* Using both cable and DSL provides a highly reliable service at a very low price
Over in the WAN newsletter, Steve and Joanie have been discussing the idea of using cable modem access and DSL in the small office/home office environment for providing highly reliable service at a very low price. The fundamental belief is that by having both services available – especially since they tend to have separate building entry points, physical routing, and network infrastructures – you end up with a highly reliable service. (The arithmetic indicates that even if the reliability of each service were only 95%, the reliability of having at least one of the two parallel paths available is 99.75%. With 99% availability for each service, you end up with 99.99% availability of one of the two paths.)
Over in the WAN newsletter, Steve and Joanie have been discussing the idea of using cable modem access and DSL in the small office/home office environment for providing highly reliable service at a very low price. The fundamental belief is that by having both services available – especially since they tend to have separate building entry points, physical routing, and network infrastructures – you end up with a highly reliable service. (The arithmetic indicates that even if the reliability of each service were only 95%, the reliability of having at least one of the two parallel paths available is 99.75%. With 99% availability for each service, you end up with 99.99% availability of one of the two paths.)
As more and more users are considering IP Telephony services over their broadband access links, this arrangement tends to make a lot of sense – especially since we seem to have a somewhat universal consensus that broadband data services are not yet up to the reliability of plain old (analog) telephony service (POTS).
Steve and Joanie furthered this experiment by trying out one of several available routers designed for the SOHO/ROBO (remote office/branch office) market with dual WAN Ethernet interfaces. And from the convergence angle, the results are definitely mixed. So long as the routers are used in a failover mode where the cable or DSL connection kicks in whenever the other fails, all seems to work fairly well for the tested applications.
However, it really seems that the load-sharing mode – where both paths are used if available – makes a lot more sense. It’s that old philosophy of not letting unused bandwidth just hand around when it could be used productively. In this mode, a few of the applications worked, but they found serious problems with other applications. We’ll dig into those in the next newsletter.
