Multiprotocol Label Switching Tunnels Research Articles

Crafting optimal and resilient iBGP-IP/MPLS overlays for transit backbone networks

The Internet is a collection of interconnected Autonomous Systems (ASes) that use the Border Gateway Protocol (BGP) to exchange reachability information. In this regard, BGP stability and scalability in the inter-domain scope have been matters of major concern for many years, and network engineers have been applying several techniques to cope with these issues. BGP is also used intra-domain (internal BGP - iBGP), to disseminate reachability information inside each AS, and works together with the Interior Gateway Protocols (IGPs) such as OSPF or IS-IS, to build routing tables. Route reflection is a widely adopted technique to tackle BGP scalability in the intra-domain scope, and choosing which routers will play the reflector role and which BGP sessions will be established among reflectors and clients (i.e. the routers which are not elected as reflectors), building an overlay of iBGP sessions, is known as the iBGP overlay design problem. The design of an optimal iBGP overlay is known to be a NP-Hard problem, and we proposed solutions for pure IP networks (i.e. best effort traffic forwarding) in our previous work. However, most Internet providers implement their backbones by combining IP routing with MPLS (Multiprotocol Label Switching) for QoS-aware traffic forwarding. MPLS forwarding incorporates traffic engineering and more efficient failover mechanisms; under this traffic forwarding paradigm, the design of traffic-engineered Label Switched Paths (LSPs, also referred as MPLS tunnels) shall be combined with the aforementioned iBGP overlay design. The present work introduces a coordinated design of both the iBGP overlay and the IP/MPLS substrates. Our contribution is the proposal of an optimal and resilient topology design for an IP/MPLS Internet backbone, which takes advantage of traffic engineering features to optimize the demands, while guaranteeing iBGP overlay optimality. We present a complete solution for a real world scenario, and we study the scalability of the solution for synthetic topologies, achieving encouraging results.

Revealing MPLS tunnels obscured from traceroute

Operators have deployed Multiprotocol Label Switching (MPLS) in the Internet for over a decade. However, its impact on Internet topology measurements is not well known, and it is possible for some MPLS configurations to lead to false router-level links in maps derived from traceroute data. In this paper, we introduce a measurement-based classification of MPLS tunnels, identifying tunnels where IP hops are revealed but not explicitly tagged as label switching routers, as well as tunnels that obscure the underlying path. Using a large-scale dataset we collected, we show that paths frequently cross MPLS tunnels in today's Internet: in our data, at least 30% of the paths we tested traverse an MPLS tunnel. We also propose and evaluate several methods to reveal MPLS tunnels that are not explicitly flagged as such: we discover that their fraction is significant (up to half the explicit tunnel quantity) but most of them do not obscure IP-level topology discovery.

Simulation and analysis of an admission control mechanism for MPLS DS-TE

Providing quality of service (QoS) is one of the main challenges in the internet that has recently gained the interest of many researchers. The internet architecture was originally designed to provide IP based “best effort” services to all its applications. The best effort service could be acceptable for traditional applications such as email and web browsing, however, it is inadequate for new classes of emerging applications with real time data such as audio and video streaming. These new applications demand good quality of service from the network due to their inherent high data throughput (bandwidth) and low-latency requirements. Three main architectures were proposed by IETF in an effort to make the IP QoS a reality. They are integrated services (Intserv), differentiated services (DiffServ) and multiprotocol label switching (MPLS). Sometimes perceived as competitor, DiffServ and MPLS are in fact complementary developments that approach the QoS challenge from two different network perspectives. Thus these two approaches can be used together in order to combine their merits. This paper discusses an improved admission control which is aimed at enabling MPLS-TE tunnels differentiations (DS-TE tunnels). It presents a simulation based study which demonstrates the effectiveness of the proposed scheme where DiffServ EF traffic is mapped to MPLS tunnel to ensure stable performance for the traffic in the MPLS Domain.

SEQUIN: An SNMP-based MPLS network monitoring system

Multiprotocol label switching (MPLS)-based networks are gaining popularity with service providers because they retain the flexibility of Internet protocol (IP) while providing support for quality of service (QoS) through differentiated services (DiffServ). The deployment of such networks requires service providers to ensure that service-level agreements (SLAs) with their customers are being met while guaranteeing cost-effective utilization of their network. The key to achieving these objectives is an efficient monitoring system that tracks QoS metrics such as bandwidth utilization, delay, and packet loss. These metrics can be tracked at multiple granularities, such as per customer, per MPLS tunnel, and per physical network pipe. SEQUIN is a simple network management protocol (SNMP)-based monitoring system capable of tracking QoS metrics in near real time. Some of the challenges addressed by SEQUIN are synthesis of end-to-end QoS using polled data from different network elements, visualization of these metrics across the network, identification of performance problems by correlating the monitored parameters, and design of scalable polling strategies to minimize management traffic. © 2003 Lucent Technologies Inc.