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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TCP under OpenVPN is very slow (tsg attached)

I have a very weird problem with OpenVPN. Most VPNs work fine, except this one. Here I get very low performance from TCP connections, but the CPU load is low (so, not a CPU issue). OpenVPN is ...
0
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0answers
54 views

Single TCP-CLOSE_WAIT connection brings down application till restart

Recently found a behaviour where my application had a connection in TCP Close_wait state till the app was restarted (after about 5 hours). But during this period the SUnreclaim space was also ...
0
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1answer
52 views

cannot send emails to other Web servers

I'm trying to limit my server's open ports in CSF. The IPv4 port settings include: # Allow incoming TCP ports TCP_IN = "22,25,53,80,110,143,443,587,3654,53343” # Allow outgoing TCP ports TCP_OUT = ...
0
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1answer
81 views

What do I need to consider when setting TCP idle timeouts?

What's purpose of having a [low] TCP idle timeouts? E.g., why have a 60 second timeout on a firewall or load-balancer? Is it a memory management or /performance optimization thing? Is there a security ...
1
vote
1answer
573 views

Linux iptables - reject tcp SYN with RST

I am doing an implementation on a linux machine to reject incoming telnet requests from wan side telnet port 8023. The functionality is achieved by using the below iptables rules. The first rule in ...
1
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0answers
44 views

periodic connection timeouts to nginx server

We have the following setup: One nginx server as a loadbalancer in front of four worker application servers. The nginx server get about 100 requests per second, sometimes more that that, active ...
0
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0answers
28 views

Want to route NFS response via an interface. What will the source ip of the packets being sent out?

The NFS server is listening on an interface for a new connection, once a new TCP connection is established the NFS operation is carried out. I'd like to send this NFS response via a different ...
0
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0answers
133 views

Proxy / Squid 2.7 / Debian Wheezy 6.7 / lots of TCP Timed-out

I'm facing a lot of TCP timed-out on a busy cache server and here below my sysctl.conf configuration as well as an output of netstat -st Kernel 3.2.0-4-amd64 #1 SMP Debian 3.2.57-3 x86_64 GNU/Linux ...
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0answers
115 views

Cannot connect to Solaris Server when Oracle GoldenGate process uses the port

I'm trying to test the Oracle goldengate to replicate data between two databases on the same server. So I installed two databases and two goldengate homes in the same machine. The goldengate ...
0
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1answer
319 views

iptables and TPROXY support

I'm running iptables v1.4.21 on Ubuntu 14.04 and is trying to setup iptables to use TPROXY. How can I check whether my current build of iptables supports TPROXY? I can check TPROXY support for ...
2
votes
1answer
162 views

remote login failed on windows XP, but remote telnet successful on mac

I recently set up an Oracle DB, started the listener on port 1561, and enabled TCP access. I then opened that port to all incoming connections. When I get on my Mac - I can use telnet remoteserver ...
1
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1answer
27 views

TCP rsyslogd events showing up as 2000 character continuations

I'm taking syslog events from a proprietary app. This could be the app's fault or it could be rsyslogd. Events are written like: Aug 15 16:00:00 10.11.12.13 Event1 from this wonderful product using ...
1
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2answers
58 views

When a socket switch to TIME_WAIT state, why I can't see its inode number?

I'm developing a program in python that parses /proc/net/tcp informations, but unfortunately, while I was doing this, I saw a strange thing. Practically, when a socket change in TIME_WAIT state, ...
-1
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1answer
44 views

CentOS 5.10 TCP Sequence Number

We have done a security check on a server and its come back with Linux Kernel TCP Sequence Number Generation Security Weakness. We are looking to correct this being flagged up on the check We are ...
2
votes
2answers
63 views

Using (r)syslog's dynamic file generation

I am in the middle of configuring a (r)syslog server as a remote server that receives logs from various clients. I wonder whether there is a nicer way to dynamically generate multiple file names as ...
0
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0answers
36 views

Is The MaxUserPort Restriction In Windows Server Accumulative Across All Local IPs?

I have a Windows 2003 server with multiple IPv4 addresses assigned to it. Each single IP address doesn't use more than 2000 outbound sockets/connections. Collectively though across all IPs, this adds ...
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1answer
102 views

HAProxy - proxy to webserver via tcp

I have a simple web application, All requests to that application are HTTP based (RESTfull API and standard ajax) I have an haproxy before my tomcat cluster. So now i have clients that http request ...
2
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0answers
307 views

TCP Connection Issue Between Linux Machine and VMWare Windows Server

I have a TCP connection issue as follows. The setup: VMWare Virtual Machine: Windows Server 2008 R2 DataCenter SP1, IP: 192.168.2.111, DG: 192.168.2.254 Host Machine: Windows 7 Professional SP1, IP: ...
1
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1answer
378 views

Troubleshooting High TCP Retransmit Rate

I've been attempting to troubleshoot a network issue that presents with very high rate of TCP retransmits. 36 samples (taken with Wireshark 1.10.8 running on 32-bit Windows 7) totaling a little over ...
0
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3answers
171 views

How does anycast work with tcp?

TCP, being stateful, should require subsequent packets to reach the same server. (Stateless) HTTP runs on top of TCP, and CDN's can use anycast. So how does TCP work with anycast? What if the syn ...
0
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0answers
56 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 ...
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 ...
6
votes
2answers
617 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 ...
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1answer
144 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 ...
2
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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 ...
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0answers
113 views

trying to reach a port forwarded server from the subnet using the public IP not working

I set up a server which is connected to my router. The router forwards a port of my server. So when I scan that port using http://www.t1shopper.com/tools/port-scan/ I got: 188.143.126.14 is ...
0
votes
1answer
65 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. ...
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1answer
93 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 ...
3
votes
2answers
272 views

FTP client/server failing on switching to PASV mode

Update The ISP said that they recently added the area where this computer is located to their IPv6 network. Coincidentally, ever since the day they added that area to their IPv6 network, no FTP ...
0
votes
2answers
97 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 ...
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0answers
52 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 ...
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0answers
42 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 ...
35
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5answers
5k 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 ...
1
vote
2answers
79 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?
8
votes
5answers
742 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 ...
0
votes
1answer
91 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 ...
7
votes
2answers
374 views

How does Intel AMT (Active Management Technology) not interfere with the TCP/IP host stack?

The Intel dev kit I've been using includes a remote management feature (also see the Ubuntu man page here) which allows remote reboots in case the operating system hangs. It has the capability of ...
2
votes
1answer
457 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
426 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 ...
3
votes
2answers
604 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 ...
0
votes
1answer
610 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.
3
votes
1answer
110 views

Is net.ipv4.vs.timeout_timewait used also for IPv6?

Does this setting for TCP net.ipv4.vs.timeout_timewait apply only to TCP connections established over IPv4 or does it also apply to TCP connections established over IPv6? I have found this for ...
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votes
1answer
65 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
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0answers
36 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
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1answer
293 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 ...
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0answers
287 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 ...
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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
vote
1answer
378 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 ...
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3answers
361 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 ...
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0answers
77 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?