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

1
vote
2answers
2k views

Deactivate SYN flooding mechanism

I am running a server that is running a service on port 59380. There are more than 1000 machines out there connecting to that service. Once I need to restart the service all those machines are ...
2
votes
2answers
2k views

Traceroute, ICMP, UDP and TCP

When does traceroute use TCP? Or does it just use UDP, also why does Traceroute use UDP on MacX and ICMP on windows? I thought ICMP just contains a message saying what caused the error of a packet and ...
0
votes
1answer
988 views

What is typical TCP ACK response time in a good network? [closed]

What is typical TCP ACK response time in a good network? One would think it is in microseconds. We have a situation that is going over 200 milliseconds.
1
vote
1answer
91 views

MongoDB cloneCollection between Azure hosted CentOS servers times out at 2 hours

I'm trying to clone a MongoDB collection from CentOS server A to CentOS server B. Both are running 2.4.6. The copy works great until exaxctly 2 hours, at which point I get a 9001 socket exception: ...
13
votes
4answers
3k views

What is the “slash” after the IP?

In Amazon EC2, where I set "security groups", It says: Source: 0.0.0.0/0 And then it gives an example of: 192.168.2.0/24 What is "/24"? I know what port and IP is.
1
vote
2answers
75 views

How to map an ephemeral port to a pid?

I have a RHEL server with several apps on it and I am attempting to figure out which one of them is making calls to an external web service. I have TCP dumps that show the calls being made and through ...
0
votes
0answers
172 views

SSH attempt keeps failing, syn+ack does not reach machine

1 0.000000 10.0.0.1 10.1.1.0 TCP 66 49285 > ssh [SYN] Seq=0 Win=8192 Len=0 MSS=1260 WS=256 SACK_PERM=1 2 0.001160 10.1.1.0 10.0.0.1 TCP 66 ssh > 49285 [SYN, ACK] Seq=0 ...
2
votes
1answer
609 views

How to achieve multiple NFS/TCP connections to the same server?

I'm trying to maximize the NFS/TCP bandwidth between a Linux client and a single NFS server over a 10Gbps link. Although each NFS mount has its own device (major/minor), everything comes down to a ...
3
votes
3answers
837 views

How do high traffic sites service more than 65535 TCP connections?

If there is a limit on the number of ports one machine can have and a socket can only bind to an unused port number, how do servers experiencing extremely high amounts (more than the max port number) ...
1
vote
2answers
701 views

NAT Gateway - Maximum connection limit

I know just enough networking to be dangerous. The nitty gritty low level details of NAT are not something I am particularly knowledgeable about. I accidentally found myself in a discussion earlier ...
1
vote
0answers
276 views

TCP connections in FIN-WAIT-2 state on linux not timing out according to tcp_fin_timeout

We run a service with lots of embedded devices in the field, their tcp stack is a bit buggy and sometimes does not close connections properly, resulting in some connections being stuck in FIN-WAIT-2 ...
0
votes
1answer
56 views

No ssh connection to vServer possible; numtcpsock value is 1,024

my virtual server is used as a mailserver (with Zimbra 7.2.0_GA_2669) and webserver. Yesterday the Zimbra web interface was not accessible anymore, though all services were running. Since two hours, ...
0
votes
3answers
123 views

Tunneling ports through different routes without the knowing of the local programs

I need to set up the following scheme: server1: Generic program connects locally to proxy, which then connects to proxy to server2. Everything is ok, until the connection between the servers. ...
0
votes
0answers
70 views

Can I use IPtables to access/mangle the contents of a TCP “optional header field”?

Can IPtables stuff data into and recover data from the TCP Optional Header Field area? I'd like to have one server add some "tags" to a packet, and another server see those tags and take action on ...
0
votes
0answers
14 views

Display number of bytes transferred over a port

how can i display the number of bytes transferred over a certain tcp port? I know there are several tools (iptop,iptables...) which can monitor this, but what i need is an absolute counter. I poked ...
8
votes
1answer
3k views

Unexpectedly shrunk window

I run a major media upload/download site and I noticed these: Is this serious or background noise due to the big file sizes and is there any tweaks I can add to /etc/sysctl.conf to improve and ...
3
votes
1answer
98 views

three-way handshake & sequence number

Looking at the image below, taken from the book of Ilya Grigorik - High Performance Browser Networking, I can understand that the SYN packet picks a random sequence number which is incremented in SYN ...
1
vote
1answer
202 views

Reasons for a TCP Timeout scenario

I am actually currently investigating long running connections of a Java/Tomcat based Web application. After ruling out any internal or application based reasons, I am now down to the network layer. ...
1
vote
1answer
333 views

How to reset a tcp connection immediately on both ends on a certain condition using linux netfilter/iptables?

Dear Serverfault community, I have the following problem: I need to reset (disconnect) tcp connections on both network sides immediately if a certain string is encountered in the packet data. I don't ...
0
votes
0answers
323 views

Window Size goes to zero

We are seeing an issue with our web servers where a client is doing a HTTP POST and sending xml files. We are seeing weird behavior where we are sometimes only receiving part of the data. (Sometimes ...
3
votes
3answers
1k views

How to enable TCP for DNS resolution?

I've been doing some reading about this, according to what I understood this is possible, but HOW??, I know UDP is much much better for DNS resolution but because of so many issues an restrictions, ...
1
vote
2answers
7k views

tcptrack shows SYN_SENT connections, does that mean the SYN package reached the server?

our server suffered a serious connection timeout problem, so we track tcp connection with tcptrack we found out that, if the client started to connect to the server, tcptrack shows the connection, ...
1
vote
3answers
655 views

Solaris tcp_keepalive_abort_interval

There is a section in Solaris reference manual for tcp_keepalive_abort_interval. However, it doesn't appear in ndd /dev/tcp \? listing. # uname -srvmpi SunOS 5.10 Generic_142909-17 sun4us sparc ...
0
votes
0answers
200 views

Too many TCP TIME_WAIT on PHP FCGI PORT

There are way too many TIME_WAIT on 127.0.0.1 This is causing PHP FCGI to work way too slow and hence my error log is full of "recv() failed (110: Connection timed out) while reading response header ...
28
votes
8answers
235k views

What does “TTL expired in transit” mean on a ping attempt?

We get the message “TTL expired in transit” when we try to ping to a server in a different network segment. When we run tracert, 4 ip addresses repeat themselves indefinitely: 14 60 ms 59 ms ...
0
votes
0answers
172 views

Unable to open TCP socket to xinetd proxy service

I have nagios check that checks service over HTTP but I constantly get there message: HTTP CRITICAL - Unable to open TCP socket I have jetty server that runs on port 7777 and I use xinetd to ...
3
votes
0answers
161 views

snmp MIB-TCP::tcp not showing any usage

I am trying to configure MRTG on all of my servers for making a network weathermap, this requires running SNMP which MRTG gets the information from. So, I installed it on two servers the exact same ...
0
votes
0answers
30 views

Catching parent application PID/name for outgoing TCP connection

I need to find the PID or application name which establishes outgoing TCP connection on remote PC. The connection is briefly closed, so I can't react to it in real time. Edit: OS is Win7 iirc.
-1
votes
1answer
92 views

Is their an official tool to tweak Windows 2008 server TCP configurations?

We are running scripts that initiates numerous TCP connections and disconnects right away. It's just to test if the remote report is opened and responsive. But we are having random strange issues ...
0
votes
0answers
259 views

Blocking a TCP Syn Attack

I have recently experienced a TCP Syn attack and since it was from a software like LOIC, it kept happening until I banned the IP Addresses or stopped my system from making output to them. Here is what ...
23
votes
5answers
2k views

Can TCP and UDP packets be split into pieces?

Can TCP packets arrive to receiver by pieces? For example, if I send 20 bytes using TCP protocol, can I be 100% sure that I will receive exactly 20 bytes at once, not 10 bytes then another 10 bytes ...
-3
votes
4answers
22k views

How do I check how many HTTP connections are open currently? [closed]

I want to know how many people are connected to my server. Since I'm doing comet applications, this is important
1
vote
2answers
992 views

SYN Cookies on a LAN server - Ok / advisable to disable?

We are looking at tuning our linux tcp stack on one of our lan boxes. We were wondering if it is ok / advisable to disable SYN cookies on a server that doesnt have any sort of external (eg: ...
0
votes
1answer
2k views

Linux bridge (brctl) dosnt forward IP packet when router is one of the bridge endpoints

I have setup a brctl bridge on Ubuntu with the following deployment: Cisco router -> Linux bridge -> client computer The bridge forward the following packets types: ARP,STP, but doesn't ...
0
votes
2answers
504 views

Test a server using MTR through TCP

Is it possible to use MTR over TCP? If not is there an alternative? I have done some research and I am not finding any way to do such a thing, so I'm wondering if anyone has had any experience with ...
0
votes
2answers
200 views

Unable to POST/Upload files to a PHP page

I have a weird problem when I try to post contents or upload files by php to my server. After submitting the form it sleeps for a while then shows a page loading error. I tried different contents and ...
21
votes
5answers
27k views

What is the best way to transfer a single large file over a high-speed, high-latency WAN link?

This looks related to this one, but it's somewhat different. There is this WAN link between two company sites, and we need to transfer a single very large file (Oracle dump, ~160 GB). We've got full ...
0
votes
0answers
39 views

Apache process 100% with IPV4 TCP 10u

Today i got strange http ussage. All apache processes woks ok but after some time i found few processes stocked at 100% and they are like that long time. After i checked that process id at webmin ...
-2
votes
1answer
159 views

VMware - Host two VPS with same IP

I have: 1 Dedicated server, Windows server 2008. 2 Virtual machines inside the server. (VMware, Windows too) 1 example IP address: (0.0.0.1) 1 example IP address: (0.0.0.2) I need: 1 Dedicated ...
0
votes
0answers
47 views

Linux + OpenVPN + SNAT + Failure on client grab the reply to it's own generated traffic

Ok, I'm really desesperate I need to release an openvpn deploy to get rid of a dying server. On the subject: I installed OpenVPN with a routed interface (tun0) into a server with a public IP + 3 ...
1
vote
1answer
72 views

Fixed TCP payload Size [closed]

I have an aplication that need to have a fixed (516 byes) payload size in the TCP packet. The application itself can't be modified to adjust it settings, therefore i need to tune the TCP Buffer Size ...
4
votes
5answers
1k views

Forwarding Windows log event using TCP

I'm looking for a way to safely centralize all my Windows and Linux logs on one location. Since I'm in a mixed environment, with both Linux and Windows, I started using Syslog-ng on the Linux boxes ...
1
vote
0answers
102 views

Strange dropped packets coming from port 8888 and with ACK or ACK+PSH set

Background During an incident on a small privative network (1 router/FW + 1 server) my server got accidentally exposed to the internet. Fortunately it was protected by it's own UFW to allow only 1 ...
2
votes
1answer
821 views

Adding more than one IP to sip.conf tcpbindaddr and udpbindaddr (Asterisk 1.8)

The defaults in the sample sip.conf under Asterisk1.8 contain udpbindaddr=0.0.0.0 and tcpbindaddr=0.0.0.0. I want to bind the incoming [foo] extension to udp:192.168.1.1/255.255.255.0, the outgoing ...
3
votes
3answers
568 views

python reports socket in use, netstat and others claim its not

We have a strange socket issue with a RHES3 box: Python 2.4.1 (#1, Jul 5 2005, 19:17:11) [GCC 3.2.3 20030502 (Red Hat Linux 3.2.3-52)] Type "help", "copyright", "credits" or "license" for more ...
4
votes
2answers
3k views

lots of packets pruned and packets collapsed because of socket buffer low/overrun

i've set up a test machine (debian squeeze 2.6.32 on a linode 2048 machine) that interact with an api that returns large chunks of json. It calls the API 3000/minutes asynchronously, the api is ...
0
votes
1answer
22 views

Information about SYN [closed]

I'm new to socket programming and i read that SYN packet can be created through a raw socket .But windows api doesn't allow the creation of a raw socket .I know that ICMP packet doesn't have any port ...
2
votes
1answer
420 views

How to edit TCP window size from iptables?

There is TCPMSS target to edit MSS value of connections (including forwarded). How to edit window size (for example, cap to some maximum value) by iptables rule? Expecting something like iptables ...
3
votes
3answers
1k views

How to prevent TCP ZeroWindow on writing a large file to a Windows share?

I've been given access to a share on a Windows Server 2003 SP1 system (10.a.bbb.ccc) which is a file and printer server, and regularly large files get copied to that share. However, occasionally such ...
2
votes
1answer
291 views

Tomcat not getting data from TCP recv-Q, hanging

I have a program which is essentially a tomcat server with postgreSQL DB running on CentOS Linux 6.3. When a client submits a larger amount of data (~10MB) to the server, which should be received on ...