TCP stands for Transmission Control Protocol and is one of the core protocols of the Internet Protocol Suite. TCP complements the Internet Protocol (IP), and therefore the entire suite is commonly referred to as TCP/IP.

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175 views

snmp MIB-TCP::tcp not showing any usage

I am trying to configure MRTG on all of my servers for making a network weathermap, this requires running SNMP which MRTG gets the information from. So, I installed it on two servers the exact same ...
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122 views

TCP Connection Issue Between Linux Machine and VMWare Windows Server

I have a TCP connection issue as follows. The setup: VMWare Virtual Machine: Windows Server 2008 R2 DataCenter SP1, IP: 192.168.2.111, DG: 192.168.2.254 Host Machine: Windows 7 Professional SP1, IP: ...
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300 views

Haproxy using 10GB Memory and 100% CPU with 50k connections

On a Ubuntu 14.04 x64 server, Haproxy uses 3.3 GB of memory and 6.8 GB of swap, while handling 52k connections. The CPU usage also keeps spiking to 100% before most of the traffic was redirected to ...
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220 views

TCP connection timeouts that persist - listener queue backlog?

I have an app running on AIX 6.1 that has a single server process that listens for and polls tcp connections and simply forwards on messages to another process using an IPC message queue. It's been ...
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267 views

No response to some SYN packets when timestamps are enabled

I have a TCP server listening on a machine ("the server") running Ubuntu 12.04.3 (kernel 3.8.0-31-generic). It receives connections from 2 different client machines. Machine A is running Ubuntu ...
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270 views

Should I set rto_min for a route inside data center?

We have a few dedicated server rented in a data center with debian 7, kernel 3.2. We use one of those servers as a database server. The network between our application server and database server is ...
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96 views

Change TCP wait for ACK timeouts in Win7/WinServer

Is there any possibility to change default wait for ACK timeout in TCP network on Windows 7 or Windows Server ? I'm using very slow network ( 1200 bps ) and want to tweak TCP. When using default ...
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368 views

Unix socket connection limit

This may appear like an already discussed/answered question. But I am specifically looking for info which I couldn't find anywhere answered clearly. I have an Nginx + php-fpm setup which uses unix ...
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562 views

mysql client can't read query result?

So I have this machine running an XMPP server which connects to its MySQL database. When I start load-testing it, all goes fine up until after about 500s when I notice: Caused by: ...
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117 views

what can put linux process managing connection pool into bad state, so it restarts them continously?

I have an application with pool of connections to MySQL. At some point, in production, every 1-3 seconds some socket is closed. As a result my app restarts this connection. This is pretty big pool ...
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227 views

Slow Transfer Speeds from KVM host to client

I am trying to isolate the root cause of slow transfer speeds from my host OS to a KVM client. Both are Ubuntu 12.04 LTS Linux. Rsync on the host 192.168.1.72 rsync -auv --progress rut3.img /tmp/ ...
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207 views

ICMP Redirect Theory VS. Application

I'm trying to watch ICMP redirects in a lab using Cisco Packet Tracer (version 5.3.2) and I'm not seeing them, which leads me to believe that either my lab configuration isn't correct or my ...
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109 views

Tcp window size won't go above 130048

I have 2 servers set up with about 80ms latency between them. Both are centos 6 and run a java app that transfers data from on location to another. Both are on 1gbps connections. I have been trying ...
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5k views

ksoftirqd process overloads CPU with high-bandwidth and multiple network connections

I got a 10GBit Server with proxmox 2.1 installed. There's an OpenVZ container running with Ubuntu 10.04 64bit. I can get 200-300MB/sec with wget from data-center internal servers (-O /dev/null) which ...
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457 views

haproxy tcp transparent mode on the same box as service

I'd like to set up transparent HA Proxy for TCP protocol. It works flawlessly when HA Proxy is in front of the boxes that are running the service. But when I try to set up HA Proxy in transparent mode ...
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262 views

A tool to measure overhead of establishing TCP connections

I need a tool which would while doing port forwarding measure how much time was spent establishing TCP connections vs total time passed. Charles debugging proxy has the port forwarding feature and ...
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791 views

In Windows 2008R2 there is a TCP port that is stuck LISTENING but the process that has it open is terminated?

I have a program, NC_net that allows Nagios to monitor Windows machines for various metrics and it seems to have caused a sporadic issue where when the service stops, the TCP port remains open. The ...
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28 views

Why do some outgoing IP traffic not contain UID information?

I am doing egress logging on my server using IPTABLES with the following line which is supposed to provide UID information on all traffic that is logged: -A OUTPUT -j LOG --log-prefix "IPTABLES(O): " ...
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31 views

Why do I get connection timeouts to private services in Azure?

I seem to be seeing this with both my SQL Server, and my MongoDB replica set. I only get a handful a day, but it still concerns me. I am getting a timeout when trying to open a new connection to the ...
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43 views

TCP Window Size Allocation, TCP Window Zero Errors and Network Latency

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 ...
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30 views

periodic connection timeouts to nginx server

We have the following setup: One nginx server as a loadbalancer in front of four worker application servers. The nginx server get about 100 requests per second, sometimes more that that, active ...
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46 views

trying to reach a port forwarded server from the subnet using the public IP not working

I set up a server which is connected to my router. The router forwards a port of my server. So when I scan that port using http://www.t1shopper.com/tools/port-scan/ I got: 188.143.126.14 is ...
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29 views

Multipath tcp application level performance measurement

I am working on a project related to Multipath tcp and I want to measure the goodput and the RTT at the application level. I don't want to use a traditional tool(netperf, iperf, ...) and I want to ...
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252 views

Improving TCP performance over a gigabit network lots of connections and high traffic for storage and streaming services

I have two servers, Both servers hardware Specification are Processor : Dual Processor RAM : over 128 G.B Hard disk : SSD Hard disk Outging Traffic bandwidth : 3 Gbps network cards speed : 10 Gbps ...
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59 views

Network flooded with LLC packet

Recently my network has been slow. From Tcpdump i found lot of frame with protocol LLC. A complete packet capture can been here tcpdump result Any hints on interpreting these packet?
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338 views

What does “connections reset due to unexpected data” in netstat -s mean

I'm running a memcached server under heavy load from multiple web servers. While investigating some odd app level behaviour, we spotted that netstat -s on the memcached box was showing a lot of ...
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191 views

Linux MIPS box: ICMP (ping) works, but TCP does not - how to fix it?

I'm trying to set up MIPS Linux box network. Here is it's configuration: ~ # ifconfig eth0 Link encap:Ethernet HWaddr CC:5D:4E:FF:45:7F inet addr:192.168.0.2 Bcast:192.168.0.255 ...
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75 views

TCP load balance authentication

Impala is a piece of Cloudera software which implements an ODBC driver on a desktop, which then connects directly to a Hadoop cluster. In our implementation, our Hadoop cluster sits behind a DMZ, in ...
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115 views

What could be the cause for outbound TCP/IP traffic beeing blocked while ICMP is still working?

On a Windows Server 2003 there is a strange issue. Every 6 hours the server don't accept outbound TCP/IP traffic while inbound traffic working fine. If the problem occurs I can connect with RDP to ...
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134 views

How can i detect and diagnose local network problems on a multi-server environment?

I'm a software engineer who trying to detect (and solve if possible) weird local networking problems since 2 weeks on multi-server hosting environment. We bought 3 dedicated boxes with 32GB ram 8 ...
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546 views

How to stop NAT dropping idle connections?

I have a TCP connection that can be idle for many hours. The traffic is flowing from the server to the client only. One might say it's kind of push notification. My home router, however, tends to ...
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318 views

TCP connections in FIN-WAIT-2 state on linux not timing out according to tcp_fin_timeout

We run a service with lots of embedded devices in the field, their tcp stack is a bit buggy and sometimes does not close connections properly, resulting in some connections being stuck in FIN-WAIT-2 ...
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115 views

Strange dropped packets coming from port 8888 and with ACK or ACK+PSH set

Background During an incident on a small privative network (1 router/FW + 1 server) my server got accidentally exposed to the internet. Fortunately it was protected by it's own UFW to allow only 1 ...
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53 views

IIS6 poor throughput from higher latency

I've been having a crazy issue with Windows 2003 + II6 where the throughput goes down as the latency goes up. This is exactly the type of thing that TCP Window scaling is supposed to solve so I ...
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137 views

Only ICMP traffic allowed inbound on ISA Server 2006

I have recently set up a connection to a remote site. The connection between the sites is done at the ISP level (ie, this is not a B2B tunnel on ISA). I'm fairly lightweight in the networking realm, ...
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287 views

Can DTrace help find cause for tcp connection reset on Solaris 10 x86?

I'm running performance tests on a web application hosted on a Glassfish cluster. Each cluster instance is hosted on a separate Solaris 10 zone and the http traffic is load balanced between the ...
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498 views

IIS Webserver failing to send a FIN/ACK

I have a Windows Server 2008 R2 SP1 box with IIS 7.5.7600.16385 installed. I have HTTP Keep-Alives switched off. Each time a web-request is made the connection is terminated. I get the following ...
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109 views

Ettercap duplicate traffic

I have a ARM device(Guruplug) and i want it to perform an ARP spoofing attack on the network. This device has 2 ethernet interfaces and 1 Wireless acces point. I want to plug this device in a ...
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64 views

% segments retransmitted above threshold

I've been doing some monitoring on our servers and we get warnings that the TCPv4 / % Segments Retransmitted is above acceptable threshold: http://imgur.com/b8RNm Is there any way to tell what the ...
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113 views

Website latency and bad tcp packets

I have multiple websites hosted on a Linode VPS and I'm having an issue with one of them: every page that I try to load has about 10 seconds latency. Apache logs are clean and the other websites on ...
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545 views

MySQL crashes when connecting from localhost with tcp (UNIX sockets work)

I have Ubuntu 12.04 running MySQL server 5.5.24. I can connect with mysql --user root -p. status shows me : ... Connection: Localhost via UNIX socket ... When I try to connect with mysql --host ...
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244 views

Duplicate syn packets sent from Windows server 2003 sp2

My pc is running Windows server 2003 sp2. Whenever I establish an internet connection (e.g., with internet explorer to google.com), my host sends the syn packet twice. It is (probably not) a ...
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35 views

Is there a utility for Windows that can be used to throttle network traffic/induce dropped packages?

I am attempting to simulate the behavior of my application under less than favourable conditions. Is there a tool that allows me to slow down my network connection by capping bandwidth, introducing ...
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209 views

how to get send-q and receive-q on windows server

in linux, is very easy to troubleshoot a remote connection problem because netstat show the send-q and recv-q. This is very useful because we can know if the remote peer is reading the server send ...
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78 views

Divert TCP connection

I am trying to divert a TCP connection. Given a client (C) which is connected to a router R and two servers (S1 and S2) are connected to the router, C initially connects to S1. I am trying to write an ...
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590 views

Disable kernel processing of TCP packets for raw socket

I'm working on a TCP/IP implementation, for an embedded device, that I want to test from a Linux user space process using raw sockets. raw(7) says that Raw sockets may tap all IP protocols in ...
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374 views

Does TIME_WAIT affect dynamic ports?

I've read a bit about TIME_WAIT connections, and know they should be harmless to my server (connection closed, so no resource connected with this socket). Recently, my server reached the magic ...
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554 views

HAProxy + NodeJS gets stuck on TCP Retransmission

I have a HAProxy + NodeJS + Rails Setup, I use the NodeJS Server for file upload purposes. The problem I'm facing is that if I'm uploading through haproxy to nodejs and a "TCP (Fast) Retransmission" ...
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241 views

Truncated HTML responses with OpenVZ (and nginx)

I'm running nginx in a OpenVZ container on Debian 6 and when proxying I get truncated responses. Most of the time it happens when I proxy another proxy like varnish or apache (for svn servers). I ...
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304 views

LDAP request seems to hang at repeating 125 byte packet, and TCP connection does not close

I've rewritten this question to focus on a specific part. Originally titled "Apache hangs or quits, but keeps TCP sockets open and won't accept connections" Problem Problem is a website (Moodle) ...