Redundancy and Robustness of the AS-level Internet topology and its models

A comparison between the topological properties of the measured Internet topology, at the autonomous system level (AS graph), and the equivalent graphs generated by two different power law topology generators is presented. Only one of the synthetic generators reproduces the tier connectivity of the AS graph

The Internet's unexploited path diversity

The connectivity of the Internet at the Autonomous System level is influenced by the network operator policies implemented. These in turn impose a direction to the announcement of address advertisements and, consequently, to the paths that can be used to reach back such destinations. We propose to use directed graphs to properly represent how destinations propagate through the Internet and the number of arc-disjoint paths to quantify this network's path diversity. Moreover, in order to understand the effects that policies have on the connectivity of the Internet, numerical analyses of the resulting directed graphs were conducted. Results demonstrate that, even after policies have been applied, there is still path diversity which the Border Gateway Protocol cannot currently exploit.Comment: Submitted to IEEE Communications Letter

On Compact Routing for the Internet

While there exist compact routing schemes designed for grids, trees, and Internet-like topologies that offer routing tables of sizes that scale logarithmically with the network size, we demonstrate in this paper that in view of recent results in compact routing research, such logarithmic scaling on Internet-like topologies is fundamentally impossible in the presence of topology dynamics or topology-independent (flat) addressing. We use analytic arguments to show that the number of routing control messages per topology change cannot scale better than linearly on Internet-like topologies. We also employ simulations to confirm that logarithmic routing table size scaling gets broken by topology-independent addressing, a cornerstone of popular locator-identifier split proposals aiming at improving routing scaling in the presence of network topology dynamics or host mobility. These pessimistic findings lead us to the conclusion that a fundamental re-examination of assumptions behind routing models and abstractions is needed in order to find a routing architecture that would be able to scale ``indefinitely.''Comment: This is a significantly revised, journal version of cs/050802

Internet routing paths stability model and relation to forwarding paths

Analysis of real datasets to characterize the local stability properties of the Internet routing paths suggests that extending the route selection criteria to account for such property would not increase the routing path length. Nevertheless, even if selecting a more stable routing path could be considered as valuable from a routing perspective, it does not necessarily imply that the associated forwarding path would be more stable. Hence, if the dynamics of the Internet routing and forwarding system show different properties, then one can not straightforwardly derive the one from the other. If this assumption is verified, then the relationship between the stability of the forwarding path (followed by the traffic) and the corresponding routing path as selected by the path-vector routing algorithm requires further characterization. For this purpose, we locally relate, i.e., at the router level, the stability properties of routing path with the corresponding forwarding path. The proposed stability model and measurement results verify this assumption and show that, although the main cause of instability results from the forwarding plane, a second order effect relates forwarding and routing path instability events. This observation provides the first indication that differential stability can safely be taken into account as part of the route selection process

Preserving Established Communications in IPv6 Multi-homed Sites with MEX

This research was supported by the SAM (Advanced Mobility Services) project, funded by the Spanish National R&D Programme under contract MCYT TIC2002-04531-C04-03.A proper support for multimedia communications transport has to provide fault tolerance capabilities such as the preservation of established connections in case of failures. While multi-homing addresses this issue, the currently available solution based in massive BGP route injection presents serious scalability limitations, since it contributes to the exponential growth of the BGP table size. Alternative solutions proposed for IPv6 fail to provide equivalent facilities to the current BGP based solution. In this paper we present MEX (Muti-homing through EXtension header) a novel proposal for the provision of IPv6 multi-homing capabilities. MEX preserves overall scalability by storing alternative route information in end-hosts while at the same time reduces packet loss by allowing routers to re-route in-course packets. This behavior is enabled by conveying alternative route information within packets inside a newly defined Extension Header. The resulting system provides fault tolerance capabilities and preserves scalability, while the incurred costs, namely deployment and packet overhead, are only imposed to those that benefit from it. An implementation of the MEX host and router components is also presented.Publicad