Bandwidth Peek!



















    Just remembered one of those good and rare packet stream analysis tricks I learned in my Internet Real-Time Communications (VoIP) Course lab during Graduate school. I kinda wanted to share that with you my techie readers (or maybe not).
Well, first off you need to know how to use Wireshark the packet analyzer (the newest version of Ethereal actually).
Ok, so let's say you want to analyze the amount of bandwidth that was taken up by an application (could be a VoIP application or any other one).
What's bandwidth? In computer networks, bandwidth is often used as a synonym for data transfer rate - the amount of data that can be carried from one point to another in a given time period (usually a second). This kind of bandwidth is usually expressed in bits (of data) per second (bps). Occasionally, it's expressed as bytes per second (Bps).
Or maybe you want to know exactly if the voice application while running is hogging lots of bandwidth, making some other parts of the network get slow. You could better perform this by using other evolved or much more sophisticated or tools such as OPNET or Fluke-based tools.
To do this with Wireshark, we first need to get a good sample of the VoIP application while it is running in use. Remember that in order to capture this data, we will need to use a tap or a SPAN (Switch Port Analyzer) between client and server.This is where the SPAN function steps in, although as the name says, this is limited to switches only. SPAN or Remote SPAN (RSPAN), where monitored traffic can traverse a Layer 2 cloud or network, essentially creates an opportunity to capture and analyze traffic on two different switches that are part of a single Layer 2 domain (as opposed to a Layer 3 routing domain). To be able to get more details on how this is done, check out the following page: http://wiki.wireshark.org/CaptureSetup/Ethernet
Once a sample of application traffic is captured, we can then filter on the conversation between client (caller agent ) and server.
Next, using the I/O Graphs, we can generate a throughput chart for the concerned application. And voila! You have your bandwidth breakdown. The manipulation takes a little time to complete at first, but once you master it, you get to do that in a few minutes.

















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