Re: [ns] node address and MAC address

[Tarik Alj <aljtarik@cholla.inrs-telecom.uquebec.ca>]

>Date: Thu, 27 Jul 2000 08:09:20 -0700 (PDT)
>From: Yan Yu <yanyu@catarina.usc.edu>
>To: Tarik Alj <aljtarik@cholla.inrs-telecom.uquebec.ca>
>cc: yanyu@catarina.usc.edu, ns-users@isi.ed
>Subject: Re: [ns] node address and MAC address
>MIME-Version: 1.0
>
>my simulation includes a duplex link connected to a wired LAN, so the
>topology is soemthing like:
>2 = 1 >-< 0
>the link between node 2 and node 1 is a duplex link, the link between 1
>and 0 is a wired LAN. 
>my IP packet is from 2 --> 0, I want to implement reliable link layer
>between 1 and 0. 
>so the node 0 receives a packet from 2, it will sends a packet back to its
>previous hop, i.e., node 1, not the source of the packet, "2".. 
>
>could you pls give me any hint on how to get the node address of node
>"1"?

well from the mac header you should be able to get the source address (I 
assume), wich should be that of node 1; then you would need to do do some sort 
of rarp lookup to get the node id.

>Thanks!!!
>yan
>
>
>On Thu, 27 Jul 2000, Tarik Alj wrote:
>
>> What do you mean by "previous hop"? On an Ethernet segment there can't be 
more 
>> that one "hop" : from source address to destination address. So you probably 
>> want the source address.
>> 
>> Exception with the LanNode : the LAN itself is a virtual-Node so packets look 
>> like they are travelling from src to LAN to dst. 
>> 
>> >Date: Wed, 26 Jul 2000 14:29:13 -0700 (PDT)
>> >From: Yan Yu <yanyu@catarina.usc.edu>
>> >To: ns-users <ns-users@isi.edu>
>> >Subject: [ns] node address and MAC address
>> >MIME-Version: 1.0
>> >
>> >
>> >My problem is to implement a reliable link layer. IN order to send a  
>> >hop-by-hop link layer ack back to the previous hop, I reverse the MacSA
>> >and MacDA in the packet, and send it back. But this is not enough for
>> >link layer. By reversing the macSA and macDA, the packet can reach the mac
>> >layer of the previous node, it can NOT reach the  link layer of the
>> >previous
>> >node. I guess there is some kind of filter which will filter out any
>> >packets whose dst address is diffrent from myself. So I change the dst
>> >address in packet to the MAC address of the previous node (i do not know 
>> >how to get the node address of previous hop node), It works when the node
>> >address and MAC address of the nodes are the same. However, The packet
>> >won't be able to get to the link layer if the Mac address happen to be
>> >different from the node address..
>> >In order to get around this,
>> > my question is:
>> >1. How to get to know the node address of the previous hop node?
>> >( I use wired LAN..)
>> >or how to get the node address from its MAC address?
>> >
>> >2. if I can not get the above information, can I change the node address
>> >arbitrarily, so that the node address can be the same as the MAC address?
>> >If I write up such a function myself to change node address, will the
>> >change mess up the normal operation in ns, such as routing?
>> >
>> >THanks a LOT for any feedback in advance!
>> >yan 
>> >
>> >
>> >
>> 
>> Tarik 
>> 

Tarik