Subject: RE: Manet Flooding

From: Scott Corson <[email-masked]>
Date: Sun, 13 Jan 2002 14:38:44 -0500

Folks,

I was indeed talking about "what to do" and not "how to do it".

I'm basically fine with the following general definition of a manet flooding
"service".

> "the process of delivering data or control messages to every 
> node within the network under consideration".

The service may ride upon/be imbedded within existing manet unicast routing
protocols, or can be a separate entity.

The *persistence* of a protocol in achieving the service's aim is up to the
protocol designers IMO, trading off probability of delivery vs. work
expended.

Whilst I'm fully aware of the literature Richard repeatedly cites, we are
working on IETF standards and the terms "network" and "broadcast" are a bit
overloaded already, so I suggest the term "flooding" to describe this
service in the IETF context.

So, if consensus exists with the aforementioned definition, can we now
switch to a more detailed discussion of the service?  Do we use multicast or
broadcast addresses for example?  I'm looking for a manet flooding service
definition of sorts, rather like what RFC1112 provides for IP multicast.

-Scott

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From: [email-masked]
Date: Sun, 13 Jan 2002 15:08:15 -0800

> service in the IETF context.

I agree with this term and will use it from now on.
I will call the brute-force mechanism "classical flooding", 
since that seems to be the consensus.

> definition of sorts, rather like what RFC1112 provides for IP multicast.

Regarding addresses, the two multicast addresses "ALL_IPv4_MANET_NODES" 
and "ALL_IPv6_MANET_NODES" that Charlie proposed in 
draft-ietf-manet-bcast-00.txt make sense to me.  (I think Fred Templin 
also suggested such a multicast address several months ago.)

It seems to me that the flooding service should also be
used to provide general multicasting, in case a MANET multicast
protocol is not available.  Thus, a packet that has *any* multicast 
address that is associated with the MANET can also be flooded.
This requires all MANET nodes to know the multicast address
of every group associated with the network, but not the membership
of each group (which I think is reasonable). Does this make sense?

I agree with Scott that protocol characteristics such as
reliability, etc., should be the designers discretion.

> protocols, or can be a separate entity.

It seems to me that each of the four main routing protocols
already have a mechanism for flooding that is easily 
extended to handle general data packets. (We have not yet
stated this for TBRPF, but it is not hard to do.)
If AODV, DSR, OLSR, and TBRPF each has its own efficient flooding 
mechanism, I do not see the need for a separate flooding protocol
other than classical flooding, since anything other than
classical flooding will probably require additional overhead.
(So it seems to me that the focus will probably be on flooding
mechanisms that are routing-protocol dependent.)

Regards,
Richard

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From: [email-masked]
Date: Sun, 13 Jan 2002 19:14:41 -0800

Correction...

> address that is associated with the MANET can also be flooded.

I did not really mean *any* multicast address; 
I meant any multicast address that is forwardable
(which excludes the limited broadcast address 255.255.255.255
and the low-numbered multicast addresses 224.x.x.x).  

(Fred Templin and I previously suggested a method using 
encapsulation to allow the non-forwardable addresses to be 
multicast or flooded to all MANET nodes, but that is
outside the scope of what I am discussing.)

I suppose flooding can also be used for prefix-directed broadcast.
Assuming that each MANET node knows all the prefixes associated 
with the MANET, any packet having the prefix-directed broadcast
address for any prefix associated with the MANET can be flooded.
Comments?

Richard

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From: "Philippe Jacquet" <[email-masked]>
Date: Mon, 14 Jan 2002 16:09:25 +0100

Flooding for

> > node within the network under consideration".

Classical Flooding for

> "Request for a remote node to propagate the information along with
flooding
> request (I am avoiding other terms to keep conflict of layers at a
minimum)
> contained in the flooding request to as many nodes as it can (best efforts
> service), while taking care to avoid replication using local information."

are OK for me. The former is for the objective and the latter is a mechanism
intended to achieve this objective.

Philippe