Clio
Discovery, documentation and foundation. Notes on how things actually work, written so that they are quick to pick up again after a long time away.
Subjects
Android Kotlin · Compose
The platform from the inside: process model, app startup, rendering, lifecycle, and the Jetpack Compose runtime.
2 articles
System design Series
Networking and the edge, scaling compute, storage engines, consensus and reliability, observability and security.
5 articles
Networking Protocols
How bytes move on the wire: the journey of a packet, then TCP, UDP, QUIC, HTTP, FTP and ICMP.
7 articles
Linux systems Series
The kernel and system calls, processes and memory, filesystems, sockets and IPC, and the namespaces, cgroups and tracing tools containers are built from.
5 articles
CCNA 200-301 Series
Network fundamentals and addressing, switching, VLANs and spanning tree, routing and OSPF, IP services, security, wireless and automation.
16 articles
Latest
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How a network is built: hosts, switches, routers and the layers between them
The pieces a network is made of, the two layer models everyone argues about, what each box actually reads before forwarding, the cables and speeds behind the ports, and the vocabulary the rest of the series assumes.
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IPv4 addressing and subnetting: the arithmetic you learn to do in your head
What the 32 bits mean, how a mask splits them into network and host, the special ranges, and a method for cutting a block into subnets and reading an address in a few seconds without a calculator.
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IPv6 addressing: longer numbers, simpler rules
Why 128 bits, how to shorten an address without breaking it, the address types that replaced broadcast, how a host configures itself with SLAAC, and what neighbour discovery does that ARP used to.
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Cisco IOS from the console: the commands everything else assumes
How a switch boots, the modes and prompts, the two configuration files and the difference between them, setting up remote access safely, and the handful of show commands and shortcuts that make the rest of the series readable.
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Switching: how a frame crosses a switch
The Ethernet frame a switch reads, how it learns where every device lives, the three things it can do with a frame, why collisions vanished, and how to read the interface counters when a port misbehaves.
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VLANs and trunks: one switch pretending to be many
Why one broadcast domain stops being enough, how an access port assigns a VLAN, what 802.1Q actually adds to a frame, the native VLAN trap, and the three ways to route between VLANs.
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Spanning tree: the protocol that saves the network from itself
Why a single redundant cable can take down a whole switched network in seconds, how switches elect a root and block their way back to a loop-free tree, what RSTP changed, and the edge-port protections every access switch should have.
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Routing: how a router chooses a path
What actually happens to a packet inside a router, how to read a routing table, why the longest prefix always wins, what administrative distance settles, and how to write static, default and floating routes that behave.