Subject: [manet] 802.11

From: DANIEL BYRNE <[email-masked]>
Date: Wed, 10 Mar 2004 12:28:44 -0600

Since the 802.11 mac header has address fields for sender, transmitter,
receiver and destination, why aren't ad-hoc routing protocols based upon
this seemingly built-in faciity for multihop routing?  Each receving node
would simply have to change the rx address to the next hop.

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From: Dave Maltz <[email-masked]>
Date: Wed, 10 Mar 2004 15:57:38 -0500 (EST)

> would simply have to change the rx address to the next hop.

DSR was originally conceived of as a layer-2 routing protocol that could
be implemented directly in the interface card using MAC addresses as you
suggest.  In that role, the protocol could be used to "transparently"
extend the coverage of access points and provide multiple-hop ad hoc
connectivity between nodes running any layer 3 protocol.

We made the decision to define what's become DSR as a layer-3 protocol so
that an ad hoc cloud could extend across multiple types of interfaces and
even across the Internet itself.  Consider a node with two types of
interfaces (say IR and 802.11b).  If the multi-hop ad hoc routing is done
at layer 3, this node has the potential ability to discover routes and
forward packets between a node that only as IR and node that only has
802.11.

Building a gateway to efficiently connect an ad hoc cloud to the Internet
requires the network layer on the gateway to have knowledge of how routing
works in the ad hoc cloud, so fewer layer violations are involved if the
ad hoc routing protocol runs at layer 3.

Cheers,
 -dam