Evaluation of CDN’s Design

Evaluate the CDN by tracing the paths that matter: a local hit, a miss through a parent cache, and a request during an origin or edge failure. The architecture offers ways to meet the requirements; measurements and failure tests establish whether it does.

Requirements compliance

For each requirement, connect a design choice to its expected benefit and the condition that could limit it.

Performance

The following choices can reduce delivery time. Measure their effect separately for hits and misses:

• Proxy servers can serve frequently accessed objects from RAM.

• Geographic distribution can shorten network paths to users.

• Placement within ISPs or near internet exchange points (IXPs) can improve connectivity to demand.

• Routing selects an eligible proxy using the factors discussed earlier. Selection quality depends on current measurements.

• Local SSD or HDD storage can serve less popular content without an origin fetch. Whether it is faster depends on local load and the alternative path.