INTERNET-DRAFT John Kaippallimalil
Intended Status: Informational Huawei
Expires: October 23, 2013 April 21, 2013
Mapping PMIP Quality of Service in WiFi Network
draft-kaippallimalil-netext-pmip-qos-wifi-02
Abstract
This document proposes a model for configuring and mapping PMIP QoS
parameters of a mobile network session to the corresponding
connection at a WiFi Access Point. In congested network conditions,
it is useful for an MN's flows to be policed and shaped at the WLC
and WiFi AP to match bandwidth constraints or service priority of
the user's subscription. Applying similar QoS management at the WiFi
AP and WLC allows optimal use of network resources. Currently, the
WiFi AP does not have information on the MNs subscribed bandwidth, or
relative priority of its flows or services for per user QoS handling
at the WiFi AP. This document provides a model for mapping PMIP QoS
to corresponding 802.11e QoS parameters.
Status of this Memo
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Copyright and License Notice
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Copyright (c) 2013 IETF Trust and the persons identified as the
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . . 4
1.2. Definitions . . . . . . . . . . . . . . . . . . . . . . . . 4
1.3. Abbreviations . . . . . . . . . . . . . . . . . . . . . . . 4
2. QoS Mechanisms . . . . . . . . . . . . . . . . . . . . . . . . 4
2.1. QoS in Mobile Networks . . . . . . . . . . . . . . . . . . 4
2.2. QoS in WiFi Networks . . . . . . . . . . . . . . . . . . . 5
3. Connection Model . . . . . . . . . . . . . . . . . . . . . . . 5
4. Policy Provisioning Architecture . . . . . . . . . . . . . . . 7
5. QoS Configuration and Mapping . . . . . . . . . . . . . . . . . 8
5.1. PMIP - 802.11e QoS Configuration . . . . . . . . . . . . . 8
5.2. Mapping Recommendations and Default Values . . . . . . . . 9
6. Next Steps . . . . . . . . . . . . . . . . . . . . . . . . . . 10
7. Security Considerations . . . . . . . . . . . . . . . . . . . . 11
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 11
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 11
9.1. Normative References . . . . . . . . . . . . . . . . . . . 11
9.2. Informative References . . . . . . . . . . . . . . . . . . 11
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 12
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1. Introduction
This document describes a means for the QoS profile of a PMIP session
to be applied to QoS on the 802.11 connection segment of the MN
(Mobile Node). A mobile network may dynamically provision QoS for its
users attached via a WiFi access and PMIP backhaul. [PMIP-QoS]
defines a mechanism by which QoS policy parameters in the mobile
network are delivered from the LMA to the the WLC (MAG) using PMIP
QoS extensions. [PMIP-QoS] further describes how the DSCP value for
the PMIP session is mapped to corresponding 802.1p value that may be
used by IP backhaul network or WiFi APs to prioritize IP flows of a
host (MN).
While [PMIP-QoS] defines how mobile network QoS can be applied to
PMIP flows, the WiFi AP has to reflexively map QoS for IP flows.
Based on the observed DSCP values in downstream packets of an IP
flow, the WiFi AP provides the same level of QoS in the upstream
direction. In addition, the WiFi AP may use the downstream DSCP
values to determine the scheduling priority in the 802.11 network.
Based on [PMIP-QoS], the WLC (MAG) can use DSCP priority as well as
other parameters of the MN such as subscribed bandwidth and service
priority to police IP flows of an MN. The WiFi AP on the other hand
relies on DSCP priority for scheduling and policing IP flows of an MN
since it does not have per subscriber policy information of an MN. In
congested network conditions, it is not possible for the WiFi AP to
differentiate between MNs that have premium subscriptions. In
addition, it is possible that upstream flows from the WiFi AP are
throttled by the WLC to match the bandwidth constraints or service
priority. This can result in sub-optimal use of network resources. In
order for the WiFi AP to differentiate on per flow and per user
basis, it needs information on the MNs subscribed bandwidth and other
policy information.
This proposal aims to provide the WiFi AP with per MN QoS profile to
allow more effective overall use of network resources - both WiFi
radio and IP backhaul. The QoS parameters needed are available to the
WLC during MN authorization and establishment of the PMIP session
with QoS extensions. Since an MN may establish tunneled IP flows,
direct IP connections or offloaded connections, the relationship of
PMIP QoS to 802.11e QoS is explained. It is possible that an MN (with
a single 802.11 interface) has more than one PMIP session. The QoS
policy for the MN may be applied by the AP to schedule and control
WiFi radio network resources and upstream user flows in the IP
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, a consistent mapping
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of QoS parameters and values between 3GPP and 802.11e is needed.
Recommendations to map 3GPP QCI to DSCP for mobility sessions are
available in [PMIP-QoS]. This document adds the configuration of QoS
per PMIP mobility session to a WiFi radio access.
The rest of the document is organized as follows. Chapter 2 outlines
the QoS mechanisms in 3GPP mobile networks and 802.11 networks.
Chapter 3 provides an overview of the architecture in which QoS is
provisioned on the WiFi AP. Chapters 4 and 5 describe the connection
model in the access network and the QoS mapping itself.
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
MBR Maximum Bit Rate
MN Mobile Node
PDN-GW Packet Data Network Gateway
QCI QoS Class Indicator
QoS Quality of Service
Tspec Traffic Conditioning Spec
WLC Wireless Controller
2. QoS Mechanisms
2.1. QoS in Mobile Networks
3GPP has standardized QoS for EPC (Enhanced Packet Core) from Release
8 [TS 23.107]. 3GPP QoS policy configuration defines access agnostic
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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 MN (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].
An MN 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 WiFi 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
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. Connection Model
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MNs that attach to a mobile network via a WiF AP and WLC are
provisioned with IP addresses corresponding to each PMIP session.
Each of the IP sessions at MN has QoS policies associated to it. This
section outlines the connection model in detail and QoS mapping on
the WiFi AP.
WiFi AP WLC(MAG)
+----------+ +-------------+
|+--------+| | +---------+ |
+---+ || PEP || | + PEP + |
|MN | |+--------+| | +---------+ |
| 1 ===========================[conn-1]=========<X>=======[PMIP-1]
+---+ | | | |
+---+ | | | |
|MN +--------------------------[conn2a]---------<X>=======[PMIP-2]
| 2 +--------------------------[conn2b]---------<X> |
+---+ +----------+ +------|------+
|
V
[offload path]
Figure 1: MN Connection model
An MN may establish a session to the mobile network or may have a
session that is offloaded to the internet from the WLC.
Figure 2 shows MN1 and MN2 attached to the WLC via a WiFi AP. An MN
may have a tunneled connection to the mobile network (MN1, conn-1,
PMIP-1), (MN2, conn2a, PMIP-2) and an IP connection that is offloaded
at the WLC (MN2, conn2b, offload). The specification for IP
tunnel/connection between MN and WLC are out of the scope of this
document.
For an MN - WLC connection segment with IP address configured via
PMIP (e.g. MN2 conn2a), the corresponding PMIP QoS would be
applicable to MN flows with this IP address.
For connection segment that is offloaded at WLC, the IP address is
configured by the WLC. As in the case of PMIP connections, QoS is
provisioned for MN flows with this IP address
In both cases - PMIP session related connection segment, or offload
connection segment - the WiFi AP gets QoS traffic filters and
configuration from the WLC. The QoS profile would be identified by
the IP address for the PMIP / offload session.
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4. Policy Provisioning Architecture
This section describes the architecture in which the PMIP QoS
configuration of MN sessions is applied to the corresponding traffic
flows in the WiFi Access Point. Following MN attach to the WiFi
network and authentication with the mobile network, the WLC gets QoS
parameters and other policy for the authorized MN. When the PMIP
connection is created, the PDN-GW returns QoS policy using [PMIP-QoS]
extensions.
In [PMIP-QoS], the Access Point (AP) is not directly provisioned with
QoS for an MN connection. As a result, the AP is only able to
prioritize flows based on observed downlink DSCP values.
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,
and of the overall access network. This solution provides a
description to provision the AP with QoS policy associated to an MN.
The paragraphs that follow outline the overall architecture and
subsequent chapters provide details on QoS parameters provisioned in
the AP.
+-----+
| AAA |
+--+--+
|
|Auth
|
WiFi AP WLC(MAG)|
+----------+ +------|------+
|+--------+| QoS | +----v----+ | PMIP-QoS +------+
||QoS-Ctrl<------------+QoS-Ctrl <------------+PDN-GW+
|+---+----+| Policy | +----+----+ | +--+---+
| | | | | | |
801.11 |+---v----+| _____ | +----V----+ | ________ |
[MN]--------+ PEP +--/ IP )---+ PEP +----/ IP ) |
|+--------+| Network | +---------+ | | Network|-+
+----------+ ( / +-------------+ ( /
----- .------.
Figure 2: Architecture for provisioning QoS Policy on WiFi AP
Figure 1 provides an overview of the architecture in which QoS for an
MN is provisioned on the AP. MN QoS policy from initial session
authorization and PMIP connection establishment is provisioned in the
WLC QoS-Ctrl (logical function). QoS-Ctrl in WLC installs QoS to the
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WLC PEP as described in [PMIP-QoS].
The WLC translates 3GPP QoS policy to equivalent parameters for IP
flows and applies them for scheduling and policing.
In this solution, the WLC sends policy information for an MNs PMIP
sessions to the WiFi AP. The protocols used to exchange QoS
parameters between the WLC and AP are not discussed in this document.
The AP can use the received QoS policy configuration and applies them
to upstream and downstream forwarding of data packets in the WiFi
radio network. The AP can also apply these QoS policies for upstream
user IP flows to the WLC.
An MN may have more than one PMIP session at any given time. Each of
these PMIP sessions can have different policy parameters. The WLC
provides the WiFi AP with a policy corresponding to each of these
PMIP sessions. Since each PMIP session configures an IP address for
the MN, the policy can be sent per IP address of MN that corresponds
to the PMIP session. This model is described further in the following
chapter.
If the MN connection at WLC is offloaded to the internet, there is no
PMIP session setup to the mobile network. In this case, the WLC
should use the subscriber policy obtained during authorization. The
WiFi AP is provisioned as for other sessions. The WLC provides the
WiFi AP with QoS parameters for the MN IP address used for the
offload connection.
5. QoS Configuration and Mapping
5.1. PMIP - 802.11e QoS Configuration
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:
- Hardware (MAC) address of host for which PMIP session is
established.
- IP prefix or address of PMIP mobility session.
- IP port address (used for NATed connections).
- DSCP. Diffserv PHB value of PMIP QoS for the mobility session.
- QCI. The WLC provides 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
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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 MN flows. The
WiFi 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 IP
backhaul to the WLC. For contention free scheduling, 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 drop 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.
5.2. 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.
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 1: QoS Mapping between QCI, WMM, 802.11e AC
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6. Next Steps
This document has described a basic model for mapping PMIP QoS
parameters to 802.11e parameters. However, there are a few questions
that need to be explored further.
The protocol between WLC and AP is not discussed in this document.
There needs to be work to determine the protocol specification if it
is desired that WLC and AP should interwork for QoS capability.
Another aspect is this draft does not describe multiple PDN
connections per MN in much detail. This is work in progress in 3GPP
and the results should be compatible with the model in this draft.
RTC Web impact to 3GPP networks is currently being studied. There are
several technical options being considered by 3GPP at this time. If
the chosen solution requires more than one type of DSCP/QoS to be
configured per PMIP session/IP connection segment - for example if
audio and video flows use the same IP session - then this capability
is required for WLC - AP configuration also.
Finally, the QoS values listed in the table in chapter 5 needs to be
aligned with [PMIP-QoS] and GSMA.
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7. 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.
8. IANA Considerations
No IANA assignment of parameters are required in this document.
9. References
9.1. 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.
9.2. 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.
[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
E-Mail: john.kaippallimalil@huawei.com
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