Multiprotocol Label Switching Networks Research Articles

P2MP MPLS-Based Hierarchical Service Management System

This paper proposes a point-to-multipoint (P2MP) Multi-Protocol Label Switching (MPLS) based hierarchical service management system. Traditionally, general management systems deployed in some service providers control MPLS Label Switched Paths (LSPs) (e.g., RSVP-TE and LDP) and services (e.g., L2VPN, L3VPN and IP) separately. In order for dedicated management systems for MPLS LSPs and services to cooperate with each other automatically, a hierarchical service management system has been proposed with the main focus on point-to-point (P2P) TE LSPs in MPLS path management. In the case where P2MP TE LSPs and services are deployed in MPLS networks, the dedicated management systems for P2MP TE LSPs and services must work together automatically. Therefore, this paper proposes a new algorithm that uses a correlation between P2MP TE LSPs and multicast VPN services based on a P2MP MPLS-based hierarchical service management architecture. Also, the capacity and performance of the proposed algorithm are evaluated by simulations, which are actually based on certain real MPLS production networks, and are compared to that of the algorithm for P2P TE LSPs. Results show this system is very scalable within real MPLS production networks. This system, with the automatic correlation, appears to be deployable in real MPLS production networks.

Security analysis of RSVP-TE signaling in MPLS networks

Multiprotocol label switching (MPLS) is one of the fastest growing telecommunications infrastructure technologies. MPLS provides OSI layer 2 switching speed coupled with layer 3 addressing, and supports multiple service models and sophisticated traffic management. Several telecommunications companies have made massive investments in MPLS technology. Indeed, within a few years, a major portion of global data, voice and video traffic is expected to travel over MPLS network cores. This paper examines the security issues related to the RSVP-TE signaling protocol, which is vital to creating and managing the high-speed paths used by MPLS traffic. Our analysis has revealed several exploits–ranging from network enumeration to denial-of-service attacks–that can significantly impact MPLS networks. The exploits are discussed in detail along with proposed mitigation strategies.

Delay-margin based traffic engineering for MPLS-DiffServ networks

This paper presents a delay-margin based traffic engineering (TE) approach to provide end-to-end quality of service (QoS) in multi-protocol label switching (MPLS) networks using differentiated services (DiffServ) at the link level. The TE, including delay, class, and route assignments, is formulated as a nonlinear optimization problem reflecting the inter-class and inter-link dependency introduced by DiffServ and end-to-end QoS requirements. Three algorithms are used to provide a solution to the problem: The first two, centralized offline route configuration and link-class delay assignment, operate in the convex areas of the feasible region to consecutively reduce the objective function using a per-link per-class decomposition of the objective function gradient. The third one is a heuristic that promotes/demotes connections at different links in order to deal with concave areas that may be produced by a trunk route usage of more than one class on a given link. Approximations of the three algorithms suitable for on-line distributed TE operation are also derived. Simulation is used to show that proposed approach can increase the number of users while maintaining end-to-end QoS requirements.

Joint routing and admission control problem under statistical delay and jitter constraints in MPLS networks

Admission control algorithms are crucial for ensuring a near optimal resource allocation while guaranteeing the required Quality of Service (QoS) constraints. In this paper, a new routing and Admission Control mechanism in multi-protocol label switching (MPLS) based networks is proposed. The proposed mechanism relies on the packets’ delay distributions that are empirically built on every link, to make adequate admission decisions. As a new connection request arrives, the admission control mechanism computes a feasible path, satisfying the connection’s statistical QoS constraints (the maximum end-to-end delay, jitter and the QoS violation probability). For that, we formulate this problem as an Integer Linear Programming (ILP) model that is solved to optimality using the CPLEX mathematical programming tool for real-size networks. Simulation results show that the new admission control mechanism allows for low blocking rates while statistically satisfying the QoS constraints for both the new and the ongoing connections.

On optimal computation of MPLS label binding for multipoint-to-point connections

Most network operators have considered reducing Label Switched Routers (LSR) label spaces (i.e. the number of labels that can be used) as a means of simplifying management of underlaying Virtual Private Networks (VPNs) and, hence, reducing operational expenditure (OPEX). This letter discusses the problem of reducing the label spaces in Multiprotocol Label Switched (MPLS) networks using label merging - better known as MultiPoint-to-Point (MP2P) connections. Because of its origins in IP, MP2P connections have been considered to have tree- shapes with Label Switched Paths (LSP) as branches. Due to this fact, previous works by many authors affirm that the problem of minimizing the label space using MP2P in MPLS - the Merging Problem - cannot be solved optimally with a polynomial algorithm (NP-complete), since it involves a hard- decision problem. However, in this letter, the Merging Problem is analyzed, from the perspective of MPLS, and it is deduced that tree-shapes in MP2P connections are irrelevant. By overriding this tree-shape consideration, it is possible to perform label merging in polynomial time. Based on how MPLS signaling works, this letter proposes an algorithm to compute the minimum number of labels using label merging: the Full Label Merging algorithm. As conclusion, we reclassify the Merging Problem as Polynomial-solvable, instead of NP-complete. In addition, simulation experiments confirm that without the tree-branch selection problem, more labels can be reduced.

Rerouting tunnels for MPLS network resource optimization

Abstract In Multi-Protocol Label Switching (MPLS) networks, traffic demands can be routed along tunnels called Label Switched Paths (LSPs). A tunnel is characterized by a path in the network and a reserved bandwidth. These tunnels can be created and deleted dynamically, depending on traffic demand arrivals or departures. After several operations of this type, the network resource utilization can be unsatisfactory, with congestion or too long routing paths for instance. One way to improve it is to reroute tunnels; the rerouting process depends on the LSP Quality of Service (QoS) requirements. Three levels of QoS are considered, with three associated types of LSPs. A global rerouting framework is proposed, which enables us to consider independently each type of LSP. Then, mathematical models are introduced and analyzed. A focus is made on complexity analysis and optimal resolution of these problems. Finally, some numerical results illustrate the theoretical analysis.

Using policy-based MPLS management architecture to improve QoS on IP network

Multi-Protocol Label Switching (MPLS) is in the process of standardization by the Internet Engineering Task Force (IETF). It is regarded as a technology for traffic engineering and QoS in IP-networks. We proposed an IETF Policy-based Network Management Framework and policies with MPLS specific classes. It uses a three-level policy architecture, which includes managing on device, network, and service level using policies for supporting Inter-serve and Diff-serve based end-to-end QoS in the Internet. A prototyping of policy-based management system for MPLS Traffic Engineering is operating on MPLS network elements. Several experiments illustrate the efficiency and feasibility in this architecture. The results show it can reduce the time of the setup of MPLS traffic engineering tunnel over hops and MPLS traffic engineering tunnel deletion. The proposed integrated policy based management architecture will allow network service providers to offer both quantitative and qualitative services while optimizing the use of underlying network resources.

Loop-free traffic engineering with path protection in MPLS VPNs

In this paper we present a new approach for VPN (virtual private network) traffic engineering with path protection in Multiprotocol Label Switching networks carrying QoS and best effort traffic. Our approach eliminates the path cycles, a problem often encountered in link-based traffic engineering methods. It also allows for control of the maximum path length and the size of the label space in each label switch router. We consider off-line computation of the working and backup paths using a link-based approach. Two cases of 1+1 and 1:1 path protection are considered. Numerical results are presented to show the efficacy of the algorithm in calculating link-disjoint and node-disjoint primary and backup paths for the QoS traffic.

Mobility label based network: Mobility support in label switched networks with multi-protocol BGP

To support mobility the network control plane is required to detect changes in the mobile node's location and distribute the new location information throughout the network thus enabling the forwarding plane to deliver traffic in an optimal manner. The network responsiveness to the mobile node movements can be generally thought of as the time elapsed between the moment the node's location in the network has changed and the moment the reception of packets in the new location has resumed. This paper outlines an approach to handling the user mobility at the network layer in the context of multi-protocol label switched networks (MPLS). This new approach does not rely on the existing IP mobility management protocols such as Mobile IP and is instead based on the combination of multi-protocol BGP (MP-BGP) and MPLS. This paper proposes to introduce new protocol elements to MP-BGP to achieve mobility label distribution at the network control plane and the optimal packet delivery to the mobile node by the network forwarding plane using MPLS regardless of the IP protocol addressing and the associated logical network topology.

Enhanced Variable Splitting Ratio Algorithm for Effective Load Balancing in MPLS Networks

Fast load balancing is of the highest importance to utilize the resources effectively and improve the performance of the Multi Protocol Label Switching (MPLS) enabled Internet Protocol (IP) networks. Load balancing splits a part of traffic called splitting ratio from the maximum loaded path in to minimum loaded path. One very strong constrain in balancing the load is the tradeoff between the delay to reach the balanced state and the oscillations generated by splitting the load at the balanced state. To avoid oscillations, the splitting ratio must be kept small. However, smaller splitting ratio takes more number of iterations to balance the load. To overcome this constrain in this study, an enhanced variable splitting ratio based algorithm was proposed to reduce the delay without oscillations. The splitting ratio was varied depending upon the difference between the maximum path load and the minimum path load. A numerical method was used to evaluate the performance of the algorithm and it was applied to a test network. The simulation results showed that the number of iterations required to balance the load was decreased significantly with out oscillations.

TROP: A Novel Approximate Link-State Dissemination Framework For Dynamic Survivable Routing in MPLS Networks

In this paper, a novel approximate link-state dissemination framework, called TROP, is proposed for shared backup path protection (SBPP) in multiprotocol label switching (MPLS) networks. While performing dynamic explicit survivable routing in a distributed environment, link-state dissemination may cause a nontrivial signaling overhead in the process of exploring spare resource sharing among individual backup label switched paths (LSPs). Several previously reported studies have tackled this problem by initiating a compromise between the amount of dissemination and the achievable extent of resource sharing. The paper first summarizes the previously reported schemes into a compact and general link-state dissemination framework by way of singular value decomposition (SVD). To improve the accuracy of the matrix reconstruction and to eliminate the overestimation of the sharable spare capacity along each link, a novel SVD approach based on the min-plus algebra (also called tropical semirings) is introduced. Simulation results show that the proposed schemes can achieve a lower blocking probability than that by all the other counterpart schemes while taking the same complexity of link-state dissemination. This great advantage is gained at the expense of a longer computation time for solving a linear program (LP) in each dissemination cycle at the core nodes. We also consider the stale link-state phenomena that may cause imprecision in the routing information at the ingress nodes due to the delay in the periodic/event-driven link-state update message advertisement.

Multi-layer MPLS network design: The impact of statistical multiplexing

The possibility of adding multi protocol label switching (MPLS) support to transport networks is considered an important opportunity by telecom carriers that want to add packet services and applications to their networks. However, the question arises whether it is suitable to have MPLS nodes just at the edge of the network to collect packet traffic from users, or to introduce also MPLS facilities on a subset of the core nodes in order to exploit packet switching flexibility and multiplexing, thus inducing a better bandwidth allocation . In this paper, we propose a mathematical programming model for the design of two-layer networks where MPLS is considered on top of transport networks (SDH or WDM depending on required link speed). Our models take into account the tradeoff between the cost of adding MPLS support in the core nodes and the savings in the link bandwidth allocation due to the statistical multiplexing and the traffic grooming effects induced by MPLS nodes. The traffic matrix specifies for each point-to-point request a pair of values: a mean traffic value and an additional one. Using this traffic model, the effect of statistical multiplexing on a link allows to allocate a capacity equal to the sum of all the mean values of the traffic demands routed on the link and only the highest additional one. We propose a path-based Mixed Integer Programming (MIP) model for the problem of optimizing the number and location of MPLS nodes in the network and the link capacities. We apply Lagrangian relaxation to this model and use the subgradient method to obtain a lower bound of the network cost. As the number of path variables used to model the routing grows exponentially with the graph size, we use an initially limited number of variables and a column generation approach. We also introduce a heuristic approach to get a good feasible solution. Computational results are reported for small size and real-world instances.

Automatic Bandwidth Adjustment for Content Distribution in MPLS Networks

Aggregates of real‐time traffic may experience changes in their statistical characteristics often manifesting non stationary behavior. In multi protocol label switching (MPLS) networks this type of the traffic is assigned constant amount of resources. This may result in ineffective usage of resources when the load is below than expected or inappropriate performance when the load is higher. In this paper we propose new algorithm for dynamic resource adaptation to temporarily changing traffic conditions. Assuming that network nodes may reallocate resources on‐demand using automatic bandwidth adjustment capability of MPLS framework, the proposed algorithm, implemented at ingress MPLS nodes, dynamically decides which amount of resources is currently sufficient to handle arriving traffic with given performance metrics. This decision is then communicated to interior MPLS nodes along the label switched path. As a basic tool of the algorithm we use change‐point statistical test that signals time instants at which statistical characteristics of traffic aggregates change. The major advantage of the proposed approach is that it is fully autonomous, that is, network nodes do not need any support from hosts in terms of resource reservation requests. The proposed algorithm is well suited for traffic patterns experiencing high variability, especially, for non stationary type of the traffic.

Routing and admission control with multiconstrained end-to-end quality of service in MPLS networks

Multiprotocol label switching (MPLS) networks require dynamic flow admission control to guarantee end-to-end quality of service (QoS) for each Internet protocol (IP) traffic flow. In this paper, we propose to tackle the joint routing and admission control problem for the IP traffic flows in MPLS networks with multiconstrained end-to-end QoS. We propose a mathematical programming model for this problem that includes end-to-end delay and packet loss constraints. These constraints are imposed not only for the new traffic flow, but also for all already admitted flows in the network. Three objective functions are proposed and analyzed: the end-to-end delay, the end-to-end packet loss and the cost of the path used by the new flow. Numerical results show that considering end-to-end delay and packet loss constraints for all flows has a small impact on the flow blocking rate, but improves significantly the end-to-end QoS parameters. Moreover, the proposed approach is able to make the decision to admit or not a new flow in less than 270 ms of computational time.

A meta-model for multiobjective routing in MPLS networks

MPLS (Multiprotocol Label Switching) enables the utilisation of explicit routes and other advanced routing mechanisms in multiservice packet networks, capable of dealing with multiple and heterogeneous QoS (Quality of Service) parameters. Firstly the paper presents a discussion of conceptual and methodological issues raised by multiobjective routing optimisation models for MPLS networks. The major contribution is the proposal of a multiobjective routing optimisation framework for MPLS networks. The major features of this modelling framework are: the formulation of a three-level hierarchical routing optimisation problem including network and service performance objectives, the inclusion of fairness objectives in the different levels of optimisation and a two-level stochastic representation of the traffic in the network (traffic flow and packet stream levels). A variant of the general model for two classes of traffic flows, QoS traffic and Best Effort traffic, is also presented. Finally a stochastic teletraffic modelling approach, underlying the optimisation model, is fully described.

Hierarchical wireless mobile MPLS mechanism using foreign tracking agent based on M/G/1 with capacity c queueing model

Within the MultiProtocol Label Switching (MPLS) network, packets with the same forwarding equivalent class can easily be identified by their attached label value. The cross-layer topology associates with access protocol and IP mobility agents. The necessity of agent discovery is reduced and an approach to enhance handoff efficiency proposed. This efficient handoff scheme is performed by a foreign tracking agent (FTA) that plays a role as an administrator of a hierarchy that consists of some foreign agents (FAs) to localise the routing operation of forwarded packets. To analyse the performance of a hierarchical mobile MPLS network, the system is modelled as an M/G/1 system with capacity c, where c represents the number of FAs that can be administered for an FTA. The mean delay time of the FTA to process the forwarding of packets is analysed using M/M/1 with capacity c queueing model. The minimum number of FAs that can be administered for an FTA is derived to improve network performance by minimising mean delay time.

Bandwidth Management for Supporting Differentiated Service Aware Traffic Engineering

This paper presents a bandwidth management framework for the support of differentiated-service-aware traffic engineering (DS-TE) in multiprotocol label switching (MPLS) networks. Our bandwidth management framework contains both bandwidth allocation and preemption mechanisms in which the link bandwidth is managed in two dimensions: class type (CT) and preemption priority. We put forward a Max-Min bandwidth constraint model in which we propose a novel "use it or lend it" strategy. The new model is able to guarantee a minimum bandwidth for each CT without causing resource fragmentation. Furthermore, we design three new bandwidth preemption algorithms for three bandwidth constraint models, respectively. An extensive simulation study is carried out to evaluate the effectiveness of the bandwidth constraint models and preemption algorithms. When compared with the existing constraint models and preemption rules, the proposed Max-Min constraint model and preemption algorithms improve not only bandwidth efficiency, but also robustness and fairness. They achieve significant performance improvement for the well-behaving traffic classes in terms of bandwidth utilization and bandwidth blocking and preemption probability. We also provide guidelines for selecting different DS-TE bandwidth management mechanisms.

Reliable Multipath Provisioning for High-Capacity Backbone Mesh Networks

We investigate reliable multipath provisioning of traffic in high-capacity backbone mesh networks, e.g., next-generation SONET/SDH networks supporting virtual concatenation (VCAT). VCAT enables a connection to be inversely multiplexed on to multiple paths, a feature that may lead to significantly improved performance over conventional single-path provisioning. Other mesh networks such as those employing optical wavelength-division multiplexing (WDM) and multiprotocol label switching (MPLS) can also benefit from this multipath provisioning approach. We propose effective multipath bandwidth as the metric to provision a connection while satisfying its reliability requirements (measured in terms of availability). We demonstrate that effective multipath bandwidth provides more flexibility and lower blocking probability without the cost and the complexity associated with traditional protection schemes developed for optical WDM and MPLS networks. We also investigate the practical problem of provisioning effective multipath bandwidth with cost constraints. We analyze the tractability of the problem and present a heuristic which results in significantly reduced number of blocked connections due to cost constraints.

QoS provisioning by EFuNNs-based handoff planning in cellular MPLS networks

In recent years, Multi Protocol Label Switching (MPLS) has been considered as the preeminent technology to incur Quality of Service (QoS) for integrated services. However, in wireless networks the remotes mobility endangers resource management procedure and QoS provisioning. In this paper we propose a new location prediction method based on Evolving Fuzzy Neural Networks (EFuNNs), to manage Label Switched Paths (LSPs) in an MPLS domain. The proposed predictor employs geographical characteristics of underlying area and the movement history of a remote, to produce a set of confidence ratios as the output. That set is considered as a criterion for establishing and managing LSPs so that QoS preserved. The simulation results have shown superior performance in terms of prediction accuracy and utilization improvement for the proposed methods.

A Scalable Path Protection Mechanism for Guaranteed Network Reliability Under Multiple Failures

We propose two versions of Link Failure Probability (LFP) based backup resource sharing algorithms, namely LFP based First-Fit algorithm, and LFP based Best-Fit algorithm for Generalized Multi-Protocol Label Switching networks. Customers' availability requirements are met by adjusting the availability of the protection paths with different sharing options. Information required for calculating the availability of both the working, and protection paths can be collected along the specific working, and protection paths, thus avoiding the requirement for flooding. This makes our algorithms scalable for a large network. Our algorithms work consistently against both single, and multiple failures. Furthermore, we propose extensions for the existing signaling protocols to demonstrate that our proposed algorithms require minimum changes to the existing protocols. Simulation results show that our proposal performs better than the conventional Dedicated Path Protection schemes in terms of Call Acceptance Rate, and Total Bandwidth Consumption. Finally, by comparing simulation results to analytical results for a simplified network, we provide some insights into the correctness, and efficiency of our proposed algorithms