Destination Prefix Research Articles

Bartolomeu: An SDN rebalancing system across multiple interdomain paths

Bartolomeu is a solution to enable stub networks to perform adaptive egress traffic load balancing across multiple interdomain routes by spreading the traffic across available paths according to a passive measurement of their performance. It defines a BGP-SDN architecture that increases the number of BGP routes that can be used by stub networks. Bartolomeu measures the available capacity of each path to any destination prefix, and allocates to each path a number of large flows that is proportional to its capacity. This strategy reduces the mean sojourn time, i.e., mean time to flow completion, compared to state-of-the-art traffic balancing techniques as ECMP. We develop a mathematical model to compute this time and compare with ECMP and single path (fast path) selection. An analysis of the traffic traces of two content providers was performed to ensure that our solution is deployable. An experiment with traffic exchange over the Internet is used to show that Bartolomeu can provide gains with real interfering traffic. A discrete-event simulator fed with the traces captured is used to asses Bartolomeu’s gains with prefixes with different number of flows, and flows with different sizes and arrival time. We observe in this experiment that Bartolomeu can reduce the sojourn time, compared to ECMP, by half when path rates differ in a factor of 3, or to a sixth when path rates differ in a factor of 10. We compute the maximum number of per-flow entries and the maximum entry change request rate to show that the resources required fit in with the specifications of the current generation of SDN switches.

Improving BGP Protocol to Advertise Multiple Routes for the Same Destination Prefix

An Internet autonomous system (AS) uses BGP policies in order to meet its local objectives (e.g. optimal routing within AS) and peering contracts with neighboring ASes (e.g. advertising some specific routes to a neighbor, forwarding traffic over specific paths, etc.) In this paper we propose an enhancement of BGP route selection and advertisement processes, and demonstrate how the enhanced BGP can be used to flexibly implement diverse policies, regardless of the network topology, that were not feasible before.

Neighbor-specific BGP

The Border Gateway Protocol (BGP) offers network administrators considerable flexibility in controlling how traffic flows through their networks. However, the interaction between routing policies in different Autonomous Systems (ASes) can lead to protocol oscillation. The best-known sufficient conditions of BGP global routing stability impose restrictions on the kinds of local routing policies individual ASes can safely implement. In this paper, we present neighbor-specific BGP (NS-BGP), a modest extension to BGP that enables a much wider range of local policies without compromising global stability. Whereas a conventional BGP-speaking router selects a single "best" route (for each destination prefix), NS-BGP allows a router to customize the route selection on behalf of each neighbor. For example, one neighbor may prefer the shortest route, another the most secure route, and yet another the least expensive route. Surprisingly, we prove that the much more flexible NS-BGP is guaranteed to be stable under much less restrictive conditions on how routers "rank" the candidate routes. We also show that it is safe to deploy NS-BGP incrementally, as a routing system with a partial deployment of NS-BGP is guaranteed to be stable, even in the presence of failure and other topology changes. In addition to our theoretical results, we also describe how NS-BGP can be deployed by individual ASes independently without changes to the BGP message format or collaboration from neighboring ASes.

On model-driven self-engineering of inter-domain traffic

Realizing autonomic networking is possible with the clear understanding of required control mechanisms under multiplexing. Attempting such understanding ecosystem is motivated as a novel unit of design, exemplified by the two extreme cases – micro-ecosystem of a single buffer with random early detection mechanism, and macro-ecosystem of a path of autonomous systems sharing traffic handling to the same destination prefix. Both problems are formalised as model-driven information coupling of distributed controllers, implicit for the micro, and explicit for the macro-ecosystems. The main contributions are ecosystem examples and their driving models; the geometry based route view diagram driving self-engineering of traffic is original, while linear bound of packet loss ratio driving the micro-ecosystem is borrowed from the literature and adapted.

TIE Breaking: Tunable Interdomain Egress Selection

In a large backbone network, the routers often have multiple egress points they could use to direct traffic toward an external destination. Today's routers select the ldquoclosestrdquo egress point, based on the intradomain routing configuration, in a practice known as early-exit or hot-potato routing. In this paper, we argue that hot-potato routing is restrictive, disruptive, and convoluted and propose an alternative called TIE (Tunable Interdomain Egress selection). TIE is a flexible mechanism that allows routers to select the egress point for each destination prefix based on both the intradomain topology and the goals of the network administrators. In fact, TIE is designed from the start with optimization in mind, to satisfy diverse requirements for traffic engineering and network robustness. We present two example optimization problems that use integer-programming and multicommodity-flow techniques, respectively, to tune the TIE mechanism to satisfy networkwide objectives. Experiments with traffic, topology, and routing data from two backbone networks demonstrate that our solution is both simple (for the routers) and expressive (for the network administrators).

MIRO

The Internet consists of thousands of independent domains with different, and sometimes competing, business interests. However, the current interdomain routing protocol (BGP) limits each router to using a single route for each destination prefix, which may not satisfy the diverse requirements of end users. Recent proposals for source routing offer an alternative where end hosts or edge routers select the end-to-end paths. However, source routing leaves transit domains with very little control and introduces difficult scalability and security challenges. In this paper, we present a multi-path inter-domain routing protocol called MIRO that offers substantial flexiility, while giving transit domains control over the flow of traffic through their infrastructure and avoiding state explosion in disseminating reachability information. In MIRO, routers learn default routes through the existing BGP protocol, and arbitrary pairs of domains can negotiate the use of additional paths (bound to tunnels in the data plane) tailored to their special needs. MIRO retains the simplicity of BGP for most traffic, and remains backwards compatible with BGP to allow for incremental deployability. Experiments with Internet topology and routing data illustrate that MIRO offers tremendous flexibility for path selection with reasonable overhead.

Traffic-engineering-aware shortest-path routing and its application in IP-over-WDM networks [Invited

Feature Issue on Next-Generation WDM Network Design and Routing (WDMN). Single shortest-path routing is known to perform poorly for Internet traffic engineering (TE) where the typical optimization objective is to minimize the maximum link load. Splitting traffic uniformly over equal-cost multiple shortest paths in open shortest path first and intermediate system-intermediate system protocols does not always minimize the maximum link load when multiple paths are not carefully selected for the global traffic demand matrix. However, a TE-aware shortest path among all the equal-cost multiple shortest paths between each ingress-egress pair can be selected such that the maximum link load is significantly reduced. IP routers can use the globally optimal TE-aware shortest path without any change to existing routing protocols and without any serious configuration overhead. While calculating TE-aware shortest paths, the destination-based forwarding constraint at a node should be satisfied, because an IP router will forward a packet to the next hop toward the destination by looking up the destination prefix. We present a mathematical problem formulation for finding a set of TE-aware shortest paths for the given network as an integer linear program, and we propose a simple heuristic for solving large instances of the problem. Then we explore the usage of our proposed algorithm for the integrated TE method in IP-over-WDM networks. The proposed algorithm is evaluated through simulations in IP networks as well as in IP-over-WDM networks.