IT Infrastructure, Systems and Network Operations
This domain tests operational understanding of the infrastructure beneath services. Expect compute, storage, networking, virtualization, cloud, availability, capacity, backup and monitoring fundamentals, with enough depth to diagnose common service issues.
Core rules and concepts
- Compute may be physical, virtual or cloud. Virtualization abstracts resources; cloud adds self-service, elasticity and measured service.
- Networks carry traffic using layered models. DNS resolves names, DHCP assigns addresses, VLANs segment traffic, load balancers distribute requests and firewalls filter flows.
- Bandwidth is capacity; latency is delay. More bandwidth does not fix high latency or packet loss.
- Capacity management balances demand against resources. Availability depends on removing single points of failure and testing failover.
- Backups are not protection until restore is tested. Monitoring needs meaningful thresholds and alert routing.
Worked example
Users report intermittent slowness in an application. A weak response is to blame the network. A stronger sequence checks DNS resolution time, latency and packet loss to the service, server CPU and memory, storage IOPS and queue depth, database waits, and upstream dependencies. Each test narrows the layer. If latency is high but bandwidth is idle, adding bandwidth wastes money. The reasoning is to locate the constraint before changing capacity.
Traps
Equating bandwidth with speed; ignoring DNS and name resolution; treating virtualization as automatic high availability; never testing restores; monitoring infrastructure without monitoring user experience.