JUNOS High Availability

Building a network capable of providing connectivity for simple business applications is a fairly straightforward and well-understood process. However, building networks capable of surviving varying degrees of failure and providing connectivity for mission-critical applications is a completely different story. After all, what separates a good network from a great network is how well it can withstand failures and how rapidly it can respond to them.While there are a great deal of books and resources available to assist the network designer in establishing simple network connectivity, there aren't many books which discuss the protocols, technologies, and the myriad ways in which high availability can be achieved, much less tie it all together into one consistent thread. "JUNOS High Availability" does just that, in essence providing a single, concise resource covering all of the bits and pieces which are required in highly available networks, allowing the network designer to build networks capable of sustaining five, six, or even seven nines of uptime.In general, there are a lot of misconceptions and misunderstandings amongst Network Engineers with regards to implementing high availability in Junos. One only needs to look at the fact that Graceful Restart (GR) protocol extensions and Graceful Routing Engine Switchover (GRES) are often mistaken for the same thing, thanks in no small part to the fact that these two technologies share similar letters in their acronyms. This book does a good job of clarifying the difference between the two and steers clear of the pitfalls typically prevalent in coverage of the subject matter. The chapter on `Control Plane High Availability' covers the technical underpinnings of the underlying architecture on most Juniper platforms; coverage of topics like the separation between the control and forwarding planes, and kernel replication between the Master and Backup Routing Engine give the reader a solid foundation to understand concepts like Non-Stop Routing, Non-Stop Bridging, and In-Service Software Upgrades (ISSU). In particular I found this book to be very useful on several consulting engagements in which seamless high availability was required during software upgrades as the chapter on `Painless Software Upgrades' discusses the methodology for achieving ISSU and provides a checklist of things to be performed before, during, and after the upgrade process. Similarly, I found the chapter on 'Fast High Availability Protocols' to be very informative as well, providing excellent coverage of BFD, as well as the differences between Fast Reroute vs. Link and Node Protection.Overall I feel this book is a valuable addition to any networking library and I reference it often when I need to implement certain high availability mechanisms, or simply to evaluate the applicability of a given mechanism versus another for a certain deployment. The inclusion of factoring costs into a high availability design is a welcome addition and one that all too many authors fail to cover. Naturally, it only makes sense that costs should be factored into the equation, even when high availability is the desired end-state, in order to ensure that ultimately the business is profitable. If I had to make one suggestion for this book it is that there should be additional coverage of implementing High Availability on the SRX Series Services Gateways using JSRP, as this is a fundamental high availability component within Juniper's line of security products. To the authors credit however, this book was written just as the SRX line was being released, so I don't fault the authors for providing limited coverage. Perhaps more substantial coverage could be provided in the future if a Second Edition is published.The bottom line is this - if you are a Network Engineer or Architect responsible for the continuous operation or design of mission-critical networks, "JUNOS High Availability" will undoubtedly serve as an invaluable resource. In my opinion, the chapters on `Control Plane High Availability', `Painless Software Upgrades', and `Fast High Availability Protocols' are alone worth the entire purchase price of the book. The fact that you get a wealth of information beyond that in addition to the configuration examples provided makes this book a compelling addition to any networking library.