\section{Entity}
\label{sec:entity}

Request and Response messages MAY transfer an entity if not otherwise
restricted by the request method or response status code.  An entity
consists of entity-header fields and an entity-body, although some
responses will only include the entity-headers.

In this section, both sender and recipient refer to either the client or
the server, depending on who sends and who receives the entity.

\subsection{Entity Header Fields}
\label{sec:entity-header}

Entity-header fields define optional metainformation about the
entity-body or, if no body is present, about the resource identified
by the request.

\begin{syntaxwcomment}
entity-header
&  =  & Allow               & {\rm ; Section \ref{sec:Allow}}\\
& $|$ & Content-Base        & {\rm ; Section \ref{sec:Content-Base}}\\
& $|$ & Content-Encoding    & {\rm ; Section \ref{sec:Content-Encoding}}\\
& $|$ & Content-Language    & {\rm ; Section \ref{sec:Content-Language}}\\
& $|$ & Content-Length      & {\rm ; Section \ref{sec:Content-Length}}\\
& $|$ & Content-Location    & {\rm ; Section \ref{sec:Content-Location}}\\
& $|$ & Content-Type        & {\rm ; Section \ref{sec:Content-Type}}\\
& $|$ & Expires             & {\rm ; Section \ref{sec:Expires}}\\
& $|$ & Last-Modified       & {\rm ; Section \ref{sec:Last-Modified}}\\
& $|$ & extension-header\\
extension-header & = & message-header\\
\end{syntaxwcomment}

The extension-header mechanism allows additional entity-header fields to
be defined without changing the protocol, but these fields cannot be
assumed to be recognizable by the recipient.  Unrecognized header fields
SHOULD be ignored by the recipient and forwarded by proxies.

\subsection{Entity Body}

See [H7.2]
