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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Where are my TIME_WAITs on Mac OS X?

No TIME_WAITs on Mac OS X Normally, when a TCP connection is closed, the socket on the side where close() is called first is left in the TIME_WAIT state. When one of the peers is a Mac OS X (Lion) ...
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A small puzzle about routing

This is a followup to this question I saw on SuperUser, to which no answer has been provided. A user deleted the second route in his routing table, # ip route show default via 192.168.73.1 dev ...
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1answer
195 views

ssh tunneling lmgrd port what I've missed?

I've got 2 machines: one local , one flexserver I'd like to do a ssh connection for forwarding the TCP port of the flexserver. On the flexserver, lmutil lmstat -c 5280@localhost is working fine So I ...
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1answer
424 views

How do I open specific ports on Linux (an AWS instance of RHEL v. 7)?

I'm using RedHat version 7. My AWS instances are in a security group with ample permissions for inbound connectivity. I can do Yum updates. The servers can ping each other. I can transfer files ...
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1answer
43 views

Windows Server 2008 sending regular TCP DNS requests to Forwarders

Our organization's primary DNS server is a Windows Server 2008 which two Forwarders set. I happened to notice on our firewall that this server is sending out regular TCP requests to the Forwarders in ...
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1answer
183 views

length of Tcp segment exceed MSS

I find a weird behavior in my Linux system, when I curling a web page, the received TCP segments are significant larger THAN the MSS. here is the output of tcpdump: 00:00:00.000000 IP 10.15.71.190....
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1answer
381 views

server is not responding on SYN packets

On the attached tcp dump, the first two SYN packets (#21800 and 21801) came to the server, however SYN ACK was sent for the second SYN. Is that correct behaviour? My understanding is that the client ...
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1answer
287 views

TCP: out of memory - Nginx

I'm running a high traffic site on a nginx server. Last fews days I'm having problems with my VPS locking up (unable to SSH, and nginx seems to be down). When I look in the logs I can see the ...
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1answer
92 views

SNORT only alerting on inbound traffic

I am trying to raise an alert when someone is setting up a connection to PORT 25 (tcp), whatever source or destination. For this i came up with this simple rule: alert tcp any any -> any 25 (msg:"...
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1answer
390 views

TCP Load balancing

I need to implement an architecture that can serve 3 million GPS Devices sending Location Updates/Alerts (every 10 secs) to our system for processing. Features: 1) TCP communication. 1) Long lived ...
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1answer
216 views

High number of TCP RST packets

Whilst looking into some transient network issues, I have noticed what seems to be a high number of RST packets received: Tcp: 40091950 active connections openings 44754733 passive connection ...
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1answer
211 views

TCP RST from telnet/ssh daemons when connecting from openvpn

I have LAN_1 and LAN_2 interconnected with an openvpn tunnel terminated ona pair of SOHO routers running busybox. One of the vpn purpose is to allow clients on both LAN_1 and LAN_2, to administer the ...
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1answer
137 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
334 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
715 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 ...
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1answer
418 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. ...
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1answer
337 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
201 views

What packet to ignore to not have ssh terminated on brief connectivity loss?

It seems like sometimes there are some connectivity problems around the edge of our network to certain other networks, and my ssh sessions with some remote servers, which themselves have no ...
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1answer
571 views

TCP packets larger than 4 KB don't get a reply from Linux

I'm running Linux 3.2.51 in a virtual machine (192.168.33.15). I'm sending Ethernet frames to it. I'm writing custom software trying to emulate a TCP peer, the other peer is Linux running in the ...
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1answer
451 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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1answer
1k views

How to increase nginx connections

I am facing the problem of nginx max connection issues. I am not able to increase max active connections(520) made by nginx. Some time it is using whole writing (516) operation connections. and due to ...
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1answer
250 views

svnserve -d child process spawning and svn connections under netstat

I see many svnserve -d processes running on my CentOS 6 box, one with the PID 400 and PPID 1 and the rest with PPID 400. I take this to mean the first one is started by init scripts (i know it is) ...
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1answer
180 views

Routing config between internet load balancers and backend

Im facing a problem due my lack of experiencie on routing. I need to config the next things (all run on my computer virtualized, if works, i will pass it to hardware) [internet] ---- [DMZR]--/--[...
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1answer
392 views

server dosnt produce syn-ack

I have a small program that take packets from the nfqueue . change the ip.dst to my server dst (and ttl), recalc checksum and return the packet to the nfqueue. The server and the client are linux and ...
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1answer
257 views

Socket(TCPIP) Unstable

I have a setup of a SCPI server in a Win7 PC and have 2 other programs talking to it locally(127.0.0.1) over TCPIP socket 5025 and 5029. This worked well and stable in a fresh PC, but when we moved ...
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1answer
327 views

TCP sender and receiver window issues

I just want to clarify some things. Lets say the receiver advertises a window of 2000 bytes. The sender sends a 1500 bytes and receives an ack from receiver with window size 100. The ack does not ...
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1answer
105 views

Windows XP TCP halts after burst on ZMQ channel

I have a ZMQ application the sends a high rate of data over a TCP connection upon start up. The application runs fine on Windows 7 and Server 2003, but on XP it halts shortly after connection. The app ...
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1answer
463 views

fast opening and closing connection with a specific port

We have a Main application named "Trevor" installed in 2008R2 machine named "TEAMER12" which is slow now. One more application named "TVS" also running in and found there were many connections per ...
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1answer
201 views

Windows 2008 Server ignoring LDAP request

I'm using Windows Server 2008 R2 and Windows NIC teaming. This is an HP server. Firewall disabled. I have 1 application which authenticates via LDAP to AD (TCP 389). (App is located in same VLAN) ...
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1answer
428 views

WSAECONNRESET curiousity

How exactly does the TCP stack on windows determine that the connection has been forcibly closed or reset by peer? I know that TCP on Windows by default tries to retransmit an unacknowledged packet 5 ...
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1answer
86 views

WebServer Performance Issue

Recently we moved to a new hosting infrastructure and our web site, every 30 min or so, comes to a halt and then recovers ... What we noticed by looking at the performance monitor is that while we ...
0
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1answer
575 views

Benchmarking TCP Server

I've written a very basic TCP-Server based on libevent. Now I would like to test the Server. Is there a tool which generates a lot of connections so that I can check how much concurrent connections ...
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1answer
320 views

Detecting TCP/IP connection drop issues in my application

I have a desktop application which talks to a server using TCP/IP. It was working before but now we are running into an issue. The log message on the server shows that the socket is disconnected after ...
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1answer
145 views

What to check when nginx is fast to serve requests once connected, but slow to connect?

There is sometimes a 1-2 second delay when connecting to port 80 (nginx) over the public interface. It occurs 50% of the time. Once connected nginx serves all requests, including fastcgi proxy ...
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1answer
189 views

Computer Networks Question

Consider the effect of using slow start on a line with a 10-msec round-trip time and no congestion. Assume the maximum segment size is 4KB and the threshold is set to 16KB initially in congestion ...
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1answer
190 views

sliding window protocol?

I understand how sliding window protocol makes the network reliable. But how can it control the flow of data?
0
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1answer
151 views

No transmission via IP

I'm using netstat on Win XP to check protocol transmission details for TCP, IP, and ICMP. There is transmission only in TCP. No transmission in ICMP is understandable since it's for errors and I ...
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1answer
542 views

Strange 2Mbps limit for single tcp connection on 24Mbps ADSL2+

I've D-Link DSL-2500U/BRU/D, ADSL mode is "ADSL2+ AnnexM EU-56", configured as bridge and connected to linux (Gentoo) workstation. Line is good enough, I've stable speed 2.09MiB/sec (i.e. about 18-...
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1answer
852 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. http://www....
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1answer
26 views

Is it possible for SYN/ACK to not be immediately proceeded by a SYN in a network trace

I'm writing a simple program to calculate initial RTTs from a network capture I took using Wireshark. To do this I wan't to calculate the difference in time between the SYN and the SYN/ACK. I don't ...
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1answer
386 views

What are the ports needed for L2TP VPN on Mac OS X Server 5.0.15?

I'm configuring a Mac as a server with a VPN service. So, I opened the ports listed as used by VPN in Apple documentation: UDP 500 -> 500 (+ESP and AH) UDP 4500 -> 4500 Any UDP -> 1701 (I got to ...
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1answer
156 views

random server timeout connections

I am searching for a solution for this issue for 2 days now. I have a centos server, and I get random timeout connections error, about 10-20% of the times. yesterday it happened to one of my users, ...
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1answer
66 views

Can TCP be used like UDP by simply not sending ACK?

Assuming both client & server cooperated, could you emulate the functionality of UDP by not sending ACK packets, and not sending retransmissions? Or would most routers somehow bork the process if ...
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1answer
166 views

How to redirect all incoming packets to sniffer in Linux using iptables?

I need to redirect all incoming tcp packets from eth0 to current host (change ip address from 1.1.1.1 to 1.1.1.2) and outgoing tcp packets from sniffer from eth1 to another host(from 2.2.2.2 to 2.2.2....
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1answer
188 views

TCP Server Memory management: #Connections Vs. #Requests

Given that, there is no theoretical limit to number of concurrent TCP connections a Windows 2008 server can handle. Only thing will happen is, with each connection there will be memory consumption in ...
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1answer
2k views

How to enable/disable TCP DELAYED ACK parameter on SUSE linux?

I want to disable TCP DELAYED ACK parameter on SUSE Linux Enterprise Server for some performance tuning operations. I have used sysctl command but it does not list this parameter. also in SUSE ...
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1answer
397 views

iptables NAT Forward 443 Port DNAT,SNAT failing

I'm trying to setup a proxy server that handles http and forwards https to the webserver. Client > Proxy > httpd I added the rules: iptables -t nat -I PREROUTING -i eth1 -p tcp -m tcp --dport ...
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1answer
2k views

How to enable jumbo frame and large TCP on Windows Server 2008

I needed to enable the jumbo frame 9000 in network setting, and I have already done that. I still need to enable large TCP on Windows Server 2008, but how do I do that?
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1answer
612 views

IIS listening 127.0.0.1 instead 0.0.0.0

I configure binding on my IIS 7 server like: ip address: All Unassigned port: 8080 but in netstat -aon command see only 127.0.0.1:8080 instead 0.0.0.0:8080(which I would like) (0.0.0.0:8080 is ...
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1answer
838 views

how to open tcp port in ubuntu

I have a ubuntu server How can i open a port ? I have flushed the iptables and off'ed ufw Provide me steps how to open a tcp port