Barry,
Thanks for reviewing. I've committed some changes to the repo and opened
some issues too.
Nits fixed in commit
https://github.com/capport-wg/architecture/commit/f7de70f8dc71dd3f22e2db4208641d1975278ec0
On 2020-04-24 19:35, Barry Leiba wrote:
Thanks for the work in this document. Here’s my AD review; I think a
revised I-D is needed before we go to last call.
General:
Expect comments during IESG Evaluation about the extensive use of BCP
14 key words in an Informational document. I don’t object to it here,
though I do find all the “MAY”s odd (example: “A device MAY query this
API at any time”, rather than “A device may query this API at any
time”), but I do expect some ADs to comment on it.
I've reviewed all upper-case "MAY", and I believe they are used as
intended.
We've allowed the user equipment to participate or not in various ways.
Please check consistency in capitalization of defined terms. The one
that stands out to me as inconsistent is “User Equipment” / “user
equipment”, but I’ve also noticed others, such as “enforcement
device”./User
User Equipment fixed with commit
https://github.com/capport-wg/architecture/commit/274b60a851ca4ef5e2b6f8ccb718ab9ac03d2119
The enforcement device language is inconsistently used, and is not such
a quick fix.
Opened issue #60 https://github.com/capport-wg/architecture/issues/60
Please be consistent about using “URI”, and not “URL”.
Changed all URI to URL in commit
https://github.com/capport-wg/architecture/commit/a9c87ba48aa64564bd9d0e1f21bd82906a2714f4
— Section 1 —
This document standardizes an architecture for implementing captive
portals that provides tools for addressing most of those problems.
We are guided by these principles:
The text that comes before this doesn’t identify anything as problems,
so I don’t see, from what’s written, what “those problems” refers to.
Maybe it would be better to say, “most of the problems that result
from current captive portal mechanisms, guided by these principles:”
or some such?
Right; we removed an earlier reference and forgot to update this.
See commit
https://github.com/capport-wg/architecture/commit/1d91dff5a55b90b22dece05cde13caac97a71225
* Solutions MUST operate at the layer of Internet Protocol (IP) or
above, not being specific to any particular access technology
such
as Cable, WiFi or 3GPP.
3GPP is not an access technology; it’s an SDO (or a consortium of
SDOs). Maybe “mobile telecom”, or “LTE”, or “5G”? Or if you want to
retain 3GPP, maybe “protocols developed in 3GPP”? I think my
preference is “5G” (and it’s only an example anyway).
I think "mobile telecom" suits the intent. See commit
https://github.com/capport-wg/architecture/commit/e95238ccef15d874882ce0f4254b7529ebbd3f39
* End-user devices can be notified of captivity with Captive Portal
Signals in response to traffic. This notification should work
with any Internet protocol, not just clear-text HTTP.
I’m not quite sure what this means. It sounds like it says that the
notification will be in-band with any Internet protocol, which clearly
isn’t possible. I think it’s talking about a separate protocol to
deliver the notification, which can work alongside any Internet
protocol, rather than having it be in-band to clear-text HTTP. Maybe
re-wording that sentence will help.
I believe the intent was, "we are no longer relying on modifying
clear-text HTTP."
Because this is discussed elsewhere in the doc, I propose:
* End-user devices can be notified of captivity with Captive Portal
Signals in response to traffic. This notification works in
response
to any Internet protocol, and is not done by modifying protocols
in-band.
See commit
https://github.com/capport-wg/architecture/commit/b42f9b5242f2d33d2dd163fd04aa5c372cd8442c
— Section 1.2 —
hosts (typically the internet).
Nit: capitalize “Internet”.
done
Captive Portal API: Also known as API. An HTTP API allowing User
Equipment to query its state of captivity within the Captive Portal.
This (and the Abstract) says “an HTTP API”, but there’s nothing at the
architecture level that assumes HTTP, is there? Instantiation may
well be via HTTP, but why does that need to be in the architecture? I
don’t see anything else in this document, apart from these two
definitions, binding the API to HTTP at the architecture level.
Yes, the architecture intentionally says it is HTTP.
No one argued for any alternatives, as far as I know.
Details of the API are left unspecified, so it's still pretty open.
If User Equipment supports the Captive Portal API, it MUST validate
API server TLS certificate (see [RFC2818]).
Nit: “validate the API server’s TLS certificate”
fixed
— Section 2.3 —
The API SHOULD provide evidence
to the caller that it supports the present architecture.
I don’t understand what this means; can you explain?
To me, this means that User Equipment can determine from the
interaction that the API is implementing this architecture vs.
being some random API. I imagine that a version number or content-
type could achieve this.
I've opened https://github.com/capport-wg/architecture/issues/61
to track the issue.
— Section 2.4 —
The Captive Portal Enforcement component restrict the network access
Nit: “restricts”
fixed
* Allows traffic through for allowed User Equipment that has
“Allows traffic through” reads oddly to me. Maybe “Allows traffic to
pass through”? Or “Allows general Internet traffic”?
Changed to
* Allows traffic to pass for User Equipment that is permitted to
use the network and has satisfied the Captive Portal Conditions.
https://github.com/capport-wg/architecture/commit/9da69e46eb77b348ee1cb1f45fe84b49a564268f
— Section 2.6 —
In Figure 1, shouldn’t “Query captivity status” and “Portal user
interface” both have bidirectional arrows?
I think the idea was to show which agent initiated. I'll add a
status response. and bidirectional arrows to the UI.
See commit
https://github.com/capport-wg/architecture/commit/9f817d148353425c43678402350df2267db5db05
— Section 3 —
these interactions, the components must be able to both identify the
user equipment from their interactions with it, and be able to agree
Common problem with “both” and “either”: “be able” is already outside
the scope of “both”, so having it inside for the second case is wrong
(and the comma is unnecessary):
NEW
these interactions, the components must be able to both identify the
User Equipment from their interactions with it and to agree
END
Accepted. Commit
https://github.com/capport-wg/architecture/commit/3a0396e9aca13cedef4b621aaea38b487944c80a
— Section 3.2.1 —
In order to uniquely identify the User Equipment, at most one user
equipment interacting with the other components of the Captive
Portal
MUST have a given value of the identifier.
The way “MUST” is used here feels very odd. I think you mean the MUST
to be related to the uniqueness, not to what components MUST have.
Maybe something like this works better?:
NEW
In order that User Equipment be uniquely identified, a given
identifier MUST NOT represent more than one User Equiment that
interacts with the other components of the Captive Portal.
END
You're right; it's poorly worded. It's just trying to say each UE must
have a unique ID at a point in time. The next point says they can be
recycled. E.g., dynamic IP addresses could be used.
I changed both bullets.
NEW
* Each instance of User Equipment interacting with the Captive
Network MUST be
given an identifier that is unique among User Equipment
interacting at that time.
* Over time, the User Equipment assigned to an identifier value MAY
change. Allowing the
identified device to change over time ensures that the space of
possible
identifying values need not be overly large.
END
Commit
https://github.com/capport-wg/architecture/commit/290d24a648a6ed8b99300c0c2544f9e310d4f574
— Section 3.2.3 —
Since the API Server will need to perform operations which rely on
the identity of the user equipment, such as query whether it is
captive, the API Server needs to be able to relate requests to the
User Equipment making the request.
The API server doesn’t query whether the UE is captive, it responds to
such queries.
Addressed in commit
https://github.com/capport-wg/architecture/commit/8357b07dc309ddcfef8f5ad2dec3c29c89cffaf9
— Section 3.2.4 —
The Enforcement Device will decide on a per packet basis whether it
should be permitted to communicate with the external network.
Nit: hyphenate “per-packet”.
“It” should be referring to the packet, not to the ED, so “whether the
packet should”.
Fixed
— Section 3.3 —
Are we really talking about evaluating individual identifiers here?
Or does this really mean to discuss *methods* of generating or
choosing identifiers?
I believe this is about choice of identifier in a solution/standard.
Opened issue https://github.com/capport-wg/architecture/issues/62
— Section 3.4.3 —
Is this section talking about using a context-free URI as a UE
identifier? It should be clearer about that, if so (and if that’s not
what it’s about, the section is misplaced). There’s nothing in here
that discusses how such identifiers would meet the specified criteria.
I think this is trying to say the server should not be looking at
Ethernet addresses, for example, because the server is probably not
on the same subnet as the User Equipment. So the info needs to be
in the URL.
I hope others can weigh in on this. Created issue
https://github.com/capport-wg/architecture/issues/63
— Section 4 —
Please be consistent about the use of “workflow” vs “work-flow”.
Fixed.
— Appendix A —
method is to attempt to make a HTTP request to a known, vendor
hosted
Nit: hyphenate “vendor-hosted”
DNS queries not using UDP
may potentially fail this test if operating over TCP or DNS over
HTTP.
Nit: it’s “DNS over HTTPS”. But I would say, “DNS queries not using
UDP may potentially fail this test if operating over TCP or HTTPS.”
Thanks. I made some other improvements to that paragraph too.
As committed in
https://github.com/capport-wg/architecture/commit/0a949c6ae536f4db390bfdfd5d795c64ab69783f,
the two bullets are now:
NEW
* Another test that can be performed is a DNS lookup to a known
address
with an expected answer. If the answer differs from the expected
answer,
the equipment detects that a captive portal is present.
DNS queries over TCP or HTTPS are less likely to be modified than
DNS
queries over UDP due to the complexity of implementation.
* The different tests may produce different conclusions, varying by
whether or not the implementation treats both TCP and UDP
traffic,
and by which types of DNS are intercepted.
END
Thanks again Barry. Great points!
-Dave
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