Re: about Mcast

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Subject: Re: about Mcast
From: Dave Plonka (plonka@doit.wisc.edu)
Date: Wed Jun 27 2001 - 08:29:32 CDT

[I'm sending this reply to a personal email to the list and am Bcc'ing
 the sender...]

On Tue, Jun 26, 2001 at 05:31:04PM -0400, someone wrote:
> Hi Dave:
>     Sorry to write to you here,I forgot the e-mail for the mailing list to
> ask question.

The mailing list is address "flowscan@net.doit.wisc.edu".
The pertinent info about the mailing lists is here:

   http://net.doit.wisc.edu/~plonka/FlowScan/#Mailing_Lists

>     Can you tell me what is the Mcast in Flowscan,

It is the traffic reported in flows that had multicast destination
addresses.

> CDEF_TOTAL_in_bits = CDEF:TOTAL_in_bits=MCAST_in_bits,total_in_bits,+
> 
> why you calculate this way  .

If the source address of the multicast traffic is not local (as defined
in "local_nets.boulder") then we count it is "inbound multicast"
because otherwise the border router that exported the flow shouldn't
have ever seen that traffic.

> what 's the different between TOTAL and total.

The capitalized "TOTAL" includes multicast, where as the lowercase
"total" is just unicast traffic.

(NetFlow currently isn't very good at accounting for multicast traffic
since, although it is reported, it doesn't tell you whether or not the
traffic was forwarded - and to which interface(s).  For that reason, I
tried to keep multicast and unicast totals seperate, except when the
two appear on the same graphs.)

Dave

-- 
plonka@doit.wisc.edu  http://net.doit.wisc.edu/~plonka  ARS:N9HZF  Madison, WI

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