Скачать или смотреть CCNA Explain PPP Encapsulation Point To Point Networking Point to Point

Point-to-Point Protocol (PPP) is a data link layer (Layer 2) protocol commonly used to establish a direct connection between two networking devices. PPP encapsulation is the method by which PPP frames are created and formatted for transmission over a network. PPP provides a standardized way of encapsulating various network layer protocols, such as Internet Protocol (IP), over point-to-point links.

The basic structure of a PPP frame includes a header and a trailer, with the payload in between. The header and trailer contain control information necessary for the PPP communication. Here are the main components of a PPP frame:

Flag Field: The frame starts and ends with a special flag sequence (01111110 in binary) to indicate the beginning and end of the frame.

Address Field (optional): In most cases, this field is not used, and the default value is 11111111, indicating a broadcast address. It's kept for compatibility reasons.

Control Field: It specifies control information. For PPP, the default value is 00000011.

Protocol Field: This field identifies the type of payload carried in the frame. For example, 0x0021 for IP (IPv4) and 0x0057 for IPX (Internetwork Packet Exchange).

Information Field (Payload): This is where the actual data (e.g., IP packet) is carried.

FCS (Frame Check Sequence): It is used for error detection, ensuring the integrity of the frame during transmission.

Flag Field: The frame ends with the same flag sequence.