# A Multipath Data-Scheduling Strategy Based on Path Correlation for Information-Centric Networking
## 3 System Design
### Multipath Transmission Mechanism  
As the IP network is the main form of the current Internet, it is obviously unrealistic to overthrow the existing network infrastructure to establish a new network architecture. In order to reduce deployment cost, the ICN architecture must be compatible with the existing IP network to fully utilize the IP infrastructure. In our previous research [34], we designed an ICN protocol stack that can achieve progressive development by adding an ID layer above the IP layer in the network layer, thus enabling the protocol stack to have ICN functions and features. In ICN, data, network devices, functions, network services and other network entities are all assigned a globally unique entity ID (EID). The EIDhas flat and non-semantic characteristics and can be numerical, a character or any other form of data. To implement the cooperation between an ID and IP, an important network component called a Name Resolution System (NRS) must be introduced in ICN to maintain the mapping relationship between the ID and IP. The NRS is deployed in a distributed manner. At the network layer, ID-based addressing and IP-based routing are decoupled: that is, network devices with the ICN protocol stack can initiate resolution requests to the NRS according to a specific ID to obtain the IP addresses bound to that ID, and the connection is then initiated to a specific ICN server or router based on IP routing rules. By using an EID as an identifier and an IP as a locator, the problems caused by the semantic overload of IP addresses can be completely solved. Despite the decoupling of addressing and routing at the network layer, the transmission efficiency and robustness of ICN are still limited by the shortest path transmission mode adopted by the underlying IP routing rules. As the number of flows increases, the congestion probability of the default shortest path increases. Once congestion or failure occurs in the default IP path, it is necessary to recalculate and update the routing rules. Typically, the convergence of routing algorithms usually takes tens of seconds or even several minutes. During this period, packet loss, throughput degradation and even session interruption may occur, which seriously affects the quality of experience. Therefore, the rigid shortest path transmission method has difficulty in meeting users' demands for high reliability and high bandwidth, especially in the scenario of massive content distribution in ICN. To improve the reliability and transmission efficiency, we have proposed a prototype system for multipath transmission based on the functions and characteristics of ICN [34]. Since ICN routers have a complete ICN protocol stack as well as caching and computing capabilities, it is a feasible solution to regard them as relay nodes to form relay paths between the two transmission endpoints. RON has experimentally proved that most of the transmission benefits can be obtained by constructing multiple single-hop paths between the sender and receiver [16]. Similarly, we utilize multiple ICN routers to construct multiple single-hop paths at both endpoints to enhance end-to-end transmission efficiency and robustness. Different from overlay routing, the proposed method implements multipath transmission by operating an IP address with an ID at the network layer instead of application layer. Specifically, the process of multipath transmission can be viewed as a service, and the corresponding multipath transmission service ID (MPSID) is generated. At network initialization, the ICN routers that can provide relay services register their IP addresses and MPSID mapping relationship in an NRS to form a set of candidate relay nodes. For a multipath connection, the data source can initiate the query to the NRS based on the MPSID to obtain the IP addresses of these relay nodes within the set. Then, several appropriate relay nodes can be selected from the set to build multiple relay paths, according to relay node selection strategy.