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[ns] Packet header related doubt
Hello All,
I want to add a new packet headrer in my ns code. The
example says that I need to add the node to the
ns-packet.tcl file in the following place:
foreach pair {
{Common _off_cmm}
..................
{Newhdr _off_newhdr}
}
But in ns 2.1b8 I see that code commmented and stated
as old code...
So where should I add new definition in this case noe
?
Regards,
-Sameer.
--- Hong Bin Liao
<[email protected]> wrote:
> Since the outrage of our mail server, sorry for this
> very late mail.
>
> > -----Original Message-----
> > From: jahn-isi [mailto:[email protected]]
> > Sent: Thursday, July 12, 2001 7:59 AM
> > To: Hong Bin Liao
> > Cc: NS-2, USERS (E-mail)
> > Subject: RE: [ns] issues on ErrorModel AGAIN!
> >
> >
> > I am not sure why the code for inserting random
> delay after
> > dropping a packet
> > is there. But it turns out that the test suites
> for executing
> > that code are
> > three, test-suite-session.tcl,
> test-suite-mixmode.tcl, and
> > test-suite-srm.tcl.
> >
> There are also several other tests with error module
> by grep 'lossmodel'
> in tcl/test.
>
> These test suites only test insert-loss which
> inserts the error model
> before the queue. IMHO, it can not simulate the link
> error model. The
> packet loss is different from packet error.
>
> > And they want to call the queue resume function
> after some
> > random delay
> > whose average is the transmission delay after
> dropping some specified
> > packets. In these three test scenario files, they
> set the
> > packet type to
> > drop by using the command "drop-packet" when they
> set the drop-target
> > with the null agent. I guess that this code is
> just for their
> > experiments. I
> > am not sure why. Is there anybody who knows why??
> >
>
> The average delay is only half of the transmission
> delay rather than the
> transmission delay since uniform(r) only generates
> random value from [0,
> r) uniformly.
>
> After checking the CVS log of errmodel.cc, it is
> changed at revision
> 1.38 to use bandwidth_ to determine when to resume
> the queue (however,
> it use the random value between [0,transmission
> delay), WHY?). Before
> that revision, the error module resumes the queue
> handler after
> 0.000001s.
>
> > But normally when packets are delivered over
> target which is a neigbor
> > after the error module decides whether or not the
> packets
> > will have errors.
> > So, other test suites are not affected by this
> code at all.
> >
>
> No true. The test suite never test the error model
> using link-lossmodel.
>
> For network with link error, e.g. wireless network,
> the error model is a
> key issue for the simulation.
>
> HongBin
> 07/18/2001
>
>
> > -jahn
> >
> >
> >
> >
> > > -----Original Message-----
> > > From: Hong Bin Liao
> [mailto:[email protected]]
> > > Sent: Wednesday, July 11, 2001 10:22 AM
> > > To: jahn-isi
> > > Cc: NS-2, USERS (E-mail)
> > > Subject: RE: [ns] issues on ErrorModel AGAIN!
> > >
> > >
> > > Hi,
> > > Sorry if the problem I stated is not so clear.
> > >
> > > the queue in ns-2 is resumed after a packet is
> transmitted, i.e.
> > > after txtime() in delay.h (8. *
> hdr_cmn::access(p)->size() /
> > > bandwidth_). However, after an error model is
> inserted
> > before the link
> > > module, it will drop packet after detecting it
> is
> > corrupted. Then, the
> > > error module try to schedule the handler to
> resume the queue after
> > > Random::uniform(8.0 * ch->size() / bandwidth_)
> seconds, that means a
> > > corrupted packet will trigger the queue resume
> handler
> > earlier than a
> > > correct packet. In the other word, a corrupted
> packet will take less
> > > bandwidth than a correct packet.
> > >
> > > Hongbin
> > > 07/11/2001
> > >
> > > > -----Original Message-----
> > > > From: jahn-isi [mailto:[email protected]]
> > > > Sent: Wednesday, July 11, 2001 1:48 AM
> > > > To: Hong Bin Liao
> > > > Subject: RE: [ns] issues on ErrorModel AGAIN!
> > > >
> > > >
> > > > I am not sure that I can understand your
> stated problem.
> > > > -jahn
> > > >
> > > > -----Original Message-----
> > > > From: Hong Bin Liao
> [mailto:[email protected]]
> > > > Sent: Tuesday, July 10, 2001 11:53 AM
> > > > To: jahn-isi
> > > > Cc: NS-2, USERS (E-mail)
> > > > Subject: RE: [ns] issues on ErrorModel AGAIN!
> > > >
> > > >
> > > > In the NS-2 implementation, error model is
> insert before the queue
> > > > module or the link module. For the insertion
> before the link
> > > > module, if
> > > > a corrupted packet is immediately dropped and
> the resume
> > > > handler of this
> > > > packet are invoked after a random period
> between 0 to
> > (PacketSize/BW).
> > > > This means a corrupted packet consumes less
> bandwidth
> > than a correct
> > > > packet. There is also another fatal issue for
> time
> > continuous error
> > > > model, since a corrupted packet takes less
> flight time
> > than a correct
> > > > packet, it cause more burst error than error
> model with
> > bit, byte, etc
> > > > as the error unit.
> > > >
> > > > -hongbin
> > > >
> > > > > -----Original Message-----
> > > > > From: jahn-isi [mailto:[email protected]]
> > > > > Sent: Saturday, July 07, 2001 5:21 AM
> > > > > To: Hong Bin Liao
> > > > > Cc: [email protected]
> > > > > Subject: RE: [ns] issues on ErrorModel
> AGAIN!
> > > > >
> > > > >
> > > > > I am not sure why there is a delay before
> notifying the packet
> > > > > corruption to the module called the error
> model.
> > > > >
> > > > > But, corrupted packets are immediately sent
> to the
> > specified target
> > > > > (which is a neigbor node's link layer or
> the next low layer
> > > > > in wireless networks)
> > > > > without any delay after scheduing the
> notification event
> > > > > with some arbitrary
> > > > > delay.
> > > > >
> > > > > You can see this flow by using a gdb
> debugger.
> > > > > -jahn
> > > > >
> > > > >
>
=== message truncated ===
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