RE: [ns] Mac & IFq communication query

[Neundorf Alexander <Alexander.Neundorf.extern@icn.siemens.de>]

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Free Dmitry Sklyarov ! 
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> -----Original Message-----
> From:	Andrew Tang [SMTP:atang@cse.unsw.EDU.AU]
> Sent:	Monday, September 17, 2001 6:49 AM
> To:	ns-users@ISI.EDU
> Subject:	[ns] Mac & IFq communication query
> 
> 
> 
> Hi,
> 
> I'm having some trouble understanding how the IFq communicates with MAC,
> this line in particular
> 
> ll.cc
> 	// let mac decide when to take a new packet from the queue.
> 		s.schedule(downtarget_, p, delay_);
> 
	This line means that after delay the Scheduler calls downtarget.handle(p). This means that Queue::recv(p) is called. This appends p to the Queue. Now we have to cases. If the queue is not blocked, the Queue calls itself downtarget->recv(p) where as p is now the first packet from the queue. Bye calling downtarget.recv() the queue changes into blocked state. In this state Queue::recv(p) doesn't yield a call to downtarget(of the queue).recv(), but it simply means that p will be added to the queue.
	Mac received in the first case the first packet from the queue. After it has finished processing this packet, it will call handler->handle(); whereas handler is the handler from the recv() method, i.e. the queue. Queue::handle() calls Queue::resume(), which dequeues the next packet and sends it to the down target.
	Fortunately this doesn't lead to a recursion  (although I don't understand exactly why, probably due to the scheduler).

	Bye
	Alex