High Avaliability: A Long-Term Feature in Network Elements

Behind the growth of the amount of broadband users connections in the world, the wide use of mobile devices as cell phones and PDAs and other accesses from anywhere throughout Internet, always require some level of availability to support customer needs. This necessity made high availability architectures be used on large scale and has been migrated to service providers which offer solutions and, furthermore, they ensure short time to repair. This paper addresses “high availability”, one of the basic requirements of today systems on the Internet, presenting the main concepts, drawbacks and an automaton for these drawbacks´ solution. Based on the two main protocols for high availability (VRRP and CARP), in particular, two problems are addressed, which leads to the environments do not respond to requests for services: split brain and no-brain. These protocols will be fast presented, as well as the study on the basis of the problems mentioned and observed in a production environment. The diagnostic for split-brain and no-brain was determiner for the solution problem. This work proposes a protocol extension, based on formal language methods (Petri Net), for high availability architectures regarding the mentioned drawbacks on protocols which reside in that kind of architecture.