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 144

Cloud Security. The Cloud-based CDN providers can combine CDN security with the
performance of cloud-based distributed infrastructures to keep their customers web-

sites both high performance and secure. The following aspects are some instances of
services the providers may provide in this area:

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1. Data Security: The Cloud-based CDN providers can apply and support advanced
standards and methods of security like PCI compliance, secure socket layer, and
digital rights management to offer the protection of their customers data.

2. High Availability: The providers offer the Cloud-based delivery of robust website
and application functionality in a high-performance manner.
3. Cloud DDoS Protection: It means the protection of websites via DDoS mitigation.
The CDN can support proactive monitoring and alerting.
4. Regulatory Compliance: The Cloud-based CDN enhance the CDN infrastructures
and services to meet the requirement of industrial and governmental standards for
protecting the customers

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' personal or nancial information.

Cloud-Based DNS. The Domain Name System (DNS) is a very important Internet
infrastructure that enables visitors to reach their website. DNS redirection has a very
crucial role to play in a Content Delivery Network, for it enables the users to get the
content they want from the available nearest surrogate server to reduce the response
time. Fetching the users

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preferential content form the optimal cache server can not
only improve the performance but reduce the chance of trafc congestion especially
during the rush time. Actually, DNS redirection is one of the mainly two techniques the
most CDN providers adopt in their architecture to achieve the aim of redirecting the
clients to the nearest surrogate server, the other is URL re-writing.

Cloud Storage. Taking advantage of Cloud Storage is a signi cant difference between

the Cloud-based CDN and the traditional CDN. For users, to Store, maintain, and
deliver a great mess of media, software, documents, or other digital objects is an
essential part of ensuring an outstanding online experience. By using the Cloud storage
functionality, the clients can effectively store a great amount of data and serve these
data to the users who need such data in different locations over the world reliably and
fastly. Furthermore, it is a very economical option. Though most Cloud-based CDN
providers in today s world allege their Cloud storage designed for reliability, scale or

speed, anyway they always mention the advantages of Cloud storage as more as
possible, there are also some limitations of the Cloud storage [ 6 ]:

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1. Due to some defective causes of the machines in the Cloud, the users data which

are stored in a Cloud Storage system can be corrupted and this would lead to the
situation that the Cloud Storage system returns incorrect results to the users.
2. The attacker may make a bug in the user

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' s programs to steal valuable information,

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s client to do Dos attacks or to spam.
3. In some rush time, because of the traf

even control the user

c jam, users might not be able to get access to
their data which are stored in the Cloud storage system accidentally.

The above disadvantages of Cloud storage may be extremely impossible, if the Cloud
Storage system is robust, well-management, well-designed etc. However, the rst

importance of the fact is that when these bad events happen, it will be very dif cult to