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 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 ...
9
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1answer
127 views

SynProxy can not return syn ack packets with asymmetric dual bridge topology

I have a asymmetric dual bridge topology as shown below when i connect from 172.16.11.5 and 172.16.10.6 with ssh but i can not connect because of SynProxy. ------- ...
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1answer
16 views

Nginx Configuration:504 Gateway Time-out error

We are using Nginx as a Load balancer. Nginx having IP address of :10.110.0.200 and address of host machines are 10.110.3.20|10.110.3.21 this is the configuration file: upstream test1 { server ...
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1answer
46 views

Is it possible to run 2 concurrent tcpdump with different options?

I need to run 2 concurrent tcpdump commands with different arguments/options. Why ? Because we wrote some long long scripts compatible with following options : tcpdump -ixenbr0 -s 400 -n -A 'port sip ...
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1answer
1k 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 ...
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20 views

Strange TCP Connections - How to kill [on hold]

My parents Mac is having some random issues - my mum paid £160 to get the computer repaired as there were some "trojans" according to the guy on the phone from india On hearing this news I had a ...
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3answers
4k views

Monitor loopback traffic (monitor MS TCP Loopback inteface traffic) with Microsoft Network Monitor 3.4 - possible?

I've downloaded NM 3.4 from microsoft.com and it appears that the software doesn't capture traffic on MS TCP Loopback interface. When I ping 127.0.0.1 address, NM shows no packets flowing. I've tried ...
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1answer
2k views

option http-server-close on HAProxy haproxy-1.5-dev19 will result in Connection: close header sent in response

I basically have the following issue: whenever I add option http-server-close to the haproxy config (either in frontend or backend section), haproxy will send a Connection: close header in the ...
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3answers
4k views

Configuring keepalives with TOAD client communication

I have a scenario where long-idle sessions of TOADSoft client communication with the Oracle server seem to be torn down as they timeout on an intermediate state-full firewall. These sessions could ...
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4answers
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1answer
75 views

Millions of TCP FIN-ACK retransmissions blocking traffic on my desktop machine

In a few minutes I have received about 7 millions(!) FIN-ACK packets from IP address that belongs to Google 74.125.133.188 what totally blocked network traffic on my desktop(!) machine. Other ...
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0answers
72 views

Does Fast Retransmit and Retransmission Timer work at the same time?

When Fast Retransmit is implemented, if I received packet 1, then I will send an ACK that says I need packet 2, and then if I received packet 3, I will send a duplicate ACK that says that I need ...
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9 views

Why is server refusing new connections?

One of our proprietary closed source server applications sometimes stops accepting new connection from remote nodes on its server port. Remote nodes that are already connected work fine. Any new ...
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4answers
3k views

Need help troubleshooting intermittant TCP timeout in HAProxy

I have an application where the client connects to a server via a simple TCP based protocol over TLS/SSL. In development, this has worked great for many months while we were building our application ...
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1answer
930 views

why 5 rx queues per NIC

On my office server, the output of cat /proc/interrupts displays one tx queue and 5 rx queues. Is this due to NIC hardware capabilities or can you configure multiple receive ring buffers in linux per ...
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1answer
1k views

How to increase nginx connections

I am facing the problem of nginx max connection issues. I am not able to increase max active connections(520) made by nginx. Some time it is using whole writing (516) operation connections. and due to ...
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1answer
33 views

Unable to set TCP_NODELAY with setsockopt on CentOS

The call to setsockopt seems to succeed, but checking with getsockopt shows that TCP_NODELAY has not been set properly. Below is the relevant section of my strace. Am I missing something? ...
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25 views

Tcp Dup Ack in response to Ack

I am new to analyzing tcp communication and right now I am struggling with a communication problem. Topology: [server 172.27.15.1 1Gb] -- copper-- [1Gb switch 1Gb] -- fiber -- [1Gb Switch 10Mb] --- ...
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1answer
745 views

Disable kernel processing of TCP packets for raw socket

I'm working on a TCP/IP implementation, for an embedded device, that I want to test from a Linux user space process using raw sockets. raw(7) says that Raw sockets may tap all IP protocols in ...
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5answers
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How passively monitor for tcp packet loss? (Linux)

How can I passively monitor the packet loss on TCP connections to/from my machine? Basically, I'd like a tool that sits in the background and watches TCP ack/nak/re-transmits to generate a report on ...
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3answers
1k views

Windows Server 2008 - unable to bind any TCP port

OS: Win Server 2008 RC2 Windows firewall on (no effect when off) I have suddenly been plagued by an issue in which I cannot find any similar ones with a search. I am running about 20 game servers ...
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2answers
3k 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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0answers
8 views

Can I use MS Host Integration Server to connect to an IBM without using SNA

I'm sorry, this will represent a lot of information, but I'd like to avoid some of the back and forth I'm having with various forums trying to resolve this issue. So please, bear with me. I've taken ...
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0answers
17 views

What technology do data center use to guarantee low RTT?

I was reading about data-center-tcp DCTCP and the paper was talking about the low retransmission timer (RTT) of about 250µs, but didn't state how that is being done. Somewhere else I read that DCTCP ...
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4answers
417 views

Why is my web server dropping connections with a TCP reset at high load?

I have a small VPS setup with nginx. I want to squeeze as much performance as possible out of it, so I've been experimenting with optimization and load testing. I'm using Blitz.io to do load testing ...
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1answer
26 views

Does ColdFusion use TCP Ports?

I am trying to access a link on our network. Whenever I try, the page times out. I have discovered that this link is a Adobe ColdFusion web page. Does ColdFusion use a TCP port other than port 80? I ...
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3answers
751 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 ...
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1answer
81 views

Slow Upload to IIS Server

I have a Windows 2012 R2 Server running on an Amazon EC2 instance with IIS 8.5. It hosts a web application, and a custom WebDAV server that interacts with the same database as the web application. I ...
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7answers
10k 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 ...
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20 views

better alternative for tcp_syncookies in linux

In an effort to prevent DDOS attacks I followed suggestions to leave /proc/sys/net/ipv4/tcp_syncookies value set to 1 in my linux box to enable TCP syncookies. However, when I look at this URL: ...
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1answer
26 views

How to prevent TCP network flood triggered by KVM VPS clients?

How to to protect nodes/ detect and block KVM VPS clients that TCP flood the network ? I use SolusVM VPS management system. Recently one abuser toke several VPSs and flood it the datacenter network. ...
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40 views

How to fix the amount of bandwidth of iperf in tcp mode?

I'm working on some experiments about my master's degree project. I'm studying some load-balancers (I'm not supposed to cite them here) and the aim is to get for each bandwidth the cpu % usage of a ...
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1answer
144 views

lsof doesn't show the established TCP connection

On my system, if I run the netstat for a port, it returns: $ netstat -nat | grep "60964" tcp 0 0 192.0.0.1:60964 0.0.0.0:* LISTEN tcp 59 0 ...
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2answers
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TCP sequence number randomization

In a recent interview, my friend was asked about firewalls’ TCP sequence number randomization feature. The interviewer mentioned that we know that a firewall randomizes the TCP sequence number, but an ...
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1answer
130 views

How does server-side `TIME_WAIT` really work?

I know there are quite a few SE questions on this, and I believe I read as many of them as it matters before coming to this point. By "server-side TIME_WAIT" I mean the state of a server-side socket ...
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12 views

what is the significance of URGENT POINTER in TCP Header?

Urgent Pointer: Used in conjunction with the URG control bit for priority data transfer. This field contains the sequence number of the last byte of urgent data. It is possible to identify the urgent ...
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1answer
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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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1answer
35 views

Openvpn: no response from server in tcp handshake

I am attempting to connect to an openVPN server that I created on pfSense 2.2.3 by using tunnelblick on my Macbook. Whenever I attempt to connect using either OpenVPN version 2.3.6 or 2.3.7 (all that ...
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18 views

TCP traffic redirection

I am using an open source program called revinetd: revinetd.sourceforge.net On server side, revinet listens for incoming connections on a defined port to act as a relay server. Now, The server ...
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4 views

Why does my firefox send TCP packets even when idle? [migrated]

I run firefox on Debian. I've disabled all mumboo-jumboo healthy and crash report tracking. There is no TCP connection to any website, I leave firefox oppen at the 'create new tab' When I turn off ...
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1answer
47 views

Tcp connection breaking, too fast for serial?

I've been having real difficulties getting a tcp connection to work with my web server. I think the issue might have something to do with the speed or ordering of the packets as the connection seems ...
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0answers
43 views

Why would Windows 7 not complete this TCP handshake?

One of our customers is running Windows 7, and cannot reach some of our servers because it seems Windows 7 cannot complete a TCP handshake. Here's a packet trace to one our servers -- note that a SYN ...
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23 views

Spurious retransmission, Dup ACK and HTTP 408

I have a server which serves as sms gateway (using kannel) and have multiple client connecting to it, but recently this one client with their particular IP said that they can't send to my server and ...
15
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4answers
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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 ...
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0answers
45 views

Citrix NetScaler sending FIN, ACK for SSL VPN Clients

I realise that it's unlikely anyone here has a definite "Check this box to resolve this" answer, but I'm struggling with this issue and I'm hoping that someone with more knowledge than me can give me ...
0
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1answer
32 views

TCP Keepalive: Why does an idled ESTABLISHED connection end after 60 seconds, instead of tcp_keepalive_time?

I am investigating ways to mitigate a server against DoS-type attacks. In one scenario, I've opened several hundred TCP connections to my webserver. I do not send any data after the initial TCP ...
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12 views

Route only on output chain?

I have two machines A and B. I want to send iperf traffic from A to B, but first have it route through a userspace program on A. I did this with a tunneling device: therefore, I used the command ip ...
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1answer
5k 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 ...
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2answers
123 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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0answers
23 views

SYN/ACK not received by iperf client?

I have an application that essentially consists of four components A, B, C, D. A and B are on the same machine - B and C are separate machines. Traffic is generated by an iperf client on A with a ...