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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Block all incoming DNS requests EXCEPT from IPs x,y,

I want to block all incoming requests on my two DNS servers APART FROM certain IP addresses e.g. IP of 1.2.3.4 will be allowed to make requests but NOBODY else will. How do you do this with iptables? ...
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Easy way to “edit” the traffic coming from a tcp host (linux)

I need to make some small modification to incoming traffic from a known tcp host:port before the process handling the connection get the stream. For example, let 192.168.1.88 be a remote host which ...
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2answers
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How to check TCP timeout in linux / macos?

I have a network problem on my MacOS that i need to troubleshoot. I know that TCP socket has internal timeout that will close connection if remote party is not responding (but no graceful disconnect ...
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3k views

Load Balancing long running TCP connections

I'm trying to research the best way to load balance long running TCP connections for the following scenario: We have multiple servers behind a redundant set of firewalls and clients establish long ...
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3k views

Allow X Client Display through TCP on Lucid

On Karmic, to allow other PCs to open and X-Window on a station, one had to edit /etc/gdm.conf and change DisallowTCP to false. That file no longer exists on Lucid. I tried changing an entry in ...
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625 views

SYN cookies on internal machines

Our system uses Cassandra running on Ubuntu 10.04 and during last spike in traffic we observed the following message in logs: possible SYN flooding on port 9160. Sending cookies. These machines are ...
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1answer
7k views

How to change receive queue length of a network interface in Linux?

I have a server running Linux (kernel 2.6.18) which is dropping incoming network packets drastically. I thought it is suffering from this because the length of the receive queue of that interface is ...
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272 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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2answers
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FreeBSD Listen Queue Overflows - can't increase max queue size

I have a decently high trafficked FreeBSD Nginx server, and I'm starting to get a large number of listen queue overflows: [root@svr ~]# netstat -sp tcp | fgrep listen 80361931 listen queue overflows ...
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Why Packet Loss AFTER tcpdump has logged the packet?

We encounter some strange packet loss and want to know the reason for this. We have an imageserver and a server for stressing the imageserver. Both are located in the same datacenter First we run a ...
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142 views

TCP packet filter based on TCP sequence

I need to build a test environment with a very precise packet loss based on specific TCP sequence or, optionally, on payload content. I couldn't figure out how to do it with tc or iptables. What tool ...
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Should I use TCP or UDP to run a web server

I have just installed Apache web server on my computer. I have managed to use it locally (I can open index.php from my computer using my web browser). But I would like to make my web site available ...
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Karmic Koala (Ubuntu): enable remote x clients through TCP

It seems every version of Ubuntu has a different way to enable remote connections to the local X server. I'm asking this question, while I do my own research: how can I enable the X server listening ...
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FTP client/server failing on switching to PASV mode

Update The ISP said that they recently added the area where this computer is located to their IPv6 network. Coincidentally, ever since the day they added that area to their IPv6 network, no FTP ...
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1answer
809 views

Does a growing number of TIME_WAIT connections affect server performance?

I have 2 servers, both running RHEL 6, one for Apache 2.2 and one for memcached (memcached-1.4.4-3). I noticed an increase in the number of TIME_WAIT connections on the Apache server netstat -n | ...
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1answer
933 views

How to achieve multiple NFS/TCP connections to the same server?

I'm trying to maximize the NFS/TCP bandwidth between a Linux client and a single NFS server over a 10Gbps link. Although each NFS mount has its own device (major/minor), everything comes down to a ...
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1answer
966 views

option http-server-close on HAProxy haproxy-1.5-dev19 will result in Connection: close header sent in response

I basically have the following issue: whenever I add option http-server-close to the haproxy config (either in frontend or backend section), haproxy will send a Connection: close header in the ...
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4answers
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Rsyslog not logging from remote server

I am trying to set up a centralized log server. I have central server (A) receiving logs via a remote server (B) on port 514. I know it is receiving these. Here are a few entries from a tcpdump on ...
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715 views

Is the TCP checksum over the payload?

I was somehow convinced that the TCP checksum was a header checksum (similar to the IP checksum), but I'm now having doubts reading the Wikipedia article: The checksum field is the 16 bit one's ...
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1answer
340 views

Bad Mumble control channel performance in KVM guest

I'm running a Mumble server (Murmur) on a Debian Wheezy Beta 4 (x86_64) KVM guest which runs on a Debian Wheezy Beta 4 (x86_64) KVM hypervisor. The guest machines are attached to a bridge device on ...
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1answer
141 views

why dstat failed with --tcp option?

why --tcp option failed? should i install some package? if yes, which package i should install? this question is not the same as ...
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3answers
114 views

SMTP server force outbound traffic

I'm having some trouble with setting up a SMTP server on a windows server 2003 machine, while trying to send emails using PHP through the internet, but to domain email addresses. Common info: ...
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105 views

How can I tell when a TCP connection was created on Linux?

How can I figure out at what time a given (as in currently-open) TCP connection was created?
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178 views

Please recommend an affordable cisco product capable of handling up to 100,000 plus simultaneous tcp connections [closed]

I am setting up my server lab, can you please recommend an affordable and very reliable router than can handle over 100,000 simultaneous open tcp connections without breaking a sweat? Thanks!
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windows firewall , some ports not listening

I've added an inbound connection rule for my windows 8 firewall on windows server 2012: I've restarted the Windows Firewall. When I check that port using this program, it says that it is not ...
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223 views

Is an Apache use TCP port on each connection?

Our system admin said "Apache use a TCP port on each connection" so A server can serve 65534 (MAX) simultaneously. is it Right? I think Apache use only 80 or 443. But , he use many file descriptor ...
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Configuring keepalives with TOAD client communication

I have a scenario where long-idle sessions of TOADSoft client communication with the Oracle server seem to be torn down as they timeout on an intermediate state-full firewall. These sessions could ...