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Re: qos routing



> From: Luis Henrique Maciel Kosmalski Costa <[email protected]>
> Date: Tue, 14 Apr 1998 15:06:33 -0300

> 	Now, let I tell you what I observed. Packet drops are allways 
> constant. I made the following test: when the link falls down, the routine
> intf-changed is called, and calls the "compute-routes" routines. Then the 
> routes are re-computed.

> 	I put a delay on that call to compute-routes. Result: the routes are 
> installed with a greater delay. It produces no new packet drops. But there 
> exists packets that are lost. They appear with + sign on out.tr, but there 
> are no correspondants "-" or "r's". So, they are lost.

a)  I doubt that the packets are actually "lost".
    You need to ensure that dropped packets are sent to
    the drophead_ in order to see them in the trace file.

    You should probably call the link method "trace-dynamics"
    to trace these drops.  (As an aside, and as I look at this
    code, I am beginning to wonder if the API for this could
    be improved some.)

> 	My conclusion: packet drops are registred only for packets which 
> were on the link (link queue) when the link goes down. The packets which are 
> sent on that link, when it is down, don't appear as drops. They just appear
> with the enque sign (+) on output.

b) There is no mechanism to drop packets within the node at this point.
   You could emulate the drophead_ concept of the link within each node.
   Then, you can point classifier entries to this drophead_ when you 
   want that node to drop packets for particular destinations.  However,
   this raises some questions about tracing that are not obviously clear
   to me.  You need to think about whether this will work for you, and how
   those results will apply to you.

> 	Am I right? If I am, I think I can simulate this increasing delays 
> as the routes processing increases. It will then be converted in packet 
> losses.


Kannan

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