# A Novel Multipath Transmission Scheme for Information-Centric Networking
## 3 Design
### Overview of Transmission Process  
In ICN, network services are treated as a kind of network entity and are labeled with identifiers, such as multicast services [40] and storage services [34]. Inspired by this, we consider multipath transmission as a kind of service and assign the corresponding MPSID. Some ICN in-network routers need to register the relationship of their NAs to the MPSID with the NRS so that they can be addressed by other network devices. These ICN routers are regarded as relay nodes for end-to-end transmission, which can reroute traffic sent by the data source to the destination. Therefore, in addition to the default shortest path, the data source can use multiple suitable relay ICN routers to construct multiple parallel single-hop relay paths between the data source and the receiver. Figure 2 shows the process of the proposed multipath transmission scheme. When the ICN routers (R2 and R4) supporting the multipath transmission service go online, they will register the mapping between its NA and MPSID with the NRS (step 1). After the connection between the two sides is established, the data source starts transferring local data chunks. Each chunk to be transferred is segmented according to the Maximum Transmission Unit (MTU) and an ICN header is added to form an ICN data  
Figure 2: An overview of the multipath transmission process. packet. The data source can transmit these packets using the default path; in addition, if a higher bandwidth is required, the data source can mark a multipath transmission label in the preference field of these ICN data packets according to the application requirements, and then send packets to the corresponding edge router (here, R5) (step 2). For security reasons, the NAs of in-network ICN routers should not be exposed to devices outside the ICN network area, so the query operation to the NRS is initiated by the edge node. When receiving the first marked data packet of the first chunk during this transmission, R5 initiates a query operation to the NRS according to the MPSID to obtain the NA list (here, NA2 and NA4). During the whole end-to-end transmission, the operation of initiating a query to the NRS by the edge router only happens once and the subsequent query operation is not needed (step 3). According to the node selection strategy, R5 selects several suitable NAs from the NA list and adds them to the selected node set. Then, R5 changes the destination NA of the data packet to one of the selected NAs and caches the network address translation information locally. It is worth noting that the granularity of data scheduling is chunk, so segmented packets of the same chunk will be processed in the same way. Since IPs can be used as NAs in this paper, these data packets will be transmitted to the corresponding relay node (R2 or R4) through an IP routing function (step 4). When receiving the first data packet of a chunk, the relay ICN routers (R2 or R4) will send a name resolution request to the NRS according to the destination ID to obtain the NA of the receiver device. It should be noted that this query operation only occurs when the first data packet of a chunk is received. The relay router will form NA translation rules locally. When subsequent packets of the same chunk arrive, their destination NAs are automatically changed according the translation rules (step 5). Finally, the relay ICN router (R2 or R4) modifies the destination NA of the data packet to the NA of the receiver device and forwards it (step 6). In contrast to some overlay routing methods, our multipath transmission scheme is implemented based on the MPSID at the network layer rather than the application layer. In the process of multipath transmission, three kinds of IDs are mainly involved, which are the IDs of chunks to be transmitted, the ID of the receiver device, and the MPSID. The source ID and destination ID of the data packet are the chunk ID and the receiver device ID, respectively.