RFC 990 (rfc990) - Page 2 of 75
Assigned numbers
Alternative Format: Original Text Document
RFC 990 November 1986
Assigned Numbers
In the entries below the name and mailbox of the responsible
individual is indicated. The bracketed entry, e.g., [nn,iii], at the
right hand margin of the page indicates a reference for the listed
protocol, where the number ("nn") cites the document and the letters
("iii") cites the person. Whenever possible, the letters are a NIC
Ident as used in the WhoIs (NICNAME) service.
The convention in the documentation of Internet Protocols is to
express numbers in decimal and to picture data in "big-endian" order
[131]. That is, fields are described left to right, with the most
significant octet on the left and the least significant octet on the
right.
The order of transmission of the header and data described in this
document is resolved to the octet level. Whenever a diagram shows a
group of octets, the order of transmission of those octets is the
normal order in which they are read in English. For example, in the
following diagram the octets are transmitted in the order they are
numbered.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 1 | 2 | 3 | 4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 5 | 6 | 7 | 8 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 9 | 10 | 11 | 12 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Transmission Order of Bytes
Whenever an octet represents a numeric quantity the left most bit in
the diagram is the high order or most significant bit. That is, the
bit labeled 0 is the most significant bit. For example, the
following diagram represents the value 170 (decimal).
0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+
|1 0 1 0 1 0 1 0|
+-+-+-+-+-+-+-+-+
Significance of Bits
Similarly, whenever a multi-octet field represents a numeric quantity
Reynolds & Postel