Internet DRAFT - draft-jobert-iccrg-ip-aware-ap
draft-jobert-iccrg-ip-aware-ap
Internet Draft S. Jobert
Intended status: Informational I. Hamchaoui
Expires: January 2014 W. Diego
Orange
July 11, 2013
Packet-oriented QoS management model for a wireless Access Point
draft-jobert-iccrg-ip-aware-ap-00.txt
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
This document may contain material from IETF Documents or IETF
Contributions published or made publicly available before November
10, 2008. The person(s) controlling the copyright in some of this
material may not have granted the IETF Trust the right to allow
modifications of such material outside the IETF Standards Process.
Without obtaining an adequate license from the person(s) controlling
the copyright in such materials, this document may not be modified
outside the IETF Standards Process, and derivative works of it may
not be created outside the IETF Standards Process, except to format
it for publication as an RFC or to translate it into languages other
than English.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet-
Drafts.
Internet-Drafts are draft documents valid for a maximum of six
months and may be updated, replaced, or obsoleted by other documents
at any time. It is inappropriate to use Internet-Drafts as
reference material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html
This Internet-Draft will expire on January 11, 2014.
Jobert Expires January 11, 2014 [Page 1]
Internet-Draft Packet-oriented QoS management model July 2013
for a wireless Access Point
Copyright Notice
Copyright (c) 2013 IETF Trust and the persons identified as the
document authors. All rights reserved.
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 to this document.
Abstract
This document introduces a packet-oriented QoS management model
applicable to a wireless Access Point, referred to as "IP aware
Access Point". This model may be used in addition, or as a
substitute to the connection-oriented traditional QoS model defined
for cellular mobile networks, based on the notion of bearer.
Table of Contents
1. Introduction ................................................. 2
2. Conventions used in this documen ............................. 4
3. Concepts and architecture .................................... 4
4. IP aware wireless Access Point behavior ...................... 6
5. Extension to upstream traffic ................................ 7
6. Examples of possible models .................................. 8
6.1. Model for intra-bearer arrangement ...................... 8
6.2. Models for inter-bearer arrangement ..................... 9
7. Security Considerations ...................................... 9
8. IANA Considerations .......................................... 9
9. References ................................................... 9
9.1. Normative References .................................... 9
9.2. Informative References ................................. 10
10. Acknowledgments ............................................ 10
1. Introduction
The management of QoS in cellular mobile networks remains
connection-oriented in many cases: when QoS differentiation is
targeted, the general solution proposed by most existing cellular
mobile standards consists in establishing several tunnels (e.g.
bearers), one per class of service, between the mobile terminal
(e.g. UE) and the wireless Access Point (e.g. NodeB, eNB).
Jobert Expires January 11, 2014 [Page 2]
Internet-Draft Packet-oriented QoS management model July 2013
for a wireless Access Point
The packets are then positioned into the various tunnels, depending
on various criteria, for instance on the required QoS of the
corresponding application. Adapted QoS treatments are then applied
on the overall tunnels, according to the characteristics of the
established bearers, but not at the packet level. In other words:
even if an IP packet is marked (e.g. using DSCP marking) as being of
high priority, this information inside the packet is not taken into
account to schedule the packet over the radio interface, only the
bearer that the packet belongs to matters.
These tunnels are moreover in general extended up to an aggregation
point in the network (e.g. GGSN, PDN-GW). Packet-oriented QoS
management may however be applied over the fixed portion of the
network, although tunnels are present.
This connection-oriented model was inherited from TDM-based
transport, and it was well adapted to early mobile data services
deployments when the amount of data exchanged was low. It now raises
important questions considering the high volumes and variability of
mobile data traffic to be handled by most of mobile network
operators generated by smartphones applications.
In addition, managing the QoS of mobile networks using a connection-
oriented model has clearly some drawbacks, such as: problems of
scalability of the architecture due to the number of tunnels to be
maintained simultaneously, additional signaling traffic required to
establish or modify the parameters of the tunnels, time to establish
or modify a tunnel, etc.
In this draft, we introduce the concepts of a packet-oriented QoS
management model applicable to a wireless Access Point, referred to
as "IP aware Access Point", which can be considered as an
alternative approach to the existing connection-oriented model. Note
however that both models could be simultaneously deployed: a
connection-oriented model could be used for managed ISP services
when signaling traffic is exchanged prior to starting the service (a
typical example might be managed VoLTE), while a packet-oriented
model could be suitable to differentiate among the other services
(e.g. Internet services), thanks to proper DSCP marking/remarking
(according to the QoS policy enforced in the ISP-operated DiffServ
domain).
It is expected that this model be applicable to both licensed and
unlicensed wireless networks (such as Wi-Fi).
Jobert Expires January 11, 2014 [Page 3]
Internet-Draft Packet-oriented QoS management model July 2013
for a wireless Access Point
2. Conventions used in this document
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].
In this document, these words will appear with that interpretation
only when in ALL CAPS. Lower case uses of these words are not to be
interpreted as carrying RFC-2119 significance.
AP: Access Point
CQI: Channel Quality Indicator
DSCP: Differentiated Services Code Point
eNB: evolved NodeB
GGSN: Gateway GPRS Support Node
Mifi: Mobile Wi-Fi
NB: NodeB
PDN-GW: Packet Data Network Gateway
PF: Proportional Fair
RB: Resource Block
TTI: Transmission Time Interval
UE: User Equipment
VoLTE: Voice over LTE
3. Concepts and architecture
Introducing a packet-oriented model in mobile networks is expected
to simplify QoS management by leveraging the experience and current
practice in fixed IP networks and permitting consistent operations
over all network segments. Indeed, it simply reuses proven (and
standard) mechanisms of fixed IP networks. It also solves most of
the drawbacks of the connection-oriented approach. Finally, it
Jobert Expires January 11, 2014 [Page 4]
Internet-Draft Packet-oriented QoS management model July 2013
for a wireless Access Point
allows for global seamless offers over various wireline and wireless
accesses.
The proposed packet-oriented QoS management model consists in the
following main principles (the description below applies mainly to
the downstream direction, i.e. from the wireless AP to the terminal,
but can be extended to the upstream direction, i.e. from the
terminal to the wireless AP):
o There is no need for establishing several tunnels to allow
differentiated QoS treatments; multiple classes of service are
defined for this purpose independently of the tunnels, allowing
differentiated QoS treatments inside the same tunnel, which may
be maintained for mobility purposes if needed.
o The packets SHOULD be marked or re-marked properly at the ingress
of the DiffServ domain corresponding to the mobile network,
according to the applicable criteria (which may depend on the
type of service, agreement between parties, etc.). The DSCP field
in the header of the IP packets MUST be used for this purpose.
This marking SHOULD be maintained transparently up to the IP
aware Access Point. Depending on the applicable scenario, the
DSCP marking function MAY be located in any upstream point from
the IP aware access point, including the traffic source.
o The IP aware wireless Access Point MUST classify the packets
based on the marking indicated in each packet and differentiated
treatments are applied on a packet-per-packet basis. The packets
with the highest priority SHOULD for instance be positioned in a
high priority queue, which is served first when radio resources
are allocated to the terminal.
Figure 1 below illustrates the proposed packet-oriented QoS
management model, with an example where 3 classes have been
configured in the IP aware Access Point (e.g. one for traffic
requiring low delay/jitter, one for traffic requiring low packet
loss, and one for Best Effort traffic). Note that the IP layer at
the IP aware Access Point MAY NOT implement a full IP layer (e.g.
only the DSCP marking in the IP header MUST be analyzed to classify
the packets into the relevant queues, but the forwarding of the
packets MAY be based on traditional relaying functions between the
tunnel on fixed network and the radio layers).
Jobert Expires January 11, 2014 [Page 5]
Internet-Draft Packet-oriented QoS management model July 2013
for a wireless Access Point
+-----------------------------------------------------------------+
| ++ | #: Voice packet |
| .----++ | +------------+ *: Video packet |
| | .-. | Radio | +------+ | @: Email packet +-----+ |
| | |#| |Scheduling| |#### | | #|Voice| |
| | '-' | | | | +------+ | '-----' |
| | .-. |==========| | Queue1 | # |
| | |*| | +------+ | | +------+ |==================== +-----+ |
| | '-' | |##*@ | | | |***** | |@ # * @ # * @ * # * *|Video| |
| | .-. | +------+ | | +------+ |==================== @ '-----' |
| | |@| |==========| | Queue2 | Fixed network |
| | '-' | | | v +------+ | (backbone/backhaul) @ +-----+ |
| '-----' | | |@@@ | | @|Email| |
| Mobile | | +------+ | '-----' |
| Terminal V | Queue3 | |
| +------------+ |
| +-------+ IP Aware Wireless AP +-------+ |
| | App |---------------------------------------------| App | |
| |-------| |-------| |
| |TCP/UDP|---------------------------------------------|TCP/UDP| |
| |-------| +-------+ +-------+ DSCP |-------| |
| | IP |----------| IP |------| IP |--Marking--| IP | |
| |-------| |-------| |-------| |-------| |
| | L2 |----------| L2 |------| L2 |-----------| L2 | |
| |-------| |-------| |-------| |-------| |
| | L1 |----------| L1 |------| L1 |-----------| L1 | |
| +-------+ +-------+ +-------+ +-------+ |
| '---------v-----------' '------------------v------------------' |
| Radio segment Wireline segment |
+-----------------------------------------------------------------+
Figure 1 - Packet-oriented QoS management model in mobile networks
4. IP aware wireless Access Point behavior
The IP aware Access Point MUST take into account the DSCP/ToS field
of each packet prior to the transmission over the radio segment. For
this purpose, an IP multiplexing stage (i.e. an IP queuing system)
is added before the radio scheduler. This two-level scheduling
process can be implemented through various algorithms. In some
cases, it is relevant to consider a model which associates one set
of IP queues to each terminal (see for instance the model in section
6.1).
Jobert Expires January 11, 2014 [Page 6]
Internet-Draft Packet-oriented QoS management model July 2013
for a wireless Access Point
In this draft, we distinguish two main types of behavior for the IP
aware Access Point:
o Intra-bearer arrangements: the allocation of radio resources is
independent of the traffic mix waiting for transmission; in this
case, radio resources allocated to a given user are determined by
a basic radio scheduler which generally takes into account the
radio conditions (e.g. algorithm based on Proportional Fairness).
The addition of an IP priority queuing system per user before the
radio scheduler (without influencing it) allows prioritizing the
sensitive flows of a given user against his own other flows when
populating the radio frame.
o Inter-bearer arrangements: the allocation of the radio resources
depends on the traffic mix waiting for transmission; in this
case, the radio resources allocated to one UE not only depend on
the radio conditions of the UE, but also on the traffic mix
offered to the IP queuing system. This traffic mix is defined
through the DSCP of its constitutive packets. Several approaches
are possible (e.g. weighting the allocation according to the
prioritized traffic volume / priority queue backlog, ensuring a
maximum latency for certain classes, etc.)
The first case (intra-bearer arrangement) is expected to be useful
for multi-tasking users (e.g. user running several applications
simultaneously, for instance in case of tethering terminals or
acting as Mifi access point). This model is further detailed in
section 6.1 of this document.
The second case (inter-bearer arrangement) targets real time
applications with stringent QoS constraints. This model is further
detailed in section 6.2 of this document.
5. Extension to upstream traffic
A future version of this draft will provide some details on the
usage of the mechanism for upstream traffic.
Note that some solutions, such as the model described in section 6.1
of this document, are already applicable to upstream traffic without
changes in the mobile terminal.
Jobert Expires January 11, 2014 [Page 7]
Internet-Draft Packet-oriented QoS management model July 2013
for a wireless Access Point
6. Examples of possible models
The following sections provide examples of applicable models for
intra-bearer and inter-bearer arrangements. It should be noted that
these models are considered as examples only (mainly as references
for simulation activity), and that actual implementations may differ
from them.
6.1. Model for intra-bearer arrangement
In this section, we describe the intra-bearer arrangement model. The
aim of this model is to prioritize the sensitive flows of one UE
against its own other flows without modifying the radio resources
allocated to this UE. As a consequence, the good properties of the
scheduling algorithm are preserved (e.g. trade-off between UE
fairness and cell throughput), thus preserving the cell throughput
capacity.
As mentioned before, the "IP aware Access Point" MUST take into
account the DSCP/ToS field, therefore an IP layer MUST be added on
the eNB side, which is not the current practice in most existing
cellular networks. In the present model, it is assumed that the
marking procedure is performed upstream from the eNB.
On the "IP aware Access Point" side, a two-level scheduler is
implemented when considering an intra-bearer arrangement:
The first level consists in an IP priority queuing system composed of
"n" finite queues per UE (DiffServ model - one queue per level of
QoS). These queues are operated according to a non-preemptive service
policy. This means that if one or more high priority packets arrive
when a packet of lower priority is served, the high priority packets
will be served only after the current service of a low priority
packet is complete. For the sake of simplicity, we propose the use of
a strict priority policy between queues, but other policies are also
possible, such as weighted fair queuing/weighted round robin. The
service rate of this IP queuing system is constant during each TTI
(Transmission Time Interval). It is calculated for each UE at each
TTI by the second level described hereafter.
The second level is a radio scheduler which shares the available
radio resources (e.g. RB - Resources Block in LTE) between the UEs.
Jobert Expires January 11, 2014 [Page 8]
Internet-Draft Packet-oriented QoS management model July 2013
for a wireless Access Point
Different scheduling algorithms are possible for the allocation of
radio resources depending on the optimization criteria (delay,
throughput, etc., or trade-off between some of these criteria). On
the present model, Proportional Fair (PF) scheduler, without any
modification, is suggested because it offers a good trade-off between
cell throughput and fairness between UEs, and because it is the basis
of many scheduler implementations in base stations. PF assigns the
available radio resources to UEs every TTI (Transmission Time
Interval), regardless of the first level queuing process described
above. The PF scheduler algorithm takes into account the radio
conditions (e.g. CQI - Channel Quality Indicator in LTE) provided by
each UE.
6.2. Models for inter-bearer arrangement
A future version of this draft will provide some details on the
applicable models for inter-bearer arrangements.
7. Security Considerations
<Add any security considerations>
8. IANA Considerations
<Add any IANA considerations>
9. References
9.1. Normative References
[1] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[2] Crocker, D. and Overell, P.(Editors), "Augmented BNF for
Syntax Specifications: ABNF", RFC 2234, Internet Mail
Consortium and Demon Internet Ltd., November 1997.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
Jobert Expires January 11, 2014 [Page 9]
Internet-Draft Packet-oriented QoS management model July 2013
for a wireless Access Point
[RFC2234] Crocker, D. and Overell, P.(Editors), "Augmented BNF for
Syntax Specifications: ABNF", RFC 2234, Internet Mail
Consortium and Demon Internet Ltd., November 1997.
9.2. Informative References
[3] Faber, T., Touch, J. and W. Yue, "The TIME-WAIT state in TCP
and Its Effect on Busy Servers", Proc. Infocom 1999 pp. 1573-
1583.
[4] Hamchaoui, I., Jobert, S., Boufelja, S., "IP aware radio
scheduling - Introducing IP QoS management in LTE networks",
IEEE ICC'13, June 2013
10. Acknowledgments
This document was prepared using 2-Word-v2.0.template.dot.
Jobert Expires January 11, 2014 [Page 10]
Internet-Draft Packet-oriented QoS management model July 2013
for a wireless Access Point
Authors' Addresses
Sébastien Jobert
Orange
2 avenue Pierre Marzin
22300 LANNION, FRANCE
Email: sebastien.jobert@orange.com
Isabelle Hamchaoui
Orange
2 avenue Pierre Marzin
22300 LANNION, FRANCE
Email: isabelle.hamchaoui@orange.com
William Diego
Orange
2 avenue Pierre Marzin
22300 LANNION, FRANCE
Email: william.diego@orange.com
Jobert Expires January 11, 2014 [Page 11]
