Networking

A network is best understood as endpoints, links, forwarding systems, protocol boundaries, and services—not as a label based only on distance. This entry builds physical, logical, administrative, and failure-domain views of the same system and follows one request across them.

Layering separates network responsibilities into services and peer protocols; encapsulation carries each layer's control information around the data supplied from above. This entry maps OSI vocabulary to the Internet stack, works one message down and up the stack, and explains where clean layering intentionally leaks.

Physical attachment, logical forwarding, service reachability, and shared-risk structure are different topologies over the same system. This entry compares common graph shapes, shows how forwarding removes loops, and turns redundancy drawings into testable failure-domain claims.

Switching systems differ in when they allocate resources, how much data they buffer before forwarding, and whether intermediate nodes keep per-connection state. This entry compares circuit, message, datagram, virtual-circuit, and fixed-cell designs through delay, utilization, isolation, and failure behavior.

Multiple transmitters can share a communication resource by separating time, frequency, code, space, or combinations of them. This entry derives the accounting model, compares static and dynamic allocation, and explains why modern switched Ethernet and Wi-Fi have fundamentally different access behavior.

ALOHA exposes the mathematics of random access; carrier sensing and backoff reduce wasted attempts but cannot remove propagation delay or hidden-terminal uncertainty. This entry derives pure and slotted ALOHA throughput and connects the model to historical Ethernet CSMA/CD and current Wi-Fi CSMA/CA.

Ethernet keeps a common MAC frame and service across many physical media and rates. This entry separates the frame seen by a bridge from the symbols sent by a PHY, explains auto-negotiation and duplex, and turns counters and captures into a link-diagnosis method.

A transparent bridge learns source locations and forwards by destination within a VLAN-scoped forwarding context. This entry derives the learning and flooding rules, explains 802.1Q ingress and egress treatment, and shows how to diagnose stale state, flooding, and VLAN mismatches.

Redundant Ethernet paths become destructive loops unless bridges agree on a loop-free active topology. This entry derives STP/RSTP port roles, follows reconvergence after failure, separates spanning tree from link aggregation, and turns topology state into operational evidence.

Network telemetry turns device state, protocol state, flow records, events, probes, and packets into evidence about forwarding behavior. The hard part is not collecting more data but preserving what was observed, where, when, and with which loss, sampling, and aggregation limits.

Model-driven management separates schema, transport, desired configuration, intended configuration, applied state, and observed behavior. Safe automation is a verified control loop with validation, concurrency control, bounded rollout, and explicit failure semantics—not a script that sends commands faster.

Network troubleshooting is controlled hypothesis testing across explicit observation boundaries. This entry shows how to choose capture points, preserve timing and loss metadata, interpret offload artifacts, compare both directions, and prove that a repair addressed the actual failure.