What is a network?
Build the basic model: devices, links, messages, and rules.
Start lessonFusingBits Academy - Domain 01
Computer Networks
Understand the systems that move information between devices, from the first message to the wider Internet.
73 lessons availableDiscovery to network architecture
The route through this domain
Start with the model. Then follow the evidence.
Each stage adds a layer without hiding the earlier one. You can revisit any lesson as your questions become more precise.
Learning sequence
Computer Networks, from local link to global service.
Start here
Discovery
Build the first mental models for devices, messages, addresses, and names.
How is digital information measured?
Understand bits, octets, decimal and binary prefixes, conversions, and the difference between data size and data rate.
Start lessonHow are networks connected?
Understand topology, connection shapes, alternate paths, and what happens when a link fails.
Start lessonWhat does each network device do?
Compare endpoints, hubs, switches, routers, access points, gateways, and service intermediaries.
Start lessonHow does a device find another?
Explore addresses, names, and the first decisions made before a request travels.
Start lessonHow do addresses describe network boundaries?
Understand IPv4, IPv6, prefixes, and the role of subnets.
Start lessonHow does a device deliver traffic locally?
Understand ARP, unicast, broadcast, multicast, and local delivery decisions.
Start lessonHow does a local network reach another network?
Understand routers, default gateways, and the difference between local and remote destinations.
Start lessonHow do networks become the Internet?
Understand independent networks, providers, routers, and the interconnections that exchange reachability.
Start lessonHow do network addresses fit together?
Connect DNS names, IP addresses, transport ports, MAC addresses, and local frames into one addressing model.
Start lessonWhy did CIDR replace IPv4 address classes?
Compare historical Classes A through E with explicit CIDR prefixes and right-sized address blocks.
Start lessonBuild the system
Builder
Connect layers, transport choices, and boundaries into one working picture.
How does a message become a packet?
Understand encapsulation, headers, frames, packets, segments, and local hops.
Start lessonHow does a local link carry a frame?
Understand Ethernet, Wi-Fi, CAN, frames, switches, shared media, and local link delivery.
Start lessonHow do networks detect transmission errors?
Understand checksums, CRC, frame checks, corruption, loss, and retransmission.
Start lessonWhat happens on the journey?
Connect packets, routers, ports, and protocols into one working picture.
Start lessonHow do network layers divide the work?
Explore encapsulation and the difference between data, segments, datagrams, packets, and frames.
Start lessonHow does the presentation layer transform data?
Understand representation, encoding, serialization, compression, and encryption at OSI Layer 6.
Start lessonHow does the session layer coordinate a conversation?
Understand dialogue state, turn control, checkpoints, recovery, and orderly release at OSI Layer 5.
Start lessonHow do applications choose transport?
Compare TCP and UDP, ports, reliability, ordering, and the tradeoffs applications make.
Start lessonHow does an application open a connection?
Understand sockets, listening services, client connections, addresses, ports, and conversation state.
Start lessonWhat happens at the network boundary?
Understand private addresses, NAT, CGNAT, and the gateway between local and public networks.
Start lessonHow does flow control protect a receiver?
Understand receive windows, buffers, acknowledgements, and backpressure between sender and receiver.
Start lessonHow does a web request become an application exchange?
Understand HTTP, HTTPS, TLS, requests, responses, headers, and application-level meaning.
Start lessonHow does HTTP turn a request into a web response?
Understand methods, headers, status codes, caching, cookies, persistent connections, and HTTP/1.1, HTTP/2, and HTTP/3.
Start lessonHow do remote terminal protocols differ?
Compare Telnet, Rlogin, and SSH, including terminal negotiation, ports, trust models, and protected channels.
Start lessonHow do mail and file-transfer protocols differ?
Compare SMTP, POP3, IMAP, FTP, FTPS, and SFTP, including mail access, channels, ports, and security boundaries.
Start lessonHow does LDAP organize identities?
Understand directory entries, attributes, distinguished names, searches, binds, and protected directory access.
Start lessonHow does NNTP distribute news articles?
Understand news groups, article commands, server replication, Message-ID, feeds, and NNTPS.
Start lessonHow does NFS make a remote file system usable?
Understand NFS, RPC, mounts, file operations, versions, caching, locking, and export security.
Start lessonHow do real-time applications keep a conversation open?
Understand the WebSocket opening handshake, persistent bidirectional messages, heartbeats, and reconnection evidence.
Start lessonHow do network standards make systems interoperate?
Understand standards, protocols, implementations, and X.25 virtual circuits in the history of packet-switched networks.
Start lessonHow does optical fiber carry data?
Understand fiber construction, single-mode and multimode transmission, optical budgets, wavelengths, and Ethernet optics.
Start lessonHow does real-time communication keep information fresh?
Understand WebSocket, WebRTC, signaling, media and data paths, NAT traversal, jitter, adaptation, and recovery.
Start lessonConnect the networks
Interconnection
Understand the configuration and boundaries that let local networks reach beyond themselves.
How does a device join a network?
Learn how DHCP provides an address, subnet, gateway, and DNS settings.
Start lessonHow does a name become an address?
Understand DNS caches, resolvers, authoritative servers, and address records.
Start lessonHow can one switch serve separate networks?
Explore VLANs, access ports, trunks, broadcast domains, and inter-VLAN routing.
Start lessonHow does a router choose a path?
Learn how destination prefixes, next hops, interfaces, and default routes guide forwarding.
Start lessonHow can an administrator define a route?
Understand static routes, destination prefixes, next hops, and default routes.
Start lessonHow does SDN centralize network control?
Understand controllers, control and data planes, forwarding rules, and centralized network decisions.
Start lessonHow does OSPF find paths inside a network?
Understand link-state advertisements, costs, topology databases, SPF, and areas.
Start lessonHow does IS-IS route through a large network?
Understand link-state flooding, adjacencies, levels, metrics, and scalable interior routing.
Start lessonHow do networks find paths across the Internet?
Understand autonomous systems, BGP announcements, prefixes, and routing policy.
Start lessonWhat does an autonomous system number identify?
Understand ASNs, policy boundaries, prefixes, origins, and inter-domain identity.
Start lessonWhy can a nearby server answer a request?
Understand CDNs, origin servers, edge locations, caching, and cache misses.
Start lessonHow can one address reach several locations?
Understand anycast announcements, routing decisions, withdrawals, and distributed services.
Start lessonHow does IGMP manage multicast groups?
Understand multicast membership reports, router queries, joins, leaves, and local delivery state.
Start lessonHow can a service share requests across servers?
Understand load balancers, backend pools, health checks, and distribution rules.
Start lessonTest the model
Investigator
Use observable signals and practical experiments to ask better network questions.
How can you measure a network's responsiveness?
Understand latency, round-trip time, jitter, packet loss, and careful measurement.
Start lessonHow can you inspect the path to a destination?
Understand traceroute, hop limits, intermediate routers, timeouts, and path evidence.
Start lessonHow can a packet capture reveal an exchange?
Understand capture points, headers, ports, flags, timing, and encrypted payloads.
Start lessonWhich layer explains a connection error?
Distinguish transport, TLS, HTTP statuses, headers, and the evidence each layer provides.
Start lessonHow can you test the model?
Use browser signals and practical experiments to inspect what the network reveals.
Start lessonWhat can ping and ICMP tell you?
Understand reachability tests, ICMP responses, packet loss, and the limits of what ping can prove.
Start lessonProtect the exchange
Security
Learn how identity and trust checks protect secure network connections.
How does a certificate establish trust?
Understand hostname identity, validity dates, trust chains, and public-key binding.
Start lessonHow does a firewall decide what can pass?
Understand rules, direction, endpoints, services, ports, and connection state.
Start lessonHow can segmentation limit reachability?
Understand zones, boundaries, permitted flows, and the limits of isolation.
Start lessonHow does a VPN create a private path?
Understand encrypted tunnels, route choices, trust boundaries, and access beyond the endpoint.
Start lessonHow can you reason about a network attack?
Distinguish reconnaissance, interception, and saturation signals without overclaiming from one symptom.
Start lessonRead the pressure
Performance
Understand how capacity, queues, loss, and timing shape the experience of a network.
Why can congestion slow a network?
Understand queues, latency, loss, throughput, and careful performance measurement.
Start lessonHow can QoS protect important traffic?
Understand traffic classes, marking, scheduling, shaping, policing, and their trade-offs.
Start lessonHow can you measure availability?
Understand user-visible checks, observation windows, partial outages, and recovery evidence.
Start lessonHow can observability explain a failure?
Understand metrics, logs, traces, baselines, and correlation across a networked service.
Start lessonWhat is the difference between bandwidth and throughput?
Understand capacity, useful delivery, overhead, bottlenecks, and the evidence behind a throughput measurement.
Start lessonOperate the network
Operations
Read network behavior, troubleshoot evidence, and design for continuity under changing conditions.
How can switching loops destabilize a network?
Understand redundant paths, broadcast storms, and loop prevention.
Start lessonHow does IPv6 deliver traffic?
Understand IPv6 addressing, local discovery, assignment, and path diagnostics.
Start lessonHow can a network keep working through failure?
Understand resilient paths, failure domains, and observable recovery.
Start lessonHow does TCP respond to congestion?
Understand how acknowledgements, loss, and delay influence sending behavior.
Start lessonHow does a network fail over?
Understand redundant paths, devices, and tested failover decisions.
Start lessonHow do you troubleshoot a network?
Move from symptoms to evidence and test the narrowest explanation first.
Start lessonCompose the system
Architecture
Connect programmable networks, services, dependencies, and boundaries into resilient designs.
How does cloud networking connect services?
Understand virtual networks, subnets, routes, gateways, policies, and managed dependencies.
Start lessonHow can infrastructure changes stay predictable?
Understand infrastructure as code, plans, desired state, drift, dependencies, and safe changes.
Start lessonHow does peer-to-peer networking work?
Understand peer roles, discovery, direct exchange, resilience, security, and hybrid architectures.
Start lessonHow can a network route traffic without fixed infrastructure?
Understand MANETs, multi-hop forwarding, AODV, DSR, OLSR, mobility, partitions, and route repair.
Start lessonHow do three-tier and multi-tier architectures divide the work?
Separate presentation, application, data, integration, security, and deployment responsibilities.
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