[Cu-wireless] Re: Cu-wireless digest, Vol 1 #138 - 3 msgs

Jon Dugan jdugan at ncsa.uiuc.edu
Tue May 28 18:42:53 CDT 2002

On Tue, May 28, 2002 at 12:33:27PM -0500, The Morenz Family wrote:
> Hi David, et. al.
> >Must an NBMA network have a D.R.? If we set every router's priority for
> >election as D.R. to 0, do we get broken routing or working routing w/o
> >any D.R.'s ?
> In a multiple access scenario  ("the MA in NBMA"), Designated Router 
> elections are necessary since DR's are the only routers to forward 
> link-state updates. Like any election, it can be rigged. But when you 
> set them *all* to "0" I believe you are essentially preventing DR 
> election and breaking the routing. I'd have to defer to Jon or 
> Stephan on this.

  I'm not sure of the details of defeating DR election, but I don't think
  that is the direction we want to head.

  PMP is clearly designed to for a situation similiar to ours.  NBMA is
  intended for a full mesh, PMP can handle a partial mesh.  

  For small routing tables like ours O(64) routes (32 routes to nodes and 32
  routes to the subnet connected to each node) I'm not sure that we will have
  any computational problems.

> >It is more clear all the time that OSPF is not the routing protocol we
> >want to use. I think that the protocol we do want to use, we will have
> >to program ourselves to operate in Zebra. It is probably DSDV, AODV,
> >or one of the other new-fangled routing protocols for ad hoc networks.

  Wow, I hadn't seen this stuff before.  Here's a pointer to the Mobile Ad Hoc
  Networks (MANET) working group in the IETF:


  I think we need to take a close look at what these folks have been working

  It also appears that there are implementations of AODV at least.

> Does anyone know the answer to my earlier question...can you have 
> more than one subnet/logical network on the same channel in the same 
> airspace? That would be a prerequisite, it seems to me, to do the PMP 
> design that we're thinking of.

  I'm not sure I follow.  Why do we need more than one logical subnet in the
  same airspace/pod?  From looking at the description of PMP in John Moy's
  book on OSPF PMP directly addresses the case of not having full reachability
  within the logical subnet.

Jon Dugan             |  Senior Network Engineer, NCSA Network Development
jdugan at ncsa.uiuc.edu  |  269 CAB, 605 E Springfield, Champaign, IL 61820
217-244-7715          |  http://www.ncsa.uiuc.edu/~jdugan/

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