Subject: [manet] OLSR and IP Addresses

From: [email-masked]
Date: Thu, 11 Mar 2004 17:33:34 -0700

I have a question about how to assign IP addresses when using OLSR.

Section 11.1 of RFC 3626 says:
The nodes in the MANET network SHOULD be assigned addresses within a defined
address sequence, i.e., the nodes in the MANET SHOULD be addressable through
a network address and a netmask. 

Since the OLSR routing protocol messages contain only IP addresses and not
subnet masks, it seems like this is implying that all IP addresses in the
OLSR
MANET should be on the same IP subnet.  Is this the case?

If so, this seems like a limitation in OLSR that is not present in other
protocols
such as AODV.  The AODV RFC says it was designed for use by mobile nodes
with IP addresses that are not necessarily related to each other.

Can someone please provide some clarification on these points?

Thanks,

Richard Herron
L-3 Communications

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From: Thomas Heide Clausen <[email-masked]>
Date: Fri, 12 Mar 2004 09:46:28 +0100

Richard,

Thanks for your interrest in OLSR.

On Thu, 11 Mar 2004 17:33:34 -0700
[email-masked] wrote:

> The nodes in the MANET network SHOULD be assigned addresses within a
> defined address sequence, i.e., the nodes in the MANET SHOULD be
> addressable through a network address and a netmask. 
> 
> Since the OLSR routing protocol messages contain only IP addresses and
> not subnet masks, it seems like this is implying that all IP addresses in
> the OLSR

Nope. Each node must have an IP-address, however there are no requirements
as to how these addresses are assigned within the OLSR network. You may
have nodes from different "IP subnet" in the same OLSR manet -- it makes no
difference as to how the routing protocol routes. For all OLSR is
concirned, an IP address is an IP address -- always.

The condition from section 11.1 (which is a SHOULD, btw., not a MUST) comes
from the simple fact that if you want to advertice routes from the OLSR
manet into another routing domain, then it is smart to be able to address
the entire manet as a "chunk" -- to aggregate the node addresses by means
of a subnet. However this is a real issue only at the time when you want to
inject routes to manet nodes into an external network. This is similar to
the way aggregation is done by other prevailing internet routing protocols.

> with IP addresses that are not necessarily related to each other.

AODV and OLSR works identically wrt. requirements address assignment within
the manet. There is no difference on this point.

I hope this answers your question?

Regards,

--thomas