L2 MTU issues - is BFD proper solution?
We experienced recently several times issues caused by eg. EAPS path swich in one of our L2 transmission providers (new path MTU was not big enough due to jumbo frames not enabled - that's what they told us, but in fact it does not meter - it's out of our control). From our point of view this situation sucks - we have several BGP sessions, terminated on 2 different BGP routers in different data centers, but problems as descripbed above in just one L2 provider network may cause our all services are not fully operational - especially when afeccted BGP sessions provides best routes for some popular services like FB, YT or… redtube.com ;). So, the question: is BFD able to detect broken L2 MTU and if detected - disable affected BGP sessions? If not BFD, any other ideas? It's possible to detect L2 problems outside bird and then disable protocols, but this may be complicated and error prone, so in fact - i do not want to to that. -- A: Because it messes up the order in which people normally read text. Q: Why is top-posting such a bad thing? Bartosz Radwan
On Thu, Jul 03, 2014 at 11:43:39AM +0200, Bartosz Radwan wrote:
We experienced recently several times issues caused by eg. EAPS path swich in one of our L2 transmission providers (new path MTU was not big enough due to jumbo frames not enabled - that's what they told us, but in fact it does not meter - it's out of our control).
From our point of view this situation sucks - we have several BGP sessions, terminated on 2 different BGP routers in different data centers, but problems as descripbed above in just one L2 provider network may cause our all services are not fully operational - especially when afeccted BGP sessions provides best routes for some popular services like FB, YT or??? redtube.com ;).
So, the question: is BFD able to detect broken L2 MTU and if detected - disable affected BGP sessions?
No. BFD sessions use very small packets, so they most likely do not notice problems specific to MTU. -- Elen sila lumenn' omentielvo Ondrej 'Santiago' Zajicek (email: santiago@crfreenet.org) OpenPGP encrypted e-mails preferred (KeyID 0x11DEADC3, wwwkeys.pgp.net) "To err is human -- to blame it on a computer is even more so."
Hi
3 jul 2014 kl. 11:43 skrev Bartosz Radwan <b.radwan@citypartner.pl>:
We experienced recently several times issues caused by eg. EAPS path swich in one of our L2 transmission providers (new path MTU was not big enough due to jumbo frames not enabled - that's what they told us, but in fact it does not meter - it's out of our control).
From our point of view this situation sucks - we have several BGP sessions, terminated on 2 different BGP routers in different data centers, but problems as descripbed above in just one L2 provider network may cause our all services are not fully operational - especially when afeccted BGP sessions provides best routes for some popular services like FB, YT or… redtube.com ;).
So, the question: is BFD able to detect broken L2 MTU and if detected - disable affected BGP sessions?
If not BFD, any other ideas?
ISIS hello packets are padded to MTU or close to it. It might not be useful for you, but anyway. /Tias
It's possible to detect L2 problems outside bird and then disable protocols, but this may be complicated and error prone, so in fact - i do not want to to that.
-- A: Because it messes up the order in which people normally read text. Q: Why is top-posting such a bad thing? Bartosz Radwan
Hello, On Aug 15, 2014, at 12:00 AM, Mathias Wolkert <tias@netnod.se> wrote:
Hi
3 jul 2014 kl. 11:43 skrev Bartosz Radwan <b.radwan@citypartner.pl>:
We experienced recently several times issues caused by eg. EAPS path swich in one of our L2 transmission providers (new path MTU was not big enough due to jumbo frames not enabled - that's what they told us, but in fact it does not meter - it's out of our control).
From our point of view this situation sucks - we have several BGP sessions, terminated on 2 different BGP routers in different data centers, but problems as descripbed above in just one L2 provider network may cause our all services are not fully operational - especially when afeccted BGP sessions provides best routes for some popular services like FB, YT or… redtube.com ;).
So, the question: is BFD able to detect broken L2 MTU and if detected - disable affected BGP sessions?
BFD does not send MTU frames, so it would not be able to.
If not BFD, any other ideas?
ISIS hello packets are padded to MTU or close to it.
It might not be useful for you, but anyway.
/Tias
It's possible to detect L2 problems outside bird and then disable protocols, but this may be complicated and error prone, so in fact - i do not want to to that.
You could write a script that would send pings at MTU with the DF bit set and react to failed responses. David
-- A: Because it messes up the order in which people normally read text. Q: Why is top-posting such a bad thing? Bartosz Radwan
participants (4)
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Bartosz Radwan -
David Sinn -
Mathias Wolkert -
Ondrej Zajicek