Standard for the transmission of IP datagrams over experimental Ethernet networks
also
- std-42
Extracted elements (10)
Using the last eight bits of the Internet address host number as the Experimental Ethernet address is recommended as the easiest approach for address mapping, given that Experimental Ethernet uses 8-bit addresses and Internet addresses contain a host number portion.
Datagrams on the Experimental Ethernet may be longer than the general Internet default maximum packet size of 576 octets. Hosts should consider sending smaller datagrams to avoid unnecessary fragmentation at intermediate gateways when communicating with hosts not on the same Ethernet.
Some versions of Unix 4.2bsd use a trailer encapsulation method for better performance with the VAX virtual memory architecture. No host is required to implement it, and datagrams in trailer format must not be sent unless the sender has positive knowledge that the recipient can interpret them.
Unix 4.2bsd uses a non-standard Internet broadcast address with a host part of all zeroes rather than all ones, and either always or never uses trailers per interface depending on a boot-time option; both behaviors are expected to change in future releases.
If necessary, the data field should be padded to meet the Experimental Ethernet minimum frame size. This padding is not part of the IP packet and is not included in the total length field of the IP header.
The maximum length of an IP datagram sent over an Experimental Ethernet is 1536 octets. Gateway implementations MUST be prepared to accept full-length packets and fragment them if necessary.
Mapping from 32-bit Internet addresses to 8-bit Experimental Ethernet addresses is recommended by using the last eight bits of the host number part of the Internet address as the host's Experimental Ethernet address.
The broadcast Internet address (host part all binary ones) should be mapped to the Experimental Ethernet broadcast address, which is address zero.
As specified in Appendix B of RFC 791, the IP datagram is transmitted over the Experimental Ethernet as a series of 8-bit bytes.
IP datagrams are transmitted in standard Experimental Ethernet frames. The type field must contain the value 513 (1001 octal). The data field contains the IP header followed immediately by the IP data.