Subject: Re: [Seamoby] Re: Regarding CAR Discovery - Sleeping WLAN interface case

From: "Govind Krishnamurthi" <[email-masked]>
Date: Mon, 25 Mar 2002 17:11:58 -0500

James,

>I can't see how the AR can know how many interfaces the MN has. On any
>particular day, there may be two or only one, or maybe even none if the
>user forgot all her interface cards.
[Govind] Well this information can be kept as part of the MN's profile. But 
I am sure there are other ways to do it. As I explained in the previous 
mail, I don't see why the MN's forgetting to power on a interface card or 
forget inserting is such a big deal. Again, I am not
advocating that this is the way to do it. All I am saying is that
we shouldn't say that this isn't possible at this stage when we are just
considering requirements.

>
>The AR won't do the waking, the MN will. That is, if the MN is getting
>traffic on one interface, it will get the CAR information on that
>interface, then the MN will make the decision about whether to power up
>the other interface.
>How can the AR wake the MN on an interface that doesn't have any power,
>much less IP service?

[Govind] Ofcourse, the MN will do the waking, but the AR can help it wake up 
selectively as opposed to the MN periodically waking up as you seem to 
suggest  as the only way to go.

>
>More specifically, the software on the MN will probably ask the user
>about whether they want to switch it on, or perhaps some kind of user
>agent.

[Govind] Maybe, but that is quite out of scope for the current discussion. 
The point is whether the network can help or not. I believe
that it can.

>
> > [Govind] What if it wants to move from one WLAN network to another...
> > essentially to save cost for eg?, and it has just one interface.
> > Clearly, CAR discovery is needed for FMIPv6 and context transfer and
> > they do talk about WLAN -> WLAN handovers.
> > [snip]
>
>To my knowledge, it is not possible to deploy two different 802.11b
>networks in the same area. It would be possible to deploy an 802.11a and
>802.11b network because they operate in different frequency ranges, but
>I view that as essentially two different media. Not sure about 802.11g.

[Govind]Frankly, I don't know about this i.e., if it is a part of the spec..

But theoretically at least it should be possible to operate in the same 
frequency. Even if the spreading codes are the same. Yes, this will cause 
packet collisions but CSMA/CA can handle it is it not? All we have
to make sure is we backoff properly and make sure that the MN receives 
beacons. My previous discussions however were under the assumptions
that multiple APs of WLANs are found.

>
> > [Govind] I don't see any great loss of simplicity in the latter. I do
>see
> > the bandwidth/power/time efficiency in the latter though.
> >
> >
>
>Well, the other alternative is that the AR could simply pass the CAR
>information along when the MN arrives. No need for the AR to know
>anything more than that the MN arrives, i.e. keep it reeeaaal simple.

[Govind] I agree that we should keep the actual solution simple.
But in the process we shouldn't compromise on getting to the best solution.

Regards,
Govind.

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From: "James Kempf" <[email-masked]>
Date: Tue, 26 Mar 2002 09:31:14 -0800

Govind,

The requirements are supposed to constrain the solution in a particular
direction. Constraining CAR discovery to avoid complex protocols for
communication of the MN's interface card state to the network is an
example.

Can you articulate why such a solution is so much better than having the
MN decide based on the CAR discovery information that we should continue
to consider it?

            jak

----- Original Message -----
From: "Govind Krishnamurthi" <[email-masked]>
To: <[email-masked]>
Sent: Monday, March 25, 2002 2:11 PM
Subject: Re: [Seamoby] Re: Regarding CAR Discovery - Sleeping WLAN
interface case

---

From: "James Kempf" <[email-masked]>
Date: Tue, 26 Mar 2002 09:31:14 -0800

Govind,

            jak

----- Original Message -----
From: "Govind Krishnamurthi" <[email-masked]>
To: <[email-masked]>
Sent: Monday, March 25, 2002 2:11 PM
Subject: Re: [Seamoby] Re: Regarding CAR Discovery - Sleeping WLAN
interface case