Regarding Link bandwidth utilization

[vaishalin]

Hi

I have one query regarding bandwidth utilization.

We are having LAN with connected to switch with 1gbps ports.

Now servers are connected to this switch and are negotiated with 1gbps speed.

This lan is connected to router having WAN link of 24 MB ( 2MB * 12 in multilink).

Now when we are sending file of 1gbps at a time we are not utilizing 24MB link at 100%.

But at night when there are parallal file transfersof larger sizes like 1gb  it gets utilized 100%.

Now my query is when we transfer 1gbps why 24mbps pipe is not at 100%

I want to clear how full bandwidth of any link reaches to 100%.

Also if any document to clear this concept pls let me know.

Regards

Vaishali

[paolo bevilacqua]

Which transfer rate are you getting for a single file transfer ?

[Giuseppe Larosa]

Hello Vaishali,

if the link use of the bundle during a single transfer is not 100% of 12 2Mbps links but is more then one single 2 Mbps the multilink is working fine.

The question may be derived by the TCP window size and the delays involved the so called bandwidth delay product.

A TCP sender can send up to X bytes in one or more packets but then it has to wait for an acknowledgement from the receiver before moving on.

Have a look at the following link

http://www.psc.edu/networking/projects/tcptune/

and RFC 1323

http://www.ietf.org/rfc/rfc1323.txt

When multiple parallel transfer happen they compete for available bandwidth but they are able to use more of it, because when one session is waiting for an ACK from other side other sessions can send packets within their own window

Hope to help

Giuseppe

[vaishalin]

Hi

Thanks for the information.

I will read docs and if any queries will let you know.

Vaishali

vaishalin,

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