K1 Byte

The switch priority of a request is assigned as indicated by bits 1 through 4 of the K1 byte (as described in the rfc3498 APS-MIB); see Table 1.

Table 1. K1 Byte, Bits 1 to 4: Type of Request

Bit 1234

Condition

1111

Lockout of protection

1110

Force switch

1101

SF - High priority

1100

SF - Low priority

1011

SD - High priority

1010

SD - Low priority

1001

(not used)

1000

Manual switch

0111

(not used)

0110

Wait-to-restore

0101

(not used)

0100

Exercise

0011

(not used)

0010

Reverse request

0001

Do not revert

0000

No request

The channel requesting switch action is assigned by bits 5 through 8. When channel number 0 is selected, the condition bits show the received protection channel status. When channel number 1 is selected, the condition bits show the received working channel status. Channel values of 0 and 1 are supported.

Table 2 shows bits 5 to 8 of a K1 byte and K2 Bits 1 to 4 and the channel number code assignments.

Table 2. K1 Byte, Bits 5 to 8 (and K2 Bits 1 to 4), Channel Number Code Assignments

Channel Number

Code

Channel and Notes

0

Null channel.

SD and SF requests apply to conditions detected on the protection line.

For 1+1 systems, Forced and Request Switch requests apply to the protection line (for the 7750 SR only).

Only code 0 is used with Lockout of Protection request.

1 to 14

Working channel.

Only code 1 applies in a 1+1 architecture.

Codes 1 through n apply in a 1:n architecture (for the 7750 SR only).

SD and SF conditions apply to the corresponding working lines.

15

Extra traffic channel.

May exist only when provisioned in a 1:n architecture.

Only No Request is used with code 15.