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rfc:rfc795

Network Working Group J. Postel Request for Comments: 795 ISI

                                                        September 1981
                          SERVICE MAPPINGS
                          ----------------

This memo describes the relationship between the Internet Protocol (IP) [1] Type of Service and the service parameters of specific networks.

The IP Type of Service has the following fields:

 Bits 0-2:  Precedence.
 Bit    3:  0 = Normal Delay,      1 = Low Delay.
 Bits   4:  0 = Normal Throughput, 1 = High Throughput.
 Bits   5:  0 = Normal Relibility, 1 = High Relibility.
 Bit  6-7:  Reserved for Future Use.
    0     1     2     3     4     5     6     7
 +-----+-----+-----+-----+-----+-----+-----+-----+
 |                 |     |     |     |     |     |
 |   PRECEDENCE    |  D  |  T  |  R  |  0  |  0  |
 |                 |     |     |     |     |     |
 +-----+-----+-----+-----+-----+-----+-----+-----+
 111 - Network Control
 110 - Internetwork Control
 101 - CRITIC/ECP
 100 - Flash Override
 011 - Flash
 010 - Immediate
 001 - Priority
 000 - Routine

The individual networks listed here have very different and specific service choices.

Postel [Page 1]

                                                        September 1981

RFC 795 Service Mappings

AUTODIN II

 The service choices are in two parts: Traffic Acceptance Catagories,
 and Application Type.  The Traffic Acceptance Catagories can be
 mapped into and out of the IP TOS precedence reasonably directly.
 The  Application types can be mapped into the remaining IP TOS fields
 as follows.
    TA    DELAY    THROUGHPUT    RELIABILITY
    ---   -----    ----------    -----------
    I/A     1           0             0
    Q/R     0           0             0
    B1      0           1             0
    B2      0           1             1
    DTR    TA
    ---   ---
    000   Q/R
    001   Q/R
    010    B1
    011    B2
    100   I/A
    101   I/A
    110   I/A
    111   error

Postel [Page 2]

                                                        September 1981

RFC 795 Service Mappings

ARPANET

 The service choices are in quite limited.  There is one priority bit
 that can be mapped to the high order bit of the IP TOS precedence.
 The other choices are to use the regular ("Type 0") messages vs. the
 uncontrolled ("Type 3") messages, or to use single packet vs.
 multipacket messages.  The mapping of ARPANET parameters into IP TOS
 parameters can be as follows.
    Type   Size   DELAY    THROUGHPUT    RELIABILITY
    ----   ----   -----    ----------    -----------
      0      S      1           0             0
      0      M      0           0             0
      3      S      1           0             0
      3      M      not allowed
    DTR   Type   Size
    ---   ----   ----
    000     0      M
    001     0      M
    010     0      M
    011     0      M
    100     3      S
    101     0      S
    110     3      S
    111       error

Postel [Page 3]

                                                        September 1981

RFC 795 Service Mappings

PRNET

 There is no priority indication.  The two choices are to use the
 station routing vs. point-to-point routing, or to require
 acknowledgments vs. having no acknowledgments.  The mapping of PRNET
 parameters into IP TOS parameters can be as follows.
    Routing   Acks    DELAY    THROUGHPUT    RELIABILITY
    -------   ----    -----    ----------    -----------
      ptp      no       1           0             0
      ptp      yes      1           0             1
    station    no       0           0             0
    station    yes      0           0             1
    DTR   Routing   Acks
    ---   -------   ----
    000   station    no
    001   station    yes
    010   station    no
    011   station    yes
    100     ptp      no
    101     ptp      yes
    110     ptp      no
    111     ptp      yes

SATNET

 There is no priority indication.  The four choices are to use the
 block vs. stream type, to select one of four delay catagories, to
 select one of two holding time strategies, or to request one of three
 reliability levels.  The mapping of SATNET parameters into IP TOS
 parameters can thus quite complex there being 2*4*2*3=48 distinct
 possibilities.

References


 [1]  Postel, J. (ed.), "Internet Protocol - DARPA Internet Program
      Protocol Specification," RFC 791, USC/Information Sciences
      Institute, September 1981.

Postel [Page 4]

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