Carrier Access Network Device Axxius 800 - Manual (Page 382)

7-10 Axxius 800 - Release 2.2
DS3 Controller Card
Controller and DS3 Redundancy
Network Protection Mode
The network mode of protection requires a single Controller with two independent DS3
channels. The cross connects are set up identically for both DS3s. Both revertive and
non-revertive modes are applicable. Two DS3 framers are present on the DS3
Controller card. Both are framed to their respective incoming data. Backplane data is
sent to both transmitters and is sent out both interfaces. On loss of signal or high bit
error rate, software will switch from Primary to Secondary interface. In revertive
mode, if the signal returns to the Primary interface or the BERT level is restored for a
period of time, software will return control to the Primary interface. In non-revertive
mode, return to the Primary interface would be by command only or if the secondary
line fails and the primary has returned to normal operation.
Electronics and Network Protection Mode
The highest level of protection, electronics and network protection, allows both the
Controller cards and the DS3 lines to be switched. This mode is available with two
Controllers and two active DS3 lines. Network protection switching must be enabled
and cross connects set up. In this mode, the primary Controller is connected to the both
the primary DS3 line and the secondary DS3 lines (TX and RX). The low-speed
transmit streams are multiplexed, framed and simultaneously broadcast on both the
primary and secondary DS3 lines, thus transmitting the identical payload to the far-end
service and protection line. Also, each Controller is framed up to both its DS3 lines
and the Controller select signal determines which Controller has access to the low-
speed cards, and thus carries the service.
If the active Controller malfunctions, if the DS3 line condition deteriorates, or a
maintenance switch is invoked (the switch command), a protection switch will occur in
the Axxius DS3, which enables the secondary DS3 path through the other Controller
card. If revertive switching is enabled after a five minute delay (beginning when the
previously-active controller’s error rate equals zero) the Axxius DS3 will switch back
to the previously-active Controller and DS3 line, if there is no longer a malfunction in
that path during the five-minute delay. If revertive switching is not enabled no switch-
back will occur.
NOTE: After a switching event in revertive mode, switching cannot occur
again until the original Controller and DS3 line have experienced 5 minutes
of error-free operation. The 5-minute delay is built-in, and conforms to
standards to prevent oscillation during poor DS3 line conditions.