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1.2.- The specifications  

Differentiated service architecture was outlined in 4 documents originated from the IETF (Internet Engineering Task Force) named RFC (Request For Comments). The documents are: 
K. Nichols, S. Blake, F. Baker, D. Black, "Definition of the 
Differentiated Services Field (DS Field) in the IPv4 and 
IPv6 Headers", RFC 2474, December 1998. 

M. Carlson, W. Weiss, S. Blake, Z. Wang, D. Black, and 
E. Davies, "An Architecture for Differentiated Services", 
RFC 2475, December 1998 

J. Heinanen, F. Baker, W. Weiss, J. Wroclawski, "Assured 
Forwarding PHB Group.", RFC 2597, June 1999. 

V. Jacobson, K. Nichols, K. Poduri, "An Expedited Forwarding 
PHB." RFC 2598, June 1999. 
 
After these RFCs were published in december 1998 and june 1999 other RFCs have been published by IETF about differentiated service; these are RFC 2836, 2983, 3086, 3140, 3246, 3247, 3248, 3260, 3289 and 3290. Because the packet field to be marked for differentiated service was defined in RFC 2474, the differentiated service architecture in RFC 2475 and the first two differentiated service behaviors were defined in RFC 2597 and 2598, we are going to concentrate in these four documents.
 
To follow, we are going to use paragraphs taken from these documents to guide the development of this HOWTO. This way we are using the original source of information to build our explanation. Those of you interested in going deeper in the study of this architecture are encourage to read directly the documents published by IETF.
 
Note: paragraphs taken for other author's documents will be presented in cursive font.
 
Up to now we have a vague idea. We want to convert our domain in a differentiated service enabled domain; for doing this we need to mark packets entering our domain and based on these marks, we are going to guarantee some kind of forwarding service for each group of packets. Let us now polish this idea using as sources the documents from IETF. Let us start with RFC 2474 that define the DS field.
 

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