HTTP communication usually takes place over TCP/IP connections. The
   default port is TCP 80, but other ports can be used. This does not
   preclude HTTP from being implemented on top of any other protocol on
   the Internet, or on other networks. HTTP only presumes a reliable
   transport; any protocol that provides such guarantees can be used;
   the mapping of the HTTP/1.1 request and response structures onto the
   transport data units of the protocol in question is outside the scope
   of this specification.

   In HTTP/1.0, most implementations used a new connection for each
   request/response exchange. In HTTP/1.1, a connection may be used for
   one or more request/response exchanges, although connections may be
   closed for a variety of reasons (see section 8.1).

2 Notational Conventions and Generic Grammar

2.1 Augmented BNF

   All of the mechanisms specified in this document are described in
   both prose and an augmented Backus-Naur Form (BNF) similar to that
   used by RFC 822 [9]. Implementers will need to be familiar with the
   notation in order to understand this specification. The augmented BNF
   includes the following constructs:






 
RFC 2068                        HTTP/1.1                    January 1997


name = definition
     The name of a rule is simply the name itself (without any enclosing
     "<" and ">") and is separated from its definition by the equal "="
     character. Whitespace is only significant in that indentation of
     continuation lines is used to indicate a rule definition that spans
     more than one line. Certain basic rules are in uppercase, such as
     SP, LWS, HT, CRLF, DIGIT, ALPHA, etc. Angle brackets are used
     within definitions whenever their presence will facilitate
     discerning the use of rule names.

"literal"
     Quotation marks surround literal text. Unless stated otherwise, the
          text is case-insensitive.

rule1 | rule2
     Elements separated by a bar ("|") are alternatives, e.g., "yes |
     no" will accept yes or no.

(rule1 rule2)
     Elements enclosed in parentheses are treated as a single element.
     Thus, "(elem (foo | bar) elem)" allows the token sequences "elem
     foo elem" and "elem bar elem".

*rule
     The character "*" preceding an element indicates repetition. The
     full form is "*element" indicating at least  and at most
      occurrences of element. Default values are 0 and infinity so
     that "*(element)" allows any number, including zero; "1*element"
     requires at least one; and "1*2element" allows one or two.

[rule]
     Square brackets enclose optional elements; "[foo bar]" is
     equivalent to "*1(foo bar)".

N rule
     Specific repetition: "(element)" is equivalent to
     "*(element)"; that is, exactly  occurrences of (element).
     Thus 2DIGIT is a 2-digit number, and 3ALPHA is a string of three
     alphabetic characters.

#rule
     A construct "#" is defined, similar to "*", for defining lists of
     elements. The full form is "#element " indicating at least
      and at most  elements, each separated by one or more commas
     (",") and optional linear whitespace (LWS). This makes the usual
     form of lists very easy; a rule such as "( *LWS element *( *LWS ","
     *LWS element )) " can be shown as "1#element". Wherever this
     construct is used, null elements are allowed, but do not contribute




 
RFC 2068                        HTTP/1.1                    January 1997


     to the count of elements present.  That is, "(element), , (element)
     " is permitted, but counts as only two elements. Therefore, where
     at least one element is required, at least one non-null element
     must be present. Default values are 0 and infinity so that
     "#element" allows any number, including zero; "1#element" requires
     at least one; and "1#2element" allows one or two.

; comment
     A semi-colon, set off some distance to the right of rule text,
     starts a comment that continues to the end of line. This is a