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Network Working Group Request for Comments:

795 SERVICE MAPPINGS ----------------

J. Postel ISI September 1981

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: Bit 3: Bits 4: Bits 5: Bit 6-7: Precedence. 0 = Normal Delay, 1 = Low Delay. 0 = Normal Throughput, 1 = High Throughput. 0 = Normal Relibility, 1 = High Relibility. Reserved for Future Use.

0 1 2 3 4 5 6 7 +-----+-----+-----+-----+-----+-----+-----+-----+ | | | | | | | | PRECEDENCE |D|T|R|0|0| | | | | | | | +-----+-----+-----+-----+-----+-----+-----+-----+ 111 110 101 100 011 010 001 000 Network Control Internetwork Control CRITIC/ECP Flash Override Flash Immediate Priority Routine

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

Postel

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RFC 795

September 1981 Service Mappings

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

THROUGHPUT ---------0 0 1 1

RELIABILITY ----------0 0 0 1

Postel

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RFC 795

September 1981 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 ---0 0 3 3 DTR --000 001 010 011 100 101 110 111 Size ---S M S M Type ---0 0 0 0 3 0 3 DELAY THROUGHPUT -------------1 0 0 0 1 0 not allowed RELIABILITY ----------0 0 0

Size ---M M M M S S S error

Postel

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RFC 795

September 1981 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 ------ptp ptp station station DTR --000 001 010 011 100 101 110 111 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. Acks ---no yes no yes DELAY ----1 1 0 0 Acks ---no yes no yes no yes no yes THROUGHPUT ---------0 0 0 0 RELIABILITY ----------0 1 0 1

Routing ------station station station station ptp ptp ptp ptp

Postel

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