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Interface Bandwidth

Hi Experts,

Need your suggestion on an interface bandwidth part which is confusing me a lot.

How do we measure the interface bandwidth i.e if I have an interface 2MB E1, when I see the link utilization in my monitoring tool (live ) its shows in that incoming traffic bandwidth 1.6 MB and out going traffic bandwidth 1.2 MB. So If I add its comes ot to be 2.8 MB. but the link is 2 MB only.

I need some inputs on this that how we measure the bandwidth of an interface. If I see the CLI output " show int s x/y " it shows me last 5 minutes input.

Just confused on this part.

regards,

-amit singh

4 REPLIES

Re: Interface Bandwidth

Hi

I hope you are aware that when we say 2Mbps link it means both in and out has 2Mbps capacity.

if u put it on simple term its as same as Fullduplex fastethernet where u got the advantage of having 100 up and 100 down in a 100Meg fullduplex interface..

The 5 min in/out rate displayed by the show interface stats are approximate values for the admin to understand the traffic flow through that particular interface at a given point of time.

To be more specific we can ofcourse change the limit thts the time to 30 seconds.the same can be done using load-interval comand under those particular interface which can be of more accurate than the 5 min values..

More about the in/out traffic rate do find the statement below..

Average number of bits and packets transmitted per second in the last 5 minutes.

The 5-minute input and output rates should be used only as an approximation of traffic per second during a given 5-minute period. These rates are exponentially weighted averages with a time constant of 5 minutes. A period of four time constants must pass before the average will be within two percent of the instantaneous rate of a uniform stream of traffic over that period.

regds

Re: Interface Bandwidth

Hi Prem,

" A period of four time constants must pass before the average will be within two percent of the instantaneous rate of a uniform stream of traffic over that period. "

Didnot get this line.

So what I understood form your post that its a full-duplex transmission and I can get 4 MBPS total in both the direction i.e 2MBPS in each direction i.e the link is capable of transmitting 2MB in each dir. Am I right ??

So the MAX utilization that I can take on that interface at any particular time would be the MAX traffic in any direction ??? and that will become my Max utilization ...the same goes for current utilization as well.... Your comments...

regards,

-amit singh

Re: Interface Bandwidth

Hi

Yes Amit you are rite in each direction its capable of handling 2Mbps.

As far as the max utilisation is concerned we used to give the reference on both the in as well as the out directions.

If you get choked at any side of the link (either in or out) that would ofcourse have an adverse effect on the speed and also in the performance of the link .

regds

Re: Interface Bandwidth

Thanks Prem, I got your point. thanks for you help Mate :0)

regards,

-amit singh

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