The Location Perspective

The Location perspective addresses the problems that arise when systems or system elements are physically distant from one another. If all elements are located in the same place, you can usually disregard this perspective.

Be aware, however, that the physical separation of elements may not always be immediately obvious. For example, many systems have disaster recovery sites that are physically distant from the main operational site or may rely on links to external, distant systems. Such an architecture presents a number of challenges that you should address through this perspective.

Desired Quality	The ability of the system to overcome problems brought about by the absolute location of its elements and the distances between them
Applicability	Any system whose elements (or other systems with which it interacts) are or may be physically far from one another
Concerns	Time zones of operation network link characteristics resiliency to link failures wide-area interoperability high-volume operations intercountry concerns (political, commercial, and legal) use of the public Internet physical variations between locations
Activities	geographical mapping estimation of link quality estimation of latency benchmarking modeling of geographical characteristics
Tactics	avoidance of widely distributed transactions architectural plans for wide-area link failure allowance for offline operation
Pitfalls	invalid (wide-area) network assumptions assumption of single-point administration assumption of one primary time zone assumption of end-to-end security assumption of an overnight batch period failure to consider political, commercial, or legal differences assumption that public networks are high-bandwidth, low-latency, and highly available assumption of a standard physical environment