Alcatel-Lucent 5620 - Page 73

5620 SAM Server to NE network reliability
The 5620 SAM Server requires reliable network connectivity between the 5620 SAM
Server/Auxiliary to the managed network elements. The mediation layer in 5620 SAM is
designed to recover from lost packets between the 5620 SAM Server and the network
elements; however, these mechanisms come with a cost to performance. Any measurable
packet loss will degrade performance of 5620 SAM's ability to manage the Network
Elements. The loss of packets between SAM and NE will have an impact on (but not
limited to):
• Any SNMP operations to the network elements:
• SNMP Trap processing performance
• Provisioning performance
• Provisioning failures
• Performance statistics collection (possibly to the point where statistics collection will
be incomplete)
• STM test operation (initiating test and collecting results retrieval)
• NE discovery and resync performance
• NE discovery and resync failures
• scheduled polling for reachability checks
• Accounting Statistics retrieval (possibly to the point where statistics collection will be
incomplete)
• CLI session operation
• NE backup retrieval and software download performance
The following example highlights the significant impact of lost packets. It only considers
the SNMP communication times with one network element. With the default mediation
policy configured with an SNMP retry time-out of 10 seconds, and an average round trip
latency of 50 ms between 5620 SAM Server and the network element, 5620 SAM will
spend a total of 25 seconds sending and receiving 1000 packets (500 SNMP gets and 500
SNMP responses). With a 0.1% packet loss (1 packet out of the 1,000) the 5620 SAM
Server will wait for the retry time-out (10 seconds) to expire before retransmitting. This
will cause the time to complete the 500 SNMP gets to increase by 10 seconds – for a total
of 35 seconds of communication time, or an increase of 40% over the time with no packet
loss. With 0.5% packet loss, the 500 SNMP gets would increase by 50 seconds – for a
total of 75 seconds to complete or an increase of 200%.
Network requirements Network reliability considerations
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5620 SAM
3HE-09809-AAAG-TQZZA 13.0 R7
Issue 1 December 2015
5-19