Transmission Control Protocol (TCP) and Internet Protocol (IP) provide end-to-end connectivity specifying how data should be formatted, addressed, transmitted, routed and received at the destination.

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39
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2answers
84k views

What are CLOSE_WAIT and TIME_WAIT states?

When I do netstat -a on my Windows machine, I get a listing of the ports with one of the four states: LISTENING CLOSE_WAIT TIME_WAIT ESTABLISHED What do CLOSE_WAIT and TIME_WAIT mean/indicate?
28
votes
7answers
30k views

Is there any benefit to using IPv6 on my home network?

I know that IPv6 is the future because there is only 4 billion IPv4 address, but on a home network, you are not going to have 4 billion users. So are there any other benefits that would make IPv6 on a ...
25
votes
3answers
47k views

Why is Windows' default IP address 169.xx.xx.xx?

My Windows system got an 169.xx.xx.xx IP address the other day, and I fixed the issue, but why did Microsoft chose this address as the default? Why not 1.xx.xx.xx or 255.xx.xx.xx? Did one guy at ...
17
votes
5answers
5k views

Why are home networks prefixed with 192.168?

Why are home networks prefixed with 192.168 ? Why those numbers? For some historical reasons?
16
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8answers
72k views

How to find the MAC address of a remote computer?

I know the IP address of a host on my own LAN. Using that, how can I find its MAC address (without having to physically access it)?
12
votes
7answers
11k views

Why is it bad to have open ports?

Here's something that has always baffled me. Why is it bad to have open ports on your computer? Assuming you don't have a virus on your computer or some other program listening to a port that may ...
11
votes
3answers
135k views

How to reinstall the TCP/IP protocol driver on Windows 7?

How to reinstall the TCP/IP protocol driver on Windows 7?
11
votes
1answer
522 views

Determining what process has bound a port (without listening) on Windows

If I want to find out what process is listening on what socket, I can use netstat/TCPview and will immediately see it. However, it is possible to bind to an address without listening. If this is done, ...
10
votes
18answers
8k views

Can the Internet work without DNS?

If we have an IP-based system of identifying nodes on the Internet why is there a need for DNS?
10
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2answers
4k views

On the Performance of TCP implementations of Linux and Windows

As I understand the implementation of TCP stack in windows and Linux are different. Windows uses a congestion control algorithm known as the TCP Reno while Linux uses Cubic. How do the 2 protocols ...
9
votes
5answers
51k views

How to tell what MTU is being used in Windows XP

I'm suffering from a really weird problem where I randomly get "The connection to the server was reset" errors when trying to access web pages (HTTP error 12031 according to the Windows network ...
8
votes
1answer
2k views

Why has Microsoft never implemented a loopback interface in Windows?

First things first: I know that you can install a sort-of-a Loopback Adapter in Windows. But what I really found strange is that there exists nothing like lo on Windows. At all. From The missing ...
7
votes
12answers
5k views

Why is IP to MAC address translation needed?

On networks that use the TCP/IP protocol, why is the IP address translated into a MAC address? I mean, when every device knows its IP, why further use the MAC address and not use the IP number as ...
7
votes
5answers
11k views

Does Windows XP only allow 10 inbound TCP/IP connections at any one time?

I tried to connect 40 clients to a webservice that is on Windows XP and I get no connection. Are the inbound TCP/IP connections on Windows XP limited to 10 at any one time?
7
votes
1answer
4k views

Is your MAC address revealed when you hit up a website?

When you hit up a site, such as cnn.com, does the TCP/IP packet contain the MAC address of your network card? Could cnn.com theoretically record my MAC address?
7
votes
2answers
8k views

What is “Disable class based route addition” good for?

In the advanced TCP/IP settings of a VPN connection, i found a checkbox labeled with "Disable class based route addition". The checkbox is only enabled as long as "Use default gateway on remote ...
7
votes
1answer
695 views

Tcpip error: Request failed due to all such ports being in use

Today my machine stopped being able to access the internet. I can still access some local network resources. When I looked in the error log I saw following tcpip warning: A request to allocate an ...
6
votes
2answers
7k views

How to generate UDP packet

I want to generate UDP packet to test a program, something equivalent to using telnet to test TCP port (Can telnet generate UDP packet?) How can I do this?
6
votes
3answers
7k views

Difference between localhost and the ip address

If bind a socket in Python to localhost,8200 this is accessible via http://localhost:8200/. but not http://x.x.x.x:8200/ If bind a socket in Python to x.x.x.x,8200, machinename,8200 this is ...
6
votes
1answer
110 views

If a major telco line is cut to a region of the world, is the “Internet” still available for sites served from within that region?

Can the Internet work independently within various regions of the world or are there safeguards in place that take down portions of the Internet-network (yes, I see the redundancy) when a major telco ...
6
votes
6answers
5k views

Why is my router not routing?

Starting a week and half ago my router stopped working with my cable modem. I went to sleep with it working and woke up with it not. I swapped in another router and am still having issues; I was ...
6
votes
1answer
100 views

Occasionally unable to connect to single web page

Occasionally, one of my users will be unable to connect to our web-based email (simple timeout, page cannot be displayed, errors). The problem persists for days (and between reboots) then eventually ...
5
votes
3answers
600 views

Why is a network ID not needed to connect to an IP address?

I know how IP basically works, and knows that an IP address composed of a network ID portion and a host ID portion, but when I type a IP address, say 8.8.8.8 into the web browser, I didn't supply any ...
5
votes
3answers
680 views

Multiple home routers

Suppose I have the following configuration: Router A: WAN port connected to the Internet, LAN = 192.168.1.0/24 Computer A: Connected to router A as 192.168.1.101 Router B: WAN port connected to ...
5
votes
7answers
139k views

Windows 7: How to solve IPv6 “No network access” problem?

I'm tearing my hair out on this one. Basically I need IPv6 to work on a Windows 7 (Home Premium) Dell laptop and it isn't. I have the wireless networking all working but if I click on the wireless ...
5
votes
2answers
2k views

Is there a tool to modify HTTP packet on the fly?

Wireshark is good, but it doesn't allow you to change the content of the packet. Is there a tool to do this job?
5
votes
2answers
779 views

Poor TCP performance over single connection, but not over multiple?

On two separate Dell machines, I seem to be having an annoying performance problem when downloading over a single connection. The one I've just tested this all on is a Dell Dimension 3000, XP SP3, P4 ...
4
votes
3answers
826 views

How to get started with TCP/IP v6?

Now and then there is "news" about that the IP numbers will run out in X years, and we must change to TCP/IP v6... And even though this crisis never really happens it has waken a question, how do ...
4
votes
2answers
26k views

How to kill a particular tcp connection in windows?

On Linux we can kill an Established TCP Connection using tcpkill command. For example, to drop all connection to/from a particular IP: tcpkill host ipaddr Or similary to kill all connection ...
4
votes
1answer
7k views

Is there a hard limit of 65536 open TCP connections per IP address on linux?

Is there a hard limit of 65536 open TCP connections per IP address on linux? I read somewhere that there was, but someone is asking for confirmation and i just can't find it. I seem to remember it ...
4
votes
3answers
10k views

Why a single(?) TCP packet gets split to multiple PDU units here?

Pic related: Why those segments are marked as separate packets (all Ack, Seq=509)? Why did a packet get split?
4
votes
1answer
352 views

Why does MacOSX try to resolve zero padded IP addresses as host names?

This one caused a friend some headache when setting up a switched internet connection which had zero padded IP addresses in the configuration paper like so: 192.168.019.254 No matter how he tried to ...
4
votes
1answer
10k views

Force socket close

Is it possible to close an established socket connection in Windows "manually" (e.g. using a command prompt tool)? I have several open sockets connected to a listening server, I can see them using ...
4
votes
2answers
55k views

How to check if TCP port 1723 and GRE protocol port 47 are blocked or not in windows 7?

I am trying to connect to a VPN Server (BestUKVPN) but im failing each time I try. I get the 691 error but the username and password are OK. I searched and I am told that the port 1723 or GRE protocol ...
4
votes
3answers
5k views

Windows keeps using a preferred DNS server?

I have trouble using Panera WiFi, and I finally tracked down the problem: Every time I reboot, Windows resets my TCP/IP settings for my wireless adapter to use a specific DNS server, instead of ...
4
votes
2answers
623 views

Is `ip` to supersede `ifconfig`

A friend of mine said that ip is supposed to be the successor of ifconfig and iwconfig — yet I found no Wikipedia article about it and have never seen anyone mention or recommend it online even though ...
4
votes
2answers
8k views

what is TCP Half Open Connection and TCP half closed connection

I am trying to understand what is the difference between TCP Half Open Connection and TCP Half closed connection can any one tell what exactly are they?
4
votes
1answer
792 views

How to ssh in the face of huge (25 second) latency?

I need to create an ssh connection between two Linux machines running Centos v5 but the latency could be as high as 25 seconds. I find that if I test something approaching this configuration ...
4
votes
2answers
266 views

Prevent a download to saturate all bandwidth on Linux

In Linux, a single download can use all available bandwidth, so that any other connection can't be started. (e.g. if I am downloading updates, I can't surf the web at the same time) Is there a way to ...
3
votes
2answers
558 views

TCP Checksum, why?

Why does TCP need a checksum, when lower layers do integrity checks anyways (like Ethernet CRC)?
3
votes
4answers
1k views

How do I rebuild the TCP/IP stack on XP?

Consider a computer has been hit with a spyware bomb and it has destroyed the internet connectivity in almost every way. (no ethernet, wireless, or dial-up) Because it would take forever to backup ...
3
votes
5answers
2k views

Editing the hosts file

I'm looking to edit the Windows TCP/IP hosts file (at c:\windows\system32\drivers\etc\hosts). I'm wondering, what is the best way to do this (on Windows XP)? Let's say that I want to redirect, say, ...
3
votes
1answer
420 views

why is my computer connecting to skynet? is it a virus or other type of malware?

i recently ran a "netstat" command on my windows xp system, and saw some connections to "Iron.Skynet". well Iron is my Computers Name, but ive not come across the name "Skynet" on my system before. ...
3
votes
1answer
3k views

How to enable “packet forwarding” in OS X

How is it possible to enable packet forwarding in Mac OS X? Google gives me tons of hints for Windows and Linux but not for OS X.
3
votes
2answers
1k views

What are ping packets made of?

What exactly are in the packets that are sent via the ping command? I was reading a Wikipedia article about magic numbers and saw this: DHCP packets use a "magic cookie" value of '63 82 53 63' ...
3
votes
2answers
2k views

Using localhost TCP/IP communication in a program - always safe?

I have an application which is separated to several parts (processes) communicating over TCP/IP, using a pre-defined port on localhost. Is this always safe? Can some kind of a firewall (corporate, ...
3
votes
3answers
11k views

Any free application to redirect serial communication to TCP/IP?

Please can anyone suggest a free application which creates virtual serial ports and any traffic on that port is redirected to given TCP/IP address?
3
votes
2answers
502 views

No route to host after changing interface to static ip

I installed a Linux (Ubuntu) server inside my home LAN, initially it's automatically configured to use DHCP interface. I'm connecting to this server from another computer using that server's hostname. ...
3
votes
1answer
2k views

Adding a second network card (dedicated connection to a network music streaming device) to a PC already on a home wireless network

I have a pretty normal home wireless network with a combined adsl modem/router which all my (Windows XP/Vista) computers use DHCP to connect wirelessly to and share resources among each other in a ...
3
votes
1answer
202 views

Why is the DNS setting part of Windows TCP/IP setting dialog? [closed]

The DNS servers setting has been part of the Windows TCP/IP setting dialog since the earliest version of Windows as far as I can remember (Windows 95). However, a host may have multiple network ...