Lucent Technologies 6000 - Manual (Page 318)

6-32 MAX 6000/3000 Network Configuration Guide
Configuring X.25
Setting up ISDN D channel X.25 support
Depending on the current state of a transaction or call, and the mode of operation selected,
T3POS uses different data formats and frame structures. The MAX supports four modes of
operation: Local, Binary-Local, Transparent, and Blind.
General frames
A general frame (or data frame) is any sequence of octets received from or sent to the DTE
within the period specified by the T1 timer (this timer is known as the Char-to-Char timer). In
Local and Binary-Local modes and in opening frames, general frames are encapsulated in the
following format:
STX [data] ETX XRC
where:
• STX is the ASCII character \002.
• Data is the user data being sent in this frame.
• ETX the ASCII character \003.
• XRC is the checksum. For all modes except Binary-Local, the checksum is a one character
Longitudinal Redundancy Check (LRC) checksum. For Binary-Local mode, the
checksum is a two character Cyclic Redundancy Check (CRC) checksum.
Control frames
The MAX uses a control frame only when establishing a call and not during data transfer. You
can use the VT-100 interface in the MAX to configure the T3POS modes and most of the
T3POS parameters for the T3POS PAD. However, use of a control frame can override the
operating mode, called number, call user data, and some user facilities. A control frame is a
supervisory frame with the following format:
SOH MSS CUD STX [data] ETX XRC
where:
• SOH is the ASCII character \001.
• MSS is the Mode Selection Signal, which can be (optionally) used to indicate the mode for
the call.
• CUD is the Called User Data. It can contain an X.121 address, and user facilities or call
user data in an X.28 format.
• Data is optional in the control frame. In Transparent and Blind modes, the T3POS PAD is
essentially restricted to passing data frames between the T3POS DTE and the T3POS host.
• ETX is the ASCII character \003.
• XRC is the checksum. For all modes except Binary-Local, the checksum is a one character
Longitudinal Redundancy Check (LRC) checksum. For Binary-Local mode, the
checksum is a two character Cyclic Redundancy Check (CRC) checksum.
T3POS Timers
The T3POS protocol defines six timers:
• T1: Char-to-Char timer