Re: [Teas] WG Last Call: draft-ietf-teas-pce-native-ip-06

[Dhruv Dhody <[e-mail]>]

Hi WG, Authors,

As an experimental framework based on RFC 8735, I am fine with
publication of this document. But I do have comments and thoughts on
what is missing in this I-D. Request authors and shepherd to consider
them before we ship this out of the WG.

(1) I find the term "Dual/Multi-" used throughout in this document to
be bit weird. Well 'multi-' includes 'dual-' :)

(2) We need to add some text that describes the experimental nature of
this work. Something in line with

   The procedures described in this document are experimental.  The
   experiment is intended to enable research for the usage of PCE in
   native IP scenarios.  For this purpose, this document describe the
   CCDR framework and the PCEP extension is specified in
   [I-D.ietf-pce-pcep-extension-native-ip].

(3) Section 1

We should be clear on where are these requirements coming from. Can we
say that they are based on the scenarios listed in RFC 8735(?), so it
does not read out of place. More importantly, the list is a mix of
technology choices, deployment limitations, and abstract philosophy;
calling them requirement may be a stretch. Further,

   o  No complex Multiprotocol Label Switching (MPLS) signaling
      procedures.

    Why signaling alone? Isn't data-plane as native IP, one of the key
    requirements?

   o  End to End traffic assurance, determined Quality of Service (QoS)
      behavior.

    Should we specify that this in the control plane?

    o  Flexible deployment and automation control.

    IMHO too generic (and marketing).

Also, please describe CCDR in the Introduction. Jumping directly into
example in section 4 is not right.

(4) If you don't use RFC 2119 keywords, then remove section 2.

(5) Section 4,

- you should be explicit that IP11, IP12 are IP prefix.
- you need to describe the term "explicit peer routes"? How is it
  different from a static route?
- I think we should say that section 4 is only for illustrative
  purpose
- I am not sure why the description is in terms of address pairs
  (IP11, IP21) and (IP12, IP22) - what happens if one sends traffic
  from IP11 to IP22? I guess the forwarding would be based on
  destination IP22 and the traffic would be sent to the link
  associated with it? Doesn't it make more sense to describe things in
  terms of IP prefix?

(6) Section 6, you have -

   It is almost impossible to provide an End-to-End (E2E) path with
   latency, jitter, packet loss constraints to meet the above
   requirements in large scale IP-based network via the distributed
   routing protocol...

Well flex-algo to some extent could do this. So maybe reword this...
Also, consider avoiding using term flow and focus on just prefix.

(7) Section 7, Add some text on -

- the loopback address used for the multi-BGP session. Do they exist
  at edge routers/RR already and PCE selects them?
- how does PCE learn the prefix and QoS requirement

(8) Section 9.2,

   If one node on the optimal path is failed, the priority traffic will
   fall over to the best-effort forwarding path.  One can even design
   several assurance paths to load balance/hot-standby the priority
   traffic to meet the path failure situation, as done in MPLS Fast
   Reroute (FRR).

Not sure how MPLS FRR is applicable here (perhaps IP FRR for static
routes)?

(9) Section 10,

   The PCE should have the capability to calculate the loop-free E2E
   path upon the status of network condition and the service
   requirements in real time.

This is true for any PCE, don't think it belongs in Security
consideration. This section needs to be improved as one can use PCEP
to create bogus BGP sessions and we need to consider what would be
impact on that. Further what would be the impact of incorrect prefix,
can this be used to misdirect traffic.

(10) Other considerations - Few things that are missing -

- PCE and PCEP considerations - Stateful nature of PCE, path state at
  the PCE, synchronization of the state etc
- Multi-domain case - as that is listed as a key benefit of CCDR.
- Impact of dynamic BGP session created based on CCDR.
- Impact of "explicit peer routes" and their interaction with other
  routes.
- Document does not mention removal and modification at all
- Comparison to other techniques is distributed in various section,
  maybe collect them in appendix


(11) Nits
- I suggest following the abbreviation guideline as per
  https://www.rfc-editor.org/materials/abbrev.expansion.txt; I see
  some well-known terms (BGP, PCE) expanded. Look for (*) in the link.
- Remove "Draft" in section 1 - "Draft [RFC8735] describes..."
- Section 1, s/differentiation/different/
- Not a good idea to have Lo0, Lo1 on both R1 and R2 - perhaps Lo11,
  Lo12 and Lo21, Lo22?
- Add reference for BGP stuff like RR

Thanks!
Dhruv