Bandwidth Setting for Monitored Device

[Patrick McHenry]

We use SolarWinds for network monitoring. My question is about the bandwith setting that SolarWinds allows you to set for interfaces.

If I have a 20Mbs download and upload Internet circuit, and my interface connecting to the ISP modem is a 100Mbs interface and is running at 100Mbs because it has been set to Auto/Auto, what should I set the bandwith setting in SolarWinds to for the interface? I've been told by SolarWinds to set the bandwidth setting in SolarWinds for the interface to the bandwidth of the Internet circuit. So, I set the interface to 20Mbs receive and transmit.

Is this Best Practices? Something just doesn't seem right about it.

Thanks, Pat.

[Reza Sharifi]

Pat,

Even though the physical interface is 100Mbs, the ISP will rate limit the bandwidth to 20Mbps, which you are contracted to have.  So, probably setting to 20Mbps is more accurate.  You can also set it 100, but most likely you are not going to see more then 20.

HTH

Reza

[Patrick McHenry]

Reza, could you please clarify your answers?

When you say -  "So, probably setting to 20Mbps is more accurate" are you saying I should set the interface to 20Mbs in SolarWinds or the router WAN interface itself?

When you say - "You can also set it 100, but most likely you are not going to see more then 20" Are you saying if I set the interface to 100Mbs in SolarWinds, it will probably not go over 20% utilization? That wouldn't be good because reports would be hard to read. We would always have to do some math everytime we looked at a report. Managers don't like that

I guess the thing that is confusing to me is that the interface is moving traffic at 100Mbs. So, how can any monitoring of the traffic be accurate when we are trying to measure the bandwidth utilization of a 20Mbs circuit? I'm trying to wrap my mind around the logic of setting the bandwidth of an interface in SolarWinds to 20Mbs and how that will give a accurate utilization reading of a 100Mbs interface. Even it I was sending one byte of data, that data would be going 100Mbs accross the link, correct?

Thanks, Pat.

[Reza Sharifi]

Pat,

When you say -  "So, probably setting to 20Mbps is more accurate" are  you saying I should set the interface to 20Mbs in SolarWinds or the  router WAN interface itself?

No, you don't set anyting on the WAN interface.

I am not familiar with SolarWinds, but what I am saying is if the incoming interface from the service provider is a 100Mb interface, and SolarWinds sees the interface as 100Mb also, you are not going to see the download speed of the interface being more then 20% of that.

When you say - "You can also set it 100, but most likely you are not  going to see more then 20" Are you saying if I set the interface to  100Mbs in SolarWinds, it will probably not go over 20% utilization? That  wouldn't be good because reports would be hard to read. We would always  have to do some math everytime we looked at a report. Managers don't  like that

But that is what you are paying for.  You are paying for 20Mb and not 100Mb right?  So, when you look at the graph and the link is fully utilize you are going to see a total of 20Mb.  For example, my verizon at home is set at 5Mb download and if I download 5 files and each file is 100Mb, I see the download speed being 1Mb per file for a total of 5Mb, but the copper interface on the router is 10/100 and I am not even close to that.

I guess the thing that is confusing to me is that the interface is  moving traffic at 100Mbs. So, how can any monitoring of the traffic be  accurate when we are trying to measure the bandwidth utilization of a  20Mbs circuit? I'm trying to wrap my mind around the logic of setting  the bandwidth of an interface in SolarWinds to 20Mbs and how that will  give a accurate utilization reading of a 100Mbs interface. Even it I was  sending one byte of data, that data would be going 100Mbs accross the  link, correct?

The interface is rate limited to 20Mb by the serive provider.  If you want the full 100Mb, you would most likley need to pay more $$$.

HTH

Reza

[Giuseppe Larosa]

Hello Patrick,

I'm sorry for the basic question:

but isn't your router shaping outbound to  a rate within 20 Mbps?

Do you expose your user traffic to SP drops by sending traffic at line rate without shaping?

If a shaper is implemented you should be fine with setting the reference banwdith to 20 Mbps on the management SW so that the traffic graphs are scaled to the agreed CIR.

Hope to help

Giuseppe

[Joseph W. Doherty]

Disclaimer

The  Author of this posting offers the information contained within this  posting without consideration and with the reader's understanding that  there's no implied or expressed suitability or fitness for any purpose.  Information provided is for informational purposes only and should not  be construed as rendering professional advice of any kind. Usage of this  posting's information is solely at reader's own risk.

Liability Disclaimer

In  no event shall Author be liable for any damages whatsoever (including,  without limitation, damages for loss of use, data or profit) arising out  of the use or inability to use the posting's information even if Author  has been advised of the possibility of such damage.

Posting

When working with circuits which have logical bandwidth caps lower then their physical media support, generally I've defined monitoring to reflect the logical cap.  Remember monitoring is really reporting average bandwidth utilization, not individual frame/packet transmission rate.

Often, I've used monitoring tools that "pick up" the logical bandwidth from an interface's bandwidth statement.  Don't know if SolarWinds does.  But even if not, you might want to set the interface bandwidth statement too, as this then will reflect load rates on the interface to the logical cap.

[Patrick McHenry]

Joseph,

SolarWinds picks up the port speed automatically and that is my problem because the speed between the router and the modem is 100Mbs but the circuit is only 20Mbs. So, are you saying that by configuring the interface setting to 20Mbs in SolarWinds I should get an accurate reading? This is what I have been doing - I really just wanted to be sure.

This raises another question that Guiseppe raised . Should we be shaping traffic leaving the router and coming into the router? By not shaping, couldn't we risk having packets dropped?

"Remember monitoring is really reporting average bandwidth utilization, not individual frame/packet transmission rate."

                                                                 That sentence makes sense to me. Cleared things up a bit.

Thank you.

[Joseph W. Doherty]

Disclaimer

The   Author of this posting offers the information contained within this   posting without consideration and with the reader's understanding that   there's no implied or expressed suitability or fitness for any purpose.   Information provided is for informational purposes only and should not   be construed as rendering professional advice of any kind. Usage of  this  posting's information is solely at reader's own risk.

Liability Disclaimer

In   no event shall Author be liable for any damages whatsoever (including,   without limitation, damages for loss of use, data or profit) arising  out  of the use or inability to use the posting's information even if  Author  has been advised of the possibility of such damage.

Posting

SolarWinds picks up the port speed automatically and that is my problem because the speed between the router and the modem is 100Mbs but the circuit is only 20Mbs. So, are you saying that by configuring the interface setting to 20Mbs in SolarWinds I should get an accurate reading? This is what I have been doing - I really just wanted to be sure.

Yes, if the circuit won't permit more than 20 Mbps, having your monitoring reflect that provides more a relevant measure.  For example, if the circuit is running at 10 Mbps, that's 50% of your capacity, but only 10% of the interface bandwidth.  Normally, you'll want to measure the former and not the latter.

This raises another question that Guiseppe raised . Should we be shaping traffic leaving the router and coming into the router? By not shaping, couldn't we risk having packets dropped?

I would recommend shaping for egress.  It queues first, and it gives you the opportunity to prioritize the how traffic is dequeued.