[Idr] ietf-104 responding to Rüdiger's comment about bfd strict mode
Jeffrey Haas <jhaas@pfrc.org> Thu, 28 March 2019 11:19 UTC
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Date: Thu, 28 Mar 2019 07:18:33 -0400
From: Jeffrey Haas <jhaas@pfrc.org>
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Subject: [Idr] ietf-104 responding to Rüdiger's comment about bfd strict mode
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In IETF 104, Rüdiger responded that he'd like to see BFD in BGP be used to prove that a link is "stable enough" before we even announce routes. As I mentioned at the mic, the critical issue is that we have varying implementations of when BFD must be up in differing implementations with regard to the BGP FSM. E.g. Up before we start the transport session (Connect), or Up before we transition to Established, or Up after Established. The proposal from Mercia and Acee effective summ to "if BFD strict negotiated, wait for BFD to come up before transition to Established". This provides a common point for implementations to interoperate. There is still potentially issue with older implementations that relied on BFD to be Up before BGP starts its TCP session; however upon supporting this feature we implicitly add an option where the behavior is changed. Back to Rüdiger's point: He has a desire that the session is stable before we start announcing routes. In BGP RFC parlance, we do not exchange our routes in the Update-Send process until stability is declared. While this is doable, how do you negotiate what level of stability is desired? BFD, without extensions, mostly will simply declare the session Down when enough packets are lost. If the link quality is very bad, this should happen quite quickly. If the link quality is partially lossy, BFD doesn't help. (However, see https://tools.ietf.org/html/draft-am-bfd-performance-00) -- Jeff
- Re: [Idr] ietf-104 responding to Rüdiger's commen… Robert Raszuk
- Re: [Idr] ietf-104 responding to Rüdiger's commen… Robert Raszuk
- [Idr] ietf-104 responding to Rüdiger's comment ab… Jeffrey Haas
- Re: [Idr] ietf-104 responding to Rüdiger's commen… Rajiv Asati (rajiva)
- Re: [Idr] ietf-104 responding to Rüdiger's commen… Acee Lindem (acee)
- Re: [Idr] ietf-104 responding to Rüdiger's commen… Robert Raszuk
- Re: [Idr] ietf-104 responding to Rüdiger's commen… Jeffrey Haas
- Re: [Idr] ietf-104 responding to Rüdiger's commen… Robert Raszuk
- Re: [Idr] ietf-104 responding to Rüdiger's commen… Jeffrey Haas