Internet DRAFT - draft-vonhugo-eacp-hetnet
draft-vonhugo-eacp-hetnet
Network Working Group D. von Hugo
Internet-Draft N. Bayer
Intended status: Informational C. Lange
Expires: July 24, 2015 Telekom Innovation Laboratories
January 20, 2015
Energy Aware Control Approach for QoS in heterogeneous packet
access networks
draft-vonhugo-eacp-hetnet-04
Abstract
This document describes an approach to enhance user perceived service
quality by control protocols following potential network performance
impairments in case of energy aware network operation.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Conventions and Terminology . . . . . . . . . . . . . . . . . 4
3. Energy aware network model . . . . . . . . . . . . . . . . . . 5
3.1. Network model . . . . . . . . . . . . . . . . . . . . . . . 5
3.2. Problem description . . . . . . . . . . . . . . . . . . . . 6
3.3. Solution space . . . . . . . . . . . . . . . . . . . . . . . 8
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10
5. Security Considerations . . . . . . . . . . . . . . . . . . . 11
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 12
7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 13
7.1. Normative References . . . . . . . . . . . . . . . . . . . 13
7.2. Informative References . . . . . . . . . . . . . . . . . . 13
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 15
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1. Introduction
Due to large contribution of expenses for stable provision of mainly
electrical power to overall network operational costs carrier grade
network operators try to reduce energy consumption in the access and
transport domain. A major challenge here is to grant customer
satisfaction in terms of preventing any perceivable service quality
degradation. Thus the network is required to meet the specified and
agreed performance figures demanded by various applications using
network connectivity.
Energy saving by load-adaptive provision of transmission capacity in
terms of switch-on and -off of resources (nodes, lines, node
components) or dynamic invocation of sleep modes may result in
network performance degradation due to temporary provision of only
reduced capacity and coverage. At the same time an improperly
designed procedure may introduce unduely high overhead (e.g. in
terms of signalling load) and corresponding energy consumption for
re-activation and reconfiguration of network components thus partly
counteracting the resource saving. Therefore intelligent mechanisms
for network operation control have to be applied to find optimum
decision in terms of timeliness and accuracy to perform the
reconfigurations such that the amount and quality of actually
provided capacity ensures as much as possible a successful
transmission of demanded user traffic at required quality.
Degradations in user perceived service quality depend on the service
specific requirements in terms of e.g. bandwidth, packet loss rate,
delay and delay variations which are governed both by the kind of
service (e.g. audio, video, file transfer, ...) as well as equipment
and application software specific measures to cope with network
performance variations. Thus e.g. for video streaming services such
as IPTV countermeasures to cope with variable bandwidth and delay
are implemented such as buffers to store data (see e.g [4]).
This draft reports an approach following the considerations and
requirements laid out in [2] to counteract the potential impact due
to energy aware network operation, which is represented as bandwidth
reduction, introduced stretch/delay, decreased recovery speed,
additional jitter/delay variations, and other operational aspects.
Issues of power-aware routing and traffic engineering have already
been considered in [8] and [9] in detail. Goal of this document is
to define and describe a network control functionality to monitor and
analyse the mentioned performance degradations and invoke
countermeasures to reduce service quality impact.
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2. Conventions and 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 [1].
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3. Energy aware network operation
3.1. Network model
The proposed concept for load adaptive energy aware networks follows
a model similar to [2] where the following measures are described as
primary ways to reduce energy usage
o Removing redundant links from the network topology
o Removing redundant network equipment from the network topology
o Reducing the amount of time equipment or links are operational
o Reducing the link speed or processing rate of equipment
Whereas the first two actions describe permanent changes to the
network (and would in general call for improved energy-aware
planning of network parameters during deployment) the latter two
aspects are considered as issues related to network operation
dealing with dynamical adaptation of actually provided network
capacity to the temporally variable traffic demand as addressed here.
Considerations here shall focus on networks of both types - those for
fixed services such as DSL-based (digital subscriber line) fixed
access described by BBF (BroadBand Forum) as well as those for mobile
services, i.e. a cellular access network as specified by 3GPP (3rd
Generation Partnership Project).
Technology specific approaches towards an energy aware operation are
laid out e.g. in [3] for mobile access where some cells providing
additional capacity are proposed to be switched off temporally for
reasons of power consumption optimization in case they are no longer
needed during the considered time frame. An important aspect here
is that both continuity of radio coverage and of quality of service
(QoS) remain guaranteed.
A local-autonomous solution for fixed DSL networks' energy efficiency
improvements is laid out e.g. in [10] where the data rate and the
power consumption associated with it are adapted to real traffic
demands observed on a particular access line by means of defined
bit rate and power modes.
A multi-link heterogeneous access network consisting of multiple
radio access technologies (Multi-RAT) such as different technologies
for cellular mobile and local wireless access via WLAN/WiFi is able
to provide an end user equipment (UE) with multiple
links concurrently or subsequently to enable continuous network
connectivity. Depending on current load within an area of coverage
(radio cell) part of the access nodes (i.e. radio base stations and
WiFi access points) are temporarily switched off either completely
or partially thus realizing the above mentioned measures.
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Similarly, a hybrid fixed-radio access network is conceivable where
the specifics of the per-technology power management solutions have
to be taken into account and in addition they have to be coordinated.
The simplistic network model used in [2] is shown in Figure 1.
/---R2---\ /---\
R1 R4 R5
\---R3---/ \---/
Figure 1: Simplistic model for energy aware network
Corresponding to this model here the access network part is described
with R1 as the UE connected to different access routers R2, R3 (or
AR1, AR2) which are attached to a common aggregation node R4 (AGR)
connected to the gateway serving the transition to the core network,
R5 (GW) via at least two redundant links. Without limitation of the
general applicability the described concept can also be applied to
other scenarios.
+-----+ +-----+
| AR1 | | GW |
+-----+ +-----+
/ \ / /
/ \ / /
/ \ / /
/ \ / /
+------+ +-----+ +-----+ /
| UE |______| AR2 |____| AGR |/
| | | | | |
+------+ +-----+ +-----+
Figure 2: Multi-technoloy access network
In Figure 2 the access routers AR1 and AR2 may provide connectivity
with different characteristics due to differences in fixed and/or
mobile radio technology, bandwidth, regional and temporal
availability etc.
3.2. Problem description
Task of the control plane to prevent ongoing sessions from negative
impact of network performance variations to user perceived service
quality or Quality of Experience (QoE) is to detect and counteract
those variations resulting in bandwidth reduction, and additional
delay and jitter. On the other hand a decreased recovery speed in
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case of (e.g. failure caused) loss of remaining redundant links and
nodes is more a network operational issue with impact on network
availability and reliability.
The approach described here focusses on the well known situation
that a network is dimensioned so to provide enough capacity to serve
all users and services expected in so-called busy hours when multiple
users are concurrently active resulting in overall peak demands.
During off-peak time the demanded network load is low so that part of
the network in terms of access nodes and routers can be operated in
sleep mode or switched off partially or completely.
For a cellular network we therefore may assume that a UE is
potentially being served by at least two such access nodes whereas in
a fixed network customer nodes can be switched to low power mode
reducing capacity and energy consumption both at the UE and in the
the AR (here: DSL Access Multiplexer, DSLAM). Such a behaviour is
denoted as load adaptive network reconfiguration.
The concept allowing for adaptive reconfiguration is based on
reliable measurement and/or prediction of actual user traffic demand
and subsequent decision on corresponding configuration actions.
Therefore a data base and decision engine is employed to collect and
analyse context information allowing for best decisions on changes in
network topology and configuration. An optimization is achieved when
provided capacity follows as exact as possible the traffic demand
with minimum amount of over-provisioning, i.e. offering capacity
exceeding the actual demand. Such a behaviour will grant energy
efficient operation and also account for enough margin to cope with
traffic demand uncertainties in terms of load variability to prevent
perceivable quality degradations.
Such quality impact may be introduced by network performance
degradations in terms of congestion and bandwidth reduction in case
of mismatch between capacity and demand. In addition the energy
aware network operation may introduce bandwidth reduction, stretch/
delay, additional jitter/delay variations as laid out in [2]. In a
cellular system additional delay or even loss of connectivity due to
handover of an UE between neighboring access nodes may occur when the
currently serving node is going to energy save state. A reduction of
such impact due to degradations and an operation saving energy is
also achieved thanks to improved mobility control: New proposals
for mobility management taking into account both low handover delay
and resource efficient operation are under way in WG DMM (Distributed
Mobility Management) [5].
Impact of all these parameters on different services according to
their requirements have to be considered and counteracted for
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customer satisfaction. A communication network operating in an
energy aware mode SHOULD apply additional measures to keep track of
network node and link states as well as of service related network
performance to minimize risk of degradations in service quality.
3.3. Solution space
For energy efficient network operation with minimum power consumption
at imperceptible degradation of the service quality as experienced by
the user a control plane framework with data base and decision engine
is required. Task of this framework is to monitor the network status
(or detect changes in the network status) and track the service
demand to assign the network resources (i.e. alter network topology
or configuration) in such a way that both power consumption is
reduced and user demands are satisfied (in terms of only minimal QoS
degradations which are hardly experienced by the user).
+ - - - - - - - - - - - - - - - +
| +------+ +------+ +---+---+
+- >| DB |- ->| DE |- ->| NM&SM |
+ - >| | | | | |
| +------+ +------+ +-------+
. . . .
| . . . .
. . . .
| . . . .
+-----+ . . +-----+
| | AR1 | . . | GW |
+-----+ . . +-----+
| / .\ . / /
/ . \ . / /
| / . \ . / /
/ . \ . / /
| +------+ +-----+ +-----+ /
+ - | UE |______| AR2 |____| AGR | /
| | | | | | /
+------+ +-----+ +-----+
Figure 3: Exemplary deployment of energy aware control framework in
network model of Figure 2
A simplified exemplary realisation of such a framework (i.e. data
base DB and decision engine DE) would have to cooperate with the
Network Mangement (NM) and Service Management (SM) as is specified
e.g. by 3GPP in [13] for mobile cellular networks. Such a setting
shall enable context information exchange between network elements as
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AR1, AR2, or AGR, GW (via signalling protocols towards NM, which are
shown in Figure 3 as dotted lines) as well as user equipment UE and
the DB of the framework. The abstracted context data (dashed arrows)
together with other internal data (e.g. based on policies) and
external (3rd party) information (not shown in Figure 3) are fed into
the data base. The corresponding reconfiguration decision is made in
decision entity DE considering also further data from NM and SM.
Authorised commands to change the network configuration and topology
are sent by NM to the network entities.
One approach is to apply a dedicated control protocol or enhance
existing ones like SNMP [14] and NETCONF protocol [15] when taking
into account both network status and performance. On the other hand
based on a metric to assess the service performance in relation to
current demand to efficiently assign the required network resources
considerations as laid down in [16] may apply.
Concrete measures to prevent expected performance degradations could
make use of prioritization of critical sessions and corresponding
de-priorisation of more robust ones based e.g. on QoS class
parameters as specified by DiffServ [11]. In case of switching on
new equipment to provide additional capacity the introduced delay
variation may be counteracted by providing spare capacity reserved
for those services which are highly sensitive to delay variations.
In the context of mobility handling (e.g. during handover towards
more energy efficient technology i.e. here between cellular and WiFi)
application of DiffServ QoS attributes and corresponding parameters
and mapping to technology specific figures for flows of active
sessions has been proposed in [17].
Furthermore energy related information on network devices as defined
in [12] for network management purposes SHOULD be incorporated in a
concept to control assessment of QoS requirements of different
services with respect to impact of energy aware networks.
Simulations and testbed implementations of load-adaptive measures to
increase access network energy efficiency indicate savings in the
order of 30% depending on the actual topoplogy and device
capabilities to support fast reliable on-/off-switching of nodes and
node components (see e.g. [6]).
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4. IANA Considerations
None /t.b.d.
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5. Security Considerations
Security is an important issue in access to communication networks
both in fixed-line networks and for mobile and wireless ones as
described e.g. in [5] such that any proposed protocol MUST
incorporate sufficiently strong protection mechanisms. Since the
proposed control plane framework interoperates with the network and
service management system the proper operation of which is essential
for a network operator, careful examination of security issues in
relation to corresponding interfaces and protocols is required.
Beside that to our knowledge no new security risks are introduced
with this concept.
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6. Acknowledgements
The described concepts have been developed within research projects
Com(municate) Green [6] and LOLA (Load Adaptive Local Area networks)
[7] partially funded by German federal ministry of economy and energy
(BMWi) under participation of DTAG T-Labs and other project partners.
Contributions and valuable comments by JinHyeock Choi are gratefully
acknowledged.
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7. References
7.1. Normative References
[1] Bradner, S., "Key words for use in RFCs to indicate requirement
levels", RFC 2119, March 1997.
7.2. Informative References
[2] Retana, A., White, R., Paul, M., "A Framework and Requirements
for Energy Aware Control Planes",
draft-retana-rtgwg-eacp-03.txt, (work in progress), October
2014.
[3] Recommendation ITU-T G.1080, "Quality of experience
requirements for IPTV services", December 2008.
[4] 3GPP TR 36.927, "Evolved Universal Terrestrial Radio Access
(E-UTRA); Potential solutions for energy saving for E-UTRAN
(Release 11)", September 2012.
[5] Chan, H. (Ed.) et al., "Requirements of distributed mobility
management", RFC 7333, August 2014.
[6] Communicate Green, Project website, available at
http://www.communicate-green.de
[7] LOLA project, available at
http://www.laboratories.telekom.com/public/English/
Innovation/success-stories/Pages/Energy-efficient-ICT.aspx
[8] Zhang, B. et al., "Power-Aware Networks (PANET): Problem
Statement", draft-zhang-panet-problem-statement-03.txt,
(work in progress), October 2013.
[9] Zhang, B. et al., "Power-aware Routing and Traffic
Engineering: Requirements, Approaches, and Issues",
draft-zhang-greennet-01.txt, (work in progress), January
2013.
[10] Recommendation ITU-T G.992.5, "Asymmetric digital subscriber
line 2 transceivers (ADSL2) - Extended bandwidth ADSL2
(ADSL2plus)", January 2009.
[11] Blake, S., Black, D., Carlson, M., Davies, E., Wang, Z., and W.
Weiss, "An Architecture for Differentiated Services", RFC 2475,
December 1998.
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[12] Parello, J., Claise, B., Schoening, B., and J. Quittek, "Energy
Management Framework", RFC 7326, September 2014.
[13] 3GPP TS 32.102, "Telecommunication management; Architecture
(Release 11)", December 2012.
[14] Presuhn, R., "Version 2 of the Protocol Operations for the
Simple Network Management Protocol (SNMP)", STD 62, RFC 3416,
December 2002.
[15] Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed., and
A. Bierman, Ed., "Network Configuration Protocol (NETCONF)",
RFC 6241, June 2011.
[16] Clark, A., "Guidelines for Considering New Performance Metric
Development", BCP170, RFC6390, October 2011.
[17] Liebsch, M. et al., "Quality of Service Option for Proxy
Mobile IPv6", RFC 7222, May 2014.
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Authors' Addresses
Dirk von Hugo
Telekom Innovation Laboratories
Deutsche-Telekom-Allee 7
Darmstadt 64295
Germany
Email: Dirk.von-Hugo@telekom.de
Nico Bayer
Telekom Innovation Laboratories
Deutsche-Telekom-Allee 7
Darmstadt 64295
Germany
Email: Nico.Bayer@telekom.de
Christoph Lange
Telekom Innovation Laboratories
Winterfeldtstr. 21
Berlin 10781
Germany
Email: Christoph.Lange@telekom.de
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