* 歴史 ** SSTP [REFS[ - [1] [CITE[伺か - SSTPプロトコル]] ([TIME[2007-09-14 12:30:05 +09:00]] 版) ]REFS] [2] > 420 Refuse ゴーストが SSTP の受信を拒否 ** PEP (HTTP) [REFS[ - [3] [CITE[PEP - an Extension Mechanism for HTTP]] ([TIME[1998-04-07 21:31:46 +09:00]] 版) ]REFS] > 420 Policy Not Fulfilled ** SIP [REFS[ - [4] [CITE@en[RFC 3261 - SIP: Session Initiation Protocol]] ([TIME[2012-01-09 20:48:30 +09:00]] 版) ]REFS] >420 Bad Extension [5] [CITE[Error Codes & Responses | Twitter Developers]] ( ([TIME[2012-02-19 13:24:15 +09:00]] 版)) [6] [CITE[Rate Limiting | Twitter Developers]] ( ([TIME[2012-08-17 02:45:08 +09:00]] 版)) [7] [CITE@en[RFC 2660 - The Secure HyperText Transfer Protocol]] ( ([TIME[2013-07-20 22:21:48 +09:00]] 版)) [8] [CITE@en[List of HTTP status codes - Wikipedia, the free encyclopedia]] ( ([TIME[2013-10-01 11:44:11 +09:00]] 版)) [9] [CITE@en[RFC 2660 - The Secure HyperText Transfer Protocol]] ( ([TIME[2014-11-09 14:12:37 +09:00]] 版)) [10] [CITE[PEP - an Extension Mechanism for HTTP]] ( ([TIME[1998-04-08 06:31:46 +09:00]] 版)) [FIG(quote)[ [FIGCAPTION[ [11] [CITE[Connecting to a streaming endpoint | Twitter Developers]] ([TIME[2015-03-05 11:50:39 +09:00]] 版) ]FIGCAPTION] > Rate limited clients will receive HTTP 420 responses for all connection requests. ]FIG] [FIG(quote)[ [FIGCAPTION[ [12] [CITE[Connecting to a streaming endpoint | Twitter Developers]] ([TIME[2015-03-05 11:50:39 +09:00]] 版) ]FIGCAPTION] > 420 Rate Limited > The client has connected too frequently. For example, an endpoint returns this status if: > A client makes too many login attempts in a short period of time. > Too many copies of an application attempt to authenticate with the same credentials. ]FIG]