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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1answer
174 views

Low throughput on Debian + nginx/apache

On the same LAN/WAN I have a Windows server 2012 server running IIS 7.5 and a Debian (wheezy) server running Nginx 1.4.5. Both servers are connected to the same LAN/WAN. When I download a 10MB file ...
2
votes
1answer
76 views

How to filter for the most common problems with tcpdump/tshark

I am currently using the following command in Linux to get specifics on network problems. tshark -r file.pcap -q -z io,stat,1,\ "COUNT(tcp.analysis.retransmission) tcp.analysis.retransmission",\ ...
0
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1answer
32 views

TCP ACK Window shrinking

(Note: I am not a networking engineer) We are sending files to an outside vendor and getting random timeouts on different services. It seems that we are getting timeouts most often on larger files. We ...
7
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1answer
1k views

What is theoretical maximum of TCP traffic over GigaEthernet?

What is theoretical maximum of TCP traffic over GigaEthernet ?
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0answers
44 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 ...
-1
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1answer
60 views

FTP upload slows down when devices are connected via hub [closed]

I have a setup with a network hub and three Ethernet devices. One of them is a PC (running windows XP), two others are hardware components that need to communicate with each other over the network. ...
0
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1answer
100 views

Windows Server 2012, application needs administrative access to open port

How can I grant an application access to listen on one particular port, without running it as Administrator or disabling UAC? Per policy, had to transition from an old server (Windows Server 2003) to ...
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0answers
13 views

How do I cap each individual tcp stream, to a fixed maximum rate?

I've read but not in depth all the various traffic shaping docs and seen the long question on HSFC scheduling Does anyone really understand how HFSC scheduling in Linux/BSD works? looked at the ...
7
votes
2answers
1k views

TCP Dump, cannot understand these 4 lines?

I need support understanding these 4 lines. looks like tcp dump but im actully not understanding what exactly is happening here. 13:13:22.407445 IP 192.168.246.128.54955 > 192.168.246.13.80: S ...
0
votes
1answer
68 views

A LOT of connections from my external IP address to my web server

I installed Nagios recently on a Debian machine running an Apache web server among other things. The thing is that lately, Nagios tells me that the HTTP service is failing intermittently and it seems ...
0
votes
2answers
531 views

Recommended TCP keepalive settings for a busy server

We are having some network timeout issues on a Debian server that is quite busy, and maintains multiple connections to a number of other servers on the network. Here are our current TCP keepalive ...
1
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0answers
95 views

TCP High Send-q coupled with FIN_WAIT1 status

I'm having a problem with one of my webservers, which is taking minutes to completely render a web page. I had a look at the TCP connection and noticed that I have a very high value in the send-q ...
4
votes
4answers
1k views

Is there a way to see what is actually filtering TCP port communication?

nmap -p 7000-7020 10.1.1.1 Will output all the filtered ports Starting Nmap 6.40 ( http://nmap.org ) at 2015-03-04 12:18 EET Nmap scan report for 10.1.1.1 Host is up (0.00091s latency). PORT ...
6
votes
4answers
2k views

apache webserver unresponsive with server-status showing all child processes waiting for connection

My setup: i have 3 nearly identical webserver machines serving the same high loaded dynamic website with simple load balancing over dns. The service has been working for over two years with the same ...
0
votes
1answer
93 views

How do I open specific ports on Linux (an AWS instance of RHEL v. 7)?

I'm using RedHat version 7. My AWS instances are in a security group with ample permissions for inbound connectivity. I can do Yum updates. The servers can ping each other. I can transfer files ...
3
votes
3answers
621 views

tcp-upstream in unbound doesn't work. Use TCP for query upstream DNS servers really work in the real world?

Today I've been playing with some options in unbound.conf just for fun. I've enabled tcp-upstream but it doesn't work with some domains. OS: OpenBSD current. Unbound: 1.4.19 Examples with ...
1
vote
3answers
1k views

HTTP not finishing over LAN. Hardware cause?

On a customer server running Apache 2.2 on Windows server 2012 we're noticing that from time to time, some requests to the server never finish. Using wireshark I've found a bunch of duplicate ACKs get ...
0
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0answers
38 views

TCP forwarding IIS

i have a server, let's call it: GATEWAY-SERVER (GS). On GS i installed a custom build TCP proxy/forwarder. This tool accepts connection TCP level and formulates a new request towards a TARGETSERVER ...
1
vote
1answer
795 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 ...
0
votes
1answer
26 views

SNORT only alerting on inbound traffic

I am trying to raise an alert when someone is setting up a connection to PORT 25 (tcp), whatever source or destination. For this i came up with this simple rule: alert tcp any any -> any 25 ...
0
votes
1answer
16 views

Windows Server 2008 sending regular TCP DNS requests to Forwarders

Our organization's primary DNS server is a Windows Server 2008 which two Forwarders set. I happened to notice on our firewall that this server is sending out regular TCP requests to the Forwarders in ...
3
votes
1answer
620 views

How to debug why WAN TCP/IP throughput is lower than expected?

I'm trying to figure out why tcp/ip throughput between two hosts I control is much lower than expected. Host A: internet connectivity provided by Comcast (Residential) in Boston Metro -- can ...
3
votes
1answer
173 views

(Why) does FreeBSD 'net.inet.tcp.always_keepalive' violate RFC1122?

While working on a server application that runs on FreeBSD and uses TCP, I noticed that TCP keepalive probes get sent even though my application explicitly disables SO_KEEPALIVE on TCP sockets. ...
3
votes
2answers
7k 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. ...
1
vote
1answer
8k views

Windows 7 default TCP connect timeout

Is there a way to change default TCP/IP new connection timeout ? In earlier Windows, timout value was stored in registry, as said here: Which is the default TCP connect timeout in Windows? But this ...
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4answers
49k views

Which is the default TCP connect timeout in Windows?

Which is the default TCP connect timeout in Windows? There is a registry key to configure it or it's set dynamically?
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3answers
222 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 ...
0
votes
1answer
40 views

length of Tcp segment exceed MSS

I find a weird behavior in my Linux system, when I curling a web page, the received TCP segments are significant larger THAN the MSS. here is the output of tcpdump: 00:00:00.000000 IP ...
0
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2answers
52 views

Get a website's host machine's OS/server software without access to the server

Is there a good methodology to find the operating system and server software that is being used on a served website that you don't have SSH access to? What I'm doing right now is looking at TCP/IP ...
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0answers
65 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 ...
2
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0answers
439 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 ...
4
votes
6answers
844 views

Effect of distance from server on page load speed

I measured the load speed of a static image file severed by nginx from my server (using pingdom service). The server should normally process this request within few seconds. My server is located in ...
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0answers
297 views

tcp connection reset [RST, ACK]

getting this errors looks like server is restating the connection because of some packet loss any possible suggestion's to figure out this 37713 591.925575000 ...
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0answers
185 views

Cisco ASA firewall blocking requests to internally hosted DNS server

I have a DNS server behind a Cisco ASA firewall. The Cisco firewall is performing NAT. When inside the network, I can NSLOOKUP directly to the server. When the client is external, requests time out. ...
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1answer
64 views

How to redirect all incoming packets to sniffer in Linux using iptables?

I need to redirect all incoming tcp packets from eth0 to current host (change ip address from 1.1.1.1 to 1.1.1.2) and outgoing tcp packets from sniffer from eth1 to another host(from 2.2.2.2 to ...
0
votes
1answer
68 views

server is not responding on SYN packets

On the attached tcp dump, the first two SYN packets (#21800 and 21801) came to the server, however SYN ACK was sent for the second SYN. Is that correct behaviour? My understanding is that the client ...
0
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3answers
75 views

how to use tcpdump to log only certain data in real time

I'd like to monitor network interfaces but only log things likes errors, collisions and dropped packets. The send that to stdout. – Can tcpdump be configured to do this?
1
vote
2answers
290 views

Checkpoint FW1 logging

When I view the logs created for my checkpoint fw1, does it log connections on receiving the syn, or does it wait till the three way handshake completes? If it logs after the syn, is there anyway of ...
17
votes
3answers
11k views

What's the difference between Unix socket and TCP/IP socket?

It's from this answer: http://stackoverflow.com/questions/2482411/is-this-pdo-bug-fixed-now/2482424#2482424
2
votes
1answer
2k views

How to capture retransmitted packet info with tcpdump?

TCP retransmission rate on a host are often a good indicator of network problems. How do I find out the source and destination IPs for the packets that are being retransmitted? For context, on hosts ...
0
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0answers
35 views

PCI says port 36141:TCP is blocked. But 36141:TCP open on iptables

PCI compliant scan fails due to port 36141:TCP is being blocked on website. I verified I cannot connection via 36141 on same server to itself: # nc -zv 127.0.0.1 36141 nc: connect to 127.0.0.1 port ...
3
votes
1answer
508 views

Unix socket connection limit

This may appear like an already discussed/answered question. But I am specifically looking for info which I couldn't find anywhere answered clearly. I have an Nginx + php-fpm setup which uses unix ...
2
votes
0answers
50 views

Linux - Outgoing connections from process timeout after the process restarts

banging my head against the wall with this one... I have an Ubuntu Linux server, on top of which our own process which holds 40K persistent connections to external services. When the process ...
0
votes
1answer
145 views

Concurrent TCP connections on Azure can be upto 500K. Really?

Let me be very clear at the outset that I am new to cloud technology. All I know is cloud servers are easily scalable (i.e. adding physical hardware is transparent to applications and users) and ...
13
votes
4answers
70k views

What causes duplicate ACK records?

We're reviewing Wireshark captures from a few client machines that are showing multiple duplicate ACK records which then triggers retransmit and out-of-sequence packets. These are shown in the ...
0
votes
1answer
207 views

NetTcpPortSharing process won't start on Windows Server 2012 R2

I have a problem in Windows Server 2012 R2 : I have searched and try everything I know to fix this, but I cannot start NetTcpPortSharing service and therefore I cannot configure Windows Server ...
3
votes
0answers
175 views

TCP congestion collapse

I am experiencing suboptimal performance on an EC2 instance connecting to an RDS instance. This particular instance was built before VPC's existed, so all the traffic is flowing through a single ...
1
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1answer
175 views

Linux clients can't connect, server and TCP Windows Size / Timestamps issue

We have a problem that a number of clients (all linux Ubuntu) are sometimes not able to connect to a remote server over SSH. If the problem occurs, Windows clients don't have that problem and can ...
0
votes
4answers
8k 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 ? ...
6
votes
2answers
807 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 ...