# A Method for 5G-ICN Seamless Mobility Support Based on Router Buffered Data
## 3 Bdmm
### How to Achieve Seamless Mobility Support? As shown in Figure 1, assuming that the UE is initially connected to BS2, the UE continuously requests content published by the Content Server. Before the UE moves, the Content Server replies to the UE that the original packet forwarding path is Content Server \(\rightarrow\) R3 \(\rightarrow\) R2 \(\rightarrow\) R1 \(\rightarrow\) UPF1 \(\rightarrow\) BS2 \(\rightarrow\) UE. When the source BS (BS2) senses that the  
Figure 2: The process of packet forwarding by ICN router. UE is about to switch, the source BS (BS2) sends a Mobile Switching Notification to the uplink UPF (UPF1) (step 1). The Mobile Switching Notification carries the UE's identifier (EID0). The source UPF (UPF1) relays the Mobile Switching Notification to the uplink access router (R1). After receiving the Mobile Switching Notification, the access router (R1) adds/updates the local MEST-related entry, sets the \"EID\" field of the entry to the UE identifier (EID0) and sets the \"New NA\" to the default value (Step 2). At this time, the access router (R1) will buffer the packets destined for the UE. The buffer resource allocation strategy used by the access router (R1) is as described in Section 4. After the UE handover is completed, the source BS (BS2) senses the UE address change result, constructs and sends a Mobile Event Message to the uplink UPF (UPF1) (step 3). The Mobile Event Message needs to carry both the UE's identifier (EID0) and the address change flag. The address change flag can be identified by \"0\" and \"1\", indicating that the UE network address has not changed and that the UE network address has changed, respectively. The source UPF (UPF1) relays the Mobile Event Message to the uplinked access router (R1). If the access router (R1) receives the Mobile Event Message, it will determine its address change flag field. If this field is \"1\", it proves that the UE has changed its address (referring to the scenario where the UE switches from BS2 to BS3, the UE performs cross-UPF handover). Then, the access router (R1) will query the NRS for the latest network address of the UE based on the UE's identifier (EID0) carried in the Mobile Event Message (step 4). When the access router (R1) receives the response from the NRS, it learns the UE's latest network address (NA2) (step 5). Next, the access router (R1) updates the local MEST-related entry and sets the \"New NA\" field of the entry corresponding to the UE's identifier (EID0) to the UE's latest network address (NA2) to redirect the packet to the UE's latest location (step 6). The access router (R1) then releases the relevant buffered packets (step 7). The packet forwarding path is Content Server \(\rightarrow\) R3 \(\rightarrow\) R2 \(\rightarrow\) R1 \(\rightarrow\) R4 \(\rightarrow\) UPF2 \(\rightarrow\) BS3 \(\rightarrow\) UE. The access router (R1) also constructs a Mobile Path Notification to propagate to the Content Server's access router (R3) in the opposite direction to that of the original packet (step 8). The mobility path notification carries the UE's identifier and the UE's latest network address (NA2). After receiving the Mobile Path Notification, the intermediate router (R2) and the access router (R3) of the Content Server update the local MEST to achieve handover routing optimization (step 9). Finally, the optimized packet forwarding path is Content Server \(\rightarrow\) R3 \(\rightarrow\) R4 \(\rightarrow\) UPF2 \(\rightarrow\) BS3 \(\rightarrow\) UE. If the access router (R1) receives the Mobile Event Message with the address change field \"0\", this proves that the UE has not switched to changing the address (referring to the scenario where the UE switches from BS2 to BS1, the UE performs non-cross-UPF handover). The access router (R1) will delete the relevant entries corresponding to EID0 in the local MEST (step 10). After that, the access router (R1) will no longer buffer packets. At the same time, the access router (R1) releases the relevant buffered packets (step 11).