5Network management & HA

• 5.1Network management & monitoring

  Covers device monitoring via SNMP (manager/agent/MIB/OID), the trade-off between polling and traps, the security hardening of SNMPv3, flow monitoring with NetFlow/sFlow, event collection via syslog, and the design thinking behind monitoring design for early fault detection.

• 5.2Performance & traffic design

  Covers performance metrics such as throughput, bandwidth, latency, jitter, and packet loss; queueing theory (M/M/1) (utilization ρ, average waiting time) for mathematically modeling congestion; traffic-volume estimation and capacity management; and diagnosing the root cause of performance degradation (bottleneck diagnosis).

• 5.3QoS & bandwidth control

  Covers why QoS is needed to protect the quality of voice and video traffic, priority control (priority queueing), which separates queues by priority, shaping and policing, which control transmission rate, the standardized priority-marking schemes DiffServ (DSCP) and IntServ, and congestion control, which prevents network-wide collapse.

• 5.4Redundancy & high availability

  Covers VRRP/HSRP for default-gateway redundancy, link aggregation for bundling physical links, route redundancy for securing multiple paths, active/standby device redundancy, calculating availability, MTBF, and MTTR, and eliminating a single point of failure (SPOF) that threatens an entire system.