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Type of Service in the Internet Protocol Suite (RFC1349)

IP.com Disclosure Number: IPCOM000002173D
Original Publication Date: 1992-Jul-01
Included in the Prior Art Database: 2000-Sep-12
Document File: 24 page(s) / 66K

Publishing Venue

Internet Society Requests For Comment (RFCs)

Related People

P. Almquist: AUTHOR

Abstract

Paths through the Internet vary widely in the quality of service they provide. Some paths are more reliable than others. Some impose high call setup or per-packet charges, while others do not do usage-based charging. Throughput and delay also vary widely. Often there are tradeoffs: the path that provides the highest throughput may well not be the one that provides the lowest delay or the lowest monetary cost. Therefore, the "optimal" path for a packet to follow through the Internet may depend on the needs of the application and its user.

This text was extracted from a ASCII Text document.
This is the abbreviated version, containing approximately 4% of the total text.

Network Working Group P. Almquist

Request for Comments: 1349 Consultant

Updates: RFCs 1248, 1247, 1195, July 1992

1123, 1122, 1060, 791

Type of Service in the Internet Protocol Suite

Status of This Memo

This document specifies an IAB standards track protocol for the

Internet community, and requests discussion and suggestions for

improvements. Please refer to the current edition of the "IAB

Official Protocol Standards" for the standardization state and status

of this protocol. Distribution of this memo is unlimited.

Summary

This memo changes and clarifies some aspects of the semantics of the

Type of Service octet in the Internet Protocol (IP) header. The

handling of IP Type of Service by both hosts and routers is specified

in some detail.

This memo defines a new TOS value for requesting that the network

minimize the monetary cost of transmitting a datagram. A number of

additional new TOS values are reserved for future experimentation and

standardization. The ability to request that transmission be

optimized along multiple axes (previously accomplished by setting

multiple TOS bits simultaneously) is removed. Thus, for example, a

single datagram can no longer request that the network simultaneously

minimize delay and maximize throughput.

In addition, there is a minor conflict between the Host Requirements

(RFC-1122 and RFC-1123) and a number of other standards concerning

the sizes of the fields in the Type of Service octet. This memo

resolves that conflict.

Table of Contents

1. Introduction ............................................... 3

2. Goals and Philosophy ....................................... 3

3. Specification of the Type of Service Octet ................. 4

4. Specification of the TOS Field ............................. 5

RFC 1349 Type of Service July 1992

5. Use of the TOS Field in the Internet Protocols ............. 6

5.1 Internet Control Message Protocol (ICMP) ............... 6

5.2 Transport Protocols .................................... 7

5.3 Application Protocols .................................. 7

6. ICMP and the TOS Facility .................................. 8

6.1 Destination Unreachable ................................ 8

6.2 Redirect ............................................... 9

7. Use of the TOS Field in Routing ............................ 9

7.1 Host Routing ........................................... 10

7.2 Forwarding ............................................. 12

8. Other consequences of TOS .................................. 13

APPENDIX A. Updates to Other Specifications ................... 14

A.1 RFC-792 (ICMP) ......................................... 14

A.2 RFC-1060 (Assigned Numbers) ...