Examining of Content Delivery Networks (CDNs) can be a way to allow mutual aid between CDNs in a scalable manner and to achieve better overall service, as perceived by end-users. A CDN is expected to provide high performance Internet content delivery through global coverage, which might be a barrier for new CDN providers, as well as affecting commercial viability of the existing ones. A Quality of Service (QoS) driven performance modeling approach is carried out for peering CDNs, in order to predict its user performance. The peering between CDNs upholds user perceived performance by satisfying the target QoS is shown. The methodology presented in this paper provides CDNs a way to dynamically redirect user requests to other peering CDNs according to different request-redirection policies. The model-based approach helps an overloaded CDN to return to normal by offloading excess requests to the peers. It also assists in making concrete QoS guarantee for a CDN. Overall this model undertakings to achieve scalability for a CDN in a user transparent manner.

Keywords: Content Delivery Networks (CDNs), Quality of Service (QoS). Request-redirection, Service Level Agreements (SLAs)