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

[Jeff Tantsura <[e-mail]>]

I’m with Tony, RST without Notification would be anything but useful/helpful for troubleshooting.
Doing both, and in that particular order would ensure consistency, and if Notification does make it through - assist with troubleshooting.

Regards,
Jeff

> On Dec 11, 2020, at 12:00, Tony Li <[e-mail]> wrote:
> 
> 
> Hi Job,
> 
> 
>> Does everyone agree BGP-4 sessions MUST be terminated using a TCP RST
>> (instead of a BGP-4 Cease NOTIFICATION) if the peer has indicated for
>> the duration of the Hold Timer that the TCP receive window is zero?
> 
> 
> Not quite.  I agree that the session should be terminated if the TCP receive window
> is zero for the duration of the Hold Timer. Clearly the receiver is stuck and the
> receiver should be terminating the connection. For robustness, it makes sense that
> the transmitter also close the connection. 
> 
> I would prefer to see the transmitter do both: queue a NOTIFICATION and reset
> the TCP connection. Yes, the NOTIFICATION will probably never make it out. The advantage
> of doing it this way is that the code path for errors will be more consistent: always send
> a NOTIFICATION before the RST. This code path is also likely to send appropriate signaling to
> the management plane. This is also useful in debugging: if you go through the
> message queue, the NOTIFICATION will be sitting there in the queue.
> 
> 
>> Perhaps RFC 4271 Section 6.5 should be amended as following:
>> 
>> OLD:
>>   If a system does not receive successive KEEPALIVE, UPDATE, and/or
>>   NOTIFICATION messages within the period specified in the Hold Time
>>   field of the OPEN message, then the NOTIFICATION message with the
>>   Hold Timer Expired Error Code is sent and the BGP connection is
>>   closed.
>> 
>> NEW:
>>   If a system does not receive (or is unable to send) successive
>>   KEEPALIVE, UPDATE, and/or NOTIFICATION messages within the period
>>   specified in the Hold Time field of the OPEN message, then the
>>   NOTIFICATION message with the Hold Timer Expired Error Code is sent
>>   and the BGP connection is closed. If the NOTIFICATION message cannot
>>   be send the BGP connection is closed.
> 
> 
> Your proposed text does what I prefer, not what you suggested above. I would suggest
> two edits: (1) remove then parentheses in the first sentence, they are unnecessary, and
> (2) remove the last sentence.
> 
> Regards,
> Tony
> 
> 
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