HINDLE . ME . UK
Seven Layer Model
Copyright © 2007
Integration Testing is an area that isn't carried out in many cases. It is this area that causes many technology companies problems, that become embarrassments. Integration Testing may appear to be unrequired at first sight. If all equipment passes the Type Approval stage then it works ! However, failure to test every systems, hardware and software in the same way that it will be used when the product is launched, will more often than not lead to trouble. In many cases after the customer has been exposed to malfunctioning systems.
Lets look at what at first may appear to be a simple system, a router connected to an ISDN2 line for accessing an Internet Service Provider.
The router has to communicate hardware and software messages to the NT1. The NT1 must communicate with the access mux equipment supplying the 'U' interface. The access mux will convert the 'U' interface into a 2M bit/s bearer, containing many other customer circuits. The 2M bit/s bearer is likely to be multiplexed into an SDH optical network. The optical network at the switch site will be returned to a 2M bit/s bearer, before being presented to the local switch. Assuming that the same company is also the ISP and the data point of presence is co-located to the local switch, another 2M bit/s bearer (now Q.931) will connect to a router in the data-POP, acting as the host for the service.
The example above is an everyday circuit used by many business for 64/128k bit/s access to the internet. There are a considerable number of component hops to link the customer to the data-POP. Each of these will have hardware and software build levels that will affect the operation, each will have a configuration build onto them via the local operator.
Integration testing of all this system is essential to make sure that it all works correctly by the time the customer is offered the service. The example hasn't even considered the interfaces to the customer database which is usually responsible for ensuring configurations are loaded for each part of the network, customer accounts are operational, correlating bills from the switch and the data-POP.
On paper this all appears to be common sense but as I said at the beginning all to often people assume that it will all work and just launch service without fully testing it. The example is a simple one in comparison to some and yet the number of points in it for miss-operation are significant.