Relay path selection approaches in peer-to-peer VoIp systems

Multipath overlay routing technologies are seen as alternative solutions for VoIP because they inherit path diversity from peer-to-peer overlay networks. We discuss and compare the performances of two relay path selection approaches proposed for VoIP overlay systems through extensive simulations. We propose a new method for relay path computation that takes into account both path disjointness and other network quality factors (such as packet delay or loss). We further apply our method in different overlay network scenarios by varying the supernode distribution. It is found that there is a considerable improvement of path performance when relaying traffic through highly connected ASs using the new method

Inferring Internet AS Relationships Based on BGP Routing Policies

The type of business relationships between the Internet autonomous systems (AS) determines the BGP inter-domain routing. Previous works on inferring AS relationships relied on the connectivity information between ASes. In this paper we infer AS relationships by analysing the routing polices of ASes encoded in the BGP attributes Communities and the Locpref. We accumulate BGP data from RouteViews, RIPE RIS and the public Route Servers in August 2010 and February 2011. Based on the routing policies extracted from data of the two BGP attributes, we obtain AS relationships for 39% links in our data, which include all links among the Tier-1 ASes and most links between Tier-1 and Tier-2 ASes. We also reveal a number of special AS relationships, namely the hybrid relationship, the partial-transit relationship, the indirect peering relationship and the backup links. These special relationships are relevant to a better understanding of the Internet routing. Our work provides a profound methodological progress for inferring the AS relationships.Comment: 8 pages and 3 figure

A critical look at power law modelling of the Internet

This paper takes a critical look at the usefulness of power law models of the Internet. The twin focuses of the paper are Internet traffic and topology generation. The aim of the paper is twofold. Firstly it summarises the state of the art in power law modelling particularly giving attention to existing open research questions. Secondly it provides insight into the failings of such models and where progress needs to be made for power law research to feed through to actual improvements in network performance.Comment: To appear Computer Communication

Quantifying AS Path Inflation by Routing Policies

A route in the Internet may take a longer AS path than the shortest AS path due to routing policies. In this paper, we systematically analyze AS paths and quantify the extent to which routing policies inflate AS paths. The results show that AS path inflation in the Internet is more prevalent than expected. We first present the extent of AS path inflation observed from the RouteView and RIPE routing tables. We then employ three common routing policies to show the extent of AS path inflation. We find that No-Valley routing policy causes the least AS path inflation among the three routing policies. PreferCustomer-and-Peer-over-Provider policy causes the most AS path inflation. In addition, we find that single-homed stub ASes experience more path inflations than transit ASes and multi-homed ASes. The AS pairs with shortest AS path of 3 AS hops experience more path inflations than other AS pairs. Finally, we investigate the AS path inflation on the end-to-end path from end users to two popular content providers, Google and Comcast. Although the majority of the shortest AS paths from end users to the two providers consists of no more than three AS hops, the actual end-to-end paths that the traffic will take are longer than the shortest AS paths in many cases. Quantifying AS path inflation in the Internet has important implications on the extent of routing policies, traffic engineering performed on the Internet, and BGP convergence speed

Computing Observed Autonomous System Relationships in the Internet

Autonomous Systems (ASes) in the Internet use BGP to perform interdomain routing. BGP routing policies are mainly determined by the business relationships between neighboring ASes, which can be classified into three types: provider-to-customer, peer-to-peer, and sibling-to-sibling. ASes usually do not export provider routes and peer routes to providers or peers. It has been proved that if all ASes conform to this common export policy then all AS paths are valley-free. Since AS relationships are not publicly available, several studies have proposed heuristic algorithms for inferring AS relationships using publicly available BGP data. Most of these algorithms rely on the valley-free property of AS paths. However, not all AS paths are valley-free because some ASes do not conform to the common export policy. As a result, inferred AS relationship are inaccurate. Instead of inferring AS relationships, we propose an algorithm for computing observed AS relationships based on transit relationships between ASes that are revealed by BGP data. We analyze the types of mismatches between observed AS relationships and actual AS relationships and show that the mismatches can be used to identify ASes that violate the common export policy

Inferring multilateral peering

The AS topology incompleteness problem is derived from difficulties in the discovery of p2p links, and is amplified by the increasing popularity of Internet eXchange Points (IXPs) to support peering interconnection. We describe, implement, and validate a method for discovering currently invisible IXP peering links by mining BGP communities used by IXP route servers to implement multilateral peering (MLP), including communities that signal the intent to restrict announcements to a subset of participants at a given IXP. Using route server data juxtaposed with a mapping of BGP community values, we can infer 206K p2p links from 13 large European IXPs, four times more p2p links than what is directly observable in public BGP data. The advantages of the proposed technique are threefold. First, it utilizes existing BGP data sources and does not require the deployment of additional vantage points nor the acquisition of private data. Second, it requires only a few active queries, facilitating repeatability of the measurements. Finally, it offers a new source of data regarding the dense establishment of MLP at IXPs