INTERNET-DRAFT Mingui Zhang
Intended Status: Proposed Standard Jie Dong
Expires: April 18, 2013 Huawei
Beichuan Zhang
The University of Arizona
October 15, 2012
Use Cases for Power-Aware Networks
draft-zhang-panet-use-cases-00.txt
Abstract
Power Aware NETwork (PANET) has attracted strong interest from both
carriers and vendors. Several use cases are investigated in this
document to exhibit the potential usage of PANET in both backbone and
data center networks.
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publication of this document. Please review these documents
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Conventions used in this document . . . . . . . . . . . . . 3
1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Power Awareness in Backbone Networks . . . . . . . . . . . . . 3
2.1. Use Case 1: Sleeping Links . . . . . . . . . . . . . . . . 4
2.2. Use Case 2: Composite Links . . . . . . . . . . . . . . . . 5
3. Power Aware in Data Center Networks . . . . . . . . . . . . . . 5
3.1. Server Consolidation . . . . . . . . . . . . . . . . . . . 6
3.2. Power Aware Load Balancing Among Multiple Sites . . . . . . 6
3.3. Elastic Network Infrastructure . . . . . . . . . . . . . . 7
6. Security Considerations . . . . . . . . . . . . . . . . . . . . 7
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 7
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 7
8.1. Normative References . . . . . . . . . . . . . . . . . . . 8
8.2. Informative References . . . . . . . . . . . . . . . . . . 8
Author's Addresses . . . . . . . . . . . . . . . . . . . . . . . . 9
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1. Introduction
Networks are usually provisioned for peak hours and potential network
failures and network devices are powered on all the time without
consideration on energy efficient. In practice, however, the traffic
load of a network is low most of the time and redundant network
equipments are used for failure recovery occasionally.
In the past years, vendors had paid a great effort on improving the
network energy efficiency at the device level: when the traffic load
is low, a network equipment should accordingly operate with less
power draw. However, network equipments have never become fully power
proportional. Even few or no traffic is carried, a powered-on network
device draws a considerable amount of power, which means energy is
being wasted. There is an explicit gap for idle network devices to be
shut down or put into sleeping state to save more energy. In order to
fill this gap, the network control plane and management system should
become power aware to coordinate network devices therefore the
sleeping or off network devices do not bring disruption to the
network.
This documents investigated several use cases on power aware network
which include both backbone networks and data center networks. As for
the energy efficiency of backbone networks, only intra-domain use
cases are considered. Trying to be energy efficient in the inter-
domain scale seems technically feasible, for now though, energy
efficient solutions can easily end up lack of business motivation,
this document leaves them for future study.
1.1. 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].
1.2. Terminology
PANET: Power Aware NETwork
2. Power Awareness in Backbone Networks
The IETF Energy Management (eman) Working Group works on the
management of power-aware network devices. Basically, the power
states of power-aware network devices are reported and recorded in
MIB. However, there is a gap on how to make use of this kind of data
to achieve energy efficient networks. With energy aware control plane
[power-control], it becomes possible to make use of these
measurements and power control ability to achieve the energy
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efficiency of a whole network.
This section lists several use cases for backbone networks. Take a
router system as an example, the start-up of it may take several
minutes and the stabilization of it may takes much longer time. It is
unrealistic to switch off and on a whole node in backbone networks
frequently to achieve energy efficient, so this document only
investigates the cases in which links (i.e., links' attached
components) are shut-down for energy conservation.
2.1. Use Case 1: Sleeping Links
+----------------+ +----------------+
|Router | | Router|
| | | |
| | | |
| +---------+ +---------+ |
| |Line-card| |Line-card| |
| | | | | |
| | +---+ Link +---+ | |
| | |NPU+--------+NPU| | |
+------+-----+---+ +---+-----+------+
Figure 2.1: Power Aware Line-cards
The power draw on line-cards occupies a great portion in the total
power consumption of a whole routing system. For high-end routers,
this portion may be higher than 50%.
Network devices and their processing capacity are provisioned for
worst cases such as traffic burst and busy hours. Most of the time,
the network is lightly loaded. Unfortunately, the power consumption
of network devices is not proportional to the traffic load on them.
Even there is no load on them, there is still a considerable base
power consumption. Unlike personal PCs which can be shut down or
enter power saving modes (such as sleeping), network devices are
powered on and running even they are idle. This reality means that
the network is wasting powers.
The conception that "a link is put into sleep state" is frequently
mentioned. In this document, this conception is formalized as
follows. The coupled end-points (such as interfaces, NPU or whole
line-cards) attached to a idle link (as shown in Figure 2.1) enter
the sleeping mode to save energy.
Traffic aggregation are used to create the opportunity for more links
to become idle. This process can be automated through the control
plane, such as Traffic Engineering [GreenTE].
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The essentials of this use case:
o Devices to be Power Aware: Routers and their line-cards.
o What actions to take: NMS measures the traffic load and power
profile each link [eman]; Routers execute the green TE algorithm;
Routers send out signals to trigger the power-on/power-off of a
NPU on a line card.
2.2. Use Case 2: Composite Links
A composite link is logical link composed of multiple physical [I-
D.ietf-rtgwg-cl-requirement]. The composite link attached end-points
are responsible to map traffic onto the component links and maintain
the state of the composite link. Power awareness can be applied to
composite links as well. When the traffic volume on the composite
link is low, some component links can be shut down to conserve energy
consumption. When the traffic volume becomes high, the sleeping
members links can be waken up to absorb the traffic load.
Compared to use case 1, the advantage of executing energy saving for
composite link is that the connectivity of the composite link does
not suffer unless all the component links are cut off. In this way,
the control plane of the component link is not disrupted. In other
words, when the end points of the composite link execute the energy
conservation action, they can do it in a distributed way and
decisions are made locally.
The essentials of this use case:
o Devices to be Power Aware: Composite links attached end-points.
o What actions to take: NMS measures the traffic load and power
profile of component links; Attached end-points adaptively turn-
on/turn-off component links according to the traffic load on the
composite link.
Use case 1 and use case 2 may be combined in a real network to
achieve more energy saving.
3. Power Aware in Data Center Networks
Servers, network devices (ICT equipments) are intensively placed in
Data Centers. In comparison with ISP backbone networks, the operating
of Data Center Networks are more power hungry. The growing amount of
energy consumed by a Data Center has led to high operating costs.
Although non-ICT equipments, such as lighting and air conditioners,
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in a Data Center consumes a notable large amount of energy as well,
this section concentrate on talking about right sizing ICT equipments
for energy conservation. Energy conservation of non-ICT equipments
are out of the scope of this document.
3.1. Server Consolidation
With virtualization technology, Virtual Machines (VMs) can be
consolidated to fewer physical servers while idled servers can be put
into power saving mode or turned off to achieve energy conservation
of the whole Data Center. Virtualization technology allows the
administration of a Data Center Network respond rapidly to the
fluctuating capacity requirements.
Through monitoring of the work load and power profile, the Data
Center Network Management System (Orchestrator) can judge in which
hours workload is high and in which hours workload is low. For
example, nights are generally off-peak hours in which workload is at
low level. Virtual machines can be moved to fewer servers therefore
idle servers can powered off or put into sleep to save energy. Before
peak hours (e.g., in the morning), sleeping or powered off servers
should be waken up to accommodate more active virtual machines
(VMs).
The essentials of this use case:
o Devices to be Power Aware: All servers in a data center.
o What actions to take: NMS measures the work load and power profile
of servers; The orchestrator of a Data Center Network adaptively
triggers the actions of VM migration, the power-off and power-on
of servers according to the workload.
3.2. Power Aware Load Balancing Among Multiple Sites
An enterprise may have multiple data centers which spread out in
different geographic locations. Generally, the ICT resources in these
data centers are well replicated and a job can be directed to any of
them for execution. These data centers form a large distributed
Internet scale systems and the price of power supply for them varies
between two different locations. The operating cost of such a system
highly depends on the load balancing scheme. Being power aware, the
system can map requests to locations where energy price is cheaper.
This use case makes use of the difference of the prices of power draw
in different locations. The orchestration of data centers (the NMS)
is responsible for monitoring the power profile and work load of the
ICT devices located in different data centers.
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The essentials of this use case:
o Devices to be Power Aware: All ICT-equipments in a data center.
o What actions to take: ICT devices report their work load and power
consumption profile to NMS. The orchestration (NMS) of the Data
Center Networks adaptively map the request onto sites in
consideration of reducing the overall power bill of the system.
3.3. Elastic Network Infrastructure
Traffic load of a data center is generated by the work load on
servers and applied on the network infrastructure. The changing work
load determines that the traffic load varies as time goes on.
However, network devices are always left on even though the traffic
load fluctuates, which wastes energy inevitably when the traffic load
is low.
Ideally, the network infrastructure is elastic and can fit the
traffic pattern with minimum subset to minimize the energy
consumption of the network infrastructure. For now, Data Center
Networks generally work at layer 2. So this use case should be
realized through manipulating switching paths, in comparison with the
power aware routing at layer 3. Openflow switches of SDN may be
utilized to achieve this goal [ElasticTree].
The essentials of this use case:
o Devices to be Power Aware: All network equipments in a data
center.
o What actions to take: Network devices report their traffic load
and power consumption profile to NMS. The orchestrator (NMS) of a
Data Center Network adaptively build the switching paths upon the
network infrastructure. The idled links are put into power saving
mode (e.g., sleeping), so that the network infrastructure becomes
energy efficient.
6. Security Considerations
This document raises no new security issues.
7. IANA Considerations
No new registry is requested to be assigned by IANA. RFC Editor:
please remove this section before publication.
8. References
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8.1. Normative References
[power-control] A. Retana, R. White, M. Paul, "A Framework and
Requirements for Energy Aware Control Planes", draft-
retana-rtgwg-eacp-00.txt, work in progress.
[eman] IETF, "Energy Management Working Group Charter", 2012,
<http://datatracker.ietf.org/wg/eman/charter/>.
[I-D.ietf-rtgwg-cl-requirement] Villamizar, C., McDysan, D., Ning,
S., Malis, A., and L. Yong, "Requirements for MPLS Over a
Composite Link", draft-ietf-rtgwg-cl-requirement-07 (work
in progress), June 2012.
8.2. Informative References
[GreenTE] Zhang, M. and et al. , "GreenTE: Power-Aware Traffic
Engineering", ICNP 2010.
[Rate-Adaptation] S. Nedevschi, L. Popa, G. Iannaccone, S. Ratnasamy,
and D. Wetherall, "Reducing Network Energy Consumption via
Sleeping and Rate-Adaptation," in Proceedings of USENIX
NSDI, 2008.
[ElasticTree] B. Heller, S. Seetharaman, P. Mahadevan, Y. Yiakoumis,
P. Sharma, S. Banerjee, and N. McKeown, "ElasticTree:
Saving Energy in Data Center Networks," in Proceedings of
USENIX NSDI, 2010.
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Author's Addresses
Mingui Zhang
Huawei Technologies Co.,Ltd
Huawei Building, No.156 Beiqing Rd.
Beijing 100095 P.R. China
Email: zhangmingui@huawei.com
Jie Dong
Huawei Technologies Co.,Ltd
Huawei Building, No.156 Beiqing Rd.
Beijing 100095 P.R. China
Email: jie.dong@huawei.com
Beichuan Zhang
The University of Arizona
Email: bzhang@cs.arizona.edu
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