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<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt;mso-fareast-language:EN-US">It assumes that
</span><span style="font-size:11.0pt;mso-fareast-language:EN-US">Extended Length bit</span><span style="font-size:11.0pt;mso-fareast-language:EN-US">
<span lang="EN-US">of Attribute Type is properly implemented so community attribute can use attribute length field as 2 octet field, right?<o:p></o:p></span></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt;mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt;mso-fareast-language:EN-US">How situation changes with
</span><span style="font-size:11.0pt;mso-fareast-language:EN-US"><a href="http://www.rfc-editor.org/info/rfc8654">RFC 8654</a> - Extended Message Support for BGP</span><span lang="EN-US" style="font-size:11.0pt;mso-fareast-language:EN-US">?<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;mso-fareast-language:EN-US"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span lang="EN-US" style="font-size:11.0pt;color:black">Regards,</span><span style="font-size:11.0pt;color:black"><o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;color:black;mso-fareast-language:EN-US">Grzegorz</span><span style="font-size:11.0pt;mso-fareast-language:EN-US"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;mso-fareast-language:EN-US"><o:p> </o:p></span></p>
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<p class="MsoNormal"><b><span style="font-family:"Calibri",sans-serif;color:black">From:
</span></b><span style="font-family:"Calibri",sans-serif;color:black">Ondrej Zajicek <santiago@crfreenet.org><br>
<b>Date: </b>Friday, 12 July 2024 at 05:40<br>
<b>To: </b>"Ponikierski, Grzegorz" <gponikie@akamai.com><br>
<b>Cc: </b>"bird-users@network.cz" <bird-users@network.cz><br>
<b>Subject: </b>Re: Limit of numbers of BGP communities<o:p></o:p></span></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">On Fri, Jul 12, 2024 at 02:30:10AM +0000, Ponikierski, Grzegorz via Bird-users wrote:<o:p></o:p></p>
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<p class="MsoNormal">Hello all!<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">How many standard communities, extended communities and large<o:p></o:p></p>
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<p class="MsoNormal">communities, user can apply on a route using Bird? BGP UPDATE message has<o:p></o:p></p>
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<p class="MsoNormal">finite size so I guess that there must be a limit somewhere.<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Hello<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">There is no specific limit on communities, just a limit on overall BGP<o:p></o:p></p>
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<p class="MsoNormal">attribute length on export, which is 1 kB less than BGP message size<o:p></o:p></p>
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<p class="MsoNormal">(there is 1 kB reserved for prefixes). So with regular BGP messages,<o:p></o:p></p>
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<p class="MsoNormal">there can be at most 3 kB of attributes, which is ~768 standard, ~384<o:p></o:p></p>
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<p class="MsoNormal">extended, or ~256 large communities. In fact, it is a slightly less due<o:p></o:p></p>
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<p class="MsoNormal">to attribute framing and presence of other attributes than communities.<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">-- <o:p></o:p></p>
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<p class="MsoNormal">Elen sila lumenn' omentielvo<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Ondrej 'Santiago' Zajicek (email: <a href="mailto:santiago@crfreenet.org">
santiago@crfreenet.org</a>)<o:p></o:p></p>
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<p class="MsoNormal">"To err is human -- to blame it on a computer is even more so."<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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