| 1. |
- Ahmed, Jawwad, et al.
(författare)
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Benefits of Connection Request Bundling in a PCE-based WDM Network
- 2009
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Ingår i: Proc. of European Conference on Networks and Optical Communications (NOC).
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The Path Computation Element (PCE) concept is considered to be beneficial in the network connection setup operations, especially in optical networks based on wavelength division multiplex (WDM) transport technology. In the PCE paradigm, communication between a node and the PCE is specified by the Path Computation Element Communication Protocol (PCEP). PCEP allows the PCC (Path Computation Client) to send to the PCE more than one LSP (path computation) request at a time, i.e., multiple LSP requests can be bundled together before being sent to the PCE. Enabling bundling, and consequently the concurrent optimization of a large set of LSP requests at the PCE, may result in significant improvements in terms of network optimization and reduced control plane overhead. However, these advantages come at a cost of increased connection setup-delay. This paper explores pros and cons of enabling bundling of LSP requests in terms of both control plane overhead reduction and benefits of sequential vs. concurrent path computation operations. A variety of scenarios are analyzed, including a WDM mesh network providing LSPs with both dedicated and shared path protection. Results demonstrate significant gains in terms of reduced control overhead using LSP bundling, and reduction in blocking probability using concurrent processing of bundled LSP requests at the PCE.
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| 2. |
- Ahmed, Jawwad
(författare)
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Dynamic Resource Provisioning and Survivability Strategies in Optical Networks
- 2013
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Optical networks based on Wavelength Division Multiplexing (WDM) technology show many clear benefits in terms of high capacity, flexibility and low power consumption. All these benefits make WDM networks the preferred choice for today’s and future transports solutions which are strongly driven by a plethora of emerging online services.In such a scenario, capability to provide high capacity during the service provisioning phase is of course very important, but it is not the only requirement that plays a central role. Traffic dynamicity is another essential aspect to consider because in many scenarios, e.g., in the case of real time multimedia services, the connections are expected to be provisioned and torn down quickly and relatively frequently. High traffic dynamicity may put a strain on the network control and management operations (i.e., the overhead due to control message exchange can grow rapidly) that coordinate any provisioning mechanisms. Furthermore, survivability, in the presence of new failure scenarios that goes beyond the single failure assumption, is still of the utmost importance to minimize the network disruptions and data losses. In other words, protection against any possible future failure scenario where multiple faults may struck simultaneously, asks for highly reliable provisioning solutions.The above consideration have a general validity i.e., can be equally applied to any network segment and not just limited to the core part. So, we also address the problem of service provisioning in the access paradigm. Long reach Passive Optical Networks (PONs) are gaining popularity due to their cost, reach, and bandwidth advantages in the access region. In PON, the design of an efficient bandwidth sharing mechanism between multiple subscribers in the upstream direction is crucial. In addition, Long Reach PONs (LR-PONs) introduces additional challenges in terms of packet delay and network throughput, due to their extended reach. It becomes apparent that effective solutions to the connection provisioning problem in both the core and access optical networks with respect to the considerations made above can ensure a truly optimal end-to-end connectivity while making an efficient usage of resources.The first part of this thesis focuses on a control and management framework specifically designed for concurrent resource optimization in WDM-based optical networks in a highly dynamic traffic scenario. The framework and the proposed provisioning strategies are specifically designed with the objective of: (i) allowing for a reduction of the blocking probability and the control overhead in a Path Computation Element (PCE)-based network architecture, (ii) optimizing resource utilization for a traffic scenario that require services with diverse survivability requirements which are achieved by means of dedicated and shared path-protection, and (iii) designing provisioning mechanism that guarantees high connection availability levels in Double Link Failures (DLF) scenarios. The presented results show that the proposed dynamic provisioning approach can significantly improve the network blocking performance while making an efficient use of primary/backup resources whenever protection is required by the provisioned services. Furthermore, the proposed DLF schemes show good performance in terms of minimizing disruption periods, and allowing for enhanced network robustness when specific services require high connection availability levels.In the second part of this thesis, we propose efficient resource provisioning strategies for LR-PON. The objective is to optimize the bandwidth allocation in LR-PONs, in particular to: (i) identify the performance limitations associated with traditional (short reach) TDM-PON based Dynamic Bandwidth Allocation (DBA) algorithms when employed in long reach scenarios, and (ii) devise efficient DBA algorithms that can mitigate the performance limitations imposed by an extended reach. Our proposed schemes show noticeable performance gains when compared with conventional DBA algorithms for short-reach PON as well as specifically devised approaches for long reach.
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| 3. |
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| 4. |
- Chen, Jiajia, et al.
(författare)
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A Novel Joint Scheduling Algorithm for Multiple Services in 10G EPON
- 2008
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Ingår i: Proceedings of SPIE, the International Society for Optical Engineering. - : SPIE. - 0277-786X .- 1996-756X. ; 7137
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- In this paper, we propose and evaluate a novel joint scheduling algorithm for multiple services which can support differentiated services and bandwidth allocation with global priority of different traffic such as Triple-play: voice, video and Internet services. Simulation results show that for the higher priority traffic better delay and jitter performance can be achieved compared with the lower priority traffic.
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| 5. |
- Chen, Jiajia, 1981-
(författare)
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Design, analysis and simultion for optical access and wide-area networks.
- 2009
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Due to the tremendous growth of traffic volume caused by both exponential increase of number of Internet users and continual emergence of new bandwidth demanding applications, high capacity networks are required in order to satisfactorily handle the extremely large amount of traffic. Hence, optical fiber communication is the key technology for the network infrastructure. This thesis addresses design, analysis and simulation of access and core networks targeting important research problems, which need to be tackled for the effective realization of next generation optical networks. Among different fiber access architectures, passive optical network (PON) is considered as the most promising alternative for the last mile connection due to its relatively low cost and resource efficiency. The inherent bursty nature of the user generated traffic results in dynamically changing bandwidth demand on per subscriber basis. In addition, access networks are required to support differentiated quality of service and accommodate multiple service providers. To address these problems we proposed three novel scheduling algorithms to efficiently realize dynamic bandwidth allocation in PON, along with guaranteeing both the priority and fairness of the differentiated services among multiple users and/or service providers. Meanwhile, because of the increasing significance of reliable access to network services, an efficient fault management mechanism needs to be provided in PON. In addition, access networks are very cost sensitive and the cost of protection should be kept as low as possible. Therefore, we proposed three novel cost-effective protection architectures keeping in mind that reliability requirement in access networks should be satisfied at the minimal cost. Regarding the optical core networks, replacing electronic routers with all-optical switching nodes can offer significant advantages in realizing high capacity networks. Because of the technological limitations for realizing all-optical nodes, the focus is put on the ingenious architecture design. Therefore, we contributed on novel switching node architectures for optical circuit and packet switching networks. Furthermore, we addressed different aspects of routing and wavelength assignment (RWA) problem, which is an important and hard task to be solved in wavelength routed networks. First, we proposed an approach based on the information summary protocol to reduce the large amount of control overhead needed for dissemination of the link state information in the case of adaptive routing. In addition, transparency in optical networks may cause vulnerability to physical layer attacks. To target this critical security related issue, we proposed an RWA solution to minimize the possible reachability of a jamming attack. Finally, in order to evaluate our ideas we developed two tailor-made simulators based on discrete event driven system for the detailed studies of PON and switched optical networks. Moreover, the proposed tabu search heuristic for our RWA solution was implemented in C++.
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| 6. |
- Chen, Jiajia, et al.
(författare)
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Dynamic routing based on information summary-LSA in WDM networks with wavelength conversion
- 2008
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Ingår i: Proceedings of 2008 10th Anniversary International Conference on Transparent Optical Networks, ICTON. - NEW YORK : IEEE. - 9781424426256 ; , s. 50-54
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- This Study investigates the use of information Summary (IS) applied to the advertised available resources to reduce the amount of link state advertisement (LSA) overhead, which is necessary to achieve distributed dynamic routing in WDM networks,. As illustrated in the Study, if carefully designed, the resulting IS-LSA protocol can significantly contain the size of the advertised data set without excessively affecting the network performance, i.e., the blocking probability caused by routing decisions based on incomplete link state information.
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| 7. |
- Chen, Jiajia, et al.
(författare)
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Novel Architectures of Asynchronous Optical Packet Switch
- 2007
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Ingår i: 33rd European Conference and Exhibition on Optical Communication ECOC’07, 2007. - : IEEE conference proceedings. - 9783800730421
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- We propose two asynchronous optical packet switch architectures, with efficient contention resolution based on controllable optical buffers and tunable wavelength converters TWCs. Providing a few shared optical buffers significantly boosts the performance obtained by TWCs.
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| 8. |
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| 9. |
- Cheng, Yuxin
(författare)
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Optical Interconnects for Next Generation Data Centers : Architecture Design and Resource Allocation
- 2019
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The current data center architectures based on blade servers and elec- tronic packet switches face several problems, e.g., limited resource utilization, high power consumption and cost, when handling the rapidly growing of data traffic. Optical networks offering ultra-high capacity and requiring low energy consumption are considered as a good option to address these problems. This thesis presents new data center architectures based on optical interconnects and transmissions, and evaluates performance by extensive simulations.The first main contribution of the thesis is to introduce a passive optical top-of-rack interconnect (POTORI) architecture. The data plane of POTORI mainly consists of passive components to interconnect the servers within the rack. Using the passive components makes it possible to significantly reduce power consumption while achieving high reliability in a cost-efficient way. In addition, the POTORI’s control plane is based on a centralized controller, which is responsible for coordinating the communications among the servers in the rack. A cycle-based medium access control (MAC) protocol and a dy- namic bandwidth allocation (DBA) algorithm are designed for the POTORI to efficiently manage the exchange of control messages and the data transmis- sion inside the rack. Simulation results show that under realistic DC traffic scenarios, the POTORI with the proposed DBA algorithm is able to achieve an average packet delay below 10 μs with the use of fast tunable optical transceivers.The second main contribution of the thesis is to investigate rack-scale disaggregated data center (DDC) architecture for improving resource utiliza- tion. In contrast to the traditional DC with blade servers that integrate various types of resources (e.g., central processing unit (CPU), memory) in a chassis, the rack-scale DDC contains fully decoupled resources held on differ- ent blades, referred to as resource blades. The resource blades are required to be interconnected within the rack by an ultra-high bandwidth optical in- terconnect through the optical interfaces (OIs). A resource allocation (RA) algorithm is proposed to efficiently schedule the resources in the DDC for virtual machine requests. Results show that with sufficient bandwidth on the OIs, the rack-scale DDC with the proposed RA algorithm can achieve 20% higher resource utilization and make 30% more revenue comparing to the traditional DC.
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| 10. |
- Cheng, Yuxin
(författare)
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Passive Optical Top-of-Rack Interconnect for Data Center Networks
- 2017
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Optical networks offering ultra-high capacity and low energy consumption per bit are considered as a good option to handle the rapidly growing traffic volume inside data center (DCs). However, most of the optical interconnect architectures proposed for DCs so far are mainly focused on the aggregation/core tiers of the data center networks (DCNs), while relying on the conventional top-of-rack (ToR) electronic packet switches (EPS) in the access tier. A large number of ToR switches in the current DCNs brings serious scalability limitations due to high cost and power consumption. Thus, it is important to investigate and evaluate new optical interconnects tailored for the access tier of the DCNs.We propose and evaluate a passive optical ToR interconnect (POTORI) architecture for the access tier. The data plane of the POTORI consists mainly of passive components to interconnect the servers within the rack as well as the interfaces toward the aggregation/core tiers. Using the passive components makes it possible to significantly reduce power consumption while achieving high reliability in a cost-efficient way.Meanwhile, our proposed POTORI’s control plane is based on a centralized rack controller, which is responsible for coordinating the communications among the servers in the rack. It can be reconfigured by software-defined networking (SDN) operation. A cycle-based medium access control (MAC) protocol and a dynamic bandwidth allocation (DBA) algorithm are designed for the POTORI to efficiently manage the exchange of control messages and the data transmission inside the rack.Simulation results show that under realistic DC traffic scenarios, the POTORI with the proposed DBA algorithm is able to achieve an average packet delay below 10 μs with the use of fast tunable optical transceivers. Moreover, we further quantify the impact of different network configuration parameters on the average packet delay.
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