If I have two sites from where I connect to a separate server in a remote location. From 1 site I can connect fine, i.e. good response times etc. However from the other site I cannot connect and the application I am connecting to is extremely slow.

My question is, how does one go about finding the exact hop/location where the issue is being caused?

Traceroute from both sites in both directions is showing no packet loss, and same response times however 1 site is still slower in loading on the client side. The client is a GUI which basically sends xmlhttp requests to the server. 1 site is fine and loading times in the client are good - however the other site the loading times are very slow and I get disconnected from the server a lot.

There are 3 seperate ISP's involved here. 1 network is where the server is hosted. 1 client, and the other client (the slow one). Nothing has changed from my side, i.e. I have not configured anything differently and the slowness seems to be completely random. Plus I have no visibility of how the ISP is balancing/routing etc.

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    Honestly, to give you a better answer we'd need more information - what about it is slow, what are traceroutes (in both directions) looking like, etc.? Are you seeing packet loss, latency, what? – Jordan Head Jan 30 '15 at 15:32
  • @JordanHead The client side sends xmlhttp requests to the server. From 1 site this client is running fine and responding quickly. However from another site I have to wait extra long for things to load in the application. In traceroute I see no packet loss, and same response times on both sites. And this is from both directions. So this is why I am confused. – W Khan Jan 30 '15 at 15:36
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    @W Khan, are you going over an ISP (or more than one), or is this all in your network? We don't NEED your topology, but it would help. You could try running continuous pings with increased packet sizes to see if/when you start seeing loss. Does it change at different times of the day (is it fine at night, and slow during the day?) Did this just randomly start, or did you change something in the network/application? spoorlezer isn't wrong that wireshark would be helpful, but its much easier to analyze when you KNOW it is or isn't the network. – Jordan Head Jan 30 '15 at 15:43
  • The application is in 1 network, 1 client is in another network, and the other client which is slow is in another network. So 3 networks are used with 3 separate ISPs. Because my application is running on a remote server and I connect to it remotely through a client. The slowness is completely random, I cant put a pattern on it! And it started randomly. Ah, increase of packet size might help here. Because it may be the case that small packets are fine and the client is sending bigger packets. Thanks – W Khan Jan 30 '15 at 15:59
  • Do you know if those 3 ISP's are set up to load share, or do you choose 1 over the rest and only change over when necessary (when one fails)? In either case, one of your ISP's might be to blame, especially if it's random and nothing has changed. I don't like jumping to immediately blame the ISP without troubleshooting your network first, but I trust you know your application and normal behavior in the environment - but 3 ISP's is a lot of "What ifs". – Jordan Head Jan 30 '15 at 16:03

Consider using a tool like Wireshark and plug it into the network on both sites. Be sure to test the front as well as the back of the hop/location when you do so.

That way, you can identify what goes right in one location, and what is different - i.e. goes wrong - on the other site.

The reason I'm telling you to test both sides of the hop/location - especially in the 'wrong' part of your networktown ( 1. traffic going to first route point and 2. traffic going beyond route point) - is because the issue may be further down the line than your first hop. You should be able to isolate the issue simply by following the river. :)

  • Thank you. I shall try this out. I would upvote but i need a minimum of 15 reputation! – W Khan Jan 30 '15 at 10:38

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