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<p><font size="2" color="navy" face="Arial">Interesante! <br>
No percibimos problemas.<br>
Espero que lo hayan probado exhaustivamente antes de ponerlo en operación . . . <br>
Saludos,<br>
Alvaro. </font></p>
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<font face="Tahoma" size="2"><b>De</b>: lacnog-bounces@lacnic.net <lacnog-bounces@lacnic.net>
<br>
<b>Para</b>: Latin America and Caribbean Region Network Operators Group <lacnog@lacnic.net>
<br>
<b>Enviado</b>: Fri Aug 27 16:57:56 2010<br>
<b>Asunto</b>: [lacnog] Problemas de ruteo con nuevo atributo <br>
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<div><span class="Apple-tab-span" style="white-space:pre"></span>Creo que este mensaje de RIPE NCC es importante para la comunidad de ruteo. No se si a alguno le haya impactado en sus operaciones.</div>
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<div>Slds</div>
<div>asn</div>
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Date: Fri, 27 Aug 2010 11:42:17 -0700 (PDT)<br>
From: Lucy Lynch <<a href="mailto:llynch@civil-tongue.net">llynch@civil-tongue.net</a>><br>
Subject: Re: Did your BGP crash today?<br>
To: Grzegorz Janoszka <<a href="mailto:Grzegorz@Janoszka.pl">Grzegorz@Janoszka.pl</a>><br>
Cc: <a href="mailto:nanog@nanog.org">nanog@nanog.org</a><br>
Message-ID: <<a href="mailto:alpine.BSF.2.00.1008271141540.79214@hiroshima.bogus.com">alpine.BSF.2.00.1008271141540.79214@hiroshima.bogus.com</a>><br>
Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed<br>
<br>
FYI:<br>
<br>
----------------------------------------------------------------------<br>
Dear Colleagues,<br>
<br>
On Friday 27 August, from 08:41 to 09:08 UTC, the RIPE NCC Routing<br>
Information Service (RIS) announced a route with an experimental BGP<br>
attribute. During this announcement, some Internet Service Providers<br>
reported problems with their networking infrastructure.<br>
<br>
Investigation<br>
--------------<br>
<br>
Immediately after discovering this, we stopped the announcement and<br>
started investigating the problem. Our investigation has shown that the<br>
problem was likely to have been caused by certain router types<br>
incorrectly modifying the experimental attribute and then further<br>
announcing the malformed route to their peers. The announcements sent<br>
out by the RIS were correct and complied to all standards.<br>
<br>
The experimental attribute was part of an experiment conducted in<br>
collaboration with a group from Duke University. This involved<br>
announcing a large (3000 bytes) optional transitive attribute, using a<br>
modified version of Quagga. The attribute used type code 99. The data<br>
consisted of zeros. We used the prefix 93.175.144.0/24 for this and<br>
announced from AS 12654 on AMS-IX, NL-IX and GN-IX to all our peers.<br>
<br>
Reports from affected ISPs showed that the length of the attribute in<br>
the attribute header, as seen by their routers, was not correct. The<br>
header stated 233 bytes and the actual data in their samples was 237<br>
bytes. This caused some routers to drop the session with the peer that<br>
announced the route.<br>
<br>
We have built a test set-up which is running identical software and<br>
configurations to the live set-up. From this set-up, and the BGP packet<br>
dumps as made by the RIS, we have determined that the length of the data<br>
in the attribute as sent out by the RIS was indeed 3000 bytes and that<br>
all lengths recorded in the headers of the BGP updates were correct.<br>
<br>
Beyond the RIS systems, we can only do limited diagnosis. One possible<br>
explanation is that the affected routers did not correctly use the<br>
extended length flag on the attribute. This flag is set when the length<br>
of the attribute exceeds 255 bytes i.e. when two octets are needed to<br>
store the length.<br>
<br>
It may be that the routers may not add the higher octet of the length to<br>
the total length, which would lead, in our test set-up, to a total<br>
packet length of 236 bytes. If, in addition, the routers also<br>
incorrectly trim the attribute length, the problem could occur as<br>
observed. It is worth noting that the difference between the reported<br>
233 and 237 bytes is the size of the flags, type code and length in the<br>
attribute.<br>
<br>
We will be further investigating this problem and will report any<br>
findings. We regret any inconvenience caused.<br>
<br>
Kind regards,<br>
<br>
Erik Romijn<br>
<br>
Information Services<br>
RIPE NCC<br>
_______________________________________________<br>
tech-l mailing list<br>
<a href="mailto:tech-l@ams-ix.net">tech-l@ams-ix.net</a><br>
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<br>
<br>
<br>
- Lucy<br>
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