DCNET 2018 Abstracts

Full Papers
Paper Nr: 5

TCP Congestion Control over IEEE 802.11 Wireless Lans based on K-Means Clustering Focusing on Congestion Window Size and Round-trip Time


Tomokazu Moriyama, Ryo Yamamoto, Satoshi Ohzahata and Toshihiko Kato

Abstract: Recent IEEE 802.11 wireless LANs provide high speed data transfer using the newly introduced physical and MAC technologies. Although packet losses over a wireless link are also decreased by the help of new MAC technologies, some packet losses still occur randomly. Those packet losses invoke TCP congestion control, which reduces the TCP level throughput, even if congestion does not occur at al. In order to resolve this problem, some machine learning based approaches have been proposed, which use K-means clustering in order to discriminate congestion triggered packet losses and wireless error triggered packet losses. However, those proposals use only delay related parameters, but delay may increase due to non-congestion reasons, in which case the conventional proposals fail discrimination. This paper proposes a method to classify packet losses by the K-means clustering focusing on congestion window size and round-trip delay, and to stop decreasing congestion window when losses are triggered by wireless errors. We develop the proposed method as a Linux kernel module and show the performance evaluation results that the throughput increases by 40% without increasing unnecessary packet losses.

Paper Nr: 12

Virtual Network Function Embedding in Multi-hop Wireless Networks


Zahra Jahedi and Thomas Kunz

Abstract: The use of Network Function Virtualization (NFV) and Software Defined Network (SDN) provides opportunities to offer services with lower CAPEX/OPEX for service providers and deploy new services quickly. However, it will introduce new challenges. One of the main challenges is an optimized placement of the virtualized functions based on the characteristics and available resources of the network. Placement of Network Functions (NFs) can affect the path traffic flows take and consequently bandwidth usage in the network. While most of the research is focused on the challenges of NFV in wired networks, it can also be applied to wireless networks. However, the specific differences between the wired and wireless networks should be considered. In this paper, we are expanding one of the comprehensive placement methods in the wired networks which use Integer Linear Programming (ILP) to place a chain of NFs. The extended model formulates the main characteristic of the wireless networks which is a scarcity of bandwidth due to interference. As our results show, the interference in the wireless networks increases the bandwidth usage and consequently the average NF deployment cost. To address this, we can either increase the number of nodes or the nodal resources to achieve higher placement success rates.

Paper Nr: 15

Multicasting in Tactical Networks: Forwarding Versus Network Coding


Ola Ashour, Marc St-Hilaire and Thomas Kunz

Abstract: Multicasting refers to the transmission of packets to a group of one or more destinations. It can be very useful in military applications, such as command and control, in which a commander needs to send instructions to a group of tanks, users, or planes. Broadcast is a unique case of multicast, where all the nodes in the network are intended receivers. The broadcast case has been studied quite extensively in the literature, showing that the use of Network Coding (NC) requires fewer data transmissions than Packet Forwarding (PF). That motivates us to explore whether the same result holds true when only a subset of nodes are receivers. In this paper, we developed two linear optimization models that determine lower bounds on the number of required data packet transmissions when sending data in a Mobile Ad-hoc Network (MANET) from a single source to multiple receivers. The first model determines the minimum number of required packet transmissions under the assumption that PF is used. The second model assumes that data is distributed using NC. We derive lower bounds for different scenarios while varying the network size, network density, and the number of receivers in the multicast group and compare them with each other. Results indicate that the lower bounds for both PF and NC are almost the same for smaller network sizes (30 nodes or less), small multicast group sizes (5 or lower), or dense networks. However, for larger network sizes, sparser networks, and larger multicast group sizes NC is more advantageous than PF.

Short Papers
Paper Nr: 6

OSPF Algebraic Formal Modelling using ACP - A Formal Description on OSPF Routing Protocol


Pedro Juan Roig, Salvador Alcaraz, Katja Gilly and Carlos Juiz

Abstract: OSPF may well be the most popular routing protocol within Autonomous Systems, being used in all kind of networks around the world. In this paper, we first design a basic model by focusing on the main tasks of a router running OSPF, hence being neighbour discovery and a simplified route management, by means of algebraic derivations using Algebra of Communicating Processes (ACP). Taking this model as a base case scenario, we extend it by adding up some timing behaviour present in real OSPF implementations and by detailing the packet exchanges involved in route management.

Paper Nr: 9

Segment Routing Single Link Failure Congestion Optimization


Vitor Pereira, Miguel Rocha and Pedro Sousa

Abstract: Segment routing is an implementation of the source routing paradigm built over an Interior Gateway Protocol. It allows improving Traffic Engineering in IP/MPLS networks by decomposing forwarding paths in lists of smaller paths called segments. The flexibility introduced by segment routing enables new responsive and dynamic methods to react to network fault events, such as link failures. Typical responses to single link failures only aim to reestablish loop-free connectivity between affected routers and do not account for impacts in network congestion. As Interior Gateway Protocols recompute shortest-paths after a link failure, SR paths and links utilization are affected by the fault augmenting the overall network congestion. This paper addresses this problem comparing post-convergence network congestion values obtained with industry and new proposal Evolutionary Computation based recovery path computation methods for segment routing. Furthermore, by comparing and analyzing each method’s advantages and disadvantages, we show that a multiplane optimization procedure stands out with best results.

Paper Nr: 8

VDES Performance Evaluation for Future e-navigation Services


M. Luglio, C. Roseti and F. Zampognaro

Abstract: E-navigation aims at increase safety and efficiency of navigation, defining reliable data exchange formats and communication channels between either ship to ship or ship to shore. New technological advancements start from the consolidation of Automatic Identification System (AIS), which is mandatory in some classes of ships for the notification of the position and to send distress signals. In pair with AIS baseline services, additional services are gaining momentum and are available in state of the art equipment, including the handling of sending and receiving Application-Specific Messages (ASMs). In this direction, the VHF Data Exchange System (VDES) standard was recently introduced, to improve on both messaging capabilities and system flexibility (standardizing the use of satellite channels) as well as to allow higher bitrates for application messages with regard to AIS and ASM. In this paper, we reviewed the main characteristics of VDES, then we carried out a technical analysis of the new communication standard in terms of channel compositions, supported rates, access schemes and latency. Finally, we focus on the performance of two possible future VDES applications, namely “dematerialization” and “towage” through a MATLAB model of the VDES communication channels.