ISSN:1124-318X    

DOI:10.1002/ett.4460130102

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:2002

数据来源: WILEY

摘要:

AbstractIn this paper, we study traffic demands in an IP bacbkone, identify the routes used by these demands, and evaluate traffic granularity levels that are attractive for improving the poor load balancing that our study reveals. The data used in this study was collected at a major POP in a commercial Tier‐1 IP backbone. In the first part of this paper we ask two questions. What is the traffic demand between a pair of POPs in the backbone? How stable is this demand? We develop a methodology that combines packet‐level traces from access links in the POP and BGP routing information to build components of POP‐to‐POP traffic matrices. Our analysis shows that the geographic spread of traffic across egress POPs is far from uniform. In addition, we find that the time of day behaviors for different POPs and different access links also exhibit a high degree of heterogeneity. In the second part of this work, we examine commercial routing practices to assess how these demands are routed through the backbone. We find that traffic between a pair of POPs is engineered to be restricted to a few paths and that this contributes to widely varying link utilization levels. The natural question that follows from these findings is whether or not there is a better way to spread the traffic across backbone paths. We identify traffic aggregates based on destination address prefixes and find that this set of criteria isolates a few aggregates that account for an overwhelmingly large portion of inter‐POP traffic. We demonstrate that these aggregates exhibit stability throughout the day on per‐hour time scales, and thus form a natural basis for splitting traffic over multiple paths to improve loa

ISSN:1124-318X    

DOI:10.1002/ett.4460130103

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:2002

数据来源: WILEY

摘要:

AbstractWe study the interdomain traffic as seen by a non‐transit ISP, based on a six days trace covering all the interdomain links of this ISP. Our analysis considers the relationships between the interdomain traffic and the interdomain topology. We first discuss the day‐to‐day stability of the interdomain traffic matrix to evaluate the feasibility of interdomain traffic engineering. Then, we study the variability of the interdomain flows for several aggregation levels (prefix, AS and sink tree) and with respect to the interdomain topology seen by BGP. We show that despite the important variability of interdomain flows, it would be useful for a non‐transit ISP to traffic engineer its access traffic by relying on a sink tree aggregatio

ISSN:1124-318X    

DOI:10.1002/ett.4460130104

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:2002

数据来源: WILEY

摘要:

AbstractWe analyze the evolution of the global Internet interdomain routing system on AS, prefix and IP address level granularities, using snapshots of Route Views BGP tables from 1997 to 2001. We introduce the notion ofsemiglob‐ally routed prefixes, those present in the majority of backbone tables, and classify them intostandalone ‐those which have no subsets, no supersets;root— have subsets, but no supersets; andsubset, or more specific, which are subsets of other blocks. Using these distinctions we find that from 1999 to 2001 many measures of routing system complexity demonstrated stability in the form of slow growth, dynamic equilibrium, and occasional contraction. We find that many net change measures reflect contributions of opposite sign, and that true measure of variation, or chum, is the sum of their absolute magnitudes rather than the difference. Appearance and disappearance of prefixes, ASes and Route Views peers, as well as status changes (an AS changing from transit to non‐transit, or a prefix shifting from a standalone prefix to a root prefix) are instances of routing systemchurn.One advantage of using our notion of semiglobal prefixes is that they exhibit less chum than global prefixes (those prefixes common to all backbone tables) and as such allow for derivation of more robust macroscopic statistics about the routing system. We study route prefix instability at a medium time granularity for late 2001 using 2‐hour snapshots of BGP tables, and find that half of all prefix reannouncements(flips)are contributed by 1% of all ASes, with government networks, telecoms in developing countries and major backbone ISPs at the top of the list of instability contributors. Small ASes (those who originate only a few prefixes into the global routing system) do not contribute more than their fair share of either route entries or churn to the global routing system. We conclude that during 1999‐2001 many Internet metrics were stable, and that the routing system's growth and instability are mostly caused by large and medium

ISSN:1124-318X    

DOI:10.1002/ett.4460130105

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:2002

数据来源: WILEY

摘要:

AbstractCongestion is a major Internet problem. TCP has evolved in attemptting to deal with this and now employs congestion control algorithms that effectively limit the bandwidth available to any one connection. However, as TCP is not the only transport protocol used on the Internet, the growth of non‐TCP traffic has lead to the formulation of TCP‐Friendly formulae. It is recommended that all best effort traffic conform to these formulae, and they act as a benchmark against which the success of any congestion control algorithms can be judged. Unfortunately, key assumptions behind the formulation of TCP's algorithms — low bandwidth, and bulk data transfers — are often no longer valid. In this paper it is shown that the combination of increasing bandwidth and short web transfers means that a significant amount of TCP traffic fails to obtain the bandwidth implied by the TCP‐friendly formulae. An alternative, measurement‐based approach that predicts a fairer starting window size for a connection is presented and evaluated. Information about the characteristics of particular network paths is dynamically maintained and used to suggest a fairer starting window size for new connections. Minor modifications to TCP allow these suggestions to be used to set start‐up control variables, and thereby strengthen the negative correlation between the bandwidth used by a connection and the level of congestion on its network path. The measurement‐based approach is realised through the use of a Location Information Server (LIS). The LIS performs centralised passive monitoring of transport headers in order to derive network level path information. Location Information Packets (LIP) are used to communicate suggested start‐up variables to local hosts. The design, implementation and evaluation of an LIS, LIP and participating host's TCP softw

ISSN:1124-318X    

DOI:10.1002/ett.4460130106

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:2002

数据来源: WILEY

摘要:

AbstractInternet traffic engineering is defined as performance evaluation and performance optimisation of operational IP networks. The definition covers both planning and routing optimisation. Planning typically optimises network topology at large time scales. Routing optimisation optimises the routing configuration in the network for a specific traffic matrix, assuming a fixed topology. With automatically switched transport networks the topology provides an additional degree of freedom at time scales on the order of magnitude of those at which traffic engineering operates. Therefore, in such a network, the decision processes should be co‐ordinated. The present contribution describes an approach and algorithms to support such co‐ordinated decisions in a centralised off‐line traffic‐engineering tool. The approach optimises the logical topology and link capacity overlaying the ASTN and the IP routing configuration. It is supported by a simulation

ISSN:1124-318X    

DOI:10.1002/ett.4460130107

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:2002

数据来源: WILEY

ISSN:1124-318X    

DOI:10.1002/ett.4460130108

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:2002

数据来源: WILEY

ISSN:1124-318X    

DOI:10.1002/ett.4460130109

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:2002

数据来源: WILEY

ISSN:1124-318X    

DOI:10.1002/ett.4460130101

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:2002

数据来源: WILEY