Re: keepalives and proxies: a request and a proposal

On Sat, 18 Nov 1995, Roy T. Fielding wrote:

> Tunnel is defined in the lastest HTTP/1.0 specification (it is one of
> the many definitions I added to explain some of the characteristics
> of HTTP communication that is often ignored by implementors).
> Use of a tunnel is compliant with HTTP, but requires that the HTTP
> semantics not be changed by the presence of a tunnel.

I'll look at the definition of tunnels before commenting more on this.

> Suffice it to say that IP addresses exist at (or below) the transport
> level, and HTTP exists at the application level.  Using IP numbers
> (or even hostnames) to define application-level behavior is wrong
> because it won't work when the transport layer changes.  Therefore,

In the original message, and in further postings, Lorenzo and I
talked about "unique identifiers" of the node (client, proxy or
server), not IP addresses. I agree that addresses exist at the
transport level, but there must exist some other form of unique
identifier that is understood at the application level. Just use
that.

> I try to avoid including them in the protocol when possible.

I fully agree on this point; this is something that probably hasn't
received much attention in the past.  Note, though, that at times the
distinction between application and transport is very difficult. As an
example, URLs can include IP addresses, such as

    http://131.114.9.237/~luigi/

and all browsers will happily find the requested info.

	Luigi
====================================================================
Luigi Rizzo                     Dip. di Ingegneria dell'Informazione
email: luigi@iet.unipi.it       Universita' di Pisa
tel: +39-50-568533              via Diotisalvi 2, 56126 PISA (Italy)
fax: +39-50-568522              http://www.iet.unipi.it/~luigi/
====================================================================

Received on Sunday, 19 November 1995 06:42:48 UTC