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Questions tagged [tcp]

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.

TCP is just one communications protocol on the web. Others include:

  • User Datagram Protocol (UDP)
  • Internet Control Message Protocol (ICMP)
  • Hypertext Transfer Protocol (HTTP)
  • Post Office Protocol (POP3)
  • File Transfer Protocol (FTP)
  • Internet Message Access Protocol (IMAP)

TCP on Wikipedia

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What are possible downsides to setting a (very) large initcwnd for high-bandwidth connections?

I have been experimenting with the TCP parameters in Linux (with a 3.5 kernel). Basically concerning this connection: Server: Gigabit uplink in datacenter, actual bandwidth (due to sharing uplinks) is around 70 MB/s when tested from another…
Tomas
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tcptrack shows SYN_SENT connections, does that mean the SYN package reached the server?

our server suffered a serious connection timeout problem, so we track tcp connection with tcptrack we found out that, if the client started to connect to the server, tcptrack shows the connection, but in SYN_SENT status, and netstat -nat shows…
xpu
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How does TCP Ping or Traceroute Work?

How does the tcp ping or traceroute work? Does it take in account just the time it takes to establis the TCP handshake? Also in ICMP ping you can specify the packet size, can this be achieved in TCP ping?
GeorgeU
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How to tune TCP for high-frequency connections between two nodes

I've been scratching my head for the past few days, trying to come up with a solution for the following problem: In our data center we have a F5 running on BigIP hardware that acts as a single ingress point for HTTPS requests from client machines in…
Christoph
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Can Squid be used as "TLS termination proxy" to encrypt TCP connections using client certificates?

Abstract I need an encrypted TCP connection from multiple clients to a single port over the internet. Can this be realized with Squid? Concrete situation We use a monitoring and client management solution in our company which is accessible over…
marsh-wiggle
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Nginx log to syslog on TCP port

I need to redirect Nginx access and error logs to a remote syslog server. From http://nginx.org/en/docs/syslog.html I saw that I can do: error_log syslog:server=192.168.1.1; However I need to redirect to a specific TCP (not UDP!) port and I tried…
int 2Eh
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Get number of TCP established connections

On a Linux server one can use netstat -tan | grep ESTABLISHED| wc -l but this will not work on a high load server with watch -n1. Such approach works fine if the server is not very busy or the monitoring interval is big enough. But what can be…
Vinicius Tinti
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Excessive 'TCP Dup ACK' & 'TCP Fast Retransmission' causing issues on network. What's causing this?

I'm getting excessive TCP Dup ACK and TCP Fast Retransmission on our network when I transfer files over the MetroEthernet link. The two sites are connected by one sonicwall router, so the sites are only one hop away. Here is a screenshot from…
Ingram
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Netstat -s showing (and growing) "packets pruned from receive queue" and "packets collapsed in receive queue"

we are seeing the following: [root@primary data]# netstat -s | grep buffer ; sleep 10 ; netstat -s | grep buffer 20560 packets pruned from receive queue because of socket buffer overrun 997586 packets collapsed in receive queue due to low…
anonymous-one
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Varnish running out of open ports, lots of SYN_SENT connections

Recently we've been experiencing issues with our Varnish (3x) -> Apache (3x) setup, resulting in a huge spike in SYN_SENT connections. The spike itself is due to the amount of new traffic hitting the site (not a DDOS of any kind), and it seems like…
user150997
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is TCP port exhaustion real?

How fast would one need to allocate ephemeral ports in order to get into the TCP port exhaustion condition? I was told there are ~4k (older Windows), ~16k (newer Windows) or ~28k (RH Linux) ports available for the client requests. Now, is the pool…
Andriy Volkov
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HTTP, TCP, UDP and connectionless

I am a bit confused with HTTP lately. Some facts are that TCP can operate connection orientated or connectionless, this I understand. TCP though is connection-oriented while UDP is connectionless which is used when the message itself can fit…
What'sTheStoryWishBone
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How do I check how many connections are open currently on a specific TCP port?

I'm doing some comet benchmarks and would like to see how many open connections I have. Actually I use netstat: netstat -ant | grep 8080 | grep EST | wc -l But it needs around 4-6 minutes to list the number, is there any tool that can do show it…
Nenad
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In TCP/IP terms, how does a download speed limiter in an office work?

Assume an office of people, they want to limit HTTP downloads to a max of 40% bandwidth of their internet connection speed so that it doesn't block other traffic. We say "it's not supported in your firewall", and they say the inevitable line "we…
TessellatingHeckler
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How can I take advantage of IW10 in kernel 2.6.33?

I've read that 2.6.33+ allows setting custom cwnd. if the IW is 10 by default (for all distros? only some?) how does one view what the current IW is on a particular compiled…
John Bachir
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