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Unable to provide 55 MBps between Other vendor RNC(N) and other Vendor OMS(E) due to replicate packet in VCTRUNK.

Publication Date:  2012-07-25 Views:  80 Downloads:  0
Issue Description
In a certain network, customer requires a 55 MBps link between RNC and OMS. Huawei OSN 7500 equipped with SSN2EGS201 boards with software version 5.53 are used for providing a 55 Mbps link between another Vendor RNC(N) and another Vendor OMS(E) as shown below. EPLAN Service with VLAN 300 is configured in by binding 1x VC3 & 5 E-1 in two VC trunks.
Upon applying traffic huge broadcast traffic is reported by RNC which causes packet loss therefore the link is unusable.
NE software Version:
5.21.18.50P01

T2000 verison : V200R007

Alarm Information

No alarms or events:
RMON performance shows broadcast packets greater than 1400:


Handling Process
The link is tested end to end with FST analyzer with a throughput test and broadcast packets are observed. The link is agian tested after configuring VLAN 300 on a single VC trunk and then broadcast traffic is found to be normal.
Customer is informed of the broadcast issue and The link is configured again with VLAN 300 on single VCRUNK 5 with 2x VC3. It is suggested to apply CAR to modify port data rate to 90 Mbps.



Root Cause
As per the strict requirement from the customer design team we need to configure SSN2EGS201-1 board with 1VC3 and 5 VC 12 capacity. Since the EGS2 cannot bind VC3 and VC12 in a single VC trunk we use two different VCTRUNKS (VCTRUNK 5 & 13) and configure the VLAN 300 on both the VCTRUNKS.
VLAN 300 -> VCTRUNK 5(VC3) + VCTRUNK 13(5xVC12)

The configuration was mistakenly compared with that of configuring 1G services in EGS 2 board.

The broadcast is due to configuring a single VLAN (VLAN 300) on two different VCTUNKS. The packets form other Vendor RNC (NOKIA) seem to be replicated between the two VCTRUNKS hence causing broadcast and packet drops in the link with OMS (erriccson).


Suggestions
For EGS2 board there exists a limitation for versions earlier than V100R10 that for a 1G service bandwidth we need to configure a single VLAN in 2 VCTUNKs (each having 4 VC4), therefore the same configuration was carried out for a lower badwidth rate.

For normal practive however avoid configuring a single VLAN on multiple VCTRUNKs in EPLAN services especially in EGS-2 board.
Use the CAR menthod to limit the data rate to customers requirement.
Always sepereate other vendor equipmetn and perform End to end test with analyzer when other vendors are involved in data services.

END