From: "Liubing (Remy)" <remy.liubing@huawei.com>
To: roll <roll@ietf.org>
Thread-Topic: Comments on draft-ietf-roll-dao-projection-09
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Date: Mon, 23 Dec 2019 09:22:48 +0000
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Subject: [Roll] Comments on draft-ietf-roll-dao-projection-09
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Hello DAO-projection authors,

I've read the latest version of the draft. Great efforts! Please find my co=
mments below for your consideration.

1. Why do you choose to extend RPL instead of designing a new separate prot=
ocol to realize the establishment of a path? Technically, extending RPL wor=
ks for sure. But if you look outside the IOT domain, the PCE have a separat=
e protocol, i.e. PCEP, to establish the paths on the devices.=20

2. The titles of the subsections in section 6 are misleading. When I looked=
 at the title "Non-storing/Storing mode projected route", I misunderstood t=
hem into "Route projection in non-storing/storing mode". Actually, until I =
reached at the appendix, I realized that they means the projected route its=
elf is source-routed or hop-by-hop (no matter strict or loose).  Do you thi=
nk it is necessary to add some clarification or to change the titles?

3. The following specification is not accurate in some cases: " In the unco=
mpressed form the source of the packet would be self, the destination would=
 be the first Via Address in the SRVIO, and the SRH would contain the list =
of the remaining Via Addresses and then the Target".
It is true if RPL is running in storing mode, otherwise, another encapsulat=
ion takes place to indicate the explicit route to the via address, just lik=
e you have said in the preceding paragraph. And the said explicit route sho=
uld be projected as well. Please consider combining the two paragraphs to m=
ake it correct.=20

4. You've mentioned that the root can be the egress of a path. Does it mean=
 that the upward route needs to be projected in some cases, given the fact =
that most of the examples given in the draft are downward or transversal ro=
utes? Could you give an example on that situation?=20

Best regards,
Remy