Page 883 - 5G Basics - Core Network Aspects

Transport aspects 2

Figure 12-1 – Link states and link-state transition diagram

The link state usage shall be monitored through the following line performance monitoring parameters:
– L2.2 link state second (L2.2S): An L2.2S second is declared if the link is in the L2.2 state for at least
a fraction of the second.

– L2.1B link state second (L2.1BS): An L2.1BS second is declared if the link is in the L2.1B state for at
least a fraction of the second and no L2.2S is declared.
– L2.1N link state second (L2.1NS): An L2.1NS second is declared if the link is in the L2.1N state for at
least a fraction of the second and no L2.2S or L2.1BS is declared.

Counters of L2.2S, L2.1BS, and L2.1NS shall be inhibited only during unavailable time even if the unavailable
time is declared retroactively.

The procedures for transitions between L0, L2.1N, L2.1B, and L2.2 link states are defined in clauses 13.4.1,
13.4.2, and 13.4.3. The link state transition shall occur at the time instant the procedure is successfully
completed. If the procedure is not successfully completed, then no link state transition shall occur.
Guidelines for the duration of these procedures (transition times) between L0, L2.1N, L2.1B and L2.2 link
states are defined in clause 12.1.1.6.

The procedures for transition from the L0, or L2.1N, or L2.1B, or L2.2 link state to the L3 link state are:
• Deactivation as defined in clause 12.1.4.1;
• Fast retrain as defined in clause 12.1.4.2, triggered by the fast retrain policy (FRpolicy).
In either case, the link state transition shall occur at the time instant the FTU leaves the SHOWTIME state
(see Figures 12-4 and 12-5). If the FTU does not leave the SHOWTIME state because the L3 request was
rejected, then no link state transition shall occur.
The procedure for transition from the L3 link state to the L0 link state is defined in clauses 12.3.2 to 12.3.5
for initialization and in clauses 12.3.3 to 12.3.5 for a fast retrain. In either case, the link state transition
shall occur at the time instant that both FTUs enter the SHOWTIME state ("pass", see Figures 12-4 and 12-

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