[Dots] AD review of draft-ietf-dots-use-cases-17

Benjamin Kaduk <kaduk@mit.edu> Tue, 02 July 2019 22:37 UTC

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Date: Tue, 2 Jul 2019 17:36:54 -0500
From: Benjamin Kaduk <kaduk@mit.edu>
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Subject: [Dots] AD review of draft-ietf-dots-use-cases-17
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First off, a few housekeeping items:

(1) This document lists seven authors, and per RFC 7322 I/the IESG needs
to specially consider this and essentially make an exception to have
more than five authors.  Can you please confirm that all listed authors
have made substantial contributions, so that I can take that to the IESG
and get it approved?

(2) The shepherd writeup indicates that three authors (Stefan, Bob, and
Nik) have not indicated conformance with BCPs 78 and 79.  I don't think
I can issue the IETF LC until that gets straightened out, so please
confirm that we're all squared away!

(3) Recently the IESG has been trying to exert some gentle backpressure
against publishing Informational use-cases/requirements drafts, when they
serve only as input to future protocol specifications and do not have
lasting archival value on their own.  I do see in the shepherd writeup that
the working group did reach consensus to publish this document and think
there's enough value in it to be worth publishing; I just mention this so
that people aren't surprised if the IESG evaluation comes back with
questions about whether we should be publishing the document at all.

Other than those, the document is generally in good shape; there's just
a few substantive questions buried in the editorial nits.

On to the section-by-section comments:

Section 2

   o  DDoS Mitigation Service: designates a DDoS mitigation service
      provided to a customer and which is scoped to mitigate DDoS
      attacks.  [...]

I don't really think that using the lowercase-'s' version to define the
uppercase-'S' version of the term is going to help anyone.

Section 3.1

It's a little surprising that we have the two bullet points near the top
about the enterprise DMS acting as a DOTS client for the first kind of
service but as a DOTS server for the second kind, but then we never seem
to talk about that second kind of service again in the document.
Perhaps we should just explicitly say that it's similar to the first
kind and not covered further?

   When the enterprise DMS detects an inbound DDoS attack targeting its
   resources ( e.g. servers, hosts or applications), it immediately
   begins a DDoS Mitigation.

I'd consider clarifying that this mitigation is entirely local within
the enterprise, so that contacting the ITP in the next step is a clear
escalation.

   related information.  Once the DDoS attack has ended, or decreased to
   the certain level that the DOTS client can handle by itself, the DOTS
   server signals the enterprise DMS DOTS client that the attack has
   subsided.

I think it's the enterprise DMS that is handling the attack, not the
DOTS client directly...

   The enterprise DMS then requests the ITP to terminate the DDoS
   Mitigation.  The DOTS server on the ITP receives this request and

... but this one is the DOTS client.

   o  (a) A DDoS attack is initiated against resources of a network
      organization which has deployed a DOTS-capable DMS - typically a
      DOTS client.

We probably want to reiterate in a parenthetical "network organization
(here, the enterprise)" the terminology we're using.

   o  (d) The DOTS server which receives the DOTS Mitigation request
      determines that it has been configured to honor requests from the
      requesting DOTS client, and honored its DDoS Mitigation by
      orchestrating its DMS.

nit: I think s/honored/honors/ to stay in the present tense.

   o  (e) While the DDoS Mitigation is active, DOTS server regularly
      transmits DOTS DDoS Mitigation status updates to the DOTS client.

nit: "the DOTS server" or "servers regularly transmit".

Section 3.2

   As such, this use case likely to match large enterprises or large
   data centers, but not exclusively.  [...]

nit: "is likely"

   In this scenario, an Enterprise Network has entered into a pre-
   arranged DDoS mitigation assistance agreement with one or more other
   DDoS Mitigation Service Providers in order to ensure that sufficient
   DDoS mitigation capacity and/or capabilities may be activated in the
   event that a given DDoS attack threatens to overwhelm the ability of
   a given DMS to mitigate the attack on its own.

We could perhaps say "overwhelm the ability of the enterprise's or any
other given DMS" since in most cases the enterprise DMS is the one at
risk of first being overwhelmed.

Is the fact that the C<-->S DOTS traffic does not go through the ITP in
Figure 3 an intentional change from Figure 2 (in that they are expected
to be communicating "out of band" or not through the enterprise's normal
transit)?  Some readers might see this and get confused if this
communication is still supposed to be going along the regular transit
path.

Section 3.3

   In this use case, one or more DDoS telemetry systems or monitoring
   devices monitor a network - typically an ISP network, an Enterprise
   network, or a data center.  Upon detection of a DDoS attack, these
   DDoS telemetry systems alert an orchestrator in charge of
   coordinating the various DMS within the domain.  [...]

nit: do we have a standard plural form for "DMS"?  (Is it just "DMS"?)

   ITP.  DDoS Mitigation System selection and DDoS Mitigation technique
   may depends on the type of DDoS attack.  In some case, a manual

nit: "techniques" plural

   The communication between a network administrator and the
   orchestrator is also performed using DOTS.  The network administrator
   via its web interfaces implements a DOTS client, while the
   Orchestrator implements a DOTS server.

nit: as written, this is saying that the network administrator has a
web interface.  I think "its" is supposed to refer to something else.

nit: Figure 4 lists "DDoS mitigation systems" in both the interprise and
the ITP, but only the enterprise side has a "stack" of boxes to indicate
there is more than one.

   These systems are configured so that when an event or some
   measurement indicators reach a predefined level to send DOTS
   mitigation request to the orchestrator.  The DOTS mitigation request

nit: the grammar here is a bit off; I think s/to send DOTS mitigation
request/they send a DOTS mitigation request/ would fix it.

   Upon receipt of the DOTS mitigation request from the DDoS telemetry
   system, the orchestrator responds with an acknowledgment, to avoid
   retransmission of the request for mitigation.  The orchestrator may
   begin collecting additional fined grain and specific information from

nit: "fine-grained"

   and provide an analysis of the event.  Eventually, the orchestrator
   may ask additional information to the DDoS telemetry system, however,
   the collection of these information is out of scope.

nit: s/ask additional information to/ask for additional information
from/
nit: semicolon before "however" instead of comma
nit: "this information"

   Upon receiving a request to mitigate a DDoS attack performed over a
   target, the orchestrator, may evaluate the volumetry of the attack as

nit: no comma after "the orchestrator"

   well as the value that represent the target.  The orchestrator may

nit: "the value that the target represents"

                          When DDoS Mitigation is requested, the status
   indicates the DDoS Mitigation is starting while not effective.  The
   DOTS client of the orchestrator will later be notified that the DDoS
   Mitigation is effective.

I'm not entirely sure what this last sentence is trying to say.

   Orchestration of the DDoS mitigation systems works similarly as
   described in Section 3.1.  The orchestrator indicates with its status
   whether the DDoS Mitigation is effective.

Is this intended to specifically refer to the external (ITP) DMS?

Also, my understanding is that for this interaction the orchestrator is
acting as a DOTS client, but the rest of the document only has status
messages being generated by the DOTS server.  Am I confused?

Section 4

It feels incomplete to list three primary attacks but only discuss
mitigations for two of them.  Perhaps "preconfigured mitigation steps to
take on the loss of keepalive traffic can partially mitigate signal
blocking, but in general it is impossible to comprehensively defend
against an attacker that can selectively block any or all traffic".

Section 6

Is Med's name spelled correctly?


Thanks,

Ben