Shuo Li et al.  demonstrated that the overflow priority classification approximation (OPCA) was an accurate method for blocking probability evaluation for various networks and systems, including OBS (Opticalburst switched networks) with deflection routing. OPCA was a hierarchical algorithm that requires fixed- point iterations in each layer of its hierarchy. This was implied along running time and also proved that the OPCA iterations alternately produced upper and lower bounds that consistently become closer to each other as more fixed-point iterations in each layer are used. It had been observed that the speed of the bounds moving closer decreases when the proportion of the overflowed traffic increase due to the growth of the offered load or the maximum allowable number of deflections, as well as the reduction of the number of channel per trunk and also demonstrated in the case of NSFNET with 50 channels per trunk that the OPCA is faster and at least as accurate as the EFPA.
circuit and packet switching while overcoming their limitations. In opticalburstswitching, the term burst is a variable length data packet, assembled at an edge router by aggregating a number of IP packets, which may be received from a single host or from multiple hosts belonging to the same or different access networks. A burst has two components: control and payload. The control packet carries the header information. Thus, the control component incurs an overhead, referred to as control overhead. Payload is the actual data transmitted. Control packet is sent first followed by the payload on a separate wavelength channel after an offset time equal to the processing time of control packet at intermediate node. Control packet is processed electronically at each intermediate node and reserves resources for a period starting from the time the payload/data burst is expected to arrive at the node until the transmission is completed.
NP-SFMOC-VF algorithm through simulation. For simulation proposed and to be more précised we take three cases for channel scheduling. In each case we take three bursts B1, B2 and B3 which have to be scheduled by using different algorithms. W is the maximum number of outgoing data channels. According to given input data of table I , we obtained an output as Table 1 which is shown below. Considering a Table 2 and its cases I, II and III we can see that in Case I delay is more in our proposed algorithm as compare to NP-DFMOC-VF and NP-SFMOC-VF but in Case II delay is less in our proposed algorithm than NP-DFMOC- VF and NP-SFMOC-VF where as in Case III in our proposed algorithm delay is more for data burst B1 and less for data burst B2 and B3 as compare to NP-DFMOC VF and NP- SFMOC-VF. Hence we can say that delay does not depend on type of algorithm we used but it depends on how the data bursts are schedule on the channels. Also from simulation of Figure 8-10 this can be seen. Again considering table 2, this time we consider total packet loss for different algorithms versus number of channel used for different algorithms. According to table we simulate the result for this as shown in Figure 11, 12 and 13. We can see that packet loss for our proposed algorithm is zero for case I and II and in case III packet losses are very low and number of channel used is also less comparing to NPSFMOC-VF algorithm. In NPDFMOC- VF algorithm, though the number of channel used is less than NPSFMOC-VF and our proposed algorithm but the packet losses are very high in NPDFMOC-VF then NPSFMOC-VF
One of the major concerns in the field of computer Network is how to Transfer large amount of data and Transfer that data without any congestion or faults. OpticalBurstSwitchingnetworks are used today for the huge transfer of data. So, Fault Tolerance is an important Issue in the Opticalburstswitching network. Fault tolerant refers to the ability of the network to transfer the information at the same amount as if any type of fault occurs in the network. In any network there are number of path to reach from source to the destination so, first the calculation of shortest path must be required. Blocking probability is the parameter which is used for the calculation of the possibility of the particular path to be blocked. In the traffic engineering Engset formula is used for the calculation of the blocking probability in the network there are the finite population sources. This paper includes the designing of new algorithm for fault tolerant and comparison of Algorithm with already existed algorithms. This algorithm is based on the shortest path calculation, checking of the fault on the each path, Calculation of blocking on paths which are fault free then selects the path with the minimum blocking probability.
OBS is considered as an optical network technique that allows wavelength-division multi- plexing (DWDM) and in this regard, the method of Volterra series transfer function (VSTF) is presented that state characteristic coefficients to record intersymbol interference (ISI), self phase modulation (SPM), intrachannel cross phase modulation (IXPM), intrachannel four wave mixing (IFWM), cross phase modulation (XPM) and four wave mixing (FWM), to clas- sify the influence of these components on the system output . Furthermore, a discrete-time input-output model is introduced for single channel multipulse multispan fiber-optic commu- nications systems based on the VSTF method. This model created an agrement with SSF method and its use has been shown by new coding scheme to prevent the development of intra- channel interferences .
The opticalburstswitching (OBS) paradigm is perceived as an intermediate switching technology prior to the realization of an all-optical network. Burst assembly is the first process that takes place at the edge of an OBS network. It is crucial to the performance of an OBS network because it greatly influences loss and delay on such networks. Burst assembly is an important process while burst loss ratio (BLR) and delay are important issues in OBS. In this paper, an intelligent burst assembly algorithm called a Fuzzy-based Adaptive Length Burst Assembly (FALBA) algorithm that is based on fuzzy logic and tuning of fuzzy logic parameters is proposed for OBS network. FALBA was evaluated against itself and the fuzzy adaptive threshold (FAT) burst assembly algorithm using 12 configurations via simulation. The 12 configurations were derived from three rule sets (denoted 0,1,2), two defuzzification techniques (Centroid [C]and Largest of Maximum[L]) and two aggregation methods (Max[M] and Sum[S]) of fuzzy logic. Simulation results have shown that FALBA 0LM has
A Passive Optical Network is a single, shared optical fiber that uses inexpensive optical splitters to divide the single fiber into separate strands feeding individual subscribers. OpticalNetworks are called “passive” because other than at the CO and subscriber endpoints, there are no active electronics within the access network. A Passive Optical Network includes an optical line terminal (OLT) and an optical network unit (ONU). The OLT resides in the CO (POP or local exchange). This would typically be an Ethernet switch or Media Converter platform. The ONU resides at or near the customer premise. It can be located at the subscriber residence, in a building, or on the curb outside. The ONU typically has an 802.3ah WAN interface, and an 802.3 subscriber interface. Passive OpticalNetworks is configured in full duplex mode (no CSMA/CD) in a single fiber point-to-multipoint (P2MP) topology .
The OBS network is composed of edge and core routers plus Wavelength Division Multiplexing WDM links. Burst aggregation and corresponding burst control packets are the edge routers responsibility, while data burstswitching/routing is held at the Core routers. In the core nodes the Just-Enough-Time (JET) protocol applies the “out-of-band” transmission fashion, where the control packet is detached from dara burst before it travels on a separate channel, for a uni-directional resource allocation. In case of having more than one output-port leading to the same destination, it is most probably that the shortest path is chosen in the unequal Probabilities Outputting Scheme (UPOS) analyzed by Ho (2009). The UPOS does not use a fixed probability for all output-ports which makes it more suitable for the actual Internet traffic environment as it reserve the short path for high priority traffic via prioritizing the multi-class traffic of OBS networks. This technique resulted in a concrete enhancement in QoS through giving high priority classes a pre-emptive chance to allocate Short-Path-Ports (SPPs) and also occupy the idle ports over those classes of low priority level.
However, It is well-known that the Poisson process is not a good model for wide area traffic , and it is unlikely that the burst arrival processes in future opticalnetworks will be accurately characterized by the Poisson model. Another problem is that in the Poisson process, an arrival occurs instantaneous, and the service time required by the arrival is independent of the inter-arrival time of two consecutive bursts. However, in opticalburstswitching, the service time of a burst is the duration of the burst, which is not independent on the inter-arrival time of the bursts. For example, the inter-arrival time of between a very long burst and the following burst must be very long, too. Therefore, more sophisticated models are required in order to advance our understanding of the performance and the potential of OBS networks. In , an OBS node is analyzed assuming the On/Off traffic, which is more real- istic than the Poisson process. However, the arriving burst is assigned a destination output port following the uniform distribution. This is not a practical assumption, since in most cases, a particular output port has more traffic than other output ports. It also assumes that all input wavelengths have the same On/Off process. That is not a practical assumption, either. Finally, the problem with On/Off process is that it only models a single class of bursts.
(JET) signaling protocol, a source node sends a control packet and then sends the corresponding burst after some offset time [4-5]. Using extra information to better predict the start and end of the burst, a wavelength is reserved efficiently to transmit the burst. Therefore, the JET protocol will achieve a better performance than other signaling protocols. There are many interesting topics in OBS, such as burst scheduling, burst assembly, offset time setting and contention resolution.
be applied. The efficient contention resolution strategies are importance in the OBS networks , such as wavelength conversion , fiber delay lines , burst segmentation , and deflection routing . The wavelength conversion and deflection routing techniques were shown to be the most effective contention resolution strategies for OBS networks [15-16]. Wavelength conversion is efficient and does not commence the delay in the data path, but it was expensive for deployment. In recent years wavelength conversion can be designed using Arrayed Waveguide Gratings (AWG) which are simple to fabricate, inexpensive and consume no power [17, 18]. Deflection Routing does not require any additional hardware so it can be easily implemented in existing network. Wavelength conversion is needed to switch the contended burst into other not occupied output wavelength channel at the same output fiber link. The contended burst redirected into another output link of the node using deflection routing. Otherwise, when the output port occupied with other bursts, and there is no any contention resolution mechanism available, then the burst will be blocked.
Different schemes in OpticalBurstSwitching are Tell- And-Go (TAG), Just-In-Time (JIT) and Just-Enough- Time (JET). TAG is an immediate reservation scheme. In TAG, the CB is transmitted on a control channel followed by a DB, which is transmitted on a data channel with zero offset. The CB reserves the wavelength and FDL at each intermediate node along the path for the DB. When the DB reaches a core node, it is buffered using the reserved FDL until the CB processing is finished. Then the DB is transmitted along the reserved channel. If no wavelength is available for reservation, the burst is dropped and a negative acknowledgement (NAK) is sent to the source. The source node sends another CB after transmitting the DB for releasing the reserved wavelengths along the path. Here, the burst size is not fixed in advance. FDLs are expensive and they can only buffer data optically for a very short time. Optical buffering is the main drawback of this scheme. Furthermore, if the “release” CB which is sent to release the reserved bandwidth along the path is lost, then these wavelengths will not be released and this creates bandwidth wastage .
Abstract: The opticalnetworks square measure a logical option to meet the growing communication demands, with fiber links giving immense bandwidths on the order of twenty five THz. so as to satisfy these growing wants, optical wavelength division multiplexing (WDM) communication systems are deployed in several telecommunications backbone networks. In WDM networks, channels square measure created by dividing the information measure into variety of wavelength or frequency bands, every of which might be accessed by the end- user at peak electronic rates . So as to with efficiency utilize this information measure, we'd like to style economical transport architectures and protocols supported progressive device technology.
Overlay networks have recently gained attention as a viable alternative to overcome functionality limitations (e.g., lack of QoS, multicast routing) of the Internet. They offer enhanced functionality to end-users by forming an independent and customizable virtual network over the native network. The basic idea of overlay networks is to form a virtual network on top of the native network so that these specialized overlay nodes can be customized to incorporate complex functionality without modifying the underlying native routers, overlay networks can be of different classes based on their specific purpose. Some common forms such service includes  are peer-to-peer (P2P) overlays, content delivery networks (CDN), and service (infrastructure) overlays.
As the favorite candidate for future all-opticalnetworks, OpticalBurstSwitching technology has received a lot of attention from scientists and researchers to solve its main issue (i.e., very large burst loss) which is caused by data contention at the buffer-less core node. To reduce burst loss and increase network performance, many variations to the JET (Hwang et al., 2003) and JIT (Wei and McFarland Jr, 2002) based OBS have been proposed in the literature. Time variant is one of them and it is the focus of this paper. Due to space limitation, the reader is referred to (Venkatesh and Murthy, 2010), (Maier, 2008) and (Maier and Reisslein, 2008) for more details on other OBS variants. In what follows, the main time variants of OBS are discussed.
Average number no packets in a buffer and average waiting time of packets in a buffer for the proposed modified ring network, employing different values of B vs packet arrival rate has been investigated with MATLAB. In fig.3 (a) and fig. 3(b) the comparative performance analysis of opticalburstswitching ring network with and without using proxy node for B=10 and 20 have been shown respectively. For a fixed value of B the nature of the curves of both network are qualitative similar but the modified ring network (with proxy node) can accommodate larger no of packets in its buffer for a particular packet arrival rate. As a result the packet dropping probability decreases in the case of modified ring network and correspondingly throughput of the network increases. In fig. 4(a) and 4(b) the average waiting time in buffer for both types of networks has been depicted. The graph shows that the average waiting time increases for the network with proxy node. The result is obvious because if the proxy node connected between the source and the destination node then the packet has to travel a longer distance so the waiting time will also increase. This result is quite interesting in network application because without adding any additional hardware the incoming packets could be retained in the buffer for longer time thus the packet blocking probability or packet loss probability will be decreased significantly.
Contention resolution is necessary when two or more bursts try to reserve the same wavelength of a link in same time. This is called external blocking. In OBS, when two or more bursts contend for the same wavelength and for the same time duration, only one of them is allotted the bandwidth. The novel idea of this kind of networks is to keep the information in the optical domain as long as possible. This allows the system to overcome the limitations imposed by the electronic processing and opto-electronic conversion, leading to high-speed data forwarding and high transparency. In principle, the OEO conversion limits the overall transmission speed of the optical fiber system. Thus, many research work addressed this problem and many suggestions aimed to overcome the OEO hurdle and build an All Optical Network (AON). On the way to an AON, and especially due to lack of advanced optical devices that can effectively replace their peer electronic devices, opticalburstswitching has gained a great potential as it represents a good compromise between Optical Circuit- Switching (OCS) and Optical Packet Switching (OPS) . In this architecture, electronic switches are replaced by optical switches that can handle the optical information. In this paper we will be interested in OpticalBurstSwitching (OBS) as a forwarding technique. In OBS, data packets are collected into bursts according to their destination and class of service. Then, a control packet is sent over the specific optical wavelength channel to announce an upcoming burst. The control packet, called also OpticalBurst Header (OBH), is then followed by a burst of data without waiting for any confirmation.
Recently, Wavelength Division Multiplexing (WDM) opticalnetworks supporting beyond 100 Gbits/s of bandwidth are becoming the technology of choice in nextgeneration networks [3, 4]. Optical circuit switching (OCS) and Optical packet switching (OPS) are main paradigm used for data switching in the optical core networks [5, 6, 7]. However these schemes have some limitations such as round trip delay, bandwidth under-
OpticalBurstSwitching (OBS) networks are new networks in optical field. OBS networks can deal with the large traffic of the internet because of their optical links and bandwidth. For dealing with large traffic, OBS networks exploit Wavelength Division Multiplexing (WDM) technique. Because the bandwidth of the links in the networks are so large to carry only one burst, the links are divided to more than one route to carry the packets and all of the links can work individually. This technique called WDM and it prevents bandwidth wasting in the network.
In this chapter, we focus on wavelength conversion to reduce contention among data bursts. We consider only the case of limited-range wavelength conversion. In limited-range wavelength conversion, data bursts arriving on a wavelength can be converted to a fixed set of wavelengths above and below the original wavelength. The degree of conversion d defines the number of target wavelengths for conversion on either side of the original wavelength. Thus an incoming data burst can be converted to a total of (2 ∗ d + 1) destination wavelengths. Yates et al  were the first to model a system with limited- range wavelength conversion. Until then, all the papers assumed full-range wavelength conversion. In , the all-optical translators considered were based on four-wave mix- ing in Semiconductor Optical Amplifiers (SOA). A model was developed to analyze the blocking performance of two-hop and multiple-hop paths in unidirectional ring and mesh- torus networks. They also stated that almost all of the network performance gained by full-range conversion can be attained by half the number of converters employing limited- range wavelength conversion. Tripathi and Sivarajan  developed an analytical model for fixed routing of lightpaths which can be applied to any topology. They stated that the benefits of full-range wavelength conversion could be achieved by limited-range conversion with degree of conversion being only 1 or 2. Rosberg et al  proposed a framework to compute the path blocking probabilities in an OBS network. They showed that for OBS networks, even a small degree of conversion can bring about significant reduction in blocking probabilities. However, they also showed that for OBS networks unlike previous studies which are based on acknowledgement-based networks, full-range conversion re- sulted in significantly less blocking probabilities than limited-range wavelength conversion with small degree of conversion. The proposed framework used a generalized form of the Erlang fixed-point approximation. Akar and Karasan  proposed a method to exactly calculate the blocking probabilities in an OBS switch with partial wavelength conversion, i.e number of converters available being less than the number of wavelengths. A numeri- cal method was used to solve the underlying continuous time Markov process. They also showed that their method could be used to efficiently calculate blocking probabilities for very large number of wavelengths.