  The proprietary nature of existing Content Delivery Networks (CDNs) means
they are closed and do not naturally cooperate. A CDN is expected to provide
high performance Internet content delivery through global coverage, which might
be an obstacle for new CDN providers, as well as affecting commercial viability
of existing ones. Finding ways for distinct CDNs to coordinate and cooperate
with other CDNs is necessary to achieve better overall service, as perceived by
end-users, at lower cost. In this paper, we present an architecture to support
peering arrangements between CDNs, based on a Virtual Organization (VO) model.
Our approach promotes peering among providers, while upholding user perceived
performance. This is achieved through proper policy management of negotiated
Service Level Agreements (SLAs) between peers. We also present a Quality of
Service (QoS)-driven performance modeling approach for peering CDNs in order to
predict the user perceived performance. We show that peering between CDNs
upholds user perceived performance by satisfying the target QoS. The
methodology presented in this paper provides CDNs a way to dynamically
distribute user requests to other peers according to different
request-redirection policies. The model-based approach helps an overloaded CDN
to return to a normal state by offloading excess requests to the peers. It also
assists in making concrete QoS guarantee for a CDN provider. Our approach
endeavors to achieve scalability and resource sharing among CDNs through
effective peering in a user transparent manner, thus evolving past the current
landscape where non-cooperative and distinct CDNs exist.
