A Survey on the Path Computation Element (PCE) Architecture

Quality of Service-enabled applications and services rely on Traffic Engineering-based (TE) Label Switched Paths (LSP) established in core networks and controlled by the GMPLS control plane. Path computation process is crucial to achieve the desired TE objective. Its actual effectiveness depends on a number of factors. Mechanisms utilized to update topology and TE information, as well as the latency between path computation and resource reservation, which is typically distributed, may affect path computation efficiency. Moreover, TE visibility is limited in many network scenarios, such as multi-layer, multi-domain and multi-carrier networks, and it may negatively impact resource utilization. The Internet Engineering Task Force (IETF) has promoted the Path Computation Element (PCE) architecture, proposing a dedicated network entity devoted to path computation process. The PCE represents a flexible instrument to overcome visibility and distributed provisioning inefficiencies. Communications between path computation clients (PCC) and PCEs, realized through the PCE Protocol (PCEP), also enable inter-PCE communications offering an attractive way to perform TE-based path computation among cooperating PCEs in multi-layer/domain scenarios, while preserving scalability and confidentiality. This survey presents the state-of-the-art on the PCE architecture for GMPLS-controlled networks carried out by research and standardization community. In this work, packet (i.e., MPLS-TE and MPLS-TP) and wavelength/spectrum (i.e., WSON and SSON) switching capabilities are the considered technological platforms, in which the PCE is shown to achieve a number of evident benefits

Supporting Service Differentiation in Multi-domain Multilayer Optical Networks

Providing differentiated quality of service became more and more important. This is not only because some service requests a high quality and real time transportation, but also because other services such as the capacity greedy applications request a higher bandwidth. In the meantime, has been the hybrid architecture consists of IP/MPLS domain and ASON/GMPLS optical domain projected as the infrastructure of the future internet. This architecture supports the transportation of the in near future expected data traffic on the ASON/GMPLS over DWDM optical domain, whereas it supports all the IP based service applications using the IP/MPLS domain. However, supporting service differentiation in multi-domain multilayer optical networks require the invention on routing scheme that supports both routing policies, the Physical Topology First (PTF) and Virtual Topology First (VTP), which are used to accommodate traffic in multilayer networks. In this work we use a hierarchical routing algorithm to evaluate the service differentiation schemes that are known in the literature in an IP/MPLS over ASON/GMPLS multi-domain network scenario, these service differentiation schemes are the Routing Policy Differentiation (RPD), Virtual Topology Differentiation (VTD) and Virtual Topology Sharing (VTS).&nbsp

On the challenges of establishing disjoint QoS IP/MPLS paths across multiple domains

MPLS is being actively adopted as the core switching infrastructure at the intradomain level. This trend is mainly attributable to the undeniable potential of MPLS in terms of virtual private networks (VPNs) management, traffic engineering (TE), QoS delivery, path protection, and fast recovery from network failures. However, little progress has been made to attain the expected extension of MPLS label-switched paths (LSPs) across domain boundaries. Among the problems that remain unsolved is how to efficiently find and establish primary and protection interdomain LSPs for mission-critical services subject to QoS constraints. This article explores the major limitations hindering the deployment of these kinds of LSPs across multiple domains, in the context of the current interdomain network model. We describe the critical problems faced by the research community, and present our vision on how to rationally overcome some of the problems exposed. Our perspective is that we should be prepared for rather coarse-grained solutions as long as we need to coexist with the current interdomain network modelPostprint (published version

Fast reroute paths algorithms

In order to keep services running despite link or node failure in MPLS networks, RSVP-TE fast reroute (FRR) schemes use precomputed backup label-switched path tunnels for local repair of LSP tunnels. In the event of failure, the redirection of traffic occurs onto backup LSP tunnels that have the same quality of service constraints as original paths. Local repair of LSP tunnels notably differ from traditional (1:1) dedicated path protection schemes in that traffic is diverted near the point of failure which speeds up the protection process by not having to notify the source and then resend the lost traffic. This gain in protection delay is crucial for MPLS networks which would otherwise suffer from an important recovery latency. In this paper, we investigate the algorithmic aspects of computing original paths along with their back-up so that they satisfy quality-of-service constraints (namely, delay) for single link or multiple link failure. In the case of single link failure, we propose an algorithm in O(nm+n 2log(n)) that computes shortest guaranteed paths with their backup towards a single destination. In the case of directed graphs, we show that this algorithm is optimal by proving that computing shortest guaranteed paths is as hard as to compute multiple source shortest paths in directed graphs. In the case of undirected graphs, we propose a faster algorithm with time complexity O(mlog(n)+n 2). We also provide a distributed algorithm based on Bellman-Ford distance computation which converges in 3n rounds at wors

Multi-domain crankback operation for IP/MPLS & DWDM networks

Network carriers and operators have built and deployed a very wide range of networking technologies to meet their customers needs. These include ultra scalable fibre-optic backbone networks based upon dense wavelength division multiplexing (DWDM) solutions as well as advanced layer 2/3 IP multiprotocol label switching (MPLS) and Ethernet technologies as well. A range of networking control protocols has also been developed to implement service provisioning and management across these networks. As these infrastructures have been deployed, a range of new challenges have started to emerge. In particular, a major issue is that of provisioning connection services between networks running across different domain boundaries, e.g., administrative geographic, commercial, etc. As a result, many carriers are keenly interested in the design of multi-domain provisioning solutions and algorithms. Nevertheless, to date most such efforts have only looked at pre-configured, i.e., static, inter-domain route computation or more complex solutions based upon hierarchical routing. As such there is significant scope in developing more scalable and simplified multi-domain provisioning solutions. Moreover, it is here that crankback signaling offers much promise. Crankback makes use of active messaging techniques to compute routes in an iterative manner and avoid problematic resource-deficient links. However very few multi-domain crankback schemes have been proposed, leaving much room for further investigation. Along these lines, this thesis proposes crankback signaling solution for multi-domain IP/MPLS and DWDM network operation. The scheme uses a joint intra/inter-domain signaling strategy and is fully-compatible with the standardized resource reservation (RSVP-TE) protocol. Furthermore, the proposed solution also implements and advanced next-hop domain selection strategy to drive the overall crankback process. Finally the whole framework assumes realistic settings in which individual domains have full internal visibility via link-state routing protocols, e.g., open shortest path first traffic engineering (OSPF-TE), but limited \u27next-hop\u27 inter-domain visibility, e.g., as provided by inter-area or inter-autonomous system (AS) routing protocols. The performance of the proposed crankback solution is studied using software-based discrete event simulation. First, a range of multi-domain topologies are built and tested. Next, detailed simulation runs are conducted for a range of scenarios. Overall, the findings show that the proposed crankback solution is very competitive with hierarchical routing, in many cases even outperforming full mesh abstraction. Moreover the scheme maintains acceptable signaling overheads (owing to it dual inter/intra domain crankback design) and also outperforms existing multi-domain crankback algorithms.\u2

Resilient network design: Challenges and future directions

This paper highlights the complexity and challenges of providing reliable services in the evolving communications infrastructure. The hurdles in providing end-to-end availability guarantees are discussed and research problems identified. Avenues for overcoming some of the challenges examined are presented. This includes the use of a highly available network spine embedded in a physical network together with efficient crosslayer mapping to offer survivability and differentiation of traffic into classes of resilience. © 2013 Springer Science+Business Media New York

Preserving confidentiality in PCE-based multi-domain networks

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Protection partagée pour les réseaux de transport multidomaines

Thèse numérisée par la Direction des bibliothèques de l'Université de Montréal