Keep-alive Messages Research Articles

An improved mechanism for flow rule installation in-band SDN

Abstract Software Defined Network (SDN) is a new network architecture that controls the network through a logically centralized controller. The controller computes and installs the flow rules (i.e., entries) in the flow table at switches. When a switch receives the data packet and does not have the flow rule in its flow table, the switch contacts controller. The best path is computed by using topology and network policies. Then controller installs flow rules at switches along the path. Subsequently, the packet is forwarded to the switches accordingly. Due to the asynchronous nature of SDN, the packet may reach an intermediate switch before the corresponding flow rules. In this case, the packet is dropped by the switch. To address this problem, we propose a new technique that computes delay of both, the flow rules installation and packet arrival at a switch along the path. In case the packet arrival delay at the switch S1 is less than the delay of corresponding flow rule installation at S1, then the packet is delayed for a minimum duration at the predecessor switch of S1 in such a way that the corresponding flow rule is installed before the packet arrival. Thus, the proposed mechanism ensures flow rule installation before the corresponding packet reaches switches and subsequently reduces packet loss. To compute the delay between any two switches, and a switch and controller, our proposed technique exploits the keep-alive messages exchanged between switch and controller in order to reduce the redundant traffic in the network. We evaluated our proposed technique in terms of packet delivery ratio and average packet end-to-end delay in Mininet emulator. Our proposed technique improves the packet delivery ratio up to 36% and average packet end-to-end delay is reduced to 74% in case of a varying number of flows as compared to an existing mechanism. Moreover, we testify our proposed technique by running the real network traces.

Evaluating a Dynamic Keep-Alive Messaging Strategy for Mobile Pervasive Systems

Abstract: Timely loss-of-contact detection between devices in pervasive systems using mobile networks is an important aspect for both functionality and user experience. Traditional schemes where time-to-live is defined by the service provider are not adequate in mobile networks where communication failures are frequent. On the other hand, schemes using keep-alive messaging tend to increase the communication overhead, in particular if the time to detect a loss of contact needs to be short. We introduce a strategy where the time between keep-alive messages is adjusted dynamically according to the need in a particular application. Our solution was evaluated with usage data from a professional application built on the PalCom framework. The measurements show a 96 % decrease of the communication overhead while still maintaining the same system responsiveness.

Impact of mobile instant messaging applications on signaling load and UE energy consumption

Mobile Instant Messaging (MIM) applications transmit not only user-triggered messages (UTMs), but also keep-alive messages (KAMs) via radio access network, which induces heavy burden in control plane channel and wastes user equipment (UE) energy consumption. In this paper, we deduce the joint distribution of KAM period and UTM mean interval from the MIM application traffic characteristics. Correlating the joint distribution with radio resource control (RRC) state machine in LTE networks, we derive two analytical expressions for the control plane signaling load and UE energy consumption respectively. Then, the variation of signaling load and energy usage is demonstrated with different settings of RRC release timer, KAM period and UTM mean interval. The analysis indicates that KAM period is the upper bound of RRC release timer when reducing the signaling load. Besides, five times of UTM mean interval is the upper bound of KAM period when reducing the UE energy consumption and signaling load. These results can guide both network operators and MIM application developers to properly set control parameters for balancing the signaling load and UE energy consumption.

Experimental Assessment of Power-Save Behavior of Commercial IEEE 802.16 Network

The mobility and portability of next-generation cellular devices must address limited accessibility to power; hence, power-saving techniques of mobile terminals are crucial. In this paper, we provide a comprehensive measurement study of power-save mechanisms implemented in current IEEE 802.16 (WiMAX) deployed networks. Particularly, we examine the power consumption of the various transmission and reception modes and compare them with the power consumption during Idle and Sleep modes. We show, both experimentally and analytically, that although theoretically, power consumption can be dramatically reduced by employing an efficient algorithm that alternates between power-save and active modes, lack of cross-layer coordination prevents efficient power-save implementation. We suggest and implement a simple proactive buffering solution that delays the sporadic traffic generated by the upper layers such as keep-alive messages, when the device is in Idle mode and show that such an enhancement can dramatically reduce the device's power consumption. In this paper, we discuss a strategy, termed Intra Frame Power-Save (IFPS), which, although not standardized by 802.16, is implemented by some leading vendors. IFPS does not require any cross-layer coordination, yet can dramatically reduce power consumption even while the device is in operational mode. We suggest ways for further reducing power consumption while performing the schedule by the base station utilizing the IFPS mechanism.

Supporting Distance Vector Routing Over Device Discovery Flows in the Pervasive Middleware PalCom

PalCom is a pervasive middleware that enables users to combine services from different devices into assemblies, or usage scenarios. The mechanism of device discovery in PalCom builds an ad-hoc network of interconnected devices while replacing cross-network periodic keep-alive messages with timely forwarded events that notify devices about the discovery and undiscovery of each other. Moreover, the device discovery mechanism is decoupled from any specific routing decisions mechanism. In this paper, we present a design that builds on this flexibility to add distance vector routing to PalCom while inheriting the event based cross-network device discovery for updating routing tables on interacting devices. The proposed design has been implemented and evaluated against a network with links that continuously change their availability.

Device Discovery for the PalCom Pervasive Middleware with Eliminated Cross-networks Periodic Heart-beat Messages

Service discovery is central in pervasive middleware systems, built on top of the communication substrate using the more fundamental mechanisms for device discovery. In mobile pervasive systems devices come and go, and switch network frequently, demanding support for device discovery across heterogeneous networks. We present the design of a device discovery mechanism for the PalCom middleware that eliminates the need for cross-network periodic keep-alive messages while still supporting timely detection of missing devices, i.e. undiscovery. The design has been implemented and is evaluated against the simplistic approach of flooding the inter-connected networks with keep-alive messages.

Still Alive: Extending Keep-Alive Intervals in P2P Overlay Networks

Detecting node failures within Peer-to-Peer networks is an inherent trade-off between timely detection and consuming bandwidth on network maintenance. In the absence of user-driven messages, the majority of P2P networks rely upon the exchange of periodic keep-alive messages to maintain connections and network topology. We investigate three novel algorithms which prioritise keep-alive messages to nodes that are more likely to have failed. In doing so, these algorithms significantly reduce the expected delay between failures occurring and their subsequent detection in comparison to the standard approach, whilst consuming similar levels of bandwidth. Our algorithms build upon several studies that have shown that older peers are more likely to remain in the network than their short-lived counterparts. Each of our algorithms increase the interval between successive keep-alive messages as peers age in the system, based upon the distribution of peer session times and the current age of peers. We extensively describe the details of each algorithm, before comparing them to the standard periodic approach using simulations based upon measured network data. Furthermore, we show that these algorithms are complimentary to existing gossip-based mechanisms and investigate alternate methods of ascertaining a node’s age so that our algorithms can be robustly deployed in untrustworthy environments.

OBGP+: An improved path-vector protocol for multi-domain optical networks

One of the essential components for the dynamic provisioning of lightpaths across multiple domains is the Routing and Wavelength Assignment (RWA) strategy adopted. The consolidation that path-vector protocols have had in practice, has motivated the optical extension to BGP (OBGP). We claim, however, that a routing model mostly centered on the exchange of reachability information–like the one we have today with BGP or the one offered by OBGP–will not be sufficient for multi-domain optical networks. Routing domains must be able to exchange both reachability as well as aggregated Path-State Information (PSI). Understanding that this is a missing piece in the routing models provided by BGP and OBGP is easy nowadays, but contributing with solutions capable of highly improving the performance of a path-vector without impacting on key aspects of the protocol–fundamentally, its scalability, its convergence properties, and the number of routing messages exchanged between domains–is a challenging task. In this paper we propose OBGP +, which is a very simple extension of a path-vector protocol supporting the computation and advertisement of PSI between optical domains. The PSI that we propose to use is highly condensed in the form of a single integer value. In order to avoid the typical increase in the number of routing messages associated with the update of PSI, we propose to piggy-back the updates in non-dummy Keepalive messages exchanged between OBGP+ neighbors. Extensive simulations reveal that, despite its simplicity: (i) OBGP+ is able to drastically reduce the blocking experienced with a path-vector protocol like OBGP; (ii) OBGP+ needs much less number of routing messages than OBGP to achieve such performance; and (iii) the convergence and restoration features of OBGP+ are also better than those of OBGP, which is particularly important for connections that lack a protection path.

A Novel Algorithm for Fast Detection of Network Failure

Fast failure detection is critical to traffic protection/restoration in a high-speed network. Generally, the way to detect failures is to periodically exchange keep-alive messages by layer 3 protocols. In traditional protocols like Open Shortest Path First (OSPF), the failure detection time is about tens of seconds, which makes the protection/restoration time too long to keep up with the increasing quality-of-service (QoS) demand. Although configuring the related parameters in OSPF can reduce the detection time to the order of milliseconds, it introduces notable issues of scalability and instability to the network. In this paper, a novel algorithm called “Low Priority Hello Reduction” (LPHR) is proposed to achieve faster failure detection while maintaining high network stability. This algorithm reduces the Hello messages sent when the signaling network is congested and maintains the adjacency by other messages. We compare it with previous schemes and our experimental results show that the algorithm we propose is superior in about an order of magnitude in reduction of both false failure alarms and queuing delay of other messages, especially at a light network load.