Mohammad Rajiullah

On the effectiveness of PR-SCTP in networks with competing traffic

PR-SCTP is an extension to SCTP for partial reliability that enables a content sensitive transport service where the reliability of messages can be individually controlled. In previous work, PR-SCTP has been applied for prioritization of messages and trading of reliability against timeliness for applications such as real time video streaming, IPTV transmission, SIP signaling, and syslog. As compared to TCP, it has been shown to provide significant reductions in message transfer delay and gains in application performance. Much of the previous work has, however, considered artificial loss scenarios without competing traffic. Experiments presented in this paper show that although PR-SCTP clearly outperforms TCP in artificial loss scenarios, the performance gain is not as evident in scenarios where PR-SCTP shares a bottleneck link with competing traffic. Our analysis shows that inefficiencies in the forward_tsn mechanism of PR-SCTP, overhead due to small messages, and a higher loss rate per byte encountered by PR-SCTP are contributing factors to the reduced performance when network resources are shared. Finally, a proposal for a more efficient forward_tsn mechanism is introduced.

Optimizing PR-SCTP performance using NR-SACKs

A partially reliable extension of SCTP, PR-SCTP, has been considered as a candidate for prioritizing content sensitive traffic at the transport layer. PR-SCTP offers a flexible QoS trade-off between timeliness and reliability. Several applications such as streaming multimedia, IPTV transmission, and SIP signaling have been shown to benefit from this. Our previous work, however, suggests that the performance gain can be very much reduced in a network with competing traffic. One of the most important factors in this case is the inefficiency in the forward_tsn mechanism in PR-SCTP. In this paper, we thoroughly examine the forward_tsn inefficiency and propose a solution to overcome it that takes advantage of the NR-SACKs mechanism available in FreeBSD. Moreover, we implement and evaluate the proposed solution. Our initial set of results show a significant performance gain for PR-SCTP with NR-SACKs. In some scenarios the average message transfer delay is reduced by more than 75%.

Priority Based Delivery of PR-SCTP Messages in a Syslog Context

Unquestionably, syslog provides the most popular and easily manageable computer system logging environment. In a computer network, syslog messages are used for several purposes such as for optimizing system performance, logging user’s actions and investigating malicious activities. Due to all these essential utilities, a competent transport service for syslog messages becomes important. Most of the current syslog implementations use either the unreliable UDP protocol or the more costly reliable TCP protocol. Neither of these protocols can provide both timeliness and reliability, while transporting inherently prioritized syslog messages in a congested network. In this paper, we both propose and evaluate the use of PR-SCTP, an existing partial reliability extension of the SCTP transport protocol, as a candidate transport service for the next generation syslog standard. In our emulation based experimental results, PR-SCTP shows better performance than TCP in terms of average delay for message transfer. Furthermore, PR-SCTP exhibits less average packet loss than UDP. In both cases, PR-SCTP exploits priority properties of syslog messages during loss recovery.

FLEX-MONROE: A Unified Platform for Experiments under Controlled and Operational LTE Settings

This paper presents FLEX-MONROE, a unique platform that facilitates achieving a thorough understanding of LTE networks, one that captures the status of current operational MBB networks and that also enables LTE performance improvements by allowing experimentation in an environment with controllable LTE parameters. Using this platform, we propose to investigate how variations in the LTE network parameters influence the network characteristics, which, in turn, translate to application performance metrics that represent the end-user experience. We argue that the FLEX-MONROE platform is crucial to understand, validate and ultimately improve how current operational MBB networks perform, towards providing guidelines for designing future 5G architectures. Furthermore, understanding the effects of low-level tweaks in network parameters in the LTE infrastructure on the application performance is critical to provide guidelines on how to improve the application performance in the current but also future MBB networks.

Results from running an experiment as a service platform for mobile broadband networks in Europe

Abstract In this article we present a selection from a vast range of experiments run with MONROE, our open experiment as a service (EaaS) platform for measurements and experimentation in Mobile Broadband Networks. We show that the platform can be used to benchmark network performance in a repeatable and controlled manner thanks to the collection of a rich set of geotagged metadata and the execution of discretionary user experiments. Indeed, with the sheer amount of data collected from 12 commercial mobile operators across Europe, MONROE offers an unprecedented opportunity to monitor, analyze and ultimately improve the status of current and future mobile broadband networks. Besides, we show how flexibly the platform allows combining metadata and experimental data series during the experiments or by means of post-processing, and show results produced by our own experiments as well as comment on results obtained by external research groups and developers that have been granted access to our platform.

Demo: Experimentation in Controlled and Operational LTE Settings with FLEX-MONROE

This demo paper presents FLEX-MONROE, a platform that facilitates better understanding of the status of current Mobile Broadband (MBB) networks (e.g. 3G and 4G/LTE) and enables performance improvements by allowing experimentation with controllable LTE parameters. The platform enables the investigation of the impact of low-level tweaks in network parameters in the LTE infrastructure on the application performance. We argue that FLEX-MONROE is crucial to provide guidelines on how to improve the application performance both in the current and future MBB networks.

Performance analysis and improvement of PR-SCTP for small messages

PR-SCTP, a partially reliable extension of SCTP, provides a flexible QoS trade-off between timeliness and reliability for application traffic. However, the performance of PR-SCTP can be affected by certain traffic characteristics and network scenarios. We previously proposed an NR-SACK based optimization for PR-SCTP. In this work, we extensively evaluate and analyze the performance of PR-SCTP with NR-SACKs using different network scenarios. Moreover, we compare the performance of our NR-SACK based PR-SCTP with existing transport protocols for syslog traffic. In the evaluation, we use real syslog traces from an operational syslog system. The results indicate that NR-SACK based PR-SCTP significantly improves the overall message transfer delay as compared to SCTP and TCP.

Syslog performance: Data modeling and transport

Syslog is one of the basic methods for event logging in computer networks. Log messages that are generated by syslog can be used for a number of purposes, including optimizing system performance, system auditing, and investigating malicious activities in a computer network. Considering all these attractive uses, both timeliness and reliability is needed when syslog messages are transported over a network. The unreliable transport protocol UDP was specified in the original syslog specification; later a reliable transport service based on TCP was also proposed. However, TCP is a costly alternative in terms of delay. In our previous work, we introduced the partially reliable extension of SCTP, PR-SCTP, as a transport service for syslog, trading reliability against timeliness by prioritizing syslog messages. In this work, we first model syslog data using real syslog traces from an operational network. The model is then used as input in the performance evaluation of PR-SCTP. In the experiments, real congestion is introduced in the network by running several competing flows. Although PR-SCTP clearly outperformed TCP and SCTP in our previous work, our present evaluations show that PR-SCTP performance is largely influenced by the syslog data size characteristics.