Re: [Manet-dt] Link local Multicast Address - MANET Routers

["Ian Chakeres" <[e-mail]>]

Comments inline.

On 4/18/06, Brian Haberman <[e-mail]> wrote:
> In what context would this common address be used?

The common address will be used for link local MANET routing protocol packets.

In NHD the address will be used for HELLO messages - all messages
In OLSRv2 it will be used for TC messages - all messages
In DYMO it will be used for RREQ, RREP, & RERR messages - all messages

> Do we expect MANETs to exist that run multiple routing protocols?

Given the common packet format, and soon to be common neighborhood
discovery, I think multiple MANET routing protocol components may be
run together in the future.

> If so, the filtering now has to be done above the MAC filters (i.e. on
> port or protocol numbers) which will affect power consumption.

Yes, but using a different multicast address for each protocol will
require that each protocol's messages be carried in separate packets.
The consequence of carrying each protocols messages in their own IP
packets can increase wireless media access significantly.

> What about security issues of sending packets that are not meant
> for a subset of routers, but are received by them due to the shared
> address?

I do not see this as an issue to be addressed by the base MANET protocols.

We are discussing authentication of routing packets for the base spec.

> In short, I would like to see a description of how this address will be
> used before I make any judgment.

Does the discussion above help?

Ian

Note - this address would be very similar to OSPF (RFC 2328) AllSPFRouters

o   Use of IP multicast.  Some OSPF messages are multicast, when
        sent over broadcast networks.  Two distinct IP multicast
        addresses are used.  Packets sent to these multicast addresses
        should never be forwarded; they are meant to travel a single hop
        only.  To ensure that these packets will not travel multiple
        hops, their IP TTL must be set to 1.

        AllSPFRouters
            This multicast address has been assigned the value
            224.0.0.5.  All routers running OSPF should be prepared to
            receive packets sent to this address.  Hello packets are
            always sent to this destination.  Also, certain OSPF
            protocol packets are sent to this address during the
            flooding procedure.

  AllDRouters
            This multicast address has been assigned the value
            224.0.0.6.  Both the Designated Router and Backup Designated
            Router must be prepared to receive packets destined to this
            address.  Certain OSPF protocol packets are sent to this
            address during the flooding procedure.

> Regards,
> Brian
>
> On Apr 15, 2006, at 18:05, Ian Chakeres wrote:
>
> > Now that we have a common packet building block, and will soon have a
> > common neighborhood discovery building block, I think it is pretty
> > natural to use a common multicast address for reaching link-local
> > MANET routers. Please reply if you support this common multicast
> > address being allocated.
> >
> > If I receive support I will start moving on this.
> >
> > Ian Chakeres
> >
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