OPTICAL BURST SWITCHING ISSUES AND ITS FEATURES

Transcription

1 OPTICAL BURST SWITCHING ISSUES AND ITS FEATURES A.M.Balamurugan. 1, Dr.A.Sivasubramanian. 2 Research Scholar and Associate Professor 1, Professor 2 Department of Electronics and Communication Engineering St.Joseph s College of Engineering, Chennai , Tamilnadu, India Abstract The Optical Burst Switching (OBS) is a growing result to the technology issue that could achieve a feasible network in future. They are featured with the ability to meet the bandwidth requirement of those applications that demand intensive bandwidth. There are more domains opening up in the OBS that clearly shows their advantages and their capability to face the future network traffic. However, the concept of OBS is still far from perfection facing issues in case of security threat. The transfer of optical switching paradigm to optical burst switching faces serious downfall in the fields of Burst aggregation, routing, authentication, dispute resolution and quality of service (QoS). The paper deals with the issues, threats and alternative solution in case of network limitations. Further, the paper gives the history of optical burst switching architecture and how researchers derived the optical burst switching from the packet and circuit switching with the optic fiber. The contention resolution technique contributes the clear picture of transmission of burst from source to destination in the proposed paper. It also discusses the benefits and drawbacks of each techniques and schemes. The paper has definite diagrams for each protocol and scheme that helps the readers to understand the optical burst switching better. Later the Paper is to bring in a holistic view on the recent trends, researches and outcomes. The OBS architecture is unique and is to be studied in detail to eliminate the possible threats, resulting due to the unstrtured or ill-defined structure of the network. It also provides in a gist of the current protocols like that of Just Enough Time, Just In time and other contention resolution techniques. The OBS are cost effective and are designed to be flexible and faster when compared to the wavelength division multiplexing networks. The major contentions of the OBS are fake burst headers, compromised nodes, creating an image of heavy traffic in network. In reality, those contentions are jobless in the current scenario. 1. INTRODUCTION The number of internet users in the late 90 s was hardly 2 percent of the then population. However today even with the rapid increase in the population there is about 8 percent of the world population that has access to internet every day. With this kind of dramatic increase in the number of users and the increasing role of internet the global trade and business there also comes the need for a network where it can be set at low cost, with high efficiency and with greater reliability. With this kind of traffic comes the data loss and handling the network becomes difficult. The main aim of the paper is to bring out the advantages of OBS network, the various process and schemes or methods of OBS, the current threats faced by these networks and the probable recommendations which can help these network more efficiently. The network had relied on the Circuit switching and that of packet switching where dynamic handling of data was absent and was not efficient respectively. The OBS which was has dynamic allocation of wavelength and with the separate control packet that carries in the destination of the data burst had created a better and efficient usage of the bandwidth that is available. The methods and Schemes such as the Just-Enough-Time, Just-In Time, Optical buffering, wavelength conversion and deflection routing that are used in the Optical burst switching have enhanced their efficiency. The schemes such as the conversion of wavelength, buffering the optics, deflection routing etc are great supporters in eliminating the malicious attack. They help in identifying and removing the threat. The conversion of wavelength helps in decreasing the different burst fighting for the same wavelength which could result in the loss of data burst. The JET and JIT as well are the protocols that ensure the delivery of the packets at right time and also clear of the delays that could happen. They are more like emergency supporters for the data burst. The greatest problem faced by the OBS at current situation is the often compromised nodes that result in compromised network. These attacks weaken the entire network. They cause unauthorized access to data, duplication of data, blockage of delivery in the destination and creation of artificial traffic leaving the data burst with no possible wavelength which ultimately results in loss of data burst. Added to it is the lack of authentication upon the delivery of data burst on the destination node to the source node. The paper on the whole has defines the various features, advantages, threats and probable solution to the issues of the optical burst switching concluding its potential to become the future efficient network that can support even the dynamic allocation with the help of wavelength division multiplexing technology. OBS network is after all the best when compared with the OCS and the OPS. The growing network traffic had made it critical for efficient use of bandwidth that could be also flexible under a new architecture. The raw bandwidth that are available on fiber optic links have gone up drastically with the advancement in the Wavelength Division Multiplexing (WDM) while the available optical network architecture is not capable of supporting this dramatic increase and use the dynamic bandwidth to support the burst network traffic. 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2 Figure 1 The Optical transport Network The architecture of the optical transport network is structured to consist of nodes and edge as shown above. The Ingress node takes in all the request from the multiple clients and then sends then to the core through the high defines and capable Dense Wavelength Division Multiplexing. While the Egress node does the function of receiving the data and then process them on dispatching it to that particular client. Currently the more popular optical transport network that are available are Optical Circuit switching (OCS) Optical Packet Switching (OPS) and Optical Burst switching (OBS) They are usually designed on the basis of method of resource allocation and the degree of coarseness for such allocation of resources. The OCS network s connection consists of all optical is also known as Light path [1]. It is connected between two nodes in the optical core to create logical circuit. These light paths can be connected dynamically as and when the data request come in or provisioned statically depending on the probable traffic demand. They are suitable networks in the case of stable or constant traffic rate however they fail in the case of dynamic traffic. The two way reservation scheme results in a trip there and back delay and in case of heavy traffic, it requires the bandwidth to be provisioned during the peak traffic load leaving the network inefficient in the resource management. The OPS, does transmits the data through optical packet which is delivered to the optical core does not require it to be converted into electronics at intermediate core nodes. The packet by packet can be allocated with dynamic bandwidth resulting in high degree of statistical multiplexing that allows efficiency even when the traffic is variable and intense. There are few disadvantages in the OPS, one is that they are facing technical challenge on implementation of optical buffer and as well they are failing to satisfy the condition of fast header processing and strict synchronization which adds to the difficulty in its implementation. The OBS is an upcoming network that has stroke a perfect balance between the finely grained packet switching and the coarse grained circuit switching [2]. This network takes the incoming data and put them in basic units that are called as data bursts (DB) and then transport them to the core. The control packet carries the information like the size of the data, the delivery address and the quality of service (QOS) of the OBS performs the controlling of signal from out of band. The control packet has a different the DB and that allows them to be checked at every intermediate beforehand while the data burst arrives later. The OBS faces little technical issues when compared to the OPS and are more efficient in allocation of resources dynamically and also paves way for statistical multiplexing of data. The OBS eliminated the technical faults of the OPS by adding up the data burst size and by out-of- band signaling. However the issue of data loss due to aggregation of the burst size in few cases is still present. While the circuit and the packet switching has been there in the field of network in handling the voice and data communication for a long period now, while the ideas and the principles in regard to the OPS and OCS are still evolving. The OBS when compared is relatively new and was introduced for the Wavelength Division Multiplexing Network [3] very recently. The notable differences between these three are noteworthy. While the OPS and OBS are closely similar, it differs from each other in conceptual way. The basic difference between them is in the granularity of their entity switching. However the OBS has proved their supremacy above the OPS and OCS, they are often facing the lack of security. Their single compromised node can easily act as an entry port for malicious attack on the entire network. Therefore the prominent lack the OBS network still faces is the lack of neatly designed authentication system that will help the nodes in Authentication on the delivery of the burst to the intended address and also on their delays, which can notify the network on any of the potential threats. 2. KEY ISSUES: Jet-Enough-Time (JET). Jet-In-Time (JIT). Buffering of Optics. Conversion of wavelength. Deflection Routing. Segmenting the burst. Separate Control, Delayed Transmission Scheme (SCDT). Threats and Vulnerabilities in OBS Networks. 3. ANALYSIS OF KEY ISSUES: 3.1 JUST-ENOUGH-TIME (JET): This protocol is used in the optical burst switching for sending a packet from origin node to delivery node comes under the delayed reservation scheme. It is meant for Two-way reservation protocol and has some unique characteristics such as delayed reservation (DR) and the ability of combining delayed reservation with the help of fiber optical delay lines (FDL) based buffered burst multiplexers (BBM)[2]. In the late eighties, the TAG Volume 2, Issue 3 May June 2013 Page 307

3 protocol was used for the optical burst switching and it lacks these features of JET protocol because it is a one way reservation mechanism. Figure 2 Optical Burst Switching using JET protocol The Figure 2 explains the basic concept of Jet Enough Time (JET) and the source node contains a burst to send to the destination. At first, the protocol JET helps the source node to send the control packet through the physical/static links between the IP entities. In order to maintain the routing table, topology (structure of the network) and the information about the source node and destination node, packet switching supports the JET protocol between the contiguous IP entities. The control packet reserves the path for the burst to reach destination based on the IP addresses of the links by composing all the optical switches along their path. After that, burst can be reached to the destination without passing through the IP intermediate nodes. From this way the JET protocol supports the Optical burst switching by depreciates the latency and the processing load in the IP layer [2]. Once the burst passed through the particular link, the wavelength used by the burst on the particular link will be released automatically or by an explicit mode. Due to this feature, the burst can reserve the bandwidth of the similar wavelength on a particular link from different source to different destination node. If control packet fails to set aside a bandwidth for the burst in any node, then the burst will be blocked or dropped from in a specific node. So, the negative response is sent to the respective source node for retransmission. The optical burst switching supports both reliable and non-reliable transmissions between the IP entities. The action of retransmission is necessary for both the control packet and the burst from source node to destination node. The OBS should have some applications protocols for the retransmission action. Sometimes the OBS sends data automatically to the destination node with the help of upper application layer protocol like transmission control protocol (TCP) [2]. Because of this retransmission, there will be some wastage of bandwidth takes place. In order to avoid that, the blocked burst must be stored in an electronic buffer after the two conversions takes place. They are optical to electronic conversion and electronic to optical conversion based on the respective destination. The use of fiber delay lines in OBS is to create delays at intermediate nodes. It is not mandatory but it support OBS to eliminate the bandwidth waste and accelerate the performance of quality of service in the network. 3.2 JUST-IN-TIME (JIT): This is another protocol used in the optical burst switching comes under immediate reservation scheme. The source node sends the control burst for wavelength reservation to the upcoming data burst. Once the wavelength is set aside or utilized, the control burst processing is over in the network. The data burst from the source node is transported to the intended delivery address over the path of the control burst. It takes place when the transportation of the burst after a delay (Offset time) should be greater than the control burst s processing time in the network. When the control burst reaches closer to the destination node, the offset time decreases and the idle time of the reserved wavelength also decreases. It means that the data burst in the particular path will get transmitted after some time. There are two protocols (JIT and TAG) under the immediate reservation scheme. It has some difference in features and characteristics between them. In JIT, there will be time gap or time line between the control and data burst because of that buffering is avoided at each node and wavelength is reserved until the first bit of the data burst arrives at each Figure 3 Optical Burst Switching using JIT protocol and every node in the link. The reserved wavelength will be released after the data burst passes through the link by using the in-band terminator. Figure 3 explains how the control burst and data burst coordinates in the optical burst switching. There are few things to explain in the figure. They are t- It represents the total time taken by both the bursts to reach destination node from source node in the optical burst switching. T Setup -Total time taken by the optical burst switching to process the control burst in the source node. T Offset - The totaltime taken between transmission of data burst and the Control burst. t + T Setup - At this point, the wavelength is reserved for the particular data burst. Amount time taken for the Control burst transmission from source to destination. T Oxc - Total time taken to configure switches form an input port to an output port. Volume 2, Issue 3 May June 2013 Page 308

4 T Offset -T Setup -T Oxc - This is the time period for the wavelength is idle for the data burst in the specific path. 3.3 RESLOUITON SCHEMES IN OPTICAL BURST SWITCHING: When the different bursts from different sources, at the same time works on to reserve one particular wavelength and the same link then this scheme is useful in that case. These schemes is useful in certain cases when different burst from different source nodes attempts to have identical wavelength and link at the same time. It can be defined as external blocking [4]. In packet switching, these kinds of blocking can be prevented by using electronic buffer. This is can be avoided in the concept of packet switching by using the electronic buffer. The optical switch bursting allots the particular wavelength for one burst even if different bursts attempts to reserve the same wavelength [4]. So, the schemes are useful in dropping the unsuccessful bursts in the network. The resolution scheme helps the OBS networks to reduce the burst loss. There is three resolution schemes present in the Optical burst switching. It happens in different domains like wavelength domain, space domain and time domain. The schemes are Buffering of Optics Conversion of Wavelength Deflection routing and Segmenting the Burst. wavelength to reach the destination node. There are two conditions for this wavelength reservation In first case, the minimum amount of time W should be greater than the fiber delay line to discard the specific burst (W > D). In second case, for reserving the required wavelength the condition should be (W< D) i.e., the minimum amount of time should be less than the fiber delay (D). The reservation time period should be the current available time until then fiber delay lines will hold the data burst through the reserved FDL. FDL transmits the data burst through the required wavelength to the output port when the waiting time reaches the minimum amount of time (W). There are lots of limitations in this reservation scheme. They are 3.4 BUFFERING OF OPTICS: The concept of optical buffering is done by using the Fiber delay lines (FDL). Fiber delay lines are used in optical buffering because of less memory in optical RAM. A buffer will be created in the Lines after the implementation of delay lines either in parallel or stages. The buffer can hold the data to delay sometime in the particular node. The buffer size in the optical buffering is precise and controlled compared to the other schemes. This is due to the concern of signal quality and also physical space in the optical RAM. Mostly, the FDL looks Massive. So, it needs more length of fiber (Over kilometer) to delay the single packet for 5 micro seconds [5].This reservation scheme contains two phases. They are In output port, the wavelength should be reserved [5] and In optical fiber, the fiber delay lines (FDL) must be reserved. The scheduler searches for a more apt wavelength in the output port, in the first phase of the reservation scheme. If the needed wavelength is idle (t + Ω) then it will be reserved immediately for the data burst. Sometimes, the required wavelength would not available in the path node for certain period of time. The data burst should wait for minimum amount of time W to reserve the required Figure 4 Optical buffering using Fiber Delay Lines (FDL) Controlled Physical size of optical random access memory (RAM) because of that high load and traffic in the node. It is not applicable for large scale deployment because of Signal dispersion and attenuation in the node [5] 3.5 CONVERSION OF WAVELENGTH: This is the next resolution scheme to carry bursts from origin node to intended delivery node. Whenever there is a situation of no route or lack of common wavelength in the link from origin node to intended delivery node is faced then this scheme can be used. The light paths are necessary for carrying the messages in the wavelength routed networks. For this, there are conditions to be met. A successful communication is the one that is able to satisfy the constraint condition for wavelength continuity in the network. When the incoming channel converts the wavelength to the different wavelength on the outgoing channel is called as Wavelength conversion [6].For this conversion, the particular device is used for converting wavelength of incoming signals to a different outgoing wavelength signals. There is no need to satisfy the wavelength Volume 2, Issue 3 May June 2013 Page 309

5 continuity constraint for this conversion. There are two classifications for this scheme. They are Optical-electronic conversion and Electronic-optical conversion. The following sub headings are different conversions involved in wavelength conversion scheme. The conversions are Full conversion: In this conversion method, the different channels can be connected together by shifting wavelength to the channels. Limited conversion: For this method, wavelength shifting is not possible to the channels. So, there is no chance of combining all the channels together. Fixed conversion: It is a kind of limited conversion method and has some restrictions too. For this conversion, each node and channel can be related to the established channel on all other links [4]. Sparse wavelength conversion: This conversion takes place only in the subset of nodes in the network. The process of wavelength conversion is explained in the above figure 4. Consider the task is to establish the connection between the node pairs (A, D) and (C, D). The nodes A and C looking for the same wavelength W1 to complete the task i.e., to reach the destination node D. so, the nodes A and C approaches the node B to form the link called BD. Unfortunately, the link BD has wavelength W2 to form the link. the propagation for this packet would be high and it is not favored for the packet- switched networks because of out of delivery of packets and potential looping. The buffer capacity of the wavelength division multiplexing optical networks is small and conversion of wavelength is not applicable. So, the concept of deflection routing helps the optical networks to stable from packet losses. Let s consider the nodes A and B are transmitting the bursts to the node E. Previously, that the nodes A and B sends the burst control (CB) to the outgoing channels for reserving bandwidth for the DB and can be denoted by C (A, E) and C (B, E). Assume that, the burst C (B, E) from node B reaches the intermediate node C earlier than C (A, E) which is from node A. So, the burst C (B, E) from node B reserves the particular bandwidth to reach the destination node E. When the burst C (A, E) form node A reaches node C, the bandwidth and link CE would not available because of delay. After that, the node C checks the other path to deflect the burst C (A, E) to reach the destination node E. When it s not deflected to the other node then the burst will be dropped. Node C deflects the burst C (A, E) to the other intermediate node called D based on the routing table and checks the deflection link is idle or not. So, the node D transmits the burst C (A, E) to the destination node E and the burst C (A, E) reaches the end point in the network with some extended delay. In this method, the fiber delay lines (FDL) is used for the idle optical links to the blocking bursts for buffering function. Figure 5 Wavelength conversion method Let s assume that the link passage (A, D) is satisfied the wavelength continuity constraint to form the link between B and D and the node C fails to meet the constraint. So, it has neglected in the network. The wavelength converter is used to convert the wavelength from W1 to W2 to reach the destination node called D by forming the link BD. The reuse values are high of about 10% to 40% when availability of wavelength is limited by using the wavelength converters [4].Now days, wavelength conversion algorithms are used in the network to reduce the wavelength converters. This method is really expensive in real networks deployment. 3.6 DEFLECTION ROUTING: When the dispute is set to be cleared by sending or transmitting the disputed packet to an output port other than the intended port is called Deflection routing [7]. But the packet which is deflected may reach the destination by taking the longest path. Due to this action, Figure 6 Deflection routing method The above figure explains the process and concept of deflection routing method. This method helps the network to improve the performance of the network and over all link utilization. The non-deflected burst process is called as Normal deflection failure [4].The implementation of deflection routing in the network has many benefits than other methods of Contention resolution techniques. Instead of dropping the burst, the deflection of burst avoids the wastage of bandwidth. If the burst is dropped, the retransmission of same burst form source node occurs and is to reach the destination node. So, the dropped burst transmission delay equals sum of the dropped burst delay and the total time taken for the retransmission of the burst. However, bandwidth wastage would be high for the retransmission of the burst for longer distance links. The algorithm called Limited deflection is used for this method to avoid burst looping [4]. In just enough time Volume 2, Issue 3 May June 2013 Page 310

6 (JET), Fiber delay line is combined with the deflection routing tends to minimize the offset time of the burst [7]. 3.7 SEGMENTING THE BURST: The segmenting of burst is used in the burst switching to avoid limitations such as packet loss in the time of contention. The contention will make the burst into multiple segments and results in the decrease of the overlapping of segments. As and when the output port transmits or transfers itself from one burst to another the rest of the packets are also dropped [8]. This method mainly concentrates to reduce the loss of priority burst. The burst segmentation consists of two techniques when collision of burst occurs in the network. The two techniques are Segmentation of even the tail of the data burst [8]. Also segments the head of the disputed burst in the network [8]. There will be a dispute between the source burst and the burst that is disputed. For this policy, the contending burst wins the contention [8]. The process of segmenting has to done for the source burst and tail of the segmented source burst can be transferred to the next immediate port that is in rest unused or will be neglected. Deflect first and drop policy (DFDP): The policy states that upon receiving a disputed burst, the network can push them to a port that is idle. On the event of no such port being available the next action to be performed by the network is to throw away the disputed burst away from the network. Deflect first, segment and drop policy: Under this policy the first action of the network is to send the disputed burst to an available port, failing the source burst is to be segmented and the segmented tail from the source burst is disposed from the network during the transportation of the disputed burst. Table 1 Comparison of contention resolution schemes Figure 7 Burst Segmentation method The reason for segmenting the tail of the initial or source burst than head of the source burst is that this will ensure that the packets are received without a break from the origin node to the intended node. Because of that, the source will assume the dropped packets are retransmitted after certain amount of time. During the segmentation of the burst, the routing table and its control message will be updated frequently. So, the segmentation takes place only in the middle of the burst. We have seen deflection routing method in the optical burst switching. Even, deflection routing can be applied to this burst segmentation method for to avoid the tail segmentation of the source burst and head segmentation of the burst under the dispute. This method helps to avoid bandwidth wastage of the dropped burst by deflecting the burst to the intermediate nodes to reach the destination. Using deflection in burst segmentation method accelerates the network performance. To reach destination node, there will be two or more alternate paths stated by each node of the network link. All nodes in the network link will specify the shortest paths in an ascending order. The quality of service is the main factor in optical burst switching and it depends on which burst (Contending or original) is to segment or deflect during the contention. There are three policies involved in the quality of service scheme. They are Segment first and deflect policy (SFDP): RESOLUTION TECHNIQUE Wavelength Conversion Optical Buffering Deflection Routing Burst Segmentation BENEFITS Accomplished Solution Construction Cost Is Less No Need To Have Any Hardware Devices Packet Loss Ration Is Less Compared To Other Resolution Techniques 3.8 SEPARATE CONTROL, DELAYED TRANSMISSION SCHEME (SCDT): DISADVANA TGES Cost Is High Delay Between The End Users Is High Out Of Order Arrival Needs Control Handling. There are many schemes is available to reserve the bandwidth in the channel. The separate control, delayed transmission scheme uses one pass reservation to perform the reservation in the channel link. For reserving the bandwidth in the channel, the request is directed to the separate passage in a different packet. The transmission of data burst (DB) is delayed for certain offset time. The offset time supports to build the switching matrix and process control information by accelerating the immediate nodes in the channel link. SCDT needs the complexity in edge nodes and provides extra delay to the data bursts. The offset time needs to reduce both the processing time of the burst and the offset information present in the Volume 2, Issue 3 May June 2013 Page 311

7 header by using actual delay. This scheme is much contrast to the two reservation scheme in the optical networks connection because the burst sender does not consider for an acknowledgement of its request. The advantage of this scheme is higher efficiency due to the absence of propagation delay. The SCDT scheme has some factors to be considered for designing optical burst switching. They are Buffers for data burst at intermediate nodes: The buffer or FDL must be used to delay the data burst and also it helps to keep the system in a less complex manner. Resource reservation mechanism: This scheme is based on the reservation of bandwidth and the buffers for better efficiency in the channel link. QOS support: The quality of service plays an important role in the field of networking for accomplished end results for the users. Protocols: The protocol design for this scheme mainly depends on the two methods such as resource reservation scheme and QOS support. Even though it s an one way reservation scheme, the protocols should be two- way for reporting the blocking circumstances and also for successful reservations. Node architecture and technology: In this part, consider all input and output interfaces, reservation units, switching systems, buffers and also fiber delay lines. WDM technology (Wavelength Division Multiplexing): The OBS mainly depends on WDM technology such as wavelength conversion. For better transmission, OBS requires the maximum wavelength channels in the node architecture. 3.9 THREATS AND VULNERABILITIES IN OBS NETWORKS: There are lots of potential threats present in the OBS networks. In order to have secure and better communication, the data burst should follow the control signal path from source to destination node. It should be processed by each node in the network link. The node tries to duplicate or steal information from the control signals because control signals are processed by all intermediate nodes in the network. The identified threats are BURST HEADER FLOODING ATTACK: The intruders Compromises any one node and Copies and replicate its original Burst address. The Duplicated Copies of the Burst address are then feed to the next intermediate node of the compromised node. The next intermediate node upon receiving such burst header tries to reserve for such duplicate address. Therein the intermediate node is under Buffer with overflow. Finally, it results in not allowing the intermediate node to reserve any resource even if they are effective burst header. It is named as Burst Header Flooding attack FAKE BURST HEADER ATTACK: The intruder tries to send malicious burst control header to the particular node. These headers redirect all the data to a fake destination that is controlled by the attacker. The original destination will be ignorant of this tapping and the security being compromised as the fake destination forwards to the real destination disguised as the source and sends through the same data burst [9]. Figure 10 Fake burst header attack DENIAL OF SERVICE ATTACK: The OBS core that decides the path of the data burst follows the unoccupied or unused outgoing Wavelength division Multiplexing (WDM) channels to make their decisions in deciding their path. Whenever there is a non availability of WDM, the burst packets that are to be transited are thrown away. The routers having routed the control packet with their destination does not have well defined mechanism to Counter check the burst sent upon they reaching their destination. This loophole can be used to exploit the network by setting up a malicious burst header that would push WDM to be labeled as busy at all times when in reality they network is completely free [9]. Figure 9 Burst header flooding attack LAND ATTACK: A virtual source code is those that redirect the incoming burst and multiples their destination to any wavelength. Thus under this attack the malicious header modifies the Volume 2, Issue 3 May June 2013 Page 312

8 intended address and redirects them to the source node resulting in the data burst making a round trip and reach both the intended delivery address as well the source node wasting the resources of the network [9]. Figure 11 Land attack MALICIOUS BURST HEADER INJECTION: The data burst simply follows the optical path and does not possess any idea on routing the information to their intended destination in the OBS network. Hence as the burst header is set on a schedule and enters the network is lost to the unauthorized or illegitimate address. This is mainly due to the lack of absence of authenticating authority in the network. This type of attack is called as Malicious Burst header injection. Figure 12 Malicious burst header injection CIRCULATING BURST HEADER ATTACK: Figure 13 Circulating burst header attack. This is a type of attack where in two or more compromised nodes are pulled together to form an attack on the OBS network. They flow in an already circuited path slowing down the delivery of the Data burst to its destination. Under this one comprised node acts like a master controlling the rest in the predetermined circuit and forwards the burst control header to the intended recipient [9]. This results in wastage of resources and also in blockage and unnecessary delay on data burst. 4. CONCLUSION: Almost, the optical burst switching has attracted most of the researchers because of its potentials and the benefits related to the bandwidth requirement for the internet traffic. The internet traffic is one of the major problems in the field of networks because it creates the bandwidth inefficiency due to the high number of internet users. Another reason is depends on specific bandwidth applications like video conferencing, and other multimedia applications. To meet this demand, the optical cables were placed for better communication instead of copper cables. There are lots of drawbacks in the copper cables. They have shown higher bit error rate, interference, security problems and end to end connections are not satisfactory. That s the reason the optical cables came into the second generation optical networks. It can be implemented only in wavelength division multiplexing networks. The wavelength division multiplexing (WDM) helps to use the full bandwidth utilization of the optical fiber. The basic fundamental of WDM is to divide the channel by assigning each channel to different wavelengths. The paper discusses that the optical circuit switching (OCS) and optical packet switching (OPS) plays are feasible to optical burst switching networks. The OPS and OCS have some limitations related to the bandwidth utilization because the period of data broadcast is less than the circuit setting up period. The optical burst switching (OBS) is related to the optical network technology that prefers to increase the optical resources in the network. The OBS transmits the data in an optical fiber in different channels by assigning different wavelengths to each channel independently. Each burst has two parts: Control burst (CB) and Data burst (DB).The basic principle is to calculate the magnitude of the burst depends before the broadcast of control burst (CB) and also the offset time is established on the step count between the commencement node and destination node. The architecture of OBS has three components. The components are ingress edge node (first node), core node (second node) and egress edge node (third node). The three components have different functions to transmit the burst from Source node to destination. The first node performs the assembly of burst and node organizing functions. The second node does the assigning of wavelength to the respective nodes and egress edge node accomplishes the packet forwarding and burst disassembly to the outgoing channels. Volume 2, Issue 3 May June 2013 Page 313

9 According to my view, the optical network is going to rule the world of networking in the next five years. It takes time to accomplish optical networks from source and destination because of high cost rate. In this paper, we discussed about the key issues facing optical burst switching. We have discussed eight issues in this paper and each issue deals with some benefits and drawbacks. Each issue has to meet some conditions for successful transmission of data. In future, the resolution schemes might provide some solutions to the researchers for better transmission of data. The scheme tries to avoid the dropping the burst from the network. Instead of that, the node deflects the burst to the other intermediate nodes by using the converters and electronic routers. This action can save the bandwidth wastage in the network. During deflection of burst, the node should know the shortest path to reach the destination. If something goes wrong in that, it leads to the maximum bandwidth wastage in the optical networks. To check the shortest path to reach destination, the algorithms can be used at each nodes in the network. The design of the scheme should not be complex because of the changes in the network. The scheme such as the separate control, delayed transmission scheme (SCDT) is yet another marking for the optical burst switching. However the threats that the network undergoes and face are common and are mostly due to their structural lack in certain cases. The network with their super high efficiency in the usage of the bandwidth and in supporting the dynamic allocation and the increasing traffic is far above from their ground level in their phase of development. The network is built on a simple architecture with a great deal of simplicity and easy administration function which in my opinion is equally important in any network. The potential threats have pulled back the development of the OBS network in the recent past leaving them with a loop that could be rectified if looked at close. Some of the threats the network face are the fake burst header attack, circulating burst header attack,denial of service attack, land attack, burst header flooding attack and malicious burst header injection. The common lack found in the network that leads to the above threats are mostly because of the absence of the mechanism of a system in which the source node could get an authentication upon the delivery of the burst to the destination. The OBS network can be brought down completely upon the compromise of one of its node. In threats like that of the malicious burst header injection and fake burst header scheme simply takes the burst to the unauthorized persons resulting in leakage of data that could be confidential. They simply compromise the security of the network and the trust of the client in the network. The burst header flooding attack and denial of service attack both simply create an artificial traffic in the network leaving the inefficiency in the bandwidth usage and breakage in the service of the network. The growing increase which seems like traffic with the no real traffic resulting in the loss of the resource and unwanted delay in reaching the destination by the burst. In the threat like that of the land attack the attacker replicated and makes provision for the burst to reach both the sender node and the destination in a roundabout away. This increases the usage of the wavelength in the place where the needed wavelength is only 30 percent of the used wavelength. This is an incredible disadvantage to the network and simply put the very basic necessity for which the network was created in failed mode as a result. The land attack is a major issue in the OBS network. The circulating burst header attack is technically a harder attack that can compromise the entire network on its Will. They are designed in such a way that they simply function in a very organized way. The two or more compromised nodes ganging up together, when one among the compromised node leading the rest of the nodes. They direct and redirect the burst and leave them to circle in their created circle of compromised node. The end result, being the delay in the delivery of the burst to the destination. Another inherent issue caused by this type of attack is the severe loss of resource and the wavelength in their unwanted circulation in the path. When listing the advantages of the OBS, their features such as like that of the usage of burst in the place of circuit or packet as in the OCS or OPS, they are built and are supported by the wavelength and are not based on the optic fiber which was inefficient in dealing with the dynamic allocation to the core node, since the mode of transit is in the form of burst the data size can range from bigger to small, a separate channel for the control burst that goes ahead of the data burst with the necessary detail like that of the size of the burst and their reaching destination and also that the consumption of the bandwidth happening only when there is real transfer of the burst from the origin node to the intended destination. The growth of the demanded network is simply beyond the projected statistics and it still continues to grow. This kind of traffic cannot simply solved by making available of the bandwidth. It needs more than that and the technology to handle such traffic and to function efficiently in the dynamic allocation of resources. The commercial and domestic purpose of network in the field of communication no longer is passive but they demand for faster, more efficient and highly secured network. In my opinion that the OBS has all the potential that can be tapped to support the above demands when handled and refined in time, which we are to see it happen sooner. The OBS in short can be told as a perfect blend of the favorable character that is seen in the OCS and OPS with added flavor of its own. The OBS has in fact outshine and has the potential to emerge as a most popular network in future as they simply take advantage of the switching if the optics that is more transparent and that records higher achievements in the burst multiplexing. The current research in the OBS has gone high as they hold not only a great importance to the scientist but as well to the industries. 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10 ACKNOWLEDGEMENT My sincere thanks to Mr. P.M.Kalaiarasan.M.S,United States of America and Mr. Jerome Melkisidak, Managing director of Stigmata Techno Solutions to complete this paper. REFERENCES [1] Chlamtac. I, Ganz. A, Karmi. G,, Lightpath communications: An approach to high bandwidth optical WAN s, Communications,IEEE Transactions on July 1992, pp [2] Qiao, C. Yoo, M.: Optical burst switching (OBS) A new paradigm for an optical internet. Journal of High Speed Networks, No. 8, January 1999, pp [3] Haselton.E. Fletcher, June 1983, A PCM frame switching concept leading to burst switching network architecture, Communications Magazine, IEEE (Volume: 21, Issue: 6 ) September 1983,pp [4] K. Koduru, New Contention Resolution Techniques for Optical Burst Switching, Master's thesis, Louisiana State University, May [5] Lamba. R, Garg. A. Kumar, Survey on contention resolution techniques for optical burst switching networks, International Journal of Engineering Research and Applications (IJERA) Vol. 2, Issue 1,Jan-Feb 2012, pp [6] Ramamurthy. B,, Wavelength conversion in WDM networking, IEEE Journal on Selected Areas in Communications, Vol. 16, No. 7, September 1998.pp [7] Zalesky. A, Vu. H. L, Zukerman. M, Rosberg.Z, Evaluation of limited wavelength conversion and deflection routing as methods blocking probability in optical burst switched networks, Communications, 2004 IEEE International Conference on (Volume:3 ) June 2004,pp [8] Vokkarane M. Vinod, Jue. P. Jason, Prioritized routing and burst segmentation for Qos in optical burst- switched networks, Proc. Optical Fiber Communication Conference (OFC) 2002,pp March 2002 [9] Sreenath. N, Muthuraj. K, Vinoth. G,,Threats and Vulnerabilities on TCP/OBS networks, Computer Communication and Informatics (ICCCI), 2012 International Conference on January 2012, pp 1 5 Chennai , India. He received his B.E in Electronics and Communication Engineering (2002) from Madurai Kamaraj University, Madurai, Tamilnadu, India.. He received his M.E in Digital Communication and Network Engineering (2005) from Anna University, Chennai, Tamilnadu. He has 10 years of experience in teaching and guiding projects for undergraduate and postgraduate students. His research areas are Optical networks and Optical Communication. Dr.A.Sivasubramanian has received B.E. degree in ECE from University of Madras in 1990, and M.E. in Applied Electronics from Bharathiar University in 1995 and Ph.D. degree in Optical Comm. from Anna University Chennai in Currently he is working as a Prof & Head, in the department of Electronics and communication engineering at St.Joseph s College of Engineering, Chennai, India. He has 20 years of experience in teaching and guiding projects for undergraduate and postgraduate students. He has added ten international and national publications to his credit. He is a recognized supervisor for the doctoral degree programme at Anna University Chennai and Sathyabama University, Chennai. His areas of interests include optical communication, optical networks, Bio-optical Engineering, Wireless sensor and computer networks. He is a member of ISTE, IETE, IEEE, and OSA. AUTHOR A.M.Balamurugan is a Research Scholar and pursuing a Doctoral Degree in Information & Communication Engineering at the Department of Electronics and Communication Engineering at Anna University, Volume 2, Issue 3 May June 2013 Page 315