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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TCP packet loss against SQL-server

Where I work, we have had some issues with connections to the database. We get a lot of failures which appear as "recv failed" on the client side. I have used Wireshark to try to debug the problem and ...
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9 views

Reverse proxy encrypted java traffic on non-standard TCP ports on Windows Server 2012 R2

I'm trying to find a software that will run on Windows Server 2012 R2 that can reverse proxy TCP traffic without caring about the layer 5-7 details. By reverse proxy, I mean the software needs to ...
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19 views

RHEL6.4 server did not send a SYN/ACK packet in response to a SYN packet from AppDirector intermittent

In my case, client access this RHEL6.4 server thought AppDirector, so the TCP connection is from AppDirector to the server. According to wireshark, sometimes, RHEL server didn't respond for the first ...
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1answer
27 views

PHP-FPM TCP connections not terminating in time

I'm serving Wordpress pages via nginx/PHP5-FPM using APC caching (through the W3 Total Cache plugin). Nginx communicates with PHP-FPM via TCP sockets on port 9000. I've adjusted the number of max ...
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41 views

Bad ping results while testing 6000 TCP clients with 18 mbytes/s total traffic on Windows Web Server 2008

The clients are running on the machine #1. The server is installed on the machine #2. The machines have a gigabit connection through a switch on their private vlan. There are no errors in the switch ...
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2answers
46 views

Get a website's host machine's OS/server software without access to the server

Is there a good methodology to find the operating system and server software that is being used on a served website that you don't have SSH access to? What I'm doing right now is looking at TCP/IP ...
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1answer
41 views

TCP Upload Speeds Slow to the Internet over LFN

I've got two Linux VMs separated by a 50 mbps WAN connection. There is about 70ms of RTT on this WAN link, so it's got some latency. I've been testing my upload throughput to the Internet from each of ...
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1answer
49 views

Hitting Ephemeral TCP Port Exhaustion

We run a high traffic website. Over the past few days, we've had several customers complain of sporadic downtime that we cannot reproduce. We have several web servers elected to receive traffic from ...
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1answer
11 views

Is it possible to bind a socket with NIC Queue?

when i open a new socket linex system automatically bind it to a NIC queu. Currently i have two sockets and i want to bind them to two different NIC queues. My question is 1)Is it possible to bind ...
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9 views

Ghost tcp connections: ss sees them, nothing else does

We have a strange problem. Our remote server shows over 900 connections coming from our office over port 80: # ss -n | grep ESTAB | grep $OFFICEIP | grep :80 | wc -l 935 Netstat shows a similar ...
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1answer
41 views

Strange entry in open file list on Ubuntu server

On my Ubuntu server I occasionally run the following command to view any open files that are TCP connections from my server: lsof -uroot | grep 104.236.XX.XXX The last time I ran it, I saw this as ...
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35 views

No SYN/ACK answer from server

At first I describe my LAN organization. I have 2 Networks (scheme http://take.ms/s3CSy): 192.168.0.0 / 255.255.255.0, router ASUS RT-N65U with internal IP 192.168.0.1, static external IP without ...
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1answer
16 views

What does the tcp_fastretrans_alert error mean?

I found this error a couple of times in /var/log/messages after experiencing some odd TCP behavior: For some reason, if I connect to for example SSH for the first time in say an hour, the connection ...
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51 views

How many concurrent TCP connections are supported in Windows Server OSs?

I am distributing software in the form of a Windows service that can be installed, and am currently trying to ascertain the specifications for supported operating systems. The service communicates ...
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32 views

Unable to connect to remote MySQL from VPS

I am trying to establish a remote MySQL connection from one VPS to another. I have tried and done everything, I have allowed the outgoing TCP port (3306) in csf.conf, I have used Iptable rules online ...
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2answers
47 views

how to force linux to accept packet with loopback ip

i have an embedded system with an Ethernet interface that needs to accept external packets with IP of 127.x.x.xx. is there a way to force Linux to accept external packets with this loop back address ...
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19 views

What happens when 2 hosts simultaneous establish a connection in a 3-way handshake [migrated]

Say two hosts A and B, both attempt to start a connection with each other but the SYN from A gets to B first before B's SYN arrives at A. What happens? My answer is that A would sent SYN ACK and ...
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29 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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4 views

nfs mount works for tcp but not over udp [migrated]

I'm connecting my raspberry pi (raspbmc) with my synology nas. I have 2 mounts 192.168.0.5:/volume1/video /mnt/video nfs udp,intr,noatime,rsize=32768,wsize=32768,nolock,nfsvers=3,async ...
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4answers
211 views

Simulate slow connection between two ubuntu server machines

I want to simulate the following scenario: given that I have 4 ubuntu server machines A,B,C and D. I want to reduce the network bandwidth by 20% between machine A and machine C and 10% between A and ...
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2answers
61 views

TCP - TAP performance

Linux. Is there a performance loss from using a tap device vs a hardware one like eth0 ? The goal is to create a user space tcp/ip stack and avoid the kernel as much as possible. I would like to be ...
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2answers
196 views

Implementing TCP Sticky Sessions With HAProxy to Handle SSL Pass-through Traffic

How can we implement session stickiness in HAProxy when SSL must terminate on the backend servers? We need the stickiness because backends cannot share sessions. This is my original configuration: # ...
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1answer
34 views

Proxy-attack simulation

I have a WS2008 x64 server, that has NodeJS application working on its 80 port. Server constantly receives queries from different IP-addresses that are trying to use my application as a proxy. NodeJS ...
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0answers
90 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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115 views

WSAECONNREFUSED SAP Gui unable to connect on SAP server on hp ux - inetd.conf file reference

I have a sap server installed on HP-UX vm, up and running. when I try to connect to the server from SAP client GUI installed on windows machine I get the following error --------------------------- ...
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2answers
242 views

How is a TCP request routed from a virtual machine to an outside resource and back again?

Scenario: Computer A has a local ip of 192.168.1.100, which is running a VM inside of it. The VM now makes a tcp request to an external IP address (74.125.225.98). Could someone explain how the ...
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25 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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1answer
72 views

Is ARP Connection oriented or connectionless?

Is ARP Connection oriented or connectionless? It uses TCP, but does that consider it connection oriented?
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43 views

Display IP & TCP statistics per interface (netstat -s with interface)

Linux has the ability to display protocol statistics with netstat -s. The output looks something like: Excerpt: 7487 times unabled to send RST due to no memory TCPDSACKIgnoredOld: 817 ...
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1answer
83 views

Limit Number of TCP connections in Linux Server, to avoid attack

I want to limit the number of TCP connections in Linux server, I have used the following command. iptables -A INPUT -p tcp --syn --dport 80 -m connlimit --connlimit-above 25 --connlimit-mask 32 ...
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1answer
65 views

What is the best way to measure latency via a “telnet to port” test, preferably with built-in Linux tools?

I'm writing a Graphite/Diamond collector measuring network latency. Specifically it should measure the time it takes to open up a connection to a port on a remote server. And it needs to work via ...
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21 views

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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1answer
64 views

Tuning Linux TCP for large number of TIME_WAIT

It looks like we have a bunch of tcp connections hanging around on a busy webserver, this is the output from ss -s: Total: 366 (kernel 1037) TCP: 72108 (estab 130, closed 71964, orphaned 0, synrecv ...
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1answer
23 views

Solaris 11 / OpenSolaris - stop processes from listening?

I would like to write a script to secure Solaris 11 servers in preparation for internet access. In addition to enabling ipfilter, I would like to disable network-accessible services that are not ...
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28 views

Dropped TCP Packets over two-stage IKEv2 VPNs

Something of a weird setup this: There are two Virtual Private Clouds (10.100.240.0/20 = prod1 and 10.101.0.0/24 = control), which have a valid router between them. Control hosts a VPN that is meant ...
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5answers
82 views

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 ...
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1answer
92 views

NTttcp shows slower throughput on loopback (127.0.0.1) than on network

I am using NTttcp to find a baseline for what throughput I can expect between a client and server on windows. When I ran the client and server on two different machines on our LAN I got the following ...
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1answer
49 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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2answers
854 views

TCP Dump, cannot understand these 4 lines?

I need support understanding these 4 lines. looks like tcp dump but im actully not understanding what exactly is happening here. 13:13:22.407445 IP 192.168.246.128.54955 > 192.168.246.13.80: S ...
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1answer
63 views

How does an IP address goes down from an Application Layer to IP Layer? [closed]

Using the classical TCP/IP layers model, I am thinking about an application (for example a browser) acting as a client wanting to talk with a server (e.g. a web server). Of course it has to use the ...
2
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1answer
97 views

TCP piggybacking introduced by a man-in-the-middle network node beween the client and server?

When wireshark trace taken on the client side it appears to be: ---SYN---> <-SYN-ACK- ---ACK---> -HTTPGET-> But when wireshark trace taken for the same traffic on the server side it ...
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4answers
214 views

Is there a netstat -s equivalent for windows?

I know that netstat -s exists on Windows, but it displays way less informations than on Linux/OS X. It only gives 8 counters about TCP, while on Linux it's more than 50. I'm looking for any ...
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101 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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0answers
64 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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2answers
139 views

Proxying TCP by hostname

I've got multiple game servers TCP ports on my single host machine. The goal is to have users be able to connect to server1.domain.net and have their directed based on that subdomain. My first ...
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61 views

TCP ignores some packets for no reason

I have a weird problem which I can't understand. The actual network configuration is quite complex, because I am using Openstack and Docker to build a virtual network. However, the problem is not ...
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186 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 ...
32
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1answer
949 views

Random TCP RST's on certain websites, what's going on?

Short version: One Windows Server 2012 machine on my network is getting persistent but intermittent TCP RSTs when connecting to certain websites. Dunno where they're coming from. Check out the ...
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2answers
145 views

Recommended TCP keepalive settings for a busy server

We are having some network timeout issues on a Debian server that is quite busy, and maintains multiple connections to a number of other servers on the network. Here are our current TCP keepalive ...
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2answers
35 views

Clients phone provider claiming high latency over UDP, how do I test?

A client of our uses a hosted phone solution for his 50 agent call centre. They use a hosted dialer who make the out going calls, once the connection is made the call is passed to my clients user ...