1,720,973 research outputs found
Cost Evaluation of Packet Switches equipped with Limited-Range and Full-Range Converters for Contention Resolution
No full textTwo architectures are proposed for a wavelength-division multiplexed optical packet switch equipped with both limited-range wavelength converters (LRWCs) and shared full-range wavelength converters (FRWCs). The FRWCs are used to overcome the performance degradation in terms of packet loss probability due to the use of LRWCs only. Two different sharing strategies of the FRWCs are considered. In the first architecture, a pool of FRWCs is shared among the arriving packets. In the second one, the sharing is only partial and the packets directed to the same output share a same pool of FRWCs. A probabilistic model is proposed to dimension the number of shared FRWCs so that the same packet loss probability of a switch equipped with only shared FRWCs is guaranteed. After introducing a cost model of the converters depending on the conversion range, we show that the architectures may allow a conversion cost savings on the order of 90%
Switching Node with Load Balancing Bursts of Packets
No full textA packet switching node is coupled by links to other nodes of a network, and receives and assembles (74) 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 (78) whether to distribute the flow across several links. If so, the bursts are then forwarded (80) for switching to the output ports (160) 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 network
Cost Evaluation of Optical Packet Switches Using Both Limited-Range and Full-Range Converters for Contention Resolution
No full textAn architecture is proposed for a wavelength division multiplexed (WDM) optical packet switch equipped with both limited range wavelength converters (LRWCs) and shared full range wavelength converters (FRWCs). The FRWCs are used to overcome the performance degradation in terms of packet loss probability due to the use of LRWCs only. A probabilistic model is proposed to dimension the number of shared FRWCs so that the same packet loss probability of a switch equipped with only shared FRWCs is guaranteed. After introducing a cost model of the converters depending on the range conversion, we show that the architecture may allow conversion cost saving in the order of 85%
Shared per Wavelength Optical Packet Switch Dimensioning by a Classical Occupancy Problem Solution
No full textWe propose a new kind of Optical Packet Switch (OPS) architecture that allows an easier realization than classical shared per node (SPN) architectures introducing a new sharing per wavelength strategy and found for this an upper bound for the Packet Loss Probability
Packet Forwarding Nodes
No full textA packet forwarding node (20) of a transport network (10) performs a first packet forwarding mode in which received packets (51) are processed and forwarded on a per-packet basis. The forwarding node performs a second packet forwarding mode when the node identifies a group (50) of consecutive packets (51). The group of packets are destined for the same destination node of the transport network (10). The second packet forwarding mode comprises determining a forwarding treatment for the group of packets (51) and forwarding the group of packets with the determined treatment. The forwarding is performed without processing the headers (52) of at least some of the packets in the group. The group (50) of consecutive packets (51) is identified by a control packet (60) preceding the group (50) or by inter-packet signalling (53) 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
Performance evaluation of the OCDM/WDM technique for optical packet switches
No full textThe performance of the Optical Code Division Multiplexing/ Wavelength Division Multiplexing (WDM/OCDM) technique for Optical Packet Switch is investigated. The impact on the performance of the impairment due to both Multiple Access Interference and Beat noise is studied. 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
Routing and Wavelength Assignment OTDM/WDM Networks with Physical Impairments
No full textIn this paper we evaluate the impact that physical impairments have on the resource
consumption in Wavelength Division Multiplexing (WDM) networks where bandwidth
utilization is optimized performing an Optical Time Division Multiplexing (OTDM). In
particular we propose two modified heuristics to solve the problem of Routing and
Wavelength Assignment (RWA) in OTDM/WDM networks where physical impairments
are taken into account. In literature this RWA problem is referred to as S-RWA (Super-
Lightpath RWA) because Super-Lightpath must be routed. If D is the OTDM
multiplexing degree, a Super-Lightpath is able to carry all connections from a single
source node to D different destinations using the D time-slot carried out on each
wavelength. The effectiveness of the technique is evaluated on the COST 266 physical
topology and when random logical topologies with several connectivity degrees are
considered. The RWA problem under physical impairments has been solved versus D
and . The resource consumption is characterized by the average number n of
wavelengths used and the number nSL of Super-Lightpath routed. When a heuristic
optimizing the number of links occupied for each Super-Lightpath is used, we have
obtained for D==16 (n, nSL)=(24.3, 26) and (n, nSL)=(18.9, 145) when an S-RWA
problem with and without physical impairments is solved respectively. The increase in
number of Super-Lightpath was expected because the routing with physical
impairments leads to shorter Super-Lightpath so much more of them are needed to
solve S-RWA problem. On the contrary the lower number of wavelengths is explained
with a better distribution of the Super-Lightpaths on physical topology when physical
impairments are taken into account. In fact when they are not considered, Super-
Lightpaths are longer, it is more probable that two Super-Lightpaths have at least one
link in common and so a greater number of wavelengths are needed
An Analytical Model to Optimally Dimension Resources in OPS Equipped with Heterogeneous Wavelength Converters
No full textAn optical packet switch that shares both limited range and full range wavelength converters for contention resolution is proposed with the aim to guarantee an high conversion cost saving. To optimally dimension the number and the conversion range of the wavelength converters, an analytical model, validated by simulation, is introduced to evaluate the packet loss probability of the switch. Numerical results show that the proposed switch architecture allows for a conversion cost saving in the order of 90% with respect to a classical architecture in which only shared full range wavelength converters are used
Performance Evaluation of an Optical Packet Switch equipped with FRWCs and LRWCs Shared per Output Fiber
No full textAn optical packet switch that shares wavelength converters for contention resolution is introduced. The sharing is partial and both limited and full range wavelength converters are used in the pool of converters shared in each Output Fiber. A parallel scheduling algorithm is defined to manage the optical packet forwarding and the wavelength converters. Performance are evaluated by means of an accurate analytical model validated through simulation
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