# Flooding Message Mitigation of Wireless Content Centric Networking for Last-Mile Smart-Grid +
## 2 System Model and Related Work  
### System Model  
Content Centric Network does not require IP addressing to access data in a specific network. Instead of IP address, CCN uses Content-prefix and Face information. The content-prefix is unique content identifier that can be created by naming rules. For example, in smart grid network, it can be modeled by URI structures as following application parameters as DLMS data structure [3]. (e.g., 'MeterType/MeterID/peakLoadData/'). A Face is logical communication interface name of content-prefix that can be a realized as MAC address, network card number, etc. In a CCN, each device maintains three types of table as Forwarding Information Base (FIB), Pending Interest Table (PIT), and Content Store (CS). These tables are updated by exchanging Content-prefix Announcement (CA), Interest, and Content packet.  
The FIB consists of content-prefix and Face(s) information. When a device receives Content or Interest packet, then content-prefix and related in/out bound Face are recorded to FIB. The PIT is updated by Interest packet. If a device generates or receives an _Interest_ packet, then related content-prefix and in/out bound Face(s) are inserted to PIT table. The CS is a cache list table that is maintained eventually during exchanging Content packet. When a device received Interest packet, device lookups the CS to find a related content. If the device has the related Content, the Interest packet flooding shall be stopped, and Content packet is transmitted toward content requester through outbound Face. This means that content packet can be transmitted by each device instead of content originator to reduce the end-to-end transmission overhead. Thus, TOP-CCN provides in-network caching functionality to achieve efficient content delivery in LMN [1]. The CCN-based smart grid network can eliminate IP complexity problems. Thus, CCN may improve LMN communication efficiency by using simple architecture, temporal data caching and name-based discovery functions [7; 8; 9; 10; 11]. Also, CCN can reduce transmission overhead by the in-network caching strategy. In a CCN smart grid environment the content packet is stored to CS of the device to ensure content cache effect.  
Figure 1 shows a Wireless CCN architecture for Smart Grid LMN. In traditional AMI system, Data Concentrate Unit (DCU) is located in each LMN. In our system model, DCU or gateway uses IP stack and non-IP based CCN stack for packet routing between different network domain between back-end communication network and CCN based LMN. If a gateway received data sending request of Meter#2 from IP server and has to prepare related data collection and sending. To collect requested data, gateway broadcasts an CCN Interest packet to network. Interest packet is broadcasted to network and each meter device updates PIT table using received requested content name and Face information as Interest sender's MAC address. When a device finds a requested content from its CS, then content will be transmitted to related Face(s) in a FIB. To reduce interest packet broadcast, each CCN meter device can announce its unique content list by using Content-prefix Announcement (CA) packet. If the device receives CA, CA information and outgoing Face to contents originator is recorded to FIB. If a device already knows face information of requested interest packet, then interest packet is transmitted to dedicated Face(s). The Content packet is an actual data packet related to interest packet. The FIB  
Figure 1: System model of Content Centric Networking (CCN)-based Last-mile Smart Grid Network for Advanced Metering Infrastructure.  
can be updated by various approaches such as proactive CA, reactive content discovery schemes, or manual setup by network managers [11]. As describe above, IP address is not utilized in a CCN because content data can be stored in various location in a local network and IP address can be replaced to specific content prefix.