Beta Draft Confidential
7-121/19/05 ATM Services Configuration Guide for CBX 3500, CBX 500, GX 550, and B-STDX 9000
Configuring Trunks
About APS
APS Trunk Backup on a GX 550 — Configure the working and protection ports on 
either the same module (BIO or Phy) or a different module (BIO or Phy). See the 
Switch Module Configuration Guide 
for CBX 3500, CBX 500, GX 550, and B-STDX 9000 
for more information.
APS Resilient UNI
The APS Resilient UNI option is available for all CBX 3500, CBX 500, and GX 550 
optical modules. When configuring APS Resilient UNI, you can provision the 
working port and the protection port on two different switch modules, protecting 
against module failure. You can use this option in conjunction with Lucent UNI 
logical ports. 
When configuring APS Resilient UNI, you have to provision a separate logical port on 
each working and protection port, and then configure a fault tolerant PVC/Resilient 
UNI between the two working ports. For more information, see “Using APS With 
Resilient UNI” on page 14-9.
Special Considerations
APS Resilient UNI on a CBX 3500/CBX 500 — Configure the working and 
protection port on different IOMs. See the Switch Module Configuration Guide 
for 
CBX 3500, CBX 500, GX 550, and B-STDX 9000 
for more information.
APS Resilient UNI on a GX 550 — Configure the working and protection port on 
either the same module (BIO or Phy) or a different module (BIO or Phy). See the 
Switch Module Configuration Guide 
for CBX 3500, CBX 500, GX 550, and B-STDX 9000 
for more information.
APS Resilient UNI Over PNNI
You can use the APS Resilient UNI option to configure fault-tolerant ATM PVCs 
across a PNNI or combined Virtual Network Navigator (VNN)/PNNI domain. You 
configure APS Resilient UNI over PNNI links using the same procedure as you would 
for ATM VNN OSPF networks.
For details, see “Resilient UNI and APS Resilient UNI Over PNNI” on page 21-25.
Fast Inter-card APS 1+1
The Fast Inter-card APS 1+1 option (Fast APS 1+1) is available for the modules 
shown in Table 7-1 on page 7-7. You can use the Fast APS 1+1 option with Lucent 
ATM direct cell trunks. Fast APS 1+1 provides switchover times that are within 50 
msec.
Note  – As traffic is rerouted from a working trunk to a protection trunk during a 
failure, the switchover speed may be less than that provided by Intra-card APS 1+1.