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LAN Speed Measurements

Posted on 2014-02-11
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Last Modified: 2014-02-14
To be specific and get right to it. I was transferring a large disc image ~4GB from a USB 3.0 external disk to a share on a server using a desktop machine.

I believe USB 3.0 is 5 Gb/s and I believe my LAN is either Gb or 100Mb. All the intervening hardware is high end or SMB class (switches, routers and machines).

So though windows 8.1's performance monitoring option I watched the transfer which takes a couple of minutes. During this time the graph pretty consistently showed 11Mb/s. Seems a little slow to me given the hardware even considering some overhead.

So, is that slow? If so, how can I quantify this in general? What is the best way to monitor and test for and ultimately track down bottlenecks. I would like to see where and what and what it would take to eliminate these choke points.

Thanks
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Question by:mohrk
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by:Dave Baldwin
ID: 39851909
11MBytes/s sounds just about right for large file transfers over a 100Mbit/s network.  Networks are rated in 'bits per second' and file transfers are measured in 'bytes per second'.  Add a little overhead and that sounds about right.  If it was the same amount of data but in small files, it would take a lot longer because of the additional overhead to open and create the many files.

All you have to do is spend lots of money making sure that all hardware runs at a 1Gbit/s (or faster and testing it to make sure it works up to speed.
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by:mohrk
ID: 39851976
Dave,

Thanks for the clarification. You are right I did forget to account for the larger byte size even having just viewed a Google hit on the topic.

Hmmm, I was hopping for something a little more low end. Like recently I had an issue with an SMTP session and I just had to "see" the actual exchange and determine programatically on the development side what the actual failure was. So, wireshark some protocol filtering and some remote end to end timing and I had the problem narrowed do to a specific expression on a line of code.

Since it took me some time to do this including determining and gathering the tools I wondered if I could short circuit this step and find a low cost out of the box solution to a problem that has certainly seen more daylight than the problem I was working on, referring to the code not  necessarily the problem itself.
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by:Dave Baldwin
ID: 39852166
I don't understand some of your comments.  I don't see that there is any failure in your current process.  You just want more speed than you are currently getting.

As far as I know, putting even one 100Mbit/s NIC on a Gigabit network brings all the traffic down to 100Mbits/s.  Any link in the path that is a 100Mbit/s connection will have the same effect.  Since you appear to be running close to the limits of a 100Mbits/s network, upgrading the hardware is the first solution that I would think of.  

You could possibly gain some speed by compressing and decompressing the data.  That only works if the data can be compressed a lot so that you would save more time in transmission than you are spending in compressing and decompressing.
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by:mohrk
ID: 39852210
Hi Dave,

I guess my goal wasn't clear. I have tried several different ways to ask questions here and there never seems to be a right way.

I started with a specific example and then wanted to generalize it. You say, yeah that's about right. How did you come to that conclusion? What were the factors you took in account? I know the whole fat pipe skinny pipe do the math and there you are thing,

What I was looking for was "I am a network <insert title of job> when we look for problems in the network as they relate to speed we start by using <insert tool/method here> and we put it <here> and <here> and we look at <these measurements> we then follow <this process> until we find <problem piece of equipment> and then we evaluate <these parameters> and gauge what if anything we are going to do about it."

My goal is information not more speed. How is it done?
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by:Dave Baldwin
ID: 39852406
I think you do have a funny way of asking questions.  This subject doesn't require a network engineer to answer.  And for the basics of connection speed, you just use the computers to get the info.  No extra equipment needed.

For the subject of "Is my network running as fast as it should?", you start with a few bits of knowledge.  First is the capability of different network interfaces.  100Mbits/s is a maximum of 12.5MBytes per second.  1Gbits/s is a maximum of 125MBytes/s.  That would be the speed without any overhead such as creating and reading/writing files and without any other traffic on the network.  Second is that networks usually run at the speed of the slowest interface on that segment.  So you need to find out what the network cards in each computer are capable of.  You also need to know the specs of the switches.

If want to find the speed of the individual computers, you can look at the properties/status of the network connection on that computer.  If your networks display in the task bar, you can right click on the icon and then click on status to see what speed it is running at.  On my computer on my right I have both a 1Gbit network connection and a 100Mbit connection to my two different networks.

You might also need to know what the capabilites of the network cards are because as I understand it, a given network runs at the speed of the slowest device on the network.  If you find all 1Gbit cards that are running at 100Mbits, you might then have to investigate how they are setup.  Every 1Gbit card that I've seen is configured for 'auto' so it will run at the speed of the network.  

If you find that one of the cards will only do 100Mbits/s, then you may have to replace it with a 1Gbit card.  Same goes for the switches.  And it is possible that your network cables are old and won't support the highest speeds.  Some of that also depends on distance / length of the individual cables.  All the ratings are done at 100 Meters max cable length.
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by:Gerald Connolly
ID: 39852882
100Mbits/sec = 10MB/s approx - you have to take into account 10 bits per byte at the hardware level. This means that 1Gbit/sec = 100MBytes/sec approx. That has been the defacto standard for 15+ years.

and as Dave said, this isnt Rocket science. If you have a pipe that only runs at 100Mb/s then that is going to restrict the flow between the systems.

Did you get 11Mbits/sec or 11MBytes/sec? and was that sustained or peak?

11MB/sec would be very good for a sustained throughput on a 100Mb/s constrained link.
11Mb/s isnt.

You need to check how fast you can get data off the disk in the first place. Just because a pipe is 5Gb/s it doesnt mean the device can actually transfer data that quick (they usually cannot even get near).

You need to consider the following points on diagnosing why this transfer is slow.
1) Speed of the disk
2) Throughput of the Disk-2-USB interface
3) Quality of the cable
4) The software you are using to do the transfer
5) The amount of RAM available
6) the speed of the disks being written to
7) activity on the disks being writen to
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by:mohrk
ID: 39860661
I got 11 MB/s assuming Megabytes. What is one to conclude from this? What does that say about the network? Say this is good but I have a super fast as yet unknown configuration that would not speak to this as "being good/bad".

I am looking for a way to MEASURE. Not estimate or guess or whatever. Certainly there has to be a way to do this. If it is really really expensive to even get reasonably close fine. If not how/what does one do to find this value?  

As far as "rocket science" throw a pile of lumber and nails, hammer and saw at me and say "frame a wall" and do not mention a measuring tape and a level and a plumb bob.
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Dave Baldwin earned 500 total points
ID: 39860846
What is it you think you will measure?  I explained how it works and you still seem confused.  11 MB/s is a MEASUREment.  But... as I explained above, the actual speed on the network is a negotiation between the interfaces and the fastest speed that ALL of them support is the speed that the network operates.  

If you have 9 1Gbits/s cards and 1 100Mbits/s card on your network, it will run at 100Mbits/s so ALL of the cards will receive the broadcast packets.  Remove that single 100Mbits/s card and that network can run at 1Gbits/s.  The actual speed you get on a network also depends on the other network traffic because you are sharing the network with other computers and devices.  

If one other computer is trying to make the same file transfer that you are at them same time, your speed will be cut in half because you are sharing the network with them.  If 9 other computers are trying to do the same thing, your speed is now down to 1/10th what it would be capable of if your computer was the only one on the network to the server.

Every Windows or Linux computer will tell you in the status for the network card what speed it is running at.  You have to look up the specs for the card to know what it is capable of because it could be running at a slower speed than it is capable of.  I know of nothing that will tell you what the overall network usage is because it is always changing.
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Author Comment

by:mohrk
ID: 39860854
Did you see that you had to add 4 characters to the end of the word? That is because you changed a verb into a noun. I am still confused because you have not answered the question.

The questions is, if I have 1 100Mbits/s card, how do I know I have it? If in the basement there is a 100Mb/s network card and I don't know its there but I know two computers have 1Gb/s cards how do I find the 100Mb card in the basement? I have to start at one end or the other and MEASURE something until I find the thing that does not MEASURE what I expected it to.
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Author Closing Comment

by:mohrk
ID: 39860861
Dave,

This is starting to become abusive. Part of what I was after besides an answer to the question was to gauge the value I get out of the subscription. It turns out that it's hit or miss. Sometimes you ask the right question in the right way (even though you are not knowledgeable about the subject) and you get lucky and find someone helpful, sometimes you get nothing. I think I will gamble my money elsewhere and have more fun with it.
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by:Dave Baldwin
ID: 39860922
Good luck, thanks for the points.
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