Re: Active networking in ns

[Zhenhai Duan <duan@cs.umn.edu>]

On Wed, 13 Oct 1999, Polly Huang wrote:

> On Wed, 13 Oct 1999, Guillermo Rodriguez Garcia wrote:
> 
> > Hello,
> > 
> > I am developing a new protocol to be used in active
> > networks (for an introduction to active networks,
> > see http://www.tns.lcs.mit.edu/activeware). The main
> > issue in active networks is that "active nodes" in
> > the path from the source to the destination might
> > do some (user-specified) additional processing on
> > the protocol packets.
> > 
> > I have written a new agent and I attach it to the
> > nodes I want to be active, but the problem is that
> > I am not sure on how to allow intermediate nodes
> > to process to packet.
> > 
> > For example, let's say I have the following simple
> > topology:
> > 
> > n0(src) ---- n1 ---- n2(dst)
> > 
> > I attach active agents to all the nodes (n0, n1, n2)
> > and then send a packet from n0 to n2. The problem is
> > that the agent at n1 won't see the packet. I guess
> > that I could modify classifier.cc so that my packets
> > are always evaluated at each node, but I would like
> > to know if there is any way to do this without
> > modifying ns itself too much. Any suggestion ?
> 
> Guillermo,
> 
> DOes n1 intercept the packet, process it, and then decide what to
> do next (for example forward it down to n2) or n1 make a quick copy of the
> packet and process it, while the packet continues to be fowarded down
> to n2? If it's the latter, you can probably use a multicast address for

Or if it's the former, and you dont care things like where to put the
agent (before the queue or after the queue), you may try  first get the
handler of the link and do $link add-to-head $youragent.

--
Zhenhai
> your active network agents in n1 and n2 both to join.  That way,
both
> agents are sure to receive the packet.  This is a quick and not very
> pretty hack, but you can get away with digging into the classifer.cc
> details.
> 
> just a thought,
> -Polly
> 
> > 
> > Regards,
> > G.
> > -- 
> > Guillermo Rodriguez Garcia
> > <guille@iies.es>
> > 
>