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Versions: (draft-tschofenig-smart-object-architecture) 00 02 03 04 05 06 RFC 7452

Network Working Group                                      H. Tschofenig
Internet-Draft
Intended status: Informational                                  J. Arkko
Expires: January 5, 2015
                                                               D. Thaler

                                                            D. McPherson

                                                            July 4, 2014


        Architectural Considerations in Smart Object Networking
               draft-iab-smart-object-architecture-04.txt

Abstract

   Following the theme "Everything that can be connected will be
   connected", engineers and researchers designing smart object networks
   need to decide how to achieve this in practice.

   This document offers guidance to engineers designing Internet
   connected smart objects.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on January 5, 2015.

Copyright Notice

   Copyright (c) 2014 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of



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   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Utilize Design Patterns . . . . . . . . . . . . . . . . . . .   3
     2.1.  Device-to-Device Communication Pattern  . . . . . . . . .   4
     2.2.  Device-to-Cloud Communication Pattern . . . . . . . . . .   5
     2.3.  Device-to-Gateway Communication Pattern . . . . . . . . .   6
     2.4.  Back-end Data Sharing Pattern . . . . . . . . . . . . . .   7
   3.  Re-Use Internet Protocols . . . . . . . . . . . . . . . . . .   8
   4.  The Deployed Internet Matters . . . . . . . . . . . . . . . .  11
   5.  Design for Change . . . . . . . . . . . . . . . . . . . . . .  12
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .  14
   7.  Privacy Considerations  . . . . . . . . . . . . . . . . . . .  14
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  15
   9.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  15
   10. Informative References  . . . . . . . . . . . . . . . . . . .  15
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  17

1.  Introduction

   RFC 6574 [1] refers to smart objects (also called "Things", as in
   Internet of Things in other publications) as devices with constraints
   on energy, bandwidth, memory, size, cost, etc.  This is a fuzzy
   definition, as there is clearly a continuum in device capabilities
   and there is no hard line to draw between devices that can run
   Internet Protocols and those that can't.

   Interconnecting smart objects with the Internet creates exciting new
   innovative use cases and products.  An increasing number of products
   put the Internet Protocol suite on smaller and smaller devices and
   offer the ability to process, visualize, and gain new insight from
   the collected sensor data.  The network effect can be increased if
   the data collected from many different devices can be combined.

   Developing embedded systems is a complex task and designing Internet
   connected smart objects is even harder since it "requires expertise
   with Internet protocols in addition to software programming and
   hardware skills.  To simply the development task, and thereby to
   lower the cost of developing new products and prototypes, we believe
   that re-use of prior work is essential.  Therefore, we provide high-




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   level guidance on the use of Internet technology for the development
   of smart objects.

   Utilize Existing Design Patterns

      Design patterns are generally reusable solutions to a commonly
      occurring design problem.  Existing smart object deployments show
      patterns that can be re-used by engineers with the benefit of
      lowering the design effort.  Individual patterns also have an
      implication on the required interoperability between the different
      entities.  Depending on the desired functionality, already
      existing patterns can be re-used and adjusted.  Section 2 talks
      about various design patterns.

   Re-Use Internet Protocols

      Most, if not all, smart object deployments can make use of the
      already standardized Internet protocol suite.  The Internet
      protocols can be applied to almost any environment due to their
      generic design, and typically offer plenty of potential for re-
      configuration, which allows the them to be tailored for the
      specific needs.  Section 3 discusses this topic.

   The Deployed Internet matters

      When connecting smart objects to the Internet, take existing
      deployment into consideration to avoid unpleasant surprises.
      Assuming an ideal, clean-slate deployments is, in many cases, far
      too optimistic since the already deployed infrastructure is
      convenient to use.  In Section 4 we highlight the importance of
      this topic.

   Design for Change

      The Internet infrastructure, the applications and preferred
      building blocks evolve over time.  Especially long-lived smart
      object deployments need to take this change into account and
      Section 5 is dedicated to that topic.

2.  Utilize Design Patterns

   This section illustrates a number of design pattern utilized in the
   smart object environment.  Note that some patterns can be applied at
   the same time in a product.  Developers re-using those patterns will
   benefit from the experience of others as well as from documentation,
   source code, and available products.





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2.1.  Device-to-Device Communication Pattern

   Figure 1 illustrates a design pattern where two devices developed by
   different manufacturers are desired to interoperate.  To pick an
   example from [1], consider a light bulb switch that talks to a light
   bulb with the requirement that each may be manufactured by a
   different company, represented as manufacturer A and B.  Other cases
   can be found with fitness equipment, such as heart-rate monitors and
   cadence sensors.


                        _,,,,    ,,,,
                       /     -'``    \
                      |  Wireless    |
                      \  Network     |
                      /               \
    ,''''''''|       /                 .       ,''''''''|
    | Light  | ------|------------------\------| Light  |
    | Bulb   |        .                 |      | Switch |
    |........'         `'-              /      |........'
                          \      _-...-`
    Manufacturer           `. ,.'              Manufacturer
        A                    `                      B

             Figure 1: Device-to-Device Communication Pattern

   In order to fulfill the promise that devices from different
   manufacturers are able to communicate out-of-the-box, these vendors
   need to get together and agree on the protocol stack.  Such a
   consortium needs to make a decision about the following protocol
   design aspects:

   o  Which physical layer(s) should be supported?

   o  Which IP version(s) should be used?

   o  Which IP address configuration mechanism(s) are integrated into
      the device?

   o  Which communication architecture shall be supported?  Which
      devices are constrained and what are those constraints?  Is there
      a classical client-server model or rather a peer-to-peer model?

   o  Is there a need for a service discovery mechanism to allow users
      to discover light bulbs they have in their home or office?

   o  Which transport-layer protocol is used for conveying the sensor
      readings/sensor commands? (e.g., UDP)



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   o  Which application-layer protocol is used? (for example, CoAP)

   o  How are requests and responses encoded? (e.g., JSON)

   o  What information model is used for expressing the different light
      levels?  What is the encoding of the information (in a data
      model)?

   o  Finally, some thoughts will have to be spent about the security
      architecture.  This includes questions like: what are the security
      threats?  What security services need to be provided to deal with
      the identified threats?  Where do the security credentials come
      from?  At what layer(s) in the protocol stack should the security
      mechanism reside?

   This list is not meant to be exhaustive but aims to illustrate that
   for every usage scenario many design decisions will have to be made
   in order to accommodate the constrained nature of a specific device
   in a certain usage scenario.  Standardizing such a complete solution
   to accomplish a full level of interoperability between two devices
   manufactured by different vendors takes time but there are obvious
   rewards for end customers and vendors.

2.2.  Device-to-Cloud Communication Pattern

   Figure 2 shows a design pattern for uploading sensor data to a cloud-
   based infrastructure.  Often the application service provider
   (example.com in our illustration) also sells smart objects as well.
   In that case the entire communication happens internally to the
   provider and no need for interoperability arises.  Still, it is
   useful for example.com to re-use existing specifications to lower the
   design, implementation, testing and development effort.

   While this pattern allows using IP-based communication end-to-end it
   may still lead to silos.  To prevent silos, example.com may allow
   third party device vendors to connect to their server infrastructure
   as well.  For those cases, the protocol interface used to communicate
   with the server infrastructure needs to be made available, and
   various standards are available, such as CoAP, DTLS, UDP, IP, etc as
   shown in Figure 2.

   Since the access networks to which various smart objects are
   connected are typically not under the control of the application
   service provider, commonly used radio technologies (such as WLAN,
   wired Ethernet, and cellular radio) together with the network access
   authentication technology have to be re-used.  The same applies to
   standards used for IP address configuration.




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            .................
            |  Application  |
            |  Service      |
            |  Provider     |
            |  example.com  |
            |_______________|
                _,   .
     HTTP    ,'      `.        CoAP
     TLS   _,'          `.     DTLS
     TCP ,'               `._  UDP
     IP-'                    - IP
    ,'''''''''''''|       ,'''''''''''''''''|
    | Device with |       | Device with     |
    | Temperature |       | Carbon Monoxide |
    | Sensor      |       | Sensor          |
    |.............'       |.................'

              Figure 2: Device-to-Cloud Communication Pattern

2.3.  Device-to-Gateway Communication Pattern

   The device-to-cloud communication pattern, described in Section 2.2,
   is convenient for vendors of smart objects and works well if they use
   choose a radio technology that is widely deployed in the targeted
   market, such as IEEE 802.11-based Wifi for smart home use cases.
   Sometimes less widely available radio technologies are needed (such
   as IEEE 802.15.4) or special application layer functionality (e.g.,
   local authentication and authorization) has to be provided.  In those
   cases a gateway has to be introduced into the communication
   architecture that bridges between the different physical layer/link
   layer technologies and performs other networking and security
   functionality.  Figure 3 shows this pattern graphically.  Often,
   these gateways are provided by the same vendor that offers the IoT
   product, for example because of the use of proprietary protocols, to
   lower the dependency on other vendors, or to avoid potential
   interoperability problems.  It is expected that in the future more
   generic gateways will be deployed to lower cost and infrastructure
   complexity for end consumers, enterprises, and industrial
   environments.

   This design pattern can frequently be found with smart object
   deployments that require remote configuration capabilities and real-
   time interactions.  The gateway is thereby assumed to be always
   connected to the Internet.







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              .................
              |  Application  |
              |  Service      |
              |  Provider     |
              |  example.com  |
              |_______________|
                     |
                     |
                     |
              .................
              |    Local      |
              |   Gateway     |
              |               |
              |_______________|
                _,         .
     HTTP    ,'              `.         CoAP
     TLS   _,' Bluetooth Smart  `.      DTLS
     TCP ,'     IEEE 802.11       `._   UDP
     IP-'       IEEE 802.15.4         - IP/6lo
    ,'''''''''''''|          ,'''''''''''''''''|
    | Device with |          | Device with     |
    | Temperature |          | Carbon Monoxide |
    | Sensor      |          | Sensor          |
    |.............'          |.................'

             Figure 3: Device-to-Gateway Communication Pattern

   A variation of this model is the case where the gateway role is
   actually incorporated into the smart phone.  Of course, if the smart
   phone is not connected to smart objects, for example because the
   phone moved out of range, they are not connected with the Internet
   anymore.  This limits the applicability of such a design pattern but
   is nevertheless very common with wearables and other IoT devices that
   do not need always-on Internet or real-time Internet connectivity.
   From an interoperability point of view it is worth noting that smart
   phones with their sophisticated software update mechanism via app
   stores allow new functionality to be updated regularly at the smart
   phone and sometimes even at the IoT device.  With special apps that
   are tailored to each specific IoT device interoperability is mainly a
   concern with regard to the lower layers of the protocol stack, such
   as the radio interface, and less so at the application layer.

2.4.  Back-end Data Sharing Pattern

   The device-to-cloud pattern often leads to silos; IoT devices upload
   data only to a single application service provider.  However, users
   often demand the ability to export and to analyze data in combination
   with data from other sources.  Hence, the urge for granting access to



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   the uploaded sensor data to third parties arises.  This design is
   shown in Figure 4.  This pattern is known from the Web in case of
   mashups and is therefore re-applied to the smart object context.  To
   offer familiarity for developers, typically a RESTful API design in
   combination with a federated authentication and authorization
   technology (like OAuth 2.0 [13]) is re-used.  While this offers re-
   use at the level of building blocks, the entire protocol stack
   (including the data model and the API definition) is often not
   standardized.


                                              .................
                                              |  Application  |
                                             .|  Service      |
                                          ,-` |  Provider     |
                                        .`    | b-example.com |
                                     ,-`      |_______________|
                                   .`
             .................  ,-`
             |  Application  |-` HTTPS
             |  Service      |   OAuth 2.0
             |  Provider     |   JSON
             |  example.com  |-,
             |_______________|  '.
                  _,              `',
                ,'                   '.
             _,' CoAP or               `',    .................
           ,'   HTTP                      '.  |  Application  |
         -'                                 `'|  Service      |
      ,''''''''|                              |  Provider     |
      | Light  |                              | c-example.com |
      | Sensor |                              |_______________|
      |........'

                  Figure 4: Backend Data Sharing Pattern

3.  Re-Use Internet Protocols

   When discussing the need for re-use of available standards vs.
   extending or re-designing protocols, it is useful to look back at the
   criteria for success of the Internet.

   RFC 1958 [6] provides lessons from the early days of the Internet and
   says:

      "The Internet and its architecture have grown in evolutionary
      fashion from modest beginnings, rather than from a Grand Plan",




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   and adds:

      "A good analogy for the development of the Internet is that of
      constantly renewing the individual streets and buildings of a
      city, rather than razing the city and rebuilding it."

   Yet because building very small, battery-powered devices is
   challenging, it may be difficult to resist the temptation to build
   solutions tailored to a specific applications, or even to re-design
   networks from scratch to suit a particular application.

   While developing consensus-based standards in an open and transparent
   process takes longer than developing proprietary solutions, the
   resulting solutions often remain relevant over a longer period of
   time.

   RFC 1263 [4] considers protocol design strategy and the decision to
   design new protocols or to use existing protocols in a non-backward
   compatible way:

      "We hope to be able to design and distribute protocols in less
      time than it takes a standards committee to agree on an acceptable
      meeting time.  This is inevitable because the basic problem with
      networking is the standardization process.  Over the last several
      years, there has been a push in the research community for
      lightweight protocols, when in fact what is needed are lightweight
      standards.  Also note that we have not proposed to implement some
      entirely new set of 'superior' communications protocols, we have
      simply proposed a system for making necessary changes to the
      existing protocol suites fast enough to keep up with the
      underlying change in the network.  In fact, the first standards
      organization that realizes that the primary impediment to
      standardization is poor logistical support will probably win."

   While [4] was written in 1991 when the standardization process was
   more lightweight than today, these thoughts remain relevant in smart
   object development.

   Interestingly, a large range of already standardized protocols are
   relevant for smart object deployments.  RFC 6272 [5], for example,
   made the attempt to identify relevant IETF specifications for use in
   smart grids.

   Still, many commercial products contain proprietary or industry-
   specific protocol mechanisms and researchers have made several
   attempts to design new architectures for the entire Internet system.
   There are several architectural concerns that deserve to be
   highlighted:



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   Vertical Profiles

      The discussions at the IAB workshop (see Section 3.1.2 of [1])
      revealed the preference of many participants to develop domain-
      specific profiles that select a minimum subset of protocols needed
      for a specific operating environment.  Various standardization
      organizations and industry fora are currently engaged in
      activities of defining their preferred profile(s).  Ultimately,
      however, the number of domains where smart objects can be used is
      essentially unbounded.  There is also an ever-evolving set of
      protocols and protocol extensions.

      However, merely changing the networking protocol to IP does not
      necessarily bring the kinds of benefits that industries are
      looking for in their evolving smart object deployments.  In
      particular, a profile is rigid, and leaves little room for
      interoperability among slightly differing, or competing technology
      variations.  As an example, layer 1 through 7 type profiles do not
      account for the possibility that some devices may use different
      physical media than others, and that in such situations a simple
      router could still provide an ability to communicate between the
      parties.

   Industry-Specific Solutions

      The Internet Protocol suite is more extensive than merely the use
      of IP.  Often significant benefits can be gained from using
      additional, widely available, generic technologies such as web
      services.  Benefits from using these kinds of tools include access
      to a large available workforce, software, and education already
      geared towards employing the technology.

   Tight Coupling

      Many applications are built around a specific set of servers,
      devices, and users.  However, often the same data and devices
      could be useful for many purposes, some of which may not be easily
      identifiable at the time that the devices are deployed.

   As a result, the following recommendations can be made.  First, while
   there are some cases where specific solutions are needed, the
   benefits of general-purpose technology are often compelling, be it
   choosing IP over some more specific communication mechanism, a widely
   deployed link-layer (such as wireless LAN) over a more specific one,
   web technology over application specific protocols, and so on.

   However, when employing these technologies, it is important to
   embrace them in their entirety, allowing for the architectural



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   flexibility that is built onto them.  As an example, it rarely makes
   sense to limit communications to on-link or to specific media.
   Design your applications so that the participating devices can easily
   interact with multiple other applications.

4.  The Deployed Internet Matters

   Despite the applicability of the Internet Protocols for smart
   objects, picking the specific protocols for a particular use case can
   be tricky.  As the Internet has evolved over time, certain protocols
   and protocol extensions have become the norm and others have become
   difficult to use in all circumstances.

   Taking into account these constraints is particularly important for
   smart objects, as there is often a desire to employ specific features
   to support smart object communication.  For instance, from a pure
   protocol specification perspective, some transport protocols may be
   more desirable than others.  These constraints apply both to the use
   of existing protocols as well as designing new ones on top of the
   Internet Protocol stack.

   The following list illustrates a few of those constraints, but every
   communication protocol comes with its own challenges.

   In 2005, Fonseca, et al. [15] studied the usage of IP options-enabled
   packets in the Internet and found that overall, approximately half of
   Internet paths drop packets with options, making extensions using IP
   options "less ideal" for extending IP.

   In 2010, Honda, et al. [17] tested 34 different home gateways
   regarding their packet dropping policy of UDP, TCP, DCCP, SCTP, ICMP,
   and various timeout behavior.  For example, more than half of the
   tested devices do not conform to the IETF recommended timeouts for
   UDP, and for TCP the measured timeouts are highly variable, ranging
   from less than 4 minutes to longer than 25 hours.  For NAT traversal
   of DCCP and SCTP, the situation is poor.  None of the tested devices,
   for example, allowed establishing a DCCP connection.

   In 2011, [16] tested the behavior of networks with regard to various
   TCP extensions: "From our results we conclude the middleboxes
   implementing layer 4 functionality are very common -- at least 25% of
   paths interfered with TCP in some way beyond basic firewalling."

   Extending protocols to fulfill new uses and to add new functionality
   may range from very easy to difficult, as [2] explains in great
   detail.  A challenge many protocol designers are facing is to ensure
   incremental deployability and interoperability with incumbent
   elements in a number of areas.  In various cases, the effort it takes



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   to design incrementally deployable protocols has not been taken
   seriously enough at the outset.  RFC 5218 on "What Makes For a
   Successful Protocol?" [9] defines wildly successful protocols as
   protocols that are widely deployed beyond their envisioned use cases.

   As these examples illustrate, protocol architects have to take
   developments in the greater Internet into account, as not all
   features can be expected to be usable in all environments.  For
   instance, middleboxes [8] complicate the use of extensions in the
   basic IP protocols and transport-layers.

   RFC 1958 [6] considers this aspect and says "... the community
   believes that the goal is connectivity, the tool is the Internet
   Protocol, and the intelligence is end to end rather than hidden in
   the network."  This statement is challenged more than ever with the
   perceived need to develop clever intermediaries interacting with dumb
   end devices.  However, RFC 3724 [12] has this to say about this
   crucial aspect: "One desirable consequence of the end-to-end
   principle is protection of innovation.  Requiring modification in the
   network in order to deploy new services is still typically more
   difficult than modifying end nodes."  Even this statement will become
   challenged, as large numbers of devices are deployed and it indeed
   might be the case that changing those devices is hard.  But RFC 4924
   [7] adds that a network that does not filter or transform the data
   that it carries may be said to be "transparent" or "oblivious" to the
   content of packets.  Networks that provide oblivious transport enable
   the deployment of new services without requiring changes to the core.
   It is this flexibility that is perhaps both the Internet's most
   essential characteristic as well as one of the most important
   contributors to its success.

5.  Design for Change

   How to embrace rapid innovation and at the same time accomplish a
   high level of interoperability is one of the key aspects for
   competing in the market place.  RFC 1263 [4] points out that
   "protocol change happens and is currently happening at a very
   respectable clip.  We simply propose [for engineers developing the
   technology] to explicitly deal with the changes rather keep trying to
   hold back the flood.".

   In [18] Clark, et al. suggest to "design for variation in outcome, so
   that the outcome can be different in different places, and the tussle
   takes place within the design, not by distorting or violating it.  Do
   not design so as to dictate the outcome.  Rigid designs will be
   broken; designs that permit variation will flex under pressure and
   survive.".  The term tussle refers to the process whereby different
   parties, which are part of the Internet milieu and have interests



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   that may be adverse to each other, adapt their mix of mechanisms to
   try to achieve their conflicting goals, and others respond by
   adapting the mechanisms to push back.

   In order to accomplish this, Clark, et al. suggest to

   1.  Break complex systems into modular parts, so that one tussle does
       not spill over and distort unrelated issues.

   2.  Design for choice to permit the different players to express
       their preferences.  Choice often requires open interfaces.

   The main challenge with the suggested approach is to predict how
   conflicts among the different players will evolve.  Since tussles
   evolve over time, there will be changes to the architecture too.  It
   is certainly difficult to pick the right set of building blocks and
   to develop a communication architecture that will last a long time,
   and many smart object deployments are envisioned to be rather long-
   lived.

   Luckily, the design of the system does not need to be cast in stone
   during the design phase.  It may adjust dynamically since many of the
   protocols allow for configurability and dynamic discovery.  But
   ultimately software update mechanisms may provide the flexibility
   needed to deal with more substantial changes.

   A solid software update mechanism is needed not only for dealing with
   the changing Internet communication environment and for
   interoperability improvements but also for adding new features and
   for fixing security bugs.  This approach may appear to be in conflict
   with classes of severely restricted devices since, in addition to a
   software update mechanism, spare flash and RAM capacity is needed.
   It is, however, a tradeoff worth thinking about since better product
   support comes with a price.

   As technology keeps advancing, the constraints that the technology
   places on devices evolve as well.  Microelectronics became more
   capable as time goes by, sometimes making it even possible for new
   devices to be both less expensive and more capable than their
   predecessors.  This trend can, however, be in some cases offset by
   the desire to embed communications technology in even smaller and
   cheaper objects.  But it is important to design communications
   technology not just for today's constraints, but also tomorrow's.
   This is particularly important since the cost of a product is not
   only determined by the cost of hardware but also by the cost of
   writing custom protocol stacks and embedded system software.





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   Software updates are common in operating systems and application
   programs today.  Without them, most devices would pose a latent risk
   to the Internet at large.  Arguably, the JavaScript-based web employs
   a very rapid software update mechanism with code being provided by
   many different parties (i.e., by websites loaded into the browser or
   by smart phone apps).

6.  Security Considerations

   Section 3.3 of [1] reminds us about the IETF work style regarding
   security:

      In the development of smart object applications, as with any other
      protocol application solution, security must be considered early
      in the design process.  As such, the recommendations currently
      provided to IETF protocol architects, such as RFC 3552 [10], and
      RFC 4101 [11], apply also to the smart object space.

   In the IETF, security functionality is incorporated into each
   protocol as appropriate, to deal with threats that are specific to
   them.  It is extremely unlikely that there is a one-size-fits-all
   security solution given the large number of choices for the 'right'
   protocol architecture (particularly at the application layer).  For
   this purpose, [5] offers a survey of IETF security mechanisms instead
   of suggesting a preferred one.

   A more detailed security discussion can be found in the report from
   the 'Smart Object Security' workshop [14] that was held prior to the
   IETF meeting in Paris, March 2012.

   As current attacks against embedded systems demonstrate, many of the
   security vulnerabilities are quite basic and remind us about the
   lessons we should have learned in the late 90's: software has to be
   tested properly, it has to be shipped with a secure default
   configuration (which includes no default accounts, no debugging
   interfaces enabled, etc.), and software and processes need to be
   available to provide patches.  While these aspects are typically
   outside the realm of standardization, they are nevertheless important
   to keep in mind.

7.  Privacy Considerations

   This document mainly focuses on an engineering audience, i.e., those
   who are designing smart object protocols and architecture.  Since
   there is no value-free design, privacy-related decisions also have to
   be made, even if they are just implicit in the re-use of certain
   technologies.  RFC 6973 [3] was written as guidance specifically for
   that audience and it is also applicable to the smart object context.



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   For those looking at privacy from a deployment point of view, the
   following additional guidelines are suggested:

   Transparency:  Transparency of data collection and processing is key
      to avoid unpleasant surprises for owners and users of smart
      objects.  Users and impacted parties must, except in rare cases,
      be put in a position to understand what items of personal data
      concerning them are collected and stored, as well for what
      purposes they are sought.

   Data Quality:  Smart objects should only store personal data that is
      adequate, relevant and not excessive in relation to the purpose(s)
      for which they are processed.  The use of anonymized data should
      be preferred wherever possible.

   Data Access:  Before deployment starts, it is necessary to consider
      who can access personal data collected by smart objects and under
      which conditions.  Appropriate and clear procedures should be
      established in order to allow data subjects to properly exercise
      their rights.

   Data Security:   Standardized data security measures to prevent
      unlawful access, alteration or loss of smart object data need to
      be defined and deployed.  Robust cryptographic techniques and
      proper authentication frameworks have to be used to limit the risk
      of unintended data transfers or unauthorized access.

8.  IANA Considerations

   This document does not require actions by IANA.

9.  Acknowledgements

   We would like to thank the participants of the IAB Smart Object
   workshop for their input to the overall discussion about smart
   objects.

   Furthermore, we would like to thank Jan Holler, Patrick Wetterwald,
   Atte Lansisalmi, Hannu Flinck, Joel Halpern, Bernard Aboba, and
   Markku Tuohino for their review comments.

10.  Informative References

   [1]        Tschofenig, H. and J. Arkko, "Report from the Smart Object
              Workshop", RFC 6574, April 2012.






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   [2]        Carpenter, B., Aboba, B., and S. Cheshire, "Design
              Considerations for Protocol Extensions", RFC 6709,
              September 2012.

   [3]        Cooper, A., Tschofenig, H., Aboba, B., Peterson, J.,
              Morris, J., Hansen, M., and R. Smith, "Privacy
              Considerations for Internet Protocols", RFC 6973, July
              2013.

   [4]        O'Malley, S. and L. Peterson, "TCP Extensions Considered
              Harmful", RFC 1263, October 1991.

   [5]        Baker, F. and D. Meyer, "Internet Protocols for the Smart
              Grid", RFC 6272, June 2011.

   [6]        Carpenter, B., "Architectural Principles of the Internet",
              RFC 1958, June 1996.

   [7]        Aboba, B. and E. Davies, "Reflections on Internet
              Transparency", RFC 4924, July 2007.

   [8]        Carpenter, B. and S. Brim, "Middleboxes: Taxonomy and
              Issues", RFC 3234, February 2002.

   [9]        Thaler, D. and B. Aboba, "What Makes For a Successful
              Protocol?", RFC 5218, July 2008.

   [10]       Rescorla, E. and B. Korver, "Guidelines for Writing RFC
              Text on Security Considerations", BCP 72, RFC 3552, July
              2003.

   [11]       Rescorla, E. and IAB, "Writing Protocol Models", RFC 4101,
              June 2005.

   [12]       Kempf, J., Austein, R., and IAB, "The Rise of the Middle
              and the Future of End-to-End: Reflections on the Evolution
              of the Internet Architecture", RFC 3724, March 2004.

   [13]       Hardt, D., "The OAuth 2.0 Authorization Framework", RFC
              6749, October 2012.

   [14]       Gilger, J. and H. Tschofenig, "Report from the 'Smart
              Object Security Workshop', March 23, 2012, Paris, France",
              draft-gilger-smart-object-security-workshop-02 (work in
              progress), October 2013.






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   [15]       Fonseca, R., Porter, G., Katz, R., Shenker, S., and I.
              Stoica, "IP options are not an option, Technical Report
              UCB/EECS", 2005.

   [16]       Honda, M., Nishida, Y., Greenhalgh, A., Handley, M., and
              H. Tokuda, "Is it Still Possible to Extend TCP? In Proc.
              ACM Internet Measurement Conference (IMC), Berlin,
              Germany", Nov 2011.

   [17]       Eggert, L., "An experimental study of home gateway
              characteristics, In Proceedings of the '10th annual
              conference on Internet measurement'", 2010.

   [18]       Clark, D., Wroslawski, J., Sollins, K., and R. Braden,
              "Tussle in Cyberspace: Defining Tomorrow's Internet, In
              Proc. ACM SIGCOMM", 2002.

Authors' Addresses

   Hannes Tschofenig
   Austria

   Email: Hannes.Tschofenig@gmx.net
   URI:   http://www.tschofenig.priv.at


   Jari Arkko
   Jorvas  02420
   Finland

   Email: jari.arkko@piuha.net


   Dave Thaler
   One Microsoft Way
   Redmond, WA  98052
   US

   Email: dthaler@microsoft.com


   Danny McPherson
   US

   Email: danny@tcb.net






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