WiFi, technically specified in the IEEE 802.11 set of standards, is one of the most widely deployed wireless standards in the world. Chance are the device you are using to read this article has is WiFi enabled. WiFi is a straightforward extension of Ethernet, with some slight adaptations for using radio instead of copper wire as the communication channel. Like Ethernet, WiFi has no central process that controls which device is allowed to transmit data at any point in time. Instead, each device decides on its own, and all devices must work together to guarantee good shared channel performance. With Ethernet, the protocol senses when the communication channel is busy and waits until it is free before sending data (carrier sensing). Ethernet also adds a collision detection protocol as an optimization. If a collision is detected, nodes stop sending data and use a randomized backoff algorithm to decide when to begin sending again. Together, these algorithms form the carrier-sense multiple access with collision detection algorithm (CSMA/CD). WiFi uses a similar strategy to Ethernet, but is restricted by the communication channel — there is no reliable way to detect collisions using radio waves. Therefore, instead of collision detection, WiFi uses a collision avoidance strategy defined by the carrier-sense multiple access with collision avoidance algorithm (CSMA/CA). ...

Ethernet is a technology developed a Xerox PARC in 1973 and 1974 to support local area networking. It has since been expanded to include a whole family of technologies that support various network architectures and topologies as part of the IEEE 802.3 working group dedicated to supporting networking using physical connections and devices (i.e. not wireless). Ethernet was built with the assumption that all computers on a network use a shared communication channel. The primary problem with using a shared connection is creating a sense of orderly traffic when an entire network of computers wants to constantly transmit data over the same channel. The core of that solution is sensing other node’s activity and waiting until the line is free and using collision detection to minimize the amount of traffic on the network. ...

All wireless networks (Wi-Fi, Bluetooth, 3G, LTE, etc.) operate using radio signals. Because they operate over the radio, all communication methods have a maximum channel capacity, regardless of technology. This maximum capacity was which is determined by the same underlying principles of information theory developed by Claude Shannon during World War II, known as Shannon-Hartley theorem or Shannon’s Law. Shannon’s Law states that This capacity relationship can be stated as: $$ {C=W\log _{2}\left( 1+{S \over N} \right)} $$ ...

Inspiration for software architecture often comes from the world of building architecture. In building architecture, the architect takes in local building codes to understand construction requirements. They analyze various building components like ductwork and furnaces, windows and doors, and figure out where and when to use standard components and when to build custom. They provide cost estimates for each of the components and for the whole, and then build out a blueprint providing upfront design and specification. ...

I recently had the pleasure of being part of the Tied to Machines podcast. We talked about the role of architecture, architectural leadership, and the intersection between architecture and business. You can listen to the full episode here.

Software is core to the operation of our business, and as architects, we are the key conduit between business and technology. Being technical leaders within this intertwined relationship means that we have a responsiblity to make sure that our business decisions and our technology decisions stay aligned. Being in this position demands leadership skills that are equal or better than our technical skills, so that we can effectively align business strategy with technical strategy, communicate that strategy to teams, motivate both teams and individuals, and influence outcomes. ...

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. ...

One of the many paradoxes of human creativity is that it seems to benefit from constraints. Although we [perceive] the imagination as requiring total freedom, the reality of the creative process is that it’s often entangled with strict conventions and formal requirements. Pop songs have choruses and refrains; symphonies have four movements; plays have five acts; painters still rely on the tropes of portraiture. Jonah Lehrer Constraints can seem like the last thing you’d want for a creative project, but they’re actually beneficial when it comes to doing good work. Anyone who has written knows the hurdle of the blank page, and the feeling that comes from being paralysed by innumerable choices. By restricting the choices available to us, paralysis disappears and we can focus on the task at hand. Don’t believe me? Consider the task of writing an entire story in less than six words. It seems impossible! How can you develop characters, expand a plot, and tell a tale in six words? Here’s how Hemingway did it: ...

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. ...

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. ...