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Re: GSE IDs [Re: IETF multihoming powder: just add IPv6 and stir]

On donderdag, mei 8, 2003, at 14:13 Europe/Amsterdam, Brian E Carpenter wrote:

As I've said before, the actual requirement is that the lower 64 bits
be mutually unique among the set of correspondents (two for normal cases,
N for p2p cases).
Is it useful to define the requirement this narrow? For a server, I would think it's hard to work with non-globally unique correspondents as potentially every host connected to the network can open a session at any time, creating a collision where there wasn't one previously.

But indeed it is a general point that non-topological
fields are more readily spoofed than topological fields, since
ingress filtering and RPF checks don't apply.
Don't forget return routability. Ingress filtering and RPF checks aren't done everywhere, but return routability protection is relatively good except when the attacker shares a subnet.

The consequence is not automatically that they can't be used, but that
if they are used, an additional layer (such as HIP) is needed.
So we agree that breaking return routability and not repairing the resulting gap with something else isn't an option?

Wouldn't such an additional layer always carry even more state with it? The only advantage is that this kind of state is kept in the endpoints. However, then we end up with the requirement that endpoints must implement the solution, which leads to deployment problems and management difficulties in some networks.

This leaves us with:

1. do it with unmodified hosts in a proxy multihoming agent and eat the state
2. do it in modified hosts and don't involve the routers
3. 1. on on end an 2. on the other

I don't feel the GSE way of doing it in modified hosts and then expect routers to do some additional work provides benefits over one of the above options.

I think that is what you should say.
I'm getting there... It's still more than a month before the draft cutoff for Vienna. :-)

Iljitsch