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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Max client TCP connections through a router

I've just been thinking about what the maximum number of client connections would be out of my home LAN to a single server on the internet. My home router is also NAT'ing the connections to convert ...
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1answer
148 views

Socket based byte counts

I see a lot of tools to get the RX and TX byte counts for transmission on interfaces, is there any tool/program that I can use to get a total transmitted byte count for a single specified socket? I'm ...
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2answers
2k views

Reduce firewall rules by half - one iptables rule for tcp and udp

I have a number of iptables rules on my firewall that look like this: iptables -A zone_lan_forward -p tcp -d 1.2.3.0/24 -j ACCEPT iptables -A zone_lan_forward -p udp -d 1.2.3.0/24 -j ACCEPT Is ...
9
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3answers
1k views

Lower TCP throughput from 1Gbps server than 100Mbps server over large RTT

We've got infrastructure distributed in a few major locations around the world - Singapore, London and Los Angeles. The RTT between any two locations is over >150ms. We've recently upgraded all of ...
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4answers
576 views

Can I find out what certificate revocation server an application is contacting?

I'm trying to install an application on a machine running Windows XP Pro. There are two different servers being contacted, both using the same wildcard certificate (GoDaddy). One via https, one ...
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1answer
104 views

Minimal handshaking necessary before establishing TCP connection

I have a Windows PC that is running a TCP server on port 9000. I also have an FPGA which is directly connected to the PC via a 10G port. The FPGA can send ethernet frames to establish and maintain a ...
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4answers
706 views

Rsyslog not logging from remote server

I am trying to set up a centralized log server. I have central server (A) receiving logs via a remote server (B) on port 514. I know it is receiving these. Here are a few entries from a tcpdump on ...
2
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1answer
361 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 ...
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4answers
255 views

Why is the TCP checksum inverted?

From the Wikipedia page: The checksum field is the 16 bit one's complement of the one's complement sum of all 16-bit words in the header and text. Why, after summing the 16-bits in the header ...
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2answers
237 views

TCP vs UDP Error-Checking

I've bounced upon two articles that describe in-depth on how TCP and UDP connections work. However there is some kind of inconsistency. Where one article tells me that UDP does no Error-Checking at ...
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0answers
97 views

tcp recycle and retransmission

TCP recycle reduces TIME WAIT by reusing sockets. It avoids collision with older packets by storing timestamp and receives packets with greater TCP timestamp. What happens when the client retransmits ...
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1answer
93 views

What process does 'own' socket in 'Time Wait' state?

Main question I see following line in netstat. Does it means this socket doesn't belong to any process? #>netstat -tpn|grep TIME_WAIT| head -1 tcp 0 0 ::ffff:127.0.0.1:5555 ...
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1answer
185 views

TCP RWIN, MSS and MTU [closed]

I have been doing some reading into TCP Receive Window (RWIN), Maximum Segment Size (MSS) and Maximum Transmission Unit (MTU). Right off the bat I have some questions and I need a power user's help! ...
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1answer
185 views

How to disable Xvfb using TCP ports when using pyvirtualdisplay (Python)?

Trying to use pyvirtualdisplay for Python to start some applications with a virtual Xvfb X terminal. However, we've seen port clashes and would like to disable Xvfb from using TCP ports. I have ...
2
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1answer
27 views

TCP Reno Window Size drops to 0

I'm working on a task on comparing TCP Tahoe and Reno. Tahoe drops the window size to 0 every time it detects packet loss, that is clear. However, when I plot my window size for Reno, it does fast ...
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1answer
225 views

TCP/IP routing: accessing a LAN device with wrong static IP configuration

I forgot to change the static IP of a network device before moving it from my datacenter network to my home LAN. Since it isn't configured properly for my LAN network, I'm not sure how to access it. ...
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0answers
70 views

Cant connect to mysql server

I'm trying to configure a freshly installed mysql server to listen on port 3306. I've removed skip_networking, I have changed bind-address=172.20.33.1 (which is my server ip) and it completely ...
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2answers
759 views

How do I get my ubuntu server to listen for database connections?

I am having a problems connecting to my database outside of phpmyadmin. Im pretty sure this is because my server isn't listening on port 3306. When I type: sudo netstat -ntlp on my OTHER working ...
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2answers
42 views

Three Duplicate acknowledgements

I understand the process of congestion avoidance where you trying to control the level of congestion in a network, and avoid loss of packets. But how can there be three acknowledgements, even if one ...
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1answer
112 views

svnserve -d child process spawning and svn connections under netstat

I see many svnserve -d processes running on my CentOS 6 box, one with the PID 400 and PPID 1 and the rest with PPID 400. I take this to mean the first one is started by init scripts (i know it is) ...
2
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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 ...
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0answers
276 views

How to interpret findings on TCP Send/Recv Buffers

I have an application running on a CentOS machine that connects to a remote DB server on another CentOS machine. Every once in a while, without any discernable warning signs, the application seems to ...
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0answers
90 views

reset packet sent when receiving big TCP traffic

A client receives chunks of TCP segments from a server, which total 20MB or more. Sometimes the client will send RST segments to the server before terminating the TCP connection. Before sending RST ...
2
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2answers
132 views

Is TCP RWIN set by application or OS?

I have a situation where an application is listening on a TCP port and every once in a while, as seen in tcp dumps, gets its Receiving Window (RWIN) set to zero. When this happens, its Recv-Q stops ...
3
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1answer
120 views

TCP 443 Connection goes into server but never reaches Apache2 (Passenger)

We have some weird problems, when external servers try to connect to our Website on Port 443(TCP) which is an Apache2+Passenger and a Rails Application. The problem only happens rarely. I started to ...
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1answer
52 views

How to diagnose why a port is broadcasting a “ZeroWindow” status

I have two CentOS servers (one is an app server, the other is a DB) communicating over a port. Every once in a while, the application server starts broadcasting that the port connected to the DB has a ...
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1answer
235 views

UDP packets dropped

A host sends UDP broadcast, but its UDP packets are not received by any other hosts in the same subnet. However, its TCP traffic with others hosts are OK. I observed this using tcpdump. Could it ...
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3answers
95 views

RHEL (say 5.6, kernel 2.6.18-238) with dual IP address (IPv4v6)

So I have a SERVER that that utilizes RHEL's (assume 5.6) underlying kernel for setting up TCP connections and other networking aspects. My deployment need requires that the SERVER have dual IP ...
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2answers
223 views

IP and Port Forwarding on ASA 5505

I have an ASA 5505 with outside network of public ips 95.123.234.64/26 and inside network of private ips 10.22.33.0/24. I would like to redirect any tcp traffic that hits 95.123.234.67:80 to a public ...
3
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1answer
518 views

Does a growing number of TIME_WAIT connections affect server performance?

I have 2 servers, both running RHEL 6, one for Apache 2.2 and one for memcached (memcached-1.4.4-3). I noticed an increase in the number of TIME_WAIT connections on the Apache server netstat -n | ...
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3answers
161 views

Send TCP/IP packets down three routes and pick fastest

Does there exist a way to split TCP/IP traffic across three routes and have the first packets to reach the destination be used? I'm imagining something like multi-homing but with the requirement that ...
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1answer
183 views

Is tcp_keepalive application dependant on Linux?

According to http://tldp.org/HOWTO/TCP-Keepalive-HOWTO/index.html , the kernel keepalive function occurs at the OS level, and doesn't require an application to explicitly call it. However I also read ...
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1answer
62 views

Problems with connecting to TCP server

I have two PCs in the same LAN: "A1" and "A2". There is another PC in a different LAN: "B". A TCP server is listening on machine "B", port 80. From machine "A1", I can connect successfully to machine ...
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1answer
64 views

Is a tcp packet with only FIN flag set valid?

got some packets dropped, but from what looks like legitimate IP
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1answer
442 views

ffmpeg simple RTMP streaming

I am trying to launch up a rtmp transcoder server using ffmpeg; that receives udp MPEG-TS streams as input, transcodes it; and generates an rtmp output to a URL, that can be accessed by users to ...
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votes
1answer
283 views

Telnet Port 23 Not Responding' [closed]

I have an assignment that requires remote access into some Cisco routers. According to Netlab, it uses TCP port 23. I'm unable to pass the port test. I'm on Windows 7, I've tried all major ...
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1answer
91 views

How to run Different congestion control algorithms in FEDORA 17?

I need to use different congestion control algorithms for tcp flow. How can I continue using those flow congestion algorithms from Fedora 11 in Fedora 17?
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3answers
76 views

Which bit represents which TCP flag?

For instance, a WireShark capture filter example I found - tcp[13] & 8 == 8 represents packets with PSH flags. How do I count the 8 ? Based on the wikipedia image, PSH is in the middle of ...
2
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1answer
51 views

SVN repo browser does not show an open TCP connection on backend

When I am connected to mysvnserver using the repo browser (TortoiseSVN), I do not see an open connection when I perform a netstat on the mysvnserver box and grep for my computer. What is the ...
1
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1answer
946 views

openvpn tcp or udp (specific situation, reliability-layer collisions)

My question is whether to use TCP of UDP for my openVPN connection. I've set up a simple network for a startup company that allows users from the outside to acces the network via an openvpn server (in ...
3
votes
1answer
468 views

Rotating outgoing IPs using iptables

I am trying to rotate outgoing IPs using iptables. I want to rotate outgoing connections between three IPs, one by one. Here is what I'm doing with iptables: root@server:~# iptables -t nat -I ...
9
votes
1answer
231 views

Where can I embed proprietary information in a layer 2 or layer 3 packet?

The Citrix Netscaler has an interesting property that embeds information in the TCP packet that gets sent to the host. This property is echoed back to the Netscaler in such a way that the Netscaler ...
0
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1answer
170 views

Effects of IW10 (initcwnd 10 initrwnd 10) on high speed LAN based TCP/IP communications?

What does changing the number of packets sent during the initial congestion window to 10 have on LAN connections? Via: ip route change default via GATEWAY dev INTERFACE initcwnd 10 initrwnd 10 Is ...
10
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1answer
525 views

TCP congestion control for low-latency 10GbE -> 1GbE network?

I have a server with a 10GbE connection to a switch, and 10 clients each with a 1GbE connection to the same switch. Running nuttcp in parallel on each of the clients, I can push 10 TCP streams of ...
0
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1answer
65 views

Secure TCP based protocol through an application layer firewall

I have two networks, one considered secure, lets call it A and one considered insecure, B. The software I need to use, uses HSMS, a protocol based on TCP with no security built in. Now the problem is ...
2
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1answer
802 views

Tuning tcp_keepalive_time for Node.js leak

I'm currently having a socket leak with my Node.js application. This bug is also posted here. I hope to fix this soon. CLOSE_WAIT and FIN_WAIT2 seem to be the major problem. Connections: 1662 ...
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2answers
170 views

Server 2012: SYN, no ACKs, on TCP ports higher than 6000

Seems ridiculous to read it back out loud, but I'm at a loss here. Server 2012 Standard. Runs a daemon for an accounting package on TCP 12502; at some point, the server stopped accepting connections ...
5
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1answer
1k views

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 ...
3
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0answers
177 views

TCP tunning for ssh port forwarding [closed]

I am using an ubuntu openssh server to allow users to connect to and do dynamic port forwarding. the performance is good until about 100 users are connected. beyond that the performance is dropped too ...
2
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0answers
441 views

mysql client can't read query result?

So I have this machine running an XMPP server which connects to its MySQL database. When I start load-testing it, all goes fine up until after about 500s when I notice: Caused by: ...