Subject: RE: identity persistence and comparison issues

From: "Christian Huitema" <[email-masked]>
Date: Tue, 29 Jun 2004 09:14:14 -0700

> The point is that today, the underlying assumption of most
applications
> is that the IP address they get back from an A or AAAA query, or any
> other source including manual config, is a permanent identifier with
> the nice property that the routing system can use it as a locator.

Is that actually true?

Looking at my own neighborhood, I see the following:

1) The most popular applications, web browsing and e-mail, do not make
the assumption that addresses are identifiers. Web servers commonly use
techniques such as DNS load balancers, and the clients see a different
address every time. Mail clients typically resolve a domain name before
any attempt to communicate with a server.

2) The vast majority of networking applications are not written to the
socket API. They are typically written in Visual Basic, C# or other high
level languages, and they interface the network through high level calls
such as RPC, DCOM or WinInet (an API to the HTTP protocol). The
underlying libraries do not assume that the addresses are fixed; the API
typically uses a service name or a server name, not an IP address.

3) Emerging applications written around instant messaging services, peer
to peer services or SIP do not assume that a host address is fixed.
Indeed, the SIP payloads carry the "current IP address" at which a SIP
UA expects to receive packets. 

Indeed, most of these applications have a concept of "session", and
expect that the addresses will remain stable for the duration of the
session. But many also have a capability to reconnect if the session is
interrupted, and the reconnection procedures typically include a name
resolution.

-- Christian Huitema