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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How to find source of TCP failed connection attempts? [closed]

I've got a host that has experienced a sudden increase in the rate of failed TCP connections. It's gone from something like 0.3/sec to 1.5/sec. Regardless of the severity of my particular issue, ...
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63 views

Tomcat fails to return syn requests to F5

I have an F5 LTM sitting in front of two tomcat servers which host 4 applications. When I initially create the pools and add the members to the LTM I can hit all applications. This is the weird part, ...
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1answer
234 views

rmem_max more than rmem_default

I just installed centos 6.3 freshly and noticed the following: [root@localhost user1]# cat /etc/redhat-release CentOS release 6.3 (Final) [root@localhost user1]# [root@localhost user1]# cat ...
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3answers
68 views

How many packets will it take to send particular data?

If I know the maximum packet size is 1500 bytes say for Ethernet frame v2 then for example I want to transfer 1 KB over the Internet which is roughly 1024 bytes. Will the packet be split into many ...
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1answer
52 views

Support of batch mode in tcpkill

I fire tcpkill with destination ip. Example tcpkill host 10.0.2.184 The problem I am facing is that, tcpkill doesn't come out after killing all tcp connection. After killing all tcp connection it ...
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1answer
307 views

Is it fine to turn off tcp window scaling and tcp timestamps on server?

Our application is running on Amazon server and we were continuously facing the issue related to tcp handshaking. Sometimes we were not able to connect to our application or telnet on port 80 of our ...
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1answer
43 views

Off-loading HTTP traffic

Need help in off loading HTTP traffic. My web server is having a lot of traffic resulting in slow response. It is also getting requests on port 80 from various mobile applications too. Traffic from ...
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2answers
142 views

MySQL connection errors when client server bandwidth is exhausted

I have several servers with a lot of outgoing traffic using nginx. When the bandwidth is exhausted (1Gbit), I have problems connecting to my mysql server from those servers. The connect always fails ...
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2answers
95 views

Network In greater than Network Out?

Stat Image: http://carzz.co/network.png Running a small image website on EC2 without much traffic to speak of (800 user sessions per day). In looking at the EC2 Monitoring on the newly created ...
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1answer
184 views

How does a file get sent over an HTTP connection? [closed]

A teacher of mine says when you are browsing a web server such as apache2 that has file/directory listing enabled then it secretly opens an ftp server to transfer the file. This confuses me, though ...
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1answer
149 views

Simulate tcp disconnect using socat

I am trying to use socat command to simulate a tcp disconnect between my client service and EMS broker process on a remote host. I am running this socat command socat TCP-LISTEN:8123,fork ...
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2answers
163 views

Optimizing OS for HTTP requests

We make a lot of HTTP requests. Recently, we've started thinking about optimizations at the OS level to make more requests from a single machine. In order to check the performance of our OS, I've ...
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2answers
180 views

once in a while windows / .net application ignores the tcp fin flag

i've run into a network problem which i cannot solve. on a few computers running windows 8.1 and communicating with linux http server tcp connections dangle on the windows side instead of being ...
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2answers
189 views

VMWare NAT releasing SYN packets from guest but not admitting SYN/ACK packets to guest

VMWare Server 2.0.2 Host OS is Windows Server 2008 R2 Standard Guest OS is Windows XP I am using VMWare VMNet8, the NAT network. The VM guests can't see out to the network around the VM host. Packet ...
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0answers
118 views

How can i detect and diagnose local network problems on a multi-server environment?

I'm a software engineer who trying to detect (and solve if possible) weird local networking problems since 2 weeks on multi-server hosting environment. We bought 3 dedicated boxes with 32GB ram 8 ...
2
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1answer
86 views

How do you change tcp_congestion_control on OpenVZ?

I have a network of OpenVZ machines that I am testing various congestion control methods on. I need to know how to change the congestion control. Currently I get nothing but permission denied. Is it ...
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1answer
436 views

How to enable/disable TCP DELAYED ACK parameter on SUSE linux?

I want to disable TCP DELAYED ACK parameter on SUSE Linux Enterprise Server for some performance tuning operations. I have used sysctl command but it does not list this parameter. also in SUSE ...
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1answer
53 views

routed network, subnetwork clients has broken tcp connection

I manage a linux server which works also as a router, and route between following networks: PPPoE (to connect to ISP) (default gw) wired network 2x VPN networks (PPTP and openVPN) wireless AP (DHCP) ...
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1answer
57 views

Routing between two PC

I have two computers connected by wire directly: PC-1 ============= PC-2 PC-1 configuration: IP Address: 192.168.1.1 netmask: 255.255.255.0 PC-2 configuration: IP Address: 192.168.1.2 ...
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1answer
143 views

Oracle 11g TNSLSNR LAST_ACK connection flooding

We have Windows 2k3 EE SP2 with Oracle 11.2.0.1.0 DB installed. The DB is used by different applications (including web-apps and services). From time to time, we have some problems with the web ...
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1answer
746 views

TCP port numbers reused and TCP Retransmission

Facing issues due to TCP Port Reuse and Retransmission for HTTP traffic. My deployment is as follows: enter image description here I have a squid proxy installed on a unix machine which is sending ...
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1answer
48 views

What packet to ignore to not have ssh terminated on brief connectivity loss?

It seems like sometimes there are some connectivity problems around the edge of our network to certain other networks, and my ssh sessions with some remote servers, which themselves have no ...
3
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1answer
350 views

Troubleshoot Broken TCP From OpenVPN Client To Server; But ping, traceroute Work

I'm troubleshooting an OpenVPN Server setup on OS X Mavericks. Prior to the 10.9 upgrade, this all worked, and I'm trying to isolate the problem to something fundamental or my server/client setup. ...
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1answer
3k views

Root cause of “curl: (56) SSL read: errno -5961” errors

I was evaluating some SSL failures, and noticed that when I use curl to one of the failing sites, I got curl: (56) SSL read: errno -5961; however, my google queries for that error didn't show the ...
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0answers
151 views

How to forward UDP and TCP traffic from one IP to another

I have a server with two LAN cards installed. I have one server in U.S and one in India. I have created a GRE tunnel to route all traffic from the U.S Server to my Indian Server. My traffic has ...
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1answer
111 views

Several Server Errors (No database connect, can't create TCP/IP socket etc

My server stops taking requests on my website today. It works for some time, but then the server just stops working and throws several errors: 500 Internal Server Error Warning: mysql_connect(): ...
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1answer
135 views

How to configure tcp wrapper

I have a server with ip-address 192.168.0.1 and a client with ip-address 192.168.0.2 both of them are able to connect with each other. Now the problem is I have configured TCP Wrapper on my server ...
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1answer
105 views

Prevent Linux from processing incoming ICMP Host unreachable packets

I have a test setup with one host on a network (10.1.0.0/16) talking via TCP to another one on another network (10.2.0.0/16) and a gateway in the middle. Sometimes, the TCP connection is lost and ...
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1answer
233 views

Random TCP Resets

We got randomly TCP "reset" error when we send request to remote server. Log from remote server Cisco TCP Connection Terminated,Nov 05 14:43:39 EST: %ASA-session-6-302014: Teardown TCP connection ...
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1answer
54 views

Request to server x Reply from server y

I need some advice from you guys: I'm dealing with a custom loadbalancer/software for which we will use 2 main servers and about 8 slave servers. In short: User sends request to main server, main ...
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2answers
210 views

Using proxy server to redirect MySQL traffic to multiple servers using standard port?

Is it possible to redirect MySQL (tcp) traffic to multiple servers based on domain name alone? Our DNS is setup to point several sub-domain aliases to one proxy machine. (running haproxy and ...
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1answer
85 views

TCP syn cookie calculation on Windows Server

Windows Server uses uses TCP syn cookies to protect itself from syn-flooding attacks. Is it known, how the operating system (Windows Server 2008 R2 and Windows Server 2012) calculates the syn cookie? ...
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0answers
203 views

Should I set rto_min for a route inside data center?

We have a few dedicated server rented in a data center with debian 7, kernel 3.2. We use one of those servers as a database server. The network between our application server and database server is ...
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0answers
393 views

How to stop NAT dropping idle connections?

I have a TCP connection that can be idle for many hours. The traffic is flowing from the server to the client only. One might say it's kind of push notification. My home router, however, tends to ...
2
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0answers
86 views

Change TCP wait for ACK timeouts in Win7/WinServer

Is there any possibility to change default wait for ACK timeout in TCP network on Windows 7 or Windows Server ? I'm using very slow network ( 1200 bps ) and want to tweak TCP. When using default ...
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1answer
407 views

How do routers combine WAN and LAN traffic (packet data over wifi and ethernet)? [closed]

In my office, we have a leased line connection which is shared by some 20 users over wi-fi. This causes congestion on the router's end, resulting in slow speed due to high packet drops (and consequent ...
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0answers
89 views

How to get more NFS packet details from Wireshark?

How can I get Wireshark to give me details about NFS packets at this level of granularity? (as exemplified here here) Specifically, I am interesting in looking at the the "Stable" option toward ...
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2answers
222 views

DHCP serving has stopped working

Something happened in our server room over the weekend that had me in the office late Saturday night replacing two switches. After powering down both racks, I have an issue where none of the computers ...
0
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1answer
220 views

TCP packets larger than 4 KB don't get a reply from Linux

I'm running Linux 3.2.51 in a virtual machine (192.168.33.15). I'm sending Ethernet frames to it. I'm writing custom software trying to emulate a TCP peer, the other peer is Linux running in the ...
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6answers
558 views

Is it possible to redirect/bounce TCP traffic to an external destination, based on rules?

I'm not even sure if this is possible... Also, please forgive my ignorance on the subject. What I'm looking for is for "something" that would allow me to redirect all TCP traffic arriving to host A ...
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1answer
169 views

Bind9 as a caching resolver fails with mismatch ID on localhost but not external IP

I'm running Ubuntu 12.04 LTS on a machine on my private network. I have bind9 installed (v9.8.1-P1) via aptitude, so it appears to have put all the bits in the right places and the service starts ...
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2answers
4k 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 ...
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1answer
225 views

TCP DOS: How to terminate CLOSE_WAIT connections? [closed]

One of my servers is getting DOS'ed - there are a large number of connections in the CLOSE_WAIT state which are preventing legitimate users from connecting to the system. So is there any way to close ...
1
vote
1answer
184 views

SSL Connect timing out during handshake (client exchange re-transmission)

We have a Java LDAP client making SSL connection to AD. Some times the connect hangs with client and server re-transmitting Client Key Exchange and ACK packets continuously as shown below and ...
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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 ...
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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 ...
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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: ...
2
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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 ...
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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 ...
3
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1answer
424 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 ...