Mission Critical Applications Limited

In 1999, a group at Nortel Networks' Harlow Laboratories developed a modification to the SIP internet telephony protocol which dealt with the provisioning of bandwidth in IP networks using MPLS switches. This was being proposed as a draft RFC to the IETF. The goal of the modification was to provide carrier-grade quality of service for internet telephony (by which is meant "QoS as good as you get when you pick up a conventional telephone handset"). This would allow IP infrastructure to begin to replace the more traditional infrastructure installed by the big telephone operators.

Nortel aproached the HISE group at the University of York to help them to develop a demonstrator for the protocol. The demonstrator required a network of SIP servers, developed to meet Nortel's revised SIP specifications. This was just around the time that Mission Critical Applications was being set up, and we were asked to provide the implementation of the SIP servers. The first proof of concept implementation was to be delivered, and integrated with the parts of the system being developed by Nortel, for demonstration before Christmas - less than 3 months away!

After meeting this delivery, and convincing Nortel management that the project was worth pursuing, there were milestone deliveries every 3-4 months. Each delivery was integrated into Nortel's prototype MPLS network for demonstration to potential Nortel customers, and for performance testing. The network grew to ten or more Linux nodes, plus Windows clients, and also allowed calls to be made between ethersets - telephone handsets with ethernet (not POTS) connections. It was even possible to make a call from an etherset to a conventional telephone anywhere in the world.

We also developed a graphical status display that could show the call set-up and tear-down processes in real-time. The SIP server code grew and shrank with the requirements document, but the maximum size was approximately 13,000 lines of C++. The status display was much smaller, being written in Python, and Python/Tk.

Mission Critical Applications' involvement in the project was successfully concluded in February 2001. Unfortunately the downturn in the telecoms market followed soon afterwards, and this caused Nortel to suspend further development.

In 1999 Vita Nuova in York acquired the world-wide rights to Inferno, an operating system developed at Lucent's Bell Laboratories by the same group that originally developed Unix. Inferno develops many of the ideas in Plan 9 - the "system which came after Unix".

One central goal of Plan 9 was that programs should not depend on the location at which they are run. This is achieved by several mechanisms, including a cleaning up of the Unix "everything is a file" philosophy, and strict source-code portability across host platforms. The first, allows a program to access its resources (files, devices, etc.) using the same mechanisms, regardless of whether, or not, the resources are attached to the same computer that is running the program.

Inferno goes one better than source-code compatibility by making all platforms binary-compatible using a virtual machine architecture. Thus, applications can be moved from machine to machine without any need for re-compilation, and this makes it especially easy to deliver applications over the network.

With the operating system, Vita Nuova also acquired the draft for a book by Rob Pike and Howard Trickey, describing Inferno from a programmer's point of view, and introducing the native language of Inferno, called Limbo. In 2001, Mission Critical Applications was asked to bring the book up-to-date (by that time, it had not been touched for about 6 years!). Martin Atkins, our technical director, became a co-author of the book, and added significant new material, particularly on the fileserving mechanisms which are central to the provision of services in Inferno.

The announcement of Martin's involvement can be found here, and the design for the front cover of the book can be found on Amazon. The book is expected to be available in March 2003.