cnp3-ebook/protocols/bgp — English @ Weblate

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125 ../../protocols/bgp.rst:440

	English From a theoretical perspective, these guidelines should be verified automatically to ensure that BGP will always converge in the global Internet. However, such a verification cannot be performed in practice because this would force all domains to disclose their routing policies (and few are willing to do so) and furthermore the problem is known to be NP-hard [GW1999]. 370/10000 · 370
126 ../../protocols/bgp.rst:442

	English In practice, researchers and operators expect that these guidelines are verified [#fgranularity]_ in most domains. Thanks to the large amount of BGP data that has been collected by operators and researchers [#fbgpdata]_, several studies have analyzed the AS-level topology of the Internet. [SARK2002]_ is one of the first analysis. More recent studies include [COZ2008]_ and [DKF+2007]_ 386/10000 · 386
127 ../../protocols/bgp.rst:444

	English Based on these studies and [ATLAS2009]_, the AS-level Internet topology can be summarized as shown in the figure below. 119/10000 · 119
128 ../../protocols/bgp.rst:450

	English The layered structure of the global Internet 44/10000 · 44
129 ../../protocols/bgp.rst:454

	English The domains on the Internet can be divided in about four categories according to their role and their position in the AS-level topology. 136/10000 · 136
130 ../../protocols/bgp.rst:465

	English Due to this organization of the Internet and due to the BGP decision process, most AS-level paths on the Internet have a length of 3-5 AS hops. 143/10000 · 143
131 ../../protocols/bgp.rst:470

	English Footnotes 9/10000 · 9
132 ../../protocols/bgp.rst:471

	English An analysis of the evolution of the number of domains on the global Internet during the last ten years may be found in http://www.potaroo.net/tools/asn32/. 155/10000 · 155
133 ../../protocols/bgp.rst:473

	English Several web sites collect and analyze data about the evolution of BGP in the global Internet. http://bgp.potaroo.net provides lots of statistics and analyzes that are updated daily. 181/10000 · 181
134 ../../protocols/bgp.rst:475

	English See http://as-rank.caida.org/ for an analysis of the interconnections between domains based on measurements collected in the global Internet. 142/10000 · 142
135 ../../protocols/bgp.rst:478

	English Two routers that are attached to the same IXP exchange packets only when the owners of their domains have an economical incentive to exchange packets on this IXP. Usually, a router on an IXP is only able to exchange packets with a small fraction of the routers that are present on the same IXP. 294/10000 · 294
136 ../../protocols/bgp.rst:480

	English See ftp://ftp.ripe.net/ripe/dbase for the RIPE database that contains the import and export policies of many European ISPs. 123/10000 · 123
137 ../../protocols/bgp.rst:482

	English In this text, we consider Autonomous System and domain as synonyms. In practice, a domain may be divided into several Autonomous Systems, but we ignore this detail. 165/10000 · 165
138 ../../protocols/bgp.rst:484

	English The BGP sessions and the underlying TCP connection are typically established by the routers when they boot based on information found in their configuration. The BGP sessions are rarely released, except if the corresponding peering link fails or one of the endpoints crashes or needs to be rebooted. 299/10000 · 299
139 ../../protocols/bgp.rst:486

	English 90 seconds is the default delay recommended by :rfc:`4271`. However, two BGP peers can negotiate a different timer during the establishment of their BGP session. Using a too small interval to detect BGP session failures is not recommended. BFD [KW2009]_ can be used to replace BGP's KEEPALIVE mechanism if fast detection of interdomain link failures is required. 362/10000 · 362
140 ../../protocols/bgp.rst:488

	English A link is said to be flapping if it switches several times between an operational state and a disabled state within a short period of time. A router attached to such a link would need to frequently send routing messages. 220/10000 · 220
141 ../../protocols/bgp.rst:490

	English Researchers such as [MUF+2007]_ have shown that modeling the Internet topology at the AS-level requires more than the `shared-cost` and `customer->provider` peering relationships. However, there is no publicly available model that goes beyond these classical peering relationships. 281/10000 · 281
142 ../../protocols/bgp.rst:492

	English BGP data is often collected by establishing BGP sessions between Unix hosts running a BGP daemon and BGP routers in different ASes. The Unix hosts stores all BGP messages received and regular dumps of its BGP routing table. See http://www.routeviews.org, http://www.ripe.net/ris, http://bgp.potaroo.net or http://irl.cs.ucla.edu/topology/. 339/10000 · 339
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