# A Dual-Connectivity Mobility Link Service for Producer Mobility in the Named Data Networking
## 3 Related Work  
According to [6], producer mobility schemes can be categorized as anchor-based schemes and anchorless schemes. Anchor-based schemes use an anchor to maintain the location information of the mobile producer. The anchor has been referred to as a local controller [8], a content router [9], an immobile anchor [10] and a home repository [11]. Depending on the proposed schemes, the anchor either stores the content, forwards Interests, or fetches the content from the producers. The interaction between the anchor and the producers requires extra signaling overhead and may lead to unnecessary triangle routing problems. As a result, it could limit the advantages of NDN, such as multipath communication and its robustness to single point failure.  
In the latter category, the mobile producer takes charge of reporting its movement to the network without an anchor. In [12], the previous NAR (pNAR) buffers incoming Interests until receiving a special Interest from the producer. The pNAR then forwards the buffered Interests to the producer. However, when the intermediate NDN router receives the buffered interests from the pNAR, it may discard the buffered interests to avoid routing loop. This is because the intermediate NDN router already has the PIT entry for the same content name. Therefore, before the FIBs at NDN routers on the forwarding path are updated, pNAR must set the bit in the buffered interests indicating that these interests have been re-transmitted. In the anchorless mobility scheme [15], a Temporary FIB (TFIB) is introduced at each NAR to help keep track of the movement of the producer. In LBMA [16], after moving to a new NAR, the producer notifies the corresponding consumer of its current location information using the modified Interest and Data packets. This causes a dependency between the original NDN forwarding plane and the mobility features. In MAP-ME [21], mobile producers use Interest update messages to update the FIB entries in an attempt to minimize their unreachability. T-Move [22] supports producer mobility by using FIB entry updates and pushing contents to the router nearest the producer. These solutions may break the simple architecture principle of NDN [17] as these solutions require some modifications to the existing parts of the NDN architecture, such as the FIB and packet format of interest message.  
There are several proposals [23; 24; 25] put forth to support producer mobility by using an optimal caching configuration. As these caching methods are determined by the heuristic method, the producer mobility may not be guaranteed. The concept of the heuristic solutions here is similar to the predictive mode of Fast Mobile IPv6 (FMIPv6) [26]. Therefore, it can be said that the heuristic solutions have same disadvantages of the predictive mode of FMIPv6 when the mobile node's movement is incorrectly predicted. The relative signaling cost could increase as the probability of prediction accuracy becomes inaccurate [27]. In addition, if the mobile node moves into unpredicted domain or the handover is not performed immediately, large packet loss and handover latency may occur [28].