# Data Naming Mechanism of LEO Satellite Mega-Constellations for the Internet of Things
## 3 Design of Data Naming Mechanism
### Data Naming Mechanism  
This paper proposes a data naming mechanism that integrates hierarchical, multicomponent, and flat hashing called ICN-HMcH. The purpose of this mechanism is to integrate the characteristics of hierarchical, multicomponent, and hash flat names into a multilayered structure using prefix-based hierarchical thinking and IoT business attributes based on the LEO satellite constellation. Figure 11 shows the top-down multilayer naming structure of ICN-HMcH, which uses a four-layer structure to identify the semantics of different applications:  
1. Root prefix layer: This layer defines the flags for publishing information and multi-source information request flags. 2. Task-type layer: This layer defines the data namespace in the LEO IoT. Two types of data namespaces are proposed using the executed request: one retrieves data and performs content extraction on demand; the other routes and forwards or caches the transmitted data. 3. Service-type layer: This layer defines the types of services to be performed, such as data transmission, video, or voice. 4. Network functions and local node identification layer: This layer identifies the network functions used to allow data retrieval from multiple sources. Figure 10: Forwarding process at a satellite node. In addition to the multilayer design, the ICN-HMcH naming mechanism uses a set of attribute value pairs at each level to describe different content/service attributes, such as operation types and security. Some of these names must exist, and some are optional or can be dynamically generated. The attribute value plays an important role in strengthening content security, protecting user/communication privacy, etc., and can be saved as a keyword. According to the ICN-HMcH top-down multilayer naming structure, the embedded naming mechanism of the data transmission process is introduced. For the data transmission of the LEO mega constellation of the IoT, according to the function, each node can be divided into the following categories:  
1. Content provider or publisher node. Such nodes inform other nodes of their own data and issue content update notifications in a timely manner when the content changes. In addition, for the requester node to request these data, the publisher node performs the data source function and provides the download source. 2. Forwarding node. Typically, an area contains at least one such node, and its location can relate to most nodes in the area to provide an efficient information summary and the function of obtaining content information. For example, each satellite can act as a central node, particularly when switching satellites. 3. Requester node. When a large number of data must be acquired and learning distribution information in the network is also required concurrently, the requester node sends a content information request to the forwarding node. The forwarding node obtains and analyses the response message; obtains the different content blocks and its node information; and then transmits the data concurrently in multiple channels. Additionally, the node requests different content blocks from different nodes concurrently. You can download and aggregate to obtain the required content. Concurrently, when the requester node obtains new data, it can publish the locally stored data information as the publisher node so that other requester nodes can directly access and download from this node. Therefore, data transmission can be divided into three steps: information publishing, content source information acquisition, and block data request downloading. In Step 1 (information publishing), the content provider nodes in the network must publish to the forwarding node in time based on the content cached locally to make full use of the distributed storage of data. The forwarding node determines the latest state of the data distribution in the network in real time, and when processing various data requests, it searches for the optimal data source to respond to user requests according to the content distribution and network topology.