</dt>
<dd>RFC 9209</dd>
</dl>
</section> </section>
<section anchor="tls-protocol-error" numbered="true" toc="default"> <section anchor="tls-protocol-error" numbered="true" toc="default">
<name>TLS Protocol Error</name> <name>TLS Protocol Error</name>
<ul spacing="normal"> <dl>
<li>Name: tls_protocol_error</li> <dt>Name:</dt>
<li>Description: The intermediary encountered a TLS error when commu <dd>tls_protocol_error</dd>
nicating with the next hop, either during handshake or afterwards.</li> <dt>Description:</dt>
<li>Extra Parameters: None.</li> <dd>The intermediary encountered a TLS error when communicating with
<li>Recommended HTTP status code: 502</li> the next hop, either during the handshake or afterwards.</dd>
<li>Response only generated by intermediaries: false</li> <dt>Extra Parameters:</dt>
<li>Reference: [this document]</li> <dd>None</dd>
<li>Notes: Not appropriate when a TLS alert is received; see tls_ale <dt>Recommended HTTP Status Code:</dt>
rt_received</li> <dd>502</dd>
</ul> <dt>Response Only Generated by Intermediaries:</dt>
<dd>false</dd>
<dt>Reference:</dt>
<dd>RFC 9209</dd>
<dt>Notes:</dt>
<dd>Not appropriate when a TLS alert is received; see tls_alert_rece
ived.</dd>
</dl>
</section> </section>
<section anchor="tls-certificate-error" numbered="true" toc="default"> <section anchor="tls-certificate-error" numbered="true" toc="default">
<name>TLS Certificate Error</name> <name>TLS Certificate Error</name>
<ul spacing="normal"> <dl>
<li>Name: tls_certificate_error</li> <dt>Name:</dt>
<li>Description: The intermediary encountered an error when verifyin <dd>tls_certificate_error</dd>
g the certificate presented by the next hop.</li> <dt>Description:</dt>
<li>Extra Parameters: None.</li> <dd>The intermediary encountered an error when verifying the certifi
<li>Recommended HTTP status code: 502</li> cate presented by the next hop.</dd>
<li>Response only generated by intermediaries: true</li> <dt>Extra Parameters:</dt>
<li>Reference: [this document]</li> <dd>None</dd>
</ul> <dt>Recommended HTTP Status Code:</dt>
<dd>502</dd>
<dt>Response Only Generated by Intermediaries:</dt>
<dd>true</dd>
<dt>Reference:</dt>
<dd>RFC 9209</dd>
</dl>
</section> </section>
<section anchor="tls-alert-received" numbered="true" toc="default"> <section anchor="tls-alert-received" numbered="true" toc="default">
<name>TLS Alert Received</name> <name>TLS Alert Received</name>
<ul spacing="normal"> <dl>
<li>Name: tls_alert_received</li> <dt>Name:</dt>
<li>Description: The intermediary received a TLS alert from the next <dd>tls_alert_received</dd>
hop.</li> <dt>Description:</dt>
<li> <dd>The intermediary received a TLS alert from the next hop.</dd>
<t>Extra Parameters: <dt>Extra Parameters:</dt>
</t> <dd><t><br/></t>
<ul spacing="normal"> <dl>
<li>alert-id: an sf-integer containing the applicable value from <dt>alert-id:</dt>
the TLS Alerts registry. See {!RFC8446}}.</li> <dd>An Integer containing the applicable value from the "TLS Ale
<li>alert-message: an sf-token or sf-string containing the appli rts" registry. See <xref target="TLS" format="default"/>.</dd>
cable description string from the TLS Alerts registry. See <xref target="RFC8446 <dt>alert-message:</dt>
" format="default"/>.</li> <dd>A Token or String containing the applicable description stri
</ul> ng from the "TLS Alerts" registry. See <xref target="TLS" format="default"/>.</d
</li> d>
<li>Recommended HTTP status code: 502</li> </dl>
<li>Response only generated by intermediaries: false</li> </dd>
<li>Reference: [this document]</li> <dt>Recommended HTTP Status Code:</dt>
</ul> <dd>502</dd>
<dt>Response Only Generated by Intermediaries:</dt>
<dd>false</dd>
<dt>Reference:</dt>
<dd>RFC 9209</dd>
</dl>
</section> </section>
<section anchor="http-request-error" numbered="true" toc="default"> <section anchor="http-request-error" numbered="true" toc="default">
<name>HTTP Request Error</name> <name>HTTP Request Error</name>
<ul spacing="normal"> <dl>
<li>Name: http_request_error</li> <dt>Name:</dt>
<li>Description: The intermediary is generating a client (4xx) respo <dd>http_request_error</dd>
nse on the origin's behalf. Applicable status codes include (but are not limited <dt>Description:</dt>
to) 400, 403, 405, 406, 408, 411, 413, 414, 415, 416, 417, 429.</li> <dd>The intermediary is generating a client (4xx) response on the or
<li> igin's behalf. Applicable status codes include (but are not limited to) 400, 403
<t>Extra Parameters: , 405, 406, 408, 411, 413, 414, 415, 416, 417, and 429.</dd>
</t> <dt>Extra Parameters:</dt>
<ul spacing="normal"> <dd><t><br/></t>
<li>status-code: an sf-integer containing the generated status c <dl>
ode.</li> <dt>status-code:</dt>
<li>status-phrase: an sf-string containing the generated status <dd>An Integer containing the generated status code.</dd>
phrase.</li> <dt>status-phrase:</dt>
</ul> <dd>A String containing the generated status phrase.</dd>
</li> </dl>
<li>Recommended HTTP status code: The applicable 4xx status code</li </dd>
> <dt>Recommended HTTP Status Code:</dt>
<li>Response only generated by intermediaries: true</li> <dd>The applicable 4xx status code</dd>
<li>Reference: [this document]</li> <dt>Response Only Generated by Intermediaries:</dt>
<li>Notes: This type helps distinguish between responses generated b <dd>true</dd>
y intermediaries from those generated by the origin.</li> <dt>Reference:</dt>
</ul> <dd>RFC 9209</dd>
<dt>Notes:</dt>
<dd>This type helps distinguish between responses generated by inter
mediaries from those generated by the origin.</dd>
</dl>
</section> </section>
<section anchor="http-request-denied" numbered="true" toc="default"> <section anchor="http-request-denied" numbered="true" toc="default">
<name>HTTP Request Denied</name> <name>HTTP Request Denied</name>
<ul spacing="normal"> <dl>
<li>Name: http_request_denied</li> <dt>Name:</dt>
<li>Description: The intermediary rejected the HTTP request based on <dd>http_request_denied</dd>
its configuration and/or policy settings. The request wasn't forwarded to the n <dt>Description:</dt>
ext hop.</li> <dd>The intermediary rejected the HTTP request based on its configur
<li>Extra Parameters: None.</li> ation and/or policy settings. The request wasn't forwarded to the next hop.</dd>
<li>Recommended HTTP status code: 403</li> <dt>Extra Parameters:</dt>
<li>Response only generated by intermediaries: true</li> <dd>None</dd>
<li>Reference: [this document]</li> <dt>Recommended HTTP Status Code:</dt>
</ul> <dd>403</dd>
<dt>Response Only Generated by Intermediaries:</dt>
<dd>true</dd>
<dt>Reference:</dt>
<dd>RFC 9209</dd>
</dl>
</section> </section>
<section anchor="http-incomplete-response" numbered="true" toc="default" > <section anchor="http-incomplete-response" numbered="true" toc="default" >
<name>HTTP Incomplete Response</name> <name>HTTP Incomplete Response</name>
<ul spacing="normal"> <dl>
<li>Name: http_response_incomplete</li> <dt>Name:</dt>
<li>Description: The intermediary received an incomplete response to <dd>http_response_incomplete</dd>
the request from the next hop.</li> <dt>Description:</dt>
<li>Extra Parameters: None.</li> <dd>The intermediary received an incomplete response to the request
<li>Recommended HTTP status code: 502</li> from the next hop.</dd>
<li>Response only generated by intermediaries: false</li> <dt>Extra Parameters:</dt>
<li>Reference: [this document]</li> <dd>None</dd>
</ul> <dt>Recommended HTTP Status Code:</dt>
<dd>502</dd>
<dt>Response Only Generated by Intermediaries:</dt>
<dd>false</dd>
<dt>Reference:</dt>
<dd>RFC 9209</dd>
</dl>
</section> </section>
<section anchor="http-response-header-section-too-large" numbered="true" toc="default"> <section anchor="http-response-header-section-too-large" numbered="true" toc="default">
<name>HTTP Response Header Section Too Large</name> <name>HTTP Response Header Section Too Large</name>
<ul spacing="normal"> <dl>
<li>Name: http_response_header_section_size</li> <dt>Name:</dt>
<li>Description: The intermediary received a response to the request <dd>http_response_header_section_size</dd>
whose header section was considered too large.</li> <dt>Description:</dt>
<li> <dd>The intermediary received a response to the request whose header
<t>Extra Parameters: section was considered too large.</dd>
</t> <dt>Extra Parameters:</dt>
<ul spacing="normal"> <dd><t><br/></t>
<li>header-section-size: an sf-integer indicating how large the <dl>
headers received were. Note that they might not be complete; i.e., the intermedi <dt>header-section-size:</dt>
ary may have discarded or refused additional data.</li> <dd>An Integer indicating how large the received headers were. N
</ul> ote that they might not be complete; i.e., the intermediary may have discarded o
</li> r refused additional data.</dd>
<li>Recommended HTTP status code: 502</li> </dl>
<li>Response only generated by intermediaries: false</li> </dd>
<li>Reference: [this document]</li> <dt>Recommended HTTP Status Code:</dt>
</ul> <dd>502</dd>
<dt>Response Only Generated by Intermediaries:</dt>
<dd>false</dd>
<dt>Reference:</dt>
<dd>RFC 9209</dd>
</dl>
</section> </section>
<section anchor="http-response-header-field-line-too-large" numbered="tr ue" toc="default"> <section anchor="http-response-header-field-line-too-large" numbered="tr ue" toc="default">
<name>HTTP Response Header Field Line Too Large</name> <name>HTTP Response Header Field Line Too Large</name>
<ul spacing="normal"> <dl>
<li>Name: http_response_header_size</li> <dt>Name:</dt>
<li>Description: The intermediary received a response to the request <dd>http_response_header_size</dd>
containing an individual header field line that was considered too large.</li> <dt>Description:</dt>
<li> <dd>The intermediary received a response to the request containing a
<t>Extra Parameters: n individual header field line that was considered too large.</dd>
</t> <dt>Extra Parameters:</dt>
<ul spacing="normal"> <dd><t><br/></t>
<li>header-name: an sf-string indicating the name of the header <dl>
field that triggered the error.</li> <dt>header-name:</dt>
<li>header-size: an sf-integer indicating the size of the header <dd>A String indicating the name of the header field that trigge
field that triggered the error.</li> red the error.</dd>
</ul> <dt>header-size:</dt>
</li> <dd>An Integer indicating the size of the header field that trig
<li>Recommended HTTP status code: 502</li> gered the error.</dd>
<li>Response only generated by intermediaries: false</li> </dl>
<li>Reference: [this document]</li> </dd>
</ul> <dt>Recommended HTTP Status Code:</dt>
<dd>502</dd>
<dt>Response Only Generated by Intermediaries:</dt>
<dd>false</dd>
<dt>Reference:</dt>
<dd>RFC 9209</dd>
</dl>
</section> </section>
<section anchor="http-response-body-too-large" numbered="true" toc="defa ult"> <section anchor="http-response-body-too-large" numbered="true" toc="defa ult">
<name>HTTP Response Body Too Large</name> <name>HTTP Response Body Too Large</name>
<ul spacing="normal"> <dl>
<li>Name: http_response_body_size</li> <dt>Name:</dt>
<li>Description: The intermediary received a response to the request <dd>http_response_body_size</dd>
whose body was considered too large.</li> <dt>Description:</dt>
<li> <dd>The intermediary received a response to the request whose body w
<t>Extra Parameters: as considered too large.</dd>
</t> <dt>Extra Parameters:</dt>
<ul spacing="normal"> <dd><t><br/></t>
<li>body-size: an sf-integer indicating how large the body recei <dl>
ved was. Note that it may not have been complete; i.e., the intermediary may hav <dt>body-size:</dt>
e discarded or refused additional data.</li> <dd>An Integer indicating how large the received body was. Note
</ul> that it may not have been complete; i.e., the intermediary may have discarded or
</li> refused additional data.</dd>
<li>Recommended HTTP status code: 502</li> </dl>
<li>Response only generated by intermediaries: false</li> </dd>
<li>Reference: [this document]</li> <dt>Recommended HTTP Status Code:</dt>
</ul> <dd>502</dd>
<dt>Response Only Generated by Intermediaries:</dt>
<dd>false</dd>
<dt>Reference:</dt>
<dd>RFC 9209</dd>
</dl>
</section> </section>
<section anchor="http-response-trailer-section-too-large" numbered="true " toc="default"> <section anchor="http-response-trailer-section-too-large" numbered="true " toc="default">
<name>HTTP Response Trailer Section Too Large</name> <name>HTTP Response Trailer Section Too Large</name>
<ul spacing="normal"> <dl>
<li>Name: http_response_trailer_section_size</li> <dt>Name:</dt>
<li>Description: The intermediary received a response to the request <dd>http_response_trailer_section_size</dd>
whose trailer section was considered too large.</li> <dt>Description:</dt>
<li> <dd>The intermediary received a response to the request whose traile
<t>Extra Parameters: r section was considered too large.</dd>
</t> <dt>Extra Parameters:</dt>
<ul spacing="normal"> <dd><t><br/></t>
<li>trailer-section-size: an sf-integer indicating how large the <dl>
trailers received were. Note that they might not be complete; i.e., the interme <dt>trailer-section-size:</dt>
diary may have discarded or refused additional data.</li> <dd>An Integer indicating how large the received trailers were.
</ul> Note that they might not be complete; i.e., the intermediary may have discarded
</li> or refused additional data.</dd>
<li>Recommended HTTP status code: 502</li> </dl>
<li>Response only generated by intermediaries: false</li> </dd>
<li>Reference: [this document]</li> <dt>Recommended HTTP Status Code:</dt>
</ul> <dd>502</dd>
<dt>Response Only Generated by Intermediaries:</dt>
<dd>false</dd>
<dt>Reference:</dt>
<dd>RFC 9209</dd>
</dl>
</section> </section>
<section anchor="http-response-trailer-field-line-too-large" numbered="t rue" toc="default"> <section anchor="http-response-trailer-field-line-too-large" numbered="t rue" toc="default">
<name>HTTP Response Trailer Field Line Too Large</name> <name>HTTP Response Trailer Field Line Too Large</name>
<ul spacing="normal"> <dl>
<li>Name: http_response_trailer_size</li> <dt>Name:</dt>
<li>Description: The intermediary received a response to the request <dd>http_response_trailer_size</dd>
containing an individual trailer field line that was considered too large.</li> <dt>Description:</dt>
<li> <dd>The intermediary received a response to the request containing a
<t>Extra Parameters: n individual trailer field line that was considered too large.</dd>
</t> <dt>Extra Parameters:</dt>
<ul spacing="normal"> <dd><t><br/></t>
<li>trailer-name: an sf-string indicating the name of the traile <dl>
r field that triggered the error.</li> <dt>trailer-name:</dt>
<li>trailer-size: an sf-integer indicating the size of the trail <dd>A String indicating the name of the trailer field that trigg
er field that triggered the error.</li> ered the error.</dd>
</ul> <dt>trailer-size:</dt>
</li> <dd>An Integer indicating the size of the trailer field that tri
<li>Recommended HTTP status code: 502</li> ggered the error.</dd>
<li>Response only generated by intermediaries: false</li> </dl>
<li>Reference: [this document]</li> </dd>
</ul> <dt>Recommended HTTP Status Code:</dt>
<dd>502</dd>
<dt>Response Only Generated by Intermediaries:</dt>
<dd>false</dd>
<dt>Reference:</dt>
<dd>RFC 9209</dd>
</dl>
</section> </section>
<section anchor="http-response-transfer-coding-error" numbered="true" to c="default"> <section anchor="http-response-transfer-coding-error" numbered="true" to c="default">
<name>HTTP Response Transfer-Coding Error</name> <name>HTTP Response Transfer-Coding Error</name>
<ul spacing="normal"> <dl>
<li>Name: http_response_transfer_coding</li> <dt>Name:</dt>
<li>Description: The intermediary encountered an error decoding the <dd>http_response_transfer_coding</dd>
transfer-coding of the response.</li> <dt>Description:</dt>
<li> <dd>The intermediary encountered an error decoding the transfer codi
<t>Extra Parameters: ng of the response.</dd>
</t> <dt>Extra Parameters:</dt>
<ul spacing="normal"> <dd><t><br/></t>
<li>coding: an sf-token containing the specific coding (from the <dl>
HTTP Transfer Coding Registry) that caused the error.</li> <dt>coding:</dt>
</ul> <dd>A Token containing the specific coding (from the "HTTP Trans
</li> fer Coding Registry") that caused the error.</dd>
<li>Recommended HTTP status code: 502</li> </dl>
<li>Response only generated by intermediaries: false</li> </dd>
<li>Reference: [this document]</li> <dt>Recommended HTTP Status Code:</dt>
</ul> <dd>502</dd>
<dt>Response Only Generated by Intermediaries:</dt>
<dd>false</dd>
<dt>Reference:</dt>
<dd>RFC 9209</dd>
</dl>
</section> </section>
<section anchor="http-response-content-coding-error" numbered="true" toc ="default"> <section anchor="http-response-content-coding-error" numbered="true" toc ="default">
<name>HTTP Response Content-Coding Error</name> <name>HTTP Response Content-Coding Error</name>
<ul spacing="normal"> <dl>
<li>Name: http_response_content_coding</li> <dt>Name:</dt>
<li>Description: The intermediary encountered an error decoding the <dd>http_response_content_coding</dd>
content-coding of the response.</li> <dt>Description:</dt>
<li> <dd>The intermediary encountered an error decoding the content codin
<t>Extra Parameters: g of the response.</dd>
</t> <dt>Extra Parameters:</dt>
<ul spacing="normal"> <dd><t><br/></t>
<li>coding: an sf-token containing the specific coding (from the <dl>
HTTP Content Coding Registry) that caused the error.</li> <dt>coding:</dt>
</ul> <dd>A Token containing the specific coding (from the "HTTP Con
</li> tent Coding Registry") that caused the error.</dd>
<li>Recommended HTTP status code: 502</li> </dl>
<li>Response only generated by intermediaries: false</li> </dd>
<li>Reference: [this document]</li> <dt>Recommended HTTP Status Code:</dt>
</ul> <dd>502</dd>
<dt>Response Only Generated by Intermediaries:</dt>
<dd>false</dd>
<dt>Reference:</dt>
<dd>RFC 9209</dd>
</dl>
</section> </section>
<section anchor="http-response-timeout" numbered="true" toc="default"> <section anchor="http-response-timeout" numbered="true" toc="default">
<name>HTTP Response Timeout</name> <name>HTTP Response Timeout</name>
<ul spacing="normal"> <dl>
<li>Name: http_response_timeout</li> <dt>Name:</dt>
<li>Description: The intermediary reached a configured time limit wa <dd>http_response_timeout</dd>
iting for the complete response.</li> <dt>Description:</dt>
<li>Extra Parameters: None.</li> <dd>The intermediary reached a configured time limit waiting for the
<li>Recommended HTTP status code: 504</li> complete response.</dd>
<li>Response only generated by intermediaries: false</li> <dt>Extra Parameters:</dt>
<li>Reference: [this document]</li> <dd>None</dd>
</ul> <dt>Recommended HTTP Status Code:</dt>
<dd>504</dd>
<dt>Response Only Generated by Intermediaries:</dt>
<dd>false</dd>
<dt>Reference:</dt>
<dd>RFC 9209</dd>
</dl>
</section> </section>
<section anchor="http-upgrade-failed" numbered="true" toc="default"> <section anchor="http-upgrade-failed" numbered="true" toc="default">
<name>HTTP Upgrade Failed</name> <name>HTTP Upgrade Failed</name>
<ul spacing="normal"> <dl>
<li>Name: http_upgrade_failed</li> <dt>Name:</dt>
<li>Description: The HTTP Upgrade between the intermediary and the n <dd>http_upgrade_failed</dd>
ext hop failed.</li> <dt>Description:</dt>
<li>Extra Parameters: None.</li> <dd>The process of negotiating an upgrade of the HTTP version betwee
<li>Recommended HTTP status code: 502</li> n the intermediary and the next hop failed.</dd>
<li>Response only generated by intermediaries: true</li> <dt>Extra Parameters:</dt>
<li>Reference: [this document]</li> <dd>None</dd>
</ul> <dt>Recommended HTTP Status Code:</dt>
<dd>502</dd>
<dt>Response Only Generated by Intermediaries:</dt>
<dd>true</dd>
<dt>Reference:</dt>
<dd>RFC 9209</dd>
</dl>
</section> </section>
<section anchor="http-protocol-error" numbered="true" toc="default"> <section anchor="http-protocol-error" numbered="true" toc="default">
<name>HTTP Protocol Error</name> <name>HTTP Protocol Error</name>
<ul spacing="normal"> <dl>
<li>Name: http_protocol_error</li> <dt>Name:</dt>
<li>Description: The intermediary encountered a HTTP protocol error <dd>http_protocol_error</dd>
when communicating with the next hop. This error should only be used when a more <dt>Description:</dt>
specific one is not defined.</li> <dd>The intermediary encountered an HTTP protocol error when communi
<li>Extra Parameters: None.</li> cating with the next hop. This error should only be used when a more specific on
<li>Recommended HTTP status code: 502</li> e is not defined.</dd>
<li>Response only generated by intermediaries: false</li> <dt>Extra Parameters:</dt>
<li>Reference: [this document]</li> <dd>None</dd>
</ul> <dt>Recommended HTTP Status Code:</dt>
<dd>502</dd>
<dt>Response Only Generated by Intermediaries:</dt>
<dd>false</dd>
<dt>Reference:</dt>
<dd>RFC 9209</dd>
</dl>
</section> </section>
<section anchor="proxy-internal-response" numbered="true" toc="default"> <section anchor="proxy-internal-response" numbered="true" toc="default">
<name>Proxy Internal Response</name> <name>Proxy Internal Response</name>
<ul spacing="normal"> <dl>
<li>Name: proxy_internal_response</li> <dt>Name:</dt>
<li>Description: The intermediary generated the response locally, wi <dd>proxy_internal_response</dd>
thout attempting to connect to the next hop (e.g. in response to a request to a <dt>Description:</dt>
debug endpoint terminated at the intermediary).</li> <dd>The intermediary generated the response itself without attemptin
<li>Extra Parameters: None.</li> g to connect to the next hop.</dd>
<li>Recommended HTTP status code: The most appropriate status code f <dt>Extra Parameters:</dt>
or the response</li> <dd>None</dd>
<li>Response only generated by intermediaries: true</li> <dt>Recommended HTTP Status Code:</dt>
<li>Reference: [this document]</li> <dd>The most appropriate status code for the response</dd>
</ul> <dt>Response Only Generated by Intermediaries:</dt>
<dd>true</dd>
<dt>Reference:</dt>
<dd>RFC 9209</dd>
</dl>
</section> </section>
<section anchor="proxy-internal-error" numbered="true" toc="default"> <section anchor="proxy-internal-error" numbered="true" toc="default">
<name>Proxy Internal Error</name> <name>Proxy Internal Error</name>
<ul spacing="normal"> <dl>
<li>Name: proxy_internal_error</li> <dt>Name:</dt>
<li>Description: The intermediary encountered an internal error unre <dd>proxy_internal_error</dd>
lated to the origin.</li> <dt>Description:</dt>
<li>Extra Parameters: None</li> <dd>The intermediary encountered an internal error unrelated to the
<li>Recommended HTTP status code: 500</li> origin.</dd>
<li>Response only generated by intermediaries: true</li> <dt>Extra Parameters:</dt>
<li>Reference: [this document]</li> <dd>None</dd>
</ul> <dt>Recommended HTTP Status Code:</dt>
<dd>500</dd>
<dt>Response Only Generated by Intermediaries:</dt>
<dd>true</dd>
<dt>Reference:</dt>
<dd>RFC 9209</dd>
</dl>
</section> </section>
<section anchor="proxy-configuration-error" numbered="true" toc="default "> <section anchor="proxy-configuration-error" numbered="true" toc="default ">
<name>Proxy Configuration Error</name> <name>Proxy Configuration Error</name>
<ul spacing="normal"> <dl>
<li>Name: proxy_configuration_error</li> <dt>Name:</dt>
<li>Description: The intermediary encountered an error regarding its <dd>proxy_configuration_error</dd>
configuration.</li> <dt>Description:</dt>
<li>Extra Parameters: None</li> <dd>The intermediary encountered an error regarding its configuratio
<li>Recommended HTTP status code: 500</li> n.</dd>
<li>Response only generated by intermediaries: true</li> <dt>Extra Parameters:</dt>
<li>Reference: [this document]</li> <dd>None</dd>
</ul> <dt>Recommended HTTP Status Code:</dt>
<dd>500</dd>
<dt>Response Only Generated by Intermediaries:</dt>
<dd>true</dd>
<dt>Reference:</dt>
<dd>RFC 9209</dd>
</dl>
</section> </section>
<section anchor="proxy-loop-detected" numbered="true" toc="default"> <section anchor="proxy-loop-detected" numbered="true" toc="default">
<name>Proxy Loop Detected</name> <name>Proxy Loop Detected</name>
<ul spacing="normal"> <dl>
<li>Name: proxy_loop_detected</li> <dt>Name:</dt>
<li>Description: The intermediary tried to forward the request to it <dd>proxy_loop_detected</dd>
self, or a loop has been detected using different means (e.g. <xref target="RFC8 <dt>Description:</dt>
586" format="default"/>).</li> <dd>The intermediary tried to forward the request to itself, or a lo
<li>Extra Parameters: None.</li> op has been detected using different means (e.g., <xref target="RFC8586" format=
<li>Recommended HTTP status code: 502</li> "default"/>).</dd>
<li>Response only generated by intermediaries: true</li> <dt>Extra Parameters:</dt>
<li>Reference: [this document]</li> <dd>None</dd>
</ul> <dt>Recommended HTTP Status Code:</dt>
<dd>502</dd>
<dt>Response Only Generated by Intermediaries:</dt>
<dd>true</dd>
<dt>Reference:</dt><dd>RFC 9209</dd>
</dl>
</section> </section>
</section> </section>
<section anchor="register-error" numbered="true" toc="default"> <section anchor="register-error" numbered="true" toc="default">
<name>Defining New Proxy Error Types</name> <name>Defining New Proxy Error Types</name>
<t>New Proxy Error Types can be defined by registering them in the HTTP <t>New proxy error types can be defined by registering them in the "HTTP
Proxy Error Types registry.</t> Proxy Error Types" registry.</t>
<t>Registration requests are reviewed and approved by Expert Review, as <t>Registration requests are reviewed and approved by Expert Review, per
per <xref section="4.5" sectionFormat="comma" target="RFC8126" format="default"/ <xref section="4.5" sectionFormat="comma" target="RFC8126" format="default"/>.
>. A specification document is appreciated, but not required.</t> A specification document is appreciated but not required.</t>
<t>The Expert(s) should consider the following factors when evaluating r <t>The expert(s) should consider the following factors when evaluating r
equests:</t> equests:</t>
<ul spacing="normal"> <ul spacing="normal">
<li>Community feedback</li> <li>Community feedback</li>
<li>If the value is sufficiently well-defined</li> <li>If the value is sufficiently well-defined</li>
<li>Generic types are preferred over vendor-specific, application-spec <li>Generic types are preferred over vendor-specific, application-spec
ific or deployment-specific values. If a generic value cannot be agreed upon in ific, or deployment-specific values. If a generic value cannot be agreed upon in
the community, the types's name should be correspondingly specific (e.g., with a the community, the type's name should be correspondingly specific (e.g., with a
prefix that identifies the vendor, application or deployment).</li> prefix that identifies the vendor, application, or deployment).</li>
<li>Extra Parameters should not conflict with registered Proxy-Status <li>Extra parameters should not conflict with registered Proxy-Status
parameters.</li> parameters.</li>
</ul> </ul>
<t>Registration requests should use the following template:</t> <t>Registration requests should use the following template:</t>
<ul spacing="normal"> <dl>
<li>Name: [a name for the Proxy Error Type that matches sf-token]</li> <dt>Name:</dt>
<li>Description: [a description of the conditions that generate the Pr <dd>[a name for the proxy error type that is of type Token]</dd>
oxy Error Type]</li> <dt>Description:</dt>
<li>Extra Parameters: [zero or more optional parameters, along with th <dd>[a description of the conditions that generate the proxy error typ
eir allowable type(s)]</li> e]</dd>
<li>Recommended HTTP status code: [the appropriate HTTP status code fo <dt>Extra Parameters:</dt>
r this entry]</li> <dd>[zero or more optional parameters, along with their allowable Stru
<li>Response only generated by intermediaries: ['true' or 'false']</li ctured Type(s)]</dd>
> <dt>Recommended HTTP Status Code:</dt>
<li>Reference: [to a specification defining this error type; optional] <dd>[the appropriate HTTP status code for this entry]</dd>
</li> <dt>Response Only Generated by Intermediaries:</dt>
<li>Notes: [optional]</li> <dd>['true' or 'false']</dd>
</ul> <dt>Reference:</dt>
<t>If the Proxy Error Type might occur in responses that are not generat <dd>[to a specification defining this error type; optional]</dd>
ed by the intermediary -- for example, when an error is detected as the response <dt>Notes:</dt>
is streamed from a forward connection, causing a Proxy-Status trailer field to <dd>[optional]</dd>
be appended -- the 'Response only generated by intermediaries' should be 'false' </dl>
. If the Proxy Error Type only occurs in responses that are generated by the int <t>If the proxy error type might occur in responses that are not generat
ermediary, it should be 'true'.</t> ed by the intermediary -- for example, when an error is detected as the response
<t>See the registry at <eref target="https://iana.org/assignments/http-p is streamed from a forward connection, causing a Proxy-Status trailer field to
roxy-status">https://iana.org/assignments/http-proxy-status</eref> for details o be appended -- the 'Response only generated by intermediaries' should be 'false'
n where to send registration requests.</t> . If the proxy error type only occurs in responses that are generated by the int
ermediary, it should be 'true'.</t>
<t>See the registry at <eref target="https://www.iana.org/assignments/ht
tp-proxy-status" brackets="angle"/> for details on where to send registration re
quests.</t>
</section> </section>
</section> </section>
<section anchor="iana-considerations" numbered="true" toc="default"> <section anchor="iana-considerations" numbered="true" toc="default">
<name>IANA Considerations</name> <name>IANA Considerations</name>
<t>Upon publication, please create the HTTP Proxy-Status Parameters regist <t>IANA has created the "HTTP Proxy-Status Parameters" registry and the "H
ry and the HTTP Proxy Error Types registry at <eref target="https://iana.org/ass TTP Proxy Error Types" registry at <eref target="https://www.iana.org/assignment
ignments/http-proxy-status">https://iana.org/assignments/http-proxy-status</eref s/http-proxy-status" brackets="angle"/> and has populated them with the types de
> and populate them with the types defined in <xref target="params" format="defa fined in Sections <xref target="params" format="counter"/> and <xref target="err
ult"/> and <xref target="error-types" format="default"/> respectively; see <xref or-types" format="counter"/> respectively; see Sections <xref target="register-p
target="register-param" format="default"/> and <xref target="register-error" fo aram" format="counter"/> and <xref target="register-error" format="counter"/> fo
rmat="default"/> for its associated procedures.</t> r their associated procedures.</t>
<t>Additionally, please register the following entry in the Hypertext Tran <t>Additionally, the following entry has been added to the "Hypertext Tran
sfer Protocol (HTTP) Field Name Registry:</t> sfer Protocol (HTTP) Field Name Registry":</t>
<ul spacing="normal"> <dl spacing="compact">
<li>Field name: Proxy-Status</li> <dt>Field name:</dt>
<li>Status: permanent</li> <dd>Proxy-Status</dd>
<li>Specification document(s): [this document]</li> <dt>Status:</dt>
<li>Comments:</li> <dd>permanent</dd>
</ul> <dt>Specification document(s):</dt>
<dd>RFC 9209</dd>
<dt>Comments:</dt>
<dd/>
</dl>
</section> </section>
<section anchor="security" numbered="true" toc="default"> <section anchor="security" numbered="true" toc="default">
<name>Security Considerations</name> <name>Security Considerations</name>
<t>One of the primary security concerns when using Proxy-Status is leaking <t>One of the primary security concerns when using Proxy-Status is leaking
information that might aid an attacker. For example, information about the inte information that might aid an attacker. For example, information about the inte
rmediary's configuration and back-end topology can be exposed, allowing attacker rmediary's configuration and backend topology can be exposed, allowing attackers
s to directly target back-end services that are not prepared for high traffic vo to directly target backend services that are not prepared for high traffic volu
lume or malformed inputs. Some information might only be suitable to reveal to me or malformed inputs. Some information might only be suitable to reveal to au
authorized parties.</t> thorized parties.</t>
<t>As a result, care needs to be taken when deciding to generate a Proxy-S <t>As a result, care needs to be taken when deciding to generate a Proxy-S
tatus field and what information to include in it. Note that intermediaries are tatus field and what information to include in it. Note that intermediaries are
not required to generate a Proxy-Status field in any response, and can condition not required to generate a Proxy-Status field in any response and can conditiona
ally generate them based upon request attributes (e.g., authentication tokens, I lly generate them based upon request attributes (e.g., authentication tokens, IP
P address).</t> address).</t>
<t>Likewise, generation of all parameters is optional, as is generation of <t>Likewise, generation of all parameters is optional, as is the generatio
the field itself. Also, the field's content is not verified; an intermediary ca n of the field itself. Also, the field's content is not verified; an intermediar
n claim certain actions (e.g., sending a request over an encrypted channel) but y can claim certain actions (e.g., sending a request over an encrypted channel)
fail to actually do that.</t> but fail to actually do that.</t>
</section> </section>
</middle> </middle>
<back> <back>
<references> <references>
<name>References</name> <name>References</name>
<references> <references>
<name>Normative References</name> <name>Normative References</name>
<reference anchor="HTTP"> <reference anchor='HTTP' target='https://www.rfc-editor.org/info/rfc9110 '>
<front> <front>
<title>HTTP Semantics</title> <title>HTTP Semantics</title>
<author fullname="Roy T. Fielding"> <author initials='R' surname='Fielding' fullname='Roy Fielding' role
<organization>Adobe</organization> ="editor">
<organization />
</author> </author>
<author fullname="Mark Nottingham"> <author initials='M' surname='Nottingham' fullname='Mark Nottingham'
<organization>Fastly</organization> role="editor">
<organization />
</author> </author>
<author fullname="Julian Reschke"> <author initials='J' surname='Reschke' fullname='Julian Reschke' rol
<organization>greenbytes GmbH</organization> e="editor">
<organization />
</author> </author>
<date day="12" month="September" year="2021"/> <date year='2022' month='June'/>
<abstract>
<t> The Hypertext Transfer Protocol (HTTP) is a stateless applic
ation-
level protocol for distributed, collaborative, hypertext information
systems. This document describes the overall architecture of HTTP,
establishes common terminology, and defines aspects of the protocol
that are shared by all versions. In this definition are core
protocol elements, extensibility mechanisms, and the "http" and
"https" Uniform Resource Identifier (URI) schemes.
This document updates RFC 3864 and obsoletes RFC 2818, RFC 7231, RFC
7232, RFC 7233, RFC 7235, RFC 7538, RFC 7615, RFC 7694, and portions
of RFC 7230.
</t>
</abstract>
</front> </front>
<seriesInfo name="Internet-Draft" value="draft-ietf-httpbis-semantics- <seriesInfo name="STD" value="97"/>
19"/> <seriesInfo name="RFC" value="9110"/>
<seriesInfo name="DOI" value="10.17487/RFC9110"/>
</reference> </reference>
<reference anchor="STRUCTURED-FIELDS"> <reference anchor="STRUCTURED-FIELDS" target='https://www.rfc-editor.org /info/rfc8941'>
<front> <front>
<title>Structured Field Values for HTTP</title> <title>Structured Field Values for HTTP</title>
<author fullname="M. Nottingham" initials="M." surname="Nottingham"> <author fullname="M. Nottingham" initials="M." surname="Nottingham">
<organization/> <organization/>
</author> </author>
<author fullname="P-H. Kamp" initials="P-H." surname="Kamp"> <author fullname="P-H. Kamp" initials="P-H." surname="Kamp">
<organization/> <organization/>
</author> </author>
<date month="February" year="2021"/> <date month="March" year="2021"/>
<abstract>
<t>This document describes a set of data types and associated algo
rithms that are intended to make it easier and safer to define and handle HTTP h
eader and trailer fields, known as "Structured Fields", "Structured Headers", or
"Structured Trailers". It is intended for use by specifications of new HTTP fie
lds that wish to use a common syntax that is more restrictive than traditional H
TTP field values.</t>
</abstract>
</front> </front>
<seriesInfo name="RFC" value="8941"/> <seriesInfo name="RFC" value="8941"/>
<seriesInfo name="DOI" value="10.17487/RFC8941"/> <seriesInfo name="DOI" value="10.17487/RFC8941"/>
</reference> </reference>
<reference anchor="RFC2119"> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.R
<front> FC.2119.xml"/>
<title>Key words for use in RFCs to Indicate Requirement Levels</tit <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.R
le> FC.8126.xml"/>
<author fullname="S. Bradner" initials="S." surname="Bradner"> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.R
<organization/> FC.8499.xml"/>
</author> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.R
<date month="March" year="1997"/> FC.8174.xml"/>
<abstract> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.R
<t>In many standards track documents several words are used to sig FC.7301.xml"/>
nify the requirements in the specification. These words are often capitalized. <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.R
This document defines these words as they should be interpreted in IETF document FC.8914.xml"/>
s. This document specifies an Internet Best Current Practices for the Internet <reference anchor="TLS" target="https://www.rfc-editor.org/info/rfc8446"
Community, and requests discussion and suggestions for improvements.</t> >
</abstract>
</front>
<seriesInfo name="BCP" value="14"/>
<seriesInfo name="RFC" value="2119"/>
<seriesInfo name="DOI" value="10.17487/RFC2119"/>
</reference>
<reference anchor="RFC8126">
<front>
<title>Guidelines for Writing an IANA Considerations Section in RFCs
</title>
<author fullname="M. Cotton" initials="M." surname="Cotton">
<organization/>
</author>
<author fullname="B. Leiba" initials="B." surname="Leiba">
<organization/>
</author>
<author fullname="T. Narten" initials="T." surname="Narten">
<organization/>
</author>
<date month="June" year="2017"/>
<abstract>
<t>Many protocols make use of points of extensibility that use con
stants to identify various protocol parameters. To ensure that the values in th
ese fields do not have conflicting uses and to promote interoperability, their a
llocations are often coordinated by a central record keeper. For IETF protocols
, that role is filled by the Internet Assigned Numbers Authority (IANA).</t>
<t>To make assignments in a given registry prudently, guidance des
cribing the conditions under which new values should be assigned, as well as whe
n and how modifications to existing values can be made, is needed. This documen
t defines a framework for the documentation of these guidelines by specification
authors, in order to assure that the provided guidance for the IANA Considerati
ons is clear and addresses the various issues that are likely in the operation o
f a registry.</t>
<t>This is the third edition of this document; it obsoletes RFC 52
26.</t>
</abstract>
</front>
<seriesInfo name="BCP" value="26"/>
<seriesInfo name="RFC" value="8126"/>
<seriesInfo name="DOI" value="10.17487/RFC8126"/>
</reference>
<reference anchor="RFC8499">
<front>
<title>DNS Terminology</title>
<author fullname="P. Hoffman" initials="P." surname="Hoffman">
<organization/>
</author>
<author fullname="A. Sullivan" initials="A." surname="Sullivan">
<organization/>
</author>
<author fullname="K. Fujiwara" initials="K." surname="Fujiwara">
<organization/>
</author>
<date month="January" year="2019"/>
<abstract>
<t>The Domain Name System (DNS) is defined in literally dozens of
different RFCs. The terminology used by implementers and developers of DNS prot
ocols, and by operators of DNS systems, has sometimes changed in the decades sin
ce the DNS was first defined. This document gives current definitions for many
of the terms used in the DNS in a single document.</t>
<t>This document obsoletes RFC 7719 and updates RFC 2308.</t>
</abstract>
</front>
<seriesInfo name="BCP" value="219"/>
<seriesInfo name="RFC" value="8499"/>
<seriesInfo name="DOI" value="10.17487/RFC8499"/>
</reference>
<reference anchor="RFC8174">
<front>
<title>Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words</ti
tle>
<author fullname="B. Leiba" initials="B." surname="Leiba">
<organization/>
</author>
<date month="May" year="2017"/>
<abstract>
<t>RFC 2119 specifies common key words that may be used in protoco
l specifications. This document aims to reduce the ambiguity by clarifying tha
t only UPPERCASE usage of the key words have the defined special meanings.</t>
</abstract>
</front>
<seriesInfo name="BCP" value="14"/>
<seriesInfo name="RFC" value="8174"/>
<seriesInfo name="DOI" value="10.17487/RFC8174"/>
</reference>
<reference anchor="RFC7301">
<front>
<title>Transport Layer Security (TLS) Application-Layer Protocol Neg
otiation Extension</title>
<author fullname="S. Friedl" initials="S." surname="Friedl">
<organization/>
</author>
<author fullname="A. Popov" initials="A." surname="Popov">
<organization/>
</author>
<author fullname="A. Langley" initials="A." surname="Langley">
<organization/>
</author>
<author fullname="E. Stephan" initials="E." surname="Stephan">
<organization/>
</author>
<date month="July" year="2014"/>
<abstract>
<t>This document describes a Transport Layer Security (TLS) extens
ion for application-layer protocol negotiation within the TLS handshake. For ins
tances in which multiple application protocols are supported on the same TCP or
UDP port, this extension allows the application layer to negotiate which protoco
l will be used within the TLS connection.</t>
</abstract>
</front>
<seriesInfo name="RFC" value="7301"/>
<seriesInfo name="DOI" value="10.17487/RFC7301"/>
</reference>
<reference anchor="RFC8914">
<front>
<title>Extended DNS Errors</title>
<author fullname="W. Kumari" initials="W." surname="Kumari">
<organization/>
</author>
<author fullname="E. Hunt" initials="E." surname="Hunt">
<organization/>
</author>
<author fullname="R. Arends" initials="R." surname="Arends">
<organization/>
</author>
<author fullname="W. Hardaker" initials="W." surname="Hardaker">
<organization/>
</author>
<author fullname="D. Lawrence" initials="D." surname="Lawrence">
<organization/>
</author>
<date month="October" year="2020"/>
<abstract>
<t>This document defines an extensible method to return additional
information about the cause of DNS errors. Though created primarily to extend S
ERVFAIL to provide additional information about the cause of DNS and DNSSEC fail
ures, the Extended DNS Errors option defined in this document allows all respons
e types to contain extended error information. Extended DNS Error information do
es not change the processing of RCODEs.</t>
</abstract>
</front>
<seriesInfo name="RFC" value="8914"/>
<seriesInfo name="DOI" value="10.17487/RFC8914"/>
</reference>
<reference anchor="RFC8446">
<front> <front>
<title>The Transport Layer Security (TLS) Protocol Version 1.3</titl e> <title>The Transport Layer Security (TLS) Protocol Version 1.3</titl e>
<author fullname="E. Rescorla" initials="E." surname="Rescorla"> <author initials="E." surname="Rescorla" fullname="Eric Rescorla"/>
<organization/> <date year="2018" month="August"/>
</author>
<date month="August" year="2018"/>
<abstract>
<t>This document specifies version 1.3 of the Transport Layer Secu
rity (TLS) protocol. TLS allows client/server applications to communicate over
the Internet in a way that is designed to prevent eavesdropping, tampering, and
message forgery.</t>
<t>This document updates RFCs 5705 and 6066, and obsoletes RFCs 50
77, 5246, and 6961. This document also specifies new requirements for TLS 1.2 i
mplementations.</t>
</abstract>
</front> </front>
<seriesInfo name="RFC" value="8446"/> <seriesInfo name="RFC" value="8446"/>
<seriesInfo name="DOI" value="10.17487/RFC8446"/> <seriesInfo name="DOI" value="10.17487/RFC8446"/>
</reference> </reference>
</references> </references>
<references> <references>
<name>Informative References</name> <name>Informative References</name>
<reference anchor="RFC5234"> <xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.R
<front> FC.8586.xml"/>
<title>Augmented BNF for Syntax Specifications: ABNF</title>
<author fullname="D. Crocker" initials="D." role="editor" surname="C
rocker">
<organization/>
</author>
<author fullname="P. Overell" initials="P." surname="Overell">
<organization/>
</author>
<date month="January" year="2008"/>
<abstract>
<t>Internet technical specifications often need to define a formal
syntax. Over the years, a modified version of Backus-Naur Form (BNF), called A
ugmented BNF (ABNF), has been popular among many Internet specifications. The c
urrent specification documents ABNF. It balances compactness and simplicity with
reasonable representational power. The differences between standard BNF and AB
NF involve naming rules, repetition, alternatives, order-independence, and value
ranges. This specification also supplies additional rule definitions and encod
ing for a core lexical analyzer of the type common to several Internet specifica
tions. [STANDARDS-TRACK]</t>
</abstract>
</front>
<seriesInfo name="STD" value="68"/>
<seriesInfo name="RFC" value="5234"/>
<seriesInfo name="DOI" value="10.17487/RFC5234"/>
</reference>
<reference anchor="RFC8586">
<front>
<title>Loop Detection in Content Delivery Networks (CDNs)</title>
<author fullname="S. Ludin" initials="S." surname="Ludin">
<organization/>
</author>
<author fullname="M. Nottingham" initials="M." surname="Nottingham">
<organization/>
</author>
<author fullname="N. Sullivan" initials="N." surname="Sullivan">
<organization/>
</author>
<date month="April" year="2019"/>
<abstract>
<t>This document defines the CDN-Loop request header field for HTT
P. CDN-Loop addresses an operational need that occurs when an HTTP request is in
tentionally forwarded between Content Delivery Networks (CDNs), but is then acci
dentally or maliciously re-routed back into the original CDN causing a non-termi
nating loop. The new header field can be used to identify the error and termina
te the loop.</t>
</abstract>
</front>
<seriesInfo name="RFC" value="8586"/>
<seriesInfo name="DOI" value="10.17487/RFC8586"/>
</reference>
</references> </references>
</references> </references>
</back> </back>
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