For techies - Network analyzer assist

by daystar 1 Replies latest jw friends

  • daystar

    1. Client uses web-based product that requires persistent connection to remotely hosted appservers.
    2. Client loses connection intermittently.
    3. Packet Analyzer log generated while issue occured.

    Now, I don't have a whole lot of experience using packet analyzers, but I'm not an idiot at least. The only thing I see that might be causing such a thing are some TCP zerowindows and subsequent TCP zerowindowprobes in the logs they've sent. (Yes, I've filtered it down to just the relevant IPs for host and dest.)

    From what I can tell, this may indicate a lower TCP buffer setting somewhere near their end.

    Thoughts? (BTW, this is not the only place I'm posting this. I know that only a few people here would be of my target audience type.)

    Oh, and HEY!! I haven't been around here in a bit. Good to see people still breathe here!

  • Little Drummer Boy
    Little Drummer Boy

    Hi Daystar!

    Nice to see you back!

    Client loses connection intermittently

    For all I know you have already tried or thought of this stuff, but I don't know if you have only a software background or if you have experience dealing with physical stuff, so I'll post this anyway.

    Some questions first:

    Is all net connectivity affected for the client? Or, is it just to that remote server? What is the client OS? Also, is it related to any specific time of the day? Just having the ceiling lights kick on in some offices can cause enough line noise to disrupt a network.

    Since you said the problem is intermitent, the first thing that jumps to my mind is a Layer 1 issue. Do diagnostics on the client NIC, patch cables, cross-connect ports, and switch ports (at both sites if possible). Should be easy enough to start with things like a temporary NIC swap. Hell, just a twitchy patch cable can cause all sorts of crap on a network. A blown out NIC can chatter away and cause grief. If you can, swap to another switch port client side and see if that helps. If it won't disrupt the network unduely, reboot the Access Layer switch

    BTW, what brand and types of network gear are they running on the client side? Do they have a time based ACL on a router that could be interfering?

    Some things to try anyway.

    Hope I haven't somehow wasted your time with this, and good luck!


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