1 General
1.1 Introduction
1.2 Signal unit delimitation and alignment
1.3 Error detection
1.4 Error correction
1.5 Initial alignment
1.6 Signalling link error monitoring
1.7 Link state control functions
1.8 Flow control
2
Basic signal unit format
2.1 General
2.2 Signal unit format
2.3 Function and codes of the signal unit fields
2.3.1 General
2.3.2 Flag
2.3.3 Length indicator
2.3.4 Service information octet
2.3.5 Sequence numbering
2.3.6 Indicator bits
2.3.7 Check bits
2.3.8 Signalling information field
2.3.9 Status field
2.3.10 Spare fields
2.4 Order of bit transmission
3
Signal unit delimitation
3.1 Flags
3.2 Zero insertion and deletion
4
Acceptance procedure
4.1 Acceptance of alignment
4.2 Error detection
5
Basic error correction method
5.1 General
5.2 Acknowledgements (positive acknowledgement and negative
acknowledgement)
5.2.1 Sequence numbering
5.2.2 Signal unit sequence control
5.2.3 Positive acknowledgement
5.2.4 Negative acknowledgement
5.3 Retransmission
5.3.1 Response to a positive acknowledgement
5.3.2 Response to a negative acknowledgement
5.3.3 Repetition of message signal units
6
Error correction by preventive cyclic retransmission
6.1 General
6.2 Acknowledgements
6.2.1 Sequence numbering
6.2.2 Signal unit sequence control
6.2.3 Positive acknowledgement
6.3 Preventive cyclic retransmission
6.3.1 Response to a positive acknowledgement
6.3.2 Preventive cyclic retransmission
procedure
6.4 Forced retransmission
6.4.1 Forced retransmission procedure
6.4.2 Limitation of the values N1 and N2
7
Initial alignment procedure
7.1 General
7.2 Initial alignment status indications
7.3 Initial alignment procedure
7.4 Proving periods
8 Processor outage
9
Level 2 flow control
9.1 General
9.2 Detection of congestion
9.3 Procedure in the congestion situation
9.4 Congestion abatement procedure
10 Signalling link error monitoring
10.1 General
10.2 Signal unit error rate monitor
10.3 Alignment error rate monitor
11 Level 2 codes and priorities
11.1 Link status signal unit
11.2 Transmission priorities within level 2
12 State transition diagrams,
abbreviations and timers
12.2 Abbreviations
12.3 Timers
Annex A –Additions for a national option for high speed
signalling links
A.1 Introduction
A.1.1 Procedures for 1.5 and 2.0 Mbit/s data
rate signalling links
A.4 Acceptance procedure
A.4.1 Acceptance of alignment
A.10.1 General
A.10.2 Errored interval monitor for 1.5 Mbit/s
and 2.0 Mbit/s links
A.10.3
Alignment error rate monitor
A.12.3 Timers