usr/src/sys/netinet/if_ether.h

/*      if_ether.h      4.3     82/12/16        */

/*
 * Structure of a 10Mb/s Ethernet header.
 */
struct  ether_header {
        u_char  ether_dhost[6];
        u_char  ether_shost[6];
        u_short ether_type;
};

#define ETHERPUP_PUPTYPE        0x0400          /* PUP protocol */
#define ETHERPUP_IPTYPE         0x0800          /* IP protocol */

/*
 * The ETHERPUP_NTRAILER packet types starting at ETHERPUP_TRAIL have
 * (type-ETHERPUP_TRAIL)*512 bytes of data followed
 * by a PUP type (as given above) and then the (variable-length) header.
 */
#define ETHERPUP_TRAIL          0x1000          /* Trailer PUP */
#define ETHERPUP_NTRAILER       16

#define ETHERMTU        1500
#define ETHERMIN        (60-14)