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  Asked: Feb 25 2008   6:58 AM GMT
  Asked by: Raghu.krishna

VPN tunnel


Networking services, VPN, VPN Tunnel

Hai all,
i have a client which is using 1Mb leased line conectivity.And VPN tunnel also,The problem he is getting,while he upload some files through tunnelto a remote server which is US/Austrelia he getting high latencey.the point to point conectivity is fine,the TTl from client end to my end iam getting 6milli seconds only.the server which is remote/i ping from my end iam getting latency of 290/300 millii seconds.

can you give solution for this that will be more help full to me.

thanks
ragards,
chaitanya
Network Engineer.

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Last Answered: Feb 27 2008  5:48 AM GMT  by Jlees


Latest Contributors: Mrdenny


If the file is large enough to fill the pipe, or there is enough other trafffic passing across the link, then the latency will go up because the ping has to fight for bandwidth on the line. I've seen this on leased lines from the US to China as well.

Another thing to check is to see how many "hops" the packets go across between the two networks with a tracert (or traceroute depending on your OS) from one side to the other side. (I know you said leased line, but sometimes even leased lines have hops as do Frame Relay circuits)

There is a chance that it's due to a bad port on either router. We had the same kind of problem at our office network and it turned out to be a bad port. The problem is that nothing on the router showed that the port was bad. We had to find the problem do to process of elimination.
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Labnuke99  |   Feb 25 2008  2:24PM GMT

That latency is to be expected also if you are using VPN encryption. That will add overhead to the already high latency due to the distance and buffering between US & Australia. This latency seems to be pretty much within norms as I have sites in Thailand and Singapore and from the US the latency is between 290 & 390msec.

It is possible that you are overloading the link and as previously mentioned that will cause higher latency. You can use a tool like iperf to measure throughput and window sizes to see if some tuning on endpoints could help with throughput.

Are you concerned about the latency issues or throughput? High latency is normal when the endpoints are far apart. Throughput is a function of latency and bandwidth. Adding more bandwidth won’t necessarily solve any issues if latency is still high (as is typical when the endpoints are halfway around the world from each other). Unfortunately the data path has to go around the globe rather than through it.