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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set MTU using ifconfig but UDP message is not affected

I have set in my code the following /sbin/ifconfig eth0 192.168.4.12 mtu 1464 in my suse Linux i686and try to create a simple application for sending a simple binary, alternating the Transport ...
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10 views

Keep doing TCP Retransmission with ACK, PSH

here is my situation: I got two servers, a loadbalancer (prowered by softlayer) and a web server running apache 2.2 and php 5.4. My web application only serve android mobile device. I was tested 2 set ...
6
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1answer
541 views

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 ...
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2answers
12 views

Distributed LAMP vs DB and Web Server same box

We have a very read heavy semantic web (RDF) application which is RHEL 5/Apache 2.2.3/Tomcat 6/Java 6 on one Server, and MySQL 5.1 on another. Apache and MySQL are backported Red Hat repo stuff, so ...
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1answer
37 views

Low throughput on Debian + nginx/apache

On the same LAN/WAN I have a Windows server 2012 server running IIS 7.5 and a Debian (wheezy) server running Nginx 1.4.5. Both servers are connected to the same LAN/WAN. When I download a 10mb file ...
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1answer
654 views

Memory Pressure Protection Feature for TCP Stack - Provided by Microsoft Security Update KB967723

We've been having a lot of funky issues with some of our web based applications that allow clients to submit lot of image files to our servers. Lots of ports are used in the process. ...
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9 views

Reproduce netperf TCP_RR test with NTttcp

The documentation of NTttcp being hard to find and to understand, how can I mimic the behavior of the TCP_RR netperf test with NTttcp?
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1answer
72 views

Linux tool to show connections/s?

Is there a tool/command to show connections per sec? I've tried a few iptraf and iftop but I can't see anything about connection rates.
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1answer
32 views

TCP timestamps field is in the future

I have a server sending TCP packets. I noticed, with wireshark, that my packets in the Timestamp optional field look like Timestamps: TSval 2552765291, TSecr 3858527953 The TSval is the value my ...
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28 views

iperf test in reverse direction gives different result

I used iperf to measure the max throughput for TCP connection between two ubuntu machines. Both the machines were directly connected be means of a 1Gbps cable. When I performed iperf tests i obtained ...
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1answer
34 views

Support of batch mode in tcpkill

I fire tcpkill with destination ip. Example tcpkill host 10.0.2.184 The problem I am facing is that, tcpkill doesn't come out after killing all tcp connection. After killing all tcp connection it ...
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1answer
54 views

Show real TCP/IP addresses behind Nginx environment

When i execute the command netstat -atun | awk '{print $5}' | cut -d: -f1 | sed -e '/^$/d' |sort | uniq -c | sort -n I see high number of connection assigned to server ip I want to see the real ...
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1answer
34 views

Open file count keeps increasing forever

I'm experiencing issues with the number of files opened increasing over time. If I run my server for about few hours, it'll no more accept any connections. The limit was 1024. I've increased the limit ...
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1answer
43 views

Windows Server 2008 TCP connections limit

I run my own game server made in .net 4.5 on a Windows Web Server 2008 VPS. I have done some research on a problem I have. My app doesn't accept clients, if there are already 1000 clients connected. ...
3
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0answers
60 views

TCP packet being retransmitted 7 times when sysctl tcp_retries1 is set to 3 - why?

Ubuntu 12.04 I am trying to better understand how many times TCP will attempt to retransmit a packet when it does not receive confirmation the destination received it. After reading the tcp man page ...
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0answers
25 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 ...
2
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3answers
66 views

Windows Server TCP sockets random disconnect: how to reproduce?

We rented 10 Windows servers from a large provider in Europe. They all work as expected. One server suddenly crashed and customer care found that both disks were broken. They replaced disks and also ...
3
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3answers
1k views

Need help troubleshooting intermittant TCP timeout in HAProxy

I have an application where the client connects to a server via a simple TCP based protocol over TLS/SSL. In development, this has worked great for many months while we were building our application ...
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0answers
33 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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6answers
353 views

How can I find the total number of TCP connections for a given port and period of time by IP?

On a Linux system there are plenty of methods for listing the current TCP connections for a given port by connecting IP but: how can I count the total number of connections to a port per source IP for ...
4
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2answers
178 views

VMXNET3 performance on Linux on ESX 5.0

What kind of performance can I expect from VMXNET3 adapter when running two Linux guests on the same VMware ESX private network defined between those guests? I use VMXNET3 adapter for communicating ...
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0answers
27 views

How can I replay a TCP stream to my client

I need to do some validation testing of a new feed handler I have made. I have some pcap data that I captured from the production network and I would like to have my development feed handler connect ...
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4answers
8k views

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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3answers
2k 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 ...
5
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1answer
2k views

apache webserver unresponsible with server-status showing all child processes waiting for connection

My setup: i have 3 nearly identical webserver machines serving the same high loaded dynamic website with simple load balancing over dns. The service has been working for over two ears with the same ...
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1answer
49 views

TCP echo server security [closed]

I am setting up a Linux server similar to a TCP echo server and am wondering about security issues I should be concerned about. This will be a bare bones Centos/KDE server with no additional files ...
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1answer
47 views

What is the incentive to operate a TCP/IP node? [closed]

I mean, why does anybody relay messages to other nodes? Why are these eleven good people below helping me send my bytes to their destination? traceroute to stackoverflow.com (198.252.206.140), ...
3
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1answer
30 views

Default TCP connection backlog value in Windows

Which is the default connection backlog value for TCP in Windows? I have tried to find it but no luck. Cheers
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1answer
98 views

Port scanning from localhost

I see lot of tcp connections on different ports on my server with 'TIME_WAIT' status. Just simple port scan, but i cant see ip address of this bastard because connections is going from my nginx. Can ...
3
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3answers
356 views

How can private IPV4 addresses get past iptables NAT (tcp RST,FIN)

I've got a router performing simple NAT translation using iptables iptables -t nat -o -j MASQUERADE This works fine almost all of the time except for one particular case where some TCP RST and FIN ...
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1answer
106 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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0answers
24 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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2answers
41 views

How to drop bogus tcp packets through iptables?

We are seeing the issue described here - http://archives.neohapsis.com/archives/bugtraq/2002-10/0266.html In brief, we need to drop bogus packets, such as with SYN+FIN flags set. I can drop this ...
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0answers
26 views

opensips sever running fine and UDP connection cannot register but TCP connections works fine

Im a newbie to opensips and Centos/Linux. Recently installed opensips sever which running smoothly on TCP connections, but users cannot register on UDP connections. here my Log, have a look. Feb 26 ...
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1answer
60 views

pushing apache2 past 1500 concurrent connections

I am trying to scale to 4000 concurrent connections on a ubuntu/apache box. It is 8 core / 64gb ram, so it is not hitting memory or cpu, or any resources for that matter. The problem is with ...
0
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1answer
25 views

How to view tcp connection errors in apache/ubuntu

I am load testing a ubuntu/apache2 server and after 500 concurrent connections my load testing software is telling me there are connection errors. The errors are not showing up in apache error log. ...
5
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1answer
67 views

Odd TCP termination sequence

While troubleshooting another thing, I've noticed an odd pattern of TCP closes. Packets: http://www.cloudshark.org/captures/7590ec4e6bef What's happening is that the last few packets of the close ...
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1answer
87 views

TCP and retransmission [closed]

I'm trying to understand how the transmission and ACK work in TCP. In this Figuure, when A retransmitt the seq 100 after he recive three duplikated ACK , B will answer with 121 ACK or 158 ACK ?
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1answer
69 views

Linux unfriendly IIS/ASP.NET :-) : Quick download on windows but slow on linux [closed]

This particular web site (gops.tay.be) serves objects quick if I try to request the page using windows, but I get them very slow if trying using linux. There is no difference if I use browser or curl: ...
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2answers
109 views

Why does TCP Reno cut the congestion window in half when I get duplicate ACKs?

I'm having a hard time understanding this conceptually. Why does TCP Reno cut its congestion window in half when it detects triple duplicate ACKs and cuts its window to 1 segment when it times out? ...
2
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1answer
25 views

TCP Reno Window Size drops to 0

I'm working on a task on comparing TCP Tahoe and Reno. Tahoe drops the window size to 0 every time it detects packet loss, that is clear. However, when I plot my window size for Reno, it does fast ...
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2answers
114 views

Parallel TCP sessions for fixed destination and source ports

As I understand, TCP takes a chunk of data and cuts it into segments that are transmitted over a TCP session. Now suppose that I, as a client, have two chunks A, B of data that I want sent to a ...
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0answers
80 views

Why would a client send a RST packet as reply to a SYN,ACK?

I have a HTTP webservice where sometimes the connection setup fails in a strange way: client sends a SYN packet server sends a SYN,ACK reply client responds with RST In which situations could a ...
0
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1answer
126 views

Effects of IW10 (initcwnd 10 initrwnd 10) on high speed LAN based TCP/IP communications?

What does changing the number of packets sent during the initial congestion window to 10 have on LAN connections? Via: ip route change default via GATEWAY dev INTERFACE initcwnd 10 initrwnd 10 Is ...
2
votes
1answer
56 views

Find number of TCP bytes transmitted

I have rhel4 and rhel6 hosts. I can use netstat -s to see information on the number of segments sent/received. I can use ifconfig to see the number of bytes sent/received on a given interface (for ...
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0answers
41 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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1answer
105 views

Is it fine to turn off tcp window scaling and tcp timestamps on server?

Our application is running on Amazon server and we were continuously facing the issue related to tcp handshaking. Sometimes we were not able to connect to our application or telnet on port 80 of our ...
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1answer
49 views

How do I know that my TCP connection is safe from the Firewalls/NAT?

Being on the Azure cloud, I found that the firewalls there drop connections between the Web server and the database quite often. Mostly when there was some inactivity, I think something between 5 and ...
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1answer
89 views

TCP Duplicate Acks are received

We are trying to get to maximum throughput on ftp over an LTE link. When we are downloading a file using ftp some duplicate ACKs are seen. Reading about the duplicate ACKs, I gather they are sent so ...
2
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1answer
375 views

How to capture retransmitted packet info with tcpdump?

TCP retransmission rate on a host are often a good indicator of network problems. How do I find out the source and destination IPs for the packets that are being retransmitted? For context, on hosts ...