1. Mapping Differentiated Service Classes to User Priorities
Month Year
doc.: IEEE yy/xxxxr0
November 2008
Mapping Differentiated Service Classes to User Priorities
Date:
Authors:
Osama Aboul-Magd, Nortel Networks
John Doe, Some Company

2. Month Year
doc.: IEEE yy/xxxxr0
November 2008
Abstract
This contribution considers issues related to CID 4006, LB 137. In particular it considers the mapping between the IP Diffserv code points (DSCP) and the IEEE UP code points
Osama Aboul-Magd, Nortel Networks
John Doe, Some Company

3. November 2008
Background
The current revision of the IEEE u draft (D4.0) provides two methods for mapping IP DSCP to IEEE UP.
Explicit mapping using one or more DSCP Exception field
By range
This contribution argues that the explicit mapping should be retained and the by-range mapping should be removed from the draft.
Osama Aboul-Magd, Nortel Networks

4. IP Diffserv Code Points
November 2008
000000
CS 0
001000
010000
011000
100000
101000
110000
111000
000001
CS 1
001001
010001
011001
100001
101001
110001
111001
000010
CS 2
001010
AF11
010010
AF21
011010
AF31
100010
AF41
101010
110010
111010
000011
CS 3
001011
010011
011011
100011
101011
110011
111011
000100
CS 4
001100
AF12
010100
AF22
011100
AF32
100100
AF42
101100
110100
111100
000101
CS 5
001101
010101
011101
100101
101101
110101
111101
000110
CS 6
001110
AF13
010110
AF23
011110
AF33
100110
AF43
101110 EF
110110
111110
000111
CS 7
001111
010111
011111
100111
101111
110111
111111
The IETF defines 21 different PHB with their related definitions
There is no expected behaviour based on the numerical values of the DSCP
Osama Aboul-Magd, Nortel Networks

5. IP Diffserv PHB Definitions
November 2008
IP Diffserv PHB Definitions
Class Selector (CS): introduced for backward compatibility and provides 8 levels of priority
Expedited Forwarding (EF): forwarding treatment aimed at providing services with low loss, low delay, and low delay variation. A rate R is configured for EF PHB and the delay of the EF packets is expected to be bounded.
Assured Forwarding (AF) PHB Group: defines four possible AF Classes. Each Class is assigned three discard levels for selective discard of incoming packets. Each class offers different forwarding assurances (discard precedence) to IP Packets. A configurable minimum amount of resources is needed for each AF class.
AFi2
AFi3
AFi1
Incoming
packets
Up to four
AF classes
Osama Aboul-Magd, Nortel Networks

6. November 2008
IEEE UP
IEEE UP are based on those defined in IEEE 802.1D.
Each priority has a designated traffic type (informative)
Priority UP
IEEE 802.1D AC
Designation 1 BK
AC_BK
Background 2 - BE
AC_BE
Best Effort 3 EE 4 CL
AC_VI
Video 5 VI 6 VO
AC_VO
Voice 7 NC
Lowest
Highest
Osama Aboul-Magd, Nortel Networks

7. Mapping Issues Both IP DSCP and Ethernet PCP imply certain behavior.
November 2008
Mapping Issues
Both IP DSCP and Ethernet PCP imply certain behavior.
For example IP packets marked as EF expects low delay and should be mapped to IEEE UP that provides similar behavior.
Mapping by range may result in inconsistent behavior between IP and IEEE
E.g. packets marked as EF are treated at low priority.
On the other hand explicit mapping ensures consistent treatment of packets and frames.
Osama Aboul-Magd, Nortel Networks

8. Possible Mapping based on RFC 4594
November 2008
Possible Mapping based on RFC 4594
Recommended DSCP Mapping
Recommend using RFC4594 Application Class Definitions and Mappings
(Summarized Above)
Arrows Show Possible Alignment Of u Application Classes To RFC4594 Application Classes
Additional Concerns with Current u DSCP Mapping
Bulk Data uses AF1. AF class is intended for applications with assured bandwidth allocation and it does not allow possible starvation, characteristic of “below BE” application classes (REF RFC 2597). Recommend aligning Bulk Data to RFC4594 High Throughput Data.
Controlled Load is a behavior, not an application class (RFC 2211). It can be applied to many application classes.
Signaling should use CS not AF. AF has drop precedence which is not applicable to signaling. CS also helps ensure better end-user responsiveness.
Osama Aboul-Magd, Nortel Networks

9. November 2008
Straw Poll
Do you agree that the by-range mapping may lead to inconsistent mapping between DSCP and UP
Yes: No: Don’t care:
Do you support the removal of the by-range mapping from IEEE u draft
Do you support updating the table T-2 in Annex T to align it with RFC 4594 applications
Osama Aboul-Magd, Nortel Networks

10. November 2008
References
[1] IETF RFC 2474, “Definition of the Differentiated Service field (DS filed) in the IPv4 and IPv6 Headers”, December 1999.
[2] IETF RFC 2597, “Assured Forwarding PHB Group”, June 1999.
[3] IETF RFC 3246, “An Expedited Forwarding PHB (per Hop Behavior), March 2002.
[4] IETF RFC 4594, “Configuration Guidelines for Diffserv Service Classes”, August 2006.
Osama Aboul-Magd, Nortel Networks