Re: [Tsv-art] [Idr] [Last-Call] Tsvart last call review of draft-ietf-idr-tunnel-encaps-19

Susan Hares <> Tue, 10 November 2020 17:14 UTC

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From: "Susan Hares" <>
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Subject: Re: [Tsv-art] [Idr] [Last-Call] Tsvart last call review of draft-ietf-idr-tunnel-encaps-19
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Could you just resubmit a version of the draft?   


We cannot reference in the draft-ietf-idr-tunnel-encaps-20.txt draft unless you have a non-expired draft.  John Scudder and the author team added it as a recommendation, but I had them take it out since the draft was expired.  IESG members do not like “expired” drafts as references. 


Here’s the current -20.txt without your draft reference. 


                 12.  Operational Considerations               


                   A potential operational difficulty arises when tunnels are used, if          

                  the size of packets entering the tunnel exceeds the maximum               

                  transmission unit (MTU) the tunnel is capable of supporting.  This         

                  difficulty can be exacerbated by stacking multiple tunnels, since            

                  each stacked tunnel header further reduces the supportable MTU.  This            

                  issue is long-standing and well-known.  The tunnel signaling provided 

                  in this specification does nothing to address this issue, nor to  

                  aggravate it (except insofar as it may further increase the         

                  popularity of tunneling).            


It would be stronger if we can point to your draft or another TSV draft that explains the details. 


If you and the TSV-art directorate has changes to this section to deal with MTU, it would very helpful  to receive this information this week. 


Cheers, Sue 



From: Idr [] On Behalf Of Joseph Touch
Sent: Monday, November 9, 2020 4:52 PM
To: Susan Hares
Cc: Brian Trammell;;; Last Call; tsv-art
Subject: Re: [Idr] [Tsv-art] [Last-Call] Tsvart last call review of draft-ietf-idr-tunnel-encaps-19


Hi, Sue,


I have a couple of other drafts currently being wrapped up (UDP options, TCP control block sharing bis). The tunnels is next on my list and I hope to finalize a version that we can consider for WGLC by the end of the year.


That doc (even the latest expired version) has the text we’ve recommended elsewhere, e.g., in the TCP core (793) and elsewhere. 



On Nov 9, 2020, at 1:26 PM, Susan Hares <> wrote:


Joe and Brian: 


As the replacement shepherd for draft-ietf-idr-tunnel-encaps-19.txt,  I am looking for the INT area statement on tunnels and MTU in tunnels. 


Your intarea draft seems to have expired without any replacement. 


Where is the latest set of comments on tunnels and MTU issue from INT area? 




From: Joseph Touch [ <>] 
Sent: Thursday, October 15, 2020 9:12 PM
To: Brian Trammell
Cc: tsv-art; Last Call;  <>;  <>
Subject: Re: [Last-Call] Tsvart last call review of draft-ietf-idr-tunnel-encaps-19



On Sep 28, 2020, at 11:32 PM, Brian Trammell via Datatracker < <>> wrote:


First and foremost, I was surprised to find no reference to tunnel or MTU 
anywhere in the document, especially given the guidance in section 6 to
stack tunnels. MTU issues are operationally difficulty in single-tunnel
environments and become more likely to cause problems in multiple-tunnel




This is discussed in detail, with some much more specific terminology, in draft-ietf-intarea-tunnels


In particular, *path MTU* is different from the received MTU, etc. It’s important to get this correct (note the many examples of current standards that do not).



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