Aps Protocol For Switch From Working Line To - Extreme Networks PoS Installation And User Manual

Based on the K1 and K2 definitions, Table 3-15 shows the detailed APS protocol
exchanges for switching from the working line to the protection line. The example
assumes the switch occurs because a Signal Degrade condition is detected on the
working line. All APS protocol exchanges occur on the protection line, between the
protection router and the ADM.
Table 3-15: APS Protocol for Switch from Working Line to Protection Line
Protect Router → ADM ADM → Protect Router
K1 Byte
0000 0000
1010 0001
1010 0001
1010 0001
1010 0001
After the APS line switch has completed, the protection router sends a message to the
working router over the Ethernet link. The message indicates that the line switch has
been performed. The working router responds by taking down the SONET interface
and initiating a routing topology update. Similarly, the protection router brings the
SONET interface up and advertises availability of routes accessible via the SONET
interface. The neighboring PPP router will think that its partner (which is now the
protection router) has renegotiated the link. On the LAN side, packets with destinations
accessible via the SONET interface will be forwarded to the protection router. These
packets may be forwarded to the protection router as a result of the routing topology
updates or the Extreme Standby Router Protocol (ESRP).
Packet Over SONET Module Installation and User Guide
K2 Byte K1 Byte
0000 0 101 0000 0000
0000 0 101 0000 0000
0000 0 101 0010 0001
0001 0 101 0010 0001
0001 0 101 0010 0001
K2 Byte
0000 0 101 No failures; working line active. Example
is provisioned for 1+1 architecture and
bidirectional switching mode.
0000 0 101 Protection router receives Signal Degrade
message from working router over
Ethernet link, and sends Signal Degrade
request for channel 1 (the working line) to
the ADM.
0001 0 101 ADM acknowledges the Signal Degrade
request by sending Reverse Request for
channel 1 in K1; K2 indicates that the
ADM has bridged channel 1 to the
protection line.
0001 0 101 Protection router selects (receives)
channel 1 data from the protection line
based on received K2, and uses K2 to
indicate that channel 1 is bridged to the
protection line.
0001 0 101 ADM selects (receives) channel 1 data
from the protection line based on received
K2.
Configuring and Monitoring APS Functions
Comments
3-81