Data transfer rate

Unanswered Question
Aug 23rd, 2008

Hi all,

My question is regarding data transfer between two server.Our customer generally complains they have 2mbps bandwidth between hub and remote site however when they are transferring data getting only data transfre rate 360kbps or less then 2mbps........Let assume this scenario over lan ..i have two servers connected via cross cable..i'm transferring data...how will i calculate the data transfer rate...

I have this problem too.
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spremkumar Sat, 08/23/2008 - 09:24

Hi Ajay

Are you measuring the same based on the download speed which normally displayed in Kilo Bytes / Second or you are checking the same via some monitoring system ???

if you are checking the same via some NMS then i would suggest to check the overall link utilisation coz the link usually contain some other traffic as well which mite slow up this download process.

if you are cehcking the same based on the download speed i m sure you mite be aware of deriving out the data transfer rate...

If its point to point 2 Mbps link between your locations you are assured to get the whole bandwidth 2Mbps up/down.

If its via some service provider ip cloud it totally depends on the SP backbone capacity as well the link capacity on both the pops where your locations are connected.

regds

ajaykumar2k1 Sat, 08/23/2008 - 09:45

thanks for reply

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if you are cehcking the same based on the download speed i m sure you mite be aware of deriving out the data transfer rate...

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here you caught my problem ???i'm not awrae of deriving out the data transfer rate...kindly advice the same.....

regards

Ajay Kumar

Calin Chiorean Sat, 08/23/2008 - 09:48

Hello there!

As the explanation from spremkumar for data transfer rate is complete, I just want to give you a hint to your problem. Maybe you are searching in the wrong place the problem, like it happened for me some months ago.

We had between 2 points 100 Mbits, but the traffic (mainly ftp) was reaching only about 4-5Mbits, which was extremely low for that capacity.After we tried for some time to investigate network problems (QOS, latency, routing...) somebody had the idea to replace the Microsoft FTP server with some free/common one. After that was working like heaven. It seems that Microsoft FTP had needed some patches (found out this from system engineers) and then it was working.

So my advice is to see what kind of traffic is mainly flowing through there and if everything is ok from software point of view.

I hope you will solve the problem. Good luck!

Cheers,

Calin

ajaykumar2k1 Sat, 08/23/2008 - 09:54

Thanks for reply calin ..

can u help me with how to derive data transfer ?

regards

Ajay Kumar

spremkumar Sat, 08/23/2008 - 10:21

Hi

Normally the download speed is represented in Kilo Bytes / Per Second and the link capacity in Kilo bits / per second. Hence you need to consider a multiplication factor of 8 with the actual value u see as download speed.

If you do any generic download even shows in KBps which u can convert as Kbps by multiplyin 8 to KBps.

Hope its clear now.

regds

ajaykumar2k1 Sat, 08/23/2008 - 10:49

thanks for reply ...

is there any formula we can calculate data transfer rate ...if we only know Bandwidth & ping time response between two servers...

i mean to say tcp throughput....

regards

Ajay kumar

Calin Chiorean Sun, 08/24/2008 - 01:50

Hi again!

The TCP throughput formula is:

TCP buffer size / RTT = TCP throughput

Let's say that we have 64Kbyte buffer and a RTT of 170ms:

(64Kbyte x 8bit) / 0.17s = 3011764 bps = 3Mbps

This is in perfect condition of network and so on.

I hope this help you :)

Cheers,

Calin

Joseph W. Doherty Sun, 08/24/2008 - 04:13

First you need to identify what the "data transfer rate" the customer is measuring. They might be measuring user data, i.e. payload, not total network data. The latter includes all the overhead placed on the wire.

For instance, if we're talking TCP over standard Ethernet, 1500 byte TCP packets normally contain 1460 bytes of user data. The other 40 bytes is IP and TCP overhead. (Can be more, resulting in even less space for data.) Additionally, a normal Ethernet frame will add another 18 bytes of framing overhead (also can be more if VLAN tagged) plus another 12 bytes for interframe gap and 8 for preamble. So, normally, of every 1538 bytes only 1460 is user data.

These two references will explain overhead further and touch on other media too.

http://sd.wareonearth.com/~phil/net/overhead/

http://www.tamos.net/~rhay/wp/overhead/overhead.htm

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