Subject: [manet] Gateway: Tunneled vs. direct approach?

From: "Marcin Michalak" <[email-masked]>
Date: Thu, 22 Apr 2004 16:06:52 +0200

Hello,
 Some time ago there was a discussion about tunneled vs. 'direct' 
approach to access outside world from ad-hoc network.
 I'm writing a summary and need following information:
- which technologies use which approach?
- has a general consensus been reached which approach shall be used?
 Thanks for help in advance.
 Regards,
  Marcin Michalak
----------------------------------------------------------
Marcin Michalak		Research Engineer
Mobile: +41 79 330 83 51	Telscom AG		

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From: "Tyan-Shu Jou" <[email-masked]>
Date: Thu, 22 Apr 2004 09:57:11 -0700

Hi,
  I do not think any consensus exists on this topic. But you may also
want to monitor the evolving progress on CAPWAP WG (and the lwapp
ineternet draft, which triggered the formation of the WG), that touches
related issues.

--Tyan-Shu Jou
  Janusys Networks

-----Original Message-----
From: [email-masked] [mailto:[email-masked]] On Behalf Of
Marcin Michalak
Sent: Thursday, April 22, 2004 7:07 AM
To: [email-masked]
Subject: [manet] Gateway: Tunneled vs. direct approach?

Hello,

---

From: David Young <[email-masked]>
Date: Thu, 22 Apr 2004 15:24:47 -0500

On Thu, Apr 22, 2004 at 04:06:52PM +0200, Marcin Michalak wrote: > Hello,
> - has a general consensus been reached which approach shall be used?

I think that it will depend on the network.  I am concerned with
community wireless networks.  I expect for a community wireless network
to be multihomed.  I do not expect for it to run an EGP at the borders.
Ordinarily, there will be NAT or 6to4 at the borders.  Thus, if I let the
gateways inject default routes into the IGP, then a node with (near-)equal
path metric to two gateways may flip-flop between them, severing TCP
connections each time.  That must not happen, so I will require wireless
routers to select a gateway, with substantial hysteresis, by more rigorous
criteria than path metric alone.  Routers will tunnel to the gateways.

At <http://che.ojctech.com/~dyoung/gateway/>, I've put up the beginnings
of some documentation for a protocol that routers will use to advertise,
discover, and negotiate for a gateway's services on our community
wireless network in Urbana, Illinois (cuwireless.net).  I invite your
comments and criticisms on those documents.  Sorry that they are not
more self-contained.

The way it works is essentially this: the IGP (OSPF, today; HSLS, in
the future) is enlisted to disseminate gateway advertisements using,
for example, OSPF Opaque LSAs.  A router requests "gateway services"
from gateways that meet its selection criteria.  Gateway services can
include NAT to a shared IPv4 number, NAT to an independent IP number,
or a 6to4 subnet.  Gateways answer, according to their resources and
policy, with an offer or a refusal of gateway services.  Finally, if a
router gets an offer, it sets up a tunnel to the gateway.

Dave

-- 
David Young             OJC Technologies
[email-masked]      Urbana, IL * (217) 278-3933