1. Carrier Grade EAB/UK/T 2003-11-051 Carrier Grade – What does it mean At least 99.999% uptime –Downtime less than 5 minutes per year Designed for 10 to 20 years of life –Continuous changes of functionality and addition of new technology –Satisfies different environmental operating conditions This means there must be no planned “down time”. The system must continue to provide its intended service during: –All hardware maintenance, repair, upgrade etc –All software bug fixes, addition and removal of software –All backups etc –All types of reconfiguration –Overload situations The system must prevent operators from doing things which crash the system

2. Carrier Grade EAB/UK/T 2003-11-052 Ericsson Systems - Processors Ericsson’s telecom systems are typically made up of hierarchies of processors: –Lots and lots of regional or device processors which handle the hard real time. Crashing one of these does not crash the whole system so there is often no redundancy at this level. –A smaller number of central processors which handle soft real time. There must be redundancy schemes so that a failing processor’s job can be taken over by another processor.

3. Carrier Grade EAB/UK/T 2003-11-053 Ericsson Systems - Software Most telecom systems are implemented with millions of lines of program code. Making a totally bug free system is not possible. Telecom systems must be designed so that the effects of software bugs: –Is limited to a small part of the system –Can be recovered from with minimum disturbance