Transmission network topology in principle is organized as in Picture 1.In between two OSN there is a hop of third party LH radio organized in 1+1 regime. OSN is connected to LH radio locally on site trough STM-1 optical interfaces. ECC channel is enabled on interfaces 1 to 4 of SLQ1 card.
No particular alarm has been generated on T2000 but multiple replies were noticed on commands issued from Navigator. Following scenario has been applied:
a) Perform log in procedure to NE OSN 1500B from Navigator or T2000 Remote client application;
b) Execute commands for collecting general configuration data from NE. For example:
We have started with ECC channel analyzis (refer to Picture 1). In radio transmission network on site A where selective receiving is applied towards NGSDH equipment, one ECC channel is received from OSN. This ECC channel is multiplied in base band of microwave on site A. Because one ODU is active, only one ECC channel is transmitted to site B.
Problem occurs on site B where ECC channel is multiplied in radio base band units of microwave LH equipment. In this way single ECC channel is delivered to OSN on site B trough two different STM-1 physical interfaces. When single command is issued to OSN on site B it will operate as two same commands are issued in almost same time. As the number of hops in network increases, the number of multiplied commands is also increased.
From Navigator output it can be concluded that OSN 1500B acts as same command is executed 4 times. Traffic that is passing trough OSN is normal.
After increasing number of hops the broadcast of management data caused by multiplication in radio system is also increased. This may lead to management data overflow and packet drop which will finally result in lost of management function.
Following solutions are possible:
i) Disable multiplication of ECC channels on third party Microwave equipment;
ii) Disable ECC channels on NG SDH equipment and leave ECC channels active only on one STM optical interface towards Microwave equipment. This solution will have consequences in case of working link of base band is down and protection is activated which will finally result in management lost of certain NGSDH node;
iii) Configure OSN as Gateway NE if IP network is on disposal.