Re: active networking in ns

[Lidia Yamamoto <yamamoto@run.montefiore.ulg.ac.be>]

Guillermo,

Could you please send me, or post to the list in case you judge more people might
be interested, the initial messages that lead to this thread? (the first message
I got is yours, which is already a reply to a reply).

Are you talking about PANAMA's AN package for ns (Diane Kiwior)? I also studied
this implementation, but it looks quite specific to reliable multicast, and I
found it difficult to apply to a more generic context.

Therefore I started working on a generic implementation of Active Networking in
ns, which is intended to be as simple&stupid as possible, while fitting the goals
of enabling generic active network packets to be transmitted and executed, using
the IP-like packet forwarding model of ns. My simulation does not require
modifying the classifier for the moment, although I guess that for optimisation
purposes I'll probably end up by doing it.

What I do is to define "execution environment" agents (implemented as a subclass
of Agent/Message) that send "capsules" among themselves. These "capsules" are
simply Agent/Message packets in which the "message" is the code to be executed.
For the moment the code I send is only the name of a tcl procedure followed by
parameters (therefore code loading/caching is not simulated). Using this it is
surprisingly simple to implement typical AN examples such as ping, multicast,
etc.

For the moment I solve the routing problem by having the execution environments
"cheat": they look at the global ns static routing tables to find the next "EE
hop" on the path towards a destination EE. A more elegant solution would be to
deploy an active routing protocol using IP as the link layer, but since I don't
need sophisticated routing at the moment, I can live with the "cheating"
solution. The drawback of this solution is that I cannot benefit from IP
multicast, so the multicast trees are not optimal, the same as when using MBONE
tunnels.

If you and/or other people are interested I am glad to make my implementation
available, but in this case I need some time to prepare a neat version for
distribution...

Lidia.


Guillermo Rodriguez Garcia wrote:

> >> I have been studying this for a while in the past days, and there
> >> are only two things about it:
> >>
> >> - Although they intended to release this package as a 'generic'
> >> extension to ns, in fact it is very focused towards AER, their
> >> own active protocol; or at least towards active protocols for
> >> multicasting.
> >
> >The basic Active Network Package is designed to allow multicasting
> >in active networks so there is some additional overhead in that respect.
>
> Yes; I guess waht I will have to do at the end is just use
> your AN extension package but I will remove everything related
> to mcast to keep it as simple as I can.
>
> >> - Also, this solution involves a modified classifier.cc, which
> >> I would like to avoid unless I'm forced to use it (same reason
> >> as above).
> >
> >I don't think there is any way around this without modifying classifier.
> Since
> >all packets released by an agent in a node pass back through that node's
> entry
> >point, for active networking the entry point must be modified.   If a
> packet is
> >an active packet that has not been seen by the active agent at that node, it
> >should be forwarded to the active agent.  If a packet is an active packet
> that
> >has been seen by that node's active agent, it should be forwarded to the next
> >hop.  We added two fields to packets and modified classifier.cc to allow the
> >entry point to make that decision.
>
> Someone suggested here to attach the agent to the queue, instead of
> attaching it to the node. It looked like a good idea, but I am just
> realizing now that this approach would need a much higher number of
> agents (two per link instead of one per node), which wouldn't be a
> good thing for a large scale simulation :-(
>
> So I'm afraid that you are right and I cannot avoid having a modified
> classifier.cc.
>
> BTW, are you still working with active networks ? I have been
> studying you ants-based AER protocol and there are two or
> three questions that I would like to ask you, if you have the
> time.
>
> Thanks for your reply !
>
> Regards,
> G.
> --
> Guillermo Rodriguez Garcia
> <guille@iies.es>
>
> --
> Guillermo Rodriguez Garcia
> <guille@iies.es>