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

Tony Li <tony.li@tony.li> Wed, 16 December 2020 00:43 UTC

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Sender: Tony Li <tony1athome@gmail.com>
From: Tony Li <tony.li@tony.li>
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Date: Tue, 15 Dec 2020 16:43:31 -0800
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Cc: "Jakob Heitz (jheitz)" <jheitz=40cisco.com@dmarc.ietf.org>, John Scudder <jgs=40juniper.net@dmarc.ietf.org>, Keyur Patel <keyur@arrcus.com>, "idr@ietf.org" <idr@ietf.org>
To: John Heasley <heas@shrubbery.net>
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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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> On Dec 15, 2020, at 4:15 PM, john heasley <heas@shrubbery.net> wrote:
> 
> Could a sender test the liveliness of a peer by attempting to open a
> new session?  would a successful 3-way and commencement of BGP OPEN be
> an indication that it should be more patient, increase its "deadtimer"
> (HOLDTIME < STUCKTIME < PATHETICTIME)?  Clearly the remote has been
> sending bgp keepalives, so perhaps not for all implementations.
> 
> could an implementation more tightly coupled to its tcp use the urgent
> pointer to test liveliness?


Hi Heas,

In modern implementations that are multi-threaded or multi-process, the ability to open 
a new connection only demonstrates liveness of the destination stack. The upper
level thread may not be alive, either due to protocol implementation issues or
OS issues.

Tony

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