Building a secure network

The internet begans as an experiments in 1969 by ARPA of the US Departement of defence.ARPA's intention was to create a very reliable digital communications network that could be used in wartime, so communication could be maintain even if the stations or physical links were targetted during attacks.Early researches into this area adopted an innovative and powerfull idea - packet switching- to build the ARPANET.Subsequencely the new technology proved to be highly successful.In the following years, more research networks were created and the ARPANET evolved into the NSFNET, before finally becoming the Internet we know today.

The internet began into rouse the interests of the public during the 1990s, partly due to the wide applications of PC and WWW.Soon access to the internet became a popular services of the residential customers as well as enterprises and the number of internet users has increase exponentially over the years, so much so, that as of the end of 2006, the number of people using the internet has sky rocketed to 1 billion worlwide.

As a public communcaiton service, the internet access has to reliable.However the kind of reliability that ARPA was looking for was actually robustness,that is, the capability to function correcly under negative impacts, so commands can be delivered to the outposts to coordinate attacks, even after some stations had been destroyed.In comparasion, the kind of reliability that the public needs is high availability.That is the proportion of the time whe the service is available, which is this instance, should be most of the time

Accoring to the Infocomm Development authority of Singapore, the availability of internet service provide by major ISPs in Singapore about 99.99%.In other words, internet service is unavailable and cannot be accessed for a little than a hour each year
Since the most people use the internet for seding email, browsing news sites,searching for information,etc, and for basically nothing very critical, then most people are satisfied with the service.

The new millenium has withnessed the coming of network convergence.A fair portion of long haul calls had been packetisez nad routed to the internet and now ILECs are beginning to replace PSTN with IMS.Succesful deployments of IPTV by pioneer telecom operators have helped to showcase the revenue and profit potential and triple play service and triggered a new wave of expansion of IP networks globally.As a result, more and more enterprises are switching to IP VPN to replace the expensive frame relay ceoonections.As the telecommunication network is heading into an all IP era, the internet will become the common IP bearer network for all kinds of new services.

Glory is always accompanied by a heavier sense of responsibility.Telecom operators established the availability standarad for PSTN and leased circuits long ago, five 9s (99,999%) which translate into 5 minutes downtime per year.Cable operator have a similar availability satandard for cable TV.In order to bear the traffic multy-play or VPN services, the IP bearer network has to be revolutionized,hence,improving availability from four 9s, to five 9s

To make the task even harder,some services are session based such as voice service. If the call is broken then the call is dropped and customers have to dial again.To effectively deal with this issue,the IP bearer network has to provide a fast automatic oath swichover mechanism to re reroute the traffic,like,SDH or PSTN, which are able to provide 50 milliseconds automatic protection

Is summary, as the common IP bearer network in All-IP era, the IP bearer network needs to be able to provide four 9s for internet access, five 9s for voice,IPTV and VPN, as well as a fast path switchover mechanism for session based services