TCP and IP are two important protocols used in networking today. Due to their importance, the Internet Protocol Suite is also commonly known as "TCP/IP"

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Connection Timeout Issues - Solaris 11 SPARC

We're currently running some performance tests using Solaris 11 (SPARC) on some large hardware. The tests, which consist of sending SOAP requests (50kb per request), are running well up until we get ...
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5answers
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How does IPv4 Subnetting Work?

This is a Canonical Question about IPv4 Subnets. Related: How does IPv6 subnetting work and how does it differ from IPv4 subnetting? How does Subnetting Work, and How do you do it ...
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1answer
839 views

Multiple Homed Windows 2008 Server / Windows 7 Client

I have a small Windows 2008 network, with some Windows 7 clients. The clients are both laptops with docking stations and I would like them to communicate with the Windows 2008 server (for filesharing) ...
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11answers
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What is the difference between UDP and TCP?

My router has two protocols (and a "both" option) that I can select when setting up port forwarding: UDP and TCP. What is the difference between these two protocols and when would you select one over ...
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1answer
1k views

Diagnosing packet loss / high latency in Ubuntu

We have a Linux box (Ubuntu 12.04) running Nginx (1.5.2), which acts as a reverse proxy/load balancer to some Tornado and Apache hosts. The upstream servers are physically and logically close (same ...
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2answers
67 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 ...
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1answer
115 views

Port forward remote desktop without a gateway over 3G modem router [closed]

I'm trying to connect from a laptop, through a VPN, and a 3G modem/router, to a remote PC / computer. PC (192.168.1.33) | 3G Modem (192.168.1.22) | [3G internet, connecting to VPN] | ...
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2answers
40 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?
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2answers
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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 ...
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6answers
861 views

TCP Sessions and IP Changes

What happens to a TCP session when the IP of a client changes? I did a simple test of having netcat listen on a port, and connecting to that port from a client machine. I then changed the IP of ...
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4answers
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Running lsof -i shows a lot of connections in CLOSE_WAIT ? Should I worry

So I am running lsof -i | wc -l periodically and it is telling me that out of 420 lines, between 240 and 255 are in CLOSE_WAIT state. How does TCP connections enter this state ? Should I be worried ...
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2answers
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What do all the settings in the Advanced TCP/IP Properties DNS Tab Mean?

Can someone explain TCT/IP > Properties > Advanced > 'DNS' tab please? I know what DNS, primary DNS suffix and DNS suffix are, but this tab has some confusing properties.
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4answers
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How is the MTU is 65535 in UDP but ethernet does not allow frame size more than 1500 bytes

I am using a fast ethernet of 100 Mbps, whose frame size is less than 1500 bytes (1472 bytes for payload as per my textbook). In that, I was able to send and receive a UDP packet of message size 65507 ...
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1answer
55 views

How to compare 2 TCP/IP stacks or implementations? [closed]

I have to recycle an old machine into a networking node for managing TCP/IP connections and PPP protocols ( basically a DSL connection ); I'm not asking for something more than this, all the tasks ...
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1answer
2k views

What else does “netsh int ip reset” do?

According to this KB article when you run the "netsh int ip reset" command, all it does is to reset the content of two registry keys: SYSTEM\CurrentControlSet\Services\Tcpip\Parameters\ ...
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7answers
3k views

How to capture postscript output via TCP/IP? (for testing purposes)

We have a propriety system that talks to various printers across multiple sites via TCP/IP. The system only outputs Postscript, which obviously sends via TCP/IP. I'm really wondering is there any kind ...
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1answer
834 views

TCP/IP performance tuning under KVM/Qemu

With more and more companies switching to public cloud services, I'm curious what you guys' thoughts are on TCP/IP tuning in the cloud. Is it worth bothering with? Given that you don't have access to ...
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1answer
119 views

TCP works for a while, then fails, why?

This comes from an implementation of OpenStack, and we have a fix, but I don't understand why we need this fix. My machine has an ip of 192.168.20.45 My default gateway (pfsense) has an ip of ...
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2answers
3k views

Slow data transfer between Server 2012 and Windows XP/7 Clients

I've installed a new Dell PowerEdge R720 server at a small company which eight workstations. It is running Windows Server 2012 Standard. I've then installed Hyper-V (role) onto the server and created ...
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2answers
3k views

Specifying a preferred route when there are multiple links to same network

I have a server with multiple interfaces and IP addresses on the same network. I would like for non-iSCSI traffic to exclusively use one of the interfaces, and for iSCSI traffic to exclusively use the ...
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0answers
110 views

Windows Server 2008 Enterprise - Print Server Role - TCP/IP Print Server Service Won't Start

I have a few Windows Server 2008 Enterprise edition Servers running Printer Server Roles. On these servers there are two system services: Print Spooler and TCP/IP Print Server (LPDSVC). The TCP/IP ...
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1answer
133 views

Host doesn't send ACK-SYN packets for transparent proxy

I am setting up a transparent proxy using haproxy, the setup works without the 'source 0.0.0.0 usesrc client' line. When I add that line in, the endpoint is called from the original client's ip ...
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0answers
100 views

Lots of packets pruned from receive queue because of socket buffer overrun - reason to worry?

I know this question has been asked before, but maybe not in this particular context: I have a setup with a couple of MS2008R2 HyperVisor servers running a number of Ubuntu guests. Our webproxy runs ...
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2answers
308 views

Can you use WMI to determine if a connection gets its DNS servers from DHCP?

The DNS server search order for a network interface can be read from Win32_NetworkAdapterConfiguration like this in Powershell, or programmatically using .Net ManagementObjects: > $NICs = ...
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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), ...
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Printer lpd daemon refuses print job if a command's new-line sent separately — bug?

I'm encountering some printer LPD daemons which work fine if the new-line is sent in the same packet as the command, but break if the new-line is sent in a separate packet. Is that a bug in these ...
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1answer
73 views

TCP client and server work for X times but hang after that

I'm a software engineer, but I think my problem needs a network engineer... For the software side of things, have a look at my Stack Overflow question: ...
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1answer
632 views

HTTP, TCP, UDP and connectionless

I am a bit confused with HTTP lately. Some facts are that TCP can operate connection orientated or connectionless, this I understand. TCP though is connection-oriented while UDP is connectionless ...
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1answer
406 views

Long TCP/IP Connect time (20-40s) with Apache 2.4, mod_proxy_ajp, Tomcat 7.0.39 running on Windows Server 2008 R2

The initial connection to an Apache HTTP Server is taking a very long time (20-40s), but the subsequent connection is very fast (<50ms). I use Apache HTTP Server as a load balancer using ...
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2answers
374 views

List of TCP & UDP ports known to be used by malware, etc [closed]

Where can I find a regularly updated, downloadable list of TCP & UDP ports that are known to be commonly used by malware, trojans, etc.? This is for import into an IT asset management system to ...
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1answer
2k views

xt_TCPMSS: bad length messages

I'm getting loads of messages like: Jun 23 10:24:20 awakening kernel: [ 1691.596823] xt_TCPMSS: bad length (1492 bytes) Jun 23 10:24:21 awakening kernel: [ 1692.663362] xt_TCPMSS: bad length (1448 ...
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1answer
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Firewall Connections fail to open under load

Problem : During High load , our applications are encountering errors : java.net.connection Time out. After some investigation , we found out that it was Firewall the root cause, but still don't know ...
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How do I view the TCP Send and Receive Queue sizes on Windows?

Linux netstat shows send and receive queue sizes. How do I get this info under Windows, specifically Server 2003?
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78 views

Could the IPG parameter in Robocopy cause TCP/IP packet problems if it is too high?

I need to throttle a robocopy transfer to limit bandwidth usage. It is already set to 1500 (/IPG:1500). I would like to increase this IPG to around 2000 (or more) in order to lower even more the ...
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2answers
2k views

Windows Server 2008 R2 IP Address Binding order

How do I set the order of multiple IP addresses all bound to one ethernet interface?
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11answers
8k views

Why would you use IPv6 internally?

Of course, I realize the need to go to IPv6 out on the open Internet since we are running out of addresses, but I really don't understand why there is any need to use it on an internal network. I have ...
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2answers
182 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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0answers
920 views

How to know the source of certain TCP traffic on AIX

We have two AIX boxes, one for production system and another for testing. both systems are running ATM machine switches, where the ATM device is connected via TCP socket. we had an issue on ...
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1answer
168 views

ping -a sometimes returns host name and sometimes returns FQDN. Why? Does this mean DNS is corrupt somehow?

I have a Windows machine called abcd for example and it uses DHCP to receive an IP address (172.28.45.5 for example) When I perform ping -a 172.28.45.5 sometimes I receive abcd as the hostname. ...
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4answers
5k views

Diagnosing and debugging LAN congestion / connection issues

What are the top N tools / methodologies used to diagnose and repair network issues? Given a LAN, for example, where users are able to consistently ping an outside server, but any data intensive ...
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Drop in HAproxy traffic with increase in connections

We have an intermittent issue that involves a severe drop in network traffic (both IN and OUT) on our HAProxy load balancer. It happens a couple times a day. HAProxy is configured to limit requests ...
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1answer
149 views

Server with two default gateways won't listen on the second gateway

I am testing a redundant internet connection setup that works like this - I have a network segment, 192.168.80.X It has two gateways - 192.168.80.1 - a FW connected to a frame relay line ...
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2answers
681 views

How to globally limit total number of TCP connections with iptables?

I'm having quite a difficult time figuring out how to REJECT both inbound and outbound connections from a machine with iptables once the total number of TCP connections hits a global maximum without ...
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2answers
795 views

Linux server resend SYN ACK

I am troubleshooting a connection timeout problem between two Linux boxes, where it seems the ACK to SYN-ACK was lost on the server's stack. The tcpdump is done on the server side. The client got ...
3
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2answers
3k views

ESXi network setup for isolated internal virtual machines

Using ESXi v5.1 and vSphere, my networking is setup like so: One standard Switch: vSwitch0 vSwitch0 has one uplink physical adapter (Internet connected) vSwitch0 VM Network has 3 virtual machines ...
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1answer
326 views

Where to find WINS IP address in registry?

I have been writting a powershell script to remotely dump the TCPIP information from the registry of machines in my Windows Domain. I was able to dump the default gateway, subnet mask, DHCP server ...
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1answer
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Need help routing Cisco network- IP routing [closed]

In the above network, can you help me configure routes so the computers on the left can see the computers on the right, and vice versa? I know the syntax of the command is ip route {network ...
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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
148 views

Do keepalives to socket connections exist?

Pre briefing: Although my question is broad on purpose, I am dealing with nginx connecting to php-fpm (fcgi), which is served via a local socket (/tmp/somesocket.socket). Nginx has a setting to ...
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1answer
236 views

is it possible to use ms loop back adapter to setup local vlan

Is it possible to use Microsoft Loop back adapter to set up Lan connection between two computer which is logically isolated from the main network? 1st computer: has a regular ip stack 192.168.1.x ...