Domain Name System
The distributed directory translating names to addresses, and the layer where propagation delays live.
The Domain Name System is the distributed database that turns names into addresses. A resolver walks from the root through each label to the authoritative server for the zone, caching results for the duration each record specifies.
Caching is the source of nearly every DNS frustration. A record's time-to-live governs how long resolvers may keep it, so a change is not instant and is not uniform — different people see different answers for a while. Lowering the time-to-live before a planned change is the standard preparation, and it has to happen before, since the old value is already cached.
The common record types are few: an address record, an alias record pointing one name at another, mail routing, and text records used for verification and policy. Provider-specific variants exist to work around the rule that an alias cannot coexist with other records at a zone's apex.
Subdomains are the practically important structure. They are ordinary names under a zone and can point anywhere, which makes them the natural mechanism for multi-tenant systems — each tenant addressed by name, with a wildcard record and a wildcard certificate covering them all. That certificate is usually the part that has to be provisioned deliberately rather than automatically, since proving control of a wildcard requires a DNS-based challenge. See Multi-Tenancy and Same-Origin Policy.
See also7
Multi-Tenancy
One deployment serving many isolated customers, with tenancy threaded through data, routing, and access.
Data & Content9 connections
Port
The numeric endpoint a network service listens on, and a scarce shared resource on a developer machine.
Systems & Tooling10 connections
Same-Origin Policy
The browser rule isolating documents by scheme, host, and port, and the mechanisms for relaxing it.
Web Platform15 connections
Cache Invalidation
Deciding when a cached value has stopped being correct — famously one of the hard problems.
Web Platform21 connections
Virtual Private Network
An encrypted tunnel that presents a remote network as local, and the narrow set of things a commercial one actually hides.
Networks & Distribution16 connections
Caller ID Authentication
Cryptographic attestation of an originating telephone number, and why spoofed calls survive it.
Networks & Distribution14 connections
eSIM
A SIM soldered into the device and provisioned over the air, with profiles downloaded rather than cards swapped.
Networks & Distribution10 connections
Related3
Nearby in the graph rather than deliberately chosen. Looser, sometimes surprising.
Linked from13
- AnycastNetworks & Distribution
Anycast announces the same IP address from many locations and lets normal routing send each client to the nearest one.
- Cache InvalidationWeb Platform
Deciding when a cached value has stopped being correct — famously one of the hard problems.
- Caller ID AuthenticationNetworks & Distribution
Cryptographic attestation of an originating telephone number, and why spoofed calls survive it.
- CAP TheoremData & Content
When a network splits a distributed system, it can stay consistent or stay available, but a proven theorem says not both.
- Content Delivery NetworkNetworks & Distribution
A CDN answers requests from servers near the requester, trading a single origin for many cached edges.
- DNS over HTTPSNetworks & Distribution
DNS over HTTPS wraps DNS lookups in encrypted HTTPS requests, hiding query contents from anyone but the resolver.
- eSIMNetworks & Distribution
A SIM soldered into the device and provisioned over the air, with profiles downloaded rather than cards swapped.
- IPv6Networks & Distribution
IPv6 exists mainly to end address scarcity, with a large enough space that per-device NAT becomes optional.
- Multi-TenancyData & Content
One deployment serving many isolated customers, with tenancy threaded through data, routing, and access.
- PortSystems & Tooling
The numeric endpoint a network service listens on, and a scarce shared resource on a developer machine.
- Same-Origin PolicyWeb Platform
The browser rule isolating documents by scheme, host, and port, and the mechanisms for relaxing it.
- TCP and UDPNetworks & Distribution
TCP guarantees ordered, reliable delivery at the cost of latency; UDP delivers packets fast with no such promise.
- Virtual Private NetworkNetworks & Distribution
An encrypted tunnel that presents a remote network as local, and the narrow set of things a commercial one actually hides.