Content Centric Network (CCN)

Content-centric networking is an innovative approach to networking that simplifies network use, improves performance and security, and enables a seamless, ubiquitous experience.

Content-centric networks enable the content itself to migrate where it is needed. In an interconnected world where people access digital information via continually shifting modes – moving from location to location, using multiple mobile devices, connecting through diverse networks – a content-centric approach allows them to access relevant, self-organizing information without cumbersome plumbing (i.e., firewalls, VPNs, and ad hoc synchronization protocols). The network can meet specific information needs with available resources, operating within appropriate administrative, performance, and security constraints.

This new approach enables network users to send and receive the right information, at the right place, at the right time – by any means available and regardless of underlying technology.

Working

The general proposal of content-centric networking recognizes that a great deal of information is produced once, and then copied many times. Therefore, it makes sense to distribute the copying and any related activities into the network's tree of equipment. In many cases, substantial storage is already available, and could be used more efficiently if it could recognize particular content and only keep one copy of it.

Since the network equipment is tree-shaped, it naturally scales content delivery to the size of the audience, and simultaneously reduces up-stream equipment to just the minimum needed to produce the content. As network service is built out, the content delivery naturally increases at the same time.

Content-centric networking uses a practical data storage cache at each level of the network to dramatically decrease the transmission traffic, and also increase the speed of response. The cache envisioned by CCN is a packet-level cache present at each node in the tree of network equipment not a complete copy of some media file. In that way, the worst case is that everything behaves as it does now: A consumer requests some data and it propagates through the network. However, the second time the data is requested, if it is still in the cache at some level, there are dramatic savings.

Architecture of CCN

There is a growing consensus in the recent literature that the central role of the IP address poorly fits the actual form of Internet usage. A typical user does not type IP addresses; he gets data or services by using application tools (e.g., Google, YouTube, Facebook, Skype), which operate on the basis of a description of the desired content. This means that users actually exploit the Internet in a content centric way; indeed, they are not interested in knowing from ”where” contents are provided, that is, the network layer has to be fed by IP addresses, which are used to ascertain from ”where” contents have to be taken. Therefore, there is a mismatch between the content-centric usage model of the Internet and the address-centric service model offered by the IP layer. Such a mismatch gives rise to several problems that would not exist if the network layer were a content-centric one.

  

Structure of CCN Node

CCN communication is driven by the consumers of data. There are two CCN packet types, Interest and Data. A consumer asks for content by broadcasting its interest over all available connectivity. Any node hearing the interest and having data that satisfies it can respond with a Data packet. Data is transmitted only in response to an Interest and consumes that Interest.1 Since both Interest and Data identify the content being exchanged by name, multiple nodes interested in the same content can share transmissions over a broadcast medium using standard multicast suppression techniques. Data ‘satisfies’ an Interest if the Content Name in the Interest packet is a prefix of the Content Name in the Data packet. CCN names are opaque, binary objects composed of an (explicitly specified) number of components (see Figure 4). Names are typically hierarchical so this prefix match is equivalent to saying that the Data packet is in the name sub tree specified by the Interest packet (see Section 3.2). IP uses this convention to resolve the hnet; subnet; host in hierarchical structure of IP addresses and experience has shown it allows for efficient, distributed hierarchical aggregation of routing and forwarding state while allowing for fast lookups. One implication of this matching is that interests may be received for content that does not yet exist – allowing a publisher to generate that content on the fly in response to a particular query. Such active names allow CCN to transparently support a mix of statically cached and dynamically-generated content, as is common in today’s Web.