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My mind is about to explode as everyone is always blaming the network guys for disconnections and slowness in the networks, but Solarwinds Reports that all utilization in the network devices and links are Okay. So I tried sniffing then I got "Zero Window" errors. So If I may ask:

1.) How is TCP Window Size Allocated? (Is it per TCP conversation like if you have 1 Application(Mozilla Firefox) and 5 tabs open, then the OS allocates Window Size per tab?)

2.) What causes and How do you fix a "TCP Zero - Window" issue? (The Stock Trading Server is the one who is having a hard time processing burst traffic and sending the TCP Zero window messages to the traders but based on the Network Utilization(CPU, Memory and Link Utilization of Network Devices) in Solarwinds and Performance Monitoring(CPU, Disk Space, Memory, NIC Utilization) in both the Stock Trading Server and Database Server, it shows that is Perfectly Normal and even under-utilized!.)

3.) Is it perhaps in the Trading Server's Settings? (32 GB Memory but only uses the default tcp window allocation size of 64 MB)

4.) Or is there something wrong with how slow the Trading Application process the data? (I am planning to increase the TCP Buffer Size from 64KB to probably 256KB but it might not help if the the Trading Application Server itself process the data slowly.)

5.) Also, all the traders are experiencing "Unable to Connect to Trading Server" and "Intermittent Connections" errors. (but there's no report of network problem like "down links" or "fully utilized links". I've even tried to change the polling data to every 1 minute to capture short disconnections but I still see no problem) So I think that there might be a latency problem

6.) How do you measure Latency of Network Communication efficiently? What Free and Paid Software Solutions do you recommend? (Traceroute reports 4ms and even if i increase the ping packet to 1mb, it also shows 1-3ms delay so I don't think that's helpful)

7.) How do you sort out each TCP thread/conversations if the source port and destination port are the same and the data is encrypted? (Like if the Stock Trading Server and the SQL Server talks on the same port numbers but has multiple transactions going on.)

Sorry, I'm just new to the networking world so there are a lot of stuff I don't know and can't find in books and other resources. I think this kind of things are learned through experience so please share your wisdom.

Thank you and Have a Good Day! :)

  • TCP Window Zero errors might indicate a performance issue on either side (not being able to handle too much data, etc), or even broken communications (e.g. TCP ACK are not received, the sending side has to keep a lot of packets in the TCP buffer and it gets full -- why are not the ACKs received on time?). I'm afraid, your question coves too much material for a decent answer that doesn't take 50 pages. – Giovanni Tirloni Sep 8 '14 at 15:57

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