Guideline on Network performance Monitoring !

[Chris Fung]

Hi there,

Just wondering if there is any webpages / documents stated the general good practise on how to correlate and evaluate the network performance report.

I am having trouble to evaluate the figures in the report e.g. What is the accepatble level of the bandwidth utilization 70%, 80%? I am using MRTG to perform link (lease line) utilization monitoring.

Many thanks,

Chris,

[Ron Kinner]

It's not really the absolute % that matters. If you had steady state data then you could happily run at 99% if the link was only used by computers talking to themselves. What hurts is when you have real people involved. Then the peaks to 100% and the packets that fall out of the queue during the peaks are critical. These activate TCP/IP's congestion avoidance routine which slows the response and annoys the users who then complain to your boss that the network is slow. Point MRTG at the OID for your device which counts dropped packets on the input queue to the serial link and you will be able to see if you already need to upgrade. (If you are already dropping lots of packets then playing with queuing strategy can buy you some time while you try to get a capacity upgrade. On a Cisco device you can usually use custom queueing and also adjust the maximum number in a queue.)

Other things you have to take into consideration are how fast your data is growing and how long it takes to get more capacity (which includes the time to prepare the business case, get it approved, order the upgrade, delay before installation, installation time, testing and waiting for an available downtime window). Bear in mind that the peaks will start clipping long before you get to 100% average usage. (If you are working with MRTG historical graphs make sure you have the option "with peak" set in the config file.)

Sorry I don't have a website or book to reference. This is just experience speaking.

Ron

[LucianoCarvalho]

hi,
Here is some information about acceptable treshold for utilization.

Long term monitor (average figure, sampling duration 1 hour or greater)
??? 10 Mb/s Ethernet
??? 37% == 3700 kbps == 462.5 kbytes/sec
??? 40% == 4000 kbps == 500 kbytes/sec
??? 100 Mb/s Ethernet
??? 37% == 37000 kbps == 4625 kbytes/sec
??? 40 % == 40000 kbps == 5000 kbytes/sec
Short term monitor (average figure, sampling duration 15 minutes)
??? 10 Mb/s Ethernet
??? 70% == 7000 kbps == 875 kbytes/sec
??? 100 Mb/s Ethernet

http://www.m2technologies.net/html/ethernet.pdf

??? 70% == 70000 kbps == 8750 kbytes/sec

Cisco also suggest tha broadcast per second can not be more than 100.

regards

[Uday_S_Ankolekar]

This doc might help

http://www1.itrc.hp.com/service/cki/search.do?category=c0&mode=id&searchCrit=allwords&docType=Security&docType=Patch&docType=EngineerNotes&docType=BugReports&docType=Hardware&docType=ReferenceMaterials&docType=ThirdParty&searchString=23222dhtm