Hello,
1. Advantages: The processing of the header is simpler. If the checksum is incorrect, the data link layer discards the error frames. So the network layer can omit this step.
Disadvantage: Errors that cannot be detected at the data link layer may occur.
2. All routers along the transmission path of IP packets do not need this field. This parameter is required only for the destination host. In IPv6, the Next Header field is used to implement the function of the Protocol field in IPv4. (The value of the next header indicates the upper-layer protocol (such as TCP or UDP) to which the data following the basic header is delivered. When an extended header appears, this field specifies the information type of the extended header that follows the basic IPv6 header. )
3. Fragmentation and reassembly are time-consuming. IPv6 uses end-to-end fragmentation. End-to-end fragmentation removes this function from routers and moves it to hosts at the network edge, reducing routing overhead and enabling routers to process more data packets per unit of time. That is, the IP data forwarding speed on the network is greatly accelerated.
I hope this helps.