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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Common back pressure strategies for services under sustained high load

I'm wondering what are the common backpressure strategies people use for their web services? Imagine your service operates under heavy load, and at some point the load reaches 120% of your capacity. ...
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158 views

TCP Window Scaling Problem over MPLS

After extensive troubleshooting why the TCP speed over an MPLS circuit is slow in one direction, I figured out that by adjusting the TCP window size the situation improved a lot. Maybe you can tell me ...
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166 views

TCP congestion collapse

I am experiencing suboptimal performance on an EC2 instance connecting to an RDS instance. This particular instance was built before VPC's existed, so all the traffic is flowing through a single ...
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274 views

TCP connection stuck in SYN_RECV state despite ACK received

My client and server are both internal machines. tcpdump on both client and server show all three parts of handshake are communicated, however netstat on server shows SYN_RECV, and on client shows ...
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240 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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47 views

Linux - Outgoing connections from process timeout after the process restarts

banging my head against the wall with this one... I have an Ubuntu Linux server, on top of which our own process which holds 40K persistent connections to external services. When the process ...
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361 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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400 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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510 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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528 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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692 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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144 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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252 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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114 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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7k 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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535 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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291 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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935 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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38 views

Why is SQL Server using all ephemeral ports connecting to itself and causing TIME_WAITs?

I've got an AWS server with Windows 2008 R2, SQL Server 2012, and Tomcat 7. When I run netstat -ano the screen is flooded with TIME_WAIT. I posted the output in a Gist. When I run CurrPorts, filter ...
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11 views

How do I cap each individual tcp stream, to a fixed maximum rate?

I've read but not in depth all the various traffic shaping docs and seen the long question on HSFC scheduling Does anyone really understand how HFSC scheduling in Linux/BSD works? looked at the ...
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49 views

TCP High Send-q coupled with FIN_WAIT1 status

I'm having a problem with one of my webservers, which is taking minutes to completely render a web page. I had a look at the TCP connection and noticed that I have a very high value in the send-q ...
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25 views

Split TCP packet - Data layer vs IPv4Layer

What is the different between split TCP packet in the Data layer compare to split the packet in IPv4Layer ?
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98 views

Always keep socat alive

I have a socat running nicely, executing my command when a connection comes in with the arguments provided. However, the issue I am having is that the socket is at EOF and the next time a connection ...
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421 views

Cannot make TCP Connection with OpenVPN Server

Client OpenVPN assigned IP: 10.8.0.2 ↓ TCP on 1194 Internet ↓ Router port-forwards 1194 to server- Public IP 104.162.67.198 ↓ Server LAN IP: 10.8.0.1 I think the above is what I am trying ...
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57 views

delay in ACK packets for ldap abandon request

we have migrated from an openldap server on linux to a DirX on windows 2008. The ldap server und normal serch request behaves as expected. However with some applications (weblogic deployed webapps) ...
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40 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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85 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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48 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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133 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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60 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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321 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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94 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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444 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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276 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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126 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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153 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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184 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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481 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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178 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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185 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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373 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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624 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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121 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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66 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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118 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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634 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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298 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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36 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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256 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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81 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 ...