VoIP Network Performance Evaluation of Operating Systems with IPv4 and IPv6 Network Implementations
Shaneel Narayan, Matthew Gordon, Chad Branks and Li Fan Department of Computing Unitec Institute of Technology Auckland, New Zealand
[email protected] Abstract— VoIP implementations are nowadays the preferred information technology alternative to public switched telephone networks. With dependence on this technology, VoIP quality and performance are critical. In this paper, we implement some commonly used VoIP CODECs on Windows desktop operating systems to evaluate their performance on two versions on IP, namely IPv4 and IPv6. Performance related metrics like throughput, jitter and latency are empirically measured in all combinations of operating systems with various CODECs and IP versions. A test-bed setup is employed to measure performance related metrics. Results obtained show that there is only a slight difference in performance between TCP IPv4 and IPv6 networks, however VoIP throughput, jitter and latency values are significantly different depending on the choice of CODEC, operating system and the IP version.
results show voice CODEC types give different performance metrics values depending on operating system and IP version. The rest of the paper is organized as follows: Section II describes Voice over IP CODECs, similar work undertaken by other researchers is mentioned in Section III, and Section IV outlines the experimental setup used in this research. We present the results and discuss the findings in Section V. Finally, the research is concluded in Section VI. II.
VoIP, also commonly known by descriptors such as IP telephony and broadband phone uses TCP/IP networks to establish voice communication between devices. Since voice is analogue and the TCP/IP media is digital, CODEC is used to compress analog voice signal to digitally encoded version that can travel on computer networks. Sound quality, bandwidth required, and resource requirements all depends on the choice of CODEC. G.7xx, including G.711, G.721, G.722, G.726, G.727, G.728, G.729, is a suite of International Telecommunications Union (ITU) standards for audio compression and de-compression. We now discuss a few commonly used voice CODECs. • G.711 – this is a high bit rate (64Kbps) of the ITU standard and is commonly the native language of the digital telephone networks. Formalized in 1998, it employs an 8-bit uncompressed logarithmic Pulse Code Modulation (PCM) encoding scheme with a sample rate of 8000 samples per second, allowing bandwidths up to 4MHz. Since G711 does not use compression, it gives good quality voice (may sound just like using a regular phone). Theoretically this CODEC will have comparatively low latency, however requires higher processing power. • G.721 –was introduced in 1984 and uses Adaptive Differential Pulse Code Modulation and produces lower bit rate the G711 (32Kbps). The reconstructed speech is almost as good as that produced by 64 Kbits/s PCM CODECs. • G.723 – is an extension of G.721 and was de-signed for video conferencing and telephony over standard phone lines. G.723 is optimized for real-time coding and offers acceptable voice quality. On fast processors, it offers simultaneous encoding and decoding in the software. Not well suited for sound and music effects and offers lower
Keywords- VoIP, IPv4, IPv6, performance evaluation, Windows operating system, CODEC, operating systems
I.
BACKGROUND
INTRODUCTION
Information Technology continue to rigorously enhance all aspects of personal, business and social activities in the twenty-first century living. Times are changing, technology is changing, and so do the demands and the expectations of millions of global users. Undoubtedly, the Internet is playing a vital role by providing a global information superhighway unrivalled by any other technological advancement. Internet Protocol (IP) version 4 currently forms the Internet cloud and has numerous limitations – this eventually will be replaced with version 6. The new version addresses inherent problems in the earlier version, and it offers new opportunities that can enhance communication experiences of users beyond current scope. However, IPv6 has larger data overhead than its counterpart, which hints network performance issues. In this paper, we performance analyze two commonly used Windows desktop operating systems, implemented with different versions of Internet Protocol, for three different voice CODEC types. The empirical experiments are conducted on a test-bed, and performance related metrics like throughput, delay, latency and jitter are measured. Our
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quality output than other CODECs with comparable data rates. • G.729 – compresses payload to low bit rate of 8Kbps using conjugate-structure algebraic-code-excited linear-prediction (CS-ACELP). A commonly used CODEC nowadays and offers comparatively low delay, high quality, robust speech performance at the price of complexity. It requires 10ms input frames and generates frames of 80 bits in length. The above mentioned VoIP CODECs are not a comprehensive list. They all have associated pros and cons and their performance variation on operating systems is researched in this paper. In the next section, we outline the literature search. III.
we evaluate performance of VoIP by measuring performance related metrics on two Windows desktop operating systems for both IPv4 and IPv6 networks. This is done on a test-bed of computers, discussed next. IV.
EXPERIMENTAL SETUP
Two computers with similar hardware (CPU: Intel Pentium C2D, RAM: 2GB, NIC: PCI Intel Pro 100, Hard Drive: Seagate 160GB) were connected using a cross-over cable and each of the operating systems to be tested were installed one at a time on this test-bed (Figure 1). IPv4 as the
LITERATTURE REVIEW
VoIP is well researched, and here we present a summary of a few key papers relevant to this research under-taking. In [1], VoIP performance on IPv4 and IPv6 networks are compared using soft phones on operating systems and bare PC. The authors conclude that difference in VoIP performance is negligible between the versions of IP. VoIP on wireless network has been looked at in [2], and impact of delay on VoIP is explored. It is suggested that techniques like packet scheduling can double VoIP capacity. Performance of VoIP on IEEE802.11a wireless network is researched in [3] and [4] impact of retransmissions and channel estimation errors on VoIP performance is discussed. With IEEE802.11b, VoIP performance is evaluated in [5] and [6]. In both papers VoIP performance is experimentally evaluated on wireless network and found that significant delays and transmission impairments can be incurred by VoIP packets which can lead to a poor quality of service (QoS) for users. A similar research undertaking in [7] has shown that VoIP capacity measured in simulations and testbeds can given similar results, provided limitation in the two methods are addressed appropriately. Increasing VoIP capacity on wireless LAN, by changing CODEC, is researched in [8] and [9]. Using buffering to enhance transmission on a mobile IPv6 network has been experimentally evaluated in [10]. Wired to wireless VoIP performance with transport layer protocols have been experimentally evaluated in [11]. On wired networks, relationship between IP performance and VoIP quality is explored in [12] showing that it may be possible to effectively manage QoS of VoIP by monitoring the corresponding network performances. In [13] and [12], speech quality in VoIP and methods to improve it has been experimentally evaluated. Enhancing VoIP by fine-tuning its multiple attributes or improving by enhancing protocols has also been researched. Packetization effects on VoIP performance and enhancing bandwidth has been simulated in [14]. Concepts surrounding VoIP application performance in discussed in detail in [15]. In [16], [17], [18] and [19], VoIP performance on satellite communication links and its intricacies has been researched. In it observed none of the above research has evaluated VoIP performance on implication of changing commonly used operating systems. The novelty of this research is that
Figure 1: Test-bed setup
communication protocol was configured first and data was collected. Later this was replaced with IPv6 ensuring that all other test-bed parameters remained the same. The first operating system tested was Windows Vista Business followed by Windows 7. D-ITG 2.6.1d [20] was the primary tool employed to evaluate performance of protocols on operating systems. This tool was chosen because it works with both the protocol versions and the operating systems. DITG generates traffic at application and network/transport layers, and sends it from sender to generator node and can measure performance related metrics. In this research application layer VoIP traffic is generated using different CODECs, and performance metrics like throughput, delay, latency and jitter for TCP traffic was measured. To ensure high data accuracy, all tests were executed 20 times, and to get the maximum throughput for a given packet size, each run had duration of 30 seconds. The results are presented and discussed next. V. RESULTS AND DISCUSSION TCP throughput values for both the operating systems implemented with the two versions of the Internet protocols
Graph 1: Throughput of all operating systems
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Graph 5: CODEC VoIP Delay
Graph 2: Throughput Windows Vista
clearly gives throughput values slightly higher that IPv6 for all packet sizes at least 128Bytes. The difference varies from approximately 6% for smaller packets to almost 2% for packets above 640Bytes. Windows 7 throughput values are shown separately in Graph 3. Like Windows Vista Business, IPv4 is again a slight better performer than IPv6. However, the difference is at a maximum 2%. Operating systems with the various CODECs on both versions of IP graphs are presented next. In Graph 4, throughput values for ten versions of CODEC are shown. Here it is seen that highest throughput values are achieved by CODEC G.711 irrespective of the operating system or the version of IP. This CODEC throughput averages approximately 650Kbps while that of G.723 and G.729 are almost 90% lower, averaging around 100Kbps. Except for IPv4 with G.711.11 and G.711.12, in all other scenarios, both operating systems have similar throughput values. In both the just mentioned scenarios, Windows 7 values are approximately 15% greater than Windows Vista Business. The delay experienced by CODEC implementations show interesting trends, as shown in Graph 5. In all scenarios except one, delay values are less than 0.003 seconds.
Graph 3: Throughput Windows Vista
are shown in Graph 1. Here it is seen that both Windows Vista Business and 7 follow similar pattern for both versions of the IP. Initially throughput value is low (approximately 40Mbps) for packet size 64Bytes and than rapidly increases for all other packet sizes to a throughput value averaging around 85Mbps. In Graph 2, only Windows Vista Business results are extracted and presented. It is seen that IPv4
Graph 4: CODEC VoIP Throughput
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Graph 6: CODEC VoIP Jitter
However or Windows 7 IPv6 with CODEC G.729.3, the experienced is comparatively high (0.014 seconds). In most scenarios, the difference between the two versions of IP is almost negligible. Jitter values are presented in Graph 6. All values are under 0.012 seconds and it is seen that for each CODEC type there is a clear distinction between the two operating systems – difference ranging from 25% to 90%. For all Windows Vista Business scenarios, IPv4 jitter values are significantly higher than IPv6. Opposite trend is seen for all Windows 7 implementation, where IPv4 values are always lower than IPv6. VI.
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CONCLUSIONS
In this research, performance of various VoIP CODECs was empirically measured on two Windows desktop operating systems (Windows 7 and Vista Business) with both versions of the Internet Protocol. From this empirical test-bed evaluation, the following specific conclusions are drawn: • Throughput values are almost the same for both the operating systems with both versions of the Internet Protocol. In all cases, IPv4 values are marginally higher by 2% -6% over IPv6 values. • CODEC G.711 values are significantly higher (almost by 90%) than that of other CODEC types for both operating systems with both versions of IP. • Windows 7 IPv6 with CODEC G.729.3 delay is significantly higher than all other CODECs in all scenarios. • There is significant variation in jitter values (25%90%) between Windows 7 and Windows Vista operating systems. This research has shown that the performance of VoIP CODEC depends on the operating system that it has been implemented on and IP version. The extent to which performance related metrics values differ depends on the combination of IP version, CODEC type and the implemented operating system. The research team aims to extend this study to incorporate more operating systems including server environments.
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