HTTP/1.0 uses many of the constructs defined for Internet Mail (RFC 822 ) and the Multipurpose Internet Mail Extensions (MIME ) to allow entities to be transmitted in an open variety of representations and with extensible mechanisms. However, RFC 1521 discusses mail, and HTTP has a few features that are different than those described in RFC 1521. These differences were carefully chosen to optimize performance over binary connections, to allow greater freedom in the use of new media types, to make date comparisons easier, and to acknowledge the practice of some early HTTP servers and clients.
At the time of this writing, it is expected that RFC 1521 will be revised. The revisions may include some of the practices found in HTTP/1.0 but not in RFC 1521.
This appendix describes specific areas where HTTP differs from RFC 1521. Proxies and gateways to strict MIME environments should be aware of these differences and provide the appropriate conversions where necessary. Proxies and gateways from MIME environments to HTTP also need to be aware of the differences because some conversions may be required.