IEN-72
Multiplexing Protocol
Jonathan B. Postel
23 January 1979
Information Sciences Institute
University of Southern California
4676 Admiralty Way
Marina del Rey, California 90291
(213) 822-1511
IEN-72 J. Postel
ISI
23 January 1979
Multiplexing Protocol
Introduction
This Multiplexing Protocol is defined to allow the combining of transmission units of different higher level protocols in one transmission unit of a lower level protocol in packet-switched computer communication in the environment of an interconnected set of computer networks. This protocol assumes that the Internet Protocol [1] is used as the underlying protocol.
Format
0 15 16 31
+--------+--------+----------------+
! ! ! !
! Zero !Protocol! Length !
! ! ! !
+--------+--------+----------------+
Multiplexing Header Format
Fields
Zero is always zero.
Protocol is the number of the following lower level protocol.
Length is the length in octets of the following protocol block.
Postel [page 1]
23 January 1979
Multiplexing Protocol IEN-72 Example
Example
0 15 16 31
+--------+--------+--------+--------+
! Zero !Protocol! Length !
+--------+--------+--------+--------+
! a transmission unit !
! of some protocol !
+--------+--------+--------+--------+
! Zero !Protocol! Length !
+--------+--------+--------+--------+
! a transmission unit !
! of some protocol !
+--------+--------+--------+--------+
! Zero !Protocol! Length !
+--------+--------+--------+--------+
! a transmission unit !
! of some protocol !
+--------+--------+--------+--------+
Multiplexing Protocol Concept
[page 2] Postel
23 January 1979 IEN-72 Multiplexing Protocol
Example
0 15 16 31
+--------+--------+--------+--------+
! Zero !datagram! Length = 16 ! ----+
+--------+--------+--------+--------+ !
! source socket ! dest. socket ! !
+--------+--------+--------+--------+ !
! length = 8 ! checksum ! !
+--------+--------+--------+--------+ !
! data ! !
+--------+--------+--------+--------+ !
! data ! !
+--------+--------+--------+--------+ <---+
! Zero ! TCP ! Length = 28 ! ----+
+--------+--------+--------+--------+ !
! source port ! destination port! !
+--------+--------+--------+--------+ !
! sequence number ! !
+--------+--------+--------+--------+ !
! acknowledgment number ! !
+--------+--------+--------+--------+ !
!offset control! window ! !
+--------+--------+--------+--------+ !
! checksum ! urgent pointer ! !
+--------+--------+--------+--------+ !
! data ! !
+--------+--------+--------+--------+ !
! data ! !
+--------+--------+--------+--------+ <---+
! Zero !datagram! Length = 12 ! ----+
+--------+--------+--------+--------+ !
! source socket ! dest. socket ! !
+--------+--------+--------+--------+ !
! length = 4 ! checksum ! !
+--------+--------+--------+--------+ !
! data ! !
+--------+--------+--------+--------+ <---+
Multiplexing Protocol Example
Protocol Application
The major use of this protocol is to allow several transmission units from differing (or the same) higher level protocols to be combined into one transmission unit of a lower level protocol.
Postel [page 3]
23 January 1979
Multiplexing Protocol IEN-72 Protocol Number
Protocol Number
This is protocol 18 (22 octal) when used in the Internet Protocol. Other protocol numbers are listed in [2].
[page 4] Postel
23 January 1979 IEN-72 Multiplexing Protocol
References
References
[1] Postel, J., "Internetwork Protocol Specification – Version 4,"
IEN-54, USC-Information Sciences Institute, September 1978.
[2] Postel, J., "Assigned Numbers," USC-Information Sciences
Institute, RFC-750, NIC-45500, September 1978.
Postel [page 5]