3com Corporation

3com Corporaton

Daniel M Brennan

Cheng T Chen

Reginald P Best

Rajiv Bhatia

C Paul Douglas

Jyh-Ming J Wang

Suiling C Zhang

A LAN modem permits unambiguous routing for multiple workstations located on a LAN to each gain access through the LAN modem to any one of a number of different remote servers located on a number of different remote networks using a combination of public port number and public address of the workstation. There are instances where sessions are changed between the same workstation/server. This changing of sessions changes the public port numbers associated with each session, which destroys the above unambiguous routing, since the combination of a public destination IP address and a private destination port number is no longer the same unique value contained in an address translation table of the LAN modem. A four step hierarchical procedure is provided in which the LAN modem determines which workstation the packet is to be routed based upon value of fields stored in the network address translation (NAT) table or value of fields stored in a static table. The NAT table or static table entries are compared to the values of fields stored in the packet header.

Apparatus and methods for determining the correct workstation within a LAN for a LAN modem to route a packet

Apparatus for an improved ISDN terminal adapter (5) and accompanying methods for use therein. The adapter provides automatic ISDN switch detection, automatic SPID configuration, baud rate unblocking and automatic data compression. Specifically, the adapter automatically detects a type of ISDN switch (480) to which the adapter is connected by analyzing D-channel initialization messages which are received by the adapter from the switch as well as specific responses to ISDN messages sent by the adapter. The switch type value is then used, during SPID determination, in conjunction with a telephone area code of the user, to access an internal database (435) of predefined SPID formats, referenced in terms of particular telephone service areas and switch types, to access the possible SPID format(s) for the ISDN switch. Firmware (460) executing within the adapter, in conjunction with software executing within the DTE, forms one of more SPID(s) appropriate for the switch, queries the switch with each of these SPIDs to select and verify a correct SPID from those formed, and, if necessary, further refine and update the switch type previously determined.

Apparatus for an improved ISDN terminal adapter having automatic ISDN

Apparatus for an improved ISDN terminal adapter (5) and accompanying methods for use therein. The adapter provides automatic ISDN switch detection, automatic SPID configuration, baud rate unblocking and automatic data compression. Specifically, with respect to baud rate unblocking, the adapter detects instances of baud rate blocking, through excessive communication errors for a known input, and forces the adapter to relinquish its high speed setting and automatically return to autobaud operation but at a lower maximum speed.

Apparatus for an improved ISDN terminal adapter having baud rate

Apparatus for an improved ISDN terminal adapter having automatic SPID

Apparatus for an improved ISDN terminal adapter (5) and accompanying methods for use therein. The adapter provides automatic ISDN switch detection, automatic SPID configuration, baud rate unblocking and automatic data compression. Specifically, the adapter automatically provides B-channel data compression in the event the DTE is unwilling or unable to do so. Here, the adapter monitors negotiation, over an ISDN line, of a compression control protocol (CCP) between the DTE and its PPP peer (380). If the negotiations reveal that the DTE will not undertake compression, then the adapter will then automatically negotiate the protocol and thereafter, for the duration of a call, perform compression and decompression in lieu of the DTE.

System for ISDN terminal adapter DCE for automatically negotiating data

A data communication system referred to as an Asynchronous/Synchronous Converter is provided to facilitate the communications between a data terminal equipment (DTE) device using the asynchronous communication port, and a dial-up router located in a digital network. When running a dial-up TCP/IP program over the asynchronous port, DTEs use a protocol called Asynchronous Point-to-Point Protocol (Asychronous PPP). On the other hand, dial-up routers usually support Synchronous PPP. The data communication system of the invention connects the DTE to the digital network and ultimately to the dial-up router and provides two way conversion between Asynchronous PPP and Synchronous PPP that is transparent to both the DTE and the router. This two way conversion is enabled in part by the converter intercepting and storing certain link control protocol (LCP) packets and using data in those packets to effect a translation.

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Hillsdale, NJ, United States of America

Daniel M Brennan