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Mapping Differentiated Service Classes to User Priorities

Mapping Differentiated Service Classes to User Priorities. Authors:. Date: 2008-10-10. 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 802.11 UP code points. Background.

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Mapping Differentiated Service Classes to User Priorities

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  1. Mapping Differentiated Service Classes to User Priorities Authors: Date: 2008-10-10 Osama Aboul-Magd, Nortel Networks

  2. 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 802.11 UP code points Osama Aboul-Magd, Nortel Networks

  3. Background • The current revision of the IEEE 802.11u draft (D4.0) provides two methods for mapping IP DSCP to IEEE 802.11 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 • 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 • 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 Up to four AF classes Incoming packets Osama Aboul-Magd, Nortel Networks

  6. IEEE 802.11 UP • IEEE 802.11 UP are based on those defined in IEEE 802.1D. • Each priority has a designated traffic type (informative) Lowest Highest Osama Aboul-Magd, Nortel Networks

  7. 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 802.11 UP that provides similar behavior. • Mapping by range may result in inconsistent behavior between IP and IEEE 802.11. • 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 Recommended DSCP Mapping • Recommend using RFC4594 Application Class Definitions and Mappings • (Summarized Above) • Arrows Show Possible Alignment Of 802.11u Application Classes To RFC4594 Application Classes • Additional Concerns with Current 802.11u 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. 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 802.11u draft • Yes: No: Don’t care: • Do you support updating the table T-2 in Annex T to align it with RFC 4594 applications • Yes: No: Don’t care: Osama Aboul-Magd, Nortel Networks

  10. 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

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