PPP protocol and Mac

IP addresses are addressing mechanisms at the TCP/IP network layer, Mac is the addressing mechanism of the 802.3/Ethernet link layer, They are different levels of things, not a side-by-side relationship. Think about whether the data is sent to the network cable or it turns into an electrical pulse. TCP/IP is not defined by the physical layer, the IP packet must be processed over Ethernet before it becomes an electrical signal. After the IP data is sent over Ethernet, Ethernet uses its own addressing mechanism to process Ethernet frames, that is, MAC addresses. PPP is in the WAN category, while Mac is in the LAN category. Different protocols are selected based on the actual situation and environment. The network structure supported by PPP can only be point-to-point, while Mac supports multi-point to multi-point.
Mac is used in Ethernet, and PPP is used remotely (for example, ADSL dialing is based on PPP ).
PPP is a Point-to-Point Protocol, logically connected to one device.

Therefore, no addressing is required. The destination address is the broadcast address. The first six bytes in PPP are the destination address.
The PPP frame format is as follows: Flag address crotrol protocol informaiton FCS flag The flag indicates the start and end of a PPP data frame. The FCS indicates frame verification. The address, control, protocol, and information fields that actually belong to the PPP data frame are included. Address indicates the PPP broadcast address. Address and control indicate that the message is a PPP packet, that is, the PPP packet header is ff03. PPP is encapsulated in different ways over Ethernet. It does not have the MAC address required by Ethernet frames. It implements point-to-point data transmission through its own negotiation process. For this type of Wan protocol, the frame structure is completely different from that of Ethernet, except for pppoe, because pppoe is based on Ethernet, while others such as PPP, FR, but not X.25. The packet capture graph of the PPP protocol and the packet capture graph of the FR protocol are attached.