Farallon Communications 612 - Manual (Page 87)

Advanced Features 6-3
Using data compression
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.
The following check modes are negotiable: None, One Byte
Sequence Number, and Extended. The mode is automatically
negotiated when a PPP call is placed to another device that
suppor ts the compression control protocol. Generally, Extended is
the preferred mode. The amount of compression depends on the
type of file being transferred. For example, a text file compresses
better than a binar y (application or executable) file.
Compression is enabled by default. If you enable compression on
the ISDN modem and your application uses compression,
compression will be disabled in the ISDN modem.
You can use compression in dual B channel Multilink PPP
connections and single B channel connections. By using
compression on a single B channel, you can achieve per formance
rivaling a two B channel connection at a fraction of the cost.
Because telephone and Internet providers often base charges on
the number of B channels used, the Netopia ISDN Modem’s
compression feature, which is not available in most other ISDN
terminal adapters, lets you achieve nearly the throughput of a two B
channel connection at the price of a single B channel connection.
Compression is negotiated between your ISDN modem and the
device to which you are placing the Multilink PPP call. To take
advantage of data compression, the device you are dialing into must
also suppor t data compression. If the other device does not
suppor t compression, compression will not be implemented.