Re: Active networking in ns

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

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> Date: Thu, 14 Oct 1999 17:32:20 +0200
> To: ns-users@mash.cs.berkeley.edu
> From: Guillermo Rodriguez Garcia <guille@iies.es>
> Subject: Re: Active networking in ns
> Mime-Version: 1.0
> 
> At 11:38 14/10/99 +0100, you wrote:
> 
> [active networking in ns]
> >
> >I am playing with similar problems, I have found two ways of doing this:
> >
> >1) Modify the classifer/forwarder in the node to check for an active
> >packet mark.  This then gives it to the AN processor for the current
> >node.

Without modifying a classifier it could be possible to have a filter object that 
would do the checking and send the packet to AN processor if necessary. Place 
the filter between the classifier and the node so that every packet received 
could be checked.

Just a thought. I really don't know how active agents work.
 
> 
> Yes, this is the approach followed in the AN package for ns (in
> www.tascnets.com/panama) which has been mentioned earlier
> in this list.
> 
> >2) Write your agent so that rather than sending it to a given
> >destination sends it only to a port on the next hop to the
> >destination...
> 
> Yes, I could do this as well. This way I have to query
> the routing tables to know which node is the next one in
> the path from src to dst... how can I do this ?

get an instance of routelogic and do a lookup:
set rtable [$ns get-routelogic]
set nh [$rtable lookup $src $dst]

> 
> Also, this approach has one disadvantage: it will be difficult
> to simulate an hybrid network with both active and standard-IP
> nodes, because I should send active packets to a port in the
> next _active_ node, not just the next node; that is, if I had:
> 
> n1(src) ---- n2 ---- n3 ---- n4(dst)
> 
> and all the nodes were active except for n3, to send an active
> packet from n1 to n4 I should do n1-n2-n4, skipping n3...
> otherwise n3 would swallow the active packet because there
> would be no active agent there to forward it to the next node.
> 
> I guess that the easiest way to do this actually involves having
> a modified classifier, just like what PANAMA's AN pkg does.
> 
> Regards,
> G.
> 
> 
> --
> Guillermo Rodriguez Garcia
> <guille@iies.es>

Tarik