An Overview of Cloud Based Content Delivery Networks: Research Dimensions and State-of-the-Art - Transactions on Large-Scale-Data-and Knowledge-Centered Systems XX - page 143

Local caching: fetches the content for the customer from the origin server and stores
it in a local server closer to the customer. This technique helps in signi

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cantly

reducing the response time.

Request redirecting: plays a very pivotal role in the performance of a CDN service
as it redirects the customer

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' s request to the nearest cache server.

4 CCDNs Architecture and Services

Technically, architectures of CCDNs in existence are various in terms of the correlation
between CDN and Cloud. For instance, some CCDNs adopt the cloud-based store as
their origin server. In this kind of CCDNs, the general mechanism is similar as the
traditional CDNs

'

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cally, in this kind of CCDNs [ 4 , 14 , 15 , 23 , 39 ] the functionality of master node is
managing, monitoring and provisioning slave nodes on demand. The slave nodes
combine the functions of POP servers. The data is replicated in the master nodes which
act as the origin server. When the slave node has to get some contents users require, it
only needs to communicate with the master node to fetch the content. A typical CCDN
architecture is presented in Fig. 3 . As depicted in the Fig. 3 , the POPs are distributed
across multiple cloud providers while the master node/origin server is responsible to
orchestrate the entire CDN functionality. Based on demand from various geographical
locations and QoS constraints, the master node will

. Other architecture includes Master/Slave mechanism [ 4 ]. Speci

re new slave POP nodes in close

proximity to origin of user requests.
Cloud-based CDNs offer a large number of additional services compared to tra-
ditional CDNs. These include:

Fig. 3. Cloud CDN typical architecture