RE: packet sampling point

From: Peter Phaal <>
Date: 10/21/09
Message-ID: <98552135AAC44408A6C8FA490C6A198E@PHAALPC>

The sampling point occurs after the packet has been accepted for processing.

>>From section 3.1 of the sFlow version 5 specification,

   Packet Flow Sampling is accomplished as follows: When a packet
   arrives on an interface, the Network Device makes a filtering
   decision to determines whether the packet should be dropped. If the
   packet is not filtered a destination interface is assigned by the
   switching/routing function. At this point a decision is made on
   whether or not to sample the packet.

You should also look at the definition of Packet Flow and Packet Flow
Sampling in section 2. Terminology and Architecture.


> -----Original Message-----
> From: [] On Behalf Of
> sujay gupta
> Sent: Wednesday, October 21, 2009 2:34 AM
> To:
> Subject: [sFlow] packet sampling point
> Hi Group,
> Should sFlow capture packets on the wire or only those packets which
> the device has to process?
> For example if the packet, ether mac is not the NIC's it will be
> dropped before L2 processing( assume no bridging) , but then should
> sFlow , packet sampling should sample this packet?
> If it does the flow info would not be what is crosssing the switch.
> Consider a broadcast link on a switch where there is numerous
> crosstalk between hosts, the sFlow would send all this data as flow
> info, even though it has not participated in it !
> Is this what the collector is interested in?
> BR,
> -Sujay
Received on Wed Oct 21 06:55:23 2009

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