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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:jahn@ISI.EDU]
> 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:hbl@msrchina.research.microsoft.com]
> 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:jahn@ISI.EDU]
> > Sent: Saturday, July 07, 2001 5:21 AM
> > To: Hong Bin Liao
> > Cc: ns-users@ISI.EDU
> > 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
> > 
> > 
> > 
> > -----Original Message-----
> > From: owner-ns-users@ISI.EDU 
> > [mailto:owner-ns-users@ISI.EDU]On Behalf Of Hong Bin Liao
> > Sent: Friday, July 06, 2001 6:01 PM
> > To: NS-2, USERS (E-mail)
> > Subject: [ns] issues on ErrorModel AGAIN!
> > 
> > 
> > Hi, Folks
> > 	I sent the following letter several days before. I got no answer
> > for it. IMHO, it's very fatal issue on the correctness of 
> model of the
> > systems. Could anyone give me answer of it?
> > 
> > Hi, folks
> > 	after reading the source code of errmodel.cc, I wonder why the
> > resume handler should be delayed for a random period between 0 to
> > (PacketSize/BW). why not this packet with error is delayed 
> > for a period
> > (PacketSize/BW)?
> > 	The former cause more burst error when error unit is bit, byte
> > or time (in two/multi state error model).
> > 
> > 
> > HongBin L.
> > 07/06/2001
> > 
> > 
>