Hot answers tagged tcpip
Due to the way TCP/IP works, connections can not be closed immediately. Packets may arrive out of order or be retransmitted after the connection has been closed. CLOSE_WAIT indicates that the remote endpoint (other side of the connection) has closed the connection. TIME_WAIT indicates that local endpoint (this side) has closed the connection. The ...
The short answer An Internet spec called RFC 1918 reserved a few blocks of addresses for "private" networks, which is what you should use when you don't have enough public, routable IP addresses to go around. 192.168/16 was one of those blocks. The long answer (and then some) Back in the good old days, everything on the Internet got its own public, ...
It's not MS it is the ISOC ;-) Have a look at reserved IP address RFC 5735 under special use IPv4: here 169.254.0.0/16 - This is the "link local" block. As described in [RFC3927], it is allocated for communication between hosts on a single link. Hosts obtain these addresses by auto-configuration, such as when a DHCP server cannot be ...
Yes, there is a benefit to using IPv6 at home. The main one is education, i.e. you will gain experience at administering an IPv6 network that you can put on your resume. In about two years from now, sometime in 2011, the world will run out of IPv4 addresses and there will be a surge in demand for IPv6 networking, and that includes a demand for people ...
Because www.google.com is a lot easier to remember than 188.8.131.52? It also adds transparency to a services location. You can move both geographically and between IP blocks and the rest of the world doesn't have to be notified of that change to continue using your service.
For Windows 7, Windows Vista and Windows XP, the MTU for various interfaces is available from Windows itself using netsh. Windows 7, Windows Vista To show current MTU on Windows 7 or Windows Vista, from a command prompt: C:\Users\Ian>netsh interface ipv6 show subinterfaces MTU MediaSenseState Bytes In Bytes Out Interface ---------- ------...
The use of 169.x.x.x addresses are defined within a standard colloquially known as APIPA - Automatic Private IP Addressing. In a nutshell, if a network device has not been assigned a fixed (static) address and cannot obtain one by asking (DHCP), the device says to itself, "Well, I'd better make up an address of my own so I can communicate on this network", ...
If you are on a Windows machine, open a command box (Start...Run...cmd), ping the target machine so you have made contact with it, and then issue the command arp -a to view your local ARP table, which will list IP addresses and their corresponding MAC addresses, e.g., C:\Users\L3K> arp -a Interface: 192.168.200.128 --- 0xb Internet Address ...
Although everybody else suggests that DNS is not necessary for the internet to work, I disagree. DNS is not necessary for an IP based network to work but for the Internet as we know it today it is absolutely necessary!!
A port isn't open if something isn't listening for a connection on it. The reason it is bad form to have all ports open to everywhere is that it exposes those services that are listening on those ports to exploits. That is why firewalls exist, to limit what is allowed to connect to certain ports, to reduce the surface area exposed by services. EDIT To ...
You may be thinking of number of ports. There are 65536 ports available in the TCP in the current versions of IPv4. This is not just a Linux limitation, its part of the protocol. Your IP address identifies your machine, and the port identifies a program on your machine. But, the number of connections isn't limited by that. A connection consists of 5 ...
In IPv4: Nope. They will see the MAC of the device which forwarded the packet to the server, likely their border router. In IPv6, the 64 bit "host" part of the full 128 bit address is often automatically generated from the MAC address, and hence might be visible to the server one connects to. See also How to avoid exposing my MAC address when using IPv6?
Basically the "WAIT" states mean that one side closed the connection but the final confirmation of the close is pending. See e.g. this diagram of TCP states for details: http://www.jxos.org/Projects/TCP/tcpstate.html
It wraps around going to 0. According to RFC 793: It is essential to remember that the actual sequence number space is finite, though very large. This space ranges from 0 to 2**32 - 1. Since the space is finite, all arithmetic dealing with sequence numbers must be performed modulo 2**32. This unsigned arithmetic ...
I use it to be able to reach all my machines from outside without doing anything special. You could also use the improved multicast support to stream data in a much more efficient way. IPv6 also removes a checksum so you could perhaps notice a small improvement in performance, but most likely not. I try to use IPv6 whenever possible, mostly because it's a ...
One word: Netcat Netcat is the go-to tool for this sort of thing. You can thrash whatever port you choose with UDP packets with something like: nc -u host.example.com 53 < /dev/random (53 is your port number) Or you can send an actual file, or tell it to bind that port and listen as a service, or whatever you like.
Does the sequence number wrap around and become 0? Yes. All the details can be found in the TCP Specification RFC 793 - Transmission Control Protocol. Sequence Numbers It is essential to remember that the actual sequence number space is finite, though very large. This space ranges from 0 to 232 - 1. Since the space is finite, all arithmetic ...
The Windows Sysinternals Suite contains a tool called TcpView. TcpView will show you all of the connections on your machine similar to netstat. It will also allow you to close the connection or kill the process hosting the connection.
Check out TCPView, which is a GUI to do this stuff: http://technet.microsoft.com/en-us/sysinternals/bb897437.aspx
To answer your question. 127.0.0.1 is not just a different ip address to the machine ip address, it's a different interface as well. 127.0.0.1 should not be seen on the local network. It's a special internal IP address for the loopback adapter. x.x.x.x will be your ethernet card. by the way 'localhost' is simply an entry in your hosts file that points ...
The TCP connection limit is not enforced, but it may be bound by legal agreement to not permit more than 10 clients. See this from Microsoft: Inbound connections limit in Windows XP In a command prompt type: net config server This shows max allowed logged on users, and max open files per session
One alternative is the use of the lsof utility; specifically, lsof -i 4tcp will list all processes with some sort of TCP IPv4 network sockets open. The manpage of lsof will provide you with detailed information on how to use the utility and how to interpret the output.
It is a private block of IPs that aren't allowed to be routed on the public Internet and are reserved for internal use to be NATed to the outside world. The document that defines this is RFC 1918, which is enforced by IANA. The blocks of private-use IPv4 addresses are: 10.0.0.0 /8 (any address beginning with 10.x.x.x) 192.168.0.0 /16 (any address ...
The TCP protocol guarantees accurate delivery regardless of underlying mechanisms. There is no guarantee that every protocol that it might run over will do any sort of integrity checking. SLIP, for example, has no error detection.
Historical reasons. From the ground up unix/linux has always been about the network. Whereas MS-DOS/Windows bolted the network on as an afterthought, initially with Windows own 'NetBIOS' rather than TCPIP. Only when Netscape came along was it necessary for Microsoft to install a TCPIP stack and acknowledge the presence of the Internet. Before then you had ...
We say TCP segment is the protocol data unit which consists a TCP header and an application data piece (packet) which comes from the (upper) Application Layer. Transport layer data is generally named as segment and network layer data unit is named as datagram but when we use UDP as transport layer protocol we don't say UDP segment, instead, we say UDP ...
You may enable packet forwarding by entering sudo sysctl -w net.inet.ip.forwarding=1 into the Terminal.
The command arping comes with the iputils package on linux. Specify an ip address to ping and it returns the MAC address, even across switches and subnets on the LAN (at least it does on our LAN). # arping -c 1 -I eth0 10.100.10.11 ARPING 10.100.10.11 from 10.100.10.25 eth0 Unicast reply from 10.100.10.11 [00:22:68:88:F3:90] 0.594ms Sent 1 probes (1 ...
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