This paper is devoted to dimensioning and optimizing optical buffers for asynchronous, variable length packets in GMPLS-based WDM optical packet-switched networks, which aims to lower network congestion and increase utilization efficiency of optical buffers. In GMPLS-based WDM optical packet-switched networks, the critical issue is how to improve network flexibility and limit network congestion. Comparing to optical buffers with a single operating wavelength, WDM optical buffers in an optical packet switch (OPS) have demonstrated superior performance in solving congestion, which perform buffering by exploiting both time and wavelength dimensions. However, the realistic buffering capacity of optical fiber-delay-line (FDLs) buffers is currently limited. Hence, the algorithm for wavelength sharing and design of the optimal value of the basic time unit of the FDLs in WDM optical buffers are indispensable to shorten FDLs and put OPS into practice. In this paper, the algorithm for wavelength sharing among multiple connections is proposed, which aims to minimize congestion and shorten the queue length. And, in this scenario, the optimal value of the basic time unit of the FDLs is designed. Finally, the proposed algorithm is compared with others in terms of performance.
The main purpose of this paper is to propose mobile IP network architecture based on dense wavelength-division multiplexing (DWDM), with GMPLS as a common control plane of the optical layer. A novel probability-based wavelength assignment (PWA) scheme for facilitating handoff in the proposed GMPLS-based mobile IP network is also presented. This paper studies the effects of network mobility and handoff path rerouting on the wavelength assignment scheme in a GMPLS-based mobile IP network. In order to support the same quality of service (QoS) for mobile services when handoff occurs, it is preferable to use the same wavelength in the newly established partial label switched path (LSP). In the proposed PWA scheme, when a mobile router (MR) begins to establish a new connection with the correspondent node, a wavelength is assigned based on the vacant probability of every wavelength in the new partial LSP after handoff. We use M/M/1(0) queue to model the dynamic traffic in a GMPLS-based mobile IP network and derive the close-form expression of wavelength vacant probability.
With the tremendous growth of broadband IP services, the impact of bandwidth bottleneck in access network becomes more prominent and largely restricts the network carriers to provide satisfied services for subscribers. Thus, a new access network with sufficient bandwidth resources and efficient network resource management must be designed. In this paper, a Generalized MPLS (GMPLS) and EPON-based optical access network is proposed to provide end-to-end quality-of-service (QoS) guarantee for broadband IP services. The proposed network architecture is presented and the Label Switched Path (LSP) setup procedure is developed. In the proposed access network, GMPLS is used to manage network resources dynamically and to conduct traffic engineering. In addition, an efficient dynamic bandwidth allocation algorithm is designed to accommodate bursty IP traffic and improve bandwidth utilization in the proposed network. The performance analyses show that under the same network load the proposed scheme has lower average packet delay and shorter queue length than current schemes.
In future GMPLS-based wavelength-routed networks (WRNs), lightpaths are set up or torn down dynamically. Blocking probabilities of on-demand requests are an important performance measure. However, the network average blocking probability only indicates the global performance of the network. Due to large resource requirements and wavelength continuity constraint, the blocking probabilities of longer-hop connections are usually much higher than those of shorter-hop connections. This problem is the so-called fairness problem. In this paper, a priority-based control is proposed to improve the fairness between different connections. Connections with high blocking probabilities are assigned high priorities and they are able to preempt low priority connections with a predetermined probability. Both theoretical analyses and simulations are given. It is shown that the proposed control not only improves the fairness, but also ensures that the average blocking probability is not degraded much. Hence, the performance of the GMPLS-based optical networks will be improved greatly.
In GMPLS-based networks, data is forwarded in manner of label switching on Label Switching Router (LSR). Ingress LSR must classify different IP flows into a set of Forwarding Equivalence Classes (FECs), which is a typical flow classification process. Ingress LSR will be the bottleneck of GMPLS-based networks if it could not provision fast flow classification. In this paper, we propose a novel fast flow classification scheme, coined Hierarchical Dividing Tree Scheme (HDTS), to improve the switching performance of ingress LSR in GMPLS-based networks. Four important advantages can be achieved by the proposed HDTS. First, the preprocess time in HDTS is reasonable. Second, fast FEC update is supported. Third, memory cost of HDTS is very low. Most important, the key factor that affects flow classification speed is not the number of FECs, but the depth of the search trees in HDTS. Theoretical analyses and simulations are conducted to evaluate performance of the proposed HDTS. Based on the analytical and experimental results, we can conclude that our HDTS improves the switching performance of ingress LSR greatly and is very practical for GMPLS-based networks due to its low cost.
The main purpose of this paper is to propose a novel bandwidth allocation scheme for facilitating quality of service (QoS) routing in mobile ad hoc networks (MANETs). In a MANET using time division multiple access (TDMA), each node communicates with its neighbors in the same time slot. In general, finding a route with the maximum end-to-end bandwidth subject to the constraint of collision-free transmission is an NP-complete problem. This paper proposed a sub-optimal solution to this problem. The solution is based on a centrally controlled bandwidth allocation scheme to properly assign the available time slots to each intermediate link. The advantage of our proposed scheme is that the resource utilization of MANET is maximized and the end-to-end QoS is guaranteed during the route establishment period. Performance analyses show that when using the proposed scheme with AODV to perform QoS routing, it achieves about 25% throughput higher than its best-effort counterpart if the node is moving at 5mps speed.
Provisioning Protection and Restoration (P&R) capability is a necessity in Generalized Multi-Protocol Label Switching (GMPLS) networks. Label Switched Path (LSP) segment-based recovery is an important P&R type. In this paper, three novel overlapped LSP segment selection schemes are proposed. The near-optimal set of overlapped LSP segments can be obtained by the proposed schemes, which have polynomial time complexity. Differences among the proposed schemes are discussed and compared. Performance comparisons between LSP segment recovery with the proposed schemes and end-to-end LSP recovery are conducted. The results show that the proposed schemes perform very well in LSP segment recovery. With the proposed schemes, the complexity of LSP segment recovery design is decreased considerably. Moreover, the proposed schemes provide flexible choices for GMPLS-based P&R techniques in terms of different failure recovery time and resource utilization constraints.
In this paper, we present a novel reliable MPEG-4 based packetisation scheme over UMTS (universal mobile telecommunications service) networks. Using this scheme, some lost crucial RTP packets can be delivered within a multiplex RTP packet. With the feedback of RTCP control packets, this paper presents a decision-making procedure by which we can calculate the number of the redundant packets in a multiplex packet during a RTCP interval, i.e., this procedure can precisely reflect current network congestion state dynamically. To support the proposed procedure, two conditions must be satisfied. The first one is the RTP packets loss constraint and the second one is the RTP packets delay limitation. Moreover, through investigating related RTP payload formats and FGS (fine granularity scalability) framework, we can deliver BL (MPEG-4 basic layer) data by the proposed scheme. EL (MPEG-4 enhancement layer) data will be delivered as the best-effort traffic. Finally, simulations over UMTS networks demonstrate the validity of this scheme. Further comparison between this scheme and the traditional schemes also is done. The results show that our scheme improves QoS of services significantly.
In next-generation IP over WDM networks, lightpaths are set up or torn down dynamically. Traditionally, OSPF in IP layer and OSPF-TE in optical layer disseminate routing information independently. Obviously, this 2-layer routing mechanism is complex and O&M cost is high. Furthermore, in a dynamic environment, both OSPF-TE and OSPF have very heavy control overheads when lightpaths change frequently. In this paper, an integrated routing protocol is proposed. The link state information of both IP layer and optical layer is disseminated simultaneously using the same routing protocol messages. The proposed protocol also advertises wavelength availability information if necessary in order to reduce the blocking probability of routing and wavelength assignment (RWA) algorithm. This proposed integrated protocol is very simple. Furthermore, its control overhead can be reduced from several to about ten times. In addition, RWA's performance is also improved. Hence, the performance of the IP over WDM networks will be improved greatly and significantly.
Optical crossconnects (OXCs) are critical core for provisioning and restoration in mesh wavelength-division-multiplexing (WDM) networks. An increasingly urgent need for large-port-count OXCs severely challenges the current existing OXC technologies. To reduce the crosspoint complexity, we propose an architecture based on 2×2 switching fabrics by integrating the general symmetric (GS) architecture with Clos and Benes switching architectures together. Rearrangeably and strictly nonblocking structures are examined as well as the control algorithm of the rearrangeably nonblocking structure is studied. Then, we present two basic switching fabrics of the simples 2×2 bidirectional OXC utilizing 2D optical MEMS, one of which is used as the basic building block in our proposed architecture is studied. The resulted switch requires (N/2)×[log2(N/2)]×(log2N-1/2) micromirrors, while the switch based on GS architecture needs 2(N/2)2 micromirrors. It is very clear that our proposed architecture reduces the number of micromirrors greatly, especially when N is large. Moreover, theoretical analyses have shown that the resulted switch has the same insertion loss, lower power consumption, and better performance of port-to-port repeatability, comparing to the conventional crossbar switch.
Several recovery mechanisms are provided in Generalized Multi-Protocol Label Switching (GMPLS) networks to improve the network survivability. Future wired backbone networks will definitely be GMPLS-based, and GMPLS networks must provide an efficient recovery scheme to provision mobility-aware capabilities in wireless IP networks. The purpose of this paper is to propose a GMPLS-based recovery scheme for fast handoff in wireless IP networks. The
proposed scheme can establish new label switched path (LSP) rapidly by utilizing the backup resources when mobile node (MN) handoffs in wireless networks. Therefore, low handoff latency can be achieved. And, the resource utilization in GMPLS networks can be improved.
In this paper, a new Active Hierarchical Label Switching Router (AHLSR) architecture of MPLS is proposed for MPEG-4-based mobile multimedia IP-networks. The proposed architecture has two important modules, AHLSR Controller (AHLSRC) and AHLSR Protocol (AHLSRP). AHLSR conducts layer 2 switching and layer 3 routing independently; it supports multi-resolution functionality. Each VOL flow entering AHLSR is segmented into several VOL sub-flows according to resolutions. And, AHLSRC manages both dedicated and unused channels. The AHLSR can achieve better performance without wasting communications bandwidth in MPEG-4-based mobile multimedia communications