# An Active Path-Associated Cache Scheme for Mobile Scenes
## 2 Related Work  
### Mobility of the ICN Network  
Mobility is a very important research issue in traditional IP networks. To support the mobility of IP networks, researchers have formulated various additional protocols [9; 10]. [PERSON] et al. proposed the session initiation protocol (SIP) [9], which is an application-layer control protocol that implements instant messaging. SIP can natively support terminal mobility. Each user has an associated SIP resolver. When the switch occurs, the terminal device re-registers its SIP-URL and IP to the resolver, and the content can continue to be obtained after a successful registration. [PERSON] et al. proposed the mobile IP (MIP) protocol, which is a network layer solution that supports host movement, allowing the terminal to retain its original IP address when it moves to other access points [10]. In the MIP protocol, each terminal is identified by a home address, and data are routed through a care-of address. When a mobile handover occurs in the terminal, the terminal needs to register the new address with the home agent to realize the binding of the home agent's forwarding address. During routing, the current location of the terminal can be found through the previous binding information to complete the forwarding of the data packet. Both SIP and MIP cores use a mapping mechanism to ensure that the network is not affected by movement. However, SIP only informs the latest address of the terminal after the handover, and data reliability cannot be guaranteed. MIP uses a tunneling mechanism. Each time a mobile node requests data, it needs to be transferred through the home agent. This method creates an inefficient triangular routing problem. These complex protocols use the patch method to solve the problem but avoid the fundamental problem of network architecture design. Therefore, the information center network supporting mobility has been widely proposed. In DONA [3], the mobile user sends a new search message at the current location. When the RH infrastructure receives the message, it will provide them with the closest copy of the information. Mobile publishers can log out of information and then re-register their information when the network location changes. To ensure that there is no outdated registration status, messages need to be forwarded all the way to layer 1 RH. This method will bring a lot of expenses, and the advertising information can be traced back to their new location. In NDN [11], when the user moves, it sends a new interest message from the current location to the object that has not received the information. These messages will be suppressed by the PIT (Pending Interest Table) on the first common CR (content route) of the two transmission routes (before and after the switch), and then the old location will receive the corresponding information object. In addition, when the content publisher moves, the FIB pointing to them must be updated, which requires re-publishing the information prefix it carries through the routing protocol. The above-mentioned high-mobility scenarios bring very high overhead. NDN uses the LFBL (Listen First, Broadcast Later) protocol to achieve mobility in opportunistic networks. In LFBL, there are a large number of interest packets. When the requested information receives interest, it listens to the wireless channel to confirm whether another node has sent a matching message. If no matching message is received, it sends a data message to the subscriber. PURSUIT considers various mobile situations [12]. Local user mobility is supported by multicast and caching. Specifically, information objects are multicast to multiple possible locations of mobile users. Local users receive content from nearby caches after switching. In addition, PURSUIT deals with global user mobility by modifying the forwarding function of the architecture. The mobility prediction can be used to reduce handover delay by caching the information requested by the user in the area where the user is expected to move after handover [8].