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In: MissingRef
Network Working Group                                         C. Bormann
Internet-Draft                                   Universitaet Bremen TZI
Intended status: Standards Track                       B. Carpenter, Ed.
Expires: April 11, 2016                                Univ. of Auckland
                                                             B. Liu, Ed.
                                            Huawei Technologies Co., Ltd
                                                         October 9, 2015


             A Generic Autonomic Signaling Protocol (GRASP)
                       draft-ietf-anima-grasp-01

Abstract

   This document establishes requirements for a signaling protocol that
   enables autonomic devices and autonomic service agents to dynamically
   discover peers, to synchronize state with them, and to negotiate
   parameter settings mutually with them.  The document then defines a
   general protocol for discovery, synchronization and negotiation,
   while the technical objectives for specific scenarios are to be
   described in separate documents.  An Appendix briefly discusses
   existing protocols with comparable features.

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 April 11, 2016.

Copyright Notice

   Copyright (c) 2015 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  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Requirement Analysis of Discovery, Synchronization and
       Negotiation . . . . . . . . . . . . . . . . . . . . . . . . .   4
     2.1.  Requirements for Discovery  . . . . . . . . . . . . . . .   4
     2.2.  Requirements for Synchronization and Negotiation
           Capability  . . . . . . . . . . . . . . . . . . . . . . .   6
     2.3.  Specific Technical Requirements . . . . . . . . . . . . .   8
   3.  GRASP Protocol Overview . . . . . . . . . . . . . . . . . . .   9
     3.1.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   9
     3.2.  High-Level Design Choices . . . . . . . . . . . . . . . .  11
     3.3.  GRASP Protocol Basic Properties and Mechanisms  . . . . .  15
       3.3.1.  Required External Security Mechanism  . . . . . . . .  15
       3.3.2.  Transport Layer Usage . . . . . . . . . . . . . . . .  15
       3.3.3.  Discovery Mechanism and Procedures  . . . . . . . . .  16
       3.3.4.  Negotiation Procedures  . . . . . . . . . . . . . . .  18
       3.3.5.  Synchronization Procedure . . . . . . . . . . . . . .  19
     3.4.  High Level Deployment Model . . . . . . . . . . . . . . .  20
     3.5.  GRASP Constants . . . . . . . . . . . . . . . . . . . . .  20
     3.6.  Session Identifier (Session ID) . . . . . . . . . . . . .  21
     3.7.  GRASP Messages  . . . . . . . . . . . . . . . . . . . . .  21
       3.7.1.  GRASP Message Format  . . . . . . . . . . . . . . . .  21
       3.7.2.  Discovery Message . . . . . . . . . . . . . . . . . .  22
       3.7.3.  Response Message  . . . . . . . . . . . . . . . . . .  23
       3.7.4.  Request Message . . . . . . . . . . . . . . . . . . .  23
       3.7.5.  Negotiation Message . . . . . . . . . . . . . . . . .  24
       3.7.6.  Negotiation-ending Message  . . . . . . . . . . . . .  24
       3.7.7.  Confirm-waiting Message . . . . . . . . . . . . . . .  25
     3.8.  GRASP General Options . . . . . . . . . . . . . . . . . .  25
       3.8.1.  Format of GRASP Options . . . . . . . . . . . . . . .  25
       3.8.2.  Divert Option . . . . . . . . . . . . . . . . . . . .  25
       3.8.3.  Accept Option . . . . . . . . . . . . . . . . . . . .  26
       3.8.4.  Decline Option  . . . . . . . . . . . . . . . . . . .  26
       3.8.5.  Waiting Time Option . . . . . . . . . . . . . . . . .  27
       3.8.6.  Device Identity Option  . . . . . . . . . . . . . . .  27
       3.8.7.  Locator Options . . . . . . . . . . . . . . . . . . .  27
     3.9.  Objective Options . . . . . . . . . . . . . . . . . . . .  29
       3.9.1.  Format of Objective Options . . . . . . . . . . . . .  29
       3.9.2.  Objective flags . . . . . . . . . . . . . . . . . . .  30
       3.9.3.  General Considerations for Objective Options  . . . .  30



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       3.9.4.  Organizing of Objective Options . . . . . . . . . . .  31
       3.9.5.  Experimental and Example Objective Options  . . . . .  32
   4.  Open Issues . . . . . . . . . . . . . . . . . . . . . . . . .  32
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .  37
   6.  CDDL Specification of GRASP . . . . . . . . . . . . . . . . .  38
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  40
   8.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  41
   9.  Change log [RFC Editor: Please remove]  . . . . . . . . . . .  42
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .  43
     10.1.  Normative References . . . . . . . . . . . . . . . . . .  44
     10.2.  Informative References . . . . . . . . . . . . . . . . .  44
   Appendix A.  Capability Analysis of Current Protocols . . . . . .  48
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  50

1.  Introduction

   The success of the Internet has made IP-based networks bigger and
   more complicated.  Large-scale ISP and enterprise networks have
   become more and more problematic for human based management.  Also,
   operational costs are growing quickly.  Consequently, there are
   increased requirements for autonomic behavior in the networks.
   General aspects of autonomic networks are discussed in [RFC7575] and
   [RFC7576].  A reference model for autonomic networking is given in
   [I-D.behringer-anima-reference-model].  In order to fulfil autonomy,
   devices that embody autonomic service agents have specific signaling
   requirements.  In particular they need to discover each other, to
   synchronize state with each other, and to negotiate parameters and
   resources directly with each other.  There is no restriction on the
   type of parameters and resources concerned, which include very basic
   information needed for addressing and routing, as well as anything
   else that might be configured in a conventional non-autonomic
   network.  The atomic unit of synchronization or negotiation is
   referred to as a technical objective, i.e, a configurable parameter
   or set of parameters (defined more precisely in Section 3.1).

   Following this Introduction, Section 2 describes the requirements for
   discovery, synchronization and negotiation.  Negotiation is an
   iterative process, requiring multiple message exchanges forming a
   closed loop between the negotiating devices.  State synchronization,
   when needed, can be regarded as a special case of negotiation,
   without iteration.  Section 3.2 describes a behavior model for a
   protocol intended to support discovery, synchronization and
   negotiation.  The design of GeneRic Autonomic Signaling Protocol
   (GRASP) in Section 3 of this document is mainly based on this
   behavior model.  The relevant capabilities of various existing
   protocols are reviewed in Appendix A.





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   The proposed discovery mechanism is oriented towards synchronization
   and negotiation objectives.  It is based on a neighbor discovery
   process, but also supports diversion to off-link peers.  Although
   many negotiations will occur between horizontally distributed peers,
   many target scenarios are hierarchical networks, which is the
   predominant structure of current large-scale managed networks.
   However, when a device starts up with no pre-configuration, it has no
   knowledge of the topology.  The protocol itself is capable of being
   used in a small and/or flat network structure such as a small office
   or home network as well as a professionally managed network.
   Therefore, the discovery mechanism needs to be able to allow a device
   to bootstrap itself without making any prior assumptions about
   network structure.

   Because GRASP can be used to perform a decision process among
   distributed devices or between networks, it must run in a secure and
   strongly authenticated environment.

   It is understood that in realistic deployments, not all devices will
   support GRASP.  It is expected that some autonomic service agents
   will directly manage a group of non-autonomic nodes, and that other
   non-autonomic nodes will be managed traditionally.  Such mixed
   scenarios are not discussed in this specification.

2.  Requirement Analysis of Discovery, Synchronization and Negotiation

   This section discusses the requirements for discovery, negotiation
   and synchronization capabilities.  The primary user of the protocol
   is an autonomic service agent (ASA), so the requirements are mainly
   expressed as the features needed by an ASA.  A single physical device
   might contain several ASAs, and a single ASA might manage several
   technical objectives.

   Note that requirements for ASAs themselves, such as the processing of
   Intent [RFC7575] or interfaces for coordination between ASAs are out
   of scope for the present document.

2.1.  Requirements for Discovery

   1.  ASAs may be designed to manage anything, as required in
   Section 2.2.  A basic requirement is therefore that the protocol can
   represent and discover any kind of technical objective among
   arbitrary subsets of participating nodes.

   In an autonomic network we must assume that when a device starts up
   it has no information about any peer devices, the network structure,
   or what specific role it must play.  The ASA(s) inside the device are
   in the same situation.  In some cases, when a new application session



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   starts up within a device, the device or ASA may again lack
   information about relevant peers.  It might be necessary to set up
   resources on multiple other devices, coordinated and matched to each
   other so that there is no wasted resource.  Security settings might
   also need updating to allow for the new device or user.  The relevant
   peers may be different for different technical objectives.  Therefore
   discovery needs to be repeated as often as necessary to find peers
   capable of acting as counterparts for each objective that a discovery
   initiator needs to handle.  From this background we derive the next
   three requirements:

   2.  When an ASA first starts up, it has no knowledge of the specific
   network to which it is attached.  Therefore the discovery process
   must be able to support any network scenario, assuming only that the
   device concerned is bootstrapped from factory condition.

   3.  When an ASA starts up, it must require no information about any
   peers in order to discover them.

   4.  If an ASA supports multiple technical objectives, relevant peers
   may be different for different discovery objectives, so discovery
   needs to be repeated to find counterparts for each objective.  Thus,
   there must be a mechanism by which an ASA can separately discover
   peer ASAs for each of the technical objectives that it needs to
   manage, whenever necessary.

   5.  Following discovery, an ASA will normally perform negotiation or
   synchronization for the corresponding objectives.  The design should
   allow for this by associating discovery, negotiation and
   synchronization objectives.  It may provide an optional mechanism to
   combine discovery and negotiation/synchronization in a single call.

   6.  Some objectives may only be significant on the local link, but
   others may be significant across the routed network and require off-
   link operations.  Thus, the relevant peers might be immediate
   neighbors on the same layer 2 link, or they might be more distant and
   only accessible via layer 3.  The mechanism must therefore provide
   both on-link and off-link discovery of ASAs supporting specific
   technical objectives.

   7.  The discovery process should be flexible enough to allow for
   special cases, such as the following:

   o  In some networks, as mentioned above, there will be some
      hierarchical structure, at least for certain synchronization or
      negotiation objectives, but this is unknown in advance.  The
      discovery protocol must therefore operate regardless of
      hierarchical structure, which is an attribute of individual



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      technical objectives and not of the autonomic network as a whole.
      This is part of the more general requirement to discover off-link
      peers.

   o  During initialisation, a device must be able to establish mutual
      trust with the rest of the network and join an authentication
      mechanism.  Although this will inevitably start with a discovery
      action, it is a special case precisely because trust is not yet
      established.  This topic is the subject of
      [I-D.ietf-anima-bootstrapping-keyinfra].  We require that once
      trust has been established for a device, all ASAs within the
      device inherit the device's credentials and are also trusted.

   o  Depending on the type of network involved, discovery of other
      central functions might be needed, such as the Network Operations
      Center (NOC) [I-D.eckert-anima-stable-connectivity].  The protocol
      must be capable of supporting such discovery during
      initialisation, as well as discovery during ongoing operation.

   8.  The discovery process must not generate excessive (multicast)
   traffic and must take account of sleeping nodes in the case of a
   resource-constrained network [RFC7228].

2.2.  Requirements for Synchronization and Negotiation Capability

   As background, consider the example of routing protocols, the closest
   approximation to autonomic networking already in widespread use.
   Routing protocols use a largely autonomic model based on distributed
   devices that communicate repeatedly with each other.  The focus is
   reachability, so current routing protocols mainly consider simple
   link status, i.e., up or down, and an underlying assumption is that
   all nodes need a consistent view of the network topology in order for
   the routing algorithm to converge.  Thus, routing is mainly based on
   information synchronization between peers, rather than on bi-
   directional negotiation.  Other information, such as latency,
   congestion, capacity, and particularly unused capacity, would be
   helpful to get better path selection and utilization rate, but is not
   normally used in distributed routing algorithms.  Additionally,
   autonomic networks need to be able to manage many more dimensions,
   such as security settings, power saving, load balancing, etc.  Status
   information and traffic metrics need to be shared between nodes for
   dynamic adjustment of resources and for monitoring purposes.  While
   this might be achieved by existing protocols when they are available,
   the new protocol needs to be able to support parameter exchange,
   including mutual synchronization, even when no negotiation as such is
   required.  In general, these parameters do not apply to all
   participating nodes, but only to a subset.




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   9.  A basic requirement for the protocol is therefore the ability to
   represent, discover, synchronize and negotiate almost any kind of
   network parameter among arbitrary subsets of participating nodes.

   10.  Negotiation is a request/response process that must be
   guaranteed to terminate (with success or failure) and if necessary it
   must contain tie-breaking rules for each technical objective that
   requires them.  While these must be defined specifically for each use
   case, the protocol should have some general mechanisms in support of
   loop and deadlock prevention, such as hop count limits or timeouts.

   11.  Synchronization might concern small groups of nodes or very
   large groups.  Different solutions might be needed at different
   scales.

   12.  To avoid "reinventing the wheel", the protocol should be able to
   carry the message formats used by existing configuration protocols
   (such as NETCONF/YANG) in cases where that is convenient.

   13.  Human intervention in complex situations is costly and error-
   prone.  Therefore, synchronization or negotiation of parameters
   without human intervention is desirable whenever the coordination of
   multiple devices can improve overall network performance.  It
   therefore follows that the protocol, as part of the Autonomic
   Networking Infrastructure, must be capable of running in any device
   that would otherwise need human intervention.

   14.  Human intervention in large networks is often replaced by use of
   a top-down network management system (NMS).  It therefore follows
   that the protocol, as part of the Autonomic Networking
   Infrastructure, must be capable of running in any device that would
   otherwise be managed by an NMS, and that it can co-exist with an NMS,
   and with protocols such as SNMP and NETCONF.

   15.  Some features are expected to be implemented by individual ASAs,
   but the protocol must be general enough to allow them:

   o  Dependencies and conflicts: In order to decide a configuration on
      a given device, the device may need information from neighbors.
      This can be established through the negotiation procedure, or
      through synchronization if that is sufficient.  However, a given
      item in a neighbor may depend on other information from its own
      neighbors, which may need another negotiation or synchronization
      procedure to obtain or decide.  Therefore, there are potential
      dependencies and conflicts among negotiation or synchronization
      procedures.  Resolving dependencies and conflicts is a matter for
      the individual ASAs involved.  To allow this, there need to be
      clear boundaries and convergence mechanisms for negotiations.



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      Also some mechanisms are needed to avoid loop dependencies.  In
      such a case, the protocol's role is limited to signaling between
      ASAs.

   o  Recovery from faults and identification of faulty devices should
      be as automatic as possible.  The protocol's role is limited to
      the ability to handle discovery, synchronization and negotiation
      at any time, in case an ASA detects an anomaly such as a
      negotiation counterpart failing.

   o  Since the goal is to minimize human intervention, it is necessary
      that the network can in effect "think ahead" before changing its
      parameters.  In other words there must be a possibility of
      forecasting the effect of a change by a "dry run" mechanism before
      actually installing the change.  This will be an application of
      the protocol rather than a feature of the protocol itself.

   o  Management logging, monitoring, alerts and tools for intervention
      are required.  However, these can only be features of individual
      ASAs.  Another document [I-D.eckert-anima-stable-connectivity]
      discusses how such agents may be linked into conventional OAM
      systems via an Autonomic Control Plane
      [I-D.ietf-anima-autonomic-control-plane].

   16.  The protocol will be able to deal with a wide variety of
   technical objectives, covering any type of network parameter.
   Therefore the protocol will need either an explicit information model
   describing its messages, or at least a flexible and easily extensible
   message format.  One design consideration is whether to adopt an
   existing information model or to design a new one.

2.3.  Specific Technical Requirements

   17.  It should be convenient for ASA designers to define new
   technical objectives and for programmers to express them, without
   excessive impact on run-time efficiency and footprint.  The classes
   of device in which the protocol might run is discussed in
   [I-D.behringer-anima-reference-model].

   18.  The protocol should be easily extensible in case the initially
   defined discovery, synchronization and negotiation mechanisms prove
   to be insufficient.

   19.  To be a generic platform, the protocol payload format should be
   independent of the transport protocol or IP version.  In particular,
   it should be able to run over IPv6 or IPv4.  However, some functions,
   such as multicasting or broadcasting on a link, might need to be IP
   version dependent.  In case of doubt, IPv6 should be preferred.



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   20.  The protocol must be able to access off-link counterparts via
   routable addresses, i.e., must not be restricted to link-local
   operation.

   21.  It must also be possible for an external discovery mechanism to
   be used, if appropriate for a given technical objective.  In other
   words, GRASP discovery must not be a prerequisite for GRASP
   negotiation or synchronization; the prerequisite is discovering a
   peer's locator by any method.

   22.  ASAs and the signaling protocol engine need to run
   asynchronously when wait states occur.

   23.  Intent: There must be provision for general Intent rules to be
   applied by all devices in the network (e.g., security rules, prefix
   length, resource sharing rules).  However, Intent distribution might
   not use the signaling protocol itself, but its design should not
   exclude such use.

   24.  Management monitoring, alerts and intervention: Devices should
   be able to report to a monitoring system.  Some events must be able
   to generate operator alerts and some provision for emergency
   intervention must be possible (e.g.  to freeze synchronization or
   negotiation in a mis-behaving device).  These features might not use
   the signaling protocol itself, but its design should not exclude such
   use.

   25.  The protocol needs to be fully secured against forged messages
   and man-in-the middle attacks, and secured as much as reasonably
   possible against denial of service attacks.  It needs to be capable
   of encryption in order to resist unwanted monitoring, although this
   capability may not be required in all deployments.  However, it is
   not required that the protocol itself provides these security
   features; it may depend on an existing secure environment.

3.  GRASP Protocol Overview

3.1.  Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in
   [RFC2119] when they appear in ALL CAPS.  When these words are not in
   ALL CAPS (such as "should" or "Should"), they have their usual
   English meanings, and are not to be interpreted as [RFC2119] key
   words.

   This document uses terminology defined in [RFC7575].



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   The following additional terms are used throughout this document:

   o  Autonomic Device: identical to Autonomic Node.

   o  Discovery: a process by which an ASA discovers peers according to
      a specific discovery objective.  The discovery results may be
      different according to the different discovery objectives.  The
      discovered peers may later be used as negotiation counterparts or
      as sources of synchronization data.

   o  Negotiation: a process by which two (or more) ASAs interact
      iteratively to agree on parameter settings that best satisfy the
      objectives of one or more ASAs.

   o  State Synchronization: a process by which two (or more) ASAs
      interact to agree on the current state of parameter values stored
      in each ASA.  This is a special case of negotiation in which
      information is sent but the ASAs do not request their peers to
      change parameter settings.  All other definitions apply to both
      negotiation and synchronization.

   o  Technical Objective (usually abbreviated as Objective): A
      technical objective is a configurable parameter or set of
      parameters of some kind, which occurs in three contexts:
      Discovery, Negotiation and Synchronization.  In the protocol, an
      objective is represented by an identifier (actually a GRASP option
      number) and if relevant a value.  Normally, a given objective will
      occur during discovery and negotiation, or during discovery and
      synchronization, but not in all three contexts.

      *  One ASA may support multiple independent objectives.

      *  The parameter described by a given objective is naturally based
         on a specific service or function or action.  It may in
         principle be anything that can be set to a specific logical,
         numerical or string value, or a more complex data structure, by
         a network node.  That node is generally expected to contain an
         ASA which may itself manage other nodes.

      *  Discovery Objective: if a node needs to synchronize or
         negotiate a specific objective but does not know a peer that
         supports this objective, it starts a discovery process.  The
         objective is called a Discovery Objective during this process.

      *  Synchronization Objective: an objective whose specific
         technical content needs to be synchronized among two or more
         ASAs.




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      *  Negotiation Objective: an objective whose specific technical
         content needs to be decided in coordination with another ASA.

   o  Discovery Initiator: an ASA that spontaneously starts discovery by
      sending a discovery message referring to a specific discovery
      objective.

   o  Discovery Responder: a peer ASA which responds to the discovery
      objective initiated by the discovery initiator.

   o  Synchronization Initiator: an ASA that spontaneously starts
      synchronization by sending a request message referring to a
      specific synchronization objective.

   o  Synchronization Responder: a peer ASA which responds with the
      value of a synchronization objective.

   o  Negotiation Initiator: an ASA that spontaneously starts
      negotiation by sending a request message referring to a specific
      negotiation objective.

   o  Negotiation Counterpart: a peer with which the Negotiation
      Initiator negotiates a specific negotiation objective.

3.2.  High-Level Design Choices

   This section describes a behavior model and some considerations for
   designing a generic signaling protocol initially supporting
   discovery, synchronization and negotiation, which can act as a
   platform for different technical objectives.

   NOTE: An earlier version of this protocol used type-length-value
   formats and was prototyped by Huawei and the Beijing University of
   Posts and Telecommunications.

   o  A generic platform

      The protocol is designed as a generic platform, which is
      independent from the synchronization or negotiation contents.  It
      takes care of the general intercommunication between counterparts.
      The technical contents will vary according to the various
      technical objectives and the different pairs of counterparts.


   o  The protocol is expected to form part of an Autonomic Networking
      Infrastructure [I-D.behringer-anima-reference-model].  It will
      provide services to ASAs via a suitable application programming
      interface, which will reflect the protocol elements but will not



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      necessarily be in one-to-one correspondence to them.  It is
      expected that the protocol engine and each ASA will run as
      independent asynchronous processes.


   o  Security infrastructure and trust relationship

      Because this negotiation protocol may directly cause changes to
      device configurations and bring significant impacts to a running
      network, this protocol is assumed to run within an existing secure
      environment with strong authentication.

      On the other hand, a limited negotiation model might be deployed
      based on a limited trust relationship.  For example, between two
      administrative domains, ASAs might also exchange limited
      information and negotiate some particular configurations based on
      a limited conventional or contractual trust relationship.


   o  Discovery, synchronization and negotiation are designed together.

      The discovery method and the synchronization and negotiation
      methods are designed in the same way and can be combined when this
      is useful.  These processes can also be performed independently
      when appropriate.

      *  GRASP discovery is always available for efficient discovery of
         GRASP peers and allows a rapid mode of operation described in
         Section 3.3.3.  For some objectives, especially those concerned
         with application layer services, another discovery mechanism
         such as the future DNS Service Discovery [RFC7558] or Service
         Location Protocol [RFC2608] MAY be used.  The choice is left to
         the designers of individual ASAs.


   o  A uniform pattern for technical contents

      The synchronization and negotiation contents are defined according
      to a uniform pattern.  They could be carried either in simple
      binary format or in payloads described by a flexible language.
      The basic protocol design uses the Concise Binary Object
      Representation (CBOR) [RFC7049].  The format is extensible for
      unknown future requirements.


   o  A flexible model for synchronization





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      GRASP supports bilateral synchronization, which could be used to
      perform synchronization among a small number of nodes.  It also
      supports an unsolicited flooding mode when large groups of nodes,
      possibly including all autonomic nodes, need data for the same
      technical objective.

      *  There may be some network parameters for which a more
         traditional flooding mechanism such as DNCP
         [I-D.ietf-homenet-dncp] is considered more appropriate.  GRASP
         can coexist with DNCP.


   o  A simple initiator/responder model for negotiation

      Multi-party negotiations are too complicated to be modeled and
      there might be too many dependencies among the parties to converge
      efficiently.  A simple initiator/responder model is more feasible
      and can complete multi-party negotiations by indirect steps.


   o  Organizing of synchronization or negotiation content

      Naturally, the technical content will be organized according to
      the relevant function or service.  The content from different
      functions or services is kept independent from each other.  They
      are not combined into a single option or single session because
      these contents may be negotiated or synchronized with different
      counterparts or may be different in response time.


   o  Self-aware network device

      Every autonomic device will be pre-loaded with various functions
      and ASAs and will be aware of its own capabilities, typically
      decided by the hardware, firmware or pre-installed software.  Its
      exact role may depend on Intent and on the surrounding network
      behaviors, which may include forwarding behaviors, aggregation
      properties, topology location, bandwidth, tunnel or translation
      properties, etc.  The surrounding topology will depend on the
      network planning.  Following an initial discovery phase, the
      device properties and those of its neighbors are the foundation of
      the synchronization or negotiation behavior of a specific device.
      A device has no pre-configuration for the particular network in
      which it is installed.


   o  Requests and responses in negotiation procedures




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      The initiator can negotiate with its relevant negotiation
      counterpart ASAs, which may be different according to the specific
      negotiation objective.  It can request relevant information from
      the negotiation counterpart so that it can decide its local
      configuration to give the most coordinated performance.  It can
      request the negotiation counterpart to make a matching
      configuration in order to set up a successful communication with
      it.  It can request certain simulation or forecast results by
      sending some dry run conditions.

      Beyond the traditional yes/no answer, the responder can reply with
      a suggested alternative if its answer is 'no'.  This would start a
      bi-directional negotiation ending in a compromise between the two
      ASAs.


   o  Convergence of negotiation procedures

      To enable convergence, when a responder makes a suggestion of a
      changed condition in a negative reply, it should be as close as
      possible to the original request or previous suggestion.  The
      suggested value of the third or later negotiation steps should be
      chosen between the suggested values from the last two negotiation
      steps.  In any case there must be a mechanism to guarantee
      convergence (or failure) in a small number of steps, such as a
      timeout or maximum number of iterations.



      *  End of negotiation

         A limited number of rounds, for example three, or a timeout, is
         needed on each ASA for each negotiation objective.  It may be
         an implementation choice, a pre-configurable parameter, or
         network Intent.  These choices might vary between different
         types of ASA.  Therefore, the definition of each negotiation
         objective MUST clearly specify this, so that the negotiation
         can always be terminated properly.


      *  Failed negotiation

         There must be a well-defined procedure for concluding that a
         negotiation cannot succeed, and if so deciding what happens
         next (deadlock resolution, tie-breaking, or revert to best-
         effort service).  Again, this MUST be specified for individual
         negotiation objectives, as an implementation choice, a pre-
         configurable parameter, or network Intent.



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3.3.  GRASP Protocol Basic Properties and Mechanisms

3.3.1.  Required External Security Mechanism

   The protocol SHOULD run within a secure Autonomic Control Plane (ACP)
   [I-D.ietf-anima-autonomic-control-plane].  The ACP MUST provide a
   status indicator to inform GRASP that the ACP is operational.

   If there is no ACP, the protocol MUST use another form of strong
   authentication and SHOULD use a form of strong encryption.  TLS
   [RFC5246] or DTLS [RFC6347] are RECOMMENDED for this purpose, based
   on a local Public Key Infrastructure (PKI) [RFC5280] managed within
   the autonomic network itself.

   Link-local multicast is used for discovery messages.  It is expected
   that the ACP will handle these and distribute them securely to all
   on-link ACP nodes only.  However, in the absence of an ACP they
   cannot be secured.  Responses to discovery messages MUST be secured.

   During initialisation, before a node has joined the applicable trust
   infrastructure, e.g., [I-D.ietf-anima-bootstrapping-keyinfra], it
   might be impossible to secure certain messages.  Such messages MUST
   be limited to the strictly necessary minimum.  A full analysis of the
   secure bootstrap process is out of scope for the present document.

3.3.2.  Transport Layer Usage

   The protocol is capable of running over UDP or TCP, except for link-
   local multicast discovery messages, which can only run over UDP and
   MUST NOT be fragmented, and therefore cannot exceed the link MTU
   size.

   When running within a secure ACP, UDP SHOULD be used for messages not
   exceeding the minimum IPv6 path MTU, and TCP MUST be used for longer
   messages.  In other words, IPv6 fragmentation is avoided.  If a node
   receives a UDP message but the reply is too long, it MUST open a TCP
   connection to the peer for the reply.

   When running without an ACP, TLS MUST be supported and used by
   default, except for multicast discovery messages.  DTLS MAY be
   supported as an alternative but the details are out of scope for this
   document.

   For all transport protocols, the GRASP protocol listens to the GRASP
   Listen Port (Section 3.5).






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3.3.3.  Discovery Mechanism and Procedures

   o  Separated discovery and negotiation mechanisms

         Although discovery and negotiation or synchronization are
         defined together in the GRASP, they are separated mechanisms.
         The discovery process could run independently from the
         negotiation or synchronization process.  Upon receiving a
         discovery (Section 3.7.2) or request (Section 3.7.4) message,
         the recipient ASA should return a message in which it either
         indicates itself as a discovery responder or diverts the
         initiator towards another more suitable ASA.

         The discovery action will normally be followed by a negotiation
         or synchronization action.  The discovery results could be
         utilized by the negotiation protocol to decide which ASA the
         initiator will negotiate with.

   o  Discovery Procedures

         Discovery starts as an on-link operation.  The Divert option
         can tell the discovery initiator to contact an off-link ASA for
         that discovery objective.  Every Discovery message is sent by a
         discovery initiator via UDP to the ALL_GRASP_NEIGHBOR multicast
         address (Section 3.5).  Every network device that supports the
         GRASP always listens to a well-known UDP port to capture the
         discovery messages.

         If an ASA in the neighbor device supports the requested
         discovery objective, it MAY respond with a Response message
         (Section 3.7.3) with locator option(s).  Otherwise, if the
         neighbor has cached information about an ASA that supports the
         requested discovery objective (usually because it discovered
         the same objective before), it SHOULD respond with a Response
         message with a Divert option pointing to the appropriate
         Discovery Responder.

         If no discovery response is received within a reasonable
         timeout (default GRASP_DEF_TIMEOUT milliseconds, Section 3.5),
         the Discovery message MAY be repeated, with a newly generated
         Session ID (Section 3.6).  An exponential backoff SHOULD be
         used for subsequent repetitions, in order to mitigate possible
         denial of service attacks.

         After a GRASP device successfully discovers a Discovery
         Responder supporting a specific objective, it MUST cache this
         information.  This cache record MAY be used for future
         negotiation or synchronization, and SHOULD be passed on when



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         appropriate as a Divert option to another Discovery Initiator.
         The cache lifetime is an implementation choice that MAY be
         modified by network Intent.

         If multiple Discovery Responders are found for the same
         objective, they SHOULD all be cached, unless this creates a
         resource shortage.  The method of choosing between multiple
         responders is an implementation choice.

         A GRASP device with multiple link-layer interfaces (typically a
         router) MUST support discovery on all interfaces.  If it
         receives a Discovery message on a given interface for a
         specific objective that it does not support and for which it
         has not previously discovered a Discovery Responder, it MUST
         relay the query by re-issuing the same Discovery message on its
         other interfaces.  Before this, it MUST decrement the loop
         count within the objective, and discard the Discovery message
         if the result is zero.  Also, it MUST limit the total rate at
         which it relays discovery messages to a reasonable value, in
         order to mitigate possible denial of service attacks.  It MUST
         cache the Session ID value of each relayed discovery message
         and, to prevent loops, MUST NOT relay a Discovery message which
         carries such a cached Session ID.  These precautions avoid
         discovery loops and mitigate potential overload.

         This relayed discovery mechanism, with caching of the results,
         should be sufficient to support most network bootstrapping
         scenarios.

   o  A complete discovery process will start with multicast on the
      local link; a neighbor might divert it to an off-link destination,
      which could be a default higher-level gateway in a hierarchical
      network.  Then discovery would continue with a unicast to that
      gateway; if that gateway is still not the right counterpart, it
      should divert to another gateway, which is in principle closer to
      the right counterpart.  Finally the right counterpart responds to
      start the negotiation or synchronization process.

   o  Rapid Mode (Discovery/Negotiation binding)

         A Discovery message MAY include one or more Negotiation
         Objective option(s).  This allows a rapid mode of negotiation
         described in Section 3.3.4.  A similar mechanism is defined for
         synchronization in Section 3.3.5.







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3.3.4.  Negotiation Procedures

   A negotiation initiator sends a negotiation request to a counterpart
   ASA, including a specific negotiation objective.  It may request the
   negotiation counterpart to make a specific configuration.
   Alternatively, it may request a certain simulation or forecast result
   by sending a dry run configuration.  The details, including the
   distinction between dry run and an actual configuration change, will
   be defined separately for each type of negotiation objective.

   If no reply message of any kind is received within a reasonable
   timeout (default GRASP_DEF_TIMEOUT milliseconds, Section 3.5), the
   negotiation request MAY be repeated, with a newly generated Session
   ID (Section 3.6).  An exponential backoff SHOULD be used for
   subsequent repetitions.

   If the counterpart can immediately apply the requested configuration,
   it will give an immediate positive (accept) answer.  This will end
   the negotiation phase immediately.  Otherwise, it will negotiate.  It
   will reply with a proposed alternative configuration that it can
   apply (typically, a configuration that uses fewer resources than
   requested by the negotiation initiator).  This will start a bi-
   directional negotiation to reach a compromise between the two ASAs.

   The negotiation procedure is ended when one of the negotiation peers
   sends a Negotiation Ending message, which contains an accept or
   decline option and does not need a response from the negotiation
   peer.  Negotiation may also end in failure (equivalent to a decline)
   if a timeout is exceeded or a loop count is exceeded.

   A negotiation procedure concerns one objective and one counterpart.
   Both the initiator and the counterpart may take part in simultaneous
   negotiations with various other ASAs, or in simultaneous negotiations
   about different objectives.  Thus, GRASP is expected to be used in a
   multi-threaded mode.  Certain negotiation objectives may have
   restrictions on multi-threading, for example to avoid over-allocating
   resources.

   Rapid Mode (Discovery/Negotiation linkage)

      A Discovery message MAY include a Negotiation Objective option.
      In this case the Discovery message also acts as a Request message
      to indicate to the Discovery Responder that it could directly
      reply to the Discovery Initiator with a Negotiation message for
      rapid processing, if it could act as the corresponding negotiation
      counterpart.  However, the indication is only advisory not
      prescriptive.




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      This rapid mode could reduce the interactions between nodes so
      that a higher efficiency could be achieved.  This rapid
      negotiation function SHOULD be configured off by default and MAY
      be configured on or off by Intent.

3.3.5.  Synchronization Procedure

   A synchronization initiator sends a synchronization request to a
   counterpart, including a specific synchronization objective.  The
   counterpart responds with a Response message containing the current
   value of the requested synchronization objective.  No further
   messages are needed.

   If no reply message of any kind is received within a reasonable
   timeout (default GRASP_DEF_TIMEOUT milliseconds, Section 3.5), the
   synchronization request MAY be repeated, with a newly generated
   Session ID (Section 3.6).  An exponential backoff SHOULD be used for
   subsequent repetitions.

   In the case just described, the message exchange is unicast and
   concerns only one synchronization objective.  For large groups of
   nodes requiring the same data, synchronization flooding is available.
   For this, a synchronization responder MAY send an unsolicited
   Response message containing one or more Synchronization Objective
   option(s), if and only if the specification of those objectives
   permits it.  This is sent as a multicast message to the
   ALL_GRASP_NEIGHBOR multicast address (Section 3.5).  To ensure that
   flooding does not result in a loop, the originator of the Response
   message MUST set the loop count in the objective to a suitable value
   (the default is GRASP_DEF_LOOPCT).  In this case a suitable mechanism
   is needed to avoid excessive multicast traffic.  This mechanism MUST
   be defined as part of the specification of the synchronization
   objective(s) concerned.  It might be a simple rate limit or a more
   complex mechanism such as the Trickle algorithm [RFC6206].

   A GRASP device with multiple link-layer interfaces (typically a
   router) MUST support synchronization flooding on all interfaces.  If
   it receives a multicast unsolicited Response message on a given
   interface, it MUST relay it by re-issuing the same Response message
   on its other interfaces.  Before this, it MUST decrement the loop
   count within the objective, and discard the Response message if the
   result is zero.  Also, it MUST limit the total rate at which it
   relays Response messages to a reasonable value, in order to mitigate
   possible denial of service attacks.  It MUST cache the Session ID
   value of each relayed Response message and, to prevent loops, MUST
   NOT relay a Response message which carries such a cached Session ID.
   These precautions avoid synchronization loops and mitigate potential
   overload.



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   Note that this mechanism is unreliable in the case of sleeping nodes.
   Sleeping nodes that require an objective subject to synchronization
   flooding SHOULD periodically initiate normal synchronization for that
   objective.

   Rapid Mode (Discovery/Synchronization linkage)

      A Discovery message MAY include one or more Synchronization
      Objective option(s).  In this case the Discovery message also acts
      as a Request message to indicate to the Discovery Responder that
      it could directly reply to the Discovery Initiator with a Response
      message with synchronization data for rapid processing, if the
      discovery target supports the corresponding synchronization
      objective(s).  However, the indication is only advisory not
      prescriptive.

      This rapid mode could reduce the interactions between nodes so
      that a higher efficiency could be achieved.  This rapid
      synchronization function SHOULD be configured off by default and
      MAY be configured on or off by Intent.

3.4.  High Level Deployment Model

   It is expected that a GRASP implementation will reside in an
   autonomic node that also contains both the appropriate security
   environment (preferably the ACP) and one or more Autonomic Service
   Agents (ASAs).  In the minimal case of a single-purpose device, these
   three components might be fully integrated.  A more common model is
   expected to be a multi-purpose device capable of containing several
   ASAs.  In this case it is expected that the ACP, GRASP and the ASAs
   will be implemented as separate processes, which are probably multi-
   threaded to support asynchronous operation.  It is expected that
   GRASP will access the ACP by using a typical socket interface.  Well
   defined Application Programming Interfaces (APIs) will be needed
   between GRASP and the ASAs.  For further details of possible
   deployment models, see [I-D.behringer-anima-reference-model].

3.5.  GRASP Constants

   o  ALL_GRASP_NEIGHBOR

      A link-local scope multicast address used by a GRASP-enabled
      device to discover GRASP-enabled neighbor (i.e., on-link) devices
      . All devices that support GRASP are members of this multicast
      group.

      *  IPv6 multicast address: TBD1




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      *  IPv4 multicast address: TBD2

   o  GRASP_LISTEN_PORT (TBD3)

      A UDP and TCP port that every GRASP-enabled network device always
      listens to.

   o  GRASP_DEF_TIMEOUT (60000 milliseconds)

      The default timeout used to determine that a discovery etc. has
      failed to complete.

   o  GRASP_DEF_LOOPCT (6)

      The default loop count used to determine that a negotiation has
      failed to complete, and to avoid looping messages.

3.6.  Session Identifier (Session ID)

   This is an up to 24-bit opaque value used to distinguish multiple
   sessions between the same two devices.  A new Session ID MUST be
   generated for every new Discovery or Request message, and for every
   unsolicited Response message.  All follow-up messages in the same
   discovery, synchronization or negotiation procedure, which is
   initiated by the request message, MUST carry the same Session ID.

   The Session ID SHOULD have a very low collision rate locally.  It
   MUST be generated by a pseudo-random algorithm using a locally
   generated seed which is unlikely to be used by any other device in
   the same network [RFC4086].

3.7.  GRASP Messages

   This section defines the GRASP message format and message types.
   Message types not listed here are reserved for future use.

3.7.1.  GRASP Message Format

   GRASP messages share an identical header format and a variable format
   area for options.  GRASP message headers and options are transmitted
   in Concise Binary Object Representation (CBOR) [RFC7049].  In this
   specification, they are described using CBOR data definition language
   (CDDL) [I-D.greevenbosch-appsawg-cbor-cddl].  Fragmentary CDDL is
   used to describe each item in this section.  A complete and normative
   CDDL specification of GRASP is given in Section 6.

   Every GRASP message carries a Session ID (Section 3.6).  Options are
   then presented serially in the options field.



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   In fragmentary CDDL, every GRASP message follows the pattern:

     message /= [MESSAGE_TYPE, session-id, *option]

     MESSAGE_TYPE = ; a defined constant
     session-id =   0..16777215
     option /=      ; one of the options defined below

3.7.2.  Discovery Message

   In fragmentary CDDL, a Discovery message follows the pattern:

     discovery-message = [M_DISCOVERY, session-id, objective]

     M_DISCOVERY =  ; a defined constant
     session-id =   0..16777215
     objective /=   ; defined below

   A discovery initiator sends a Discovery message to initiate a
   discovery process.

   The discovery initiator sends the Discovery messages to the link-
   local ALL_GRASP_NEIGHBOR multicast address for discovery, and stores
   the discovery results (including responding discovery objectives and
   corresponding unicast addresses or FQDNs).

   A Discovery message MUST include exactly one of the following:

   o  a discovery objective option (Section 3.9.1).  Its loop count must
      be set to a suitable value to prevent discovery loops (default
      value is GRASP_DEF_LOOPCT).

   o  a negotiation objective option (Section 3.9.1) to indicate to the
      discovery target that it MAY directly reply to the discovery
      initiatior with a Negotiation message for rapid processing, if it
      could act as the corresponding negotiation counterpart.  The
      sender of such a Discovery message MUST initialize a negotiation
      timer and loop count in the same way as a Request message
      (Section 3.7.4).

   o  one or more synchronization objective options (Section 3.9.1) to
      indicate to the discovery target that it MAY directly reply to the
      discovery initiator with a Response message for rapid processing,
      if it could act as the corresponding synchronization counterpart.







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3.7.3.  Response Message

   In fragmentary CDDL, a Response message follows the pattern:

     response-message = [M_RESPONSE, session-id,
                        (+locator-option // divert-option // objective)]

     M_RESPONSE =       ; a defined constant
     session-id =       0..16777215
     locator-option /=  ; defined below
     divert-option =    ; defined below
     objective /=       ; defined below

   A node which receives a Discovery message sends a Response message to
   respond to a discovery.  It MUST contain the same Session ID as the
   Discovery message.  It MAY include a copy of the discovery objective
   from the Discovery message.

   If the responding node supports the discovery objective of the
   discovery, it MUST include at least one kind of locator option
   (Section 3.8.7) to indicate its own location.  A combination of
   multiple kinds of locator options (e.g.  IP address option + FQDN
   option) is also valid.

   If the responding node itself does not support the discovery
   objective, but it knows the locator of the discovery objective, then
   it SHOULD respond to the discovery message with a divert option
   (Section 3.8.2) embedding a locator option or a combination of
   multiple kinds of locator options which indicate the locator(s) of
   the discovery objective.

   A node which receives a synchronization request sends a Response
   message with the synchronization data, in the form of GRASP Option(s)
   for the specific synchronization objective(s).

3.7.4.  Request Message

   In fragmentary CDDL, a Request message follows the pattern:

     discovery-message = [M_REQUEST, session-id, objective]

     M_REQUEST =    ; a defined constant
     session-id =   0..16777215
     objective /=   ; defined below

   A negotiation or synchronization requesting node sends the Request
   message to the unicast address (directly stored or resolved from the




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   FQDN) of the negotiation or synchronization counterpart (selected
   from the discovery results).

   A request message MUST include the relevant objective option, with
   the requested value in the case of negotiation.

   When an initiator sends a Request message, it MUST initialize a
   negotiation timer for the new negotiation thread with the value
   GRASP_DEF_TIMEOUT milliseconds.  Unless this timeout is modified by a
   Confirm-waiting message (Section 3.7.7), the initiator will consider
   that the negotiation has failed when the timer expires.

   When an initiator sends a Request message, it MUST initialize the
   loop count of the objective option with a value defined in the
   specification of the option or, if no such value is specified, with
   GRASP_DEF_LOOPCT.

3.7.5.  Negotiation Message

   In fragmentary CDDL, a Negotiation message follows the pattern:

     discovery-message = [M_NEGOTIATE, session-id, objective]

     M_NEGOTIATE =  ; a defined constant
     session-id =   0..16777215
     objective /=   ; defined below

   A negotiation counterpart sends a Negotiation message in response to
   a Request message, a Negotiation message, or a Discovery message in
   Rapid Mode.  A negotiation process MAY include multiple steps.

   The Negotiation message MUST include the relevant Negotiation
   Objective option, with its value updated according to progress in the
   negotiation.  The sender MUST decrement the loop count by 1.  If the
   loop count becomes zero both parties will consider that the
   negotiation has failed.

3.7.6.  Negotiation-ending Message

   In fragmentary CDDL, a Negotiation-ending message follows the
   pattern:

     end-message = [M_END, session-id, accept-option / decline-option]

     M_END =          ; a defined constant
     session-id =     0..16777215
     accept-option =  ; defined below
     decline-option   ; defined below



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   A negotiation counterpart sends an Negotiation-ending message to
   close the negotiation.  It MUST contain one, but only one of accept/
   decline option, defined in Section 3.8.3 and Section 3.8.4.  It could
   be sent either by the requesting node or the responding node.

3.7.7.  Confirm-waiting Message

   In fragmentary CDDL, a Confirm-waiting message follows the pattern:

     wait-message = [M_WAIT, session-id, waiting-time-option]

     M_WAIT =              ; a defined constant
     session-id =          0..16777215
     waiting-time-option = ; defined below

   A responding node sends a Confirm-waiting message to indicate the
   requesting node to wait for a further negotiation response.  It might
   be that the local process needs more time or that the negotiation
   depends on another triggered negotiation.  This message MUST NOT
   include any other options than the Waiting Time Option
   (Section 3.8.5).

3.8.  GRASP General Options

   This section defines the GRASP general options for the negotiation
   and synchronization protocol signaling.  Additional option types are
   reserved for GRASP general options defined in the future.

3.8.1.  Format of GRASP Options

   GRASP options are CBOR objects that MUST start with an unsigned
   integer identifying the specific option type carried in this option.
   Apart from that the only format requirement is each option MUST be a
   well-formed CBOR object.  In general a CBOR array format is
   RECOMMENDED to limit overhead.

   GRASP options are usually scoped by using encapsulation.  However,
   this is not a requirement

3.8.2.  Divert Option

   The Divert option is used to redirect a GRASP request to another
   node, which may be more appropriate for the intended negotiation or
   synchronization.  It may redirect to an entity that is known as a
   specific negotiation or synchronization counterpart (on-link or off-
   link) or a default gateway.  The divert option MUST only be
   encapsulated in Response messages.  If found elsewhere, it SHOULD be
   silently ignored.



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   In fragmentary CDDL, the Divert option follows the pattern:

     divert-option = [O_DIVERT, +locator-option]

     O_DIVERT =       ; a defined constant
     locator-option = ; defined below

   The embedded Locator Option(s) (Section 3.8.7) point to diverted
   destination target(s) in response to a Discovery message.

   Note: Currently the need for this option is disputed.  It might be
   removed or modified.

3.8.3.  Accept Option

   The accept option is used to indicate to the negotiation counterpart
   that the proposed negotiation content is accepted.

   The accept option MUST only be encapsulated in Negotiation-ending
   messages.  If found elsewhere, it SHOULD be silently ignored.

   In fragmentary CDDL, the Accept option follows the pattern:

     accept-option = [O_ACCEPT]

     O_ACCEPT =       ; a defined constant

3.8.4.  Decline Option

   The decline option is used to indicate to the negotiation counterpart
   the proposed negotiation content is declined and end the negotiation
   process.

   The decline option MUST only be encapsulated in Negotiation-ending
   messages.  If found elsewhere, it SHOULD be silently ignored.

   In fragmentary CDDL, the Decline option follows the pattern:

     decline-option = [O_DECLINE]

     O_DECLINE =       ; a defined constant

   Notes: there are scenarios where a negotiation counterpart wants to
   decline the proposed negotiation content and continue the negotiation
   process.  For these scenarios, the negotiation counterpart SHOULD use
   a Negotiate message, with either an objective option that contains a
   data field set to indicate a meaningless initial value, or a specific
   objective option that provides further conditions for convergence.



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3.8.5.  Waiting Time Option

   The waiting time option is used to indicate that the negotiation
   counterpart needs to wait for a further negotiation response, since
   the processing might need more time than usual or it might depend on
   another triggered negotiation.

   The waiting time option MUST only be encapsulated in Confirm-waiting
   messages.  If found elsewhere, it SHOULD be silently ignored.  When
   received, its value overwrites the negotiation timer (Section 3.7.4).

   The counterpart SHOULD send a Negotiation, Negotiation-Ending or
   another Confirm-waiting message before the negotiation timer expires.
   If not, the initiator MUST abandon or restart the negotiation
   procedure, to avoid an indefinite wait.

   In fragmentary CDDL, the Waiting-time option follows the pattern:

     waiting-time-option = [O_WAITING, option-waiting-time]

     O_WAITING =           ; a defined constant
     option-waiting-time = 0..4294967295 ; in milliseconds

3.8.6.  Device Identity Option

   The Device Identity option carries the identities of the sender and
   of the domain(s) that it belongs to.

   In fragmentary CDDL, the Device Identity option follows the pattern:

     option-device-id = [O_DEVICE_ID, bytes]

     O_DEVICE_ID =   ; a defined constant

   The option contains a variable-length field containing the device
   identity and one or more domain identities.  The format is not yet
   defined.

   Note: Currently this option is a placeholder.  It might be removed or
   modified.

3.8.7.  Locator Options

   These locator options are used to present reachability information
   for an ASA, a device or an interface.  They are Locator IPv4 Address
   Option, Locator IPv6 Address Option, Locator FQDN (Fully Qualified
   Domain Name) Option and Uniform Resource Locator Option.




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   Note: It is assumed that all locators are in scope throughout the
   GRASP domain.  GRASP is not intended to work across disjoint
   addressing or naming realms.

3.8.7.1.  Locator IPv4 address option

   In fragmentary CDDL, the IPv4 address option follows the pattern:

     ipv4-locator-option = bytes .size 4

   The content of this option is a binary IPv4 address.

   Note: If an operator has internal network address translation for
   IPv4, this option MUST NOT be used within the Divert option.

3.8.7.2.  Locator IPv6 address option

   In fragmentary CDDL, the IPv6 address option follows the pattern:

     ipv6-locator-option = bytes .size 16

   The content of this option is a binary IPv6 address.

   Note: A link-local IPv6 address MUST NOT be used when this option is
   used within the Divert option.

3.8.7.3.  Locator FQDN option

   In fragmentary CDDL, the FQDN option follows the pattern:

     fqdn-locator-option = [O_FQDN_LOCATOR, text]

     O_FQDN_LOCATOR =   ; a defined constant

   The content of this option is the Fully Qualified Domain Name of the
   target.

   Note: Any FQDN which might not be valid throughout the network in
   question, such as a Multicast DNS name [RFC6762], MUST NOT be used
   when this option is used within the Divert option.

3.8.7.4.  Locator URL option

   In fragmentary CDDL, the URL option follows the pattern:

     url-locator-option = [O_URL_LOCATOR, text]

     O_URL_LOCATOR =   ; a defined constant



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   The content of this option is the Uniform Resource Locator of the
   target [RFC3986].

   Note: Any URL which might not be valid throughout the network in
   question, such as one based on a Multicast DNS name [RFC6762], MUST
   NOT be used when this option is used within the Divert option.

3.9.  Objective Options

3.9.1.  Format of Objective Options

   An objective option is used to identify objectives for the purposes
   of discovery, negotiation or synchronization.  All objectives must
   follow one of two common formats as follows, described in fragmentary
   CDDL:

     generic-obj = [objective-name, objective-flags, loop-count, ?any]
     vendor-obj = [{"PEN":pen}, objective-name, objective-flags,
                   loop-count, ?any]

     objective-name = tstr
     pen = 0..4294967295
     loop-count = 0..255
     objective-flags \=     ; defined below

   All objectives are identified by a unique name which is a UTF-8
   string.  The names of generic objectives MUST be registered with
   IANA.

   The name "PEN" and the value following it MUST be prepended to
   indicate vendor-defined objectives.  The associated value uniquely
   identifies the enterprise that defines the option, in the form of a
   registered 32 bit Private Enterprise Number (PEN)
   [I-D.liang-iana-pen].  There is no default value for this field.
   Note that it is not used during discovery.  It MUST be verified
   during negotiation or synchronization.

   The 'loop-count' field is used for terminating negotiation as
   described in Section 3.7.5.  It is also used for terminating
   discovery as described in Section 3.3.3, and for terminating flooding
   as described in FLOODING.

   The 'any' field is to express the actual value of a negotiation or
   synchronization objective.  Its format is defined in the
   specification of the objective and may be a single value or a data
   structure of any kind.  It is optional because it is optional in a
   Discovery or Response message.




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3.9.2.  Objective flags

   An objective may be relevant for discovery, negotiation or
   synchronization.  This is expressed in the objective by logical
   flags:

     objective-flags = uint .bits objective-flag
     objective-flag = &(
     D: 0 ; valid for discovery only
     N: 1 ; valid for discovery and negotiation
     S: 2 ; valid for discovery and synchronization
     )

3.9.3.  General Considerations for Objective Options

   As mentioned above, generic Objective Options MUST be assigned a
   unique name.  As long as vendor-defined Objective Options start with
   a valid PEN, this document does not restrict their choice of name,
   but the vendor SHOULD publish the names in use.

   All Objective Options MUST respect the CBOR patterns defined above as
   "generic-obj" or "vendor-obj" and MUST replace the "any" field with a
   valid CBOR data definition for the relevant use case and application.

   An Objective Option that contains no additional fields beyond its
   "loop-count" can only be a discovery objective and MUST only be used
   in Discovery and Response messages.

   The Negotiation Objective Options contain negotiation objectives,
   which vary according to different functions/services.  They MUST be
   carried by Discovery, Request or Negotiation Messages only.  The
   negotiation initiator MUST set the initial "loop-count" to a value
   specified in the specification of the objective or, if no such value
   is specified, to GRASP_DEF_LOOPCT.

   For most scenarios, there should be initial values in the negotiation
   requests.  Consequently, the Negotiation Objective options MUST
   always be completely presented in a Request message, or in a
   Discovery message in rapid mode.  If there is no initial value, the
   bits in the value field SHOULD all be set to indicate a meaningless
   value, unless this is inappropriate for the specific negotiation
   objective.

   Synchronization Objective Options are similar, but MUST be carried by
   Discovery, Request or Response messages only.  They include value
   fields only in Response messages.





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3.9.4.  Organizing of Objective Options

   Generic objective options MUST be specified in documents available to
   the public and MUST be designed to use either the negotiation or the
   synchronization mechanism described above.

   As noted earlier, one negotiation objective is handled by each GRASP
   negotiation thread.  Therefore, a negotiation objective, which is
   based on a specific function or action, SHOULD be organized as a
   single GRASP option.  It is NOT RECOMMENDED to organize multiple
   negotiation objectives into a single option, nor to split a single
   function or action into multiple negotiation objectives.

   It is important to understand that GRASP negotiation does not support
   transactional integrity.  If transactional integrity is needed for a
   specific objective, this must be ensured by the ASA.  For example, an
   ASA might need to ensure that it only participates in one negotiation
   thread at the same time.  Such an ASA would need to stop listening
   for incoming negotiation requests before generating an outgoing
   negotiation request.

   A synchronization objective SHOULD be organized as a single GRASP
   option.

   Some objectives will support more than one operational mode.  An
   example is a negotiation objective with both a "dry run" mode (where
   the negotiation is to find out whether the other end can in fact make
   the requested change without problems) and a "live" mode.  Such modes
   will be defined in the specification of such an objective.  These
   objectives SHOULD include flags indicating the applicable mode(s).

   An objective may have multiple parameters.  Parameters can be
   categorized into two classes: the obligatory ones presented as fixed
   fields; and the optional ones presented in CBOR sub-options or some
   other form of data structure embedded in CBOR.  The format might be
   inherited from an existing management or configuration protocol, the
   objective option acting as a carrier for that format.  The data
   structure might be defined in a formal language, but that is a matter
   for the specifications of individual objectives.  There are many
   candidates, according to the context, such as ABNF, RBNF, XML Schema,
   possibly YANG, etc.  The GRASP protocol itself is agnostic on these
   questions.

   It is NOT RECOMMENDED to split parameters in a single objective into
   multiple options, unless they have different response periods.  An
   exception scenario may also be described by split objectives.





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   All objectives MUST support GRASP discovery.  However, as mentioned
   in Section 3.2, it is acceptable for an ASA to use an alternative
   method of discovery.

   Normally, a GRASP objective will refer to specific technical
   parameters as explained in Section 3.1.  However, it is acceptable to
   define an abstract objective for the purpose of managing or
   coordinating ASAs.  It is also acceptable to define a special-purpose
   objective for purposes such as trust bootstrapping or formation of
   the ACP.

3.9.5.  Experimental and Example Objective Options

   The names "EX0" through "EX9" have been reserved for experimental
   options.  Multiple names have been assigned because a single
   experiment may use multiple options simultaneously.  These
   experimental options are highly likely to have different meanings
   when used for different experiments.  Therefore, they SHOULD NOT be
   used without an explicit human decision and SHOULD NOT be used in
   unmanaged networks such as home networks.

   These names are also RECOMMENDED for use in documentation examples.

4.  Open Issues

   There are various unresolved design questions that are worthy of more
   work in the near future, as listed below (statically numbered in
   historical order for reference purposes, with the resolved issues
   retained for reference):

   o  1.  UDP vs TCP: For now, this specification suggests UDP and TCP
      as message transport mechanisms.  This is not clarified yet.  UDP
      is good for short conversations, is necessary for multicast
      discovery, and generally fits the discovery and divert scenarios
      well.  However, it will cause problems with large messages.  TCP
      is good for stable and long sessions, with a little bit of time
      consumption during the session establishment stage.  If messages
      exceed a reasonable MTU, a TCP mode will be required in any case.
      This question may be affected by the security discussion.

      RESOLVED by specifying UDP for short message and TCP for longer
      one.


   o  2.  DTLS or TLS vs built-in security mechanism.  For now, this
      specification has chosen a PKI based built-in security mechanism
      based on asymmetric cryptography.  However, (D)TLS might be chosen
      as security solution to avoid duplication of effort.  It also



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      allows essentially similar security for short messages over UDP
      and longer ones over TCP.  The implementation trade-offs are
      different.  The current approach requires expensive asymmetric
      cryptographic calculations for every message.  (D)TLS has startup
      overheads but cheaper crypto per message.  DTLS is less mature
      than TLS.

      RESOLVED by specifying external security (ACP or (D)TLS).



   o  The following open issues apply only if the current security model
      is retained:

      *  2.1.  For replay protection, GRASP currently requires every
         participant to have an NTP-synchronized clock.  Is this OK for
         low-end devices, and how does it work during device
         bootstrapping?  We could take the Timestamp out of signature
         option, to become an independent and OPTIONAL (or RECOMMENDED)
         option.

      *  2.2.  The Signature Option states that this option could be any
         place in a message.  Wouldn't it be better to specify a
         position (such as the end)?  That would be much simpler to
         implement.

      RESOLVED by changing security model.

   o  3.  DoS Attack Protection needs work.

      RESOLVED by adding text.


   o  4.  Should we consider preferring a text-based approach to
      discovery (after the initial discovery needed for bootstrapping)?
      This could be a complementary mechanism for multicast based
      discovery, especially for a very large autonomic network.
      Centralized registration could be automatically deployed
      incrementally.  At the very first stage, the repository could be
      empty; then it could be filled in by the objectives discovered by
      different devices (for example using Dynamic DNS Update).  The
      more records are stored in the repository, the less the multicast-
      based discovery is needed.  However, if we adopt such a mechanism,
      there would be challenges: stateful solution, and security.

      RESOLVED for now by adding optional use of DNS-SD by ASAs.





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   o  5.  Need to expand description of the minimum requirements for the
      specification of an individual discovery, synchronization or
      negotiation objective.

      RESOLVED for now by extra wording.

   o  6.  Use case and protocol walkthrough.  A description of how a
      node starts up, performs discovery, and conducts negotiation and
      synchronisation for a sample use case would help readers to
      understand the applicability of this specification.  Maybe it
      should be an artificial use case or maybe a simple real one, based
      on a conceptual API.  However, the authors have not yet decided
      whether to have a separate document or have it in the protocol
      document.

      RESOLVED: recommend a separate document.

   o  7.  Cross-check against other ANIMA WG documents for consistency
      and gaps.

   o  8.  Consideration of ADNCP proposal.

      RESOLVED by adding optional use of DNCP for flooding-type
      synchronization.


   o  9.  Clarify how a GDNP instance knows whether it is running inside
      the ACP.  (Sheng)

      RESOLVED by improved text.


   o  10.  Clarify how a non-ACP GDNP instance initiates (D)TLS.
      (Sheng)

      RESOLVED by improved text and declaring DTLS out of scope for this
      draft.


   o  11.  Clarify how UDP/TCP choice is made.  (Sheng) [Like DNS? -
      Brian]

      RESOLVED by improved text.


   o  12.  Justify that IP address within ACP or (D)TLS environment is
      sufficient to prove AN identity; or explain how Device Identity
      Option is used.  (Sheng)



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      RESOLVED for now: we assume that all ASAs in a device are trusted
      as soon as the device is trusted, so they share credentials.  In
      that case the Device Identity Option is useless.  This needs to be
      reviewed later.


   o  13.  Emphasise that negotiation/synchronization are independent
      from discovery, although the rapid discovery mode includes the
      first step of a negotiation/synchronization.  (Sheng)

      RESOLVED by improved text.


   o  14.  Do we need an unsolicited flooding mechanism for discovery
      (for discovery results that everyone needs), to reduce scaling
      impact of flooding discovery messages?  (Toerless)

      RESOLVED: Yes, added to requirements and solution.


   o  15.  Do we need flag bits in Objective Options to distinguish
      distinguish Synchronization and Negotiation "Request" or rapid
      mode "Discovery" messages?  (Bing)

      RESOLVED: yes, work on the API showed that these flags are
      essential.

   o  16.  (Related to issue 14).  Should we revive the "unsolicited
      Response" for flooding synchronisation data?  This has to be done
      carefully due to the well-known issues with flooding, but it could
      be useful, e.g. for Intent distribution, where DNCP doesn't seem
      applicable.

      RESOLVED: Yes, see #14.

   o  17.  Ensure that the discovery mechanism is completely proof
      against loops and protected against duplicate responses.

      RESOLVED: Added loop count mechanism.

   o  18.  Discuss the handling of multiple valid discovery responses.

   o  19.  Should we use a text-oriented format such as JSON/CBOR
      instead of native binary TLV format?

      RESOLVED: Yes, changed to CBOR





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   o  20.  Is the Divert option needed?  If a discovery response
      provides a valid IP address or FQDN, the recipient doesn't gain
      any extra knowledge from the Divert.  On the other hand, the
      presence of Divert informs the receiver that the target is off-
      link, which might be useful sometimes.

   o  21.  Rename the protocol as GRASP (GeneRic Autonomic Signaling
      Protocol)?

      RESOLVED: Yes, name changed.

   o  22.  Does discovery mechanism scale robustly as needed?  Need hop
      limit on relaying?

      RESOLVED: Added hop limit.

   o  23.  Need more details on TTL for caching discovery responses.

      RESOLVED: Done.

   o  24.  Do we need "fast withdrawal" of discovery responses?

   o  25.  Does GDNP discovery meet the needs of multi-hop DNS-SD?

   o  26.  Add a URL type to the locator options (for security
      bootstrap)

      RESOLVED: Done.

   o  27.  Security of unsolicited Response multicasts (Section 3.3.5).

   o  28.  Does ACP support multicast?

   o  29.  PEN is used to distinguish vendor options.  Would it be
      better to use a domain name?  Anything unique will do.

   o  30.  Does response to discovery require randomized delays to
      mitigate amplification attacks?

   o  31.  We have specified repeats for failed discovery etc.  Is that
      sufficient to deal with sleeping nodes?

   o  32.  We have one-to-one synchronization and flooding
      synchronization.  Do we also need selective flooding to a subset
      of nodes?






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5.  Security Considerations

   It is obvious that a successful attack on negotiation-enabled nodes
   would be extremely harmful, as such nodes might end up with a
   completely undesirable configuration that would also adversely affect
   their peers.  GRASP nodes and messages therefore require full
   protection.

   - Authentication

      A cryptographically authenticated identity for each device is
      needed in an autonomic network.  It is not safe to assume that a
      large network is physically secured against interference or that
      all personnel are trustworthy.  Each autonomic node MUST be
      capable of proving its identity and authenticating its messages.
      GRASP relies on a separate external certificate-based security
      mechanism to support authentication, data integrity protection,
      and anti-replay protection.

      Since GRASP is intended to be deployed in a single administrative
      domain operating its own trust anchor and CA, there is no need for
      a trusted public third party.  In a network requiring "air gap"
      security, such a dependency would be unacceptable.

      If GRASP is used temporarily without an external security
      mechanism, for example during system bootstrap (Section 3.3.1),
      the Session ID (Section 3.6) will act as a nonce to provide
      limited protection against third parties injecting responses.  A
      full analysis of the secure bootstrap process is out of scope for
      the present document.

   - Privacy and confidentiality

      Generally speaking, no personal information is expected to be
      involved in the signaling protocol, so there should be no direct
      impact on personal privacy.  Nevertheless, traffic flow paths,
      VPNs, etc. could be negotiated, which could be of interest for
      traffic analysis.  Also, operators generally want to conceal
      details of their network topology and traffic density from
      outsiders.  Therefore, since insider attacks cannot be excluded in
      a large network, the security mechanism for the protocol MUST
      provide message confidentiality.

   - DoS Attack Protection

      GRASP discovery partly relies on insecure link-local multicast.
      Since routers participating in GRASP sometimes relay discovery
      messages from one link to another, this could be a vector for



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      denial of service attacks.  Relevant mitigations are specified in
      Section 3.3.3.  Additionally, it is of great importance that
      firewalls prevent any GRASP messages from entering the domain from
      an untrusted source.

   - Security during bootstrap and discovery

      A node cannot authenticate GRASP traffic from other nodes until it
      has identified the trust anchor and can validate certificates for
      other nodes.  Also, until it has succesfully enrolled
      [I-D.ietf-anima-bootstrapping-keyinfra] it cannot assume that
      other nodes are able to authenticate its own traffic.  Therefore,
      GRASP discovery during the bootstrap phase for a new device will
      inevitably be insecure and GRASP synchronization and negotiation
      will be impossible until enrollment is complete.

6.  CDDL Specification of GRASP

   <CODE BEGINS>

   grasp-message = message

   session-id = 0..16777215
   ; that is up to 24 bits

   message /= discovery-message
   discovery-message = [M_DISCOVERY, session-id, objective]

   message /= response-message
   response-message = [M_RESPONSE, session-id,
                      (+locator-option // divert-option // objective)]

   message /= request-message
   request-message = [M_REQUEST, session-id, objective]

   message /= negotiation-message
   negotiation-message = [M_NEGOTIATE, session-id, objective]

   message /= end-message
   end-message = [M_END, session-id, (accept-option / decline-option)]

   message /= wait-message
   wait-message = [M_WAIT, session-id, waiting-time-option]

   divert-option = [O_DIVERT, +locator-option]

   accept-option = [O_ACCEPT]




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   decline-option = [O_DECLINE]

   waiting-time-option = [O_WAITING, option-waiting-time]
   option-waiting-time = 0..4294967295 ; in milliseconds

   option-device-id = [O_DEVICE_ID, bytes]

   locator-option /= ipv4-locator-option
   ipv4-locator-option = bytes .size 4
   ; this is simpler than [O_IPv4_LOCATOR, bytes .size 4]

   locator-option /= ipv6-locator-option
   ipv6-locator-option = bytes .size 16

   locator-option /= fqdn-locator-option
   fqdn-locator-option = [O_FQDN_LOCATOR, text]

   locator-option /= url-locator-option
   url-locator-option = [O_URL_LOCATOR, text]

   objective-flags = uint .bits objective-flag

   objective-flag = &(
   D: 0
   N: 1
   S: 2
   )

   ; D means valid for discovery only
   ; N means valid for discovery and negotiation
   ; S means valid for discovery and synchronization

   objective /= generic-obj
   generic-obj = [objective-name, objective-flags, loop-count, ?any]

   objective /= vendor-obj
   vendor-obj = [{"PEN":pen}, objective-name, objective-flags,
                 loop-count, ?any]

   ; A PEN is used to distinguish vendor-specific options.

   pen = 0..4294967295
   objective-name = tstr
   loop-count = 0..255

   ; Constants

   M_DISCOVERY = 1



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   M_RESPONSE = 2
   M_REQUEST = 3
   M_NEGOTIATE = 4
   M_END = 5
   M_WAIT = 6

   O_DIVERT = 100
   O_ACCEPT = 101
   O_DECLINE = 102
   O_WAITING = 103
   O_DEVICE_ID = 104
   O_FQDN_LOCATOR = 105
   O_URL_LOCATOR = 106


   <CODE ENDS>

7.  IANA Considerations

   Section 3.5 defines the following link-local multicast addresses,
   which have been assigned by IANA for use by GRASP:

   ALL_GRASP_NEIGHBOR multicast address  (IPv6): (TBD1).  Assigned in
      the IPv6 Link-Local Scope Multicast Addresses registry.

   ALL_GRASP_NEIGHBOR multicast address  (IPv4): (TBD2).  Assigned in
      the IPv4 Multicast Local Network Control Block.

      (Note in draft: alternatively, we could use 224.0.0.1, currently
      defined as All Systems on this Subnet.)

   Section 3.5 defines the following UDP and TCP port, which has been
   assigned by IANA for use by GRASP:

   GRASP_LISTEN_PORT:  (TBD3)

   This document defines the General Discovery and Negotiation Protocol
   (GRASP).  The IANA is requested to create a GRASP Parameter Registry.
   The IANA is also requested to add two new registry tables to the
   newly-created GRASP Parameter Registry.  The two tables are the GRASP
   Messages and Options Table and the GRASP Objective Names Table.

   GRASP Messages and Options Table.  The values in this table are names
   paired with decimal integers.  Future values MUST be assigned using
   the Standards Action policy defined by [RFC5226].  The following
   initial values are assigned by this document:





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    M_DISCOVERY = 1
    M_RESPONSE = 2
    M_REQUEST = 3
    M_NEGOTIATE = 4
    M_END = 5
    M_WAIT = 6

    O_DIVERT = 100
    O_ACCEPT = 101
    O_DECLINE = 102
    O_WAITING = 103
    O_DEVICE_ID = 104
    O_FQDN_LOCATOR = 105
    O_URL_LOCATOR = 106

   GRASP Objective Names Table.  The values in this table are UTF-8
   strings.  Future values MUST be assigned using the Specification
   Required policy defined by [RFC5226].  The following initial values
   are assigned by this document:

    EX0
    EX1
    EX2
    EX3
    EX4
    EX5
    EX6
    EX7
    EX8
    EX9
    PEN

8.  Acknowledgements

   A major contribution to the original version of this document was
   made by Sheng Jiang.

   Valuable comments were received from Michael Behringer, Jeferson
   Campos Nobre, Laurent Ciavaglia, Zongpeng Du, Yu Fu, Zhenbin Li,
   Dimitri Papadimitriou, Pierre Peloso, Reshad Rahman, Michael
   Richardson, Markus Stenberg, Rene Struik, Dacheng Zhang, and other
   participants in the NMRG research group and the ANIMA working group.

   This document was produced using the xml2rfc tool [RFC2629].







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9.  Change log [RFC Editor: Please remove]

   draft-ietf-anima-grasp-01, 2015-10-09:

   Updated requirements after list discussion.

   Changed from TLV to CBOR format - many detailed changes, added co-
   author.

   Tightened up loop count and timeouts for various cases.

   Noted that GRASP does not provide transactional integrity.

   Various other clarifications and editorial fixes.

   draft-ietf-anima-grasp-00, 2015-08-14:

   File name and protocol name changed following WG adoption.

   Added URL locator type.

   draft-carpenter-anima-gdn-protocol-04, 2015-06-21:

   Tuned wording around hierarchical structure.

   Changed "device" to "ASA" in many places.

   Reformulated requirements to be clear that the ASA is the main
   customer for signaling.

   Added requirement for flooding unsolicited synch, and added it to
   protocol spec.  Recognized DNCP as alternative for flooding synch
   data.

   Requirements clarified, expanded and rearranged following design team
   discussion.

   Clarified that GDNP discovery must not be a prerequisite for GDNP
   negotiation or synchronization (resolved issue 13).

   Specified flag bits for objective options (resolved issue 15).

   Clarified usage of ACP vs TLS/DTLS and TCP vs UDP (resolved issues
   9,10,11).

   Updated DNCP description from latest DNCP draft.

   Editorial improvements.



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   draft-carpenter-anima-gdn-protocol-03, 2015-04-20:

   Removed intrinsic security, required external security

   Format changes to allow DNCP co-existence

   Recognized DNS-SD as alternative discovery method.

   Editorial improvements

   draft-carpenter-anima-gdn-protocol-02, 2015-02-19:

   Tuned requirements to clarify scope,

   Clarified relationship between types of objective,

   Clarified that objectives may be simple values or complex data
   structures,

   Improved description of objective options,

   Added loop-avoidance mechanisms (loop count and default timeout,
   limitations on discovery relaying and on unsolicited responses),

   Allow multiple discovery objectives in one response,

   Provided for missing or multiple discovery responses,

   Indicated how modes such as "dry run" should be supported,

   Minor editorial and technical corrections and clarifications,

   Reorganized future work list.

   draft-carpenter-anima-gdn-protocol-01, restructured the logical flow
   of the document, updated to describe synchronization completely, add
   unsolicited responses, numerous corrections and clarifications,
   expanded future work list, 2015-01-06.

   draft-carpenter-anima-gdn-protocol-00, combination of draft-jiang-
   config-negotiation-ps-03 and draft-jiang-config-negotiation-protocol-
   02, 2014-10-08.

10.  References







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10.1.  Normative References

   [I-D.greevenbosch-appsawg-cbor-cddl]
              Vigano, C. and H. Birkholz, "CBOR data definition
              language: a notational convention to express CBOR data
              structures.", draft-greevenbosch-appsawg-cbor-cddl-06
              (work in progress), July 2015.

   [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>.

   [RFC3986]  Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
              Resource Identifier (URI): Generic Syntax", STD 66,
              RFC 3986, DOI 10.17487/RFC3986, January 2005,
              <http://www.rfc-editor.org/info/rfc3986>.

   [RFC4086]  Eastlake 3rd, D., Schiller, J., and S. Crocker,
              "Randomness Requirements for Security", BCP 106, RFC 4086,
              DOI 10.17487/RFC4086, June 2005,
              <http://www.rfc-editor.org/info/rfc4086>.

   [RFC5246]  Dierks, T. and E. Rescorla, "The Transport Layer Security
              (TLS) Protocol Version 1.2", RFC 5246,
              DOI 10.17487/RFC5246, August 2008,
              <http://www.rfc-editor.org/info/rfc5246>.

   [RFC5280]  Cooper, D., Santesson, S., Farrell, S., Boeyen, S.,
              Housley, R., and W. Polk, "Internet X.509 Public Key
              Infrastructure Certificate and Certificate Revocation List
              (CRL) Profile", RFC 5280, DOI 10.17487/RFC5280, May 2008,
              <http://www.rfc-editor.org/info/rfc5280>.

   [RFC6347]  Rescorla, E. and N. Modadugu, "Datagram Transport Layer
              Security Version 1.2", RFC 6347, DOI 10.17487/RFC6347,
              January 2012, <http://www.rfc-editor.org/info/rfc6347>.

   [RFC7049]  Bormann, C. and P. Hoffman, "Concise Binary Object
              Representation (CBOR)", RFC 7049, DOI 10.17487/RFC7049,
              October 2013, <http://www.rfc-editor.org/info/rfc7049>.

10.2.  Informative References








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   [I-D.behringer-anima-reference-model]
              Behringer, M., Carpenter, B., Eckert, T., Ciavaglia, L.,
              Liu, B., Jeff, J., and J. Strassner, "A Reference Model
              for Autonomic Networking", draft-behringer-anima-
              reference-model-03 (work in progress), June 2015.

   [I-D.chaparadza-intarea-igcp]
              Behringer, M., Chaparadza, R., Petre, R., Li, X., and H.
              Mahkonen, "IP based Generic Control Protocol (IGCP)",
              draft-chaparadza-intarea-igcp-00 (work in progress), July
              2011.

   [I-D.eckert-anima-stable-connectivity]
              Eckert, T. and M. Behringer, "Using Autonomic Control
              Plane for Stable Connectivity of Network OAM", draft-
              eckert-anima-stable-connectivity-01 (work in progress),
              March 2015.

   [I-D.ietf-anima-autonomic-control-plane]
              Behringer, M., Bjarnason, S., BL, B., and T. Eckert, "An
              Autonomic Control Plane", draft-ietf-anima-autonomic-
              control-plane-01 (work in progress), October 2015.

   [I-D.ietf-anima-bootstrapping-keyinfra]
              Pritikin, M., Richardson, M., Behringer, M., and S.
              Bjarnason, "Bootstrapping Key Infrastructures", draft-
              ietf-anima-bootstrapping-keyinfra-00 (work in progress),
              August 2015.

   [I-D.ietf-homenet-dncp]
              Stenberg, M. and S. Barth, "Distributed Node Consensus
              Protocol", draft-ietf-homenet-dncp-10 (work in progress),
              September 2015.

   [I-D.ietf-homenet-hncp]
              Stenberg, M., Barth, S., and P. Pfister, "Home Networking
              Control Protocol", draft-ietf-homenet-hncp-09 (work in
              progress), August 2015.

   [I-D.ietf-netconf-restconf]
              Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF
              Protocol", draft-ietf-netconf-restconf-07 (work in
              progress), July 2015.








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   [I-D.liang-iana-pen]
              Liang, P., Melnikov, A., and D. Conrad, "Private
              Enterprise Number (PEN) practices and Internet Assigned
              Numbers Authority (IANA) registration considerations",
              draft-liang-iana-pen-06 (work in progress), July 2015.

   [I-D.stenberg-anima-adncp]
              Stenberg, M., "Autonomic Distributed Node Consensus
              Protocol", draft-stenberg-anima-adncp-00 (work in
              progress), March 2015.

   [RFC2205]  Braden, R., Ed., Zhang, L., Berson, S., Herzog, S., and S.
              Jamin, "Resource ReSerVation Protocol (RSVP) -- Version 1
              Functional Specification", RFC 2205, DOI 10.17487/RFC2205,
              September 1997, <http://www.rfc-editor.org/info/rfc2205>.

   [RFC2608]  Guttman, E., Perkins, C., Veizades, J., and M. Day,
              "Service Location Protocol, Version 2", RFC 2608,
              DOI 10.17487/RFC2608, June 1999,
              <http://www.rfc-editor.org/info/rfc2608>.

   [RFC2629]  Rose, M., "Writing I-Ds and RFCs using XML", RFC 2629,
              DOI 10.17487/RFC2629, June 1999,
              <http://www.rfc-editor.org/info/rfc2629>.

   [RFC2865]  Rigney, C., Willens, S., Rubens, A., and W. Simpson,
              "Remote Authentication Dial In User Service (RADIUS)",
              RFC 2865, DOI 10.17487/RFC2865, June 2000,
              <http://www.rfc-editor.org/info/rfc2865>.

   [RFC3209]  Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V.,
              and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP
              Tunnels", RFC 3209, DOI 10.17487/RFC3209, December 2001,
              <http://www.rfc-editor.org/info/rfc3209>.

   [RFC3315]  Droms, R., Ed., Bound, J., Volz, B., Lemon, T., Perkins,
              C., and M. Carney, "Dynamic Host Configuration Protocol
              for IPv6 (DHCPv6)", RFC 3315, DOI 10.17487/RFC3315, July
              2003, <http://www.rfc-editor.org/info/rfc3315>.

   [RFC3416]  Presuhn, R., Ed., "Version 2 of the Protocol Operations
              for the Simple Network Management Protocol (SNMP)",
              STD 62, RFC 3416, DOI 10.17487/RFC3416, December 2002,
              <http://www.rfc-editor.org/info/rfc3416>.







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   [RFC4861]  Narten, T., Nordmark, E., Simpson, W., and H. Soliman,
              "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861,
              DOI 10.17487/RFC4861, September 2007,
              <http://www.rfc-editor.org/info/rfc4861>.

   [RFC5226]  Narten, T. and H. Alvestrand, "Guidelines for Writing an
              IANA Considerations Section in RFCs", BCP 26, RFC 5226,
              DOI 10.17487/RFC5226, May 2008,
              <http://www.rfc-editor.org/info/rfc5226>.

   [RFC5971]  Schulzrinne, H. and R. Hancock, "GIST: General Internet
              Signalling Transport", RFC 5971, DOI 10.17487/RFC5971,
              October 2010, <http://www.rfc-editor.org/info/rfc5971>.

   [RFC6206]  Levis, P., Clausen, T., Hui, J., Gnawali, O., and J. Ko,
              "The Trickle Algorithm", RFC 6206, DOI 10.17487/RFC6206,
              March 2011, <http://www.rfc-editor.org/info/rfc6206>.

   [RFC6241]  Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed.,
              and A. Bierman, Ed., "Network Configuration Protocol
              (NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011,
              <http://www.rfc-editor.org/info/rfc6241>.

   [RFC6733]  Fajardo, V., Ed., Arkko, J., Loughney, J., and G. Zorn,
              Ed., "Diameter Base Protocol", RFC 6733,
              DOI 10.17487/RFC6733, October 2012,
              <http://www.rfc-editor.org/info/rfc6733>.

   [RFC6762]  Cheshire, S. and M. Krochmal, "Multicast DNS", RFC 6762,
              DOI 10.17487/RFC6762, February 2013,
              <http://www.rfc-editor.org/info/rfc6762>.

   [RFC6763]  Cheshire, S. and M. Krochmal, "DNS-Based Service
              Discovery", RFC 6763, DOI 10.17487/RFC6763, February 2013,
              <http://www.rfc-editor.org/info/rfc6763>.

   [RFC6887]  Wing, D., Ed., Cheshire, S., Boucadair, M., Penno, R., and
              P. Selkirk, "Port Control Protocol (PCP)", RFC 6887,
              DOI 10.17487/RFC6887, April 2013,
              <http://www.rfc-editor.org/info/rfc6887>.

   [RFC7228]  Bormann, C., Ersue, M., and A. Keranen, "Terminology for
              Constrained-Node Networks", RFC 7228,
              DOI 10.17487/RFC7228, May 2014,
              <http://www.rfc-editor.org/info/rfc7228>.






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   [RFC7558]  Lynn, K., Cheshire, S., Blanchet, M., and D. Migault,
              "Requirements for Scalable DNS-Based Service Discovery
              (DNS-SD) / Multicast DNS (mDNS) Extensions", RFC 7558,
              DOI 10.17487/RFC7558, July 2015,
              <http://www.rfc-editor.org/info/rfc7558>.

   [RFC7575]  Behringer, M., Pritikin, M., Bjarnason, S., Clemm, A.,
              Carpenter, B., Jiang, S., and L. Ciavaglia, "Autonomic
              Networking: Definitions and Design Goals", RFC 7575,
              DOI 10.17487/RFC7575, June 2015,
              <http://www.rfc-editor.org/info/rfc7575>.

   [RFC7576]  Jiang, S., Carpenter, B., and M. Behringer, "General Gap
              Analysis for Autonomic Networking", RFC 7576,
              DOI 10.17487/RFC7576, June 2015,
              <http://www.rfc-editor.org/info/rfc7576>.

Appendix A.  Capability Analysis of Current Protocols

   This appendix discusses various existing protocols with properties
   related to the above negotiation and synchronisation requirements.
   The purpose is to evaluate whether any existing protocol, or a simple
   combination of existing protocols, can meet those requirements.

   Numerous protocols include some form of discovery, but these all
   appear to be very specific in their applicability.  Service Location
   Protocol (SLP) [RFC2608] provides service discovery for managed
   networks, but requires configuration of its own servers.  DNS-SD
   [RFC6763] combined with mDNS [RFC6762] provides service discovery for
   small networks with a single link layer.  [RFC7558] aims to extend
   this to larger autonomous networks but this is not yet standardized.
   However, both SLP and DNS-SD appear to target primarily application
   layer services, not the layer 2 and 3 objectives relevant to basic
   network configuration.  Both SLP and DNS-SD are text-based protocols.

   Routing protocols are mainly one-way information announcements.  The
   receiver makes independent decisions based on the received
   information and there is no direct feedback information to the
   announcing peer.  This remains true even though the protocol is used
   in both directions between peer routers; there is state
   synchronization, but no negotiation, and each peer runs its route
   calculations independently.

   Simple Network Management Protocol (SNMP) [RFC3416] uses a command/
   response model not well suited for peer negotiation.  Network
   Configuration Protocol (NETCONF) [RFC6241] uses an RPC model that
   does allow positive or negative responses from the target system, but
   this is still not adequate for negotiation.



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   There are various existing protocols that have elementary negotiation
   abilities, such as Dynamic Host Configuration Protocol for IPv6
   (DHCPv6) [RFC3315], Neighbor Discovery (ND) [RFC4861], Port Control
   Protocol (PCP) [RFC6887], Remote Authentication Dial In User Service
   (RADIUS) [RFC2865], Diameter [RFC6733], etc.  Most of them are
   configuration or management protocols.  However, they either provide
   only a simple request/response model in a master/slave context or
   very limited negotiation abilities.

   There are some signaling protocols with an element of negotiation.
   For example Resource ReSerVation Protocol (RSVP) [RFC2205] was
   designed for negotiating quality of service parameters along the path
   of a unicast or multicast flow.  RSVP is a very specialised protocol
   aimed at end-to-end flows.  However, it has some flexibility, having
   been extended for MPLS label distribution [RFC3209].  A more generic
   design is General Internet Signalling Transport (GIST) [RFC5971], but
   it is complex, tries to solve many problems, and is also aimed at
   per-flow signaling across many hops rather than at device-to-device
   signaling.  However, we cannot completely exclude extended RSVP or
   GIST as a synchronization and negotiation protocol.  They do not
   appear to be directly useable for peer discovery.

   We now consider two protocols that are works in progress at the time
   of this writing.  Firstly, RESTCONF [I-D.ietf-netconf-restconf] is a
   protocol intended to convey NETCONF information expressed in the YANG
   language via HTTP, including the ability to transit HTML
   intermediaries.  While this is a powerful approach in the context of
   centralised configuration of a complex network, it is not well
   adapted to efficient interactive negotiation between peer devices,
   especially simple ones that are unlikely to include YANG processing
   already.

   Secondly, we consider Distributed Node Consensus Protocol (DNCP)
   [I-D.ietf-homenet-dncp].  This is defined as a generic form of state
   synchronization protocol, with a proposed usage profile being the
   Home Networking Control Protocol (HNCP) [I-D.ietf-homenet-hncp] for
   configuring Homenet routers.  A specific application of DNCP for
   autonomic networking was proposed in [I-D.stenberg-anima-adncp].

   DNCP "is designed to provide a way for each participating node to
   publish a set of TLV (Type-Length-Value) tuples, and to provide a
   shared and common view about the data published... DNCP is most
   suitable for data that changes only infrequently... If constant rapid
   state changes are needed, the preferable choice is to use an
   additional point-to-point channel..."

   Specific features of DNCP include:




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   o  Every participating node has a unique node identifier.

   o  DNCP messages are encoded as a sequence of TLV objects, sent over
      unicast UDP or TCP, with or without (D)TLS security.

   o  Multicast is used only for discovery of DNCP neighbors when lower
      security is acceptable.

   o  Synchronization of state is maintained by a flooding process using
      the Trickle algorithm.  There is no bilateral synchronization or
      negotiation capability.

   o  The HNCP profile of DNCP is designed to operate between directly
      connected neighbors on a shared link using UDP and link-local IPv6
      addresses.

   DNCP does not meet the needs of a general negotiation protocol,
   because it is designed specifically for flooding synchronization.
   Also, in its HNCP profile it is limited to link-local messages and to
   IPv6.  However, at the minimum it is a very interesting test case for
   this style of interaction between devices without needing a central
   authority, and it is a proven method of network-wide state
   synchronization by flooding.

   A proposal was made some years ago for an IP based Generic Control
   Protocol (IGCP) [I-D.chaparadza-intarea-igcp].  This was aimed at
   information exchange and negotiation but not directly at peer
   discovery.  However, it has many points in common with the present
   work.

   None of the above solutions appears to completely meet the needs of
   generic discovery, state synchronization and negotiation in a single
   solution.  Many of the protocols assume that they are working in a
   traditional top-down or north-south scenario, rather than a fluid
   peer-to-peer scenario.  Most of them are specialized in one way or
   another.  As a result, we have not identified a combination of
   existing protocols that meets the requirements in Section 2.  Also,
   we have not identified a path by which one of the existing protocols
   could be extended to meet the requirements.

Authors' Addresses










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   Carsten Bormann
   Universitaet Bremen TZI
   Postfach 330440
   D-28359 Bremen
   Germany

   Email: cabo@tzi.org


   Brian Carpenter (editor)
   Department of Computer Science
   University of Auckland
   PB 92019
   Auckland  1142
   New Zealand

   Email: brian.e.carpenter@gmail.com


   Bing Liu (editor)
   Huawei Technologies Co., Ltd
   Q14, Huawei Campus
   No.156 Beiqing Road
   Hai-Dian District, Beijing  100095
   P.R. China

   Email: leo.liubing@huawei.com
























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