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Structure Of The Multiplexer Protocol; Introduction Of The Multiplexer Protocol; Data Link Layer; Figure 3: Data Link Layer - Siemens Mux_guide_v06 User Manual

Multiplexer user's guide
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Multiplexer User's Guide
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4 Structure of the multiplexer protocol

4.1 Introduction of the multiplexer protocol

The supported multiplexer protocol conforms to the GSM 07.10 Multiplexer Protocol. The
non-error recovery mode was implemented with the basic option.
The frames have a start and a stop byte. A checksum is calculated to protect the transferred
data. Frame repetition is not enabled.
Data and fax calls are transferred in the logical channel DLCI = 1 (DLCI: Data Link
Connection Identifier). The remaining DLCIs are in AT command mode; two GPRS
connections can be established simultaneously on every channel.
The multiplexer protocol must be started and the logical channels opened in compliance with
specified procedures.
This chapter also discusses the following issues:
Opening logical channels without parameter negotiation
Opening logical channels with parameter negotiation
Closing of logical channels

4.2 Data link layer

The
following
sections
show the detailed structure
a data link frame.

Figure 3: Data link layer

Mux_guide_v06
Flag
Address
Control
1 Octet
1 Octet
1 Octet
EA
C/R
DLCI: Data Link Connection Identifier
C/R:
Command / Response
EA:
extension bit; EA = 1
0xF9
Page 17 of 36
s
Length
Information
1 or 2 Octets
n Octets
EA
Length
Length: Length Information
EA:
extension bit;
EA = 1 -> 1 octet length information
EA = 0 -> >2 octets length information
Frame type:
SABM Set Asynchronous Balanced Mode
UA
Unnumbered Acknowledgement
DM
Disconnected Mode
DISC
Disconnect
UIH
Unnumbered Information with Header check
UI
Unnumbered Information
P/F-Bit Poll- /Final - Bit
DLCI
m
o b i l e
FCS
Flag
1 Octet
1 Octet
of
0xF9
Checksum for address,
control and length
fields, also for the
information field in the
case of UI frames FCS.
30.06.2004

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