A QoS-aware Residential Gateway with Bandwidth Management

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IEEE Transactions on Consumer Electronics, Vol. 51, No. 3, AUGUST 2005

Contributed Paper

A QoS-aware Residential Gateway with Bandwidth Management

Wen-Shyang Hwang and Pei-Chen Tseng, Member, IEEE

Abstract — The Residential Gateway (RG) is the core device of the digital home network. The RG translates communication protocols, coordinates information sharing and serves as a gateway to external networks for integrated multimedia entertainment, on-line services, home security, home automation, information exchange and data storage. Modern home network applications especially for real-time are demanding guaranteed Quality of Service (QoS) for bounded network bandwidth resources. In order to initiate a DiffServ-QoS (Differentiated Services-QoS) bandwidth management mechanism during network congestion, this paper proposes a QRG (QoS-aware Residential Gateway) with both real-time traffic monitoring, DiffServ-QoS and CBQ bandwidth management. Firstly, QRG classifies traffic flow into separate types, with specialized treatment per traffic type to optimize compliance with user-specified priorities. Applications with higher priority get the right to deliver first. Additionally, QRG with built-in traffic control function adopts Class Based Queuing (CBQ) as DiffServ-QoS bandwidth/traffic management for optimized use of bounded network resources. QRG is experimentally implemented on a Linux platform. High-end application is simulated by hosting QRG in a general-purpose PC, while minimum-cost modular application is simulated by hosting QRG in a light-weight low-power ARM920T embedded system. Results show that in both implementations, QRG successfully performs DiffServ-QoS and CBQ bandwidth management functions so that good quality of service and video performance are maintained during network congestion. 1

Index Terms—Residential Gateway, Home Network, QoS, Embedded System.

I. INTRODUCTION

The modern home is evolving rapidly into a digital home network environment. Inter-device data communication and Internet connectivity are penetrating the home as personal computers, video telephonic systems, networked home entertainment systems, home security systems and a variety of smart devices for both home automation and home digitalization. A probable result of this convergence is the digital home wherein the dweller is able to enjoy networked content at any place at any time by any device. A recent consumer survey [1] indicated that the contemporary

1_{This work is supported under Grant No. NSC 93-2745-E-151-001 and} NSC 93-2218-E-151-005 conducted by National Kaohsiung University of Applied Sciences under the sponsorship of the National Science Council, Taiwan, ROC.

Wen-Shyang Hwang and Pei-Chen Tseng are now with Department of Electrical Engineering, National Kaohsiung University of Applied Sciences, Kaohsiung, Taiwan (E-mail: wshwang@mail.ee.kuas.edu.tw, peichen@wshlab2.ee.kuas.edu.tw).

American PC-owning family still spends around 70% of its electronic media-device time in the living room and only 30% using the PC. Of PC usage, about 56% is for listening to music, 45% for managing and editing personal photos, 32% for burning MP3 music and 20% for watching DVD content. The high percentage of family PC time spent for media use indicates a huge new market is emerging from the fusion of PC and A/V (Audio/Video) multimedia. But the reality of implementation poses many challenges, including the problems of set-up and interoperation of devices and systems with different hardware and vender-dependent standards. Proprietary systems do not create category growth and industry standards alone do not ensure interoperability. Limited interoperability increases consumer resistance and the demand for solutions.

The present in-home networking field has more than 50 candidate technologies, which can be divided into those requiring new wires (i.e. IEEE 1394, Ethernet, USB), no new wires (i.e. ApBus, X-10, CEBus, Lonworks, PLC) and wireless (i.e. IEEE 802.11, Bluetooth, IrDA, HomeRF) [2]. Many groups such as EchoNet, OSGi, DHWG and CELF [1] are working to drive convergence of the future digital home network despite different points of view regarding platform, open standards and technical specifications. Their goals can be summarized as:

z Open standards and open service platforms to interoperate among different technologies;

z Central network server to integrate multimedia entertainment, on-line games, information exchange and storage features;

z Networked-home transmission such as WLAN and Ethernet implementation within home networking. The demand for improved digital home networking technologies has lead to continuous discussions such as OSGi [3]-[7] and EchoNet [6] led by important consumer electronics manufactures as they move towards mass-market home servers. Microsoft’s Windows XP 2005 PC media center integrates consumer electronics and PC-related products to achieve any-connection any-time any-place any-device performance. Intel’s Entertainment PC and Sony’s PS3 likewise aim at establishing ubiquitous home media centers by integrating entertainment and networking features. Because of the universal appeal of consumer electronics, TV, personal computers and the Internet, it is only a matter of time before these various devices converge into a cost-effective integrated home network with seamless interoperability.

The Residential Gateway (RG) is the core device at the heart of the home network. It functions not only as the information exchange and control center to allow transfer of different communication protocols and the sharing of information in the home network, but it also functions as a

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W.-S. Hwang and P.-C. Tseng: A QoS-aware Residential Gateway with Bandwidth Management 841

gateway to connect to external networks. The RG in the integrated heterogeneous home networking environment may transport data, audio/video, home control and multimedia entertainment services. At the same time, the RG must deal with broadband access technology and the well-known ‘last mile problem’ to the digitally networked house. For successful design, the RG must be able to cope with the various access infrastructures such as copper enhancements (Digital Subscriber Line; xDSL), Fiber-To-The-Home (FTTH) and Wireless Local Loop (WLL) [2]. The new barrier to end-to-end broadband service provisioning is the home network. For example, the bandwidth inside the home can be over 400 Mbps (e.g. Home Audio/Video interoperability (HAVi) [8] based on IEEE 1394), but bandwidth of the access network is generally below 2 Mbps (e.g. ADSL).

Since its creation in the early 1970s, the Internet has used the straightforward delivery service called “Best Effort (BE).” This can be explained by quoting an article that appeared in the UK-based Network News [9]: “IP was not designed with QoS in mind, so every single packet that is transmitted is treated in exactly the same way. This is fine for basic data transfers that are not time dependent, but if IP is, as many people predict, to be the protocol of the future, then QoS will be a hugely important factor in its success.” For deal with this requirement, IETF (Internet Engineering Task Force) proposed two types of QoS (Quality of Service): Integrated Service (IntServ) [10] and Differentiated Service (DiffServ) [11].

IntServ, developed in the early and mid-1990s, provides the ability to give individual flows absolute QoS guarantees on packet delays (delay bounds) and packet losses (no loss) as long as the traffic of each flow conforms to a pre-specified set of parameters [12]. IntServ reserves network resources along the entire path for per-flow end-to-end guarantee, but this leads to scalability problems which become more serious with increasing requests for various network applications.

Consequently, in the second half of the 1990s there was a shift of QoS focus to DiffServ architecture, which makes a distinction between operations performed in the network core and operations performed at the edges of the network. DiffServ provides a scalable scheme by classifying Per-Hop Behavior (PHB) on the basis of a DiffServ CodePoint (DSCP) in each packet’s IP header. Depending on the actual queuing and forwarding implementation, there are three types of PHB, namely BE, EF (Expedited Forwarding) and AF (Assured Forwarding). The EF class, typically DSCP value 46, minimizes delay and jitter and provides the highest level of aggregate QoS. The AF class assigns preset Dropping Probability (DP) to different DiffServ class traffic to provide relative services.

Bandwidth management deals with provisioning and regulating bandwidth usage in a manner that provides consistent performance and availability for all traffic applications. Generally, bandwidth management obtains best performance when it integrates four functions, namely Class Based Queuing (CBQ), TCP rate shaping, packet-size optimization and an algorithm for fair allocation of bandwidth by connection, i.e. within the same class, each connection has

a fair allocation of bandwidth [9]. Allocating specific amounts of bandwidth to a particular class of traffic guarantees that mission-critical applications never starve from lack of bandwidth availability. Consequently, bandwidth management produces an optimized mix of traffic to ensure that critical applications perform at their best at all times and bandwidth is used most efficiently.

The current generation of RGs provides insufficient QoS for meeting the demands of existing and emerging multimedia applications [13]-[14] and likewise provides insufficient bandwidth management [15] for optimum utilization of bounded network resources. To help solve these problems, this paper proposes a QRG (QoS-aware Residential Gateway)

with real-time traffic monitoring, DiffServ-QoS (Differentiated Services-QoS) and CBQ bandwidth

management in order to initiate DiffServ-QoS bandwidth management during network congestion. Firstly, ORG assigns traffic flow to the appropriate class for optimized treatment for user demands. Applications with higher priority of traffic get the right to deliver first. Additionally, the QRG built-in Traffic Control (TC) function adopts CBQ for QoS bandwidth/traffic management to optimize utilization of the bounded network bandwidth resource. CBQ provides fine granularity of bandwidth sharing and traffic priority control, including session level, to enable service level guarantees for individual flows and aggregate traffic.

Networked communication is increasingly important. It is changing our way of communication, work and entertainment. To remain competitive, businesses are shifting more and more to the Internet. E-crimes such as password hacking, account theft and false charging of purchases are making Internet security issues a major concern. Spam, worms, viruses, e-scams, e-vandalism and innovative hacking are new issues. Covert hijacking of computers as spam routers is one example. Another example is the massive February 2000 Distributed Denial-of-Service (DDoS) attacks which disabled high-profile Internet websites such as Yahoo, Ebay and CNN, or the January 2001 DDoS attack on Microsoft’s name server. Despite the well-known attacks on large high-visibility sites, the majority of attacks are not well publicized. It is clear that strengthening network security and defending against network attacks are primary issues in further development of Internet community.

The rest of this paper is organized as follows. Section II covers the proposed QRG system architecture. Section III introduces the proposed DiffServ-QoS and bandwidth management mechanism. QRG implementation and experimental results are presented in sections IV and V, respectively. Finally conclusions and future work are summarized in section VI.

II. QRGSYSTEM ARCHITECTURE

A typical application of the QRG system is presented in Fig. 1. As seen, the QRG interconnects the Internet and a home network that includes an IEEE 1394 HAVi network [8] and an X-10 home automation network [16].

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IEEE Transactions on Consumer Electronics, Vol. 51, No. 3, AUGUST 2005 842

Fig. 1. QRG network architecture

The IEEE 1394 system is a very fast external bus standard which supports an isochronous mode to transfer A/V data among devices, delivering data at a guaranteed rate. IEEE 1394 is ideal for devices such as video that need to transfer high levels of data in real-time.

X-10 was the beginning of affordable Home Automation and utilizes a “no-new-wires” solution by using existing power lines for communication. With plug-in X-10 power modules, for example, most devices plugged into a wall outlet can be remotely commanded to go "ON" or "OFF" without the addition expensive proprietary control wiring.

Fig. 2. QRG features

A. Features

QRG has the following features, as shown in Fig. 2: z User interface friendly

For communications from outside home, QRG provides server capability and user interface to meet the diversity of user interface environments.

z QoS/Firewall Function

The main purpose of the firewall is approximately the same as that of an office environment, i.e. to protect the system from unauthorized traffic. In addition, during network congestion, the QRG packet-filtering firewall intercepts and analyzes the packets, then modifies the headers according to the preset DiffServ-QoS rules shown in Tables I and II.

z Address translation and protocol translation functions

Generally there are differences between network protocols for inside and outside the home. In other words, protocol translation in needed between IP and

the (non-IP based) home network protocol, between IP private address (inside home) and the IP global address (outside home). The QRG hides the differences among them, making them transparent to users.

z Remote control function

A remote user (home user while on work or on vacation) while surfing on the QRG home page can remotely control the home network easily by GUI (Graphical User Interface).

z Auto-configuration function

Adopting preset settings, QRG with auto-configuration capability is convenient even for the elderly and children.

z Media translation function

Network capabilities such as bandwidth can differ significantly between the home network and the public or access network. Therefore, appropriate translation functions are needed (e.g. MPEG2/MPEG4 or DV/MPEG4 translation).

B. Bandwidth Management –Traffic Classification

Applications with very different characteristics and network requirements compete for bounded network resources. Often, the result is that critical transactional applications suffer unacceptable levels of performance degradation during network congestion.

However, bandwidth management enables users to allocate less bandwidth to HTTP traffic without sacrificing response time or throughput. Allocating less bandwidth to HTTP traffic frees up network resources for transactional applications and critical real-time traffic, thereby providing dramatic improvement in response time and throughput for critical data.

Before bandwidth allocation can be performed, QRG must identify the traffic that is traveling through it. This process is called Traffic Classification. In the following, the proposed QRG classifies the traffic into (but not limited to) 8 classes.

z Security traffic

This class includes security CCD/cameras which normally work when the user is outside the home. This class occurs periodically and frequently. Hence a relatively small bandwidth but high priority channel should be reserved for this class.

z Multimedia traffic

This traffic of application includes digital TV streaming, VoIP (Voice over Internet Protocol) applications, teleconferencing and other multimedia traffic. This class requires large bandwidth, small delay and delay jitter. High priority should be given to this class and the bandwidth should be reserved when the application is running.

z Home appliance control traffic

This class belongs to control signals for home appliance. These are normally small and short messages. These signals appear at user request. This class is assigned with high priority but with no bandwidth reservation

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IEEE Transactions on Consumer Electronics, Vol. 51, No. 3, AUGUST 2005 848

Experiments 2 and 3 to compare the ARM920T embedded system with the general-purpose PC. As shown in Figs. 13 and 14, performance using the ARM920T embedded system is slightly weaker than the general-purpose PC. Nevertheless, the general results of these experiments demonstrate that whether implemented in a general-purpose PC or in a modular low-power ARM920T embedded system, the proposed QRG successfully performs DiffServ-QoS and CBQ bandwidth management functions so that good quality of service and video performance are maintained during network congestion.

VI. CONCLUSIONS AND FUTURE WORK

Broadband networks and ubiquitous computing are driving development toward home networks built around some all-in-one digital home server. A trend is observed that regardless of how much bandwidth is available, new applications will be created to consume it. This paper has proposed a QoS-aware Residential Gateway (QRG) with real-time traffic monitoring and a QoS mechanism in order to initiate DiffServ-QoS bandwidth management during network congestion. Firstly, ORG classifies traffic flow to an appropriate class for optimized treatment for meeting user demands. Higher priority of traffic applications get the right to deliver first. Additionally, the QRG built-in traffic control function adopts CBQ for DiffServ-QoS bandwidth/traffic management to optimize utilization of bounded network bandwidth resources. CBQ provides fine granularity of bandwidth sharing and traffic priority control, including session level, enabling service level guarantees for individual flows and aggregate traffic. Network usage can be controlled and monitored even in large networks with thousands of users without severe performance degradation. Experimental implementations, not only in a general-purpose PC but also in a special-purpose modular low-power ARM920T embedded system, demonstrated the proposed QRG performs DiffServ-QoS well with CBQ bandwidth management mechanism on a Linux platform, thereby meeting the key goals of a cost-effective, low-maintenance, upgradeable, control and network gateway.

Our future work will add network security features to QRG such as IP traceback and watermarking. The eventual goal, of course, is a small, light-weight, portable, cost-effective, multimedia-capable and security-enabled product suitable for functioning as the (Q)RG of the modern digital home network.

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Wen-Shyang Hwang received B.S., M.S., and Ph.D. degrees in Electrical Engineering from National Cheng Kung University, Taiwan, in 1984, 1990 and 1996, respectively. He is an associate professor of Electrical Engineering, National Kaohsiung University of Applied Sciences, Taiwan. His current research interests include storage area networks, WDM networks, wireless networks, embedded systems, performance evaluation, Internet QoS, and Internet applications. He is a member of IEEE.

Pei-Chen Tseng was born in Hualien, Taiwan, in 1968. She graduated from National Taipei Institute of Technology in Electronic Engineering in 1990. From 1990 to 2001 she worked for Siemens as a telecommunication engineer, including five years as a testing engineer in EWSD switching systems, one year as a technical support engineer in switching systems, one year as a technical specialist in mobile telecommunication systems, and almost five years as a RF engineer in mobile telecommunication systems. Studying at the National Kaohsiung University of Applied Sciences, Kaohsiung, Taiwan, she received a B.S. in electrical engineering in 2002, a M.S. in 2004 and is currently pursuing a Ph.D. with a focus on communication, protocol and networking. Her research interests include home networking, network security, and GSM/GPRS/CDMA telecommunication systems. Ms. Tseng is a student member of IEEE.