> From: Curtis Villamizar <curtis@workhorse.fictitious.org>
> When we talk about mobility, based on the discussions we've been
> hearing on this list, we could be trying to solve one of three
> practical problem
I like this taxonomy. A couple of comments/questions:
> 1. Very long time scale mobility. A prefix changes the provider
> that they use.
By "prefix" here, you mean "chunk of topology", right? (Since presumably as
part of moving they wind up with a new prefix.)
> 2. Medium time scale mobility. There are two flavors of this.
> ...
> 3. Short time scale mobility. Again two flavors.
I don't see the difference between these two, at least on the time-scale
axis.
It seems like you have defined two orthagonal axes along which to measure:
one is whether existing connections are required to stay up, and the other is
whether the mobility is over limited topological scope or not. These are both
interesting axes, I agree - but I don't think one can order them against each
other.
The two together define a 4-part space:
- connections-up/limited-scope (which you dealt with as 3a)
- connections-up/non-limited-scope (your 3b, but also 2b)
- connections-down/limited-scope (which you didn't discuss, but it's
not a very interesting case)
- connections-down/non-limited-scope (which you dealt with as 3a)
> b. Active TCP connections must remain up.
This - as with much of mobility - turns out to present basically the same
issues as the equivalent multi-homing case (where you want connections to
stay up).
It's amazing how similar the issues of the two things (mobility and
multi-homing) are - one even has the same sort of breakdown of cases (whether
one wants connections to stay up, over how wide a topological scope is the
multi-homing, etc, etc). This would seem to me to argue for a single
architectural approach...
> Even simpler, use a fixed address on the loopback, use a PPP over
> tunnel connection
This is an interesting approach, one that more and more people seem to be
using for a variety of problems, not just mobility. (One I hear a lot is for
home offices, or road offices, where you have the issue that people want
their remote site to be "within" the corporate firewall, etc.)
Noel
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