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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Iperf Tcp Client and Server

I'd really like to know why the bandwith in the client is higher than the server, i can´t find the answer explaining why this happens. Thank you, Tiago Melancia Values of the bandwidth: Client ...
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2answers
42 views

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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40 views

Configure a websocket server in front of HAProxy

I have a small python server script which creates a websocket connection and accepts base64 encoded IP packets (very similar to this). As of now my script decodes the IP packet and sends it out into ...
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1answer
80 views

Access to Proxy Protocol address within HAProxy

I am running HAProxy that is receiving layer 4 proxy protocol from an upstream source. I have a need to create a custom HTTP header with the address contained there. I can't seem to find how I can ...
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1answer
55 views

How to select different backend based on URI when using “mode tcp”

I am using haproxy version 1.6.2 I have enabled http2 using the config below which I need to use "mode tcp". But once I have switched from "mode http" to "mode tcp" I couldn't use acl path_beg to ...
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4answers
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How does Intel AMT (Active Management Technology) not interfere with the TCP/IP host stack?

The Intel dev kit I've been using includes a remote management feature (also see the Ubuntu man page here) which allows remote reboots in case the operating system hangs. It has the capability of ...
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22 views

Not getting TCP Update Window packet after TCP Zero Window begins

Once I get TCP Zero Window during data transmission, I can't send data anymore in that desktop sharing session. Even I stopped the data sending to check if it can resume but no benefit! In my test ...
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1answer
99 views

Difference between net.core.rmem_max and net.ipv4.tcp_rmem

What's the difference between net.core.rmem_max and the third value of net.ipv4.tcp_rmem? Which has the higher priority for tcp connections? For below two examples, what's the max buffer for tcp ...
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2answers
115 views

TCP timeout for established connections in Windows

I have the following situation: Application (Firebird DB client) on a client computer opens a TCP connection to server on port 3050 Application crash on client, application terminated netstat on the ...
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75 views

Windows Telnet Could Not Open Connection On Any Port, Connect Failed

Configuration: Host: Hyper-V Windows 2008 R2 Guest: Windows 2008 R2 No firewall, no antivirus Problem: After 5 or 6 days, the guest cannot make any TCP connection to outside, neither can do to ...
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1answer
53 views

Permissions to ports Alfresco

When I restart Alfresco, it starts... I got the page... But on the logs I got the error: 2015-11-10 09:58:55,282 INFO [management.subsystems.ChildApplicationContextFactory] [localhost-startStop-1] ...
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2answers
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How do I prevent TCP connection freezes over an OpenVPN network?

New details added at the end of this question; it's possible that I'm zeroing in on the cause. I have a UDP OpenVPN-based VPN set up in tap mode (I need tap because I need the VPN to pass multicast ...
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1answer
89 views

Wireshark shows “TCP Dup Ack” on SACK after each regular ACK

I have a TCP session captured via switch port mirroring and tcpdump. When viewing it (in Wireshark), I see the same pattern whenever I send a message; here's an excerpt of the outbound packets (I ...
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1answer
494 views

Slow Upload to IIS Server

I have a Windows 2012 R2 Server running on an Amazon EC2 instance with IIS 8.5. It hosts a web application, and a custom WebDAV server that interacts with the same database as the web application. I ...
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35 views

TCP and UDP ports usually blocked [closed]

Which are TCP and UDP ports most likely to be blocked? I refer especially to the client edge of the network. To start I guess SMTP (25), SIP (5060) for TCP, Traceroute (33434) for UDP.
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1answer
71 views

Server sends ACK in response to SYN causing a reset in TCP request from the client

We are getting 7% reset messages for our TCP layer messages. We have two sets of logs. The first of Wireshark logs shows a good request and response Here the client was replied with sync ...
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1answer
60 views

tcp retransmit via curl and netcat

I'm trying to setup iptables to cause realistic network failures between docker containers. On the server, I run both netcat -lk 1234 and an Erlang cowboy server. On the client I run clients: echo ...
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2answers
258 views

lsof doesn't show the established TCP connection

On my system, if I run the netstat for a port, it returns: $ netstat -nat | grep "60964" tcp 0 0 192.0.0.1:60964 0.0.0.0:* LISTEN tcp 59 0 ...
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4answers
14k views

What is the “in-the-wire” size of a ethernet frame? 1518 or 1542?

According to the table here, it says that MTU = 1500 bytes and that the payload part is 1500 - 42 bytes or 1458 bytes (<- this is actually wrong!). Now on top of that you have to add IPv4 and UDP ...
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2answers
56 views

Run ncat in background

from some time I'm trying to resolve very annoying issue: I need to have simple server which will listen on particular TCP port and throw all information which it recieve to trash. I'm doing it by ...
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2answers
900 views

Big IP orphaned connections

Let me state up-front that I know just enough about networking at this level to be dangerous, so if I say something stupid, please be kind. I am using a Big IP load balancer in front of 3 Apache ...
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1answer
45 views

Why is Apache2 serving as an iperf server?

My Question: Does anybody know why an apache2 server can act as an iperf server? I thought that an apache2 server does only answer HTTP requests. My Situation: I accidentally realized that an apache2 ...
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1answer
3k views

Dropped ACK FIN, ACK RST, RST packets on webserver with iptables

I run a webserver (Apache) on a Debian 7 machine, with iptables on the same machine. iptables rules are generated by the ConfigServer Firewall (CSF) script. The websites hosted there are fine on my ...
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67 views

TCP connections drop off after initial build up

A bizarre problem on a production setup. Scenario 1) A server listens on a particular port. 2) There are potentially thousands of TCP connection requests. 3) About 200-300 TCP connections reach ...
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4answers
965 views

Why is my web server dropping connections with a TCP reset at high load?

I have a small VPS setup with nginx. I want to squeeze as much performance as possible out of it, so I've been experimenting with optimization and load testing. I'm using Blitz.io to do load testing ...
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Can iptables log all type of tcp connection?

Can iptables log tcp Split-Handshake and Simultaneous-Open connections as well as tcp Three Way Handshake? Here is these two kind of tcp connection descriptions. Here I find how to log new tcp ...
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Apache timeouts and TCP retransmission

The documentation for the timeout directive in apache states that: When writing data to the client, the length of time to wait for an acknowledgement of a packet if the send buffer is full. But ...
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2answers
7k views

What is msrpc needed for on a Windows 7 workstation

I just ran an nmap scan against our network, and many Windows 7 machines have several high ports listening with Microsoft Windows RPC. Example: Port Serv Process name 49152, msrpc [wininit.exe] ...
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24 views

Why might a connection stay in TIME_WAIT for hours or even days?

Our environment is ubuntu 12.04 on EC2. I know TIME_WAIT is a good thing, and I know generally it's OK to see connections remain in TIME_WAIT for up to 2 minutes according to all the reading I've ...
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1answer
45 views

On-the-fly decoding HTTP bodies on Linux?

My wish is to monitor HTTP exchanges between my server and a browser. At present time, I use the localhost because I'm developping the app. I installed and used tcpflow and found it quite useful but ...
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35 views

Logging Simultaneous Open Connection Establishment With Iptables

Simultaneous Open Connection Establishment: TCP is also set up to handle the situation where both devices perform an active OPEN instead of one doing a passive OPEN. This may occur if two clients are ...
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2answers
33 views

Can a poor client VPN connection corrupt a database?

We have a small office with one server and one client that connects to the server’s database for the Sage 300 accounting software. The server is also being used as a workstation for the Sage 300 ...
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1answer
81 views

Ubuntu 14.04 TCP established hash table entries

A bit of background I am running two servers under high traffic one with ubuntu 12.04 (linux 3.2.0-69-generic) and one with ubuntu 14.04 (linux 3.13.0-52-generic). I am now trying to secure both. ...
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(Windows Media Encoder) TCP connection randomly fails/succeeds

We have a windows media server running and are pushing a stream using Windows Media Encoder 9 software on the client. Sometimes, it can't connect to the server and sometimes it can. I ran wireshark ...
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5answers
12k views

netstat shows many times deploy.akamaitechnologies.com connected to my server

Many times, after running netstat on my server, I find one of IP addresses belonging to deploy.akamaitechnologies.com connected to my server, do someone has an idea on what is happening on my server ? ...
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33 views

TCP Syn cookies is it always turned on when enabled?

For Linux kernel 2.6.32 if I set net.ipv4.tcp_syncookies = 1 will that be always used or only during a SYN flood attack? I found 2 sources which says the opposite. 1: "There are, however, two ...
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3answers
179 views

Strange limit of 65536 max tcp incoming connections

I have a Linux server with an Erlang application which shows an odd limit of exactly 65536 max tcp incoming connections. The Erlang application is written with the Cowboy framework. I have tuned the ...
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1answer
1k views

why 5 rx queues per NIC

On my office server, the output of cat /proc/interrupts displays one tx queue and 5 rx queues. Is this due to NIC hardware capabilities or can you configure multiple receive ring buffers in linux per ...
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2answers
3k views

Finding short-lived TCP connections owner process

Running tcpdump on local connections to an apache server, I found TCP connections being established and closed immediately every 2 seconds. How do I find which process is responsible for these? ...
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1answer
52 views

Stopping exploits based on Reversing TCP [closed]

One of the most common exploits on msf, reverse tcp by buffer overflow i guess is my concern. Can i, by any means stop of manage my tcp ports to deny giving access to rhosts and become safe from this ...
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1answer
170 views

tcp_tw_reuse and tcp_tw_recycle not working in specific environment

We are running HAProxy to direct mysql traffic from PHP to a set of mysql servers. However, due to an issue with the way the mysql-client sends TCP packets, we get a ton of connections in TIME_WAIT ...
6
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1answer
1k views

Will tcpdump see packets that are being dropped by iptables?

I have a firewall with these simple rules: iptables -A INPUT -p tcp -s 127.0.0.1/32 --dport 6000 -j ACCEPT iptables -A INPUT -p tcp -s 192.168.16.20/32 --dport 6000 -j ACCEPT iptables -A INPUT -p tcp ...
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5answers
6k 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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0answers
86 views

TCP Established connection spike in AWS

We are using AWS ELB in HTTP mode and are observing a spike in TCP established connection on Tomcat server. We have Apache HTTP server with mod_proxy between ELB and Tomcat. Apache and Tomcat run on ...
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0answers
78 views

Network speed between Windows 7 machines sharing over samba/SMB not reaching 10Gb/s

I have two Windows 7 Machines that are connected via 10Gb/s Intel Server Cards on a 10Gb/s Switch an a subnetwork(Physically separate from the larger main domain network). I'm trying to copy files ...
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1answer
65 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
158 views

Can I use HAProxy to load balance telnet connections?

We use HAProxy as load balancer for regular HTTP requests. I see no reference to telnet connections in the HAProxy configuration guide: HAProxy config guide. I was hoping to reuse HAProxy (or spin up ...
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84 views

TCP Out-of-order packets over GRE causing disconnect

I'm experiencing an issue with a small percentage of TCP connections over a GRE tunnel between two servers. The topology is basically Internet <-> GRE Tunnel <-> Backend The GRE tunnel and the ...
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Wireshark RST against TCP Zero Window

During application sharing with Microsoft Lync Client (Mac OS X), TCP ACK with RST flag is sent from my application end to Lync end against TCP Zero Window packets and call gets dropped. Image Link. ...
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2answers
41 views

SMB / CIFS / Samba Connectionless or Not whilst transfering files?

I have been researching this for a bit, but I have been getting conflicting answers, does samba, from my gatherings, SMB runs on ports TCP & UDP 137-139 & 445. But I have no idea therefore ...