From: ccie2be (ccie2be@nyc.rr.com)
Date: Wed Feb 26 2003 - 21:28:44 GMT-3
Hey Scott,
First of all, let me thank you for your response. It's one of the best
written, logical, responsive, and comprehensive post I've seen on group
study since I've started following group study ( about 2 months ago). And,
to show my graditude, if you're ever in New York City, I hope you'll let me
know so I can buy you a drink.
Now, let me make sure I completely understand what you're saying.
If a mobile node's client software supports a co-located care-of-address, it
doesn't need there to be a Foreign Agent when it attaches to a non- home
network segment because it can be it's own FA. Is that right? And, if so,
does it go thru a process whereby it first checks to see if there's a FA,
and, if so, uses the "typical" method of using the FA's care-of-address,
but, if not, resorts to a co-location care-of-address?
Also, doesn't this process, if I understand it correctly, present a
potential problem in that mobile nodes can attach to any non-home network
segment whether or not attachment is authorized? For example, suppose a
company has 5 network segments A, B, C, D, and E. And, the company's
security policy says that mobile nodes whose home segment is A, B or C can
roam among those 3 segments and mobile nodes whose home segment is D or E
can roam anywhere. To me, it sounds like this policy can't be enforced if
the mobile nodes are able to use a co-located care-of-address. Is that
correct?
And, finally, as a practical matter vis-a-vis the lab, I don't have to be
concerned with this care-of -address distinction because it's not something
I explicitly configure on the router - if anything, it might be an option
configured on the mobile node itself - if it's supported. True?
Anyway, thank you again. I've been wondering about this for several weeks.
Jim
----- Original Message -----
From: "Scott Morris" <swm@emanon.com>
To: "'ccie2be'" <ccie2be@nyc.rr.com>; "'Group Study'"
<ccielab@groupstudy.com>
Sent: Wednesday, February 26, 2003 6:20 PM
Subject: RE: Amazing but true
> The foreign agent care-of-address is the "typical" way that mobile IP
> works. And it's the announcement of the FA itself saying to the home
> agent that 'I know how to get to x.x.x.x' (done through a tunnel). So
> for routing purposes, the FA becomes the care-of-address in order to get
> to x.x.x.x...
>
> The colocate care-of-address actually implies that sometimes a mobile
> node moves onto a roaming network that either has no FA's, or all of the
> FA's are busy. This is when it can become it's "own" FA using a
> colocated care-of-address. The specifics of how to get one aren't in
> the mobile IP RFC's, but DHCP is the primary method. At that point, the
> mobile node technically has two addresses, it's "normal" mobile one, and
> an address within the roaming networks' scope. It is also possible to
> have a pre-determined colocated address configured on the mobile node
>
> So you the network engineer MAY determine things depending on which end
> of the problem you are on! If you are on the mobile node/home agent
> side, there's nothing you can do. If you are engineering the foreign
> agent/roaming network then you are in control of this, and may set up
> extra things in order to facilitate this interaction (or not). It would
> depend on the mobile node software though as to whether it would take
> effect.
>
> If a colocated c/o address is used, the the mobile node will not attempt
> to register with the FA router. It will just start sending IP packets
> as if it were its own FA.
>
> Hope that helps.
>
> Scott
>
> -----Original Message-----
> From: ccie2be [mailto:ccie2be@nyc.rr.com]
> Sent: Wednesday, February 26, 2003 5:33 PM
> To: Group Study; swm@emanon.com
> Subject: Re: Amazing but true
>
>
> Hi,
>
> Here's the original post regarding care-of-addresses used with Mobile
> IP.
>
>
> With Mobile IP there are 2 types of care-of addresses:
>
> 1) Care-of-address acquired from a Foreign Agent
> 2) Colocated care-of-address
>
> The Cisco docs does a good job of explaining what these are but doesn't
> say anything about what determines which type of address is used or why
> 1 type should be used versus the other.
>
> Do I, as the network engineer, determine which type of address is used?
> Does this depend on what mobile node software is installed on the client
> or is this configured on the router, and if so, how?
>
> Please help me understand this. Thanks, Jim
>
> ----- Original Message -----
> From: "Scott Morris" <swm@emanon.com>
> To: "'ccie2be'" <ccie2be@nyc.rr.com>
> Sent: Wednesday, February 26, 2003 5:30 PM
> Subject: RE: Amazing but true
>
>
> > What was/were the original questions?
> >
> > Scott
> >
> > -----Original Message-----
> > From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf
> > Of ccie2be
> > Sent: Wednesday, February 26, 2003 2:50 PM
> > To: Group Study
> > Subject: Amazing but true
> >
> >
> > Hi everyone,
> >
> > Over the past few weeks, several times I've posted a question
> > regarding the two types of care-of-addresses used with Mobile IP. My
> > question concerned what detemines which type of address is used and
> > whether the type used is something that's configured on the router or
> > determined by some other means - perhaps the software installed on the
>
> > mobile client.
> >
> > What surprises me though is that there hasn't been one single
> > response! I don't understand how that could be. I've searched thru
> > both the Group Study archieves and Cisco's documentation and found
> > nothing addressing this question. I also know that mobile IP is fair
> > game for the lab, so I'm amazed that this question continues to go
> > unanswered.
> >
> > And, though I can't understand why that is I've come up with 2
> > theories:
> >
> > a) nobody knows
> > b) nobody cares
> >
> > I can't imagine that nobody on groupstudy knows this - this is
> > probably the most knowledgable group of networking professional in the
>
> > world - so let's nix that idea.
> >
> > Could it be that nobody cares? That's also hard to imagine.
> > Everyday, questions seemingly far more esoteric are posted and
> > responded to. Besides, there must be at least a few people who might
> > need to implement Mobile IP in the near future and they would
> > certainly need to know about this. And, even if nobody at the moment
> > needed to know about this for work, most people on group study seemed
> > to be very intellectually curious So, let's nix this theory as well.
> >
> > Well, I hope this sparks some discussion, and maybe, in the process,
> > generates the answer to the original question.
> >
> > What do you think?
> >
> > Jim
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