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

[Olivier Bonaventure via Datatracker <[e-mail]>]

Reviewer: Olivier Bonaventure
Review result: Ready with Issues

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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.