Cisco Systems 15454 7.3 OC-N Card Protection

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Cisco ONS 15454 Reference Manual, R7.0

78-17191-01

Chapter 7 Card Protection

7.3 7.3 OC-N Card Protection

7.3 OC-N Card Protection

The ONS 15454 provides two optical card protection methods, 1+1 protection and optimized 1+1

protection. This section covers the general concept of optical card protection. Specific optical card

protection schemes depend on the optical cards in use.

Any OC-N card can use 1+1 protection. With 1+1 port-to-port protection, ports on the protect card can

be assigned to protect the corresponding ports on the working card. The working and protect cards do

not have to be placed side by side in the node. A working card must be paired with a protect card of the

same type and number of ports. For example, a single-port OC-12 must be paired with another

single-port OC-12, and a four-port OC-12 must be paired with another four-port OC-12. You cannot

create a 1+1 protection group if one card is single-port and the other is multiport, even if the OC-N rates

are the same. The protection takes place on the port level, and any number of ports on the protect card

can be assigned to protect the corresponding ports on the working card.

For example, on a four-port card, you can assign one port as a protection port on the protect card

(protecting the corresponding port on the working card) and leave three ports unprotected. Conversely,

you can assign three ports as protection ports and leave one port unprotected. In other words, all the ports

on the protect card are used in the protection scheme.

1+1 span protection can be either revertive or nonrevertive. With nonrevertive 1+1 protection, when a

failure occurs and the signal switches from the working card to the protect card, the signal stays switched

to the protect card until it is manually switched back. Revertive 1+1 protection automatically switches

the signal back to the working card when the working card comes back online. 1+1 protection is

unidirectional and nonrevertive by default; revertive switching is easily provisioned using CTC.

Note When provisioning a line timing reference for the node, you cannot select the protect port of a 1+1

protection group. If a traffic switch occurs on the working port of the 1+1 protection group, the timing

reference of the node automatically switches to the protect port of the 1+1 protection group.

Optimized 1+1 protection is used in networks that mainly use the linear 1+1 bidirectional protection

scheme. Optimized 1+1 is a line-level protection scheme using two lines, working and protect. One of

the two lines assumes the role of the primary channel, where traffic is selected, and the other line

assumes the role of secondary channel, which protects the primary channel. Traffic switches from the

primary channel to the secondary channel based on either line conditions or an external switching

command performed by the user. After the line condition clears, the traffic remains on the secondary

channel. The secondary channel is automatically renamed as the primary channel and the former primary

channel is automatically renamed as the secondary channel.

Unlike 1+1 span protection, 1+1 optimized span protection does not use the revertive or nonrevertive

feature. Also, 1+1 optimized span protection does not use the Manual switch command. The 1+1

optimized span protection scheme is supported only on the Cisco ONS 15454 SONET using either

OC3-4 cards or OC3-8 cards with ports that are provisioned for SDH payloads.

Optimized 1+1 is fully compliant with Nippon Telegraph and Telephone Corporation (NTT)

specifications. With optimized 1+1 port-to-port protection, ports on the protect card can be assigned to

protect the corresponding ports on the working card. The working and protect cards do not have to be