The User Datagram Protocol (UDP), first described in 1980 by RFC 768, offers a minimal set of functionality: there is no guarantee of message delivery, no guarantee of message order, no congestion avoidance, and no tracking of connection state. In fact, UDP is often referred to as the null protocol, because it offers little functionality not already included in the IP layer.[Read More]
Innovation with Constraints
How Does TCP Work?
The transmission control protocol (TCP) does one job very well — it creates an abstraction that makes an unreliable channel look like a reliable network. For applications built over an unreliable network like the Internet, TCP is a godsend that hides a lot of the inherent complexity in building networked applications. A laundry list of TCP features that application developers rely on every day includes: retransmission of lost data, in-order data delivery, data integrity, and congestion control. This article provides an introduction TCP, describing the structure of TCP segments, how TCP connections are established, and the algorithms that govern the flow of data between senders and receivers.[Read More]
How Do Websockets Work?
A WebSocket is a persistent connection between a client and server. WebSockets provide a bidirectional, full-duplex communications channel that operates over HTTP through a single TCP/IP socket connection. At its core, the WebSocket protocol facilitates message passing between a client and server. This article provides an introduction to the WebSocket protocol, including what problem WebSockets solve, and an overview of how WebSockets are described at the protocol level.[Read More]
The Zero Bug Policy
Building Quality into Your Process
How Does HTTP/2 Work?
Note: To make this easier to read (and write), h1 may be used in place of HTTP/1, and h2 may used in place of HTTP/2.
HTTP/1 has a long and storied history. Originally developed as a sixty page specification documented in RFC 1945, it was designed to handle text-based pages that leverage hypermedia to connect documents to each other. Typical web pages would kilobytes of data. For example, the first web page was a simple text file with web links to other text documents. Now, the web is made up of media-rich sites containing images, scripts, stylesheets, fonts, and more. The size of a typical web page is measured in megabytes rather than kilobytes, and the number of requests required to assemble a full page can be over one hundred. The reality of how web pages are built today does not match the reality that HTTP/1 was designed to support.[Read More]