A Cluster-based Content Access Mechanism for Content-Centric Networking Kamrul Hasan, Chanhong Park, Minsub Lee, Seong-Ho Jeong Dept. of Information and Communications Engineering Hankuk University of Foreign Studies, Korea
[email protected], {chanhong, eminsub, shjeong}@hufs.ac.kr
Abstract —Data transmission from one device to another is increasing vastly, and therefore routing and communication between devices are becoming critical issues. Content-Centric Networking (CCN) is being recognized as a very useful technology for efficient and fast content delivery. In this paper, we propose an enhanced cluster-based content access mechanism which accelerates the rapid transmission of contents. The proposed architecture is based on the principles of CCN and incorporates a cluster-based approach for the better performance in terms of content retrieval delay and the traffic overhead compared to the basic CCN and other content delivery architectures. Keywords— Content-Centric Networking, Clustering
II. A CLUSTER-BASED ARCHITECTURE FOR CCN
I. INTRODUCTION
The proposed scheme mainly works based on the improvement of the existing cluster-based approach in CCN. The proposed scheme is divided into the following steps: - Formation of a cluster - Selection of a cluster head among the scattered routers - Cashing at each router and the cluster head - Transmission of Interest and Data Packets
As all the information becomes digital, hundreds of millions of new devices and people are coming online every year. Data demand is exponentially increasing, and global demand for IP data is nearing 30 exabytes per month. To meet all the new demands of the current Internet usage, a new paradigm, called Content-Centric Networking (CCN) [1], has emerged where the content queries and data are routed based on the content name [2]. Different types of naming has also been introduced for the content-oriented networking like hierarchical naming, flat naming and attribute naming schemes [3]. There are some other clustering-based approaches for mobility support [4] in CCN. In CCN, it is very important to provide efficient and fast content delivery to the users. In this paper, we propose an enhanced cluster-based content access mechanism which accelerates the rapid transmission of the content. The proposed architecture is based on the principles of CCN and incorporates a cluster-based approach for better performance in terms of content retrieval delay and the traffic overhead compared to the basic CCN and other content delivery architectures. The proposed scheme reduces the transmission of Interest Packets, which are query packets for searching the target content, without sending them repeatedly. This clusteringbased forwarding system reduces the time complexity and improves the efficiency of the overall CCN-based system. The
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overall procedure makes sure that how the capacity of CCNbased network will be ensured. This scheme does not use any additional equipment to maintain the movement of Interest Packets and catch the neighboring router information which ensures the cost effectiveness. When storing the information about the neighboring routers and clusters, intra-cluster caching capability is better than the other existing schemes in terms of the low content retrieval time. The rest of the paper is organized as follows. Section II proposes a cluster-based architecture for CCN. Section III describes the detailed operation of the proposed architecture. Performance analysis is given in Section IV. Finally we conclude the paper in Section V.
A. Formation of a cluster Clustering is the task of grouping a set of objects in such a way that objects in the same group (called a cluster) are more similar (in some sense or another) to each other than to those in other groups (clusters). In CCN, a cluster is a group of some routers which can share different types of information, e.g., the neighbouring routers’ addresses, their available storage, and so on. With the concept of cluster, we can reduce our computational and transmission overhead. To form the cluster, we use the algorithm No. 1 in [5]. During the formation of the cluster, all of the basic rules of CCN are applied. B. Selection of a cluster head The cluster head is the main object of the cluster. The most important task is done by the cluster head. To construct the cluster head, we use the algorithm No. 1 described in [4]. Every cluster constructs their cluster head using the same algorithm. As a result, we will get all the clusters and their head within a moment.
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C. Operation of Routers All end user terminals are directly or indirectly connected to a router. Every router stores the information about the end user terminals. When a user sends an Interest Packet towards its connected router, it will be stored in the router’s internal memory. If another user terminal sends the same content via an Interest Packet towards its connected router, the router first compares with the information in its internal memory. If a match found, then the Interest Packet is discarded. Otherwise, it will forward the Interest Packet. Ultimately, the previously requested content contained in Data Packets will arrive at the router, and the router will forward the Data Packets towards the second end user whose Interest Packet was discarded. In this way, the repeated transmissions of Interest Packets will be minimized. Since every router is a member of a cluster and every cluster has a cluster head, every router must store the information about the head.
B. Scenarios The proposed architecture operates in a CCN-based scenario which needs transmissions of Interest Packets and delivery of Data Packets as a response. For example, an end user-1 is connected with a router as shown in Figure 2. If the user-1 sends an Interest Packet toward its connected router, the router sends it to CH according to the rules as we described before. When any cluster head receives an Interest Packet (i.e., content request) from its neighboring router, it will be compared with its Pending Interest Table (i.e., its internal request table), if no match found, then a new entry for the Interest Packet is created in the table of the respective cluster head.
D. Operation of Cluster Heads It contains all the information of the corresponding cluster. Every connected router is directly connected to the cluster head. It stores all incoming and outgoing information, e.g., Interest Packets (content requests) and Data Packets (responses). It also stores the neighboring cluster heads’ addresses. III. OVERALL PROCEDURE
Figure 2. Connection between end users and routers
A. A proposed cluster-based architecture for CCN After completing the formation of a cluster by grouping neighboring routers, we now have the information about a cluster (C) and a cluster head (CH). Every cluster has its own address. Figure 1 shows that a cluster has been formed and there are six clusters named as C-1, C-2, C-3, C-4, C-5, and C6, and the names of six cluster heads are CH-1, CH-2, CH-3, CH-4, CH-5, and CH-6, respectively. Every cluster head is connected with its one hop neighboring cluster head and the members of its cluster. Figure 2 shows that initially, how the end user terminal is handled by its connected router within a cluster. The overall procedure can be explained by the figures.
Then it is forwarded to its one hop neighboring cluster head and the same procedure is performed by all other cluster heads. If a match is found, it indicates that either this Interest Packet is forwarded or Data Packets of the connected routers must contain the target information. Thus, the cluster head instantly forwards an Interest Packet to its connected router. If the router contains the requested content then the responding Data Packets are delivered in the reverse path. Otherwise, Interest Packets are forwarded. Figure 2 shows that an Interest Packet (IP) is sent to its connected router and the router forwards it to its cluster head. When the cluster head receives the Interest Packet then automatically the packet will be compared with the information in its own PIT. If a match is found, then the cluster head forwards this Interest Packet towards its own cluster members. Then the corresponding content within the cluster is forwarded by Data Packet (or Data Reply (DR) in the figure) in the reverse path. At the same time user-2 sends the same Interest Ps to its connected router. This time this Interest Packet is not forwarded because the cluster head already has the DR packets. Every cluster follows this sequence to reply to the content request. The first scenario describes the presence of Interest Packet in the connected router cluster. If the Interest Packet is absent in the connected router cluster, then the cluster head sends the Interest Packet to its one hop neighboring cluster head. As shown in Figure 1, due to the absence of Interest Packet, CH-1 sends it to its one hop neighboring CH-2, CH-3, and CH-4. After receiving the Interest Packet 1 (IP-1), three cluster heads perform their responsive task as mentioned earlier. If any
Figure 1. A proposed cluster-based architecture for CCN
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match is found, DRs will be sent in the reverse path. Otherwise, IP-1 is forwarded to the next one hop cluster head. Figure 2 shows that CH-3 and CH-4 forward IP-1 to its one hop neighbors CH-5 & CH-6 and CH-3 & CH-5, respectively. But CH-3 rejects the IP-1 because IP-1 already contains the same request in its storage. In the same way, other CHs also reject the duplicate request. CH-5 and CH-6 perform their respective task and reply along the reverse path. IP-1 will be forwarded until getting DRs along the reverse path. If CH-5 and CH-6 are unable to reply, they also forward it to their one hop neighbor. This scenario is not shown in Figure 2, but in real life, it is possible to forward. If it is not possible to forward the IP-1, then the cluster head sends a reply to inform that the requested content cannot be found. This message is forwarded along the reverse path. When the sender gets the reply, it will be understood that the Interest Packet is absent in the current network.
Figure 3. Number of Interest Packets (IP) for content access V. CONCLUSION
IV. PERFORMANCE ANALYSIS
This paper proposed an enhanced cluster-based content access mechanism which accelerates the rapid transmission of the content. The proposed architecture is based on the principles of CCN and incorporates a cluster-based approach for the better performance in terms of content retrieval delay and the traffic overhead compared to the basic CCN and other content delivery architectures. We showed that the proposed approach works better than the existing architecture, especially in the large-scale network.
Our proposed procedure maintains the basic rule of CCN. CCN works on the individual routers but the proposed approach is a cluster-based procedure. Therefore, our scheme will significantly reduce the number of transmitted Interest Packets the delay of content delivery and increase the overall performances. Suppose that there are N routers in an area. Every router has M neighboring routers. Thus, the total number of Interest Packets needed is M x N. Let’s apply the clustering procedure in the area. It is assumed that the number of clusters is m and there are n neighboring clusters. Thus, the total number of Interest Packets is m x n. For example, there are 60 routers in an area and there are 5 neighboring routers connected to each router. In this case, on average 300 Interest Packets are needed for CCN operation. On the other hand, using the clustering technique, we have at most 10 clusters and on average 3 clusters will be the neighboring clusters of each cluster. In this case, only 30 Interest Packets will be needed, which is ten times less than the previous approach. In the same way, other computation cost will also be reduced. Due to the intra-cluster catching, the access time of data reply will be reduced. Using the technique at each router and cluster head, the same cluster can reply in an efficient manner. For this reason the overall performance is increased. Figure 3 shows the number of Interest Packets needed for requesting the target content in the CCN environment. This analysis was performed considering the worst case of response of Data Packets. But in the best and average cases, the performance is even better than the basic CCN. In this clusterbased system analysis, it is assumed that every cluster contains five routers.
ACKNOWLEDGMENT This research was funded by the MSIP (Ministry of Science, ICT & Future Planning), Korea in the ICT R&D Program 2014. REFERENCES [1] [2] [3] [4] [5]
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