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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2answers
169 views

Debugging slow transfer rate from server [duplicate]

I'm trying to explain this as simple but documented as possible. This is not exclusive to this server or my current ISP. I've seen the same exact issue over the years while being with different ISPs ...
4
votes
0answers
515 views

Haproxy using 10GB Memory and 100% CPU with 50k connections

On a Ubuntu 14.04 x64 server, Haproxy uses 3.3 GB of memory and 6.8 GB of swap, while handling 52k connections. The CPU usage also keeps spiking to 100% before most of the traffic was redirected to ...
2
votes
1answer
22 views

Why some tcp_[rw]?mem$ voodoo show all equal values?

Looking at TCP optimization guides across the Internet, a common theme is setting the tcp_mem, tcp_rmem, or tcp_wmem three-integer vector to have equal values in the sysctl.conf file. Borrowing from ...
1
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1answer
128 views

How to Add/Remove New Server behind Haproxy with Minimal Disruption

Haproxy is currently balancing the load between 2 servers, A an B. Clients are connecting to these servers via persistent TCP connections. Question: We want to upgrade from server A to a more ...
3
votes
1answer
928 views

is it possible to synchronize the states of TCP proxies in real time (for real-high-availability of SLB)?

Consider that there are two server load balancers working in the tcp proxy mode (e.g., for L7 load balancing). Is it possible to synchronize their states in real time so that they can be a backup for ...
34
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3answers
4k views

Windows TCP Window Scaling Hitting plateau too early

Scenario: We have a number of Windows clients regularly uploading large files (FTP/SVN/HTTP PUT/SCP) to Linux servers that are ~100-160ms away. We have 1Gbit/s synchronous bandwidth at the office and ...
2
votes
2answers
6k views

All connections from this network get stuck in SYN_RECV state, connections from my home or phone properly get ESTABLISHED

My server (a linode VPS) suddenly started to timeout on every request yesterday. I'm pretty inexperienced in networking and would love to learn a process for debugging these connectivity issues. ...
3
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2answers
2k views

is TCP port exhaustion real? [closed]

How fast would one need to allocate ephemeral ports in order to get into the TCP port exhaustion condition? I was told there are ~4k (older Windows), ~16k (newer Windows) or ~28k (RH Linux) ports ...
1
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1answer
508 views

Does hole punching require a UDP rendezvous server Or could it be a TCP one?

I'm trying to get my head wrap around this issue... I would like to connect two users... Those users are already connected to a TCP server, which is aware of both public ip and connection TCP port. ...
0
votes
2answers
96 views

Strange data in HTTP request

I have a HTTP server that serve many short time connections from many clients, the server logged that there are some invalid HTTP requests, so I decide to capture the network traffic. This is what I ...
0
votes
1answer
62 views

Prevent TCP Connections from Timing out on Restarting Service

On Ubuntu 14.04, an app communicates with clients at intervals of about 1 per sec to 1 per min. However the service have to be restarted regularly and this causes all the connections to drop/timeout. ...
3
votes
1answer
785 views

Linux - TCP Source Port Reuse (and delay)

We have an application making a lot of calls to a remote web server/service. Client app is JBoss/Java on Linux (Red Hat 5), remote server is Windows 2008. There is a Cisco ACE in the way but there ...
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votes
1answer
90 views

How can my server announce its presence to everyone in the network [closed]

The situation is as follows. I want to have an application running on a server. All of the desktops in the company has to connect to it. But I do not want the IP address of the server to be hard coded ...
1
vote
0answers
45 views

Multipath tcp application level performance measurement

I am working on a project related to Multipath tcp and I want to measure the goodput and the RTT at the application level. I don't want to use a traditional tool(netperf, iperf, ...) and I want to ...
0
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0answers
40 views

OWPING communicating between tcp and tcp6

I am trying to deploy the perfSonar toolkit on my network. I'm testing the one-way ping tool on a local subnet, which contains the monitoring station (in this case, a laptop) and a host ( a cubox-i ...
1
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2answers
68 views

Incoming tcp SYNs possibilities

This might be a general TCP question. Can I receive TCP SYN packet on an established connection OR a connection in TIME_WAIT state? Is is possible?
2
votes
1answer
651 views

How to force use of tcp instead of udp for rpcbind?

I'm trying to use tcp/111 for rpcbind under Debian Wheezy instead of udp/111. The portmap in Squeeze uses tcp/111 without any special configuration, but Wheezy fails. Even numerous sites (as well as ...
8
votes
5answers
707 views

dump tcp connections without tcpdump

On a centos box, I like to dump tcp connections - I would like to see if a server tries to send requests to a certain IP. Usually tcpdump would do the trick - but tcpdump is not installed, and ...
10
votes
3answers
27k views

What does LAST_ACK mean, as a State value in netstat?

If a Windows server has several thousand ports open in LAST_ACK state (as shown by netstat), what could this mean? Is it because one endpoint is waiting for the other to respond?
0
votes
1answer
79 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 ...
2
votes
1answer
406 views

Cisco ASA 5510 Out-of-Order Packets to Google

We're seeing a large number of packets being dropped due to being Out-of-Order. The numbers are large enough that it may be having an impact on network performance. We've isolated it down to a few ...
1
vote
1answer
365 views

How to configure SSH client timeout after network failure?

Let's say I connect from a client to a server via SSH, and in the middle of the session I pull the server's network cable. On the client, the ssh connection stays alive for around 15 minutes before ...
2
votes
2answers
10k views

How to troubleshoot connectivity when curl gets an *empty response*

I want to know how to proceed in troubleshooting why a curl request to a webserver doesn't work. I'm not looking for help that would be dependent upon my environment, I just want to know how to ...
3
votes
2answers
584 views

When a server IP changes, do exising TCP (e.g. http/mysql) connections remain running

We have some PHP-FPM servers and when they need a database connection, they connect to an HAProxy server which selects them a database server to use and the connection opens. When we then want to ...
1
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0answers
277 views

Improving TCP performance over a gigabit network lots of connections and high traffic for storage and streaming services

I have two servers, Both servers hardware Specification are Processor : Dual Processor RAM : over 128 G.B Hard disk : SSD Hard disk Outging Traffic bandwidth : 3 Gbps network cards speed : 10 Gbps ...
0
votes
1answer
460 views

How to send 0x80 byte to a tcp port using netcat or similar tool?

I'm trying to make a Memcached server respond as if I where using binary protocol. If possible just command line answers pls, no code spinet in any programming language.
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votes
1answer
60 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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0answers
32 views

Security concerns regarding php://stdin

I'm using xinet.d and php://stdin to host a raw tcp-connnection, (following the excellent guide at http://gonzalo123.com/2010/05/23/building-network-services-with-php-and-xinetd/) I'm concerned with ...
0
votes
1answer
236 views

How to measure TCP connection time in Linux

I want to measure the overhead in creating a TCP connection. I know of many tools like hping and netperf, but they seem oriented at measuring latency. I want to know how long the 3-way handshake ...
1
vote
1answer
3k 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 ...
1
vote
2answers
3k views

Wireshark TCP Window Size Value

I am debugging an application with Wireshark and watching the TCP Window Size value shrink on one side of the communication. If the packet's TCP section shows a "Window size value: 1", does that mean ...
-1
votes
3answers
312 views

What happen when I assign 2 IP on one NIC? [closed]

What happen when I assign 2 IP on one NIC? e.g. I have one physical NIC (eth0) and I assign on this interface 2 IPs from different network. e.g. auto eth0 iface eth0 inet static address ...
0
votes
1answer
1k views

Connecting To FMS Server Issues

I am trying to get my computer to connect to an Adobe Connect server but I have had no luck. The error that Adobe is telling me is "ERROR: FMS Server did not return correctly!" and have done some ...
1
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0answers
72 views

Network flooded with LLC packet

Recently my network has been slow. From Tcpdump i found lot of frame with protocol LLC. A complete packet capture can been here tcpdump result Any hints on interpreting these packet?
11
votes
6answers
27k views

Finding cause of TCP retransmission within a LAN

Hello denizens of Server Fault I have an irritating problem with a LAN of about 100 computers, 2 Windows domain servers, and 12 VoIP phones. Since their installation around a year ago, every week or ...
-1
votes
2answers
403 views

block all packets in windows 7 (so nothing appears in wireshark)? Can anything locally installed do it?

is it possible to block all packets in windows 7, so that nothing appears in wireshark? I have tried choosing Block all for incoming. for outgoing, I see it has no block all option, just a block ...
0
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2answers
111 views

TCP Python Server

I have a question regarding connection reliability running a tcp server from an ec2 instance. We are currently serving mobile customers around the world from the Oregon region using a c3.4xl ec2 ...
0
votes
1answer
781 views

TCP Sequence & Acknowledgment numbers

I have looked through other questions on here involving the relevant topics, but I am still not clear on this. I have just been reading this explanation of TCP sequence & acknowledgment numbers. ...
0
votes
2answers
204 views

apache2 keepalive and opening a tcp connection

An IP packet contains a payload, such as HTTP information, which in turn contains html information. An IP packet is encapsulated into a TCP segment, which detects problems in transmission over ...
7
votes
2answers
405 views

What are possible downsides to setting a (very) large initcwnd for high-bandwidth connections?

I have been experimenting with the TCP parameters in Linux (with a 3.5 kernel). Basically concerning this connection: Server: Gigabit uplink in datacenter, actual bandwidth (due to sharing uplinks) ...
1
vote
3answers
172 views

Is TCP header the same as TCP segment?

So, is a TCP header actually the same thing as a TCP segment? I was reading this page, where it reads near the end that: Even though it might seem they are, in most cases, when referring to the ...
-1
votes
1answer
360 views

Connect to sphinx on remote server

I recently moved sphinx onto the same server as our db so our architecture is: File Server that hosts our web app DB server w/ Sphinx instance (searchd) When I try to connect to sphinx at ...
2
votes
1answer
400 views

TCP Window size increases drastically and sender don't send until the receive buffer is not empty

I have a download stream over TCP in an application (running on Win2k12). The problem is that the connection gets closed by the sender because it times out. I used wireshark to see what happens on ...
1
vote
1answer
160 views

Increase number of connections per socket

How do I increase the number of connections each socket can accept? I know that you can increase the total number of connections using: # sysctl kern.ipc.somaxconn=4096 But each connection is then ...
0
votes
2answers
179 views

FreeBSD Established Connections Maxing out at 300

We've previously had issues in our environment where it seemed we were reaching FreeBSDs max connection limit. We took action demonstrated by http://nginx.org/en/docs/freebsd_tuning.html and bumped up ...
0
votes
1answer
852 views

TCP Zero windows size and full windows size

The problem that we are facing is that some of the http connection have response time > 60s (about 5%). I discover that the problem should between the web server and loadbalancer. Here is my finding, ...
0
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0answers
19 views

Debian as TCP-Server for Serial Port redirecting [duplicate]

I want to start a tcp listener on debian. One client should be able to connect and should get inputs of serial port in the tcp connection. And when the client sends data through the tcp socket the ...
5
votes
1answer
4k views

Too many TCP connections causes disconnections

I have a game server which runs with TCP connections. Server disconnects users randomly. I think its related with TCP settings of server. In local development environment written code can handle ...
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0answers
403 views

What does “connections reset due to unexpected data” in netstat -s mean

I'm running a memcached server under heavy load from multiple web servers. While investigating some odd app level behaviour, we spotted that netstat -s on the memcached box was showing a lot of ...
2
votes
0answers
276 views

TCP connection timeouts that persist - listener queue backlog?

I have an app running on AIX 6.1 that has a single server process that listens for and polls tcp connections and simply forwards on messages to another process using an IPC message queue. It's been ...