Internet Assigned Numbers Authority

Hypertext Transfer Protocol (HTTP) Proxy-Status

Created
2021-10-22
Last Updated
2022-06-10
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HTTP Proxy-Status Parameters

Registration Procedure(s)
Expert Review
Expert(s)
Unassigned
Reference
[RFC9209]
Available Formats

CSV
Name Description Reference
error The error parameter's value is a Token that is a proxy error type. When present, it indicates that the intermediary encountered an issue when obtaining this response. [RFC9209]
next-hop The next-hop parameter's value is a String or Token that identifies the intermediary or origin server selected (and used, if contacted) to obtain this response. It might be a hostname, IP address, or alias. [RFC9209]
next-protocol The next-protocol parameter's value indicates the Application-Layer Protocol Negotiation (ALPN) protocol identifier [RFC7301] of the protocol used by the intermediary to connect to the next hop when obtaining this response. [RFC9209]
received-status The received-status parameter's value indicates the HTTP status code that the intermediary received from the next-hop server when obtaining this response. [RFC9209]
details The details parameter's value is a String containing additional information not captured anywhere else. This can include implementation-specific or deployment-specific information. [RFC9209]

HTTP Proxy Error Types

Registration Procedure(s)
Expert Review
Expert(s)
Unassigned
Reference
[RFC9209]
Available Formats

CSV
Name Description Extra Parameters Recommended HTTP Status Code Response Only Generated by Intermediaries Reference Notes
dns_timeout The intermediary encountered a timeout when trying to find an IP address for the next-hop hostname. None 504 true [RFC9209]
dns_error The intermediary encountered a DNS error when trying to find an IP address for the next-hop hostname.

- rcode: A String conveying the DNS RCODE that indicates the error type. See [RFC8499], Section 3.

- info-code: An Integer conveying the Extended DNS Error Code INFO-CODE. See [RFC8914].

502 true [RFC9209]
destination_not_found The intermediary cannot determine the appropriate next hop to use for this request; for example, it may not be configured. Note that this error is specific to gateways, which typically require specific configuration to identify the "backend" server; forward proxies use in-band information to identify the origin server. None 500 true [RFC9209]
destination_unavailable The intermediary considers the next hop to be unavailable; e.g., recent attempts to communicate with it may have failed, or a health check may indicate that it is down. None 503 true [RFC9209]
destination_ip_prohibited The intermediary is configured to prohibit connections to the next-hop IP address. None 502 true [RFC9209]
destination_ip_unroutable The intermediary cannot find a route to the next-hop IP address. None 502 true [RFC9209]
connection_refused The intermediary's connection to the next hop was refused. None 502 true [RFC9209]
connection_terminated The intermediary's connection to the next hop was closed before a complete response was received. None 502 false [RFC9209]
connection_timeout The intermediary's attempt to open a connection to the next hop timed out. None 504 true [RFC9209]
connection_read_timeout The intermediary was expecting data on a connection (e.g., part of a response) but did not receive any new data in a configured time limit. None 504 false [RFC9209]
connection_write_timeout The intermediary was attempting to write data to a connection but was not able to (e.g., because its buffers were full). None 504 false [RFC9209]
connection_limit_reached The intermediary is configured to limit the number of connections it has to the next hop, and that limit has been exceeded. None 503 true [RFC9209]
tls_protocol_error The intermediary encountered a TLS error when communicating with the next hop, either during the handshake or afterwards. None 502 false [RFC9209] Not appropriate when a TLS alert is received; see tls_alert_received.
tls_certificate_error The intermediary encountered an error when verifying the certificate presented by the next hop. None 502 true [RFC9209]
tls_alert_received The intermediary received a TLS alert from the next hop.

- alert-id: An Integer containing the applicable value from the [TLS Alerts registry]. See [RFC8446].

- alert-message: A Token or String containing the applicable description string from the [TLS Alerts registry]. See [RFC8446].

502 false [RFC9209]
http_request_error The intermediary is generating a client (4xx) response on the origin's behalf. Applicable status codes include (but are not limited to) 400, 403, 405, 406, 408, 411, 413, 414, 415, 416, 417, and 429.

- status-code: An Integer containing the generated status code.

- status-phrase: A String containing the generated status phrase.

The applicable 4xx status code true [RFC9209] This type helps distinguish between responses generated by intermediaries from those generated by the origin.
http_request_denied The intermediary rejected the HTTP request based on its configuration and/or policy settings. The request wasn't forwarded to the next hop. None 403 true [RFC9209]
http_response_incomplete The intermediary received an incomplete response to the request from the next hop. None 502 false [RFC9209]
http_response_header_section_size The intermediary received a response to the request whose header section was considered too large. - header-section-size: An Integer indicating how large the received headers were. Note that they might not be complete; i.e., the intermediary may have discarded or refused additional data. 502 false [RFC9209]
http_response_header_size The intermediary received a response to the request containing an individual header field line that was considered too large.

- header-name: A String indicating the name of the header field that triggered the error.

- header-size: An Integer indicating the size of the header field that triggered the error.

502 false [RFC9209]
http_response_body_size The intermediary received a response to the request whose body was considered too large. - body-size: An Integer indicating how large the received body was. Note that it may not have been complete; i.e., the intermediary may have discarded or refused additional data. 502 false [RFC9209]
http_response_trailer_section_size The intermediary received a response to the request whose trailer section was considered too large. - trailer-section-size: An Integer indicating how large the received trailers were. Note that they might not be complete; i.e., the intermediary may have discarded or refused additional data. 502 false [RFC9209]
http_response_trailer_size The intermediary received a response to the request containing an individual trailer field line that was considered too large.

- trailer-name: A String indicating the name of the trailer field that triggered the error.

- trailer-size: An Integer indicating the size of the trailer field that triggered the error.

502 false [RFC9209]
http_response_transfer_coding The intermediary encountered an error decoding the transfer coding of the response. - coding: A Token containing the specific coding (from the [HTTP Transfer Coding Registry]) that caused the error. 502 false [RFC9209]
http_response_content_coding The intermediary encountered an error decoding the content coding of the response. - coding: A Token containing the specific coding (from the [HTTP Content Coding Registry]) that caused the error. 502 false [RFC9209]
http_response_timeout The intermediary reached a configured time limit waiting for the complete response. None 504 false [RFC9209]
http_upgrade_failed The process of negotiating an upgrade of the HTTP version between the intermediary and the next hop failed. None 502 true [RFC9209]
http_protocol_error The intermediary encountered an HTTP protocol error when communicating with the next hop. This error should only be used when a more specific one is not defined. None 502 false [RFC9209]
proxy_internal_response The intermediary generated the response itself without attempting to connect to the next hop. None The most appropriate status code for the response true [RFC9209]
proxy_internal_error The intermediary encountered an internal error unrelated to the origin. None 500 true [RFC9209]
proxy_configuration_error The intermediary encountered an error regarding its configuration. None 500 true [RFC9209]
proxy_loop_detected The intermediary tried to forward the request to itself, or a loop has been detected using different means (e.g., [RFC8586]). None 502 true [RFC9209]