TCP and UDP
TCP guarantees ordered, reliable delivery at the cost of latency; UDP delivers packets fast with no such promise.
TCP and UDP are the two transport-layer protocols nearly everything on the internet is built from, and the choice between them is a choice about which failure mode you'd rather have. TCP (Transmission Control Protocol) establishes a connection, numbers every byte, retransmits anything lost, and delivers data to the application in order — a stream abstraction that hides the packet-switched, unreliable network underneath it. UDP (User Datagram Protocol) does none of that: it fires datagrams and does not confirm they arrived, does not reorder them, and does not retry.
The handshake is the visible cost of TCP's guarantees. A connection opens with a three-way handshake (SYN, SYN-ACK, ACK) before a single byte of application data moves, and closing is similarly ceremonial. UDP has no handshake — the first packet sent is the first packet of data — which is why protocols built for speed over correctness (DNS queries, video calls, game state) often prefer it. A dropped UDP packet just doesn't arrive; nothing pauses waiting for a retransmit that reliability would demand.
This tradeoff is exactly why real-time media favors UDP: a WebRTC call would rather skip a lost audio frame than stall the whole stream waiting for TCP to retransmit it in order, since a slightly glitchy stream beats a frozen one. QUIC is the modern rebuttal to "just use TCP for reliability" — it builds TCP-like guarantees on top of UDP, per-stream instead of per-connection, to avoid one lost packet blocking unrelated data (head-of-line blocking).
Reliability is also why TCP is the wrong tool for anything latency-sensitive under packet loss: its congestion control treats loss as a signal to slow down, which is correct for bulk transfer and actively harmful for a live call.
See also4
Latency and Jitter
Latency is how long a packet takes; jitter is how much that time varies — and the second often matters more.
Networks & Distribution14 connections
Port
The numeric endpoint a network service listens on, and a scarce shared resource on a developer machine.
Systems & Tooling19 connections
IPv6
IPv6 exists mainly to end address scarcity, with a large enough space that per-device NAT becomes optional.
Networks & Distribution15 connections
Port Scanning
Probing a machine's network ports to find which services are listening, the first step of both attacks and audits, now done to the entire internet in minutes, so anything exposed gets found.
Networks & Distribution9 connections
Linked from14
- BitTorrentNetworks & Distribution
A peer-to-peer file-sharing protocol from 2001 in which everyone downloading a file also uploads pieces of it to others, so popular files get faster as more people want them, and its legitimate and pirate uses.
- ChecksumNetworks & Distribution
A small value computed from data so that accidental corruption can be detected later, from parity bits and credit card check digits to the CRCs in every Ethernet frame, and useless against deliberate tampering.
- Denial-of-Service AttackNetworks & Distribution
Making a service unavailable by overwhelming it with traffic or expensive requests, usually from many machines at once, and the layered defenses that absorb or filter the flood.
- HTTP2 and HTTP3Web Platform
Two successive rewrites of HTTP's transport layer, each solving the previous version's head-of-line blocking at a different layer.
- IPv6Networks & Distribution
IPv6 exists mainly to end address scarcity, with a large enough space that per-device NAT becomes optional.
- KernelSystems & Tooling
The core of an operating system that runs with full hardware privileges, managing processes, memory, devices, and files on behalf of every other program.
- Latency and JitterNetworks & Distribution
Latency is how long a packet takes; jitter is how much that time varies — and the second often matters more.
- MQTTNetworks & Distribution
A lightweight publish-subscribe protocol in which devices send small messages to topics on a central broker, the common language of sensors, smart homes, and industrial telemetry.
- Network SocketNetworks & Distribution
The programming interface through which a program talks to the network, identified by an address and a port, and treated by the operating system as one more file descriptor.
- Port ScanningNetworks & Distribution
Probing a machine's network ports to find which services are listening, the first step of both attacks and audits, now done to the entire internet in minutes, so anything exposed gets found.
- QUICNetworks & Distribution
QUIC rebuilds reliable, multiplexed transport on top of UDP so one lost packet stops blocking unrelated streams.
- Tail LatencyNetworks & Distribution
The slowest few percent of response times, which averages hide and which dominate the experience of large systems, because one request often waits on many others.
- TimeoutNetworks & Distribution
The limit on how long to wait for a remote call, the most basic defense against a hung dependency, and the harder problems of choosing the number and passing the remaining time down a chain of services.
- WebSocketWeb Platform
A persistent, full-duplex connection between browser and server, replacing repeated request-response with an open channel.