The ISI Stack embodies the interrelationships between all the various components within the system and is based exclusively on the Interoperability Protocol (IP). To ISI there is only one system, just as there is only one mission for your organization.
The premise of the ISI Stack is that a eacher layer of a tower (or stack) is only as strong as the layers underneath. This essentially means that to avoid a "Tower of Pisa" problem, it is critical that best practices be used at each level of the stack so as to assure that layers further up the stack are properly supported. As you might imagine, it is thereby critical that the partner used to design, build, support, and maintain these converged systems be chosen very carefully.
Facilities - The foundation of the stack is Facilities. This includes Physical Access, Power, and Structured Cabling. Physical Access is detrimental to security - no system is secure if it can be physically accessed by an attacker. Battery backup, surge protection and other power considerations must be taken in to account to be sure system availability is maintained during short periods of power loss, and with spikes or dips in power. Finally, a good foundation of structured cabling is a must - all IP communications are only as reliable as the cabling on which they travel.
IP Infrastructure - The next order of importance is IP infrastructure. All computers on a network communicate via cabling that is attached to a switch. Your switching infrastructure must be reliable, fast, and secure in order to guarantee reliable network communication. A router is a device which interconnects two networks - usually your corporate network and the Internet. This device is of obvious importance and should be reliable and correctly configured and maintained. Finally, firewalls protect your network from intruders and should also be correctly configured to prevent security breaches.
Voice/Video Infrastructure - A business is made up of employees, and those employees are only as strong as their ability to communicate with each other. Reliable voice systems are vital to facilitate communication between employees internally and with the outside world. The appropriate voice systems, video systems and video/voice interfaces must be in place and correctly configured to guarantee reliable communication.
Storage Infrastructure - With all of the lower levels of the Stack in place, there must be a place to store digital data. For smaller companies, storage will take place at the server level. Larger companies may implement Storage Area Networks (SAN) or even Network Attached Storage (NAS) devices as a means for data storage. The requirements for each business are different and heavily dependent on several factors, so storage needs and solutions should be designed by professionals.
Server Infrastructure - Your network servers will be used to service the needs of your users. File shares, print shares, email (provided by a system like Microsoft Exchange), document sharing (provided by Microsoft SharePoint), and many other vital functions all rely on the ability of your servers to perform quickly and efficiently. Your server hardware, server operating system , and your server applications should all be correctly configured to work together for optimal performance.
User Devices - The user devices in your enterprise serve as the primary interface between your employees and your network systems. These devices could include desktop PCs, laptops, tablets, and smart phones. A user will only be as productive as his device allows him to be. This means that user devices should be fast, reliable, secure, and easy to use.
Services - After you've built a strong foundation of secure facilities, reliable structured cabling, fast and reliable structured routing and switching solutions, good server hardware, and quick and reliable user devices, you should be set... until something goes wrong. Even the best systems fail from time to time - and all systems require routine maintenance and monitoring.
