Re: [tcpm] Meeting Notes // TCP silent close issue

Hi, all,

I noticed the discussion on TCP “silent close”, but didn’t recall seeing any discussion on this topic on the list, so I figured I’d start one.

(Incidentally, a question to the chair: aren’t topics with meeting times slots supposed to have at least been discussed on the list or drafted?)

The issue, AFAICT, is that:
	- an app with a huge number of TCP connections crashes
		- so the OS sends out that huge number of FINs
		- which a burden on the OS and network
	- if the entire OS crashes, no FINs get sent out
		- so why not let that happen when the apps crash?

This is addressed in TIME_WAIT discussions already, e.g.:

T. Faber, J. Touch and W. Yue, "The TIME-WAIT state in TCP and its effect on busy servers," IEEE INFOCOM '99. Conference on Computer Communications. Proceedings. Eighteenth Annual Joint Conference of the IEEE Computer and Communications Societies. The Future is Now (Cat. No.99CH36320), 1999, pp. 1573-1583 vol.3, doi: https://doi.org/10.1109/INFCOM.1999.752180 <https://doi.org/10.1109/INFCOM.1999.752180>

The reason is RFCs 793 and 1122 both require hosts to avoid new connections for the TIME_WAIT period during a reboot, ensuring the safety of the orphan TCP connections on the remote systems.

So, in this case, it would be OK for the OS to avoid sending out the burst of FINs, but *ONLY* if it also ensured those connection identifiers (at least) remained in TIME_WAIT. I.e., it would be possible for the OS to simply put them in TIME_WAIT and then allow the TCBs to be garbage collected either during a scan of TCBs or when a new connection on the same socket pair occurs. That can happen one of two ways:
	- put the TCBs in TIME_WAIT directly (or perform equivalent bookkeeping)
	- have the OS pause new connections for the TIME_WAIT period, i.e., emulating the reboot pause

(I would be glad to assist with documenting that approach if useful).

Joe

—
Joe Touch, temporal epistemologist
www.strayalpha.com

> On Nov 12, 2021, at 2:34 AM, tuexen@fh-muenster.de wrote:
> 
> Dear all,
> 
> a first version of the meeting notes has been uploaded:
> https://datatracker.ietf.org/meeting/112/materials/minutes-112-tcpm-01
> If you have comments, please let the chairs know.
> 
> Thanks a lot to Gorry for taking the notes and anyone improving the
> notes during the meeting!
> 
> Best regards
> Michael
> 
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