Network Analysis

Posted on 2007-07-23
Last Modified: 2010-03-05
I would like to run an analysis of the current bandwidth usage for a local school.  They are running alot of streaming video and have introduced Smartboards and Distance Learning(video conferencing).

I am concerned that we will run out of bandwidth and it will have a negative impact on the devices we are using.

Is there a good free or low cost program out there that will monitor the bandwidth usage for short and long periods of time, and then output that information in the form of a statistical report?
Question by:goeden
    LVL 25

    Accepted Solution

    depends on how your network is setup and the devices you have.  I swear by Ntop.  

    This can tell you what clients are using the network, how much bandwidth they are taking up, how long their sessions have been going on, what each protocol (configured by port monitoring) takes up, what servers are being communicated with, etc.

    Very nice tool.  The way I use it is I have a managed switch.  I mirror all the traffic of the port that the firewall is plugged into to the monitoring server.  I'm told you can use NetFlow as well, but I haven't used that route before so can't help if you need to use that method
    LVL 8

    Expert Comment

    modern network appliances make it really hard to get an idea of your total internal network capacity because non-blocking switching means that any node on the network can only see traffic that is sent to its ip range. You need to find the bottlenecks on your network, be that links between switches or internet bandwitdth or individual machines and measure at those specific points in the network.
    LVL 25

    Expert Comment

    I believe that's where NetFlow is suppose to come in, of course the network device must have that ability
    LVL 57

    Assisted Solution

    As Cyclops3590 has suggested, NTOP is great for this type of function.  If you have a device that supports NetFlow you don't have to do the port mirroring.  I have used NTOP with NetFlow (Cisco 6500's).  It basically "summirizes" the traffic and sends to NTOP which interperts it.  "Host A" sent/received X number of bytes over port 80/24555 to "Host B"/  You do not see every packet with NetFlow, just the summary.

    If you do not have a device that support NetFlow, then you can do one of the following:

    1) Mirror ports that carry the traffic you want to want, requires managed switch.
    2) Connect the devices you want to monitor and the computer running NTOP to a HUB.  This is cheaper than getting a managed switch if you don't have one, but depending on the traffic could cause performance problems.  A hub will change duplex from full to half, which in high volume situtations can reduce performance.  By high volume I mean that you are pushing 100 Mbps Eithernet to 70 Mbps or higher.
    3) If you don't care about what type of traffic is accouting for the network traffic and your switch is managed, get MRTG and just do SNMP queries on the ports you are interested in.
    LVL 25

    Expert Comment

    giltrjr mentioning MRTG made me think of another piece of software: Nagios.
    what I do for my internet link is monitoring it with Nagios using ping monitoring.  RTT gets too large and I get a warning.  Look at MRTG to see which interface is getting maxed out at the time, then open up the appropriate Ntop instance to find the specific abusing host and see if their bandwidth usage is legit or not.  If not, then collect all data, kill session, and track down user to inform them the misuse has been logged with HR.
    Just saying what I do anyway.
    LVL 3

    Expert Comment

    Ntop is really a good software for this purpose.

    Author Comment

    I will test out these options and let you know what works for me.  Thanks for the help.

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