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.

learn more… | top users | synonyms

4
votes
3answers
541 views

How do I diagnose network corruption on an Internet path?

I run a few hosts on network A that make requests to servers (which I don't own) on network B, somewhere across the Internet. Unfortunately, many of these requests get corrupted. If I make the ...
2
votes
2answers
3k views

What is [PSH, ACK] doing during my connection to a global catalog server?

A linux server of mine is trying to establish a LDAPS connection to a global catalog server and the connection is getting dropped (presumably by the GC side). For the purpose of discussion, let's ...
1
vote
1answer
979 views

Windows Server 2008 constantly spamming external IP's on outbound TCP port 445

I have a Windows Server 2008 box running as a Domain Controller. I have noticed in my Cisco ASA firewall logs that this box is continuously sending out (like a thousand requests a second) requests on ...
0
votes
0answers
64 views

FortiBalancer and IE TCP issues

We are using a Fortibalancer for our web servers (Win2012 with IIS) and we have run into a strange issue. IE users will experience timeouts (~77s) in getting a response from our servers. Packet traces ...
1
vote
1answer
413 views

iptables: unknown option “--dport”

When I try to run iptables -A control_in -p tcp --dport 22 -j ACCEPT I get the error message iptables v1.4.20: unknown option "--dport". Everything I've found on the internet and serverfault relating ...
0
votes
2answers
188 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 ...
2
votes
1answer
23 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
vote
1answer
157 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
1k 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 ...
3
votes
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
vote
1answer
613 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
100 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
70 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
993 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 ...
-3
votes
1answer
98 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 ...
0
votes
0answers
44 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
vote
2answers
84 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
773 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
766 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
29k 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
98 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
520 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
512 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 ...
5
votes
2answers
13k 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
621 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
vote
0answers
315 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
717 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.
-1
votes
1answer
70 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 ...
0
votes
0answers
37 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
342 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 ...
2
votes
1answer
4k 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
4k 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
394 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
vote
0answers
85 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?
12
votes
6answers
31k 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
494 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
votes
2answers
123 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
1k 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
232 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
440 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
177 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
460 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
462 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
181 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
226 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
1k 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
votes
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
5k 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 ...
1
vote
0answers
431 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 ...