Reddy,
Your proposed changes sound good.
Thanks,
Paul
On 1/27/20 7:33 AM, tirumal reddy wrote:
On Mon, 27 Jan 2020 at 15:36, tirumal reddy <kond...@gmail.com
<mailto:kond...@gmail.com>> wrote:
Hi Paul,
Thanks for the review. Please see inline
On Thu, 23 Jan 2020 at 21:09, Paul Kyzivat <pkyzi...@alum.mit.edu
<mailto:pkyzi...@alum.mit.edu>> wrote:
I am the assigned Gen-ART reviewer for this draft. The General Area
Review Team (Gen-ART) reviews all IETF documents being processed
by the IESG for the IETF Chair. Please treat these comments just
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For more information, please see the FAQ at
<https://trac.ietf.org/trac/gen/wiki/GenArtfaq>.
Document: draft-ietf-dots-architecture-15
Reviewer: Paul Kyzivat
Review Date: 2020-01-23
IETF LC End Date: 2020-01-27
IESG Telechat date: ?
Summary:
This draft is on the right track but has open issues, described
in the
review.
General:
This is a very well written document! Even though I lack any
knowledge
of the subject domain I was generally able to understand it.
I had trouble classifying some of my issues below. I wanted to
make them
be questions. But in a review such as this it makes more sense
to state
them as issues of clarity in the text, since the reader should
ideally
not be left with questions.
Issues:
Major: 0
Minor: 5
Nits: 0
1) MINOR: Resource Ownership:
The 2nd paragraph of section 2.2.2 stresses that it is important
for a
DOTS Server to verify that the DOTS Client owns the resources
over which
it is requesting mitigation.
There seems to be quite a lot hiding behind that requirement. In
particular, how is the server supposed to be in a position to do
that
verification? This seems to require that the server have access to
ownership information. While that may be easy in some cases
(e.g., when
the server is operated by the ISP that assigned the resources to
the
client), in other cases it could be hard. I'd like to see more
discussion of this.
The exact mechanism to validate the resources owned by the DOTS
client domain is deployment-specific. I can add the following
example mechanisms to address your comment:
The exact mechanism for the DOTS servers to validate that the resources
are within the
scope of the DOTS client domain is deployment-specific. For example,
if the DOTS client domain leverages the DDoS mitigation service of
its Internet Transit Provider (ITP), it knows the prefixes assigned
to the DOTS client domain. If the DDoS Mitigation is offered by a
third party DDoS mitigation service provider, and if the resources
are not owned by the requesting domain, it can impose penalties for
violating the service level agreement. Alternatively, the DDoS
mitigation service provider and the DOTS client domain can opt to use
the identifier validation challenges discussed in [RFC8555] and
[I-D.ietf-acme-ip] to identify whether the DOTS client domain
actually controls the resources. Note that the challenges for
validating control of resources must be performed when no attack
traffic is present.
I have modified the above text as follows for better clarity:
The exact mechanism for the DOTS servers to validate that the resources are
within the
scope of the DOTS client domain is deployment-specific. For example,
if the DOTS client domain leverages the DDoS mitigation service of
its Internet Transit Provider (ITP), the ITP knows the prefixes
assigned to the DOTS client domain. However, if the DDoS Mitigation
is offered by a third party DDoS mitigation service provider, it does
not know the resources owned by the DOTS client domain. The DDoS
mitigation service provider and the DOTS client domain can opt to use
the identifier validation challenges discussed in [RFC8555] and
[I-D.ietf-acme-ip] to identify whether the DOTS client domain
actually controls the resources. The challenges for validating
control of resources must be performed when no attack traffic is
present and works only for "dns" and "ip" identifier types. Further,
if the DOTS client lies about the resources owned by the DOTS client
domain, the DDoS mitigation service provider can impose penalties for
violating the service level agreement.
-Tiru
2) MINOR: Scope and lifetime of sessions:
Section 3.1 states that a session can be a signal channel
session or a
data channel session or both. I'm confused about the
relationships here.
If a session can consist of both, how are they related? Is there
some
state that ties them together?
Can a channel survive the loss and reestablishment of a TCP
connection?
Or does the creation of a new connection create a new channel?
What is the act that creates a new channel, and what destroys one?
I'd like to see some more text explaining this.
All above details are discussed in the DOTS signal and data channel
protocol drafts (currently in the RFC editor queue), added the
following like to address your comment:
The DOTS server couples the DOTS signal and data channel sessions using
the DOTS
client identity. The DOTS session is further elaborated in the DOTS
signal channel protocol defined in [I-D.ietf-dots-signal-channel] and
the DOTS data channel protocol defined in
[I-D.ietf-dots-data-channel].
3) MINOR: Feedback for recursive mitigation:
Section 3.2.3 says:
... To maximize
mitigation visibility to the DOTS client, however, the
recursing
domain SHOULD provide recursed mitigation feedback in signals
reporting on mitigation status to the DOTS client. For
example, the
recursing domain's mitigator should incorporate into mitigation
status messages available metrics such as dropped packet or
byte
counts from the recursed mitigation.
This seems to imply that feedback from So to Cn is routed to Mn for
merging with Mn's feedback. That seems to violate the
architecture. Can
the feedback from So be routed by Gn back to Cc?
Yes, clarified text as follows:
For example, the recursing domain's DOTS server should incorporate into
mitigation
status messages available metrics such as dropped packet or byte
counts from the recursed domain's DOTS server.
Can this be clarified?
4) MINOR: Security of recursive mitigation:
The last paragraph of section 3.2.3 says:
Deployment of recursive signaling may result in traffic
redirection,
examination and mitigation extending beyond the initial
bilateral
relationship between DOTS client and DOTS server. As such,
client
control over the network path of mitigated traffic may be
reduced.
DOTS client operators should be aware of any privacy
concerns, and
work with DOTS server operators employing recursive
signaling to
ensure shared sensitive material is suitably protected.
This sounds like hand waving. Am I right in thinking this is
talking
about incorporating the details of recursion in the service
level agreement?
Yes, will add the following line:
Typically there is a contractual Service Level Agreement (SLA)
negotiated among
the DOTS client domain, the recursed domain and the recursing domain
to meet the privacy requirements of the DOTS client domain.
5) MINOR: Normative references:
I was surprised by the scarcity of normative references. I went
looking
for MUSTs referencing RFCs and found three: RFC8612 (DOTS
Requirements),
and RFCs 5389 and 7350 (STUN related). Please consider making these
normative references.
Done (Replaced RFC5389 with
https://tools.ietf.org/html/draft-ietf-tram-stunbis-21).
Cheers,
-Tiru
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