Re: [Tsv-art] Tsvart last call review of draft-ietf-detnet-mpls-over-ip-preof-08

[Balázs Varga A <[e-mail]>]

Hi Oliver,

Thanks for the feedbacks. Replies:
- flowLabel:
The intention was to formulate text being valid for both IPv4 and IPv6. 
However agree, that FlowLabel needs clarification. The following additions
proposed to fix this (to the end of Section "4.4 Flow Aggregation"):
NEW TEXT
   If several Detnet flows are aggregated in a single UDP tunnel, they all need 
   to follow the same path in the network.
END

- Section1.
Agree with comment. We change "IP header" to "IP packet" in the text.

- Section 4.4
Agree with comment. Reference to Fig3. will be added as proposed

All changes will be applied in the next version (uploaded soon).
Let us know if any further changes needed.

Thanks & Cheers
Bala'zs


-----Original Message-----
From: Olivier Bonaventure via Datatracker <[e-mail]> 
Sent: Friday, December 22, 2023 3:05 PM
To: [e-mail]
Cc: [e-mail]; [e-mail]; [e-mail]
Subject: Tsvart last call review of draft-ietf-detnet-mpls-over-ip-preof-08

Reviewer: Olivier Bonaventure
Review result: Ready with Issues

This document has been reviewed as part of the transport area review team's ongoing effort to review key IETF documents. These comments were written primarily for the transport area directors, but are copied to the document's authors and WG to allow them to address any issues raised and also to the IETF discussion list for information.

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I reviewed the document from the transport viewpoint without being an expert in DetNet. As Bruno Decraene mentions in his review, the document seems to be a small modification to RFC9025 that already defines the encapsulation. Is it intended to informational while RFC9025 is standards track.

In Section 5, my main concern is the handling of the FlowLabel field in the
IPv6 header when several Detnet flows are aggregated together. Will these flows use packets with the same IPv6 flowLabel or different flowLabels (one per Detnet flow) ? This would have an impact on ECMP hash and thus influence the packet that different Detnet flows follow. If several Detnet flows are aggregated in a single UDP tunnel, do they all need to follow the same path in the network or not ?

The handling of this FlowLabel must be clarified in a revision of this document.

Details

In Section 1
  However, the DetNet IP
   data plane described in [RFC8939] does not specify how sequencing
   information can be encoded in the IP header.

the end of the sentence (IP header) is misleading. The reader could think that you will change the IP header with an extension, which is clearly not the case.

In 4.4, at the end of

   In the first case, the different DetNet PWs use the same UDP tunnel,
   so they are treated as a single (aggregated) flow at the forwarding
   sub-layer.  At the service sub-layer, each flow uses a different
   Service ID.

I would suggest to provide a reference to Figure 3 that describes this encapsulation.