Re: [Dart] WGLC: draft-ietf-dart-dscp-rtp-02

<Ruediger.Geib@telekom.de> Mon, 11 August 2014 10:21 UTC

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From: <Ruediger.Geib@telekom.de>
To: <david.black@emc.com>
Date: Mon, 11 Aug 2014 12:21:12 +0200
Thread-Topic: [Dart] WGLC: draft-ietf-dart-dscp-rtp-02
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Subject: Re: [Dart] WGLC: draft-ietf-dart-dscp-rtp-02
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Hi David,

new EF related text has been added in the -01 version. I've copied 
in some text of RFC3246 related to EF remarking and policing below. 
My take:

. remarking of entire flows is an option, but no remarking of 
  packets exceeding EF capacity limits.
- looking at the EF jitter and delay properties, I doubt that 
  shaping is desirable. RFC3246 doesn't mention shaping as part 
  of EF conditioning. I personally wouldn't expect EF shaping 
  in sections where policing is applied. 
- dropping of packets exceeding EF capacity is a MUST, if I 
  interpret RFC3246 correctly.

I suggest to adapt the section of draft-dart-dscp to be more 
precise regarding the optional remarking of EF traffic and to 
remove shaping as a conditioning option if traffic is beyond 
the EF forwarding capacity limit. A Proposal for the final 
sentence:

...exceeds that capacity must be dropped. EF compliant flows may 
be remarked to a different DSCP.

All other new text indicated by the Diff version looks allright.

Regards,

Ruediger



draft-dart-dscp:

3. Expedited Forwarding (EF) [RFC3246] intended for inelastic	
   traffic. Beyond the basic EF PHB, the VOICE-ADMIT PHB [RFC5865]	
   is an admission controlled variant of the EF PHB. Both of these	
   PHBs are based on pre-configured limited forwarding capacity;	
   traffic that exceeds that capacity may be shaped, remarked to a	
   different DSCP, or dropped.

########################################

RFC3246 (three excerpts):

   Packets belonging to a single microflow within the EF aggregate
   passing through a device SHOULD NOT experience re-ordering in normal
   operation of the device.

   Packets marked for EF PHB MAY be remarked at a DS domain boundary
   only to other codepoints that satisfy the EF PHB.  Packets marked for
   EF PHBs SHOULD NOT be demoted or promoted to another PHB by a DS
   domain.

   If the EF PHB is implemented by a mechanism that allows unlimited
   preemption of other traffic (e.g., a priority queue), the
   implementation MUST include some means to limit the damage EF traffic
   could inflict on other traffic (e.g., a token bucket rate limiter).
   Traffic that exceeds this limit MUST be discarded.





-----Ursprüngliche Nachricht-----
Von: Dart [mailto:dart-bounces@ietf.org] Im Auftrag von Ben Campbell
Gesendet: Samstag, 9. August 2014 19:50
An: dart@ietf.org
Cc: Richard Barnes; draft-ietf-dart-dscp-rtp.all@tools.ietf.org; mls.ietf@gmail.com
Betreff: [Dart] WGLC: draft-ietf-dart-dscp-rtp-02

This is a DART Working Group Last Call of draft-ietf-dart-dscp-rtp-02. It's available on the data tracker at the following URL:

https://datatracker.ietf.org/doc/draft-ietf-dart-dscp-rtp/

The WGLC will conclude on 22 August, 2014. Please send your comments to the authors and the DART mailing list. If you've reviewed it and think it's good to go, please say so.

Thanks!

Ben.

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