Improving internal BGP routing

While initially designed as a research network, the Internet has become a large interconnection of networks all over the world. Its infrastructure and the applications that it supports are in constant evolution. The Border Gateway Protocol (BGP) plays a key role in today's Internet, as the interdomain routing protocol used to build end-to-end paths. BGP is affected by the growth of the Internet, and this is problematic as the dataplane performances depend on the robustness and stability of this protocol. It is however difficult to modify BGP itself, as such a change requires cooperation between concurrent Internet Service Providers (ISPs). In this thesis, we study the behavior of BGP inside an ISP, and show that its internal organization is often responsible for a lack of alternate paths, preventing fast and local failure recovery. Slow BGP convergence inside an ISP affects the global reachability of impacted destinations and the number of BGP messages exchanged between ISPs. First, we propose several modifications to the classical iBGP organization to improve iBGP stability and reactivity upon failure. In the second part, we study a new variant of iBGP that allows several paths to be advertised for the same prefix on a session. This solution is promising, as it is able to solve several iBGP issues at once, but ISPs must be aware that additional paths increase the memory consumption inside routers and the number of BGP messages to process. We analyse the trade-offs of several deployment scenarios and provide a tool to simulate and compare them quantitatively. With the solutions presented in this thesis, ISPs are able to recover quickly from link failures and to reduce the number of BGP messages they propagate to their neighbors. They are thus able to contribute individually to a global improvement of Internet performances.(FSA 3) -- UCL, 201

Comparison of IBGP Topologies

This paper presents a method to evaluate iBGP topologies with route reflection, and to measure their performances compared to the full-mesh, in order to choose the best one. First, we describe the procedure and the criteria used for the comparison. After that, we briefly present the result of an application of this method to the GEANT network [3]. This analysis allows us then to isolate some of the factors that are influencing the quality of an iBGP topolog

Growing algorithmic thinking through interactive problems to encourage learning programming

Attracting pupils from secondary schools (12–18 years old) to learn programming is not easy. It is especially the case in Belgium where there is no or very few programming and algorithm design courses in secondary schools. Another issue is that teachers who are in charge of computer science courses are afraid of teaching a matter they do not feel comfortable with, especially when they are not informatics teachers. This paper presents ILPADS, interactive learning of programming and algorithm design skills, an interactive website which aims at gradually growing algorithmic thinking skills to lead pupils towards the learning of the Python programming language. That website aims to serve as working material to support teachers for their computer science courses in secondary schools. Pupils can also use the website at home to continue learning on their own. The paper presents the interactive website and mainly focuses on the design of the ILPADS activities. Future work includes testing the website in real classrooms and evaluating it

BGP Add-Paths: The Scaling/Performance Tradeoffs

Internet Service Providers design their network with resiliency in mind, having multiple paths towards external IP subnets available at the borders of their network. However, with the current internal Border Gateway Protocol, BGP routers and route reflectors only propagate their (unique) best path over their iBGP sessions. As a result, at the BGP router level, path diversity tends to be poor. Such lack of path diversity can lead to MED oscillations, prevents an efficient use of multipath BGP and does not allow for a fast and local recovery upon nexthop failure. Advertising multiple paths over iBGP sessions with BGP Add-Paths solves those issues, depending on the way the additional paths are selected. In this paper, we analyze the various options for the selection mode of the paths to be advertised. We show that these modes differently fulfill the needs of Add-Paths applications such as fast recovery upon failure and MED oscillation avoidance. We also show in our analysis that the costs and benefits bound with these modes depend on the connectivity of the AS where it is deployed. To support the analysis, we developed a tool allowing to measure the scaling of these modes in a given network. We illustrate the utilization of this tool on synthetic Internet topologies, and provide some recommendations for the choice of an Add-Paths selection mode

Automating the iBGP organization in large IP networks

For years, the Border Gateway Protocol has been used as the interdomain routing protocol inside the Internet [9]. This protocol allows ASes to exchange routes to reachable destinations. A BGP route contains, among other attributes, the list of ASes that form a path to the destination, i.e. an IP prefix. This list is called an AS Path. Thanks to the BGP routes it receives, an AS has all the information needed to forward packets towards their destination by sending them to the best BGP nexthop in the first AS in the AS Path. In practice, there are several BGP routers inside an AS. The routes from a neighbouring AS are received by the routers that have a peering session with this neighboring AS. Such sessions are called eBGP sessions. However, other routers that do not have a peering session with this particular neighbour also need to receive this information. For this purpose, routers inside an AS establish internal BGP sessions, called iBGP session

Quantifying ASes Multiconnectivity Using Multicast Information

peer reviewedRedundant connectivity (or multiconnectivity) between adjacent autonomous systems (ASes) is important for inter-domain traffic engineering and fast recovery in case of failures. However, the redundancy of ASes business relationship links has not been quantitatively studied, mainly due to the difficulty of obtaining relevant data. In this paper, we show that the mrinfo multicast monitoring tool can provide useful data about the Internet topology and such redundant links in particular. Our analysis relies on more than four years of daily queries to about ten thousand routers mapped into more than two hundred ASes. We demonstrate that peering links between ASes are frequently redundant. In particular, our analysis shows that more than half of the studied ASes pairs are connected through multiple physical links. We then refine our analysis by considering the different types of ASes and their business relationships. A particular result of our analysis is that at least 75% of the peer-to-peer relationships between adjacent Tier-1 ASes are redundant, i.e., the con- nections between these ASes involve several physical links. Our analysis is conservative, providing so a lower bound, as some links might not be seen by mrinfo due to ISPs filtering policies