Figure 1 shows the fields in an LCP packet:
- Code - The code field is 1 byte in length and identifies the type of LCP packet.
- Identifier - The identifier field is 1 byte in length and is used to match packet requests and replies.
- Length - The length field is 2 bytes in length and indicates the total length (including all fields) of the LCP packet.
- Data - The data field is 0 or more bytes as indicated by the length field. The format of this field is determined by the code.
Each LCP packet is a single LCP message consisting of an LCP code field identifying the type of LCP packet, an identifier field so that requests and replies can be matched, and a length field indicating the size of the LCP packet and LCP packet type-specific data.
Each LCP packet has a specific function in the exchange of configuration information depending on its packet type. The code field of the LCP packet identifies the packet type according to Figure 2.