Re: Classifier and Routing?

[K Sun <ksun@essex.ac.uk>]

Hello,

     Really thanks for your further discussion!

> 	here's what i've been able to understand from ns-node.tcl and 
> classifier.h and .cc:

      I only read some parts of the three files above andI have not 
completely looked through these three files. I will try it later.
 
> 	- The same kind of classifier (classifier-address.cc) is used both for 
> port and address classification.
   
       For this point, I still think the classifier 
(classifier-address.cc) is only used for address classification. In 
another word, only this classifier has something to do with Routing. 
         
> 	- This classifier applys a bit shift to the address field to get rid of 
> either the address or the port #. Then a mask (with a bitwise AND) to make sure 
> the address (port#) is correctly taken.

        Maybe I am confused. However, I think it is not one bit shift. 
The number of bits which should be shifted is stored in the variable 
"shift_" and the operation of classify() in AddressClassifier is only 
for extracting the address, instead of port number. I think it should 
be operated in this way, although I am not sure of it. 

> 	- at an ns node the classifier is set-up like this (pretty much):
> 
> 	DA     slot
> 	self   -> dmux -> agents
> 	n1     -> link1
> 	n2     -> link2
> 	n3     -> link1
> 	
> 	for a topology, say, like this:
> 	
> 	n2---------n0--------n1-------n3 	
> 	    link2      link1
> 	    
> 	Where dmux is a port classifier (an address classifier with a shift&mask 
> to get the port #).

         The only difference between you and me is: 
(my understanding)

DA     slot
self   -> dmux
n1     -> link1
n2     -> link2
n3     -> link1
 	 

And the cast between "dumx" and "agents" has been completed just during 
the initiation of agents.

      I try to further study it.

      Best Regards,

              Sun Kai      



> 	I hope that clarifies it, and if i have made mistakes people on the list 
> can correct me (please do so).
> 	Sincerely,
> 	
> 	Tarik.
> 
> > From: K Sun <ksun@essex.ac.uk>
> > To: Tarik Alj <aljtarik@ozias.inrs-telecom.uquebec.ca>
> > cc: ns-users@mash.cs.berkeley.edu
> > Subject: Re: Classifier and Routing?
> > Date: Sat, 2 Oct 1999 22:21:14 +0100 (GMT Daylight Time)
> > X-Authentication: IMSP
> > MIME-Version: 1.0
> > 
> > Hello,
> > 
> > > 	The classifier at a node is filled in ns-node.tcl, Node instproc 
> > > add-route; wich is called in ns-route.tcl's Simulator compute-flat-routes. 
> > 
> >     Thanks a lot! In the meantime, I am really sorry that I was not 
> > careful enough although I wanted. Currently, I know deeplier the 
> > relation between classifier and routing. Really thank you for your help.
> > 
> > 
> > > Concerning the classify() function, i 'm also trying to figure it out, 
> > > particularly the port classification: it seems classification happens on 
> adress 
> > > and on port # at the same time? 
> > 
> >     Yes, it is a problem indeed. According to my understanding, 
> > classifiation does not happens on address and on port at the same 
> > time. The slot array of port classifier has been set just after we 
> > attach an agent to this node. So, the slot array of port classifier 
> > always keep right. Everytime, Routing just configures the slot array of 
> > address classifier ( in the Unicast Node). The statement about 
> > add-route on page 37 gives me such impresssion. 
> > 
> > 
> > > What if I need to access to different headers at 
> > > the same time to classify?     
> > 
> >     I do not know this question clearly. Why you need to access to 
> > different headers at the same time to classifier? I think the routing 
> > only use address field of a packet.
> > 
> >    I really appreciate your help !
> > 
> >    Best Regards,
> > 
> >    Sun Kai
> >   
> > 
> >...