The Protocol field indicates the type of payload packet: 0xC021 for LCP, 0x80xy for various NCPs, 0x0021 for IP, 0x0029 AppleTalk, 0x002B for IPX, 0x003D for Multilink, 0x003F for NetBIOS, 0x00FD for MPPC and MPPE, etc. PPP is limited, and cannot contain general Layer 3 data, unlike EtherType.
the protoCol Field iNdicaTeS The Type of paYLOaD packet: 0Xc021 For Lcp, 0x80xy for vARious NcPs, 0x0021 for ip, 0x0029 AppLetalk, 0X002b for ipx, 0X003D foR Multilink, 0x003F for netbiOs, 0x00fD fOr mppc and MpPe, etc. ppP is limIteD, anD caNNot COnTain GeNEral layER 3 Data, Unlike etherType.