[Cu-wireless] roaming initiative & DHCP question

stephane_alnet at ureach.com stephane_alnet at ureach.com
Thu Jun 27 00:12:33 CDT 2002

Hi Dave,

> I have not figured this out yet. It seems like they're trying to invent
> a new business model. I cannot tell if there is any technical content
> to this initiative at all.  It looks like they're trying to answer the
> question, "If you're signed up with WISP X, and you roam from WISP X
> to WISP Y, how are the costs shared by X and Y?" It is sort of like a
> "peering agreement" for WLANs.

That's a pretty good description; but it's not a new business model..
(More here: http://company.monster.lu/excilanlu/ )


Looks like another instance of "first to market". GSM roaming is a
lucrative market (the same way settlement is a lucrative market in the
long-distance & international telecom industry), both for the telecom
companies and for the companies that provide the service (Excilan
apparently pretending to be one of these in the GSM market). Adding 802.11
to your portfolio (because, obviously, it's wireless and works the same
way as GSM, so on top of that "you already have the expertise") seems like
an easy way to expand zillionfold your customer base in the flip of a
(marketing) switch. Where have I already read that story, again?


Now, regarding your DHCP question: DHCP (or BOOTP) requests are sent to
broadcast addresses (since the client doesn't even know it's own IP
address, there's no reason to believe it's going to know the IP address of
the server it's requesting its IP address from). If the server and/or the
relay want to be able to pick these broadcasts off the wire, there's no
secret: they'll have to bind() to IPADDR_ANY.

> The reason that I want to do that is to
>  a) serve DHCP clients on interfaces belonging to a pod or uplink
>     "master" (i.e., the first station in a pod, or the first station
>     in an uplink network)
>  b) simultaneously relay DHCP requests to the first station in
>     a pod, who runs the DHCP server for the pod

I'm not sure I understand that part; do you say you want to have them both
running on the same interface (layer 2) or on the same machine? If you
want to pick interfaces, dhcrelay has a "-i" command-line parameter
(ignore these interfaces) while dhcpd will accept interfaces as its last
parameters (use these interfaces). If you want both on the same L2
interface (or SSID), I think it's going to get messy very rapidly; I think
you could have dhcrelay relay to the local dhcpd (via a loopbak interface
of some sort), but I don't see the advantage. (If you want to change
behaviors dynamically, then you probably could do that by changing
dhcrelay's config file on the fly and restarting it, I'd guess?)

At best I'm confused. :)  Would you happen to have a drawing showing what
you want to do?


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