Permanent adapter having modulation and demodulation means for connecting networks

Claim 1

A terminal adapter, having modulation means and demodulation means, for connecting a LAN and a WAN on the basis of an Internet standard protocol describing a procedure of communication as well as terminating a line service and providing data transmission to a terminal system, said terminal adapter comprising: extraction means for extracting, from packets constituted by received data as an output of said demodulation means and transmitted data as an input to said modulation means, a simple network management protocol message indicating said Internet standard network control protocol, said extraction means including means for extracting from said packets of transmitted and received data, source and destination protocol addresses indicate of logical addresses for recognizing a host in said Internet; wherein said extraction means further includes means for checking a protocol field in each of said packets to determine if said checked protocol field meets a predetermined condition and, if said checked protocol field meets a first predetermined condition, checking source and destination port numbers, and extracting, if said checked source and destination port numbers meet a second predetermined condition, source and destination Internet protocol addresses; and network control means for performing network control according to said simple network management protocol message and performing network control according to signals obtained from said modulation and demodulation means.