I. Network and Agreement Stack In SA (Independent Networking) 5G (NR) wireless network is usually divided into CU (Centralized Unit) and DU (Distributed Unit), where: DU (Distributed Unit) hosts the RLC, MAC, and PHY (Physical) layers, and CU (Centralised Unit) hosts the SDAP and PDCP layers; the user side of the network. The protocol stack is shown in the figure below:
II. the user data transfer to the end user (UE) to browse the Internet and download Web page content, for example, Internet browsers in the application layer using HTTP (Hypertext Transfer) protocol; assuming that the end user (UE) to host the Web page to be downloaded to the server to send the HTTP GET command, the application server will continue to use the TCP / IP (Transmission Control Protocol / Internet Protocol) packets to begin downloading the web content to the end user; the following header additions are required;
2.1 TCP Header Addition As shown in Figure 213, the TCP layer header is added with a standard header size of 20 bytes, but the size may be larger when optional header fields are included.The TCP header specifies the source and destination ports to identify higher-level applications. By default HTTP uses port number 80. the header also includes a sequence number to allow for reordering and packet loss detection at the receiver. The acknowledgement number provides a mechanism for acknowledging the packet, while the data offset defines the size of the header. The window size specifies the number of bytes the sender is willing to receive. Checksums allow for error bit detection in the header and payload. Emergency pointers can be used to indicate that certain data needs to be processed with high priority
2.2 IP Layer Header Addition Assuming IPv4 is used, the standard size of the header added at the IP layer, as shown in Figure 214, is 20 bytes (but the size may be larger when the optional header field is included).The IP header specifies the source IP address and the destination IP address, and the router uses the destination IP address to forward the packet in the appropriate direction. The version header field has a value of 4 when using IPv4, where the HDR (header) length field specifies the size of the header and the total length field specifies the size of the packet; DSCP (Differential Service Code Point) can be used to prioritize packets, and ECN (Explicit Congestion Notification) can be used to indicate network congestion. The agreement field specifies the type of content within the packet payload; TCP uses protocol number 6 for identification.
