If the checksum is zero, it means that checksum was not calculated by the sender and can be ignored. In this case, any foreign socket is acceptable as long as the local sockets match.
If the computer has been moved around, the Ethernet card may come unseated from the expansion slot on the motherboard. UP - receive urgent pointer IRS - initial receive sequence number [Page 19] September Transmission Control Protocol Functional Specification The following diagrams may help to relate some of these variables to the sequence space.
The rest of this [Page 2] September Transmission Control Protocol Introduction section offers a very brief view of the protocol interfaces and operation. If any question arises about the correct specification of a protocol, please refer to the actual standards defining RFC.
A reset is valid if its sequence number is in the window. In particular, SYNs addressed to a non-existent connection are rejected by this means. If a segment contains an odd number of header and text octets to be checksummed, the last octet is padded on the right with zeros to form a 16 bit word for checksum purposes.
This is used at the end of all options, not the end of each option, and need only be used if the end of the options would not otherwise coincide with the end of the TCP header.
When the computer is moved to a different part of an internet, its IP address must be changed. The content of the route table is defined by the network administrator. These services can then be accessed through the known addresses.
Thus, all communication is viewed as inter-process communication. The IP address must be unique for an internet.