Page 785 - (ISC)² CISSP Certified Information Systems Security Professional Official Study Guide

hosted applications.

SDN offers a new network design that is directly programmable from a
central location, is flexible, is vendor neutral, and is open-standards

based. Using SDN frees an organization from having to purchase
devices from a single vendor. It instead allows organizations to mix
and match hardware as needed, such as to select the most cost-
effective or highest throughput–rated devices regardless of vendor.
The configuration and management of hardware is then controlled

through a centralized management interface. Additionally, the settings
applied to the hardware can be changed and adjusted dynamically as
needed.

Another way of thinking about SDN is that it is effectively network
virtualization. It allows data transmission paths, communication
decision trees, and flow control to be virtualized in the SDN control
layer rather than being handled on the hardware on a per-device basis.

Content Distribution Networks

A content distribution network (CDN), or content delivery network, is
a collection of resource services deployed in numerous data centers
across the internet in order to provide low latency, high performance,
and high availability of the hosted content. CDNs provide the desired

multimedia performance quality demanded by customers through the
concept of distributed data hosts. Rather than having media content
stored in a single location to be transmitted to all parts of the internet,
the media is distributed to numerous locations across the internet.
This results in a type of geographic and logical load-balancing. No one
server or cluster of servers will be strained under the load of all
resource requests, and the hosting servers are located closer to the
requesting customers. The overall result is lower-latency and higher-

quality throughput. There are many CDN service providers, including
CloudFlare, Akamai, Amazon CloudFront, CacheFly, and Level 3
Communications.

While most CDNs focus on the physical distribution of servers, client-
based CDN is also possible. This is often referred to by the term P2P
(peer-to-peer). The most widely recognized P2P CDN is BitTorrent.