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Outage due to lease line media Issue

Publication Date:  2012-07-25 Views:  124 Downloads:  0
Issue Description

Please refer to the picture above. We have a scenerio where customer has taken DS3 media from a leased line mux. From that mux we have distributed the E1 to different IDUs. Now, suddenly we see that E1 in IDU F,C and H is getting down and going up without any reason.Although other sites were up. We checked all configuration, link RSL etc and everything was Ok. Customer presurrised and gave the outage on Huawei as Leased line media provider said that everything was ok from their end as we got loop break from Mux.
Alarm Information
Handling Process
Media provider giving loop & break form BSC MUX end, the loop was through. Now instead of giving loop from the BSC Mux end, we gave loop from aggregation point (Media handover point) the loop was through again. Hence the leased media provider denied of any fault at their end. Then we asked for continuous loop for observation and after 3-4 minutes we got break on the 7th E1.Then we asked for the path of those 7 E1 and found out that the path was unprotected and a link between this unprotected path fluctuating. Thus we proved customer that the issue is with media and the saved outage of 5 hours .

Root Cause

After confirming that all parameters from our end was correct, we checked for the leased media end. We asked for the KLM mapping table as per the picture above, and found out that sites on a particular KLM table was fluctuating. This was because some E1 in the KLM table was protected whereas others were not protected. The above picture shows the scenerio. For the lease media service provider, node 11 to 15 was unprotected whereas other nodes were protected. Now, when their link fluctuated, our sites that were running on that particular KLM was getting down.
This was happening because 1st 7 Vc12 of this DS3 was not protected whereas other Vc12 were protected in their media, and a MW link was fluctuating in the unprotected path.
Media provider was giving loop from BSC end instead of Aggregation point. Also they were not checking the unprotected path and performance .