Subject: [manet] Gateway discovery

From: [email-masked]
Date: Wed, 24 Sep 2003 09:21:44 +0200

Hi Richard/all,

Just to quickly mention that I will be away the next two weeks and won't be able to reply frequently.

About multiple prefixes, I think maintaining multiple addresses (from different gateways) is interesting, but the question remains as how applications can choose among multiple addresses ... I don't think any application code can today make such a choice, so if we want to developp some working code I think maintaining multiple prefixes is maybe a "luxury" that is not really needed. Of course from a research point of you, this is different. ;-)

Regards,
Christophe

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From: "HyunWook Cha" <[email-masked]>
Date: Wed, 24 Sep 2003 18:12:19 +0900

Hi Christophe/all, 

As for implementation of selection among multilple global addresses, how
about updating the Policy table of the default address selections
algorithm ?
I think that distance to gateway may be a good factor for preference
parameter for a global ip.
IMO, its implementation is not difficult and use of multiple global IPs
is not "luxury" since it can support Internet connectivity for MANET.

Regards,
Hyunwook Cha

> -----Original Message-----
> From: [email-masked] [mailto:[email-masked]] On 
> Behalf Of [email-masked]
> Sent: Wednesday, September 24, 2003 4:22 PM
> To: [email-masked]
> Subject: [manet] Gateway discovery
> 
> 
> 
> Hi Richard/all,
> 
> Just to quickly mention that I will be away the next two 
> weeks and won't be able to reply frequently.
> 
> About multiple prefixes, I think maintaining multiple 
> addresses (from different gateways) is interesting, but the 
> question remains as how applications can choose among 
> multiple addresses ... I don't think any application code can 
> today make such a choice, so if we want to developp some 
> working code I think maintaining multiple prefixes is maybe a 
> "luxury" that is not really needed. Of course from a research 
> point of you, this is different. ;-)
> 
> Regards,
> Christophe
>

---

From: Anders Nilsson <[email-masked]>
Date: Wed, 24 Sep 2003 12:34:06 +0200

Hello,

I think it is possible to specify the address using (advanced?) socket 
options, at least in IPv6. Another question is how an application should 
retrieve information about the different available addresses, and 
permissions needed to do so. These are just implementation and design 
issues.

So, I think the answer to your question is yes, it is possible.

regards,

Anders

---

From: Florian Schiel <[email-masked]>
Date: Wed, 24 Sep 2003 13:51:47 +0200 (MET DST)

Hello *,

In my optinion the use of multiple prefixes (from different gateways) for
global addresses is absolutely useful. Even if applications can not chosse
them directly, a predictive process could estimate the 'best'
prefix/gateway for any new connection. This is especially useful for nodes
with high mobility, where a gateway is only reachable for a short
interval. A problem here are the connections made with an 'older' gateway,
that may not be reachable anymore.

I do not see any biger problem with proactive routing protocols, but
reactive protocols may need some sort of procativeness to get information
about other available gateways (at least while an applications stays
connected and exchanges packets).

For most applications (like web-browsing or email) it does not really
matter which (source) address is used. For them, the above estimation
could be used without trouble as long as the (TCP-) connections are only
used for a short time (and thus with a lower chance of breakage).

If I did not get your statement wrong, the question here is the selection
of the source address. Here, RFC 3484 lists some rules for source-address
selection.
In the MANET case, a node would be considered to be just like on of the
multi-homed examples in the RFC3484, since it has at least its address
based of MANET_PREFIX, and one or more addersses with global prefixes.

Another question in this context is: Which source- and destination
addresses belong to the manet and should be routed by manet-nodes, and
which addresses do not belong there and should be dropped?
This could be useful to lower pollution of a manet with non-manet traffic
routed by manet-nodes. Is this considered somewhere?

So long,
	Florian

On Wed, 24 Sep 2003, Anders Nilsson wrote:

> >About multiple prefixes, I think maintaining multiple addresses
> (from different gateways) is interesting, but the question remains as
> how applications can choose among multiple addresses ... I don't think
> any application code can today make such a choice, so if we want to
> developp some working code I think maintaining multiple prefixes is
> maybe a "luxury" that is not really needed. Of course from a research

Florian Schiel    -    Siemens CT IC2 Internet and Mobility Lab
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Siemens AG, CT IC2         phone: +49 89 636-50686
Otto-Hahn Ring 6           mail: [email-masked]
D-81730 Munich