Server congestion control

International Journal of Computer Networks & Communications (IJCNC) Vol.7, No.5, September 2015
DOI : 10.5121/ijcnc.2015.7507 83
SERVER CONGESTION CONTROL
AND REDUCTION OF SERVER
POWER CONSUMPTION WITH DPI
TECHNOLOGY
Shin-ichi Kuribayashi
Department of Computer and Information Science, Seikei University, Japan
ABSTRACT
Deep packet inspection (DPI) technology has conventionally been introduced for traffic monitoring,
bandwidth control, access control of specific types of traffic, etc. As a new potential application of DPI
technology, this paper proposes three promising approaches of network and server control with DPI
technology, and presents implementation examples of two approaches. These approaches could
simplify dramatically the conventional work load for system management and reduction of power
consumption by servers and accelerate the control action.
First, this paper proposes an example of server congestion control method, in which the DPI equipment
estimates the CPU usage of each server by constantly monitoring the number of TCP live connections
established by each server, and moves some of virtual machines on the congested server to other
servers through remote control timely. Next, this paper proposes an example of reducing power
consumption by servers, in which the DPI equipment constantly monitors the traffic sent or received in
each area with multiple servers. Finally, the feasibility of the proposed approaches is demonstrated by
an evaluation system with a real DPI equipment.
KEYWORDS
Deep packet inspection, congestion control, reduction of power consumption
1.INTRODUCTION
Deep Packet Inspection (DPI) has been a very important research topic within the traffic
classification field. Its concept consists of the analysis of the contents of the captured
packets in order to accurately and timely discriminate the traffic generated by different
Internet protocols. That is, DPI monitors the data parts (payloads) of IP packets and to
determine the type of processing to be applied to packets, such as filtering, based on the
content of the payloads [1],[2]. A variety of data, such as email messages and videos, are
exchanged using HTTP in the internet. DPI can inspect URLs, content of messages, and
packet information that is at a layer higher than that for information used for conventional
packet filtering. This capability of DPI also makes it possible to take more finely tuned
security measures than before, such as detection of viruses that attempt to invade using
HTTP or prevention of information leakage in enterprises.

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DPI technology has conventionally been introduced for traffic monitoring, bandwidth
control, bandwidth allocation, control of specific types of traffic, etc [3],[4]. A lot of service
providers are adopting the DPI equipment for securing the visibility of the data traffic, due to
the dramatic increase of data traffic in mobile networks [5]. For example, peer-to-peer (P2P)
traffic would give ISPs a great deal of trouble and DPI allows the ISP to perform traffic
control and bandwidth allocation.
In recent years, there have been intense studies to use DPI to enhance charging (charging
based on usage or data content, etc.) or security (identifying types of traffic and encrypting
them accordingly, etc.). There have also been studies to combine DPI with different
technologies in order to identify types of traffic and use this information for behavior-based
targeted advertising [4], in which sites browsed, products purchased, or search key words
used by Internet users are collected and analyzed.
DPI equipment installed at any arbitrary point in a network can monitor communications of
many servers simply and analyze the type of processing to be applied to packets without
packet capture tools and skilled engineers in every server. This could simplify dramatically
the conventional work load for system management and reduction of power consumption by
servers and accelerate the control action. Moreover, DPI functions can be virtualized and
deployed on commodity hardware as a piece of software with Network Functions
Virtualization (NFV) [5]. It enables to rapidly scale up (or down) the deployment of DPI
functions economically [6], as it only requires the installation of virtual appliances on
existing server equipment.
This paper explores the possibility of applying DPI technology to the server control and the
reduction of power consumption. The rest of this paper is organized as follows. Section 2
explains related works. Section 3 proposes three promising approaches of network and server
control with DPI technology. Section 4 proposes an example of server congestion control
with DPI technology and demonstrates it by the evaluation system with a real DPI
equipment. Section 5 proposes an example to apply DPI technology to the reduction of
power consumption by servers and demonstrates it by the evaluation system with a real DPI
equipment. Section 6 presents the conclusions. This paper is an extension of the study in
Reference [18].
2.RELATED WORK
Reference [3] summarizes potential uses of DPI technology as follows:
 Network security: DPI's ability to inspect data streams at such a granular level will
prevent viruses and spyware from either gaining entrance to a network or leaving it.
 Network access: DPI creates conditions where network access rules are easy to
enforce due to the deep inspection of packets.
 SLA enforcement: ISPs can use DPI to ensure that their acceptable use policy is
enforced. For example, DPI can locate illegal content or abnormal bandwidth usage.
 QoS: P2P traffic gives ISPs a great deal of trouble. DPI would allow the ISP to
instigate traffic control and bandwidth allocation.
 Tailored service: DPI allows ISPs to create different services plans, which means
users would pay for a certain amount of bandwidth and traffic priority.

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 DRM enforcement: DPI has the ability to filter traffic to remove copyrighted
material. There's immense pressure from the music and movie industries to make
ISPs responsible for curtailing illegal distribution of copyrighted material.
Reference [6] has proposed a network management system with DPI server which supports
the network management system to classify the network traffic. For example, if the DPI
equipment finds that the user id of the VoIP session is in the black list, the DPI equipment
informs the NMS about this SIP session. Then the NMS configures related switches to
intercept that VoIP session. Reference [5] has proposed to apply DPI technology to the
CDMA mobile network packet switch domain and constructed a DPI based network traffic
monitoring, analysis and management system. References [7] and [8] has presented a
technical survey for the implementation and evaluating of traffic classification modules
under a common platform. Reference [9] has proposed a method that enables to find out a
DPI engine deployment that satisfies the trade-off between the minimum number of engines
and the minimum network load for a considered set of costs and operational constraints.
Reference [10] has described the hardware and software components of the platform of DPI
with its four utilization fields. Reference [11] has proposed a method, based on genetic
algorithms, that optimizes the cost of DPI engine deployment, minimizing their number, the
global network load and the number of unanalyzed flows.
Most of these studies mainly try to restrict transfer of specific types of traffic. To the best of
our knowledge, applying DPI technology to server congestion control and the reduction in
server power consumption has not been fully studied.
3.THREE PROMISING APPROACHES OF APPLYING DPI
TECHNOLOGY TO NETWORK AND SERVER CONTROL
Today, identifying the types of application used in each server in a data center requires
sophisticated processing and a considerable workload. For example, it is necessary to
introduce a packet capture tool in each server and to have skilled engineers analyze packets
used by different applications. DPI can simplify this, because it is possible to analyze in
detail the content of data that flow in the network just by installing DPI equipment at any
arbitrary point in a network. There is no need to introduce a packet capture tool and skilled
engineers in every server. It is easy to identify the type of application used and the
characteristics of its traffic, such as communication content and communication time. It is
performed without any access to individual servers. In addition, DPI makes it possible to
simultaneously monitor many servers scattered over a wide area and control the network from
a network-wide perspective.
Three promising approaches of applying DPI technology to network and server control are as
follows:
<Case 1> Server Congestion Control
An image of server congestion control with DPI technology is illustrated in Figure 1. The
DPI equipment in the network monitors traffic related to server #1 and estimates the
following values:

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 CPU utilization of server #1 and VM in the server #1
 Utilization of bandwidth used for server #1
For example, if DPI equipment monitored traffic related to server#1 and estimated that server
#1 is in a congested state, the following actions could be taken to maintain QoS:
 Move virtual machine on the congested server to other uncongested servers (① in
Figure 1)
 Reduce the bandwidth available to virtual machine that is causing the congestion (②
in Figure 1)
This approach could simplify dramatically the conventional work load for system
management and accelerate the control action.
<Case 2> Reduction Of Power Consumption By Servers
Server administrators need to handle considerable workloads if they monitor traffic and
instruct maintenance staff to put the server concerned to sleep mode or shut it down, upon
detecting absence of traffic (except for monitoring packets) in a server for a certain period. If
a DPI equipment is applied instead, the communication states of many servers can be
monitored easily and timely from a single point in the network, and, based on that
information, servers that are not handling traffic can be put in sleep more or shut down
automatically through remote control.
An image of reduction of power consumption by servers with DPI technology is illustrated in
Figure 2. In this example, the DPI equipment installed in the network constantly monitors the
volume of traffic carried in areas A, B and C. Each area has multiple servers. When the DPI
equipment detects an area that carries no traffic except for monitoring packets, it either puts
all servers in the area to sleep mode or shut them down. On the contrary, DPI equipment
remotely turns on the server with Wake-on-LAN (WOL) [12], when it monitors the start of
traffic flow to the server. This approach could reduce power consumption simply and timely,
compare with the conventional method with maintenance staffs.
<Case 3> Link Congestion Control In The Network
An image of link congestion control with DPI technology is illustrated in Figure 3. The DPI
equipment in the network monitors traffic flows and estimates the utilization of each link on
the route. If the utilization exceeds the threshold, DPI equipment judges the risk of link
congestion and makes a preparation for detouring specific flows on another non-congested
route. Assuming SDN-based network [13],[14], DPI equipment requests SDN controller to
set flow entries at each SDN node (switch) on the alternate route. Then, node x in this
example detours specific flows to the alternate route and it could avoid link congestion.
These approaches can avoid link congestion in the network simply and timely, compare with
the conventional method with maintenance staffs.
Implementation examples of the above two cases, case 1 and case 2, are proposed in
Section 4 and Section 5 respectively.

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Figure 1. Image of server Congestion control with DPI technology(Case 1)
Figure 2. Reducing power consumption of server with DPI technology(case 2)

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Figure 3. Image of link congestion control by detouring specific flows(Case 3)
4. SERVER CONGESTION CONTROL WITH DPI TECHNOLOGY
4.1 Example of server congestion control method (Example of Case 1)
Applications could be classified into a ‘bandwidth type’ (applications that use a large bandwidth)
and a ‘transaction type’ (applications that demand high CPU usage). As for bandwidth type, DPI
equipment can estimate applications and bandwidth used for each server. For example, if the
amount of bandwidth for videos exceeds a certain threshold, it is possible to reduce bandwidth for
the server which handles videos. The monitoring example of traffic volume of each application is
illustrated in Figure 4. In this example, the traffic volume of HTTP download exceeded the
threshold and it is required to reduce bandwidth to the VM (virtual machine) which processes
HTTP download application.

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Figure 4. Total bandwidth measured by DPI equipment
As for transaction type, the following procedure is proposed, assuming the scenario in Figure 1.
It is also assumed that DPI tool installed in the network monitors and controls a physical server
(server #1) in which a number of virtual machines are implemented. A detailed processing flow is
shown in Figure 5.
<Step 1> The DPI equipment monitors the type (video on demand (VoD), peer-to-peer (P2P),
Web access, etc.) of application running on each virtual machine in server #1. It is assumed that
the DPI equipment knows in advance the relationship between the number of transactions and
CPU utilization in server #1.
<Step 2> The DPI equipment constantly monitors the number of transactions handled in server #1
per unit time. If the number exceeds a certain threshold (which is preset for each physical
machine based on its normal usage) for more than a certain period, the tool determines that the
service is in an overload state. It either moves the VM associated with the specific application
(e.g., VoD, P2P) responsible for the overload to another physical server (server #2) (①in Figure 1).
Alternatively, if that is not possible, the tool reduces the bandwidth used by the traffic to and from
the VM (②in Figure 1). These measures can resolve congestion in server #1.
<Step 3> The DPI equipment continues to monitor the number of transactions on server #1
constantly. When the number goes down below the threshold, the tool releases the restriction
imposed in Step 2 above.

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Figure 5. Processing flow of the proposed server congestion control with DPI technology
4.2 Evaluation of the proposed server congestion control method
(1) Evaluation system
To evaluate the server congestion control method proposed in Section 4.1, the evaluation system
shown in Figure 6 is constructed. NetEnforcer AC-502 [15] from Allot Communications is used
as the DPI equipment. A software program (NetXplorer) that monitors AC-502 is installed in an
NX server. As AC-502 is not able to collect the number of transactions per unit time in each
server, the number of TCP live connections per unit time is used estimate CPU usage instead.
Every minute AC-502 measures the number of TCP live connections between the client terminal
and the source server. This information is collected by DPI tool (software) that is installed in the
NX server.
Figure 7 illustrates the actual evaluation system constructed. Dell PowerEdge T110 with
Windows Server 2008 is used as NX server, and Dell Vostro3350 (Intel Core i3, CPU 2.27GHz)
is used as client terminal and servers. VirtualBox [16] is used as a virtual system, and both host
OS and guest OS are Windows 7.
(2) Effectiveness of using the number of TCP live connections
An example of the relationship between the number of TCP live connections (Web-based
applications with TCP) and the CPU utilization in the source server is shown in Table 1. This
example shows a high coefficient of correlation (around 0.9), indicating a good possibility of
determining the degree of server congestion from the number of TCP live connections.

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(3) Evaluation of the proposed server congestion control method
The operation of the proposed method was verified under the following conditions:
1)The evaluation tool monitors the number of TCP live connections every minute in source server.
Fig 6. Configuration of evaluation system
Figure 7.Overview of developed system for evaluation

92
Table 1.Example of measured CPU utilization
2) When the number of TCP live connections exceeded 55 (this is determined based on data in
Table 1) continuously for 3 minutes on end, a VM on the source server is moved (live-migration)
to destination server. The evaluation tool installed in an NX server remotely instructs both the
source and the destination server to migrate virtual machines, with PsExec[17] from Microsoft.
It is confirmed that the proposed method operated as had been expected, and it means that DPI
technology can allow the server congestion control without packet capture tool and skilled
engineers in every server.
(4) Scalability of the proposed method
As mentioned in Section 1, DPI functions can be virtualized and deployed only at the time when
needed with NFV. It enables to rapidly scale up (or down) the deployment of DPI functions in
the network economically, as it only requires the installation of virtual appliances on existing
server equipment.
5. USE OF DPI TECHNOLOGY FOR REDUCTION OF SERVER
POWER CONSUMPTION
The proposed method of reducing power consumption by servers is explained with Figure 2. The
DPI equipment installed in the network constantly monitors the volume of traffic carried in areas
A, B and C. Each area has multiple servers. When the tool detects an area that carries no traffic
except for monitoring packets, it either puts all servers in the area to sleep mode or shut them
down. This reduces power consumption by servers in that area simply and timely, compare with
the conventional method with maintenance staffs. Figure 8 illustrates a processing flow of the
proposed method.
The proposed method was evaluated by reusing the evaluation system described in Section 4
under the following conditions:
 Instead of source and destination servers in Figure 7, three servers (each represents
one area) are added to the evaluation system.

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 The DPI equipment constantly monitors the volume of traffic carried in each area. If it
detected an area where there was no traffic (except for monitoring packets) for 10
minutes or longer, it remotely shut the server down with PsExec [17] from Microsoft.
Figure 8.Processing flow for reducing power consumption of server with DPI technology
It is confirmed that power consumption is reduced as had been expected. Moreover, it is also
confirmed that DPI equipment can remotely turn on the server with WOL technology.
6. CONCLUTIONS
As a new potential application of DPI technology, this paper has proposed three promising
approaches of network and server control with DPI technology. The proposed approaches could
simplify dramatically the conventional work load for system management and reduction of
power consumption by servers and accelerate the control action.
This paper has proposed an example of server congestion control method, in which the DPI
equipment at any arbitrary point in a network estimates the CPU usage of each server by
constantly monitoring the number of TCP live connections established by each server, and moves
some of virtual machines on the congested server to other servers through remote control timely.
Next, this paper has proposed an example of reducing power consumption by servers, in which
the DPI equipment constantly monitors the traffic sent or received in each area with multiple
servers and put all servers in that area to shut them down remotely. The feasibility of two
proposed approaches was demonstrated by an evaluation system with a real DPI equipment.
As NFV technologies enables to rapidly scale up (or down) the deployment of DPI functions in
the network economically, the proposed methods have a scalability in larger network constructed
with NFV technologies. However, it will be necessary to investigate the effectiveness of the
proposed methods further and to study total network congestion control and reduction of power
consumption by network equipment with DPI technology.

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ACKNOWLEDGMENT
We would like to thank Mr. Kohei YANAGISAWA and Mr. Hirohumi KUBOTA for their help
with the evaluation.
REFERENCES
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functions in SDN,” MILCOM2013, Vol.32, No.1, Nov.2013
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[16] VirtualBox https://www.virtualbox.org/
[17] Windows Sysinternals “ PsExec” https://technet.microsoft.com/ja-jp/sysinternals/ bb897553.aspx
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Author
Shin-ichi Kuribayashi received the B.E., M.E., and D.E. degrees from Tohoku University,
Japan, in 1978, 1980, and 1988 respectively. He joined NTT Electrical Communications
Labs in 1980. He has been engaged in the design and development of DDX and ISDN
packet switching, ATM, PHS, and IMT 2000 and IP-VPN systems. He researched
distributed communication systems at Stanford University from December 1988 through
December 1989. He participated in international standardization on ATM signaling and IMT2000 signaling
protocols at ITU-T SG11 from 1990 through 2000. Since April 2004, he has been a Professor in the
Department of Computer and Information Sci ence, Faculty of Science and Technology, Seikei University.
His research interests include optimal resource management, QoS control, traffic control for cloud
computing environments and green network. He is a member of IEEE, IEICE and IPSJ.

Server congestion control

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