Apparently, many WAN Optimization companies price their appliances based on Flow Volume.  What does Flow Volume mean?  Flow Volume is the number of concurrent flows on a specific interface or all interfaces at any given time.  For example, if you download a web page, this could create several flows.  If you ping something, this would create a flow as well.  In fact, syslogs, SNMP traps, etc. all create flows.  TCP tends to create flows that linger longer than ICMP or UDP flows.

How Does this Help with WAN Optimization?
I had a customer point out the other day that they use Scrutinizer for WAN optimization sizing.  “Really, how so?” I asked.  “The Flow Volume report tells me how many TCP flows we have on a link at any given time” he said.  This is true, one of the free reports in Scrutinizer displays the volume of flows per minute (or second if necessary).  It trends a rate/second and you get a total per interval <see below>.


The customer explained that some WAN Optimization vendors charge more specifically based on TCP Flow count.  Scrutinizer allows you to easily add filters to include or exclude just about any field in a NetFlow datagram.  Because of this Scrutinizer report, he is able to buy the appropriate hardware without fear of spending too much for equipment he doesn’t need.

WAN Optimization Vendors
• BlueCoat
• Cisco WAAS
• Expand
• Riverbed
• Silver Peak

Mind Your Flows
Before you buy, make sure the appliance supports NetFlow and ideally, NetFlow v9 with egress flows.  Why? Read this brief blog on Best Practices for Cisco WAAS Reporting using NetFlow.  It applies to all vendors.

Mike Patterson author pic


Michael is one of the Co-founders and the former product manager for Scrutinizer. He enjoys many outdoor winter sports and often takes videos when he is snowmobiling, ice fishing or sledding with his kids. Cold weather and lots of snow make the best winters as far as he is concerned. Prior to starting Somix and Plixer, Mike worked in technical support at Cabletron Systems, acquired his Novell CNE and then moved to the training department for a few years. While in training he finished his Masters in Computer Information Systems from Southern New Hampshire University and then left technical training to pursue a new skill set in Professional Services. In 1998 he left the 'Tron' to start Somix which later became Plixer.


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