draft-ietf-httpbis-proxy-status-02.txt   draft-ietf-httpbis-proxy-status-03.txt 
HTTP M. Nottingham HTTP M. Nottingham
Internet-Draft Fastly Internet-Draft Fastly
Intended status: Standards Track P. Sikora Intended status: Standards Track P. Sikora
Expires: February 12, 2021 Google Expires: 13 August 2021 Google
August 11, 2020 9 February 2021
The Proxy-Status HTTP Response Header Field The Proxy-Status HTTP Response Header Field
draft-ietf-httpbis-proxy-status-02 draft-ietf-httpbis-proxy-status-03
Abstract Abstract
This document defines the Proxy-Status HTTP field to convey the This document defines the Proxy-Status HTTP field to convey the
details of intermediary handling of responses, including generated details of intermediary response handling, including generated
errors. errors.
Note to Readers Note to Readers
_RFC EDITOR: please remove this section before publication_ _RFC EDITOR: please remove this section before publication_
Discussion of this draft takes place on the HTTP working group Discussion of this draft takes place on the HTTP working group
mailing list (ietf-http-wg@w3.org), which is archived at mailing list (ietf-http-wg@w3.org), which is archived at
https://lists.w3.org/Archives/Public/ietf-http-wg/ [1]. https://lists.w3.org/Archives/Public/ietf-http-wg/
(https://lists.w3.org/Archives/Public/ietf-http-wg/).
Working Group information can be found at https://httpwg.org/ [2]; Working Group information can be found at https://httpwg.org/
source code and issues list for this draft can be found at (https://httpwg.org/); source code and issues list for this draft can
https://github.com/httpwg/http-extensions/labels/proxy-status [3]. be found at https://github.com/httpwg/http-extensions/labels/proxy-
status (https://github.com/httpwg/http-extensions/labels/proxy-
status).
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on February 12, 2021. This Internet-Draft will expire on 13 August 2021.
Copyright Notice Copyright Notice
Copyright (c) 2020 IETF Trust and the persons identified as the Copyright (c) 2021 IETF Trust and the persons identified as the
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Notational Conventions . . . . . . . . . . . . . . . . . 4 1.1. Notational Conventions . . . . . . . . . . . . . . . . . 4
2. The Proxy-Status HTTP Field . . . . . . . . . . . . . . . . . 4 2. The Proxy-Status HTTP Field . . . . . . . . . . . . . . . . . 4
2.1. Proxy-Status Parameters . . . . . . . . . . . . . . . . . 5 2.1. Proxy-Status Parameters . . . . . . . . . . . . . . . . . 5
2.1.1. next-hop . . . . . . . . . . . . . . . . . . . . . . 5 2.1.1. error . . . . . . . . . . . . . . . . . . . . . . . . 5
2.1.2. next-protocol . . . . . . . . . . . . . . . . . . . . 5 2.1.2. next-hop . . . . . . . . . . . . . . . . . . . . . . 6
2.1.3. error . . . . . . . . . . . . . . . . . . . . . . . . 6 2.1.3. next-protocol . . . . . . . . . . . . . . . . . . . . 7
2.1.4. details . . . . . . . . . . . . . . . . . . . . . . . 7 2.2. received-status . . . . . . . . . . . . . . . . . . . . . 7
2.2. Defining New Proxy-Status Parameters . . . . . . . . . . 7 2.2.1. details . . . . . . . . . . . . . . . . . . . . . . . 7
2.3. Proxy Error Types . . . . . . . . . . . . . . . . . . . . 8 2.3. Defining New Proxy-Status Parameters . . . . . . . . . . 7
2.3.1. DNS Timeout . . . . . . . . . . . . . . . . . . . . . 8 2.4. Proxy Error Types . . . . . . . . . . . . . . . . . . . . 8
2.3.2. DNS Error . . . . . . . . . . . . . . . . . . . . . . 8 2.4.1. DNS Timeout . . . . . . . . . . . . . . . . . . . . . 8
2.3.3. Destination Not Found . . . . . . . . . . . . . . . . 8 2.4.2. DNS Error . . . . . . . . . . . . . . . . . . . . . . 8
2.3.4. Destination Unavailable . . . . . . . . . . . . . . . 9 2.4.3. Destination Not Found . . . . . . . . . . . . . . . . 9
2.3.5. Destination IP Prohibited . . . . . . . . . . . . . . 9 2.4.4. Destination Unavailable . . . . . . . . . . . . . . . 9
2.3.6. Destination IP Unroutable . . . . . . . . . . . . . . 9 2.4.5. Destination IP Prohibited . . . . . . . . . . . . . . 9
2.3.7. Connection Refused . . . . . . . . . . . . . . . . . 9 2.4.6. Destination IP Unroutable . . . . . . . . . . . . . . 10
2.3.8. Connection Terminated . . . . . . . . . . . . . . . . 10 2.4.7. Connection Refused . . . . . . . . . . . . . . . . . 10
2.3.9. Connection Timeout . . . . . . . . . . . . . . . . . 10 2.4.8. Connection Terminated . . . . . . . . . . . . . . . . 10
2.3.10. Connection Read Timeout . . . . . . . . . . . . . . . 10 2.4.9. Connection Timeout . . . . . . . . . . . . . . . . . 10
2.3.11. Connection Write Timeout . . . . . . . . . . . . . . 10 2.4.10. Connection Read Timeout . . . . . . . . . . . . . . . 11
2.3.12. Connection Limit Reached . . . . . . . . . . . . . . 11 2.4.11. Connection Write Timeout . . . . . . . . . . . . . . 11
2.3.13. TLS Protocol Error . . . . . . . . . . . . . . . . . 11 2.4.12. Connection Limit Reached . . . . . . . . . . . . . . 11
2.3.14. TLS Certificate Error . . . . . . . . . . . . . . . . 11 2.4.13. TLS Protocol Error . . . . . . . . . . . . . . . . . 11
2.3.15. TLS Alert Received . . . . . . . . . . . . . . . . . 11 2.4.14. TLS Certificate Error . . . . . . . . . . . . . . . . 12
2.3.16. HTTP Request Error . . . . . . . . . . . . . . . . . 12 2.4.15. TLS Alert Received . . . . . . . . . . . . . . . . . 12
2.3.17. HTTP Request Denied . . . . . . . . . . . . . . . . . 12 2.4.16. HTTP Request Error . . . . . . . . . . . . . . . . . 13
2.3.18. HTTP Incomplete Response . . . . . . . . . . . . . . 12 2.4.17. HTTP Request Denied . . . . . . . . . . . . . . . . . 13
2.3.19. HTTP Response Header Block Too Large . . . . . . . . 13 2.4.18. HTTP Incomplete Response . . . . . . . . . . . . . . 13
2.3.20. HTTP Response Header Too Large . . . . . . . . . . . 13 2.4.19. HTTP Response Header Section Too Large . . . . . . . 14
2.3.21. HTTP Response Body Too Large . . . . . . . . . . . . 13 2.4.20. HTTP Response Header Too Large . . . . . . . . . . . 14
2.3.22. HTTP Response Transfer-Coding Error . . . . . . . . . 14 2.4.21. HTTP Response Body Too Large . . . . . . . . . . . . 14
2.3.23. HTTP Response Content-Coding Error . . . . . . . . . 14 2.4.22. HTTP Response Trailer Section Too Large . . . . . . . 15
2.3.24. HTTP Response Timeout . . . . . . . . . . . . . . . . 14 2.4.23. HTTP Response Trailer Too Large . . . . . . . . . . . 15
2.3.25. HTTP Upgrade Failed . . . . . . . . . . . . . . . . . 14 2.4.24. HTTP Response Transfer-Coding Error . . . . . . . . . 16
2.3.26. HTTP Protocol Error . . . . . . . . . . . . . . . . . 15 2.4.25. HTTP Response Content-Coding Error . . . . . . . . . 16
2.3.27. Proxy Internal Response . . . . . . . . . . . . . . . 15 2.4.26. HTTP Response Timeout . . . . . . . . . . . . . . . . 16
2.3.28. Proxy Internal Error . . . . . . . . . . . . . . . . 15 2.4.27. HTTP Upgrade Failed . . . . . . . . . . . . . . . . . 17
2.3.29. Proxy Configuration Error . . . . . . . . . . . . . . 15 2.4.28. HTTP Protocol Error . . . . . . . . . . . . . . . . . 17
2.3.30. Proxy Loop Detected . . . . . . . . . . . . . . . . . 16 2.4.29. Proxy Internal Response . . . . . . . . . . . . . . . 17
2.4. Defining New Proxy Error Types . . . . . . . . . . . . . 16 2.4.30. Proxy Internal Error . . . . . . . . . . . . . . . . 17
3. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 17 2.4.31. Proxy Configuration Error . . . . . . . . . . . . . . 18
4. Security Considerations . . . . . . . . . . . . . . . . . . . 17 2.4.32. Proxy Loop Detected . . . . . . . . . . . . . . . . . 18
5. References . . . . . . . . . . . . . . . . . . . . . . . . . 17 2.5. Defining New Proxy Error Types . . . . . . . . . . . . . 18
5.1. Normative References . . . . . . . . . . . . . . . . . . 17 3. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 19
5.2. Informative References . . . . . . . . . . . . . . . . . 18 4. Security Considerations . . . . . . . . . . . . . . . . . . . 19
5.3. URIs . . . . . . . . . . . . . . . . . . . . . . . . . . 18 5. References . . . . . . . . . . . . . . . . . . . . . . . . . 20
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 19 5.1. Normative References . . . . . . . . . . . . . . . . . . 20
5.2. Informative References . . . . . . . . . . . . . . . . . 20
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 21
1. Introduction 1. Introduction
HTTP intermediaries - including both forward proxies and gateways HTTP intermediaries -- including both forward proxies and gateways
(also known as "reverse proxies") - have become an increasingly (also known as "reverse proxies") -- have become an increasingly
significant part of HTTP deployments. In particular, reverse proxies significant part of HTTP deployments. In particular, reverse proxies
and Content Delivery Networks (CDNs) form part of the critical and Content Delivery Networks (CDNs) form part of the critical
infrastructure of many Web sites. infrastructure of many Web sites.
Typically, HTTP intermediaries forward requests towards the origin Typically, HTTP intermediaries forward requests towards the origin
server and then forward their responses back to clients. However, if server and then forward their responses back to clients. However, if
an error occurs before a response is obtained from upstream, the an error occurs before a response is obtained from upstream, the
response is generated by the intermediary itself. response is often generated by the intermediary itself.
HTTP accommodates these types of errors with a few status codes; for HTTP accommodates these types of errors with a few status codes; for
example, 502 Bad Gateway and 504 Gateway Timeout. However, example, 502 Bad Gateway and 504 Gateway Timeout. However,
experience has shown that more information is necessary to aid experience has shown that more information is necessary to aid
debugging and communicate what's happened to the client. debugging and communicate what's happened to the client.
Additionally, intermediaries sometimes want to convey additional Additionally, intermediaries sometimes want to convey additional
information about their handling of a response, even if they did not information about their handling of a response, even if they did not
generate it. generate it.
To enable these uses, Section 2 defines a new HTTP response field to To enable these uses, Section 2 defines a new HTTP response field to
allow intermediaries to convey details of their handling of a allow intermediaries to convey details of their handling of a
response, Section 2.1 enumerates the kind of information that can be response, Section 2.1 enumerates the kind of information that can be
conveyed, and Section 2.3 defines a set of error types for use when a conveyed, and Section 2.4 defines a set of error types for use when a
proxy generates the response. proxy encounters an issue when obtaining a response for the request.
1.1. Notational Conventions 1.1. Notational Conventions
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP "OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here. capitals, as shown here.
This specification uses Structured Headers This specification uses Structured Fields
[I-D.ietf-httpbis-header-structure] to specify syntax. The terms sf- [I-D.ietf-httpbis-header-structure] to specify syntax and parsing.
list, sf-item, sf-string, sf-token, sf-integer and key refer to the The terms sf-list, sf-item, sf-string, sf-token, sf-integer and key
structured types defined therein. refer to the structured types defined therein.
Note that in this specification, "proxy" is used to indicate both Note that in this specification, "proxy" is used to indicate both
forward and reverse proxies, otherwise known as gateways. "Next hop" forward and reverse proxies, otherwise known as gateways. "Next hop"
indicates the connection in the direction leading to the origin indicates the connection in the direction leading to the origin
server for the request. server for the request.
2. The Proxy-Status HTTP Field 2. The Proxy-Status HTTP Field
The Proxy-Status HTTP response field allows an intermediary to convey The Proxy-Status HTTP response field allows an intermediary to convey
additional information about its handling of a response and its additional information about its handling of a response and its
associated request. associated request.
It is a List [I-D.ietf-httpbis-header-structure]: It is a List [I-D.ietf-httpbis-header-structure], Section 3.1:
Proxy-Status = sf-list Proxy-Status = sf-list
Each member of the list represents an intermediary that has handled Each member of the list represents an intermediary that has handled
the response. The first member of the list represents the the response. The first member of the list represents the
intermediary closest to the origin server, and the last member of the intermediary closest to the origin server, and the last member of the
list represents the intermediary closest to the user agent. list represents the intermediary closest to the user agent.
For example: For example:
Proxy-Status: FooProxy, ExampleCDN Proxy-Status: FooProxy, ExampleCDN
indicates that this response was handled first by FooProxy and then indicates that this response was handled first by FooProxy and then
ExampleCDN. ExampleCDN.
Intermediaries determine when it is appropriate to add the Proxy- Intermediaries determine when it is appropriate to add the Proxy-
Status field to a response. Some might decide to add it to all Status field to a response. Some might decide to append to it to all
responses, whereas others might only do so when specifically responses, whereas others might only do so when specifically
configured to, or when the request contains a header that activates a configured to, or when the request contains a header that activates a
debugging mode. debugging mode.
The list members identify the intermediary that inserted the value, Each member of the list identifies the intermediary that inserted the
and MUST have a type of either sf-string or sf-token. Depending on value, and MUST have a type of either sf-string or sf-token.
the deployment, this might be a product or service name (e.g., Depending on the deployment, this might be a product or service name
ExampleProxy or "Example CDN"), a hostname ("proxy-3.example.com"), (e.g., ExampleProxy or "Example CDN"), a hostname ("proxy-
and IP address, or a generated string. 3.example.com"), an IP address, or a generated string.
Parameters on each member convey additional information about that Parameters on each member convey additional information about that
intermediary's handling of the response; see Section 2.1 for defined intermediary's handling of the response and its associated request;
parameters. While all of these parameters are OPTIONAL, see Section 2.1. While all of these parameters are OPTIONAL,
intermediaries are encouraged to provide as much information as intermediaries are encouraged to provide as much information as
possible. possible (but see Section 4 for security considerations in doing so).
When adding a value to the Proxy-Status field, intermediaries SHOULD When adding a value to the Proxy-Status field, intermediaries SHOULD
preserve the existing contents of the field, to allow debugging of preserve the existing members of the field, to allow debugging of the
the entire chain of intermediaries handling the request. entire chain of intermediaries handling the request.
Proxy-Status MAY be sent in HTTP trailers, but - as with all trailers
- it might be silently discarded along the path to the user agent, so
this SHOULD NOT be done unless it is not possible to send it in
headers. For example, if an intermediary is streaming a response and
the upstream connection suddenly terminates, Proxy-Status can be
appended to the trailers of the outgoing message (since the headers
have already been sent).
Note that there are various security considerations for Proxy-Status MAY be sent in HTTP trailers. For example, if an
intermediaries using the Proxy-Status field; see Section 4. intermediary is streaming a response and the upstream connection
suddenly terminates, Proxy-Status can only be appended to the
trailers of the outgoing message, since the headers have already been
sent. As with all trailers, it might be silently discarded along the
path to the user agent, so this SHOULD NOT be done unless it is not
possible to send it in headers, and an intermediary MUST NOT send
Proxy-Status as a trailer field unless it has also sent a
corresponding Proxy-Status header field in the same message, so that
the trailer value's ordering relative to other intermediaries is
preserved.
Origin servers MUST NOT generate the Proxy-Status field. Origin servers MUST NOT generate the Proxy-Status field.
2.1. Proxy-Status Parameters 2.1. Proxy-Status Parameters
This section lists parameters that can be used on the members of This section lists parameters that can be used on the members of the
Proxy-Status. Proxy-Status field. Unrecognised parameters SHOULD be ignored.
2.1.1. next-hop
The "next-hop" parameter's value is a sf-string or sf-token that
identifies the intermediary or origin server selected (and used, if
contacted) for this response. Its contents might be a hostname, IP
address, or alias.
For example:
Proxy-Status: cdn.example.org; next-hop=backend.example.org
2.1.2. next-protocol
The "next-protocol" parameter's value indicates the ALPN protocol
identifier [RFC7301] used by the intermediary to connect to the next
hop. This is only applicable when that connection was actually
established.
The value MUST be either a sf-token or sf-binary. If the protocol
identifier is able to be expressed as a sf-token using UTF-8
encoding, that form MUST be used.
For example:
Proxy-Status: "proxy.example.org"; next-protocol=h2 2.1.1. error
2.1.3. error The "error" parameter's value is an sf-token that is a Proxy Error
Type. When present, it indicates that the proxy encountered an issue
when obtaining a response.
The "error" parameter's value is a sf-token that is a Proxy Error Unless a Proxy Error Type specifies otherwise, the presences of error
Type. When present, it indicates that the response was generated by often, but not always, indicates that response was generated by the
the proxy, not the origin server or any other upstream server. proxy, not the origin server or any other upstream server. For
example, a proxy might attempt to correct an error, or part of a
response might be forwarded before the error is encountered.
Section 2.3 lists the Proxy Error Types defined in this document; new Section 2.4 lists the Proxy Error Types defined in this document; new
ones can be defined using the procedure outlined in Section 2.4. ones can be defined using the procedure outlined in Section 2.5.
For example: For example:
HTTP/1.1 504 Gateway Timeout HTTP/1.1 504 Gateway Timeout
Proxy-Status: SomeCDN; error=connection_timeout Proxy-Status: SomeCDN; error=connection_timeout
indicates that this 504 response was generated by SomeCDN, due to a indicates that this 504 response was generated by SomeCDN, due to a
connection timeout when going forward. connection timeout when going forward.
Or: Or:
skipping to change at page 6, line 45 skipping to change at page 6, line 29
Proxy-Status: SomeReverseProxy; error=http_request_error Proxy-Status: SomeReverseProxy; error=http_request_error
indicates that this 429 Too Many Requests response was generated by indicates that this 429 Too Many Requests response was generated by
the intermediary, not the origin. the intermediary, not the origin.
When sending the error parameter, the most specific Proxy Error Type When sending the error parameter, the most specific Proxy Error Type
SHOULD be sent, provided that it accurately represents the error SHOULD be sent, provided that it accurately represents the error
condition. If an appropriate Proxy Error Type is not defined, there condition. If an appropriate Proxy Error Type is not defined, there
are a number of generic error types (e.g., proxy_internal_error, are a number of generic error types (e.g., proxy_internal_error,
http_protocol_error) that can be used. If they are not suitable, http_protocol_error) that can be used. If they are not suitable,
consider registering a new Proxy Error Type (see Section 2.4). consider registering a new Proxy Error Type (see Section 2.5).
Each Proxy Error Type has a Recommended HTTP Status Code. When Each Proxy Error Type has a Recommended HTTP Status Code. When
generating a HTTP response containing "error", its HTTP status code generating a HTTP response containing "error", its HTTP status code
SHOULD be set to the Recommended HTTP Status Code. However, there SHOULD be set to the Recommended HTTP Status Code. However, there
may be circumstances (e.g., for backwards compatibility with previous may be circumstances (e.g., for backwards compatibility with previous
behaviours) when another status code might be used. behaviours, a status code has already been sent) when another status
code might be used.
2.1.4. details Proxy Error Types can also define any number of extra parameters for
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 defined, it will be ignored.
The "details" parameter's value is a sf-string containing additional 2.1.2. next-hop
The "next-hop" parameter's value is an sf-string or sf-token that
identifies the intermediary or origin server selected (and used, if
contacted) for this response. It might be a hostname, IP address, or
alias.
For example:
Proxy-Status: cdn.example.org; next-hop=backend.example.org
2.1.3. next-protocol
The "next-protocol" parameter's value indicates the ALPN protocol
identifier [RFC7301] used by the intermediary to connect to the next
hop. This is only applicable when that connection was actually
established.
The value MUST be either an sf-token or sf-binary. If the protocol
identifier is able to be expressed as an sf-token using UTF-8
encoding, that form MUST be used.
For example:
Proxy-Status: "proxy.example.org"; next-protocol=h2
2.2. received-status
The "received-status" parameter's value indicates the HTTP status
code that the intermediary received from the next hop server.
The value MUST be an sf-integer.
For example:
Proxy-Status: ExampleProxy; received-status=200
2.2.1. details
The "details" parameter's value is an sf-string containing additional
information not captured anywhere else. This can include information not captured anywhere else. This can include
implementation-specific or deployment-specific information. implementation-specific or deployment-specific information.
For example: For example:
Proxy-Status: ExampleProxy; error="http_protocol_error"; Proxy-Status: ExampleProxy; error="http_protocol_error";
details="Malformed response header - space before colon" details="Malformed response header - space before colon"
2.2. Defining New Proxy-Status Parameters 2.3. Defining New Proxy-Status Parameters
New Proxy-Status Parameters can be defined by registering them in the New Proxy-Status Parameters can be defined by registering them in the
HTTP Proxy-Status Parameters registry. HTTP Proxy-Status Parameters registry.
Registration requests are reviewed and approved by a Designated Registration requests are reviewed and approved by a Designated
Expert, as per [RFC8126], Section 4.5. A specification document is Expert, as per [RFC8126], Section 4.5. A specification document is
appreciated, but not required. appreciated, but not required.
The Expert(s) should consider the following factors when evaluating The Expert(s) should consider the following factors when evaluating
requests: requests:
o Community feedback * Community feedback
o If the value is sufficiently well-defined * If the value is sufficiently well-defined
o Generic parameters are preferred over vendor-specific, * Generic parameters are preferred over vendor-specific,
application-specific or deployment-specific values. If a generic application-specific or deployment-specific values. If a generic
value cannot be agreed upon in the community, the parameter's name value cannot be agreed upon in the community, the parameter's name
should be correspondingly specific (e.g., with a prefix that should be correspondingly specific (e.g., with a prefix that
identifies the vendor, application or deployment). identifies the vendor, application or deployment).
* Parameter names should not conflict with registered extra
parameters in the Proxy Error Type Registry.
Registration requests should use the following template: Registration requests should use the following template:
o Name: [a name for the Proxy-Status Parameter that matches key] * Name: [a name for the Proxy-Status Parameter that matches key]
o Description: [a description of the parameter semantics and value] * Description: [a description of the parameter semantics and value]
o Reference: [to a specification defining this parameter] * Reference: [to a specification defining this parameter]
See the registry at https://iana.org/assignments/http-proxy-status See the registry at https://iana.org/assignments/http-proxy-status
[4] for details on where to send registration requests. (https://iana.org/assignments/http-proxy-status) for details on where
to send registration requests.
2.3. Proxy Error Types 2.4. Proxy Error Types
This section lists the Proxy Error Types defined by this document. This section lists the Proxy Error Types defined by this document.
See Section 2.4 for information about defining new Proxy Error Types. See Section 2.5 for information about defining new Proxy Error Types.
2.3.1. DNS Timeout 2.4.1. DNS Timeout
o Name: dns_timeout * Name: dns_timeout
o Description: The intermediary encountered a timeout when trying to * Description: The intermediary encountered a timeout when trying to
find an IP address for the next hop hostname. find an IP address for the next hop hostname.
o Extra Parameters: None. * Extra Parameters: None.
o Recommended HTTP status code: 504 * Recommended HTTP status code: 504
2.3.2. DNS Error 2.4.2. DNS Error
o Name: dns_error * Name: dns_error
o Description: The intermediary encountered a DNS error when trying * Description: The intermediary encountered a DNS error when trying
to find an IP address for the next hop hostname. to find an IP address for the next hop hostname.
o Extra Parameters: * Extra Parameters:
* rcode: A sf-string conveying the DNS RCODE that indicates the - rcode: A sf-string conveying the DNS RCODE that indicates the
error type. See [RFC8499], Section 3. error type. See [RFC8499], Section 3.
o Recommended HTTP status code: 502 * Recommended HTTP status code: 502
2.3.3. Destination Not Found 2.4.3. Destination Not Found
o Name: destination_not_found * Name: destination_not_found
o Description: The intermediary cannot determine the appropriate * Description: The intermediary cannot determine the appropriate
next hop to use for this request; for example, it may not be next hop to use for this request; for example, it may not be
configured. Note that this error is specific to gateways, which configured. Note that this error is specific to gateways, which
typically require specific configuration to identify the "backend" typically require specific configuration to identify the "backend"
server; forward proxies use in-band information to identify the server; forward proxies use in-band information to identify the
origin server. origin server.
o Extra Parameters: None. * Extra Parameters: None.
o Recommended HTTP status code: 500 * Recommended HTTP status code: 500
2.3.4. Destination Unavailable 2.4.4. Destination Unavailable
o Name: destination_unavailable * Name: destination_unavailable
o Description: The intermediary considers the next hop to be * Description: The intermediary considers the next hop to be
unavailable; e.g., recent attempts to communicate with it may have unavailable; e.g., recent attempts to communicate with it may have
failed, or a health check may indicate that it is down. failed, or a health check may indicate that it is down.
o Extra Parameters: None. * Extra Parameters: None.
o Recommended HTTP status code: 503 * Recommended HTTP status code: 503
2.3.5. Destination IP Prohibited 2.4.5. Destination IP Prohibited
o Name: destination_ip_prohibited * Name: destination_ip_prohibited
o Description: The intermediary is configured to prohibit * Description: The intermediary is configured to prohibit
connections to the next hop IP address. connections to the next hop IP address.
o Extra Parameters: None. * Extra Parameters: None.
o Recommended HTTP status code: 502 * Recommended HTTP status code: 502
2.3.6. Destination IP Unroutable 2.4.6. Destination IP Unroutable
o Name: destination_ip_unroutable * Name: destination_ip_unroutable
o Description: The intermediary cannot find a route to the next hop * Description: The intermediary cannot find a route to the next hop
IP address. IP address.
o Extra Parameters: None. * Extra Parameters: None.
o Recommended HTTP status code: 502 * Recommended HTTP status code: 502
2.3.7. Connection Refused 2.4.7. Connection Refused
o Name: connection_refused * Name: connection_refused
o Description: The intermediary's connection to the next hop was * Description: The intermediary's connection to the next hop was
refused. refused.
o Extra Parameters: None. * Extra Parameters: None.
o Recommended HTTP status code: 502 * Recommended HTTP status code: 502
2.3.8. Connection Terminated 2.4.8. Connection Terminated
o Name: connection_terminated * Name: connection_terminated
o Description: The intermediary's connection to the next hop was * Description: The intermediary's connection to the next hop was
closed before any part of the response was received. If some part closed before complete response was received.
was received, see http_response_incomplete.
o Extra Parameters: None. * Extra Parameters: None.
o Recommended HTTP status code: 502 * Recommended HTTP status code: 502
2.3.9. Connection Timeout * Notes: Responses with this error type might not have been
generated by the intermediary.
o Name: connection_timeout 2.4.9. Connection Timeout
o Description: The intermediary's attempt to open a connection to * Name: connection_timeout
* Description: The intermediary's attempt to open a connection to
the next hop timed out. the next hop timed out.
o Extra Parameters: None. * Extra Parameters: None.
o Recommended HTTP status code: 504 * Recommended HTTP status code: 504
2.3.10. Connection Read Timeout 2.4.10. Connection Read Timeout
o Name: connection_read_timeout * Name: connection_read_timeout
o Description: The intermediary was expecting data on a connection * Description: The intermediary was expecting data on a connection
(e.g., part of a response), but did not receive any new data in a (e.g., part of a response), but did not receive any new data in a
configured time limit. configured time limit.
o Extra Parameters: None. * Extra Parameters: None.
o Recommended HTTP status code: 504 * Recommended HTTP status code: 504
2.3.11. Connection Write Timeout * Notes: Responses with this error type might not have been
generated by the intermediary.
o Name: connection_write_timeout 2.4.11. Connection Write Timeout
o Description: The intermediary was attempting to write data to a * Name: connection_write_timeout
* Description: The intermediary was attempting to write data to a
connection, but was not able to (e.g., because its buffers were connection, but was not able to (e.g., because its buffers were
full). full).
o Extra Parameters: None. * Extra Parameters: None.
o Recommended HTTP status code: 504 * Recommended HTTP status code: 504
2.3.12. Connection Limit Reached * Notes: Responses with this error type might not have been
generated by the intermediary.
o Name: connnection_limit_reached 2.4.12. Connection Limit Reached
o Description: The intermediary is configured to limit the number of * Name: connection_limit_reached
* Description: The intermediary is configured to limit the number of
connections it has to the next hop, and that limit has been connections it has to the next hop, and that limit has been
passed. passed.
o Extra Parameters: None. * Extra Parameters: None.
o Recommended HTTP status code: 503
2.3.13. TLS Protocol Error * Recommended HTTP status code: 503
o Name: tls_protocol_error 2.4.13. TLS Protocol Error
o Description: The intermediary encountered a TLS error when * Name: tls_protocol_error
* Description: The intermediary encountered a TLS error when
communicating with the next hop, either during handshake or communicating with the next hop, either during handshake or
afterwards. afterwards.
o Extra Parameters: None. * Extra Parameters: None.
o Recommended HTTP status code: 502 * Recommended HTTP status code: 502
* Notes: Responses with this error type might not have been
generated by the intermediary.
Note that additional information about the error can be recorded in Note that additional information about the error can be recorded in
the details parameter (as is the case for all errors). the details parameter (as is the case for all errors).
2.3.14. TLS Certificate Error 2.4.14. TLS Certificate Error
o Name: tls_certificate_error * Name: tls_certificate_error
o Description: The intermediary encountered an error when verifying * Description: The intermediary encountered an error when verifying
the certificate presented by the next hop. the certificate presented by the next hop.
o Extra Parameters: None. * Extra Parameters: None.
o Recommended HTTP status code: 502 * Recommended HTTP status code: 502
Note that additional information about the error can be recorded in Note that additional information about the error can be recorded in
the details parameter (as is the case for all errors). the details parameter (as is the case for all errors).
2.3.15. TLS Alert Received 2.4.15. TLS Alert Received
o Name: tls_alert_received * Name: tls_alert_received
o Description: The intermediary received a TLS alert from the next * Description: The intermediary received a TLS alert from the next
hop. hop.
o Extra Parameters: * Extra Parameters:
* alert_message: a sf-token containing the applicable description - alert-message: an sf-token containing the applicable
string from the TLS Alerts registry. description string from the TLS Alerts registry.
o Recommended HTTP status code: 502 * Recommended HTTP status code: 502
2.3.16. HTTP Request Error * Notes: Responses with this error type might not have been
generated by the intermediary.
o Name: http_request_error 2.4.16. HTTP Request Error
o Description: The intermediary is generating a client (4xx) * Name: http_request_error
* Description: The intermediary is generating a client (4xx)
response on the origin's behalf. Applicable status codes include response on the origin's behalf. Applicable status codes include
(but are not limited to) 400, 403, 405, 406, 408, 411, 413, 414, (but are not limited to) 400, 403, 405, 406, 408, 411, 413, 414,
415, 416, 417, 429. 415, 416, 417, 429.
o Extra Parameters: * Extra Parameters:
* status_code: a sf-integer containing the generated status code. - status-code: an sf-integer containing the generated status
code.
* status_phrase: a sf-string containing the generated status - status-phrase: an sf-string containing the generated status
phrase. phrase.
o Recommended HTTP status code: The applicable 4xx status code * Recommended HTTP status code: The applicable 4xx status code
This type helps distinguish between responses generated by * Notes: This type helps distinguish between responses generated by
intermediaries from those generated by the origin. intermediaries from those generated by the origin.
2.3.17. HTTP Request Denied 2.4.17. HTTP Request Denied
o Name: http_request_denied * Name: http_request_denied
o Description: The intermediary rejected the HTTP request based on * Description: The intermediary rejected the HTTP request based on
its configuration and/or policy settings. The request wasn't its configuration and/or policy settings. The request wasn't
forwarded to the next hop. forwarded to the next hop.
o Extra Parameters: None. * Extra Parameters: None.
o Recommended HTTP status code: 403 * Recommended HTTP status code: 403
2.3.18. HTTP Incomplete Response 2.4.18. HTTP Incomplete Response
o Name: http_response_incomplete * Name: http_response_incomplete
o Description: The intermediary received an incomplete response to * Description: The intermediary received an incomplete response to
the request from the next hop. the request from the next hop.
o Extra Parameters: None. * Extra Parameters: None.
o Recommended HTTP status code: 502 * Recommended HTTP status code: 502
2.3.19. HTTP Response Header Block Too Large * Notes: Responses with this error type might not have been
generated by the intermediary.
o Name: http_response_header_block_size 2.4.19. HTTP Response Header Section Too Large
o Description: The intermediary received a response to the request * Name: http_response_header_section_size
whose header block was considered too large.
o Extra Parameters: * Description: The intermediary received a response to the request
whose header section was considered too large.
* header_block_size: a sf-integer indicating how large the * Extra Parameters:
- header-section-size: an sf-integer indicating how large the
headers received were. Note that they might not be complete; headers received were. Note that they might not be complete;
i.e., the intermediary may have discarded or refused additional i.e., the intermediary may have discarded or refused additional
data. data.
o Recommended HTTP status code: 502 * Recommended HTTP status code: 502
2.3.20. HTTP Response Header Too Large * Notes: Responses with this error type might not have been
generated by the intermediary.
o Name: http_response_header_size 2.4.20. HTTP Response Header Too Large
o Description: The intermediary received a response to the request * Name: http_response_header_size
* Description: The intermediary received a response to the request
containing an individual header line that was considered too containing an individual header line that was considered too
large. large.
o Extra Parameters: * Extra Parameters:
* header_name: a sf-string indicating the name of the header that - header-name: an sf-string indicating the name of the header
triggered the error. that triggered the error.
o Recommended HTTP status code: 502 - header-size: an sf-integer indicating the size of the header
that triggered the error.
2.3.21. HTTP Response Body Too Large * Recommended HTTP status code: 502
o Name: http_response_body_size * Notes: Responses with this error type might not have been
generated by the intermediary.
o Description: The intermediary received a response to the request 2.4.21. HTTP Response Body Too Large
* Name: http_response_body_size
* Description: The intermediary received a response to the request
whose body was considered too large. whose body was considered too large.
o Extra Parameters: * Extra Parameters:
* body_size: a sf-integer indicating how large the body received - body-size: an sf-integer indicating how large the body received
was. Note that it may not have been complete; i.e., the was. Note that it may not have been complete; i.e., the
intermediary may have discarded or refused additional data. intermediary may have discarded or refused additional data.
o Recommended HTTP status code: 502 * Recommended HTTP status code: 502
2.3.22. HTTP Response Transfer-Coding Error * Notes: Responses with this error type might not have been
generated by the intermediary.
o Name: http_response_transfer_coding 2.4.22. HTTP Response Trailer Section Too Large
o Description: The intermediary encountered an error decoding the * Name: http_response_trailer_section_size
* Description: The intermediary received a response to the request
whose trailer section was considered too large.
* Extra Parameters:
- trailer-section-size: an sf-integer indicating how large the
trailers received were. Note that they might not be complete;
i.e., the intermediary may have discarded or refused additional
data.
* Recommended HTTP status code: 502
* Notes: Responses with this error type might not have been
generated by the intermediary.
2.4.23. HTTP Response Trailer Too Large
* Name: http_response_trailer_size
* Description: The intermediary received a response to the request
containing an individual trailer line that was considered too
large.
* Extra Parameters:
- trailer-name: an sf-string indicating the name of the trailer
that triggered the error.
- trailer-size: an sf-integer indicating the size of the trailer
that triggered the error.
* Recommended HTTP status code: 502
* Notes: Responses with this error type might not have been
generated by the intermediary.
2.4.24. HTTP Response Transfer-Coding Error
* Name: http_response_transfer_coding
* Description: The intermediary encountered an error decoding the
transfer-coding of the response. transfer-coding of the response.
o Extra Parameters: * Extra Parameters:
* coding: a sf-token containing the specific coding that caused - coding: an sf-token containing the specific coding that caused
the error. the error.
o Recommended HTTP status code: 502 * Recommended HTTP status code: 502
2.3.23. HTTP Response Content-Coding Error * Notes: Responses with this error type might not have been
generated by the intermediary.
o Name: http_response_content_coding 2.4.25. HTTP Response Content-Coding Error
o Description: The intermediary encountered an error decoding the * Name: http_response_content_coding
* Description: The intermediary encountered an error decoding the
content-coding of the response. content-coding of the response.
o Extra Parameters: * Extra Parameters:
* coding: a sf-token containing the specific coding that caused - coding: an sf-token containing the specific coding that caused
the error. the error.
o Recommended HTTP status code: 502 * Recommended HTTP status code: 502
2.3.24. HTTP Response Timeout * Notes: Responses with this error type might not have been
generated by the intermediary.
o Name: http_response_timeout 2.4.26. HTTP Response Timeout
o Description: The intermediary reached a configured time limit * Name: http_response_timeout
* Description: The intermediary reached a configured time limit
waiting for the complete response. waiting for the complete response.
o Extra Parameters: None. * Extra Parameters: None.
o Recommended HTTP status code: 504 * Recommended HTTP status code: 504
2.3.25. HTTP Upgrade Failed * Notes: Responses with this error type might not have been
generated by the intermediary.
o Name: http_upgrade_failed 2.4.27. HTTP Upgrade Failed
o Description: The HTTP Upgrade between the intermediary and the * Name: http_upgrade_failed
* Description: The HTTP Upgrade between the intermediary and the
next hop failed. next hop failed.
o Extra Parameters: None. * Extra Parameters: None.
o Recommended HTTP status code: 502 * Recommended HTTP status code: 502
2.3.26. HTTP Protocol Error 2.4.28. HTTP Protocol Error
o Name: http_protocol_error * Name: http_protocol_error
o Description: The intermediary encountered a HTTP protocol error * Description: The intermediary encountered a HTTP protocol error
when communicating with the next hop. This error should only be when communicating with the next hop. This error should only be
used when a more specific one is not defined. used when a more specific one is not defined.
o Extra Parameters: None. * Extra Parameters: None.
o Recommended HTTP status code: 502 * Recommended HTTP status code: 502
* Notes: Responses with this error type might not have been
generated by the intermediary.
Note that additional information about the error can be recorded in Note that additional information about the error can be recorded in
the details parameter (as is the case for all errors). the details parameter (as is the case for all errors).
2.3.27. Proxy Internal Response 2.4.29. Proxy Internal Response
o Name: proxy_internal_response * Name: proxy_internal_response
o Description: The intermediary generated the response locally, * Description: The intermediary generated the response locally,
without attempting to connect to the next hop (e.g. in response to without attempting to connect to the next hop (e.g. in response to
a request to a debug endpoint terminated at the intermediary). a request to a debug endpoint terminated at the intermediary).
o Extra Parameters: None. * Extra Parameters: None.
o Recommended HTTP status code: * Recommended HTTP status code:
2.3.28. Proxy Internal Error 2.4.30. Proxy Internal Error
o Name: proxy_internal_error * Name: proxy_internal_error
o Description: The intermediary encountered an internal error * Description: The intermediary encountered an internal error
unrelated to the origin. unrelated to the origin.
o Extra Parameters: None * Extra Parameters: None
o Recommended HTTP status code: 500 * Recommended HTTP status code: 500
Note that additional information about the error can be recorded in Note that additional information about the error can be recorded in
the details parameter (as is the case for all errors). the details parameter (as is the case for all errors).
2.3.29. Proxy Configuration Error 2.4.31. Proxy Configuration Error
o Name: proxy_configuration_error * Name: proxy_configuration_error
o Description: The intermediary encountered an error regarding its
* Description: The intermediary encountered an error regarding its
configuration. configuration.
o Extra Parameters: None * Extra Parameters: None
o Recommended HTTP status code: 500 * Recommended HTTP status code: 500
Note that additional information about the error can be recorded in Note that additional information about the error can be recorded in
the details parameter (as is the case for all errors). the details parameter (as is the case for all errors).
2.3.30. Proxy Loop Detected 2.4.32. Proxy Loop Detected
o Name: proxy_loop_detected * Name: proxy_loop_detected
o Description: The intermediary tried to forward the request to * Description: The intermediary tried to forward the request to
itself, or a loop has been detected using different means (e.g. itself, or a loop has been detected using different means (e.g.
[RFC8586]). [RFC8586]).
o Extra Parameters: None. * Extra Parameters: None.
o Recommended HTTP status code: 502 * Recommended HTTP status code: 502
2.4. Defining New Proxy Error Types 2.5. Defining New Proxy Error Types
New Proxy Error Types can be defined by registering them in the HTTP New Proxy Error Types can be defined by registering them in the HTTP
Proxy Error Types registry. Proxy Error Types registry.
Registration requests are reviewed and approved by a Designated Registration requests are reviewed and approved by a Designated
Expert, as per [RFC8126], Section 4.5. A specification document is Expert, as per [RFC8126], Section 4.5. A specification document is
appreciated, but not required. appreciated, but not required.
The Expert(s) should consider the following factors when evaluating The Expert(s) should consider the following factors when evaluating
requests: requests:
o Community feedback * Community feedback
o If the value is sufficiently well-defined
o Generic types are preferred over vendor-specific, application- * If the value is sufficiently well-defined
* Generic types are preferred over vendor-specific, application-
specific or deployment-specific values. If a generic value cannot specific or deployment-specific values. If a generic value cannot
be agreed upon in the community, the types's name should be be agreed upon in the community, the types's name should be
correspondingly specific (e.g., with a prefix that identifies the correspondingly specific (e.g., with a prefix that identifies the
vendor, application or deployment). vendor, application or deployment).
* Extra Parameters should not conflict with registered Proxy-Status
parameters.
Registration requests should use the following template: Registration requests should use the following template:
o Name: [a name for the Proxy Error Type that matches sf-token] * Name: [a name for the Proxy Error Type that matches sf-token]
o Description: [a description of the conditions that generate the
* Description: [a description of the conditions that generate the
Proxy Error Type] Proxy Error Type]
o Extra Parameters: [zero or more optional parameters, along with * Extra Parameters: [zero or more optional parameters, along with
their allowable type(s)] their allowable type(s)]
o Recommended HTTP status code: [the appropriate HTTP status code * Recommended HTTP status code: [the appropriate HTTP status code
for this entry] for this entry]
* Notes: [optional]
If the Proxy Error Type might occur in responses that are not
generated by the intermediary -- for example, when the error is
detected during response content processing and a Proxy-Status
trailer field is appended -- that SHOULD be explained in the Notes.
See the registry at https://iana.org/assignments/http-proxy-status See the registry at https://iana.org/assignments/http-proxy-status
[5] for details on where to send registration requests. (https://iana.org/assignments/http-proxy-status) for details on where
to send registration requests.
3. IANA Considerations 3. IANA Considerations
Upon publication, please create the HTTP Proxy-Status Parameters Upon publication, please create the HTTP Proxy-Status Parameters
registry and the HTTP Proxy Error Types registry at registry and the HTTP Proxy Error Types registry at
https://iana.org/assignments/http-proxy-statuses [6] and populate https://iana.org/assignments/http-proxy-statuses
them with the types defined in Section 2.1 and Section 2.3 (https://iana.org/assignments/http-proxy-statuses) and populate them
respectively; see Section 2.2 and Section 2.4 for its associated with the types defined in Section 2.1 and Section 2.4 respectively;
procedures. see Section 2.3 and Section 2.5 for its associated procedures.
4. Security Considerations 4. Security Considerations
One of the primary security concerns when using Proxy-Status is One of the primary security concerns when using Proxy-Status is
leaking information that might aid an attacker. For example, leaking information that might aid an attacker. For example,
information about the intermediary's configuration and back-end information about the intermediary's configuration and back-end
topology can be exposed. topology can be exposed.
As a result, care needs to be taken when deciding to generate a As a result, care needs to be taken when deciding to generate a
Proxy-Status field. Note that intermediaries are not required to Proxy-Status field. Note that intermediaries are not required to
generate a Proxy-Status field in any response, and can conditionally generate a Proxy-Status field in any response, and can conditionally
generate them based upon request attributes (e.g., authentication generate them based upon request attributes (e.g., authentication
tokens, IP address). tokens, IP address).
Likewise, generation of all parameters is optional. Likewise, generation of all parameters is optional.
5. References 5. References
5.1. Normative References 5.1. Normative References
[I-D.ietf-httpbis-header-structure]
Nottingham, M. and P. Kamp, "Structured Field Values for
HTTP", draft-ietf-httpbis-header-structure-19 (work in
progress), June 2020.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>. <https://www.rfc-editor.org/info/rfc2119>.
[RFC7301] Friedl, S., Popov, A., Langley, A., and E. Stephan,
"Transport Layer Security (TLS) Application-Layer Protocol
Negotiation Extension", RFC 7301, DOI 10.17487/RFC7301,
July 2014, <https://www.rfc-editor.org/info/rfc7301>.
[RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for [RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for
Writing an IANA Considerations Section in RFCs", BCP 26, Writing an IANA Considerations Section in RFCs", BCP 26,
RFC 8126, DOI 10.17487/RFC8126, June 2017, RFC 8126, DOI 10.17487/RFC8126, June 2017,
<https://www.rfc-editor.org/info/rfc8126>. <https://www.rfc-editor.org/info/rfc8126>.
[RFC8499] Hoffman, P., Sullivan, A., and K. Fujiwara, "DNS
Terminology", BCP 219, RFC 8499, DOI 10.17487/RFC8499,
January 2019, <https://www.rfc-editor.org/info/rfc8499>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>. May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC8499] Hoffman, P., Sullivan, A., and K. Fujiwara, "DNS [I-D.ietf-httpbis-header-structure]
Terminology", BCP 219, RFC 8499, DOI 10.17487/RFC8499, Nottingham, M. and P. Kamp, "Structured Field Values for
January 2019, <https://www.rfc-editor.org/info/rfc8499>. HTTP", Work in Progress, Internet-Draft, draft-ietf-
httpbis-header-structure-19, 3 June 2020,
<http://www.ietf.org/internet-drafts/draft-ietf-httpbis-
header-structure-19.txt>.
[RFC7301] Friedl, S., Popov, A., Langley, A., and E. Stephan,
"Transport Layer Security (TLS) Application-Layer Protocol
Negotiation Extension", RFC 7301, DOI 10.17487/RFC7301,
July 2014, <https://www.rfc-editor.org/info/rfc7301>.
5.2. Informative References 5.2. Informative References
[RFC8586] Ludin, S., Nottingham, M., and N. Sullivan, "Loop [RFC8586] Ludin, S., Nottingham, M., and N. Sullivan, "Loop
Detection in Content Delivery Networks (CDNs)", RFC 8586, Detection in Content Delivery Networks (CDNs)", RFC 8586,
DOI 10.17487/RFC8586, April 2019, DOI 10.17487/RFC8586, April 2019,
<https://www.rfc-editor.org/info/rfc8586>. <https://www.rfc-editor.org/info/rfc8586>.
5.3. URIs
[1] https://lists.w3.org/Archives/Public/ietf-http-wg/
[2] https://httpwg.org/
[3] https://github.com/httpwg/http-extensions/labels/proxy-status
[4] https://iana.org/assignments/http-proxy-status
[5] https://iana.org/assignments/http-proxy-status
[6] https://iana.org/assignments/http-proxy-statuses
Authors' Addresses Authors' Addresses
Mark Nottingham Mark Nottingham
Fastly Fastly
made in Prahran VIC
Prahran, VIC
Australia Australia
Email: mnot@mnot.net Email: mnot@mnot.net
URI: https://www.mnot.net/ URI: https://www.mnot.net/
Piotr Sikora Piotr Sikora
Google Google
Email: piotrsikora@google.com Email: piotrsikora@google.com
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