2.2 Micro CDN: A Use Case for CCN
Micro CDN is a content delivery system. It is a net-
work of caches that serve content to the clients of the
network. Micro CDN offers two main distinctive fea-
tures. First, in-network high-speed caching features.
Second, a content based routing protocol based on
names. Its features are achieved by implementing a
CCN network.
Using CCN as the underlying architecture for Mi-
cro CDNs presents the following advantages:
• Caches for Every Protocol/Application. Cur-
rently, different CDN architectures target differ-
ent applications or protocols. For instance, a CDN
may offer services for live streaming of content or
static content delivery. With the use of CCN, dif-
ferent protocols and applications share the same
information at the networking layer. At network-
ing layer, a Content Name specifies the content
being transmitted instead of the protocol or any
IP address of the server destination. It means that
every caching protocol and application can benefit
of the in-network caching features of CCN.
• Fine-Granularity of Cached Content. Content
Names are hierarchically structured and made up
of components. Among the components, CCN
stores segmentation and version of the packet. It
means that CCN handles packets at a chunk level.
This can be beneficial for particular cases of con-
tent delivery. Such is the case for video on de-
mand services, where first chunks must be re-
trieved faster to start playback than the rest of the
chunks that can be incrementally downloaded.
• No More HTTP. Nowadays, most of the content
is transmitted through HTTP pages. Although the
HTTP protocol was not implemented for transmit-
ting content. For example, video streaming ser-
vices such as YouTube serve of HTTP and RTSP,
another protocol derived from HTTP, to deliver
the content. CCN permits to deliver content at the
network layer and completely suppress the over-
head caused by HTTP.
CCN based Micro CDNs may provide interesting
features for ISPs and networks in general. However,
there are still many parameters and studies to be car-
ried out. In this paper, we focus one specific param-
eter of Micro CDNs: the Gateways and its impact on
the caching features.
3 SINGLE GATEWAY OR
MULTIPLE GATEWAYS
A Gateway is a network node interfaced to connect
to other networks that use different communication
protocols.
In our case, the Gateways connect the Micro CDN
with the Internet. As Internet uses the TCP/IP com-
munication model and the Micro CDN uses CCN,
both networks are interfaced with Gateways. In a Mi-
cro CDN based on CCN, the content is not expected
to be produced in the CCN network. The CCN net-
work retrieves the information from the Internet. As
such, every time a content cannot be found in a cache,
it is demanded through a Gateway and subsequently
retrieved from the Internet.
Interfacing two networks through Gateways is a
challenging problem. In particular, mapping a CCN
name into an IP packet is a complicated task and it
depends on naming conventions (Shang et al., 2013).
However, this is not the only interesting point. As
CCN is a network of caches, different manners of im-
plementing Gateways will affect drastically the per-
formance of the Micro CDN. As a consequence, it is
essential to determine the effects produced by using
alternative Gateway designs to interconnect the CCN
and Internet networks.
In the Figure 1, we have explicitly said similar re-
quests are always retrieved from the same gateway.
We assume that the CCN network has a routing proto-
col associated. In this case, it is Open Short Path First
for Named data (OSPFN) (L. Wang, A. M. Hoque,
C. Yi, A. Alyyan, and B. Zhang, 2012; Moy, 1998)
OSPF is the default routing protocol for CCN. OSPF
finds the shortest path towards the requested node. As
such, similar requests are always to follow the same
routing protocol and will be guided through the same
nodes.
There exists an alternative manner to explain this
problem: using catalogs instead of gateways. A cat-
alog is a storage entity where all the demanded con-
tent is previously saved. Then, if we consider an au-
tonomous CCN network without connection with ex-
ternal networks, the catalogs can be interpreted as the
Gateways of the network. Single or Multiple Gate-
ways can be translated into Single or Multiple cata-
logs. Thus, every request is answered with one of the
catalogs. The problem becomes into assessing if hav-
ing one single catalog or multiple catalogs distributed
across the network are better choices.
For the analysis on the impact of Gateways into
caching features, we consider two types of Gateway
designs that are presented in the Figure 1: Single and
Multiple Gateways. The Single Gateways are repre-
Analyzing Gateways’ Impact on Caching for Micro CDNs based on CCN
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