Hardware Broadcast II
Wed, 14 Oct 1998 13:58:01 -0700 (PDT)
On 14 Oct 1998, Yuri Pryadkin wrote:
> Pascal Anelli <Pascal.Anelli@lip6.fr> writes:
> > I have nearly the same question.
> > My question is how an agent like arp can use Mac broadcasting?
> > I know Classifier/mac implements a broadcasting mechanism in copying
> > packet.
> > AttachLL (in addnode) is called with sender node and receiver node as
> > parameters, i.e. LL component use unicast address
> > only. . Morever the link_ member used for routing
> > haven't any information concerning a broadcasting address. I don't
> > understand how a packet to broadcast is sent from an agent to Mac
> > component and If I change $ll set macDA (in attachLL) to a BCAST_ADDR, I
> > am not sure if all the arp agent will receive a arp request (broadcasted
> > packet)
> > Thank you for some light on this point
> Well, we've made some changes in the current snapshot and e.g. you can
> set a variable in Classifier/Mac to broadcast packets no matter what
> the address is. Anyhow, if you want to implement ARP, you should
> definitely take a look at the snapshot, looking for LAN C++ code
> changes and tcl/lan/vlan.tcl
> You're right: If you set macDA to BCAST_ADDR, the packet will make it
> to every node on the LAN, but it will not be received by every agent,
> because node's classifier will not classify it as you want. That's
> why I don't think implementing ARP as an agent is a very good idea:
> agent is more like an IP entity with the address, port, etc. It seems
> that a better place for ARP would be on top of MAC layer or even
> inside MAC.
and in fact there is an implementation of arp (in link layer) as a part of
CMU's mobility module available from
http://www-mash.CS.Berkeley.EDU/ns/ns-contributed.html or directly from
CMU's page at
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