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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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
274 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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73 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
114 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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2answers
114 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
142 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
291 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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131 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
153 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
44 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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56 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
221 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
141 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
2k 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
95 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 ...
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1answer
190 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
268 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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192 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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201 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
739 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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107 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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0answers
328 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 ...
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1answer
1k 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
645 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
60 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 ...
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48 views

Windows Server 2008 consuming a lot of bandwidth

My Windows Server 2008 has been consuming A LOT of bandwidth in the last days (990 GB). This is a development server so it should not consume more than 100mb aprox. We noticed this after the server ...
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2answers
59 views

Can't block spammy IP

I'm being attacked by 37.59.4.76. It's sending me a great amount of data, which is destroying my dataplan. I've added the iptables Chain num pkts bytes target prot opt in out ...
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2answers
126 views

TCP/UDP Small Package Size optimization [closed]

I currently have the problem, that when a LOT of RTP streams (>800) go to one server the max. speed is onlynabout 70-80 Mbit (on a Gigabit LAN - all Hardware components are Gigabit components) 130 ...
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1answer
151 views

POST of MTU + ~798 bytes gets lost

I have a very weird issue with certain packets not arriving on the destination host. It happens when we transmit a POST that is somewhat larger than the MTU. We can reproduce it with this script: ...
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1answer
324 views

Relationship between tcp state TIME_WAIT & HTTP keep-alive

What is the relationship between keep-alive on a HTTP request and a tcp socket in TIME_WAIT - should they be correlated? Furthermore, should system and web server settings be aligned e.g. ...
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47 views

Source ip based Anycast-BGP?

I'm just getting interested in networking so don't be too harsh on me :) Ideal: 2 servers with shared ip; ip X Client 1 pings ip X > always server A Client 2 pings ip X > always server B ...
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1answer
54 views

Geo distributed ip [duplicate]

When i ping 8.8.8.8 from my home computer (europe) i get around 26 ms latency. When i ping 8.8.8.8 from a server(US) i get around 1 ms latency. When i ping my (US) server from home (europe) i have 130 ...
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259 views

HAProxy RTMP (TCP) load balancing

I am using HAProxy as load balancer for the RTMP protocol. For now it's working very very good but I have one small problem. I want to send the client's IP on the RTMP request after the load balancer. ...
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359 views

How to trace dropped TCP connections?

Trying to help someone with a situation where TCP connections get mysteriously dropped after a few minutes for no apparent reason (this happens even with non idle connections). Both client and server ...
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63 views

apache bench handshake failure server sending TCP FIN

I am trying to verify handshake performance by sending number of requests with out setting concurrency with below command. ab -k -n 18750 -c 1 -Z AES128-SHA -f TLS1.3 ...
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4answers
2k views

Cannot work out what is using port 8080

In Windows Server 2003 R2 64 Bit SP2 I have an app which will only use port 8080 but something is already using it. I would be happy to just kill whatever is using it but I can't work out what it is. ...
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1answer
279 views

Existing TCP Relay Solutions [closed]

I have a scenario which requires the use of a TCP Relay. Before I set out to write something custom, I wanted to see if anyone knows of existing software that can do this for me. I have 2 devices on ...
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1answer
52 views

TCP ports duplication [closed]

I need to communicate server1 to server2. Server1 should have to fetch some records from Server2 when we execute program.exe will make server1 to fetch server2 When I gave netstat -an | find ...
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2answers
736 views

Wireshark “length” column - what does it include?

Can anyone tell me what the "Length" column in WireShark refers to? I'm pretty sure it's the "size" of the entire frame on the wire. I did some calculations, but I didn't get the number that ...
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3answers
2k views

HTTP not finishing over LAN. Hardware cause?

On a customer server running Apache 2.2 on Windows server 2012 we're noticing that from time to time, some requests to the server never finish. Using wireshark I've found a bunch of duplicate ACKs get ...
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71 views

Cannot connect to TCP service from remote host

I have two servers running RHEL 5.8. SRV1 (10.58.192.36) has a service running on port 9002 and I need to connect to this service from SRV2 (10.58.192.42). [root@SRV1 ~]# netstat -anp | grep 9002 tcp ...
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167 views

TCP [RST,ACK] ignored

I have a Windows 2008 server and an application that connects over Internet to it. From time to time I see that I receive a TCP [RST, ACK] that is ignored by my application. Using TCPViewer I still ...
2
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1answer
214 views

iptables: match only the first packet of established TCP-connection

In my Apache-logfiles I find a lot of entries that contain "GET /w00tw00t.at.ISC.SANS.DFind:) HTTP/1.1" 400 or similar crap. They come from non-RFC2616-connections (HTTP/1.1 without hostname). I ...
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115 views

Networking issue in IBM x3650 after install Ubuntu 14.04

I have a problem making TCP connections after a fresh Ubuntu 14.04 installation. First of all, after booting the interface is always off. In my case the interface is manually configured and named em2. ...
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1answer
99 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 ...
14
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1answer
674 views

Under what circumstances is TCP-over-TCP performing significantly worse than TCP alone (2014)?

Many admins keep perpetuating - on ServerFault and elsewhere - how bad of an idea TCP-over-TCP is, e.g. in VPNs. That even the slightest packet loss will make one suffer from at least severe ...
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44 views

Duplicated TCP SYN Messages: second one is ACKed, but the connection is finally FINed

While wring a TCP server program, I found a very interesting symptoms. clients sends a first SYN packet. (server does not show any reactions.) clients sends another SYN packet after one second. ...
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1answer
40 views

Application protocol-based port forwarding/redirection [closed]

I need to split traffic on port 80 between HTTP and non-HTTP, and internally forward HTTP traffic to a port nginx will listen to, and non-HTTP traffic to port 22. Does anyone know of a piece of ...
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2answers
881 views

Send Text String to a Socket In Windows

I have a server that has an open socket that listens for a particular text string on it in order to perform an action. Our linux machines send this data via: echo "text_string" | nc -w 2 ...
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1answer
61 views

FTP upload slows down when devices are connected via hub [closed]

I have a setup with a network hub and three Ethernet devices. One of them is a PC (running windows XP), two others are hardware components that need to communicate with each other over the network. ...