Network Working Group T. Suzuki
Internet-Draft T. Tarui
Intended status: Informational Hitachi, Ltd.
Expires: April 18, 2013 October 15, 2012
Requirements for an Energy-Efficient Network System
draft-suzuki-eens-requirements-00
Abstract
Requirements concerning an energy-efficient network system such as a
cloud system are presented. Specifically, a large-scale cloud
system, which is composed of multiple data centers (DCs) and a wide
area network (WAN) to connect these DCs, is focused on. The problems
needed to be overcome in order to make the system energy efficient
are presented. The requirements that must be satisfied in order to
solve these problems are also presented.
Status of this Memo
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This Internet-Draft will expire on April 18, 2013.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Problem Statement . . . . . . . . . . . . . . . . . . . . . . 4
3. Use Case . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
3.1. Management System Structure . . . . . . . . . . . . . . . 5
3.2. Server Function . . . . . . . . . . . . . . . . . . . . . 6
3.3. Power-saving Method on a large scale cloud system . . . . 7
4. Requirements . . . . . . . . . . . . . . . . . . . . . . . . . 8
5. Security Considerations . . . . . . . . . . . . . . . . . . . 9
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10
7. Informative References . . . . . . . . . . . . . . . . . . . . 11
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 12
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1. Introduction
This draft describes the requirements that an energy-efficient
network system must satisfy. An example of the network system is a
cloud system.
Recently, cloud services, which provide various resources to distant
data centers (DCs), such as processing power, storage, and
applications, via a network have become wide-spread around the world.
The users of cloud services have been increasing in proportion to the
enhancement of the services. Besides, the number and the scale of
cloud systems have also been increasing in accordance with the growth
of the number of users. As a result of these trends, the power
consumed by the systems has risen dramatically, and devising power-
saving measures targeting the systems has become one of the biggest
issues.
Under those circumstances, the requirements concerning a power-saving
cloud system to guarantee network-access quality to a virtual machine
(VM) are described in this draft. A power-saving cloud system is
created by reallocating all VMs appropriately in the system in order
to save power on the basis of cooperation between a DC management
server and a network management server. The requirements concerning
power saving at the network level are described here while the
requirements concerning the device level are still being discussed by
the EMAN [EMAN] working group.
In section 2, specific issues on the network level are discussed. In
section 3, a usage case for a power-saving cloud system is described.
In section 4, requirements that the system must satisfy are
prescribed.
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2. Problem Statement
One way to create a power-saving cloud system is to consolidate
working physical servers by appropriate VM migrations. In a VM
migration, many VMs are accommodated in the same physical server
while the load of the CPU for each VM is low. Unnecessary physical
servers are then shut down, and power consumption of the entire
system is cut.
In regard to a conventional power-saving method, reallocation of the
VMs is determined on the basis of the load of only physical servers
and VMs. Service quality is therefore guaranteed from the
perspective of CPU load. However, network congestion is possible
when excess consolidation based on VM migrations is executed without
considering the load corresponding to the network resource (such as
bandwidth) even if enough CPU resources are available.
Power-saving control for a cloud system should therefore be done
while service quality is guaranteed. To do that, power-saving
control must be executed from the perspective of not only CPU load
but also network load. However, a method or protocol for
communication between a DC management server and a network management
server has not been defined yet.
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3. Use Case
3.1. Management System Structure
A target cloud system for power saving is shown in Figure 1. The
system is composed of multiple DCs and a wide area network (WAN)
connecting the DCs. An example of a management system for cloud-
system power-saving is shown in Figure 2. In the example, there is a
WAN management server on the WAN side and multiple DC sub-management
servers and a DC main-management server on the DC side.
+---------------------------------------------------+
| |
| Wide Area Network (WAN) |
| |
+----------+-----------------------------+----------+
| |
| |
| |
+----------+----------+ +----------+----------+
| | | |
| Data Center (1) | - - - | Data Center (n) |
| | | |
+---------------------+ +---------------------+
Figure 1: Example of a target cloud system
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+---------------------------------------------------+
| WAN Mgmt Srv |
+-------------------------+-------------------------+
|
|(1) WAN-DC I/F
|
+----------+--------------+-------------------------+
| DC Main-Mgmt Srv |
+----------+-----------------------------+----------+
| |
|(2) DC Main-Sub I/F |(2) DC Main-Sub I/F
| |
+----------+----------+ +----------+----------+
| | | |
| DC Sub-Mgmt Srv (1) | | DC Sub-Mgmt Srv (n) |
| +-------+ |
+---------------------+ +---------------------+
(3) DC-DC I/F
Figure 2: Example of a management system
3.2. Server Function
In this section, a function for each management server shown in
Figure 2 is described in concise way.
WAN Management Server:
The WAN managemnet server monitors available bandwidth for each
node and consumed bandwidth by each VM in the WAN and predicts
future loads for each resource. In addition, it calculates the
minimum necessary number of data-routing paths and bandwidth on
the basis of the monitored resource conditions and predicted
future load for each resource. The number of routing paths is
then consolidated accordingly.
DC Main-Management Server:
The main-management sever controls the start and end times of
the VM consolidation for power saving of all DCs by utilizing
the huge difference in the CPU loads on the servers during
business hours and during the night. In addition, it manages
other DC sub-management servers.
DC Sub-Management Server:
The sub-management server monitors available bandwidth for each
node and consumed bandwidth by each VM and predicts future
loads for each resource. It then calculates minimum necessary
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number of physical servers to accommodate all VMs (some of
which are under low load late at night). Next, it reallocates
them appropriately on the basis of the monitored resource
conditions and predicted future load for each resource. It
then consolidates routing paths according to the minimum number
of necessary routing paths and bandwidth.
3.3. Power-saving Method on a large scale cloud system
The following four methods can be used for power saving.
1. The power consumption of the DC is saved by turning off
unnecessary physical servers after appropriate VM reallocation
for the physical servers based on VM migrations while the quality
of service (QoS) of the cloud services provided by the DC is
guaranteed.
2. The power consumption of the DC is saved by turning off
unnecessary physical servers and nodes or their ports on
unnecessary data-routing paths after appropriate VM reallocation
in the DC while QoS of the cloud services is guaranteed.
3. The power consumption of the DC is saved by turning off
unnecessary physical servers after appropriate VM reallocation
for the physical servers based on VM migrations between DCs while
QoS of the cloud services is guaranteed.
4. The power consumption of the DC and WAN is saved by turning off
unnecessary physical servers and nodes or their ports on
unnecessary data-routing paths after appropriate VM reallocation
between DCs while QoS of the cloud services is guaranteed.
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4. Requirements
The interfaces shown in Figure 2 are needed to create the power-
saving cloud system based on the schemes described in the previous
section. The requirements for each interface are briefly described
below.
WAN-DC Interface:
The interface is used to transmit information concerning a
change in the conditions of the network and server resources
(including VMs) in the DC from the DC management server to the
WAN management server. In addition, by accessing the WAN
management server, the DC management server uses the interface
to determine if any problems occur in the WAN when the planned
VM migration is executed.
DC Main-Sub Interface:
The interface is used by the DC main management server to
inform the DC sub-management server to start or stop power-
saving control for the network and server resources (including
VMs) in each DC. In addition, the DC sub-management server
uses the interface to determine if any problems occur in the
WAN when the planned VM migration over the DCs is executed via
the WAN-DC interface.
DC-DC Interface:
The interface is used to determine appropriate reallocations of
network and server resources by exchanging conditions of each
resource (such as the load on the CPU of the physical server
and VMs and availability of network bandwidth in the DC).
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5. Security Considerations
This document describes problems and requirements for a power-saving
large-scale network system. To achieve this power saving, it is
necessary to exchange information on the resource conditions in the
WAN and DC between management servers in the WAN and DC. It is
therefore necessary to use a secure communication channel between
management servers.
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6. IANA Considerations
This document includes no request for IANA.
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7. Informative References
[EMAN] "EMAN Working Group".
<http://datatracker.ietf.org/wg/eman/>
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Authors' Addresses
Toshiaki Suzuki
Central Research Laboratory, Hitachi, Ltd.
292 Yoshida-cho
Totsuka-ku, Yokohama, Kanagawa 244-0817
Japan
Phone: +81-45-860-2177
Email: toshiaki.suzuki.cs@hitachi.com
Toshiaki Tarui
Central Research Laboratory, Hitachi, Ltd.
292 Yoshida-cho
Totsuka-ku, Yokohama, Kanagawa 244-0817
Japan
Phone: +81-45-860-2177
Email: toshiaki.tarui.my@hitachi.com
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