Alcatel-Lucent 7750 SR OS, Руководство по настройке интерфейса, Страница: 53 / 444

Interface Configuration
7750 SR OS Interface Configuration Guide Page 53
APS 1+1 Protection and Working Port Management Operations
Switching Modes
The 7750 SR only transmits traffic on an active circuit. This may add to a network outage during
an APS switch. The 7750 SR supports bi-directional mode (default) and uni-directional mode. The
uni-directional mode is limited to APS signalling support to allow interoperability with network
elements that do not support bi-directional mode/uni-directional APS between two 7750s acting as
line termination equipment (LTEs) for an APS-protected line.
In bi-directional mode, the highest priority local request is compared to the remote request
(received from the far-end node using an APS command), and whichever has the greater priority is
selected. The relative priority of all events that affect APS 1+1 protection is listed in the
Table 15
on page 51 in descending order. The requests can be automatically initiated (such as signal failure
or signal degrade), external (such as lockout, forced switch, request switch), and state requests
(such as revert-time timers, etc.).
The following are behaviors of the 7750/7710 SR while operating in uni-directional mode (for
example, configured for uni-directional APS or connected to equipment configured for uni-
directional APS):
• The 7750 SR generates/transmits K bytes based on local request/condition only (i.e. as
required by the APS signalling).
• The 7750 SR always RX and TX on the same (active) circuit. This has the following
caveats:
→
If the 7750 SR performs an APS switch due to a local condition, then the 7750 SR
will also move its TX direction to the newly selected circuit (currently inactive) and
will send L-AIS on the currently active TX circuit to force the remote end to APS
switch to the newly active circuit. Note that some local request may not cause an APS
switch when a remote condition prevents both RX and TX direction to be on the same
circuit (for example an SD detected locally on a working circuit will not cause a
switch if the protection circuit is locked out by the remote end).
→
If the remote end indicates an APS switch and the 7750 SR can RX and TX on the
circuit newly selected by the remote end, then the 7750 SR will move its TX direction
and will perform an APS switch of its RX direction (unless the 7750 already TX and
RX on the newly selected circuit).
→
If the remote end indicates an APS switch and the 7750 SR CANNOT RX and TX on
the circuit newly selected by the remote end (for example due to a higher priority
local request, like a force request or manual request, etc.), then the 7750 SR will send
L-AIS on the circuit newly selected by the remote end to force it back to the
previously active circuit.