Cisco 15454 2F BLSR interoperability with the Nortel LH combiner platform

Question

Help anyone, my problem is the following:
The company I work for is interfacing with another company that is running a 2 Fiber BLSR topology with the ONS 15454. This device will be interfacing with our existing Nortel LH combiner platform running version 2.0. When we dicussed this application with Nortel, they told us that the Cisco 15454 will not interface with the Nortel LH combiner cards due to the fact that the Cisco 15454 two fiber BLSR implementation is proprieitary and not standards compliant in that it requires use of the K1 byte of the second STS-1. Basically, the Nortel combiner cards are not transparent to the second STS-1, so the K1 value input is losted. They claim they did not have this issue with other vendors' BLSR SONET devices, just Cisco's 15454.
Another way they decribed the problem was: "The Nortel LH combiner cards do not work with the 15454 BLSR topology because of a proprietary overhead usage conflict. The Cisco product uses an undefined overhead byte for a BLSR check sum which conflicts with Nortel combiner mapping of tributary defined overhead into unused overhead of the aggregate line."
I do not know what software version Nortel was running when they did this testing with the ONS 15454, but I thought maybe someone has heard this one before and that maybe Cisco corrected this problem with a later release. Help anyone!

Answer 1

K3 Byte remapping is required...
"The ONS 15454 uses the K3 overhead byte for BLSR automatic protection switching (APS) to allow an ONS 15454 BLSR to have more than 16 nodes. If a BLSR is routed through third-party equipment that cannot transparently transport the K3 byte, you can remap it to either the Z2, E2, or F1 bytes on OC48AS cards."
Cisco allows more than 16 nodes in a BLSR but the K1 byte only has 4 bits available for 16 nodes. Cisco has extended this range of Node IDs which is proporietary to Cisco. However, I believe if the ring does not exceed 16 nodes then the 15454 complies to Telcordia standards...