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Thing-to-Thing Research Group                                 M. Burgess
Internet-Draft                                    Independent Researcher
Intended status: Informational                              H. Wildfeuer
Expires: October 22, 2016                                  Cisco Systems
                                                          April 20, 2016


 Federated Multi-Tenant Service Architecture for an Internet of Things
                   draft-burgess-promise-iot-arch-01

Abstract

   This draft describes architectural recommendations for a unified
   concept of Cloud Computing and Internet of Things, based on tried and
   tested principles from infrastructure science.  We describe a
   functional service architecture that may be applied in the manner of
   a platform, from the smallest scale to the largest scale, using
   vendor agnostic principles.  The current draft is rooted in the
   principles of Promise Theory[Bergstra1] and voluntary cooperation.

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
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   Internet-Drafts are draft documents valid for a maximum of six months
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   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 October 22, 2016.

Copyright Notice

   Copyright (c) 2016 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
   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



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   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.  Requirements and Promises Language  . . . . . . . . . . . . .   3
   3.  Definitions and concepts  . . . . . . . . . . . . . . . . . .   3
   4.  Device interconnection  . . . . . . . . . . . . . . . . . . .   4
   5.  Federation of agency  . . . . . . . . . . . . . . . . . . . .   6
     5.1.  Ownership . . . . . . . . . . . . . . . . . . . . . . . .   7
     5.2.  Tenancy and separation of concerns  . . . . . . . . . . .   7
     5.3.  Proximity of services to location-sensitive Things  . . .   8
   6.  The concept of workspaces . . . . . . . . . . . . . . . . . .   8
     6.1.  Workspaces and namespaces . . . . . . . . . . . . . . . .   8
     6.2.  Workspaces promises . . . . . . . . . . . . . . . . . . .   9
     6.3.  Workspaces as resource clusters . . . . . . . . . . . . .   9
     6.4.  Workspace maintenance . . . . . . . . . . . . . . . . . .  10
   7.  Generic Promise-Oriented Architecture . . . . . . . . . . . .  11
     7.1.  Control . . . . . . . . . . . . . . . . . . . . . . . . .  11
     7.2.  Services  . . . . . . . . . . . . . . . . . . . . . . . .  12
     7.3.  Promises  . . . . . . . . . . . . . . . . . . . . . . . .  13
     7.4.  Agents and their promises . . . . . . . . . . . . . . . .  13
     7.5.  Standard promises . . . . . . . . . . . . . . . . . . . .  14
     7.6.  Contextual policy-based adaptation  . . . . . . . . . . .  14
     7.7.  Change of policy (system intent)  . . . . . . . . . . . .  15
     7.8.  Separation of concerns versus timescales  . . . . . . . .  15
     7.9.  Device roles per workspace or region  . . . . . . . . . .  16
     7.10. Connectivity and Network Policy . . . . . . . . . . . . .  17
   8.  Remarks . . . . . . . . . . . . . . . . . . . . . . . . . . .  18
   9.  Summary and Outlook . . . . . . . . . . . . . . . . . . . . .  19
   10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  19
   11. Security Considerations . . . . . . . . . . . . . . . . . . .  19
   12. Normative References  . . . . . . . . . . . . . . . . . . . .  20
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  21

1.  Introduction

   The scenario we call the Internet of Things (IoT) is an inflection
   point in the development of information local and global
   infrastructure.  We know cloud computing as a commoditization of
   primary infrastructure resources (also `things') for flexible
   datacentre hosting.  The facilitation of a common platform for the
   next generation of global commerce presents a challenge of both
   technological and human dimensions.  Not only do we have to solve the
   matter of technology at scale, we must also solve the matter of human
   dignity and participation.  This is a challenge that spans every



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   layer of the software and networking stacks, yet can be described in
   general terms without the need to specific implementations.  That is
   our goal in this (revised) draft.  Only a few new ideas are needed to
   synthesize this infrastructure, however several old technology
   practices must be deprecated for scaling and security considerations.

   A platform for society as a whole must be vendor agnostic at its
   root, and must leave ample space for vendor specific creativity on
   top.  What distinguishes IoT from past scenarios is the prolific
   contact surface it will expose to the physical world, embedding
   devices pervasively in our close environments, and touching every
   part of human life.  At the time of writing, IoT has barely begun to
   emerge in domestic and industrial settings; however, choices we make
   now could help or hinder the development of an adequate platform over
   the coming decades.  The proposed architecture not only scales up to
   large numbers, it also scales down to small devices of low
   capability; from the largest installations to the smallest, and from
   the tiniest amounts of data, to vast data-stores collected by
   scientific computing at the limits of possibility.

2.  Requirements and Promises Language

   The term "PROMISE", "PROMISES" in this document are to be interpreted
   as described in Promise Theory [Bergstra1]

   When used, the key words "MUST", "MUST NOT", "REQUIRED", "SHALL",
   "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in RFC
   2119 [RFC2119].

3.  Definitions and concepts

   IP endpoint  A hardware or software agent that is IP addressable, via
             a TCP/IP capable interface.

   Static endpoint  A hardware or software agent with an IP address
             (prefix and subnet) that is fixed over the timescale of
             application service interactions.

   Mobile endpoint  A hardware or software agent whose IP address
             location can change on the timescale of application service
             interactions.

   Application server/service  Any agent that promises to respond to
             requests, from external parties, and perform services of
             any kind, on a timescale that we may call the application
             service timescale.




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   Multi-tenant application service  A collection of agents housed as
             tenants within a single host device, each offering
             different services, with potentially different timescales.

   Client application  An agent that consumes data from an application
             service, requested either by imposed query or by promised
             schedule.

   Application Programmer Interface (API)  A set of interfaces that
             expose remote agents to accessing and overriding of the
             local autonomy of agents.

   Standalone Thing (FFD)  A full function device (FFD)[OneM2M], with an
             IP address, that can present its own service gateway or
             interface to the IP network.

   Peripheral Thing (RFD)  A reduced function device (RFD)[OneM2M], with
             no IP address, that attaches to a host gateway device as a
             peripheral, over an arbitrary network (USB, PCIe, CANbus,
             Profibus, ModBus, wireless sensor network, etc).  Devices
             are addressable, only through the gateway service.  This
             includes portmapped devices.

   Embedded network  Any network (IP or non-IP) that is non-IP routed,
             i.e. contained within a host endpoint as part of a black
             box, e.g. isolated NAT, device bus, serial channels.

   Transducer  An agent that consumes a service from another agent, and
             provides a new service based on the consumed service, e.g.
             a router, encrypter, compressor, etc.

   Trust     A unilateral policy assessment of one agent by another,
             concerning its reliability in honouring promises.  Trust is
             not necessarily a transitive property.

   Partial connectivity  A device is said to have partial connectivity
             if it is unavailable for intervals of time, e.g. due to
             loss of connectivity, mobility, or power napping.

4.  Device interconnection

   A platform that brings computing closer to users, away from
   specialized datacentres, must be based on plausible assumptions.  We
   assume that devices live in a partially connected environment, of
   limited reliability: they MUST be fault tolerant to loss of
   communications, both with other devices, in the course of providing
   application services, and with trusted sources of information.  The
   minimum level of interdependency is recommended to facilitate this.



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   For a nascent Internet of Things, our focus is naturally drawn to the
   specialized leaf devices, where data may be produced or consumed.  It
   will take many years to commoditize these sensors and actuators, and
   their local communication architectures.  However, these are only
   half the picture. `Thing' devices, by design, also communicate with
   online services deployed `higher up', or `Northbound' in the system,
   to offload analysis and decision-making.  Their physical capabilities
   thus place them into two broad categories:

   Standalone devices  These are assumed to connect by an IP (or layer
             3) addressable underlay network.  Connectivity is assumed
             end-to-end, without reference to tunnels or software-
             defined overlays.  Policy-based routing is assumed to be
             provided end-to-end, and fully decoupled from the hardware
             and software running on devices.  Routing paths may be
             managed through a namespace registration abstraction which
             we call workspaces.  Segregation and firewalling of certain
             network regions may be included as part of external network
             governance design, but will not be considered here.

   Peripherals  These include bare sensors and actuators, which do not
             possess sufficient onboard resources or software
             interfaces, may attach to hosting standalone devices that
             act as a gateway and IP (or layer 3) endpoint on their
             behalf.

   Transducers  These pass-through devices transformers, converters,
             encapsulation services, etc























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  +------------------+
  | FFD / Standalone |--> IP Endpoint
  +------------------+

  +------------------+
  | RFD / Peripheral |--+
  +------------------+  |      +------------------+
                        +------| FFD / Standalone |--> IP or L3 endpoint
  +------------------+  |      +------------------+
  | RFD / Peripheral |--+
  +------------------+



    Devices may be standalone (FFD), with service interfaces, or hosted
   peripherals (RFD), where data are exposed through service interfaces
        from other buses, e.g.  USB, CANbus, MODbus, Profibus, etc.

                                 Figure 1

   Standalone devices are full stack devices that provide data oriented
   services to data clients

   Stand-alone devices and transducers can vary considerably in their
   processing, memory, and connectivity constraints.  This architecture
   assumes a minimum resource level at the stand-alone device, but the
   device must support `full stack' implementations.  In practice, this
   implies that they contain an embedded OS (e.g.  Linux), and are
   capable of running an agent providing secure service and connectivity
   interfaces.

5.  Federation of agency

   Centralization of intent is a natural form of coordination.  However,
   centralization of command and control (e.g. by API) is not practical
   in environments where the density of devices and overlapping concerns
   reaches the level of a pervasive Internet of Things.  Legacy
   technology is pervasively centralized and top-down in nature:
   requests for domain names and name services, IP address assignment,
   change management of information records, cloud controllers, service
   entry points, etc.  The barriers to scalable autonomous activity are
   high.  The trend has been to delegate these activities to sub-
   authorities (multiple queues) to limit scaling bottlenecks, which
   improves queue latency but not minimum transaction time.  In the
   future, resource management can profit by propagating intentions and
   desires from the bottom-up, i.e. from the many points of service
   consumption, with localization to minimize queueing and flooding
   contention of the independent needs.



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5.1.  Ownership

   Infrastructure ownership is an important issue in a multi-tenant
   consumer environment.  While some devices can be centrally managed by
   providers (regardless of owner), many devices in an Internet of
   Things will be owned by private individuals who will permit
   management by centralized services.  Devices may be managed by:

   Their owners  This applies in particular to personal consumer
             electronics, phones, cars, domestic appliances, etc, where
             users need to retain trusted ownership of their personal
             belongings.

   A service provider  This applies to managed services, factory
             machinery, fleet vehicles, set-top boxes placed in the
             home, power controllers, etc, where users do not need to
             interact with the devices on a management level, but there
             is an advantage to placing a device as a local presence in
             a smart environment.

5.2.  Tenancy and separation of concerns

   Federation of intent, aka multi-tenancy or diversity, all point to
   the need for Special Interest Groups (SIG) or workgroups, who
   specialize within organizations to develop expertise.  Software
   architectures following this pattern are sometimes called
   microservice architectures.  We shall introduce the notion of
   `workspaces' as a federated infrastructure abstraction designed to
   wrap one or more of these specialized services under an umbrella
   abstraction that is easy to understand and work with.  A goal of the
   workspace is to expose only the working parts that need to interact
   with consumers, e.g.  in the same way that one does not expose the
   inner components of a television or a car.

   Federation is desirable along a number of lines:

   o  Geographic partitioning (location)

   o  Separation of timescales (fast and slow)

   o  By special interest group (functional)

   See sections below for further information.








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5.3.  Proximity of services to location-sensitive Things

   Although user-facing devices, deployed in the field, may be separate
   from the agencies processing their sensory data, or feeding them
   guidance (e.g. as policies), it becomes increasingly impractical to
   transport data over long distances between leaf devices and `cloud'
   services as the density of deployed devices grows.  The logical
   outcome is therefore a decentralization of the processing cloud
   itself, so as to bring all necessary resources close to the field-
   deployed data sources themselves.  To scale such a distribution, the
   data services will naturally associate with private workspaces, which
   bound the scope of data generated by Things.

6.  The concept of workspaces

6.1.  Workspaces and namespaces

   Workspaces may be thought of as a modernization and generalization of
   the familiar network domain concept.  Workspaces go beyond
   namespacing, to include federation, collaboration, and segmentation
   of services.  Currently, name domains are typically linked to simple
   directory services (DNS, Active Directory, LDAP etc) for name-address
   mapping.  These are assigned from some top-down agency, either within
   an organization or even beyond it, at a regional level.  The demands
   of multi-tenant environments, where shared resources and separate
   business-processes mix and compete, make these older services less
   than optimal, though not inherently flawed.  It is awkward to
   separate independent collaborative activities and then manage their
   interactions on a need-to-know/need-to-do basis, without involving
   multiple human interventions.  Cloud APIs bring some improvement, by
   exposing arbitrary capabilities to remote operation, but the
   remoteness also brings risks and inefficiencies by exposing an attack
   surface, and from lack of situational awareness of actual state.

   Workspaces are related to the more familiar notion of namespaces in
   information technology; however, namespaces refer mainly to priority
   name-referencing of objects, without necessitating underlying
   resource access segmentation.  Workspaces MUST support multi-tenant
   separation of concerns within a hosted hardware resource space.
   Today, workspace-like facilities are commonly offered as user logins
   on computer operating systems or online services, and quasi-
   workspace-like facilities are offered by virtual private networks,
   and VLANs, etc, in networking.  However, resource management
   platforms do not yet bring the same level of flexibility to
   infrastructure.  Typically, resources are managed by top-down
   agencies who design and grant resource usage manually, leading to the
   insertion of a human processing timescale into the flow of
   automation.



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6.2.  Workspaces promises

   Workspaces need to be able to promise segmentation and privacy.  This
   involves some basic capabilities:

   1.  Authorization and user identification for resource access
       control, within each workspace.

   2.  Multiple compatible user identities in case of a member node
       belonging to several workspaces.

   3.  Resource separation that is respected by all levels of the
       software interactions.  This requires the support of operating
       systems. i.e. segmentation at the network, application, and
       operating system level.  For example, Linux containers, systemd
       containment, network virtualization, etc.

   4.  Service discovery, and registration of capabilities.

   5.  Resource mobility and availability tracking.

   6.  Scaling of information on a need-to-know/need-to-propagate basis,
       avoiding costly data consistency protocols that broadcast data
       updates, and lead to waiting.

6.3.  Workspaces as resource clusters

   At the time of this revision, many of the properties of workspaces
   are being explored under the aegis of cloud application cluster
   managers.  Google's Kubernetes [K8S], for example, is presently the
   most ambitious of these.  It is plausible to imagine extending such a
   system to cover the workspace proposal for both cloud and IoT
   scenarios.

   For a collaborative Internet of Things, where interests span many
   issues from manufacturer interests, to personal ownership, service
   provider concerns, functional responsibility, and security, etc, the
   technologies for inter-group collaboration need to be modernized to
   support logical segmentation, authenticated access, instrumented
   delegation, shared name-service information, as well as private
   naming, all across a converged palette of resources: compute,
   network, storage and sensor-actuators.  This is somewhat reminiscent,
   but not identical, of the goals of Named Data Networking (NDN) [NDN],
   which promotes the semantics of space above the details of its
   interconnectivity.






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   1.  Workspaces imply scope; i.e. they may or may not be private, but
       they must be self-contained and separable, in the manner of
       namespaces.

   2.  Workspaces may or may not be associated with multiple tenants;
       but they are associated with multiple functional or
       organizational issues.

   3.  Workspaces represent a context for human activity, respecting
       separation of concerns.  We need not prejudge what aspects of
       future activity need to embed software-based technologies, but it
       seems safe to assume no limits.  Example workspaces might
       include: online stores and services, offices, the home, a
       children's playground, a squash court, a shop, a factory floor,
       buildings, districts, cities, an emergency communications
       channel, a subsystem of hot and cold water pipes, a hotel dining
       room, a personal drinks cabinet, etc.

   Ubiquitous computing (the Internet of Things) is all about how
   networked devices support a wider variety of workspaces than
   industrial scale central services.  As the density of device
   resources (compute, storage, sensors, actuators) in a workplace or
   home environment increases, isolation of regions, and mapping of
   resources to responsible or interested parties become more difficult
   problems, both to implement and to understand.

   A detailed description of workspaces will be given separately
   [WORKSPC].

6.4.  Workspace maintenance

   The following characteristics describe compatible policy update
   processes:

   1.  Devices subscribe to policy from a trusted workspace source,
       download changes to the policy model when they can, and cache it
       locally so that it is always available.

   2.  Local agents implement cached policy, without any dependence on
       remote communication, and in a fault tolerant fashion.  The
       failure to keep one promise should have minimal impact on the
       ability to keep others.

   3.  By verifying promises continuously, the agent that runs on each
       standalone device will know (or be able to calculate) its
       operational context, and can decide which promises are needed
       from the policy model, and whether or not to keep the promises.
       This scales O(1), i.e. without bottleneck.



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   4.  Each promise that documents and intended outcome of the system is
       verified and measured in the process, providing immediate and
       statistical feedback to policy designers about the success of the
       policy in describing a stable desired outcome.

7.  Generic Promise-Oriented Architecture

   The properties we are looking for in workspaces, suggest an
   architecture based on the principles of promise theory; such a
   promise-oriented architecture is described implicitly in [DSOM2005]
   and [Bergstra1].  It lays out a generic `bottom up' management
   concept, in which devices each have the responsibility for their own
   state and roles.  It resembles Service Oriented Architecture (SOA)
   superficially, without reference to specific technologies,
   implementations or protocols, and relates to the modern notion of
   microservices [MicroS]

   By formulating architecture from the bottom up, one can easily
   account for multi-contextual concerns, from developer concerns about
   realtime software updates (Continuous Delivery and DevOps etc), to
   operational service scaling, governance, and security, in a way that
   top-down schemes cannot easily achieve.

   The relationship between a generic promise-oriented architecture and
   the concept of a workspace is that the former provides a necessary
   and sufficient basis for implementing the latter.  Workspaces are
   expected to be a friendly interface to the underlying promise
   architecture, separating interior and exterior promises cleanly and
   intuitively.

7.1.  Control

   A promise-oriented architecture communicates (e.g. intent and data)
   by authenticated publish-subscribe (aka "pull") methods, for security
   and predictability.  In a workspace, devices MUST not accept control
   commands imposed upon them by remote "push" methods, as this exposes
   a security risk and may lead to inconclusive results during
   uncoordinated pushes (multithreaded access).  In the vernacular usage
   of "control plane" and "data plane", control is asserted through
   agreed service level policies, and data are exchanged within services
   to carry out functions.

   Every standalone device operates autonomously, with policy guidance
   from its owner, without direct external intervention.  To form a
   workspace, any standalone device can give up that autonomy to a
   trusted manager, offering policy updates as a service.  Workspaces
   separate interior and exterior promises about resources and their
   accessibility: they are a priori opaque from the exterior, and



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   transparent from the interior.  By joining a workspace, any device
   (whether a cloud server or an IoT embedded FFD, subordinates itself
   to a bounded policy domain with a private namespace.  Policy
   determines whether a given member of the workspace will expose public
   service entry points, or will be entirely anonymous to exterior
   agents.  This is very close to the community namespace idea currently
   being implemented in the Kubernetes cloud cluster manager [K8S].  One
   can imagine a meta-cluster of such cloud clusters, which are designed
   to tolerate partial network reliability, as forming a basis for the
   Internet of Things alongside more traditional high reliability
   datacentre environments.  Currently, cluster managers assume top-down
   ownership, rather than autonomous self-management, and expose more
   complexity through APIs than is appropriate for average engineers.


        +--------------------------+-----------------------+
        | Workspaces               | Cloud clusters        |
        +--------------------------+-----------------------+
        | Bootstrap server         | Cluster master node   |
        | Standalone device        | Application Pod       |
        | Intermittent network     | Reliable network      |
        | Network by directory     | Network by overlay    |
        | Converged infrastructure | Siloed infrastructure |
        | Bottom up                | Top down              |
        | Unreliable network       | Reliable network      |
        | Node members anywhere    | Nodes in datacentre   |
        | Master policy source     | Master controller     |
        | Need to know             | Full consistency      |
        +--------------------------+-----------------------+


   Rough correspondence between contemporary cloud clusters and proposed
     workspace concept: workspaces are principally a bottom-up, self-
      service collaboration over multiple clusters with more diverse
                          hardware and software.

                                 Figure 2

7.2.  Services

   All devices provide services with varying degrees of sophistication.
   Peripheral devices serve data or actuators to host devices, and
   standalone devices expose functions to one another as software
   services.  Each server plays a role to be composed into the wider
   system.

   Services may be used both for basic infrastructure support, and for
   driving user applications.  No limitations need be stated about



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   applications.  Each fully functional, standalone device is free to
   host any application services.  The result is superficially similar
   to the Service Oriented Architecture [SOA], but without reference to
   a specific technology or methodology.  In modern parlance, the model
   is an example of microservices [MicroS].

   Data collection services are also best implemented with pull methods,
   for resource-light scalability and security.  However, extremely
   limited application devices might initially struggle to support this
   mode of operation.

   Service scaling is a task for workspaces.  Public (exterior) services
   can be provided in a standardized manner, through accessible points
   of entry, whose name information is propagated publicly, analogous to
   a DNS directory.  Workspaces can hide internals (e.g. vendor or
   implementation specific details, private internal services, load
   sharing parallelism.

   Interior name services deal with the registration and propagation of
   information between workspace members, on a need-to-know basis.  This
   is never visible to the exterior network.

7.3.  Promises

   The basic atom of bottom-up policy is a promise.  Each promise
   consists of three things:

   A `promiser'  i.e. a resource that will affect a change by keeping
             its promise to the system, e.g. a file, a process, a
             transaction, a measurement, device settings, etc.

   A description body  i.e. the desired-outcome that is achieved when
             the promise is kept.  This SHOULD be implemented in a
             convergent, idempotent manner, (see [CFENGINE],
             [CONVERGE]).

   A context in which the promise applies, based on time, location, type
             and group membership of the devices referred to in the
             model.

7.4.  Agents and their promises

   In a promise architecture, every device is contextually evaluated and
   integrated from the bottom up, according to the promises is keeps,
   e.g. the services it provides, its behaviours and properties, etc.
   Thus every device is modelled by its individual degree of agency to
   act as a proxy for human intent (policy).




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   Standalone devices are assumed to be equipped with policy-keeping
   software agents.  Peripheral devices, such as sensors or actuators,
   are assumed to be integral parts of the standalone devices, and hence
   maintainable by the their software agents.

   NO system MUST push changes or data to such agents ad hoc, without a
   documented promise to accept; thereafter, `fault tolerance' demands
   that we reject the word `must' from most descriptions, and replace it
   with `promise of best effort', as to reply on perfect behaviour leads
   to brittle systems with unrealistic expectations.  For human safety
   in a rapidly expanding sphere of human involvement, the only `must'
   is for each agent to be stable and self-correcting, subject to the
   guidance of policy.

7.5.  Standard promises

   The following characteristics describe the cooperation between
   agents:

   1.  Standalone devices promise to bootstrap to some trusted
       bootservice, i.e. register to one or more workspaces.

   2.  Standalone devices promise to refuse direct commands imposed from
       network peers (as mentioned above).

   3.  Policy consists of a collection of promises that apply in
       labelled contexts, each of which describes a unique desired end-
       state.

   4.  Promises are kept in a convergent manner, so that all promise-
       keeping actions lead to the desired end-state, no matter what the
       initial state of the device.

   5.  Agents that live on every device have drivers/renderers and make
       all changes without remote communication.

7.6.  Contextual policy-based adaptation

   Each policy agent promises to maintain a context evaluator that
   computes a set of classifying `tags' or `labels' that characterize
   the state of the agent.  This is updated every time the agent
   verifies policy, as its state may change as a result of repairs.
   These may be used as conditionals for distributed policy-based
   decision-making.

   Contextual labels characterize the device, its environment, and its
   location and time.  The labels can then be used in policy to make
   certain promises apply only in specific contexts.



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   When promises, within a policy, are tagged by issue or context,
   agents can select those that apply to its condition, within a larger
   trust relationship implied by policy sourcing.  This simplifies logic
   and promotes stability, as evidenced by experience with software
   agents [CFENGINE].

7.7.  Change of policy (system intent)

   Policy change can be initiated from within a workspace, subject to a
   defined quality assurance, or fit-for-purpose review.  Thus change of
   infrastructure may be instigated from the bottom-up also, as a self-
   service request.

   1.  Human operators (owners or managers) decide on a policy model for
       all devices in an organization or policy group.  This may be
       informed by the feedback about the success rate of previously
       kept promises.

   2.  The changes are edited into a model, which consists of a
       collection of promises that should be kept by all resources on
       all devices.

   3.  Changes are checked and tested before publishing.

   4.  Once changes are approved, they are published by a policy service
       for download at the convenience of the standalone device.

7.8.  Separation of concerns versus timescales

   Infrastructure stability is supported by a separation of systems into
   agencies that act in alignment with specific, separable timescales.
   Separation of fast and slow timescales avoids tight coupling and
   associated complex behaviours and should be considered a priority for
   maintaining safe, stable systems for human dependence.

   Systems scale along two broad lines, which a promise-oriented
   architecture helps to resolve:

   Dynamical scaling  Workload timescales concern the quantitative
             activity of the system: how fast requests are handled, how
             quickly service is delivered, and promises are kept.

   Semantic (functional) scaling  Semantics are normally the concern of
             software engineers and system designers.  This facilitates
             functional understanding.  It is a form of human interface
             or knowledge management.  It is sometimes at odds with the
             needs of dynamical scaling.




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   Changes to semantics should generally be slow compared to the
   workload related dynamical activity, in order to maintain functional
   stability.  Cooperative design of workspaces may observe this
   principle to foster functional stability and workload efficiency.

7.9.  Device roles per workspace or region

   A number of functional roles are required to maintain a service
   lifecycle in a distributed environment.  Making these roles self-
   managed within each workspace is how one scales the diversity of
   human intent and concerns.  Roles are defined by the kinds of
   promises kept by devices:

   Bootstrap server  To provide trusted need-to-know data and local
             contacts so that clients can begin working within a policy
             domain.

   Bootstrap client  To accept essential directory information on trust
             in order to join a local policy domain.

   Policy server  To deliver current policy from an authorized source,
             appropriate for each client (tenancy terms) from its global
             perspective

   Policy client  To subscribe to the policy, selectively, depending on
             context from its local perspective.

   Data server  data server (aka ``Thing'') To offer a catalogue of data
             streams to different tenants This includes sensors,
             actuators.

   Data Client  To subscribe to the policy, selectively, depending on
             context from its local perspective.

   Identity server  Manufacturer User Description service is promised by
             all Things providing a URI that points to a description of
             the device, its serial number characteristics, service
             details etc.

   Identity client  Identity clients promise to make use of data schemas
             and encodings involved in the interpretation of data
             pertaining to the device.

   Directory service  A mutual binding service of published-subscribed
             registry information, enabling mutual discovery of interior
             services.





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                         "Control data"                            "Application data"
 +--------------------------------------------------------------+
 |+------------------+ +------------------+ +----------------- +| +-----------------+
 || Bootstrap server | | Policy server    | | Directory server || |  Data client(s) |
 |+------------------+ +------------------+ +----------------- +| +-----------------+
 +--------|---------------------|----------------------|--------+          |
          |                     |                      |                   |
          +----------------+    |                      |                   |
                           |    |                      |                   |
     +------------------+  |    |                      |                   |
     | FFD / Standalone |  |    |                      |                   |
     |  Bootstrap client|--+    |                      |                   |
     |  Policy client   |-------+                      |                   |
     |  Directory server|------------------------------+                   |
     |  Data client     |--------------------------------------------------+
     +------------------+

        "Thing(s)"




   The roles in each collaborative workspace.  Devices at the bottom of
   the figure typically coordinate through workspace services hosted in
     the "cloud" or any nearby compute resource.  Efficiency suggests
     avoiding long data paths, instead moving computational resources
                     closer to data collection points.

                                 Figure 3

   Bootstrapping new devices into a workspace represents the beginning
   of a device lifecycle.  Devices must begin with the location of a
   known bootstrap server.  Devices must also promise to advertise their
   nature and capabilities, called `identification'.  This may include
   Manufacturer Usage Description (MUD) identifiers [MUD].

7.10.  Connectivity and Network Policy

   So far, much as been said on how the application devices provide
   services via promises, and how system intent can be described and
   orchestrated via policy.  There is also a connectivity (transport)
   fabric for these devices that operates on a set of promises that
   underly the described service framework, i.e. the network.  Each
   network endpoint can be seen as providing its own set of promises
   that are used by other network elements to deliver routing and
   switching capabilities [PromiseNet].  The simplest form of SDN is
   simply name registration and route management.




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   Intent driven networking is becoming more relevant as Software
   Defined Networking (SDN) deployments proliferate.  In the described
   IoT architecture, service policies that describe the IoT system
   intent can be used as an input to derive partial network policies
   (e.g.  Group Based Policy or some other model-based approach), with
   modulation by other data discovered from bootstrapping, etc.  The
   figure below illustrates the relationship between the service and
   network layer policies for IoT.


                   +--------------------+
                   | IoT Service Policy |
                   +--------------------+
                             |
     +---------------------+ | +--------------------+
     | Topology / Location | | |   Orchestration    |
     |                     +-+-+
     |   Bootstrap data    | | | Organization policy|
     +---------------------+ | +--------------------+
                             |
                            \|/
                             v
                 +--------------------+
                 |   IoT SDN policy   |
                 +--------------------+




     Service policy could be partially rendered as an SDN baseline for
      simplifying dependency management.  The simplest form of SDN is
              simply name registration and route management.

                                 Figure 4

8.  Remarks

   The architecture, described in this draft, enables densely clustered
   IT resources to form arbitrary self-service communities that span
   local or wide area networks.  This is decouples a logical patchwork
   of segments on top of a plain end-to-end IP network.  By basing on
   principles of fault-tolerance, including publish-subscribe
   dissemination semantics, this may be scaled, without bottleneck, by
   only the well-known methods currently employed by the World Wide Web.

   IPv6 and successors will play a key role in recapturing network
   simplicity from the many workarounds that have been stacked on top of
   IPv4 and its limitations.  However, currently missing are adequate



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   directory services to support a transparent workspace concept.  The
   present Internet architecture is still geared principally towards a
   shared single-tenant, top-down management model, with host authority
   at the top.  Top down methods require the leaf domains to trust (and
   hence always be exposed to attack from) the layers high up in the
   network.  However, shrink-wrapping workspace boundaries closer around
   their private resources, this management can be simplified, speeded
   up, and become less exposed.

9.  Summary and Outlook

   The issues discussed and laid out in this draft address key issues of
   scalability, fault tolerance, separation of concerns, and federation
   of intent within networked information systems.  The platform,
   described here, is a synthesis of well-known techniques, and is
   deliberately aligned with the needs of agile commercial spaces, as
   well as large industrial distributions, and small domestic needs.  We
   purposely leave open vendor specific concerns, which can easily fit
   into the described architecture, on top of this common set of
   principles.

   Interest in using IT to stimulate smart spaces (homes, buildings,
   vehicles, cities, etc., necessitates a scalable approach to
   interactive services, in which the service clients are not only
   humans but sensors and actuators.  This cannot be scaled reliably
   without the segmentation of spacetime itself.  Centralized cloud
   controllers, as we understand them today, cannot plausibly manage
   stable services for a society to rely on.  We propose extending the
   notion of cloud and IoT to become a single seamless vision, without
   centralization as the core paradigm.

10.  Acknowledgments

   We are grateful for helpful conversations with K.  Burns, M.
   Dvorkin, D.  Maluf, and E.  Lear.

11.  Security Considerations

   With a pervasive contact surface onto both the Internet and the real
   world, security is obvious a major concern.  Experience with
   pervasive frameworks like [CFENGINE], as well as theoretical studies
   of pull-based architectures, suggest that the promise-oriented pull-
   only architecture can reduce the exposure to denial of service
   attacks and data-based overflow attacks, by rejecting all external
   data sent without invitation.  Moreover, the tie-in between service
   and network policy reduces the likelihood of errors in policy across
   the layers.




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   Workspaces can play a role too here, as a shrink-wrapping of service
   scope around minimal set of endpoints, thus reducing the logical
   contact surface for data communications, and publishing information
   purely on a need-to-know basis.  We take is for granted that
   workspace data are encrypted with workspace authorized credentials.

12.  Normative References

   [Bergstra1]
              Bergstra, J. and M. Burgess, "Promise Theory: Principles
              and Applications", 2013.

   [CFENGINE]
              Burgess, M., "A site configuration engine, Computing
              Systems", 1995.

   [CONVERGE]
              Burgess, M., "Configurable immunity model of evolving
              configuration management, Science of Computer
              Programming", 2004.

   [DSOM2005]
              Burgess, M., "An Approach to Understanding Policy Based on
              Autonomy and Voluntary Cooperation, Lecture Notes in
              Computer Science", 2005.

   [K8S]      Various, , "Kubernetes, Open Source Project", 2015-.

   [MicroS]   Richardson, C., "Pattern: Microservices Architecture",
              2014.

   [MUD]      Lear, E., "Manufacturer Usage Description", 2015.

   [NDN]      Zhang, L., Afanasyev, A., Burke, J., Jacobson, V., Claffy,
              K., Crowly, P., Papadopoulos, C., Wang, L., and B. Zhang,
              "Named Data Networking", 2014.

   [OneM2M]   OneM2M, , "Standards for M2M and the Internet of Things",
              2015.

   [PromiseNet]
              Borrill, P., Burgess, M., Craw, T., and M. Dvorkin, "A
              Promise Theory of Networking", 2014.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <http://www.rfc-editor.org/info/rfc2119>.



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   [SOA]      Open Group, , "SOA Reference Architecture Technical
              Standard : Basic Concepts", 2016.

   [WORKSPC]  Burgess, M., Dvorkin, M., and K. Burns, "Self-Service
              Workspaces for Federated IT Infrastructure", 2016.

Authors' Addresses

   Mark Burgess
   Independent Researcher
   Oslo
   Norway


   Herb Wildfeuer
   Cisco Systems
   San Jose
   USA

   Email: hwildfeu@cisco.com































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