e913ce18fc There are undoubtedly other places, where modifications must be done. The local computer (192.168.1.100) sends the packet as coming from 192.168.1.100, but the server (192.168.1.2) receives it as coming from 203.0.113.1. This article focuses too much on specific examples without clearly discussing its abstract general subject. The router is also connected to the Internet with a "public" address assigned by an Internet service provider. "RFC 4787 Network Address Translation (NAT) Behavioral Requirements for Unicast UDP" (text). ^ superuser.com ^ "NAT Loopback Routers - OpenSim". The major transport layer protocols, TCP and UDP, have a checksum that covers all the data they carry, as well as the TCP/UDP header, plus a "pseudo-header" that contains the source and destination IP addresses of the packet carrying the TCP/UDP header.
Information technology portal . Usually this is done because it is desired to set up a direct communications path (either to save the cost of taking the data via a server or to improve performance) between two clients both of which are behind separate NATs. Long-term and short-term solutions to these problems are being developed. Since both use a one's complement sum, it is sufficient to calculate the arithmetic difference between the before-translation and after- translation addresses and add this to the checksum. (See RFC 1597 .) This address could then be used for internets with no connection to the Internet. ^ Network Protocols Handbook (2 ed.). RFC 1631 Network Address Translator May 1994 4. PAT (Port Address Translation) resolves conflicts that would arise through two different hosts using the same source port number to establish unique connections at the same time. 3.3 Header Manipulations In addition to modifying the IP address, NAT must modify the IP checksum and the TCP checksum.