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vider and the CDN user, the contents were delivery
to a CDN provider. All the content files were copied
in the source server by the CDN providers. CDN
content were transmission to the edge cache server
by distribution module of CDN according to a
certain distribution means, shown as figure 2.
Figure 2: Content distribution.
The existing distribution method (Adrian J. 2006)
(S. S. H., 2003) does not support service
differentiation. All content objects as a whole, does
not distinguish the different server quality
requirements between different content. The
proposed method in this paper supports
differentiated Service and supports optimization for
each content object. A contract was signed between
the CDN provider and the CDN user in which
contain the service level requirements of each
content object. Different levels of service
corresponding to different number of copies. Every
content objects has the attributes of service level
requirements. How to distribute the contents of an
object with differentiated Service effectively is the
aim of this paper.
3 DIFFSERV-BASED CONTENT
DISTRIBUTION METHOD
CDN systems included source server, edge servers,
and the CDN management system. CDN
management system including the content
distribution related modules: service differentiation
module, content distribution control module, ant
search module, the delay measurement module,
shown as figure3. Content distribution module's
function is to distribute the content object to the edge
server node.
Delay measurement module is to measure the
network delay between the edge servers. If there are
N edge servers, n
(0 )nN<≤ points selected from
the edge servers randomly. The delay data were
statistics to get the delay date of other points to the n
points. The hierarchical diagram was obtained
through clustering these data. The pedigree chart was
transformed into a standard pedigree tree for a
heuristic algorithm of content distribution.
Figure 3: CDN system modules.
If there are n copies for one content, then n ants
climb out in ant colony search modules. For a set of
content objects, there may be a crowding
phenomenon, in which a lot of content was assigned
to one location, causing unbalance distribution.
However, this distribution unbalanced is necessary
from the view of all the point of positions. The
purpose content distribution network is to reducing
the delay, the best performance in a position to do
distribution copy is necessary. However, it is
necessary to balance distribution in the peer position
with the same effect. In another word, the balance is
necessary form the view of local area or the nearby
position. According to this principle, ants were
crawling, and sprinkle pheromone. Distribution
balance guided by the pheromone information.
The service level argument was obtained from
the service distinction module. The service level
information contains the number of copies for a
content object. The service level as an argument was
transmitted to ant search module. The ant searching
module run heuristic search in the space of edge
server based on the pedigree tree. Contents were
distribution to the optimal position based on the ant
search result. It is shown as figure 4.
A DIFFERENTIATED SERVICE BASED CONTENT DISTRIBUTION METHOD IN CDN
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