Re: [Idr] TCP & BGP: Some don't send terminate BGP when holdtimer expired, because TCP recv window is 0

John Scudder <jgs@juniper.net> Tue, 15 December 2020 22:55 UTC

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From: John Scudder <jgs@juniper.net>
To: Job Snijders <job@sobornost.net>
CC: Christoph Loibl <c@tix.at>, "idr@ietf.org" <idr@ietf.org>, Robert Raszuk <robert@raszuk.net>
Thread-Topic: [Idr] TCP & BGP: Some don't send terminate BGP when holdtimer expired, because TCP recv window is 0
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Date: Tue, 15 Dec 2020 22:55:54 +0000
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Subject: Re: [Idr] TCP & BGP: Some don't send terminate BGP when holdtimer expired, because TCP recv window is 0
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It came up earlier in the discussion that HOLDTIME serves at least two different purposes: neighbor liveness detection, and as a metric of BGP protocol health. If the proposal is adopted, the former use is potentially problematic in deployments where the hold time gets cranked down to a very small number.[*] Of course, you can argue that this is a bad use of the BGP hold time, and that the operator should use BFD instead, but sometimes this isn’t done, for whatever reason. 

Because of this sad state of affairs, it seems to me that if we adopt this proposal, there should be a new hold time introduced, call it TX_HOLDTIME if you like. It could have the same default value as HOLDTIME, but (and this is the important bit) would not inherit any non-default value of HOLDTIME, it would have to be explicitly changed separately.

—John

[*] I assume this is obvious; I’m prepared to detail why if people don’t agree.