new wireless TCP algorithm in real environments, in order to identify the advantages ... In out-door environments with WiFi technology, we performed a traffic ...
Performance Evaluation of a New Wireless TCP Algorithm in Out-door and In-door Environments on WiFi and WiMAX links Román Lara-Cueva, Member, IEEE, Gonzalo Olmedo, and Katherine Calvopiña. Abstract—This article describes the performance evaluation of a new wireless TCP algorithm in real environments, in order to identify the advantages and disadvantages of its operation. We evaluate the proposed wireless TCP algorithm with respect to generic TCP, considering an intrusive technique by using traffic injection. These tests were performed over point-to-point WiFi and WiMAX links in out-door and in-door environments. The proposed amendment for wireless TCP was incorporated in a virtual machine under Linux operating system, and using D-ITG tool for the traffic injections. We assess the performance of the proposed algorithm in terms of the main parameters of Quality of Service (QoS) as throughput, delay, and jitter. Our primary results demonstrate that our new proposal of the TCP algorithm presents better results in comparison with the generic TCP referred to all terms of QoS in wireless environments. Index Terms——Wireless TCP, throughput, delay, jitter, performance evaluation.
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I. INTRODUCTION
RANSPORT Control Protocol (TCP) was created to establish a connection-oriented communication, ensuring transmission between interconnected networks, multiplexes the data from the different sources from which they come for transiting on the network simultaneously [1]. TCP guarantees that data is delivered to its destination without error [2], and handles certain algorithms for congestion control data, adapting both the delay and the bandwidth of the network. As we known, TCP is one of fundamental Internet protocols designed to be used with high reliability in host-to-host switching network connections of communication software packages and interconnected systems [3]. However, TCP was designed for solving the own problems of wire networks, these solutions are ineffective for wireless networks, for example packet losses occur in wireless networks usually for two main reasons, the first are the errors caused due to the physical medium, which is related to the bit error rate (BER), this problem causes a reduction of the bit rate, which means reducing their performance, and the second is the network Manuscript received July 29, 2015; accepted August 17, 2015. Date of publication October 28, 2015; date of current version September 9, 2015. This work was supported in part by the Universidad de las Fuerzas Armadas ESPE, Sangolquí, Ecuador, through the Economical Support in the Development of this Project by Research under Grant Project 2011-PIT-010. R. Lara-Cueva, G. Olmedo, and K. Calvopiña are with the Grupo de Investigación en Sistemas Inteligentes (WiCOM-Energy) and Centro de Investigaciones de Redes Ad Hoc, Departamento de Eléctrica y Electrónica, Universidad de las Fuerzas Armadas ESPE, Sangolquí-171-5-231B, Ecuador (e-mail: {ralara, gfolmedo, kcalvopiña}@espe.edu.ec).
congestion, the main problem in wire networks. In this setting, we developed a new TCP algorithm that solves the first problem, which refers to the characteristics of the medium [4]. In this paper we evaluated our proposal TCP algorithm, which was developed in our previous works and detailed in [5][6], and tested in real environments. We verified how TCP can adapt optimally running over WiFi and WiMAX links, by using negative acknowledgments, and optimize the congestion control mechanism to manage this common problem in wireless networks, in order to identify the main advantages and disadvantages considering an intrusive technique by injecting traffic with D-ITG tool [1], in real environments with network topologies that use WiFi and WiMAX technologies, to test its performance at various distances within our university campus at ESPE. We used a test scenario with a network model consisting of an access point and two wireless clients, configure one of these nodes to generate traffic and thus check the network performance at different distances. In out-door environments with WiFi technology, we performed a traffic network model consists of an access point, and two or more wireless clients. In out-door environments with WiMAX technology, we test a scenario consists of the Base Station (BS), a Relay Station (RS), and two Subscribers Stations (SS); we made injections of traffic in different directions testing behavior network. The rest of the paper is organized as follows. Section II summarizes previous works on the subject. Section III describes the test scenarios in which we perform injections traffic. Section IV describes the results obtained in our scenarios. Finally, Section V presents our conclusions and future works. II. RELATED WORK TCP in wireless means with priority should manage congestion, the same which is more common in this environment [7], that of random packet losses due to congestion that in a significant number of packets lost. In the implementation of the original TCP [8], flow control windows are used to control the use of space in the receiver buffer and retransmission after a fall for reliable packet delivery, but there is no dynamic adjustment of window flow control in response to congestion, so the performance decreases for wireless links. There are some proposals of algorithms that aim to provide the performance of TCP over wireless links, and then briefly describe some of them. The Snoop protocol module introduces a snoop agent at the BS, and compare
stored data segments and ACKs exchanged with mobile stations, determining which segments are lost in the wireless link and a local broadcast schedule at link layer. Explicit Loss Notification (ELN) [9] seeks to optimize TCP on mobile transmitters because it informs the TCP sender that a loss due to wireless link errors occurred by the ELN bit, so it is excluded from the congestion control retransmissions from the transmitter. ELN make a list of the voids produced in sequence space, to avoid confusing a gap caused by congestion at the BS with a gap caused by a wireless loss, the agent on the BS queries the list of holes and marks the ELN bit in the ACK, when the transmitter warns you have received an ACK with the ELN bit scores, retransmits the lost segment and updates a variable called, eln_last_RXmit. Delayed Duplicate Acknowledgments (DDA) [10] thinking about a future broadcast, DDA slows the third duplicate ACK, assuming that this is a wireless loss, receiver free duplicate ACK in order to trigger a delayed relay end-to-end. Requires modifications to the mobile station and does not distinguish wireless loss and congestion loss. Explicit Congestion Notification (ECN) [11] reported an incipient congestion rather than drop packets using an two-bit field in the IP header called ECN, and consists of two flags known as ECT and CE. When both ends of the transport protocol are "ECN-capable" this is indicated by the codes '10 'and '01' are identified as "ECN-Capable Transport" (ECT) ECT (0) and ECT (1) respectively. The code '00 '("Not-ECT") is a package that is not using ECN and finally the code '11' is used by routers to indicate both ends of the connection that is experiencing an incipient congestion. It is estimated that the disposal should not need a "full ECN-capable" network but still exist in the transition to it. Congestion Coherence (CC) [12] considered presupposition that ECN is implemented on the wired network; CC uses a scheme based on congestion coherence between consecutive packets pointing to determine the cause of the loss of packets. Local retransmissions employs link layer level and detects packet loss cause. All frames transmitted in the wireless link are recognized locally before being cleared in the buffer of the issuer. Frames that are not recognized or are negatively acknowledged after the expiry of a timer will be retransmitted. III. TEST SCENARIOS The scenarios used for testing have real unlike the scenario which was used in [5] conditions, it was an emulator link, in which factors such as attenuation, distortion, noise and interference were controlled, among others, used the kernel with corresponding to the new algorithm of TCP, using a virtual machine with Linux operating system distribution UBUNTU, transmissions were performed using the traffic injection D-ITG, by setting the number of packets per second, the size of the send segments and accordingly, the corresponding bandwidth, we use OWD (One Way Delay). The values set for the frame size is based on the fact that TCP as protocol transmitted as frames based on 512 bytes, the MSS (maximum segment size) for TCP is set to 1024 bytes, and Ethernet transmits usually frames 1500 bytes is therefore
TABLE I VALUES FOR TRAFFIC INJECTION Frame Bit Rate Number of Test Size (kbps) Packages/s (bytes) 1 2500 512 11880 2 2500 512 6624 3 1500 1024 12768 4 1000 1500 12320
intended to make a comparison in the case of a wired communication and thus to observe the behavior and performance of the new algorithm during transmission. The tests were conducted at different distances, WiFi technology for out-door were four distances, in-door 2 WiFi and WiMAX distances out-door, 6 distances. Table I summarizes all the values, which were considered in our test scenarios. A. Scenario out-door test with WiFi technology The network scenario consisted of two terminals, with the implementation of TCP modified in the virtual machine with the modified kernel, the terminals are connected by wireless link to an AP (Access Point) out-door (PowerStation2, Ubiquiti), provided the conditions for supporting evidence, the terminals were located at different distances within the campus, obtaining results with D-ITG, which allows us to control the number of packets sent per second and the size in bytes of the same, as depicted in Figure 1. B. Stage in-door test with WiFi technology This scenario consisted of two terminals or computers connected by wireless link to an AP (Access Point) under WiFi technology. Conducted by injecting D-ITG traffic in both the transmitter and the receiver. The software configuration and the scenario was the same used in the tests out-door, Figure 1 shows the scenario in-door, with the main difference of the distances considered between stations. C. Out-door venue for testing WiMAX Figure 2 shows the scenario with WiMAX technology, the tests were performed using a network model consisting of a Base Station (BS) ARBA550 Albentia Systems and several user terminals (CPE) or Underwriters Stations (SS), one of these nodes is configured to generate traffic and the other to receive and check the performance of the network at different distances greater than 100 meters. A computer linked to the CPE Base Station makes the transmissions; therefore it has a mixed connection because the computer has a wired Ethernet connection to the CPE equipment, and WiMAX wireless link to the base and back to the destination.
Fig. 1. Stage Out-door testing.
Figure 3. Test 1 WiFi - Comparative Chart.
Figure 2. General structure of the out-door scenario testing WiMAX technology.
IV. ANALYSIS AND PERFORMANCE OF QOS From experimental tests results in terms of throughput, delay and jitter, in some cases, being experimental tests with various weather conditions, the values vary so the right way to handle these figures is getting the value obtained median between iterations of testing conducted in this way is left out outliers and values are within the generated trend taken. The data obtained from the experimental tests show variations depending on the distance, the technology used and the weather conditions or obstacles. To evaluate the performance of the new algorithm for use TCP parameters: Throughput, jitter and delay, so that the speed at which data is sent, the normal interference and of the delay is evaluated, TCP will compare TCP NACK+15 TCP NACK+20 with TCP Generic to conclude whether there are improvements in the performance of the algorithm for data exchange between the transmitter and receiver.
Figure 4. Test 2 WiFi - Comparative Chart.
A. Results of tests in terms of throughput WiFi For Test 1 TCP NACK+15 shows better performance at all distances, while TCP NACK+20 shorter distances greater than 180 meters, compared to this generic TCP, as depicted in Figure 3. Meanwhile, Figure 4 shows that for Test 2, TCP NACK +15 shows a trend toward better performance at all distances, while TCP NACK +20 shorter distances greater than 190 meters, compared to TCP generic. For Test 3, TCP NACK+15 shows a trend toward better performance at all distances, while TCP NACK +20 shorter distances greater than 220 meters, compared to generic TCP as we can see in Figure 5. Finally, for Test 4, TCP NACK +15 shows a trend toward better performance at all distances, while TCP NACK +20 shorter distances greater than 210 meters, compared to generic TCP, as depicted in Figure 6.
Figure 5. Test 3 WiFi - Comparative Chart.
Figure 6. WiFi Test 4 - Comparative Chart.
B. Results of tests with WiMAX in terms of throughput
Figure 7. Test 1 WiMAX - Comparative Chart.
Figure 7 shows the results for Test 1 in WiMAX scenario, both TCP NACK +15 and TCP NACK +20 show a trend toward better performance at distances less than 400 meters compared to generic TCP. For Test 2, TCP NACK +15 shows a trend of better performance at distances less than 410 meters, while TCP NACK +20 shows a low performance in distances less than 410 meters, compared to TCP generic, as depicted in Figure 8. Meanwhile, Figure 9, shows the results for Test 3, TCP NACK +15 and TCP NACK +20 shows a trend of better performance at distances less than 410 meters, just as TCP NACK +15 compared to generic TCP. Finally, in Figure 10, Test 4 TCP NACK+15 shows a trend of better performance at distances less than 410 meters, TCP NACK+20 shows better performance at all distances especially in the range from 410 to 800 meters compared to generic TCP is showed. C. Results of tests with WiFi as to delay
Figure 8. WiMAX Test 2 - Comparative Chart.
Figure 9. WiMAX Test 3 - Comparative Chart.
Figure 10 shows the results for Test 1, TCP NACK+15 and TCP NACK+20 show a decrease in the delay, which allows us to assert the best performance of the algorithm experienced in all distances, all in comparison with the generic TCP. For Test 2, TCP NACK+15 and TCP NACK+20 show a decrease in the delay, which allows us to assert the best performance of the algorithm experienced in all distances, in comparison with the generic TCP, as depicted in Figure 11. Meanwhile, in Figure 12 are the results for Test 3, as both TCP NACK +15 and TCP NACK +20 show a decrease in the delay, which allows us to assert the best performance of the algorithm experienced in all distances, in comparison with the generic TCP. Finally, for Test 4, TCP generic shows decrease in delay with respect to TCP NACK +15 and TCP NACK +20 which allows us to observe that under these conditions of transmission, sending 1000 packets per second 1500 bytes, the algorithm does not show an advantage over generic TCP, as depicted in Figure 13. D. Results of testing WiMAX in terms of delay Figures 15, 16, 17, and 18, show the results for WiMAX scenario, in all tests by comparing TCP NACK +15 and TCP NACK +20 show a decrease in the delay, we identified the best performance of the algorithm experienced in all distances, by comparing with the generic TCP. The TCP NACK +15 shows the better performance referred to the time delay up to 700 m respect to TCP NACK +20 for tests 3 and 4, as depicted in Figures 17 and 18.
Figure 10. WiMAX Test 4 - Comparative Chart.
Figure 11. WiFi Test 1 - Comparative Chart delay.
Figure 15. WiMAX Test 1 - Comparative Chart delay.
Figure 12. Test 2 WiFi - Comparative Chart delay.
Figure 16. WiMAX Test 2 - Comparative Chart delay.
Figure 13. WiFi Test 3 - Chart comparative delay.
Figure 17. WiMAX Test 3 - Chart comparative delay.
Figure 14. WiFi Test 4 - Chart comparative delay.
Figure 18. WiMAX Test 4 - Chart comparative delay.
V. DISCUSSION Consistent with the performance evaluation of wireless TCP modified algorithm, performed using experimental evidence regarding WiFi transmission link, in terms of throughput is observed that TCP NACK +15 and TCP NACK +20 will show an improving trend in tests at distances between 200 ± 20 meters with approximately 20% increase compared to generic TCP, thanks to the negative acknowledgment thereof which forwards the lost segments while maintaining the throughput with which you have found sending in that times. Regarding delay may indicate that TCP NACK+15 and TCP NACK+20, in test 2 and 3 stand out with an advantage of about 40% decrease at all tested distances. As for jitter, it became clear that TCP NACK+15 generally outperforms 150 and 230 meters away; TCP NACK +20 shows an improving trend at 100 and 150 meters. Regarding WiMAX transmissions with link, regarding TCP throughput and TCP NACK +15 and TCP NACK +20 at distances less than 414 meters profiting about 10%, and at a distance of 414 meters between the transmitter and receiver gains obtained up to 200% compared to the four generic TCP tests, which include TCP NACK +20 at distances greater than 414 meters in test 4, which was transmitted 1000 packets per second of 1500 bytes, earned a considerable profit, attributable to increased congestion window whenever negative ACKs are received due to loss, and to be more frequent ACKs is much greater increase in the congestion window. Regarding delay may indicate that TCP NACK +15 has better performance in all tests, experienced in all distances. Regarding NACK +15 TCP jitter performed better compared to generic TCP in Tests 1, 2 and 3, maintains a TCP NACK +20 slight tendency to decrease jitter 414 and 427 meters away. Generally under the WiFi technology in accordance with the results obtained in terms of throughput, delay and jitter can indicate that overall the best performance we have evidence TCP NACK +15 at distances of about 200 ± 20 meters. Under the WiMAX technology in general, the best performance in terms of throughput TCP NACK +15 presents at distances less than 414 meters. It may be concluded that the new algorithm of TCP outperforms conventional TCP, based on the results obtained, because the algorithm by showing a loss in the transmission sends a negative ACK for retransmission increasing the congestion window, thus achieving increased transmission speed. For future studies are recommended to test the algorithm under transmissions with specific applications that allow for practical purposes and use of their advantages to wireless telecommunications means low. REFERENCES [1] Jayananthan, A., “TCP performance enhancement over wireless networks”. University of Canterbury, New Zealand, 2007. [2] Seth, S. y Venkatesulu, M., “TCP/IP architecture, desing, and implementation in linux”. New Jersey: John Wiley & Sons, Inc., 2008. [3] A. Dainotti, A. Botta, A. Pescapè, “A tool for the generation of
realistic network workload for emerging networking scenarios,” in Computer Networks, 2012, vol. 56, no. 15, pp. 3531-3547. [4] Lara, R.; Simo, J., "Performance analysis of uplink capacity in IEEE 802.16j transparent mode," IEEE Colombian in Communications Conference (COLCOM), 2012, pp.1-6. [5] Pilo-Pais, A., “Verificación del desempeño de un nuevo algoritmo de control de congestionamiento en entornos inalámbricos reales mediante la modificación del protoco TCP en el kernel de Linux”. Escuela Politécnica del Ejército, 2011. [6] Cifuentes, G. F. O.; Almeida, C; Zelenovsky, R.; Camara, C. E.; Filho, R. B.; Arantes, D. S. “Controle de congestionamento do protocolo TCP em sistemas de comunicação sem fio CDMA usando estrategia de detecção multiusuario, arranjo de antenas e correção de erro FEC.” Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de Computação, 2002. [7] Fernández Hernández, M., “Desarrollo de alternativas al protocolo TCP para redes inalámbricas,” 2002. [8] RFC 793. “Transmision Control Protocol”. IETF. [9] Balakrishnan, H.; Katz, R., “Explicit Loss Notification and Wireless Web Performance,” in IEEE Globecom Internet Mini-Conference, 1998. [10] N. H. Vaidya, M. Mehta, C. Perkins, G.Montenegro, “Delayed duplicate acknowledgements: a TCP unaware approach to improve performance of TCP over wireless,” Technical Report 99-003, Computer Science Dept., Texas A&M University, 1999. [11] Ramakrishnan, K.; Floyd, S.; Black, D., “RFC 3168: The Addition of Explicit Congestion Notification (ECN) to IP”, 2001. [12] Chunlei, L; Raj, J, “Approaches of wireless TCP enhancement and a new proposal based on congestion coherence, “in Hawaii International Conference on System Sciences, Quality of Service in Mobile and Wireless Network minitrack, 2003.
