Cisco Cisco ONS 15600 Multiservice Switching Platform (MSSP)

When the Cisco ONS 15600 is used in the Data Communications Network (DCN) as a Gateway Network 
Element (GNE), Cisco Systems, Inc. recommends that: 

a. Each Cisco ONS 15600 GNE should cater to no more than 64 Data Communications Channels 
(DCC)-connected External Network Elements (ENE).
b. No ENE should be more than 8 DCC hops away from its GNE.
c. With large networks, the Cisco Transport Controller (CTC) Java Virtual Machine (JVM) Heap Size 
should be set to 512 MB (default is 128 MB).
d. When running R7.2.1 and above, the ONS 15600 GNE should be declared a SOCKS proxy in CTC 
preferences.
e. The number of simultaneous CTC sessions on the network should be limited to five.

When an ASAP card 1PIO that has STS1 circuits on it is removed, the downstream NE will see UNEQ-P 
on the STS1 circuits instead of AIS-P, as expected. Concatenated circuits will see AIS-P, as expected. 
This issue does not occur with 4PIO removals, or with concatenated circuits. This issue will be resolved 
in a future release.

When you perform a Manual Switch To Protect and then an SD-L condition is raised on the Protect port 
that preempts the Manual Switch To Protect, the CTC Maintenance > Protection tab shows 
“APS_CLEAR.” When you click Clear in that tab while the SD-L is still present on the protect port, the 
K bytes will change to “No Request” for about 400-1000 frames before redeclaring the SD-L condition. 
This issue can occur on ONS 15600 ASAP cards with 1+1 protection. It does not affect other cards or 
protection schemes. This issue does not affect traffic. This issue can only occur when using the CTC 
Maintenance > Protection tab under the aforementioned conditions. To avoid this issue, do not click 
Clear when the CTC Maintenance > Protection tab shows “APS_CLEAR” and SD-L is present on the 
protect port. This issue will be resolved in a future release.

A CTC client session can disconnect from an ONS node during simultaneous deletion of large numbers 
of VT level circuits (3000+). Connectivity to the node will recover without any user action. If the 
condition persists, restart the CTC session to reconnect. This issue is under investigation.

ONS platforms support only a single OSPF virtual link. This issue will be resolved in a future release.

Network connectivity could be lost if a backbone area becomes segmented into multiple GNEs. This 
occurs only if multiple ONS 15600 nodes and routers are connected to the same LAN in OSPF area 0. 
If a link between two routers breaks, the CTC session connected to Router 1 will not be able to 
communicate with the ONS 15600 connected to Router 2. To resolve, you must repair the link between 
the routers or provide another form of redundancy in the network. This is as designed.