Clarence Filsfils

Achieving sub-50 milliseconds recovery upon BGP peering link failures

Recent measurements show that BGP peering links can fail as frequently as intradomain links and usually for short periods of time. We propose a new fast-reroute technique where routers are prepared to react quickly to interdomain link failures. For each of its interdomain links, a router precomputes a protection tunnel, i.e., an IP tunnel to an alternate nexthop which can reach the same destinations as via the protected link.We propose a BGP-based auto-discovery technique that allows each router to learn the candidate protection tunnels for its links. Each router selects the best protection tunnels for its links and when it detects an interdomain link failure, it immediately encapsulates the packets to send them through the protection tunnel. Our solution is applicable for the links between large transit ISPs and also for the links between multi-homed stub networks and their providers. Furthermore, we show that transient forwarding loops (and thus the corresponding packet losses) can be avoided during the routing convergence that follows the deactivation of a protection tunnel in BGP/MPLS VPNs and in IP networks using encapsulation.

A Declarative and Expressive Approach to Control Forwarding Paths in Carrier-Grade Networks

SDN simplifies network management by relying on declarativity (high-level interface) and expressiveness (network flexibility). We propose a solution to support those features while preserving high robustness and scalability as needed in carrier-grade networks. Our solution is based on (i) a two-layer architecture separating connectivity and optimization tasks; and (ii) a centralized optimizer called framework, which translates high-level goals expressed almost in natural language into compliant network configurations. Our evaluation on real and synthetic topologies shows that framework improves the state of the art by (i) achieving better trade-offs for classic goals covered by previous works, (ii) supporting a larger set of goals (refined traffic engineering and service chaining), and (iii) optimizing large ISP networks in few seconds. We also quantify the gains of our implementation, running Segment Routing on top of IS-IS, over possible alternatives (RSVP-TE and OpenFlow).

The Segment Routing Architecture

Network operators anticipate the offering of an increasing variety of cloud-based services with stringent Service Level Agreements. Technologies currently supporting IP networks however lack the flexibility and scalability properties to realize such evolution. In this article, we present Segment Routing (SR), a new network architecture aimed at filling this gap, driven by use-cases defined by network operators. SR implements the source routing and tunneling paradigms, letting nodes steer packets over paths using a sequence of instructions (segments) placed in the packet header. As such, SR allows the implementation of routing policies without per-flow entries at intermediate routers. This paper introduces the SR architecture, describes its related ongoing standardization efforts, and reviews the main use-cases envisioned by network operators.

Multi-layer capacity planning for IP-optical networks

We consider a pragmatic multi-layer capacity planning approach for an IP over optical network, which builds on existing planning practices. We first describe a router bypass process that considers the real impact of the IP layer topology change, given the actual behavior of the IP layer, leveraging a commercial IP planning tool. We then consider the design and cost impact of several multi-layer restoration schemes. We compute the savings achieved on two real-world core network models. The resulting savings are similar for both networks and are very promising.

Deploying Diffserv at the network edge for tight SLAs, Part 2

In the first of a two-part series, we review industry best practices for designing, validating, deploying, and operating IP-based services at the network edge with tight service-level agreements (SLAs). We describe the important SLA metrics for IP service performance and discuss why Diffserv is the preferred technology to achieve these SLAs.

Deploying diffserv in backbone networks for tight SLA control

The differentiated services architecture (Diffserv) enables service providers to offer tighter, more comprehensive service-level agreements (SLAs) for IP service performance. One way it does this is by letting designers engineer IP backbone networks to assure that SLA parameters are met on a per-class basis. This review covers best practices for designing, validating, deploying, and operating Diffserv in the network backbone. It also presents new results from router-based testing that demonstrate how, with Diffserv, high-performance backbone routers can achieve tight SLA capabilities.

Engineering a multiservice IP backbone to support tight SLAs

This paper describes technologies that enable IP service providers to offer tighter service level agreements for IP performance, in order to create competitive advantage and better serve their customers. The SLA parameters that need to be tightened are defined and then the technologies that should be considered are described, together with the decision criteria on where each technology should be used. This paper is based upon current best practise and includes results from both lab testing and deployment experience. The specific technologies discussed are differentiated services, fast IGP convergence, and traffic engineering. Consideration is given to how these technologies should be deployed and operated.

Beyond MPLS ... Less is More

Multiprotocol label switching possesses a simple data plane that has enabled new services and functions operating in many service provider networks. Yet, the MPLS control plane can impose both technical and operational challenges. This article explores these challenges and examines recent advances in IP routing technology suggesting that all services - including those that are MPLS-based - can be delivered over networks running only IP.

IP-optical interaction during traffic restoration

We analyze the required interaction between the optical and IP layers to enable restoration of IP links in the optical layer. Significant interaction is needed to achieve a cost effective process that minimizes traffic impact.

A local approach to fast failure recovery of LISP ingress tunnel routers

LISP (Locator/ID Separation Protocol) has been proposed as a future Internet architecture in order to solve the scalability issues the current architecture is facing. LISP tunnels packets between border routers, which are the locators of the non-globally routable identifiers associated to end-hosts. In this context, the encapsulating routers, which are called Ingress Tunnel Routers (ITR) and learn dynamically identifier-to-locators mappings needed for the encapsulation, can cause severe and long lasting traffic disruption upon failure. In this paper, thanks to real traffic traces, we first explore the impact of ITR failures on ongoing traffic. Our measurements confirm that the failure of an ITR can have severe impact on traffic. We then propose and evaluate an ITR synchronization mechanism to locally protect ITRs, achieving disruptionless traffic redirection. We finally explore how to minimize the number of ITRs to synchronize in large networks.