5-10 Netopia ISDN Modem User’s Guide
B Channels
The B Channels area lets you select options for your two ISDN
B channels.
Data Rate. Choose the B-channel data rate you want from the Data Rate pop-up menu. The data rate options are 56 Kbps and 64 Kbps (the two data rates ISDN supports). Not all telephone services support the 64 Kbps data rate. Select the data rate used by your telephone company.
Protocol. The Protocol pop-up menu lets you choose the transport protocol you want. The protocol options are QuickSelect, Async/Sync PPP Convert, and V.120. In most cases, you should use the QuickSelect protocol. QuickSelect allows the Netopia ISDN Modem to automatically detect the protocol in use on the ISDN line and adapt to that protocol. Also, when QuickSelect is active, the modem converts asynchronous Point-to-Point (PPP) information into synchronous (HDLC-based) PPP information. If you select either the Async/Sync PPP Convert or V.120 protocol, the Netopia ISDN Modem will only use the selected protocol.
Enable Compression. (This option is only available for the Netopia ISDN Modem Model 412.) Check the Enable Compression box to turn on data compression. Data compression is a method of reducing the size of data without losing any of the information. Models 412 and 612 of the Netopia ISDN Modem automatically use Stac data compression to compress data to improve data transfer times. To take advantage of data compression, the device you are dialing into must also support data compression. Note that the Netopia ISDN Modem’s data compression will not be used if data compression is in use in your communications application. For more information about data compression, see the “Using data compression” section on page 6-3.
V.120 Max Frame Size. The V.120 Max Frame Size pop-up menu lets you specify the maximum number of bytes in a V.120 frame. V.120 is an alternative transport protocol to PPP. The available frame sizes range from 240 to 256 bytes. Leave this set at 256 unless your system administrator or Internet Service Provider (ISP) instructs you to specify a different value.
