Network Working Group R. Fielding Request for Comments: 2616 ...

needs of those who build web applications that require highreliability and, failing that, at least reliable indications offailure.HTTP communication usually takes place over TCP/IP connections. Thedefault port is TCP 80 [19], but other ports can be used. This doesnot preclude HTTP from being implemented on top of any other protocolon the Internet, or on other networks. HTTP only presumes a reliabletransport; any protocol that provides such guarantees can be used;the mapping of the HTTP/1.1 request and response structures onto thetransport data units of the protocol in question is outside the scopeof this specification.Fielding, et al. Standards Track [Page 13]RFC 2616 HTTP/1.1 June 1999In HTTP/1.0, most implementations used a new connection for eachrequest/response exchange. In HTTP/1.1, a connection may be used forone or more request/response exchanges, although connections may beclosed for a variety of reasons (see section 8.1).2 Notational Conventions and Generic Grammar2.1 Augmented BNFAll of the mechanisms specified in this document are described inboth prose and an augmented Backus-Naur Form (BNF) similar to thatused by RFC 822 [9]. Implementors will need to be familiar with thenotation in order to understand this specification. The augmented BNFincludes the following constructs:name = definitionThe name of a rule is simply the name itself (without anyenclosing "") and is separated from its definition by theequal "=" character. White space is only significant in thatindentation of continuation lines is used to indicate a ruledefinition that spans more than one line. Certain basic rules arein uppercase, such as SP, LWS, HT, CRLF, DIGIT, ALPHA, etc. Anglebrackets are used within definitions whenever their presence willfacilitate discerning the use of rule names."literal"Quotation marks surround literal text. Unless stated otherwise,the text is case-insensitive.rule1 | rule2