Presently disclosed is a method and apparatus for monitoring and
diagnosing a content delivery network (CDN) by examining received content
elements that have been marked with one or more identifiers. Diagnosing
is accomplished by using all or part of one or more of the identifiers
associated with errored or corrupted content elements to determine which
network elements or connection paths are faulty. The identifiers may
contain content-, server-, or receiver-specific data that denotes,
respectively, the source of the content, the links associated with one or
more of the servers utilized in the network, and/or data associated with
the receiving computer system. Both marking and diagnosing may be
performed at any location within the CDN or at any host computer
connected to the CDN or receiver. The marking may also be dynamically
reconfigured in order to facilitate diagnosis.