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We are trying to diagnose a chronic disconnection issue. Overnight, nearly every night, our HTTP long poll client is disconnected from the server. The most likely proximate cause is that the longpoll wasn't received within 35s of the last one.

That proximate cause doesn't help us very much because it doesn't explain why.

Claim: some network device in the path between the clients and the server is dropping or delaying packets.

Question: How would we go about finding evidence for or against this claim?

The clients are on the West Coast of North America and the server is in the East so there's a fair bit that might fail. I'm not sure how to decide if this failure is in the network or not.

The server is Centos. The clients are Ubuntu and Windows.

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Wow, thats a hell of a long way. I presume this is just over a 'internet' connection rather than a private circuit. Run a traceroute or tracepath and post the results here. Do you go through one AS (ISP) or Multiple AS's (ISP's). Can you move your Boxes so they are connected by the same AS (same ISP). Could you rent a private circuit (mpls or other) between the two boxes. Could you make your software tollerant to adverse network conditions. Do you have any device performing NAT between the two boxs (think nat timeouts). Use a continious ping betweem the two boxes for 24 hours,. –  The Unix Janitor Sep 14 '12 at 16:48
    
For continious pings, check out MTR. It combines ping and traceroute in a single program. –  Hennes Sep 14 '12 at 17:00
    
There is a private link between the sites. My concern is that the problem may be more generic. The clients will eventually go on customer sites where we can't necessarily pull the same tricks. –  Sarge Sep 14 '12 at 17:39

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