Upstream Throughput Research Articles

EMPIRICAL OBSERVATION OF WIRELESS NETWORK PERFORMANCE FOR TRANSMISSION CONTROL PROTOCOL (TCP) UPSTREAM AND DOWNSTREAM FOR DIFFERENT USERS SCENARIOS

The increase in demand for proper and fast access to network infrastructure around the University environment by staff, students, and visitors in the quest to carry out daily tasks or keeping up with trends/innovations around the globe is a daily experience resulting in some challenges. But these challenges are not unexpected. The access to network infrastructure around the environment encourages proper development. This paper presents an empirical observation of transmission control protocol upstream throughput (TCPupT) and downstream throughput (TCPdownT) performance for an IEEE 802.11g wireless local area network (WLAN) installed at a corridor space of University of Nigeria, Nsukka campus. This work measured the TCP upstream and downstream throughput values for single, double, and multiple users (several Users) accessing an installed WLAN access point. The paper adopted basic WLAN system setup approach while observing the TCP performance in relation to SNR. Data collected for each environment were statistically analyzed, equations and results were also presented. The observed TCP throughput values vary as users increase thereby affecting the observed round-trip time (RTT). The generated equations were also used to predict TCP throughput which would aid network engineers in the deployment of IEEE 802.11g WLAN systems especially around the university environment. It is now clear that the generated model equations can be used for predicting the expected performance of IEEE 802.11g WLAN systems during deployment. This work gives WLAN engineers, researchers and users an apparatus to rapidly estimate the TCP upstream and downstream throughput, by monitoring the received SNR for IEEE 802.11g systems.

Environment specific TCP upstream throughput models in IEEE802.11b WLAN

This paper presents our study on environment based dependence of TCP Upstream Throughput (TCPupT) on signal to noise ratio (SNR) for a single user in an IEEE 802.11b Wireless Local Area Network (WLAN). Small offices, open corridors and free space environments were studied using an infrastructure based network for different quality of service (QoS) traffic. Environment based Models that predict TCPupT directly from SNR for different signal categories were statistically generated, validated and compared with similar models that were earlier developed without considering specific environments. The first type of models developed in this work were developed from all data specifically collected from each environment while the second type of models were developed by first categorizing the data in each specific environment into different signal categories and then models were statistically generated for each signal category before combining them into one model equation. At the stated levels of significance and the different degrees of freedom, the developed models were accepted at 1% (for F test) and 0.5% (for T test). From the RMS errors computed, the specific environment based models developed in this work were more accurate (as they showed lower RMS errors compared with earlier similar models) in predicting TCPupT in IEEE 802.11b WLAN for a single user on the network. It was also observed that the second type of models were found to be more accurate having shown lower RMS errors.Keywords: TCP Upstream throughput, Signal to noise ratio, environment based empirical model,IEEE802.11b, WLANs

Towards estimating the untapped potential: a global malicious DDoS mean capacity estimate

ABSTRACTWhat is the malicious reflected distributed denial of service (rDDoS) mean potential of the internet? The authors have been using data from the openNTP project which measures the number of reflectors on the internet since 2014 until now, and completed a graph that roughly estimates a lower boundary for global rDDoS mean potential across four internet protocols (IPs); SSDP, NTP, SNMP and open recursive DNS. By summing these values, and adjusting for average uplink capacity from reflectors, we come to a single number: 108.49 Tb/s as an estimate of rDDoS magnitude potential across IPv4. Tracking this number over time can give us insights into global remediation and clean-up efforts and where to invest our resources in when battling of rDDoS attacks. This paper demonstrates that the upstream throughput is the main contributing, measurable limiting factor for a volumetric rDDoS attack. The largest DDoS event reported by a single target (Dyn in 2016) was 1.2 Tb/s. In contrast, our lower estimate for the global attack potential is two orders of magnitude larger than the Dyn attack.The key contribution is an extensible methodology for measuring global potential for rDDoS attacks, with surprising policy implications.

Hitless λ-Tuning Sequence to Reduce Tuning Delay in λ-Tunable WDM/TDM-PON

In wavelength (λ)-tunable wavelength-division-multiplexing/time-division-multiplexing passive optical networks (WDM/TDM-PONs), an optical line terminal (OLT) directs optical network units (ONUs) to change wavelengths to achieve functions such as load balancing or power saving. This demands λ-tuning without any data-frame loss, i.e., hitless λ-tuning. In addition, there is a need to increase the dynamic bandwidth allocation cycle period (DBA-p) to expand scalability as regards the splitting ratio or fiber reach. Unfortunately, with a large DBA-p, more buffer memory is needed in the OLTs or ONUs to cover the tuning delay demanded by the conventional hitless λ-tuning sequence, which requires a message exchange between the OLT and the ONU after λ-tuning. In this paper, we propose a novel hitless λ-tuning sequence to reduce the tuning delay. With the proposed sequence, the completion of λ-tuning is decided by calculation, and the buffers for upstream and downstream transmissions are released according to the calculation, instead of the message exchange. Experiments confirm that the proposed sequence can tune the wavelength of the ONU's transceiver without any data-frame losses for multiple measurements. Each measurement includes 300 λ-tuning operations. Additionally, it is shown that, when the DBA cycle is 4 ms, the tuning delay and buffer memory for upstream transmission can be reduced by 98% and 50%, respectively, while those for downstream transmission can be reduced by 86% and 86%, respectively, compared to the conventional sequence. We also show that the maximum upstream throughput is not degraded.

Measurement and modelling of TCP downstream throughput dependence on SNR in an IEEE802.11b WLAN system

This paper presents our study on the dependence of TCP downstream throughput (TCPdownT) on signal to noise ratio (SNR) for multiple users in an IEEE 802.11b Wireless Local Area Network (WLAN) system. The study was carried out in small offices, open corridors and free space environments using an infrastructure based IEEE 802.11b WLAN while transmitting different quality of service (QoS) traffic all corresponding to different wireless multimedia tags. Models describing TCPdownT against SNR for different signal categories were statistically generated and validated. Our findings show a large variation in the throughput behaviour of the IEEE 802.11b WLAN system for the different categories of signals. We observed RMS errors of 0.938012Mbps, 1.047012Mbps, 0.65833Mbps and 0.452927Mbps for the general (all SNR) model, strong signals model, grey signals model and weak signals model respectively which were much lower than that of similar models with which they were compared. Comparing our results with a previous work on TCP upstream throughput showed that it is more accurate to investigate upstream and downstream throughput separately. Our models enable network designers and installers to predict the TCPdownT without the need to measure additional parameters other than the observed SNR which is already part of the normal network installation process.

Analysis of Modulation Order to Guarantee Real-Time Service Throughputs in OFDMA-PON

In an orthogonal frequency-division multiple access passive optical network (OFDMA-PON), each optical network unit (ONU) chooses a modulation format based on the signal-to-noise ratio (SNR) at its receiver. An ONU with a high SNR can use a high-order modulation format to increase its transmission efficiency. When upstream resources are fully utilized, this increases an aggregated upstream throughput by ONUs, but the throughput is varied by ONUs' modulation orders. To guarantee upstream throughputs of real-time services, we first estimate the network throughout in a case that a total upstream resource is fully and fairly distributed to ONUs. By using the estimation, then, we present the lowest order of available modulation formats for the throughput guarantee. We investigate how the modulation order affects the number of ONUs that can be serviced in the OFDMA-PON.

Investigation on the Dependence of TCP Upstream Throughput on Snr for Single and Multiple Links in a Wlan System

An empirical investigation on the dependence of TCP upstream throughput (TCPupT) against signal to noise ratio (SNR) in an IEEE802.11b WLAN system was carried out in various environments and varieties of QoS traffic using an Infrastructure based IEEE802.11b WLAN system set up consecutively in various environments (open corridor, small offices with block walls or plaster boards and free space). Empirical models describing the TCPupT against SNR for different signal ranges (all signals, strong signals, grey signals and weak signals) were developed and validated for both single and multiple users on the network. Our results show a strong dependence of TCPupT on the received SNR which varied as the SNR values changed from high (strong signals) through low (grey signals) to very low (weak signals). Our models showed lower RMS errors when they and other similar models were compared with validation data. We observed RMS errors of 0.5605471Mbps, 0.4479389Mbps, 1.04536603Mbps and 0.5813471Mbps for the General, Strong signals, Grey signals and Weak signals models respectively for the single user scenario. We also observed RMS errors of 1.3319396Mbps, 0.9457431Mbps, 0.8092979Mbps and 0.4220292Mbps for the multiple users scenario. An appreciable difference was observed between the throughput behavior for single and multiple users on the network showing the inefficiency of the distributed coordination function and Point coordination function used in WLANs as access mechanisms. Our models will provide researchers and WLAN systems users with a tool to estimate the TCP upstream throughput in a real network in various environments by monitoring the SNR.

A Novel OFDMA-PON Architecture With Source-Free ONUs for Next-Generation Optical Access Networks

This letter proposes a novel architecture for next-generation passive optical networks based on the employment of orthogonal frequency-division multiple access. The key new feature of the proposed approach is source-free single-wavelength upstream transmission enabled by carrier suppression, which has been experimentally verified to achieve 10-Gb/s upstream throughput.

Dynamic bandwidth assignment MAC protocol for differentiated services over GPON

A dynamic bandwidth assignment MAC protocol is proposed to facilitate the upstream channel resource sharing and to support differentiated services over GPON. A new procedure for bandwidth reporting and a novel balance transferring mechanism are incorporated together with efficient bandwidth assignment. Simulated upstream throughput characteristics demonstrate significantly improved network performance.

Analysis and modeling of upstream throughput in multihop packet CDMA cellular networks

We consider the problem of throughput modeling of wireless multihop packet CDMA networks with cellular overlay using simple forwarding strategies in the upstream. Considering the effect of shadowing and distance-dependent path loss, we approximate the probability density of interference at each base station (BS) and compare numerical and simulation results for different path-loss parameters. We derive the probability density of the received power at each BS due to transmission of one packet from a random node, as well as the probability distribution of the number of packets received at each node per time slot. Subsequently, we use the above results to approximate the probability density of the total received power at each BS based on calculations of moments. We observe that the probability density of intercell interference due to transmissions from terminals and routers may be approximated by normal and log-normal densities, respectively. We quantify the network performance based on throughput, total consumed power, and outage probability for different system parameters. For homogeneous link efficiencies, introducing routers into the network while reducing the transmission power increases the mean and variance of interference to the desired signal, hence higher outage probability. However, there are ample opportunities inherent to multihop structure, applicable to any of the physical, data link, and network layers, which help increase the overall achievable network throughput.

Performance characterisation of the MCNS DOCSIS 1.0 CATV protocol with prioritised first come first served scheduling

The Multimedia Cable Networks Systems (MCNS) Data Over Cable Service Interface Specifications (DOCSIS) is established as the primary cable network data communications standard. The head-end scheduling algorithm is not defined within the standard but it is the key function for providing the required performance capability. Computer simulation, using the Common Simulation Framework (CSF) 12 version of the CableLabs DOCSIS 1.0 computer model, has been used to predict the upstream system throughput and mean access delay. A prioritised first come first served scheduling algorithm has been considered to provide a baseline reference set of performance statistics against which other algorithms can be compared. The simulations, with theoretical confirmation, have shown that the maximum sustainable system throughput is 1965 kbps for a channel capacity of 2560 kbps and a packet size of 1500 octets, whereas for packet size of 100 octets the maximum sustainable throughput is only 1550 kbps. The mean access delay is found to vary between 10-900 ms depending on the offered load and assuming that the offered load does not exceed the capacity of the channel. Excess offered load causes service starvation according to the assigned priority.