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I'm connecting from my office to two servers (server 'A' and server 'B') hosted by two different providers.

Since a few days, my connection speed to server 'A' has dramaticaly slowed down. Even when opening a shell through SSH, a two pages directory listing can take 10 seconds. Using Wireshark, I can see a lot of [TCP Spurious Retransmission], [TCP Retransmission], [TCP Dup Ack], etc...

However my connection to server 'B' still works perfectly fine, and when I open a shell from server 'B' to server 'A' I'm not experiencing any latency. So I believe that the problem is due to an equipement on the route between the gateway of my office and server 'A'.

Is there any way to determine which equipment could be the cause of the problem?

Olivier Leneveu
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  • Can you ping server A from your office, and what do the responses look like? – Mintra Dec 22 '15 at 15:52
  • Pinging does not show any anomaly: `Réponse de 212.47.xxx.xxx : octets=32 temps=19 ms TTL=53`. – Olivier Leneveu Dec 22 '15 at 16:17
  • If you ping continuously (`ping -t` on windows) you get all the packets back, none dropped, with consistent round-trip times? – Mintra Dec 22 '15 at 16:26
  • Sorry, my previous answer was a bit short. I did run a ping -t for about 1/2 hour this morning without noting any anomaly. The latency was constant, around 20ms. – Olivier Leneveu Dec 22 '15 at 16:29
  • Is there a VPN or firewall in between the systems? – Gmck Dec 22 '15 at 16:55
  • I think if you don't have access to routers or firewall between your PC and server A, you probably won't figure out what's causing the problem. You can use iperf (`iperf -s` on server `iperf -c` on client in case you are running Linux) to check throughput end-to-end though and show the result to our ISP for SLA comformance. – Alexey Smirnov Dec 22 '15 at 17:04

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