In many cases, 7750 SRs are deployed in redundant pairs at the MSC. In this case, MC-APS is typically used for all ATM connections. Figure 1 shows this case, assuming that MC-APS is deployed on both the RNC connection and the ATM network connection. For MC-APS to be used, clear channel SONET or SDH connections should be used.
In this scenario, endpoint Y allows an ICB spoke-SDP as well as the primary spoke-SDP and secondary SAP. ICB operation is maintained as the current redundant pseudowire operation and the ICB spoke-SDP is always provided an active status. The ICB spoke-SDP is only used if both the primary spoke-SDP and secondary SAP are not available. The secondary SAP is used if it is operationally up and the primary spoke-SDP pseudowire status is not active. Receive is enabled on all objects even though transmit is only enabled on one.
To allow correct operation in all failure scenarios, an ICB spoke-SDP must be added to endpoint X. The ICB spoke-SDP is only used if the SAP is operationally down.
The following is an example configuration of Epipes mapping to Figure 1. A SAP can be added to an endpoint with a non-ICB spoke-SDP only if the precedence of the spoke is primary.
7750 SR #1
*A:ALA-A>config>service# epipe 1
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endpoint X
exit
endpoint Y
exit
sap 1/1/2:0 endpoint X
exit
spoke-sdp 1:100 endpoint X icb
exit
spoke-sdp 10:500 endpoint Y
precedence primary
exit
sap 1/1/3:0 endpoint Y
exit
spoke-sdp 1:200 endpoint Y icb
exit
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*A:ALA-A>config>service#
7750 SR #2
*A:ALA-B>config>service# epipe 1
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endpoint X
exit
endpoint Y
exit
sap 2/3/4:0 endpoint X
exit
spoke-sdp 1:200 endpoint X icb
exit
spoke-sdp 20:600 endpoint Y
precedence primary
exit
sap 2/3/5:0 endpoint Y
exit
spoke-sdp 1:100 endpoint Y icb
exit
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*A:ALA-B>config>service#