Bandwidth affected by latency

We have a VPN tunnel to another company and use it to move large files (20-100M). We are only able to achieve ~250kByte transfer speeds. The ping-time is ~250ms. We are using a 9M partial DS3 with a PIX 525 and the receive site has 100M burst capability (unsure as to the equipment on the rx end).

Yes, I have tried adjusting the RWIN during testing. No, the application is not able to create multiple send threads/streams. Is there a calculation to verify the transfer speed and factor the latency? What else could we look into to try and improve the tunnel speed?

Reply to
Frank
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In article , Frank wrote: ;We have a VPN tunnel to another company and use it to move large files ;(20-100M). We are only able to achieve ~250kByte transfer speeds. The ;ping-time is ~250ms. We are using a 9M partial DS3 with a PIX 525 and the ;receive site has 100M burst capability (unsure as to the equipment on the rx ;end).

:Yes, I have tried adjusting the RWIN during testing. No, the application is :not able to create multiple send threads/streams. Is there a calculation to :verify the transfer speed and factor the latency? What else could we look :into to try and improve the tunnel speed?

I suggest you try ttcp, or better yet, netperf

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Reply to
Walter Roberson

Frank,

Do you have any packet drops or maybe even high cpu utilization on your routers? Packet drops not counted as various types of frame errors (CRC, etc.) are mostly caused by overfilled queues.

Please post 'show int' outputs of two interfaces that are making one of your VPN connections with poor performances...

B.R. Igor

Reply to
Igor Mamuzic

I'm a novice in this area but for 250KBps (about 2Mbps) with a 250ms RTT is consistent with 64KB buffer sizes. To fill 9Mbps with a 250ms RTT you need to get your buffers up to about 280KB - 256KB might be OK. See Brian Tierney's TCP tuning pages at for an explanation.

Sam

Reply to
Sam Wilson

Google "long fat networks" for more info high bandwidth, high latency networks.

Scott

Reply to
thrill5

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