Hi RIS team, See below. Any comments or ideas? Olaf helped with us on myASn in the past, so we should say a little bit more than just a standard answer. Henk -------- Original Message -------- Subject: Quagga question Date: Tue, 27 May 2008 09:42:26 +0300 From: Olaf Maennel <olaf@maennel.net> To: Henk Uijterwaal <henk@ripe.net> CC: Ashley Flavel <ashley.flavel@adelaide.edu.au> Dear Henk, how are you? haven't heard from you for a while now... Hope everything is okay?! Ashley, one of my colleagues in Australia, was looking into errors in quagga and suspects that updates could sometimes be reordered if they arrive within a very short time (= not written to file in chronological order). Are you aware of anything like that? Thanks, olaf On 27/05/08 4:44 AM, "Ashley Flavel" <ashley.flavel@adelaide.edu.au> wrote:
Hi guys,
I'm looking at making the CleanBGP stuff usable by others (including myself). Just found an interesting 'feature' of the data. I'm not sure if it is a bug in the Quagga route monitor collecting the data, but this is what is happening...
If two updates are received at the same timestamp for the same prefix, I have been assuming that the ordering of them in the file dictates which order they were received in. However, this is not necessarily the case :( I have found cases where a prefix is updated twice in the same second and the ordering of the updates is incorrect in the files (I know this as I have tables which tell me the entry which is present). It gets worse... I have also found cases where updates with a gap of 1 second are recorded in the incorrect order.
I have a way to deal with this... I keep a history of the last update prior to the current update (if it is within 5 seconds -- I could make this larger if I needed to). Then when I compare my constructed table at a timestamp, if a difference occurs, I can check if this is as a result of the ordering of 'almost simultaneous' updates.
So... although this is annoying -- it also adds to the 'things you need to be careful about' when analysing the data.
Ash
-- ------------------------------------------------------------------------------ Henk Uijterwaal Email: henk.uijterwaal(at)ripe.net RIPE Network Coordination Centre http://www.amsterdamned.org/~henk P.O.Box 10096 Singel 258 Phone: +31.20.5354414 1001 EB Amsterdam 1016 AB Amsterdam Fax: +31.20.5354445 The Netherlands The Netherlands Mobile: +31.6.55861746 ------------------------------------------------------------------------------ Is one of the choices leaving the office open? Alan Greenspan on the next elections