At 12:44 04/04/2003, R. Simkins wrote:
I talk about mobile IP (RFC2002) at the start of my WLAN security paper. Home Agents, Foreign Agents and Care-of-Addresses.
When I come to introducing 802.11 I am struggling to put into words how it adopts RFC2002. I am not sure what happens in 802.11 when a client of network A moves out of the network into a new one, can this happen? For a client to be allowed service it must successfully provide authentication. If it is a FA then the authentication wouldnt be successful. How is tunneling the CoA supported by 802.11, if it is at all?
Well, first thing, WLANs operate at layer 2, while Mobile IP operates (mostly) at layer 3 (I say mostly because there are some cases where there are direct interactions with layer 2 to avoid assigning IP addresses and the like).
So there are two cases:
- user roams from one AP to another within the same L2 network: this is pure 802.11 roaming, and Mobile IP shouldn't see anything.
- user roams from one AP to another within different L2 networks: this is pure Mobile IP roaming.
In any case, 802.11 authentication should happen first (depending on the exact setup: pure 802.11 authentication, 802.1X authentication, 802.11i pre-authentication...). In the second case, there might be Mobile IP authentication on top.
I don't think there are any current "optimizations" to have one single authentication process for both, but I might be wrong. Check out the Internet-Drafts repository to see if there's anything there.
Now, your question may be about pure 802.11 inter-network roaming (how a user of T-Mobile roams on to the network of Swisscom, say), but that's a totally different subject (at the moment there's no MobileIP use at all in such situations -- not that there is much anyway, I still have to see a FA in real life).
Hope that helps,
Jacques.
-- Jacques Caron, IP Sector Technologies Join the discussion on public WLAN open global roaming: http://lists.ipsector.com/listinfo/openroaming
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