[opendtv] Re: IP vs. MAC addresses (was: Twang's Tuesday Tribune)
- From: "Manfredi, Albert E" <albert.e.manfredi@xxxxxxxxxx>
- To: <opendtv@xxxxxxxxxxxxx>
- Date: Mon, 10 May 2004 17:02:51 -0400
Craig Birkmaier wrote:
> Perhaps the best way to assign IP addresses then, would be to map
> them to physical locations. A device would then be addressed based on
> its nominal "at rest" location, which should be relatively unique
> (you might have a range of addresses for a "stacked" location like an
> office building). And when roaming the device could be assigned
> temporary location based IP addresses as it moves between WiFi points
> of presence.
That's normally how it's done. IP addresses are mostly tied to a
location, so routers know where to direct the packets. And again
often, but certainly not always, they are temporarily assigned. This
was more important in IPv4, where addresses are scarce, but I'm
sure the practice will continue.
But I was left unsatisfied with the previous exchange on this IP
vs MAC address because it limited the role of IP addresses to less
than it really is.
A roaming host may either change its IP address as it roams, *or*
it may retain its permanent IP address and acquire a temporary one
while it is in the temporary location, *or* the entire subnet might
be roaming along with that host, so that the hosts' IP addresses
can remain unchanged, *or* it can become merely a unique identifier,
used in wireless ad-hoc nets. Each of these techniques is used, and
each one has multiple flavors.
The consistent difference between IP and MAC addresses is that the
IP address hierarchical, useful for routing packets through a
global infrastructure, whereas the MAC address is an arbitrary
number which identifies a physical interface (usually, although
sometimes MAC addresses identify the whole node).
Bert
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