Re: vlan.tcl delay - bug?

[Wing-Chung Hung <hungw@jupiter.nal.utoronto.ca>]

Here are my understand:

1.

LL is a child of DelayLink which is a child of link.
In a point to point connection (not lan), the delay_ of link, I think, is
the propagation delay (the time it take for a bit of information from
transmitter to receiver) and there is no channel in such topology.

2.

when I create a lan using make-lan

  set lan [$ns make-lan $nodelist $bw $delay LL Queue/DropTail Mac]

I am thinking that the $delay is the delay is the propagation
(channel) delay between a transmitting and a receiving node.  I.e. it
should be the delay_ of a channel.

In channel.cc, delay_  actually means propagation dealy and is used for
collison calculation.

double 
Channel::get_pdelay(Node* /*tnode*/, Node* /*rnode*/)
{
	// Dummy function
	return delay_;
}

By assigning the $delay to the delay_ of LL, this delay means the amount
of time the packet stay in a node before being send to it's downtarget_
which is the queue.  This is reflected in ll.cc

from ll.cc

void LL::sendDown(Packet* p)
{	
	...
	if (tx == 0) {
		Scheduler& s = Scheduler::instance();
		s.schedule(downtarget_, p, delay_);
	}
}


My conclusion is that the $delay argument in make-lan
  
  set lan [$ns make-lan $nodelist $bw $delay LL Queue/DropTail Mac]

means the inbound processing delay (the amount of time to stay in the node
before being queue for transmission), and is not related to propagation
dealy.

Please comment.

Thanks.

-- Wing-Chung



On Wed, 5 Jan 2000, Tarik Alj wrote:

> that delay is not a transmission delay, but more of a latency delay; as I 
> understand it...
> 
> 
> > X-Authentication-Warning: mash.CS.Berkeley.EDU: majrdomo set sender to 
> owner-ns-users@irtf.CS.Berkeley.EDU using -f
> > Date: Tue, 4 Jan 2000 19:29:01 -0500 (EST)
> > From: Wing-Chung Hung <hungw@jupiter.nal.utoronto.ca>
> > X-Sender: hungw@uranus
> > To: ns-users@mash.cs.berkeley.edu
> > Subject: vlan.tcl delay - bug?
> > MIME-Version: 1.0
> > 
> > 
> > Hi,
> > 
> >   In vlan.tcl of ns-2.1b6-current, link delay is set to the delay of LL.
> > However, I think the delay should be set to that of channel becasue
> > channel is when the delay really occured.
> > 
> >   Can someone comment?  Do I missing or misunderstand something?
> > 
> >   Thanks.
> > 
> > -- Wing-Chung
> > 
> > 
> > from vlan.tcl:
> > 
> > LanNode instproc addNode {nodes bw delay {llType ""} {ifqType ""} \
> >                 {macType ""} {phyType ""}} {
> > 		
> > 		 ...
> > 
> >                 set ll [$nif set ll_]
> >                 $ll set delay_ $delay
> >                 $ll varp $varp_
> > }
> > 
> > there is no setting of channel_::delay_ in vlan.tcl
> 
> Tarik 
> 
>