“802.1aq Shortest Path Bridging Design and Evolution: The Architect’s Perspective” provides a sense of the relative simplicity of 802.1aq, explaining the small number of moving parts required to achieve what it does, and why those choices were made.
The book describes what were elective decisions and what decisions were dictated by the design goals using a multi-part approach to the book. First it uses a “what it is” description intended to provide an overview of SPB. Second is separated out, and uses a narrative form to describe the design process and decisions that led to SPB to provide further context in understanding the first part. It’s rounded out with applications and potential futures for the technology to suggest where it could go.
Shortest Path Bridging is the most recent of this series of evolutionary steps, and is arguably one of the 3 or 4 most significant enhancements in Ethernet’s history. Until SPB, Ethernet had retained its original control mechanisms, and these are now distinctly behind the state of the art in their properties. SPB refreshes this component of Ethernet, by taking the existing data path technology practically unaltered, and marrying it to a significant extension of the state of the art in distributed control planes, link state routing.