Tagged Questions

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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2answers
98 views

TCP Python Server

I have a question regarding connection reliability running a tcp server from an ec2 instance. We are currently serving mobile customers around the world from the Oregon region using a c3.4xl ec2 ...
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1answer
535 views

TCP Sequence & Acknowledgment numbers

I have looked through other questions on here involving the relevant topics, but I am still not clear on this. I have just been reading this explanation of TCP sequence & acknowledgment numbers. ...
0
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2answers
181 views

apache2 keepalive and opening a tcp connection

An IP packet contains a payload, such as HTTP information, which in turn contains html information. An IP packet is encapsulated into a TCP segment, which detects problems in transmission over ...
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3answers
167 views

Is TCP header the same as TCP segment?

So, is a TCP header actually the same thing as a TCP segment? I was reading this page, where it reads near the end that: Even though it might seem they are, in most cases, when referring to the ...
-1
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1answer
268 views

Connect to sphinx on remote server

I recently moved sphinx onto the same server as our db so our architecture is: File Server that hosts our web app DB server w/ Sphinx instance (searchd) When I try to connect to sphinx at ...
0
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2answers
151 views

Debugging slow transfer rate from server

I'm trying to explain this as simple but documented as possible. This is not exclusive to this server or my current ISP. I've seen the same exact issue over the years while being with different ISPs ...
1
vote
1answer
144 views

Increase number of connections per socket

How do I increase the number of connections each socket can accept? I know that you can increase the total number of connections using: # sysctl kern.ipc.somaxconn=4096 But each connection is then ...
2
votes
1answer
334 views

TCP Window size increases drastically and sender don't send until the receive buffer is not empty

I have a download stream over TCP in an application (running on Win2k12). The problem is that the connection gets closed by the sender because it times out. I used wireshark to see what happens on ...
0
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2answers
134 views

FreeBSD Established Connections Maxing out at 300

We've previously had issues in our environment where it seemed we were reaching FreeBSDs max connection limit. We took action demonstrated by http://nginx.org/en/docs/freebsd_tuning.html and bumped up ...
0
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0answers
19 views

Debian as TCP-Server for Serial Port redirecting [duplicate]

I want to start a tcp listener on debian. One client should be able to connect and should get inputs of serial port in the tcp connection. And when the client sends data through the tcp socket the ...
0
votes
1answer
679 views

TCP Zero windows size and full windows size

The problem that we are facing is that some of the http connection have response time > 60s (about 5%). I discover that the problem should between the web server and loadbalancer. Here is my finding, ...
1
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0answers
362 views

What does “connections reset due to unexpected data” in netstat -s mean

I'm running a memcached server under heavy load from multiple web servers. While investigating some odd app level behaviour, we spotted that netstat -s on the memcached box was showing a lot of ...
2
votes
0answers
237 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 ...
0
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0answers
262 views

Keep doing TCP Retransmission with ACK, PSH

here is my situation: I got two servers, a loadbalancer (prowered by softlayer) and a web server running apache 2.2 and php 5.4. My web application only serve android mobile device. I was tested 2 set ...
0
votes
2answers
35 views

Distributed LAMP vs DB and Web Server same box

We have a very read heavy semantic web (RDF) application which is RHEL 5/Apache 2.2.3/Tomcat 6/Java 6 on one Server, and MySQL 5.1 on another. Apache and MySQL are backported Red Hat repo stuff, so ...
0
votes
0answers
77 views

Reproduce netperf TCP_RR test with NTttcp

The documentation of NTttcp being hard to find and to understand, how can I mimic the behavior of the TCP_RR netperf test with NTttcp?
0
votes
1answer
95 views

Linux tool to show connections/s?

Is there a tool/command to show connections per sec? I've tried a few iptraf and iftop but I can't see anything about connection rates.
1
vote
1answer
78 views

TCP timestamps field is in the future

I have a server sending TCP packets. I noticed, with wireshark, that my packets in the Timestamp optional field look like Timestamps: TSval 2552765291, TSecr 3858527953 The TSval is the value my ...
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0answers
279 views

iperf test in reverse direction gives different result

I used iperf to measure the max throughput for TCP connection between two ubuntu machines. Both the machines were directly connected be means of a 1Gbps cable. When I performed iperf tests i obtained ...
0
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1answer
144 views

Show real TCP/IP addresses behind Nginx environment

When i execute the command netstat -atun | awk '{print $5}' | cut -d: -f1 | sed -e '/^$/d' |sort | uniq -c | sort -n I see high number of connection assigned to server ip I want to see the real ...
-1
votes
1answer
67 views

Open file count keeps increasing forever

I'm experiencing issues with the number of files opened increasing over time. If I run my server for about few hours, it'll no more accept any connections. The limit was 1024. I've increased the limit ...
1
vote
1answer
1k views

Windows Server 2008 TCP connections limit

I run my own game server made in .net 4.5 on a Windows Web Server 2008 VPS. I have done some research on a problem I have. My app doesn't accept clients, if there are already 1000 clients connected. ...
8
votes
1answer
354 views

TCP packet being retransmitted 7 times when sysctl tcp_retries1 is set to 3 - why?

Ubuntu 12.04 I am trying to better understand how many times TCP will attempt to retransmit a packet when it does not receive confirmation the destination received it. After reading the tcp man page ...
2
votes
0answers
300 views

No response to some SYN packets when timestamps are enabled

I have a TCP server listening on a machine ("the server") running Ubuntu 12.04.3 (kernel 3.8.0-31-generic). It receives connections from 2 different client machines. Machine A is running Ubuntu ...
2
votes
3answers
481 views

Windows Server TCP sockets random disconnect: how to reproduce?

We rented 10 Windows servers from a large provider in Europe. They all work as expected. One server suddenly crashed and customer care found that both disks were broken. They replaced disks and also ...
1
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0answers
203 views

Linux MIPS box: ICMP (ping) works, but TCP does not - how to fix it?

I'm trying to set up MIPS Linux box network. Here is it's configuration: ~ # ifconfig eth0 Link encap:Ethernet HWaddr CC:5D:4E:FF:45:7F inet addr:192.168.0.2 Bcast:192.168.0.255 ...
1
vote
1answer
140 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 ...
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0answers
136 views

How can I replay a TCP stream to my client

I need to do some validation testing of a new feed handler I have made. I have some pcap data that I captured from the production network and I would like to have my development feed handler connect ...
1
vote
1answer
65 views

TCP echo server security [closed]

I am setting up a Linux server similar to a TCP echo server and am wondering about security issues I should be concerned about. This will be a bare bones Centos/KDE server with no additional files ...
-6
votes
1answer
57 views

What is the incentive to operate a TCP/IP node? [closed]

I mean, why does anybody relay messages to other nodes? Why are these eleven good people below helping me send my bytes to their destination? traceroute to stackoverflow.com (198.252.206.140), ...
3
votes
1answer
62 views

Default TCP connection backlog value in Windows

Which is the default connection backlog value for TCP in Windows? I have tried to find it but no luck. Cheers
5
votes
6answers
727 views

How can I find the total number of TCP connections for a given port and period of time by IP?

On a Linux system there are plenty of methods for listing the current TCP connections for a given port by connecting IP but: how can I count the total number of connections to a port per source IP for ...
4
votes
2answers
1k views

VMXNET3 performance on Linux on ESX 5.0

What kind of performance can I expect from VMXNET3 adapter when running two Linux guests on the same VMware ESX private network defined between those guests? I use VMXNET3 adapter for communicating ...
1
vote
0answers
77 views

TCP load balance authentication

Impala is a piece of Cloudera software which implements an ODBC driver on a desktop, which then connects directly to a Hadoop cluster. In our implementation, our Hadoop cluster sits behind a DMZ, in ...
0
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0answers
86 views

opensips sever running fine and UDP connection cannot register but TCP connections works fine

Im a newbie to opensips and Centos/Linux. Recently installed opensips sever which running smoothly on TCP connections, but users cannot register on UDP connections. here my Log, have a look. Feb 26 ...
0
votes
2answers
194 views

How to drop bogus tcp packets through iptables?

We are seeing the issue described here - http://archives.neohapsis.com/archives/bugtraq/2002-10/0266.html In brief, we need to drop bogus packets, such as with SYN+FIN flags set. I can drop this ...
0
votes
1answer
194 views

pushing apache2 past 1500 concurrent connections

I am trying to scale to 4000 concurrent connections on a ubuntu/apache box. It is 8 core / 64gb ram, so it is not hitting memory or cpu, or any resources for that matter. The problem is with ...
0
votes
1answer
136 views

How to view tcp connection errors in apache/ubuntu

I am load testing a ubuntu/apache2 server and after 500 concurrent connections my load testing software is telling me there are connection errors. The errors are not showing up in apache error log. ...
5
votes
1answer
132 views

Odd TCP termination sequence

While troubleshooting another thing, I've noticed an odd pattern of TCP closes. Packets: http://www.cloudshark.org/captures/7590ec4e6bef What's happening is that the last few packets of the close ...
1
vote
1answer
153 views

TCP and retransmission [closed]

I'm trying to understand how the transmission and ACK work in TCP. In this Figuure, when A retransmitt the seq 100 after he recive three duplikated ACK , B will answer with 121 ACK or 158 ACK ?
0
votes
1answer
110 views

Linux unfriendly IIS/ASP.NET :-) : Quick download on windows but slow on linux [closed]

This particular web site (gops.tay.be) serves objects quick if I try to request the page using windows, but I get them very slow if trying using linux. There is no difference if I use browser or curl: ...
1
vote
1answer
2k views

Why would a client send a RST packet as reply to a SYN,ACK?

I have a HTTP webservice where sometimes the connection setup fails in a strange way: client sends a SYN packet server sends a SYN,ACK reply client responds with RST In which situations could a ...
2
votes
1answer
160 views

Find number of TCP bytes transmitted

I have rhel4 and rhel6 hosts. I can use netstat -s to see information on the number of segments sent/received. I can use ifconfig to see the number of bytes sent/received on a given interface (for ...
1
vote
0answers
125 views

What could be the cause for outbound TCP/IP traffic beeing blocked while ICMP is still working?

On a Windows Server 2003 there is a strange issue. Every 6 hours the server don't accept outbound TCP/IP traffic while inbound traffic working fine. If the problem occurs I can connect with RDP to ...
0
votes
1answer
105 views

How do I know that my TCP connection is safe from the Firewalls/NAT?

Being on the Azure cloud, I found that the firewalls there drop connections between the Web server and the database quite often. Mostly when there was some inactivity, I think something between 5 and ...
3
votes
1answer
1k views

Reverse proxy for mixed tcp, udp, and http services

I'm building an architecture that will be hosting various services which individually maybe listening on a variable number of ports that could be mixed protocols. I want to map these services to ...
0
votes
1answer
1k views

HTTP 502 Bad Gateway error response

I'm debugging an issue and running out of ideas. I have a server with SharePoint code hosted at port 8080 and a WCF REST service at port 8801. From another machine on the domain, I can connect to the ...
0
votes
0answers
293 views

XenServer open vSwitch performance downgrade

I'm trying to capture part of an inter hypervisor traffic between 2 virtual machines running over XenServer 6.2. I want to mirror some TCP sessions to a 3rd virtual machine with minimum affect to the ...
0
votes
0answers
63 views

Throughput decreases after MTU 5000

I am trying to test throughput between two computers directly connected through 1 Gb and testing with iperf. I am getting a throughput around 980Mbps when MTU is between 5000 and 5050, however it ...
1
vote
1answer
316 views

TCP Duplicate Acks are received

We are trying to get to maximum throughput on ftp over an LTE link. When we are downloading a file using ftp some duplicate ACKs are seen. Reading about the duplicate ACKs, I gather they are sent so ...