Digital Data; Determining The Packet Length - ZyXEL Communications omni TA128 User Manual

audible tone that will allow you to decide whether or not you
should take any action.
When an ISDN data call comes in, the TA128 will try to negotiate a
connection using the proper ISDN protocol. When an analog call
comes in, the TA128 will send the call to the analog port as the
factory default, Phone 1 and then Phone 2.

Digital Data

The TA128 currently supports Circuit Switched Data (CSD) for
ISDN data applications. The CSD protocols supported by the
TA128 include: PPP, MPPP, V.120, X.75, and V.110. PPP is the
most popular protocol used in North America; it is used by most
Internet service providers. Once the TA128 answers a call, it will
examine the incoming data to determine which protocol to use, and
automatically switch to this mode. The TA128 is able to auto-
switch for PPP, MPPP, V.120, X.75, V.110, and above protocols
over the speech channel. In most cases, you can rely on the auto-
switching feature for your applications. If you need more specific
settings for answering calls, refer to the section entitled "Answering
a Call using MSN" found later in this chapter.
: For DTE Port 2, only PPP, V.120, and X.75 are supported.
O O
NOTE

Determining the Packet Length

The user's information is sent on a frame-by-frame basis for V.120
and X.75. Sometimes we call it "packetized." The maximum frame
length on the sending side should not exceed the maximum frame
length that the receiving side allows. Sometimes this information
will be exchanged during handshaking. However, few
manufacturers, if any, have implemented this mechanism.
If the sending side sends packets greater than what the receiving
side allows, the receiving side will discard the frame and reply with
a Frame Reject frame (FRMR). FRMR indicates that the
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