## 3 Design Overview
### ID-Based Multipath Transmission Protocol  
The multipath transmission protocol in the MPTS-ICN architecture uses IP addresses for routing, so all messages are encapsulated as IP packets. The identifier is an important part of the ICN network. In order to be able to process the identifier in the network, the ID-related fields are added to the data packet header during the data packet design. The ID-related fields are located above the IP layer and belong to the network layer. The IP layer protocol mainly includes the IPv4 protocol and the IPv6 protocol. An unallocatedvalue (e.g., 0 \(\times\) 99) can be set for the \"Protocol\" field of IPv4 or the \"Next Header\" field of IPv6 to indicate that the IP header is followed by the ID header. Compared with IPv4, IPv6 has a larger address space and a smaller routing table, enhanced multicast support support for convection, and added support for automatic configuration and higher security. In this paper, the Identifier Protocol (IDP) is proposed based on IPv6 extension; Figure 2 shows the IDP protocol layer layout. IDP defines a set of rules and regulations to specify how to operate the IP address field of the packet according to the ID of the network layer under the separation of ICN identity and location [37]. In the network layer, the ID header is the last header of the extension header defined in ipv6. The ID header mainly includes the Next Header field, source ID type field, destination ID type field, source ID field, destination ID field, and so on. The Next Header field is used to specify which transport protocol the transport layer uses for the next processing of the data message. Transport layer protocols can be TCP (protocol field value 6), UDP (protocol field value 17), or custom ICN transport layer protocols (e.g., SeaDP [37]). Since the flat naming method is used to identify various entities (e.g., devices, data chunks, services, etc.) in the network, it is necessary to classify the IDs to adapt to different transmission scenarios. In the ID header, two fields are used to identify the source ID type and the destination ID type, respectively. In order to support multipath services at the network layer, we add a preference field to the ID header to identify multipath data packets. At the same time, we extend the function of IDP so that ICN routers can process multipath data packets. The design of the IDP protocol transforms the transmission mode of the network from IP-to-IP to ID-to-ID, so it can better support the realization of mobility and the network as a service. Ordinary IP routers cannot identify the ID header, the data packets will be forwarded in accordance with the IP layer protocol. ICN routers that support the IDP protocol can perform corresponding actions based on the defined rules and protocols according to the ID header field, such as deleting some carried addresses from the IP address field, changing the destination address, or performing in-network caching at the ICN router. For multipath transmission services, there are two main types of data packets: multipath content request packets and multipath content data packets. In this article, we use different types of IDs to handle multipath transfer services, as shown in Figure 3. First, the edge node queries the NAs of multipath service nodes through the service ID. In this paper, we use MPSID and send the MPSID query message to NMRS. After receiving the MPSID query message, NMRS queries the locally stored ID-NA mapping table, encapsulates the  
Figure 2: IDP Protocol Layer Layout. query result as an MPSID reply message and sends it to the edge node. Edge nodes establish a multipath forwarding information table according to query results and node selection strategy. At the beginning of data transmission, consumers use the consumer device ID as the source ID, the producer device ID as the destination ID, and the transport layer message contains the requested data chunk ID list to request multiple NDCs from the producer.