Differential Delay Constraint Research Articles

A Method of Optical Grooming Based on Dynamic Multicast Capable of Adaptive Splitting Under Differential Delay Constraint

Abstract Aiming at the problem of energy efficient transmission for multiple paths under differential delay constraint, we propose a method of optical grooming based on dynamic splitting under differential delay constraint algorithm (OG-DSDA) for optical networks. When a multicast demand cannot be groomed due to the bandwidth fragment, the method constructs two types of logic light-tree sets according to the differential delay constraint between source node and destinations. In order to reduce the network link costs caused by too many split parts, the method gives high priority to the first type logic light-trees with the maximum available bandwidth to meet the requirement. When the bandwidth of first type logic light-tree is insufficient for all sub-requests, the rest of sub-demands is adaptively groomed into a light-tree in second set of light-trees with the lower power consumption. Simulation results show that the proposed method can effectively decrease the network blocking probability and reduce network’s energy consumption.

Minimizing Blocking Probability in Elastic Optical Networks by Varying the Bandwidth Granularity Based on Optical Path Fragmentation

Elastic optical networks (EONs) based on orthogonal frequency-division multiplexing (OFDM) are considered a promising solution for the next optical network’s generation. These networks make it possible to choose an adequate portion of the available spectrum to satisfy the requested capacity. In this paper, we consider the impact of spectrum fragmentation along the optical single/multipath routing transmission on the efficiency of the EONs. This involves reducing the fragmentation effects by dynamically updating and controlling the minimum bandwidth allocation granularity (ɡ). We adopt linear and nonlinear dynamic mechanisms, which are denoted as LDAɡ and NLDAɡ, respectively, to choose proper bandwidth granularities that are proportional to the optical link/path bandwidth fragmentation status. In order to avoid either splitting the capacity request over many routing paths, which would increase the management complexity, or encouraging single path transmission, the proposed schemes aim to choose a proper bandwidth allocation granularity (ɡ) for a predefined set of suggested values. Simulation results show that varying the bandwidth granularity based on the optical path fragmentation status can offer an improved performance over fixed granularity with respect to the bandwidth blocking probability, the number of path splitting actions, the throughput, and the differential delay constraint issue in terms of: the network bandwidth utilization and multipath distribution.

Minimizing Blocking Probability in Elastic Optical Networks by Varying the Bandwidth Granularity Based on Optical Path Fragmentation

Elastic optical networks (EONs) based on orthogonal frequency-division multiplexing (OFDM) are considered a promising solution for the next optical network’s generation. It basically makes it possible to choose an adequate portion of the available spectrum to satisfy the requested capacity. In this paper, we consider the impact of spectrum fragmentation along the optical single/multipath routing transmission on the efficiency of the EONs. This involves reducing the fragmentation effects by dynamically updating and controlling the minimum bandwidth allocation granularity (g).We adopt linear and nonlinear dynamic mechanisms, which are denoted as LDAEi and NLDAEi, respectively, to choose proper band width granularities that are proportional to the optical link/path bandwidth fragmentation status. In order to avoid neither splitting the capacity request over many routing paths, which would increase the management complexity, nor encouraging single path transmission, the proposed schemes aim to choose a proper bandwidth allocation granularity (g) of a predefined set of suggested values. Simulation results show that varying the bandwidth granularity based on the optical path fragmentation status can offer improved performance over fixed granularity with respect to the bandwidth blocking probability, the number of path splitting, the throughput, and differential delay constraint issue in terms of: the network bandwidth utilization and multipath distribution.

Multi-flow virtual concatenation triggered by path cascading degree in Flexi-Grid optical networks

The Flexi-Grid optical networks can elastically allocate spectrum tailored for various bandwidth requirements. In the flexible architecture, routing and spectrum allocation (RSA) is the key problem is to assign spectral resources to accommodate traffic demands. However, spectrum continuity and contiguity constraints in Flexi-Grid optical networks may cause the network fragmentation issue and lead to poor spectrum utilization. In this paper, different from defragmentation methods, we propose multi-flow virtual concatenation (MFVC) in Flexi-Grid optical networks. MFVC can utilize spectral fragments effectively and decrease blocking probability without influencing the already existing active services or wasting additional spectrum resources. We also analyze the feasibility of MFVC and present a MFVC-enabled transponder and control model implementation. For estimating the distribution and size of available fragments on a path in advance, a split-multi-flow RSA heuristic algorithm (SMF) is proposed by introducing path cascading degree (PCD) based triggered mechanism according to the proposed model. Additionally, resource assignment scheme, guard band size, maximum number of split-flow and differential delay constraint are also considered into MFVC and the performances of the proposed algorithm can be demonstrated to improve the spectral utilization and greatly decrease blocking probability through extensive simulations.

Design QoS-Aware Multi-Path Provisioning Strategies for Efficient Cloud-Assisted SVC Video Streaming to Heterogeneous Clients

We layout a network infrastructure that leverages the storage and computing power of a cloud residing in the core for collecting network status and computing multi-path scalable video coding (SVC) streaming provisioning strategies. Therefore, in addition to its conventional tasks in the application layer, the cloud also gets involved in the network layer for the optimization of routing and forwarding. We call this scheme as cloud-assisted SVC streaming, and use it to further improve the performance of SVC streaming by using close cooperation between cloud and network. Compared to source-routing based provisioning, the cloud-assisted scheme can provide more cost-effective provisioning strategies by utilizing better knowledge of network environment together with more powerful computation power. We then propose several multi-path provisioning algorithms for cloud-assisted SVC streaming in heterogeneous networks. To the best of our knowledge, these are the first proposals to work on the problem of adaptive multi-path SVC streaming under the bandwidth, delay and differential delay constraints. Our design of the provisioning algorithms starts from an approach that is based on Max Flow and an Auxiliary Graph. Several extensions are then made based on this approach to address the situations such as provisioning from multiple sources and provisioning in dynamic network environments with rapid background traffic fluctuations. Simulations in both static and dynamic network environments show that the proposed algorithms can achieve effective performance improvements in terms of request blocking probability, bandwidth utilization, packet delay, packet loss rate, and video playback quality.

Dynamic Multi-Path Service Provisioning under Differential Delay Constraint in Elastic Optical Networks

Optical orthogonal frequency-division multiplexing (O-OFDM) technology has the elastic feature of allocating spectrum resources based on subcarrier slots with bandwidths at a few GHz or even narrower. This feature enables us to utilize link capacity more efficiently by splitting a connection's traffic over multiple routing paths. In this paper, we propose a novel dynamic multi-path provisioning algorithm for O-OFDM based elastic optical networks. The algorithm tries to set up dynamic connections with single-path routing in a best-effort manner. When a connection cannot be served with a single routing path, the algorithm uses an auxiliary-graph based approach to calculate a multi-path provisioning scheme based on two parameters, i.e., the differential delay upper-bound and the bandwidth allocation granularity. Simulation results indicate that compared with several existing single-path provisioning algorithms, the proposed algorithm provides lower bandwidth blocking probability and achieves 10-18% improvement on average network throughput.

Survivable Multipath Provisioning With Differential Delay Constraint in Telecom Mesh Networks

Survivability is a critical concern in modern telecom mesh networks because the failure of a network element may cause tremendous data and revenue loss in such networks using high-capacity optical fibers employing wavelength-division multiplexing (WDM). Multipath provisioning is a key feature of next-generation SONET/SDH networks (which can be used on top of optical WDM), and they can support virtual concatenation (VCAT); thus, multipath provisioning can significantly outperform single-path provisioning in resource efficiency, service resilience, and flexibility. However, in multipath provisioning, differential delay is an important constraint that should be considered. We investigate survivability of service paths based on differential-delay constraint (DDC) and multipath provisioning together in telecom backbone mesh networks. We propose the Shared Protection of the Largest Individual Traversed link (SPLIT) method for survivable multipath provisioning and present a DDC-based algorithm for multipath routing subject to DDC. We also compare the DDC-based algorithm with the K shortest link-disjoint paths (KDP) algorithm, using SPLIT, under dynamic service requests. We find that exploiting link-disjoint paths is very efficient for survivable multipath provisioning, and our algorithm is resource-efficient, has low signaling overhead, and has fast fault recovery for survivable multipath provisioning with DDC. For a 5-ms DDC, our algorithm can decrease the bandwidth blocking ratio (BBR) significantly in typical U.S. backbone networks.

Survivable Multipath Traffic Grooming in Telecom Mesh Networks With Inverse Multiplexing

We investigate the survivable traffic grooming problem with inverse multiplexing in telecommunication mesh networks employing next-generation SONET/SDH and WDM. With the support of virtual concatenation, a connection of any bandwidth can be provisioned as several subconnections (i.e., inverse multiplexed) over diverse paths. Therefore, it is important to efficiently groom and protect these low-speed subconnections onto high-capacity wavelength channels, considering the typical constraints. We propose and investigate the characteristics of survivable multipath traffic grooming with protection-at-connection and protection-at-lightpath levels for grooming connections with shared pro- tection, subject to the constraints of the inverse-multiplexing factor, differential-delay constraint, and grooming ports. Since this problem is NP-complete, we propose effective heuristics using a novel analytical model. Our results show that (1) the network performance, in metrics of bandwidth blocking ratio and resource overbuild, can be notably improved by exploiting the inverse-multiplexing capability, (2) tight constraints have negative impact on performance, (3) protection-at-connection performs better in most cases of multipath provisioning when the constraints are not too tight, and (4) protection-at-lightpath achieves better performance when the number of grooming ports is moderate or small.

Adaptive Reliable Multipath Provisioning in Survivable WDM Mesh Networks

We investigate the problem of adaptive reliable multipath provisioning in next-generation backbone mesh networks employing optical wavelength-division multiplexing (WDM) and channelization techniques such as synchronous optical network/synchronous digital hierarchy (SONET/SDH) and supporting virtual concatenation (VCAT). VCAT enables multipath provisioning, but also introduces differential delay at destination nodes. How to guarantee service availability, using multipath provisioning, and meet the differential-delay constraint (DDC) is an important problem. We introduce the notation M:N(m) for multipath provisioning where a service path for a connection is set up with M primary paths and N backup paths, where each path has a fraction of the bandwidth of the connection, and (m) in this notation denotes “multipath.” With M:N(m) provisioning schemes, we develop an analytical model to analyze the end-to-end connection availability for the full bandwidth request. We propose two types of bandwidth migration methods, which can be implemented by a link-capacity adjustment scheme (LCAS) protocol of next-generation SONET/SDH, to optimize resource usage. Based on the M:N(m) analytical model, we develop an adaptive heuristic algorithm to provision a connection subject to the DDC while satisfying its service-level agreement (SLA). We show that, for end-to-end connection-availability-guaranteed service, multipath provisioning can achieve much better network performance than traditional single-path provisioning. With bandwidth migration, we can further improve multipath provisioning performance.

Performance study of IP and SONET grooming in optical WDM mesh networks

We study the problem of IP traffic grooming in optical wavelength-division-multiplexed (WDM) mesh networks. Two different grooming architectures are considered: (i) IP/MPLS grooming, and (ii) SONET grooming. The IP/MPLS grooming approach provides a fine level of grooming granularity realized via software-based implementations but has router-processing-related bottlenecks. The SONET grooming approach is realized in dedicated hardware, but it is more expensive and typically offers limited grooming granularity choices. We also consider multipath routing as used in SONET virtual concatenation techniques, and we study the impact of the differential delay constraint. A detailed comparison of the different grooming options in terms of blocking probability, lightpath utilization, and survivability issues is presented. The simulation analysis helps quantify the improved performance of finer granularity grooming approaches over the coarser SONET-based approaches.