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

Jeffrey Haas <jhaas@pfrc.org> Sun, 20 December 2020 00:16 UTC

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From: Jeffrey Haas <jhaas@pfrc.org>
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Date: Sat, 19 Dec 2020 19:16:50 -0500
Cc: Gyan Mishra <hayabusagsm@gmail.com>, John Scudder <jgs=40juniper.net@dmarc.ietf.org>, "idr@ietf. org" <idr@ietf.org>, Enke Chen <enchen@paloaltonetworks.com>
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To: Robert Raszuk <robert@raszuk.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 19, 2020, at 6:45 PM, Robert Raszuk <robert@raszuk.net> wrote:
> 
> The other day I asked how often BGP is retrying to write to socket in most widely deployed implementations - but did not get any answer :( 
> 

I will publicly state that in each implementation I've worked on over twenty years that handling EAGAIN, EWOULDBLOCK and similar along with dealing with long-lived zero windowing regularly happens.

The majority of the time this is due to simple load issues on the receiver.  It occasionally is related to local resources being scarce (e.g. mbufs).

Once you start getting packet loss on the TCP session, you get these things much more often.

-- Jeff

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