Mapping PMIP Quality of Service in WiFi Network
draft-kaippallimalil-netext-pmip-qos-wifi-00
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| Last updated | 2012-07-07 | ||
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draft-kaippallimalil-netext-pmip-qos-wifi-00
INTERNET-DRAFT John Kaippallimalil
Intended Status: Informational Huawei
Expires: January 7, 2013 July 6, 2012
Mapping PMIP Quality of Service in WiFi Network
draft-kaippallimalil-netext-pmip-qos-wifi-00
Abstract
This document proposes a mapping for PMIP QoS parameters of each
mobility session that a WLC configures on a WiFi Access Point. In
particular there is a recommendation for consistent mapping between
DSCP and QCI to 802.11e parameters. The document also discusses that
these QoS parameters can be used by the WiFi Access Point to provide
priority based services based on contention in WiFi radio network or
reservation based services in contention free cycles in the WiFi
radio network.
Status of this Memo
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Copyright and License Notice
Copyright (c) 2012 IETF Trust and the persons identified as the
document authors. All rights reserved.
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This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
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described in the Simplified BSD License.
Table of Contents
1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1 Terminology . . . . . . . . . . . . . . . . . . . . . . . . 3
1.2 Definitions . . . . . . . . . . . . . . . . . . . . . . . . 3
1.3 Abbreviations . . . . . . . . . . . . . . . . . . . . . . . 3
2. QoS Mechanisms . . . . . . . . . . . . . . . . . . . . . . . . 4
2.1 QoS in 3GPP Networks . . . . . . . . . . . . . . . . . . . . 4
2.2 QoS in 802.11 Networks . . . . . . . . . . . . . . . . . . . 4
3. QoS Configuration . . . . . . . . . . . . . . . . . . . . . . . 5
3.1 Architecture Context . . . . . . . . . . . . . . . . . . . . 5
3.2 QoS Configuration on WiFi AP . . . . . . . . . . . . . . . . 6
4. Mapping Recommendations and Default Values . . . . . . . . . . 7
5. Security Considerations . . . . . . . . . . . . . . . . . . . . 9
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 9
7 References . . . . . . . . . . . . . . . . . . . . . . . . . . 9
7.1 Normative References . . . . . . . . . . . . . . . . . . . 9
7.2 Informative References . . . . . . . . . . . . . . . . . . 9
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 10
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1 Introduction
This document provides information on how to map 3GPP QoS profile to
802.11e. When a user with subscription in the 3GPP network attaches
to a 3GPP EPC via a WiFi access, the 3GPP network can provides a QoS
profile for each mobility session over PMIP (S2a interface) and
during authorization over Diameter (STa interface). [PMIP-QoS]
proposes a mechanism by which QoS policy parameters in the 3GPP EPC
(Enhanced Packet Core) are obtained by the WLC (MAG). [PMIP-QoS]
further describes how DSCP obtained via PMIP is mapped to 802.1p and
used by WiFi APs to prioritize IP flows to/from a host (UE).
The QoS policy for the user should be applied in the WiFi radio
network and to upstream user flows in the IP backhaul network. DSCP
or 802.1D mapping can be used in the backhaul network. If per session
QoS policy is not available, the AP may be provisioned to apply QoS
based on the subscribed QoS values obtained during 3GPP user
authorization.
In order to provision QoS in the WiFi network, it is useful to have a
consistent mapping of QoS parameters and values between 3GPP and
802.11e. Recommendations to map a 3GPP QCI to DSCP for mobility
sessions are available in [PMIP-QoS]. This document adds the explicit
configuration of QoS per PMIP mobility session to a WiFi access
(radio access).
1.1 Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].
1.2 Definitions
1.3 Abbreviations
3GPP Third Generation Partnership Project
AAA Authentication Authorization Accounting
ARP Allocation and Retention Priority
AP Access Point
DSCP Differentiated Services Code Point
EPC Enhanced Packet Core
GBR Guaranteed Bit Rate
MAG Mobility Access Gateway
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MBR Maximum Bit Rate
PDN-GW Packet Data Network Gateway
QCI QoS Class Indicator
QoS Quality of Service
Tspec Traffic Conditioning Spec
UE 3GPP User Equipment
WLC Wireless Controller
2. QoS Mechanisms
2.1 QoS in 3GPP Networks
3GPP has standardized QoS for EPC (Enhanced Packet Core) from Release
8 [TS 23.107]. 3GPP QoS policy configuration defines access agnostic
QoS parameters that can be used to provide service differentiation in
multi vendor and operator deployments. The concept of a bearer is
used as the basic construct for which the same QoS treatment is
applied for uplink and downlink packet flows between the UE (host)
and gateway [TS23.401]. A bearer may have more than one packet filter
associated and this is called a Traffic Flow Template (TFT). The IP
five tuple (IP source address, port, IP destination, port, protocol)
identifies a flow.
The access agnostic QoS parameters associated with each bearer are
QCI (QoS Class Identifier), ARP (Allocation and Retention Priority),
MBR (Maximum Bit Rate) and optionally GBR (Guaranteed Bit Rate). QCI
is a scalar that defines packet forwarding criteria in the network.
Mapping of QCI values to DSCP is well understood and GSMA has defined
standard means of mapping between these scalars [GSMA-IR34].
A 3GPP UE may have more than one IP addresses associated with the
same hardware (MAC) address corresponding to each of the networks
than it is attached to. This corresponds to more than one PMIP
mobility session for which QoS is provisioned in the WLC.
2.2 QoS in 802.11 Networks
802.11e [802.11e] defined by IEEE provides an enhancement of the MAC
layer in WiFi networks to support QoS. Basic 802.11 WiFi uses CSMA
and collision avoidance to provide best effort access to the medium.
802.11e defines a Hybrid Coordination Function (HCF) that provides a
priority based access and also admission control based access.
HCF contention based channel access provides prioritized access to
the 802.11 medium. Four access categories (AC) are defined based on
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traffic type. Each arriving frame is mapped into one of four FIFO
queues corresponding to different user priority (UP) values. The
highest priority frame is transmitted when access is obtained in a
contention window. Access categories and their mapping to 802.1D user
priorities is provided [802.11e].
HCF controlled channel access uses a central coordinator to provide
contention free access to the medium based on admission control. The
HCCA (HCF Controlled Channel Access) based scheduling can use
configured policies to grant exclusive access to a QSTA (user) for
limited contention free slots.
3. QoS Configuration
3.1 Architecture Context
This section describes the context in which the 3GPP QoS
configuration is applied to traffic flows handled by a WiFi Access
Point. In this case, a 3GPP user attaches to the WiFi network and
accesses services in the 3GPP EPC. The 3GPP EPC provides QoS
parameters when the user is authorized (subscribed QoS) and for each
connection to EPC as described in [PMIP-QoS]. At this point, the WLC
has 3GPP QoS parameters for each user attached to the EPC. Access
Points can use DSCP values in downlink IP flows associated with a
user to provision 802.11e priority in WiFi network.
In [PMIP-QoS], the Access Point (AP) is not directly provisioned with
QoS for a user connection. As a result, the AP is only able to
prioritize flows based on observed DSCP values on downlink flows.
Additionally, the AP does not know the maximum bandwidth of a
subscriber or flow to be applied on the WiFi radio network. This can
result in sub-optimal utilization of scarce WiFi network resources.
This solution recommends provisioning the AP with QoS policy
associated to a user.
The paragraphs that follow outline the overall architecture and the
next sub-chapter provides details on QoS parameters provisioned in
the AP.
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+-----+
| AAA |
+--+--+
|
| STa
|
WiFi AP WLC(MAG)|
+---------------+ +-------|-------+
| +---------+ | 802.11 | +----v----+ | PMIP-QoS +--------+
| |QoS-Ctrl <-----------------+QoS-Ctrl <--------------+ PDN-GW +
| +----+----+ | QoS | +----+----+ | (S2a) +---+----+
| | | | | | |
| +----v----+ | _____ | +----V----+ | ________ |
| | PEP +-----/ IP )-----+ PEP +------/ IP ) |
| +---------+ | Network | +---------+ | | Network|--+
+---------------+ ( / +---------------+ ( /
----- --------
Figure 1: Provisioning 802.11 QoS parameters on WiFi AP
Figure 1 provides a view of the architecture in which the 3GPP QoS is
provisioned on the AP. The end user (not shown in figure) attaches to
the 3GPP EPC (Enhanced Packet Core) via the WiFi AP and WLC. The two
QoS provisioning interfaces shown in the figure are STa for
delivering subscriber policy as part of user authorization, and S2a
PMIP for each connection to the EPC. QoS-Ctrl (logical entity) in WLC
provisions QoS to the WLC PEP as described in [PMIP-QoS]. In
addition, the WLC translates the 3GPP QoS policy to equivalent
parameters for 802.11e and IP flows and sends them to the WiFi AP.
The protocols used to exchange QoS parameters between the WLC and AP
are not discussed in this document. The AP maps the received QoS
policy configuration and applies them to upstream and downstream
forwarding of data packets on the WiFi radio network. The AP also
applies these QoS policies for upstream user IP flows to the WLC.
The WLC takes subscriber policy and policy per connection to EPC
network and translates it to equivalent 802.11e and DSCP parameters.
It should be noted that 3GPP users may have more than one connection
and policy associated with each of them. The WLC should provide the
AP with a policy that applies to each user (MAC address in WiFi
network) and parameters per IP flow.
3.2 QoS Configuration on WiFi AP
The WiFi Access Point (AP) gets QoS configuration per IP session from
the WLC. The QoS information per IP session provided to the AP
includes:
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- Hardware (MAC) address of host for which PMIP session is
established.
- IP prefix or address of PMIP mobility session
- DSCP. Diffserv PHB value of PMIP QoS for the mobility session.
- QCI. The WLC may provide the 3GPP QCI value if available, for
example, from authorization profile of APN (i.e. subscribed values
per established PMIP mobility session).
- ARP (Allocation and Retention Priority). This value is obtained
from the PMIP QoS for the mobility session. It determines the
priority of a flow (1 has highest priority).
- MBR (Maximum Bit Rate) for mobility session uplink and downlink.
This should not exceed the AMBR (Aggregate MBR) of the
subscription.
- GBR (Guaranteed Bit Rate) for mobility session uplink and downlink,
if required.
The WiFi AP uses the above QoS configuration to implement
classification, admission control and forwarding of user flows. The
WiF AP maps DSCP (or QCI) to 802.11e AC (Access Categories) for each
IP session / hardware (MAC) address of the host (3GPP user). The
mapping from DSCP or QCI to 802.11e AC is shown in table in chapter 4
below.
In the WiFi radio network, the AP uses 802.11e AC values for
contention (HCF) based forwarding based on priority. The AP schedules
downstream flows in the WiFi radio network and for upstream backhaul
to the WLC. For contention free scheduling (based on HCCA), the WiFi
AP additionally uses the QoS configuration per user to admit flows
based on 802.11e ADDTS (ADD TSpec) requests from the host (3GPP
user). The WiFi AP may drops packet that fall outside the configured
MBR and GBR. In case of severe radio congestion, the WiFi AP can use
ARP in addition to DSCP drop precedence to determine the flows to be
dropped.
4. Mapping Recommendations and Default Values
The table below outlines a recommended mapping between 3GPP QCI,
and 802.11e Access Category (AC) priorities. QCI packet delay budget
and packet error loss rate may be used by the WiFi access point in
scheduling contention free access when HCCA scheduling is used.
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QCI DSCP 802.11e AC Example 3GPP service
-------------------------------------------------------------
1 EF 3 AC_VO conversational voice
2 EF 3 AC_VO conversational video
3 EF 3 AC_VO real-time gaming
4 AF41 2 AC_VI buffered streaming
5 AF31 2 AC_VI IMS signaling
6 AF31 2 AC_VI buffered streaming
7 AF21 0 AC_BE interactive gaming
8 AF11 0 AC_BE web access
9 BE 1 AC_BK e-mail
Table: QoS Mapping between QCI, WMM, 802.11e AC
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5. Security Considerations
This document describes mapping of 3GPP QoS profile and parameters to
IEEE 802.11e parameters. No security concerns are expected as a
result of using this mapping.
6. IANA Considerations
No IANA assignment of parameters are required in this document.
7 References
7.1 Normative References
[KEYWORDS] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC1776] Crocker, S., "The Address is the Message", RFC 1776, April
1 1995.
[TRUTHS] Callon, R., "The Twelve Networking Truths", RFC 1925,
April 1 1996.
7.2 Informative References
[EVILBIT] Bellovin, S., "The Security Flag in the IPv4 Header",
RFC 3514, April 1 2003.
[RFC5513] Farrel, A., "IANA Considerations for Three Letter
Acronyms", RFC 5513, April 1 2009.
[RFC5514] Vyncke, E., "IPv6 over Social Networks", RFC 5514, April 1
2009.
[PMIP-QoS] Liebsch, et al., "Quality of Service Option for Proxy
Mobile IPv6", draft-ietf-netext-pmip6-qos-00, June 2012.
[RFC 2211] Wroclawski, J., "Specification of the Controlled Load
Quality of Service", RFC 2211, September 1997.
[RFC 2212] Shenker, S., Partridge, C., and R. Guerin, "Specification
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of Guaranteed Quality of Service", RFC 2212, September
1997.
[RFC 2216] Shenker, S., and J. Wroclawski, "Network Element QoS
Control Service Specification Template", RFC 2216,
September 1997.
[RFC 3246]
[TS23.107] Quality of Service (QoS) Concept and Architecture, Release
10, 3GPP TS 23.107, V10.2.0 (2011-12).
[TS23.207] End-to-End Quality of Service (QoS) Concept and
Architecture, Release 10, 3GPP TS 23.207, V10.0.0 (2011-
03).
[TS23.401] General Packet Radio Service (GPRS) enhancements for
Evolved Universal Terrestrial Radio Access Network (E-
UTRAN) access (Release 11), 3GPP TS 23.401, V11.2.0 (2012-
06).
[TS23.203] Policy and Charging Control Architecture, Release 11, 3GPP
TS 23.203, V11.2.0 (2011-06).
[TS29.212] Policy and Charging Control over Gx/Sd Reference Point,
Release 11, 3GPP TS 29.212, V11.1.0 (2011-06).
[802.11e] IEEE, "IEEE part 11: Wireless LAN Medium Access
Control(MAC) and Physical Layer (PHY) specifications.
Amendment 8: Medium Access Control (MAC) Quality of
Service Enhancements" 802.11e-2005, 22 September 2005.
[GSMA-IR34]Inter-Service Provider Backbone Guidelines 5.0, 22
December 2010
Authors' Addresses
John Kaippallimalil
5340 Legacy Drive, Suite 175
Plano Texas 75024
EMail: john.kaippallimalil@huawei.com
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