Re: [OPSAWG] Eric Rescorla's Discuss on draft-mm-wg-effect-encrypt-17: (with DISCUSS and COMMENT)

[Kathleen Moriarty <[e-mail]>]

Hi Eric,

Thanks for your feedback, responses are inline.

FYI - I posted another version, but expect at least one more iteration
after this version with additional comments and the ones we haven't
gotten to yet.

On Thu, Feb 8, 2018 at 12:04 AM, Eric Rescorla <[e-mail]> wrote:
> Eric Rescorla has entered the following ballot position for
> draft-mm-wg-effect-encrypt-17: Discuss
>
> When responding, please keep the subject line intact and reply to all
> email addresses included in the To and CC lines. (Feel free to cut this
> introductory paragraph, however.)
>
>
> Please refer to https://www.ietf.org/iesg/statement/discuss-criteria.html
> for more information about IESG DISCUSS and COMMENT positions.
>
>
> The document, along with other ballot positions, can be found here:
> https://datatracker.ietf.org/doc/draft-mm-wg-effect-encrypt/
>
>
>
> ----------------------------------------------------------------------
> DISCUSS:
> ----------------------------------------------------------------------
>
> I have completely re-reviewed the latest version. First, I want to
> thank you for toning down some of the material that I was concerned
> about.
>
> Unfortunately, the fundamental concern that motivated my DISCUSS
> remains: I do not believe that this document matches the consensus
> of the IETF community.
>
> Specifically, this document takes at face value a large number of
> claims about the necessity/value of certain practices that either are
> controversial within the IETF or that there is, I believe, rough
> consensus to be actively bad, and that in many cases, encryption is
> specifically designed to prevent. I have noted a number of these
> below, but I do not believe that this is an exhaustive list (going
> through my previous DISCUSS, I see that I noted a number of these but
> that still appear to be unaddressed.)

In the previous round of IESG reviews, the IESG concluded that framing
upfront was the preferred approach to make it clear that not all cited
practices are ones the IETF consider valid.  This was done in the
updated introduction.

Please respond to the discussion points as I believe your additional
points have been addressed to also make these points again in the
document.  In a couple of places, we have questions to make sure your
concern is understood.

>
>
> DISCUSS
>    session encryption that deployed more easily instead of no
>    encryption.
>
> I think I understand what you are saying here, but the term
> "breakable" seems very unfortunate, especially in the context of this
> document. The only such shift I am aware of that has received
> acceptance in IETF is one from always requiring fully authenticated
> encryption to allowing unauthenticated encryption, which you document
> in the next paragraph. I recognize that there are other perspectives
> (e.g., those in draft-rhrd) but those are pretty far from IETF
> consenus. Accordingly, I think you should remove this sentence.

Opportunistic security was well discussed, so that was likely top of
mind for you when reading this draft. However there are other areas
where the IETF decided breakable encryption was better than none in
recent years.  Another adopted and published example is in the mail
community.  Deprecating MD5 was deemed to be too hard because of
support in a particular library.  We had lengthy discussions about
this for RFC7627 (see sect 6.2) and related drafts, now published
RFCs.

This sentence had nothing to do with the drafts that are not WG drafts
in the TLS WG, but real use cases of published RFCs where deprecated
crypto is still accepted despite efforts to correct that in addition
to the acceptance of the OS approach in multiple session encryption
protocols.  The support tools and use cases don't always drive the
best solution where we have strong crypto everywhere as you have also
noted on recent draft reviews, now published RFCs.

>
>
>    motivation outside of privacy and pervasive monitoring that are
>    driving end-to-end encryption for these content providers.
>
> This section seems kind of confusing, at least as applied to
> HTTP. There are three kinds of cache in HTTP:
>
> - Reverse proxy caches (the kind CDNs run)
> - Explicit forward proxy caches
> - "Transparent" intercepting caches
>
> The first of these move to HTTPS just fine and that's typically how
> CDNs do it.  Explicit forward proxy caches are largely going away, but
> part of the point of this kind of end-to-end encryption is to hide
> data from those caches.

Sure, that point was made in the draft and cleared up a little further
from Benjamin K's review.  The business risk associated with not
controlling your content was more explicitly stated for CDNs who have
moved to an e2e approach.

Here's the updated sentence:
   The business risk of losing control of content is a motivation outside
   of privacy and pervasive monitoring that are driving end-to-end
   encryption for these content providers.

> Transparent intercepting caches that the user
> didn't opt into are a bad thing, so having them go away is a positive.

The text says authorized parties, so this is referring to caches where
there is an agreement in place for this usage.  CDN's that wish to
block this behavior have the option to require e2e.  That trend alone
may be enough to kill this type of service offering.  I don't see why
it shouldn't be mentioned in terms of it's current use.  What change
are you looking to see here?

>
>    document existing practices, the development of IETF protocols
>    follows the guiding principles of [RFC1984] and [RFC2804].
>
> This is pretty opaque in this context. It should explicitly state that
> the IETF's position is that we do not engineer for these use cases,
> not just to cite the RFCs.

We can add the following (or suggest something else):

"and explicitly do not support tools and methods that could be used
for wiretapping and censorship."

>
>
>    based billing, or for other reasons, possibly considered
>    inappropriate by some.  See RFC7754 [RFC7754] for a survey of
>    Internet filtering techniques and motivations.  This section is
>
> I don't think this accurately represents the RFC, which makes clear
> that the IAB consensus is that filtering is bad:
>
> " From a technical perspective, there are no perfect or even good
> solutions -- there is only least bad.  On that front, we posit that a
> hybrid approach that combines endpoint-based filtering with network
> filtering may prove least damaging.  An endpoint may choose to
> participate in a filtering regime in exchange for the network
> providing broader unfiltered access."

I've added the following to the end of the sentence as the RFC is too
long to repeat what is already in 7754:

   "and the IAB consensus on those mechanisms."

But I'll note that this cherry picks one part of the conclusion
section of 7754 and even this text acknowledges that some network
filtering is needed in the suggested hybrid approach.

The first paragraph of this section says:
  "Filtering will continue to occur on the Internet. We conclude that,
   whenever possible, filtering should be done on the endpoint.
   Cooperative endpoints are most likely to have sufficient contextual
   knowledge to effectively target blocking; hence, such blocking
   minimizes unintended consequences.  It is realistic to expect that at
   times filtering will not be done on the endpoints.  In these cases,
   promptly informing the endpoint that blocking has occurred provides
   necessary transparency to redress any errors, particularly as they
   relate to any collateral damage introduced by errant filters."

This text does not say it is bad, it says that it should occur when
possible on the endpoint and that in cases where it is not possible,
the end points should be notified of this filtering.  That's different
from saying filtering is bad as there are a number of cases why the
IAB agreed on a hybrid approach.

DDoS mitigation requires the use of SP filtering to be effective.
This is a clear example of where filtering must be done on the network
and is very important and hard to argue that it isn't good.  You may
have to step back toward the source of the traffic, iteratively
setting up filters to block traffic through cooperation of SPs until
you get close to the source.

Filtering recommended in BCP38 certainly has had a positive impact.

SPs also use filtering to protect their own infrastructure.

This was just a quick response, I am sure there are other good
examples that supported the hybrid recommendation.

>
>
>    detect or prevent attacks as well as to guarantee service level
>    expectations.  In some cases, alternate options are available when
>    encryption is in use, but techniques like that of data leakage
>
> These certainly are use cases, but you really need to acknowledge that
> it's also a form of user surveillance.
>

This is referring to corporate networks.  The rules are a bit
different since you get a paycheck and agree to monitoring, sign an
acknowledgement as an employee then operate on their equipment and
network.

To help make this point more clear, I've added text into section 4.1,
let us know if this does not address your concern:

OLD:
Large corporate enterprises are the owners of the platforms, data, and
network infrastructure that provide critical business services to
their user communities. As such, these enterprises are responsible for
all aspects of the performance, availability, security, and quality of
experience for all user sessions. These responsibilities break down
into three basic areas:

NEW:
Large corporate enterprises are the owners of the platforms, data, and
network infrastructure that provide critical business services to
their user communities. As such, these enterprises are responsible for
all aspects of the performance, availability, security, and quality of
experience for all user sessions. Users typically sign agreements
acknowledging that they are subject to monitoring while operating on
corporate networks. Subsections of 4. Encryption for Enterprises may
discuss techniques that access data beyond the data-link, network, and
transport level headers typically used in SP networks since the
corporate enterprise owns the data. These responsibilities break down
into three basic areas:

This was one of the reasons why we felt it was important to keep
section 4 separate.

>
>    Some DLP tools intercept traffic at the Internet gateway or proxy
>    services with the ability to man-in-the-middle (MiTM) encrypted
>    session traffic (HTTP/TLS).  These tools may use key words important
>    to the enterprise including business sensitive information such as
>    trade secrets, financial data, personally identifiable information
>    (PII), or personal health information (PHI).  Various techniques are
>    used to intercept HTTP/TLS sessions for DLP and other purposes, and
>    are described in "Summarizing Known Attacks on TLS and DTLS"
>    [RFC7457].
>
> As far as I know, the MITM techniques used by middleboxes are not
> described in 7457.

The use of an RSA static key is discussed in terms of the danger of
using this approach in Section 2.8. I updated the text slightly to
make this point more clear and added the section reference:

Various techniques are used to intercept HTTP/TLS sessions for DLP and
other purposes, and can be misused as described in "Summarizing Known
Attacks on TLS and DTLS [RFC7457] Section 2.8.

>
> You also need to cover the fact that these MITM are a threat to user
> security because they are often so badly implemented.

I think 7457 does a good job of that.  Let us know if you have
proposed text if the above fix isn't enough for you coupled with this
being in the Enterprise section.

>
>
> S 5.4.
> It's pretty odd to talk about phishing without acknowledging that by
> far the largest anti-phishing platform (Safe Browsing) operates in the
> client, not be network interception.

We responded on this previously pointing out that this is mentioned in
section 5.3 on phishing.  Here's the text:

   Administrators might also add URLs contained in
   messages to block lists locally or this may also be done by browser
   vendors through larger scales efforts like that of the Anti-Phishing
   Working Group (APWG).  See the Coordinating Attack Response at
   Internet Scale (CARIS) workshop Report [RFC8073] for additional
   information and pointers to the APWG's efforts on anti- phishing.

The CARIS report goes a bit deeper as well.  The approach is broader
than just the browser vendors and that should be acknowledged.
Cooperation of many other players is involved in updating the block
lists and working with law enforcement to take down the offending
sites.  Safe Browsing is just one piece of the larger puzzle and the
browser block lists are already mentioned.

>
>
>     The transport header encryption prevents trusted transit proxies.  It
>    may be that the benefits of such proxies could be achieved by end to
>
> You don't define a "trusted transit proxy" so I don't know what this
> means, and whether they provide any benefit, but this certainly sounds
> euphemistic. Generally, "trusted" is not an adjective we associate
> with network proxies operated by third parties.

We added a little more text on this per Benjamin's comment.  I'm
including the full text of the paragraph so this is not taken out of
context as endorsing such mechanisms as the text goes on to say other
ways it could be addressed in an encrypted Internet.  Here is the
text.

     Transport header encryption prevents the use of transit proxies
     in center of the network and the use of some edge proxies by preventing
     the proxies from taking action on the stream. It may be that the benefits
     of such proxies could be achieved by end-to-end client and server
     optimizations, distribution using CDNs, plus the ability to continue
     connections across different access technologies (across dynamic
     user IP addresses).

>
>
>    In the best case scenario, engineers and other innovators would work
>    to solve the problems at hand in new ways rather than prevent the use
>    of encryption.  As stated in [RFC7258], "an appropriate balance
>    (between network management and PM mitigations) will emerge over time
>    as real instances of this tension are considered."
>
> Much of the context of this debate is about whether operators not
> being able to do the things in this document is a problem, and this
> seems to presume the answer.

Section 8 has been overhauled in response to Deborah's comments. I see
what you mean in the wording and that was not intended. The goal of
the draft is to help improve adoption by talking about the issues and
bringing them to the surface for discussion (tough discussions that
need to happen).  Here is the current text.

"As stated in [RFC7258] an appropriate balance (between network
management and PM mitigations) will emerge over time as real instances
of this tension are considered." Numerous operators made it clear in
their response to this document that they fully support strong
encryption and providing privacy for end users, this is a common goal.
Operators recognize not all the practices documented need to be
supported going forward, either because of the risk to end user
privacy or alternate technologies and tools have already emerged. This
document is intended to support network engineers and other innovators
to work toward solving network and security management problems with
protocol designers and application developers in new ways that
facilitate adoption of strong encryption rather than preventing the
use of encryption. By having the discussions on network and security
management practices with application developers and protocol
designers, each side of the debate can understand each others goals,
work toward alternate solutions, and disband with practices that
should no longer be supported. A goal of this document is to assist
the IETF to understand some of the current practices so as to identify
new work items for IETF-related use cases which can help facilitate
the adoption of strong session encryption and support network and
security management."

>
>
>    This optimization at network edges measurably improves real-time
>    transmission over long delay Internet paths or networks with large
>
> Do you have a citation for this claim?

The draft that this text refers to in the previous paragraph has a
section on performance enhancing proxies, section 3.5 and is referred
to right before this text. David Dolson was the contributor.

>
>
>    Web proxies are sometimes used to filter traffic, allowing only
>    access to well-known sites found to be legitimate and free of malware
>    on last check by a proxy service company.  This type of restriction
>    is usually not noticeable in a corporate setting as the typical
>    corporate user does not access sites that are not well-known to these
>    tools, but may be noticeable to those in research who are unable to
>    access colleague's individual sites or new web sites that have not
>    yet been screened.  In situations where new sites are required for
>    access, they can typically be added after notification by the user or
>    proxy log alerts and review.  Home mail account access may be blocked
>    in corporate settings to prevent another vector for malware to enter
>    as well as for intellectual property to leak out of the network.
>    This method remains functional with increased use of encryption and
>    may be more effective at preventing malware from entering the
>    network.  Web proxy solutions monitor and potentially restrict access
>    based on the destination URL or the DNS name.  A complete URL may be
>    used in cases where access restrictions vary for content on a
>    particular site or for the sites hosted on a particular server.
>
> If you are filtering on URL and there is HTTPS involved, then you are
> a MITM, and this is potentially noticeable to end-users. We encounter
> this regularly when MITM proxies make mistakes in getting into our
> trust anchor store.

This is in the enterprise section where monitoring is accepted by end
users.  What is your proposal here?  I don't see an issue with
describing this usage.  Are you okay with this text since you also see
this as an issue and perhaps it needs more discussion?

>
>
> Re: 0-rating.
>    user.  This feature is impacted if encryption hides the details of
>    the content domain from the network.
>
> Well, maybe. Facebook's zero rating, for instance, is IP-based.
> https://info.internet.org/en/blog/2015/09/24/enhancing-security-and-privacy-of-free-basics/

It seems the providers or applications offering 0-rating all operate
differently.
https://arstechnica.com/information-technology/2016/02/verizons-mobile-video-wont-count-against-data-caps-but-netflix-will/

I had more of an issue with the word feature here, so I believe I
addressed your comment and my concern with the following:

     For some implementations, zero rating is impacted if encryption
     hides the details of the content domain from the network.

>
> S 2.2.2.
> The presentation here seems biased given that it does not acknowledge
> that one of the reasons that ISPs do traffic class discrimination is
> to prioritize favored rather than disfavored traffic, regardless of
> user preferences. I don't believe that the IETF has taken a position
> for net neutrality, but I'm also pretty sure we don't have consensus
> against it.

How about the following text:
This section does not consider traffic discrimination by service
providers related to NetNeutrality, where traffic may be favored
according to the service provider preference as opposed to the user's
preference. These use cases are considered out-of-scope for this
document as controversial practices.

>
>
> ----------------------------------------------------------------------
> COMMENT:
> ----------------------------------------------------------------------
>
>    Pervasive Monitoring (PM) attacks on the privacy of Internet users is
>    of serious concern to both the user and the operator communities.
> are of serious concern

Thanks.
>
>    Traditional network management, planning, security operations, and
>    performance optimization have been developed in an Internet where a
>    large majority of data traffic flows without encryption.  While
> you have a plural/singular mismatch here.
>
>    Authentication with IPsec [RFC7619] and there are a number of
>    infrastructure use cases such as server to server encryption, where
>    this mode is deployed.  While OS is helpful in reducing pervassive
> Nit, no comma before "where"

Done, thanks.
>
>    recommendations from these documents were were built upon for TLS 1.3
>    to provide a more inherently secure end-to-end protocol.
> "were were"

Already fixed, thanks.
>
>    to-user content encryption schemes, such as S/MIME and PGP for email
>    and encryption (e.g.  Off-the-Record (OTR)) for XMPP are used by
>    those interested to protect their data as it crosses intermediary
> Not, "e.g.,"

Fixed, thanks.
>
>    been impacted by increases in encrypted traffic.  Only methods
>    keeping with the goal of balancing network management and PM
>    mitigation in [RFC7258] should be considered in solution work
>    resulting from this document.
> I don't understand what the normative content of this was.

There is no normative content.  Are you asking because the lowercase
should was used?

>
>    upgrades before user experience declines.  For example, findings of
>    loss and jitter in VoIP traffic can be a predictor of future customer
>    dissatisfaction (supported by metadata from the RTP/RTCP protocol )
>    [RFC3550], or increases in DNS response time can generally make
>    interactive web browsing appear sluggish.  But to detect such
>    problems, the application or service stream must first be
>    distinguished from others.
>
> This is a little hard to read, but generally this information is not
> encrypted for SRTP/SRTCP.

In looking at the text, the Secure version of RTP/RTCP isn't mentioned
and isn't cited as an issue.  The text (from Dave Dolson, we think)
seems to say that any form of security that obscures the application
or service info of the stream complicates analysis as VoIP, or
analysis as <something else>.

If this isn't clear enough, would you like to propose text?

>
>    When using increased encryption, operators lose a source of data that
>    may be used to debug user issues.  Because of this, application
>    server operators using increased encryption might be called upon more
>    frequently to assist with debugging and troubleshooting, and thus may
>    want to consider what tools can be put in the hands of their clients
>    or network operators.
>
> This is phrased as hypothetical, but is there any actual data to
> support this? We have a lot of experience now with encrypted voice and
> video as well as Web. Do those providers report any increased level of requests.

This makes perfect sense.  If you are troubleshooting and the data is
not available at the endpoint, the network is used.  If that goes
away, logging and reporting at the endpoint has to improve.  If you
take a look at the feedback from the OPsDir review, it had several
specific types of log improvements added into a paragraph early into
the document.  I added a few more to that from other comments.

In my operational experience as well as work with customers at EMC,
I've heard this comment as well and it was addressed.  This is part of
why the increase in encryption with storage platforms is not a big hit
- tools were provided at the endpoint to fill the gap.

>
>    the new flow and would not be able to route it back to the original
>    POP.
>
> I'm having a little trouble understanding this paragraph. Why is this
> about mobile operators? It seems like it's an issue for anyone who has
> a service that might have mobile clients.

If you mean laptops/IP based devices on WiFi access, this works
differently at the routing layer than with cellular mobile phones.
Phones need to be able to transition seamlessly with migrations
(coordinated roaming).  Other devices, like laptops on WiFi access,
might need this type of transition within a wireless managed
environment, but this is with APs that don't typically attempt to
preserve connection state. When IP based devices on WiFi access have
traffic traversing POPs, it's at the IP layer and the applications
handle continuity.  The key difference between WiFi and cellular is
maintaining connection state.

>
>    effective at providing data offload when there is a network element
>    close to the receiver that has access to see all the content.
> This section is also confusing in that it fails to distinguish between proxies
> of this type that the user opts into from transparent proxies that just do this
> service without the user's consent. Part of the purpose of encryption is to
> preclude that.

This reads to me as if these are transparent proxies, so I'll add that
in to clarify the text further.  Thanks.

>
>    created from the intercepting device to the client's destination,
>    this is an opt-in strategy for the client.  Changes to TLSv1.3 do not
>    impact this more invasive method of interception, where this has the
> I don't understand the cite to TLS 1.3 here. None of this is presently affected
> by 1.3.

This is saying that changes to TLSv1.3 do not impact this more
invasive method of interception explicitly, so I believe the text
already addresses your point.  If not, could you please suggest text?

>
>    endpoints as a service reduces providers' ability to offer parental
>    control.
> This section makes it seem like there are no other methods that allow for
> parental control, but that's not true. There are parental control mechanisms
> which rely on MITM proxies or application interfacing.

The section NOW starts off with the following in the first paragraph
that should address your concern:

    This section is intended to document a selection of current
    content blocking practices...

I think this came from Benjamin's review - the section is not
exhaustive (neither is the draft as it was contribution driven).

This text in the first paragraph should also help with your point:
    Content blocking may also happen at endpoints or at the edge
    of enterprise networks, but those are not addressed in this section.

At the edge is a proxy/gateway MiTM solution.

The next paragraph talks about proxies in the core or edge of a
network, these are also MiTM devices, so I think that's well covered.

The following sentence in this section calls this out as MiTM behavior
explicitly:

    Changes to TLSv1.3 do not impact this more invasive method of
     interception, that has the potential to expose every HTTPS
     session to an active man in the middle (MitM).

I ammended the following sentence in the last paragraph in case that helps you:

OLD:
This type of granular filtering could occur at the endpoint.

NEW:
This type of granular filtering could occur at the endpoint or as a
proxy service.

>
>    HTTP headers and content are encrypted, this prevents mobile carriers
>    from intercepting the traffic and performing an HTTP redirect.  As a
>    result, some mobile carriers block customer's encrypted requests,
> Yes, stopping traffic redirection is actually one of the major design purposes
> of HTTPS.

Sure, there's not an issue other than the practice needs to change and
they need to figure out better ways to notify customers.  It's raised
here in case better ideas can be developed and some operator may look
at the reference (RFC6108).  Adam and Al were chatting on this as a
result of his review, so hopefully they make a little progress.

I added the word appropriately as I think that will address your
concern.  The operators just want efficient ways to notify their
customers, it doesn't have to be done this way, but they raised the
issue because they don't know what to do and I believe, want help.

NEW:
When the HTTP headers and content are encrypted, this appropriately
prevents mobile carriers from intercepting the traffic and performing
an HTTP redirect.

>
>    to the customer and additional overhead to the mobile network service
>    provider.
> This section is basically a commercial for this practice. It needs to
> acknowledge that it's actually much closer to IETF consensus that it's a bad
> practice.

This text was already changed as follows:

     The customer may need to call customer care to find out the
     reason and/or resolve the issue, possibly extending the time
     needed to restore their network access.
>
>    headers to accomplish the, sometimes considered controversial,
>    functions above.
> Again, this is precisely the form of attack that HTTPS is intended to prevent.

The following paragraph was added per conversations with Christian and
Martin.  Hopefully, this also addreses your concern.  The paragraph
mentioned was amended as well.

NEW:
    Guidance from the Internet Architecture Board has been provided
     in [RFC8165] on Design Considerations for Metadata Insertion.
     The guidance asserts that designs that share metadata only by
     explicit actions at the host are preferable to designs in which
     middleboxes insert metadata. Alternate notification methods that
     follow this and other guidance would be helpful to mobile carriers.

>
>    perform SSL/TLS decryption are impacted by the increased use of
>    encryption that prevents interception.
> I don't really understand what this text means. What is "use of encryption that
> prevents interception" in the context of tools which already do decryption?

This reads clear enough to me, but would you be happier with:

s/impacted/no longer functions/

It's referring to encryption that prevents interception, not talking
about proxies which still can be used technically.  This change has
not been made yet, so please let us know if this helps or if you have
another suggestion.


>
>    [DarkMail].  Of course, SPAM filtering will not be possible on
>    encrypted content.
> This is not strictly correct, as you can still header filter, etc.

It seems a few words were trimmed in what you have quoted above.
Here's the full sentence:

Of course, content-based spam filtering will not be possible on
encrypted content.

I'm not sure what happened there as I don't think this was a recent
fix. The sentence was in context of content-based filtering.

In much earlier versions of this draft, there was mention of efforts
that would encrypt email header information to protect privacy
discussed a couple of years ago (SAAG and a spin off list) - which is
a good thing to do.  If that happens operations are impacted and that
would require discussion to develop new approaches for spam filtering
and other email based attack prevention techniques.

>
>    over the Internet.  Options for monitoring will vary with each
>    encryption approach described below.  In most cases, solution have
>    been identified to provide encryption while ensuring management
> Nit: "solutions have"

Already fixed, thanks.
>
>    allow for multiple end user sessions to share the same TCP
>    connection.  This rasises several points of interest with an
>    increased use of encryption.  TCP session multiplexing should still
> Typos: rasises

Fixed, thanks.
>
>    be possible when TLS or TCPcrypt is in use since the TCP header
>    information is exposed leaving the 5-tuple accessible.  The use TCP
>    session multiplexing of an IP layer encyption, e.g.  IPsec, that only
> I'm not sure if this is correct. What precisely do you mean by "TCP
> session multiplexing"? A cite would be helpful here.

It's described in section 4.1.3.2:

    TCP pipelining/session multiplexing used mainly by
    middleboxes today allows for multiple end user sessions
    to share the same TCP connection.

>
>    center.  HTTP pipelining requires both the client and server to
>    participate; visibilty of packets once encrypted will hide the use of
>    HTTP pipelining for any monitoring that takes place outside of the
> Typo: visibility

Fixed, thanks.
>
>    traffic cannot be intercepted, encouraging alternate options such as
>    performing these functions at the edge.
> I'm not seeing the relevance of this. Who is proposing solutions in which
> encrypted traffic cannot be intercepted at the outgoing network edge.

The only option here for this described usage is a proxy where the TLS
1.3 session is terminated and restarted.  If you look back to slides
from Stephen on PM and advancements resulting from PM being considered
an attack, one of the ideas to make TLS stronger was DANE
authentication to provide a way to know you truly have an e2e session
- a very good thing.  The draft on the last telechat:
https://datatracker.ietf.org/doc/draft-ietf-tls-dnssec-chain-extension/
that should be approved soon is able to do this with some middleboxes,
but I'm not sure what happens with a proxy - so I asked the editors
for clarification.  If this just doesn't work and the session proceeds
without this extension, there is nothing to notify on.  If this is
something proxies should be aware of to allow through unhampered, it
would be good to include a little more text.  For instance, in
corporate networks certain traffic with PII, like financial
transactions, are not proxied and would benefit from using this
extension, giving their users assurance in the security of their
sessions.

>
>    owing to concealment of critical headers and payloads.  Many forms of
>    enterprise performance management may be similarly affected.
> Again, this is sort of transparent caching is an anti-pattern, so this document
> ought to acknowledge that,

I added the following text at the end of this paragraph to address your concern:
It should be noted that transparent caching is considered an anti-pattern.

If you have alternate text to suggest, please do!


>
>    parts of the address assignment/management protocols, critical for
>    SAVI mechanisms, can result in a dysfunction of the SAVI mechanisms.
> Does anyone actually deploy SAVI? If not, encryption isn't having much of an
> impact.

It appears to be the case with drafts being published as recent as 2017:
https://tools.ietf.org/html/rfc8074

And I'm told it is widely deployed in China.

>
>    network filters look out for seeing a Server Name Indication
>    extension, they may not find one.  The SNI Encryption in TLS Through
>    Tunneling [I-D.ietf-tls-sni-encryption] draft has been adopted by the
> This doesn't really follow. I mean they "may not" but overwhelmingly they will

I'm not sure when the text was changed, but it already has been changed from.

OLD:

   This information is only visible if the client is populating the
   Server Name Indication extension.  This need not be done, but may be
   done as per TLS standard and as stated above this has been
   implemented by all major browsers.  Therefore, even if existing
   network filters look out for seeing a Server Name Indication
   extension, they may not find one.

NEW:
This information is only available if the client populates the Server
Name Indication extension. Doing so is an optional part of the TLS
standard and as stated above this has been implemented by all major
browsers. Due to its optional nature, though, existing network filters
that examine a TLS ClientHello for a SNI extension cannot expect to
always find one.

>
>



-- 

Best regards,
Kathleen