Introduction to Server Administration

TCP/IP is the family of protocols on which the internet runs: IP moves packets between addresses without guarantees, and TCP or UDP ride on top to deliver either a reliable ordered stream or fast unordered messages.

The OSI model is a seven-layer reference framework that separates networking into physical transmission, link, network, transport, session, presentation and application concerns, used to reason about where a problem sits rather than to describe any real protocol stack.

IP addressing is the scheme that gives every interface on a network a numeric address, with IPv4's four-byte addresses now supplemented by IPv6's much larger space, and with private ranges reserved for use inside networks that reach the internet through translation.

Caching keeps the result of expensive work, such as a rendered page or a database query, and serves that stored copy until it expires, making it the largest single source of speed on any busy website.

Uptime is the proportion of time a service answers requests, quoted in nines, and a service level agreement is the contract clause setting out how that proportion is counted and what the provider owes when it falls short.

Kubernetes is an open-source system that runs containers across a cluster of machines, keeping the number and placement of running copies matched to a declared desired state, and restarting, rescheduling and scaling them without a person intervening.