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Client /server outage

asked 2017-11-06 15:46:14 +0000

tbaror gravatar image

updated 2017-11-06 16:25:39 +0000

sindy gravatar image

Hello ,

I have issue with TCP/IP server that exchange data with clients dcl (xml) format , the issue occurs once a day , sometimes twice , and goes as follows suddenly all clients cannot connect to the server , while on the server itself, the server is still appear to be listening and seems to be operational , but no connection could be done. During normal communication the data exchange finish with RST deliberately to avoid "TCP Time wait" as attached below Normal communication

image description The server run under Windows 2008R2 , we made sure that firewall and base filtering service is off During the Wireshark trace on it , we can see that prior to the indecent several clients announce Zero Window Clients zero Window

Zero Window Session example

, but i don't know if its related , During the incident we can see clearly that's server kind of rejecting connection but we not sure of the source , since as for server logs seems to operate ok, and he exchange data with others same type of servers during the clients outage as seen blows image. Incident Period

Now we are kind of stucked , and hope someone could pin point something I missed trace is shared here Thanks Please advice

trace Sample

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You have said you close all the sessions with an RST. But in the trace I can see a lot of session wich are closed by a normal FIN handshake?

Christian_R gravatar imageChristian_R ( 2017-11-07 04:59:56 +0000 )edit

Hi Christian Thanks for noticing it , you right, on your opinion could it be that server waits for RST and clients for some reason sends FIN can cause that effect ?

tbaror gravatar imagetbaror ( 2017-11-07 08:26:06 +0000 )edit

At the moment I can´t say it. As I need to have a deeper look into the tracefile.

Christian_R gravatar imageChristian_R ( 2017-11-07 11:39:26 +0000 )edit

1 Answer

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answered 2019-08-14 00:34:56 +0000

wbenton gravatar image

Is there a load balancer in front of your server?

It sounds like one load balancer/or server might fail and clients attempt to go to another load balancer/server which they don't have a valid 3-way handshake for.

If you don't have a load balancer, forget I asked.

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Asked: 2017-11-06 15:46:14 +0000

Seen: 618 times

Last updated: Aug 14 '19