1,720,967 research outputs found
'Energy efficient ethernet' enhanced with a QoS-aware sleep mode controller
No full textOperating costs and scalability of nowadays telecommunication networks are largely impacted by energy consumption of network equipments. In packet switching devices it is especially due to packet processing, queuing, and input/output interface functionalities. Different approaches to reduce energy consumption in packet switches are emerging, some exploit under-laid optical bypass of transit traffic to reduce their capacity and interfaces, others simplify their operations or turn off some of their functionalities when unnecessary. The IEEE standardization body developed a standard on Energy Efficient Ethernet (IEEE P802.3az) that defined a mechanism allowing to de-activate the Physical layer elements during periods of low link utilization. It is based on a protocol that coordinates transitions to and from a lower power consumption mode without changing the link status and dropping frames. Time needed by such transitions is, however, comparable with packet transmission time; that makes energy efficiency of the method far from being proportional to interfaces unused capacity. Solutions proposed in the literature to improve EEE performance are mainly based on the buffer and burst approach, which, making the transmission non continuous, creates more opportunities for long sleeping period. Such solutions, however, if applied across the network, strongly impact packet delay requirements. In this paper, a traffic management mechanism that controls sleeping period to reduce EEE transitions overhead while meeting delay constraints of data flows is proposed. Starting from the consideration that in Ethernet network provisioning is static, i.e. service level agreement parameters of each flow are configured on switches output ports of its path via management plane at the set-up phase, the proposed method off-line determines, for each output port, if the activation of a dummy flow, associated to the quiet period, can provide power consumption reduction without impacting data flows delay requirements. On ports where the dummy flow is activated the sleeping period is triggered by the scheduler mechanism each time a dummy packet is served. A comparative analysis between the standard EEE, with and without the support of buffer and burst functionality, and the proposed method has been carried out in order to quantify the improvements in terms of energy efficiency and to assess its effectiveness in terms of Quality of Service (QoS). © 2011/2012 IOS Press and the authors
Switching node with load balancing of bursts of packets
No full textA packet switching node is coupled by links to other nodes of a network, and receives and assembles packets belonging to a specified packet flow, into bursts of packets with a burst control packet indicating a sequence of the burst in the flow. The node determines whether to distribute the flow across several links. If so, the bursts are then forwarded for switching to the output ports of the selected links. Distributing the flow over multiple links can enable more flexible and efficient filling of allocated bandwidth on links, as traffic increases. To reduce the risk of losing the order of packets the sequence of the bursts is indicated for use in reordering at intermediate nodes during transmission through the networ
Packet forwarding node
No full textA packet forwarding node of a transport network performs a first packet forwarding mode in which received packets are processed and forwarded on a per-packet basis. The forwarding node performs a second packet forwarding mode when the node identifies a group of consecutive packets. The group of packets are destined for the same destination node of the transport network. The second packet forwarding mode comprises determining a forwarding treatment for the group of packets and forwarding the group of packets with the determined treatment. The forwarding is performed without processing the headers of at least some of the packets in the group. The group of consecutive packets is identified by a control packet preceding the group or by inter-packet signalling which indicates that the packet before the inter-packet signalling and the packet after the inter-packet signalling are to be treated as part of the same group. Packets which are determined to be received on transit channels can be forwarded without processing headers of individual packets
Dimensioning of optical codes in OCDM/WDM optical packet switches
No full textIn this paper we investigate the performance of an Optical Code Division Multiplexing/Wavelength Division Multiplexing (WDM/OCDM) Optical Packet Switch when impairment due to both Multiple Access Interference and Beat noise are taken into account. Analytical models are introduced to dimension the switch resources, in particular the number of optical codes carried on each wavelength. The Packet Loss Probability due to output packet contentions is evaluated as a function of the main switch and traffic parameters when Gold coherent optical codes are adopted. The Packet Loss Probability of the OCDM/WDM switch can reach 10 -9 when M=16 wavelengths, Gold code of length L=511 and only 24 wavelength converters are used in the switch. © 2012 ACADEMY PUBLISHER
QoS-aware sleep mode controller in 'Energy Efficient Ethernet'
No full textEnergy efficiency in telecommunication networks has been recognized as a very important topic during the last few years. This is motivated by the fact that reduction of power consumption translates into reduction of carbon footprint and operating costs. The IEEE standardization body also included energy consumption aspects into its activities and developed a standard on Energy Efficient Ethernet (IEEE P802.3az). Its objective was to define a mechanism to reduce power consumption of the Physical layer when links are underutilized. It therefore defined a protocol to coordinate transitions to and from a lower power consumption mode without changing the link status and dropping frames. Time required by such transitions is however comparable with packet transmission time; that makes power consumption reduction of the method strongly dependent on packet inter-arrival time and limits its application to cases of low link utilization, such as home/office environments and access networks. A new solution for extending the application of the EEE mechanism in Ethernet networks with different traffic load conditions and QoS requirements, where data flows are statically provisioned and opportunely conditioned at the edge, is proposed. It allows shaping traffic across the network so as to reduce O0/OFF transitions at EEE aware switch interfaces while ensuring end to end delay constraints to packets traversing multiple links. It off-line determines on the basis of the Parekh Gallager theorem if the activation of a dummy flow, associated to the OFF periods, can provide power consumption reduction without impacting data flows delay requirements. On ports where the dummy flow is activated, the scheduler mechanism triggers the OFF period each time a dummy packet is served. A performance analysis of the EEE mechanism enhanced with the proposed QoS aware sleep mode controller has been carried out in order to quantify the improvements in terms of energy efficiency with respect to the standard EEE operation and to assess its effectiveness in terms of Quality of Service (QoS). © 2012 IEEE
An Analytical Model Evaluating the Performance of Small Size Asynchronous Optical Packet Switches
No full textIn this paper we propose an analytical model able to analytically evaluate the performance of an asynchronous Optical Packet Switch (OPS) realized in Semiconductor Optical Amplifier (SOA). The considered switch has a bufferless architecture that shares the wavelength converters for input wavelength. The obtained results show how the proposed model is more accurate than others proposed in literature in the case of small size switches
Evaluation of the energy consumption per bit in BENES optical packet switch
No full textWe evaluate the average energy consumption per bit in Optical Packet Switches equipped with BENES switching fabric realized in Semiconductor Optical Amplifier (SOA) technology. We also study the impact that the Amplifier Spontaneous Emission (ASE) noise generated by a transmission system has on the power consumption of the BENES switches due to the gain saturation of the SOAs used to realize the switching fabric. As a matter of example for 32x32 switches supporting 64 wavelengths and offered traffic equal to 0,8, the average energy consumption per bit is 2, 34.10 -1 nJ/bit and increases if ASE noise introduced by the transmission systems is increased. © 2011 IEEE
Performance Evaluation of a QoS Technique for Bufferless Optical Packet Switches
No full textIn this paper we propose a technique to support Quality of Service for Bufferless Optical Packet Switches (OPS) equipped with shared Wavelength Converters (WC). The WCs sharing is fully, that is all of the arriving packets share the same pool of WCs. The QoS, expressed in terms of Packet Loss Probability, is differentiated by giving the packets different priorities in accessing both the output wavelengths and the WCs. The effectiveness of the QoS technique is studied by means of a sophisticated analytical model validated by simulation results. The results show that the proposed technique to support QoS allows a good differentiation of the QoS offered to the packets
Performance Evaluation of an Optical Packet Switch using Wavelength and Code domain to solve Output Contentions
No full textIn this paper we investigate the performance of an Optical Code Division Multiplexing/Wavelength Division Multiplexing (OCDM/WDM) Optical Packet Switch when impairment due to both Multiple Access Interference and Beat noise are taken into account. The Packet Loss Probability due to output packet contentions is evaluated as a function of the main switch and traffic parameters when Gold coherent optical codes are adopted. When the available bandwidth is fixed, due to a statistical multiplexing effect, we show that the use of more length codes and fewer wavelengths lead to lower packet loss probability, especially for low offered traffic
Evaluation of power consumption of spanke optical packet switch
No full textThe power consumption of an Optical Packet Switch equipped with SOA technology based Spanke switching fabric is evaluated. Sophisticated analytical models are introduced to evaluate the power consumption versus the offered traffic, the main switch parameters, and the used device characteristics. The impact of Amplifier Spontaneous Emission (ASE) noise generated by a transmission system on the power consumption is investigated. As a matter of example for 32 x 32 switches supporting 64 wavelengths and offered traffic equal to 0,8, the average energy consumption per bit is 5,07 . 10 -2 nJ/bit and increases if ASE noise introduced by the transmission systems is increased. © 2011 IEEE
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