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Versions: (draft-liu-anima-grasp-api) 00 01 02 03 04 05 06 07 08 09 10

Network Working Group                                    B. E. Carpenter
Internet-Draft                                         Univ. of Auckland
Intended status: Informational                               B. Liu, Ed.
Expires: 16 April 2021                               Huawei Technologies
                                                                 W. Wang
                                                                 X. Gong
                                                         BUPT University
                                                         13 October 2020


   Generic Autonomic Signaling Protocol Application Program Interface
                              (GRASP API)
                     draft-ietf-anima-grasp-api-07

Abstract

   This document is a conceptual outline of an application programming
   interface (API) for the Generic Autonomic Signaling Protocol (GRASP).
   Such an API is needed for Autonomic Service Agents (ASA) calling the
   GRASP protocol module to exchange autonomic network messages with
   other ASAs.  Since GRASP is designed to support asynchronous
   operations, the API will need to be adapted to the support for
   asynchronicity in various programming languages and operating
   systems.

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 https://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 16 April 2021.

Copyright Notice

   Copyright (c) 2020 IETF Trust and the persons identified as the
   document authors.  All rights reserved.





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   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents (https://trustee.ietf.org/
   license-info) in effect on the date of publication of this document.
   Please review these documents carefully, as they describe your rights
   and restrictions with respect to this document.  Code Components
   extracted from this document must include Simplified BSD License text
   as described in Section 4.e of the Trust Legal Provisions and are
   provided without warranty as described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  GRASP API for ASA . . . . . . . . . . . . . . . . . . . . . .   4
     2.1.  Design Assumptions  . . . . . . . . . . . . . . . . . . .   4
     2.2.  Asynchronous Operations . . . . . . . . . . . . . . . . .   5
       2.2.1.  Alternative Asynchronous Mechanisms . . . . . . . . .   6
       2.2.2.  Multiple Negotiation Scenario . . . . . . . . . . . .   7
       2.2.3.  Overlapping Sessions and Operations . . . . . . . . .   8
     2.3.  API definition  . . . . . . . . . . . . . . . . . . . . .   8
       2.3.1.  Parameters and data structures  . . . . . . . . . . .   8
       2.3.2.  Registration  . . . . . . . . . . . . . . . . . . . .  12
       2.3.3.  Discovery . . . . . . . . . . . . . . . . . . . . . .  15
       2.3.4.  Negotiation . . . . . . . . . . . . . . . . . . . . .  16
       2.3.5.  Synchronization and Flooding  . . . . . . . . . . . .  21
       2.3.6.  Invalid Message Function  . . . . . . . . . . . . . .  25
   3.  Implementation Status [RFC Editor: please remove] . . . . . .  26
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .  26
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  26
   6.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  26
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  26
     7.1.  Normative References  . . . . . . . . . . . . . . . . . .  26
     7.2.  Informative References  . . . . . . . . . . . . . . . . .  26
   Appendix A.  Error Codes  . . . . . . . . . . . . . . . . . . . .  28
   Appendix B.  Change log [RFC Editor: Please remove] . . . . . . .  29
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  31

1.  Introduction

   As defined in [I-D.ietf-anima-reference-model], the Autonomic Service
   Agent (ASA) is the atomic entity of an autonomic function, and it is
   instantiated on autonomic nodes.  When ASAs communicate with each
   other, they should use the Generic Autonomic Signaling Protocol
   (GRASP) [I-D.ietf-anima-grasp].

   As Figure 1 shows, a GRASP implementation could contain several sub-
   layers.  The bottom layer is the GRASP base protocol module, which is
   only responsible for sending and receiving GRASP messages and
   maintaining shared data structures.  Above that is the basic API



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   described in this document.  The upper layer contains some extended
   API functions based upon GRASP basic protocol.  For example,
   [I-D.ietf-anima-grasp-distribution] describes a possible extended
   function.

   Multiple ASAs in a single node will share the same instance of GRASP,
   much as multiple applications share a single TCP/IP stack.  This
   aspect is hidden from individual ASAs by the API, and is not further
   discussed here.

   It is desirable that ASAs can be designed as portable user-space
   programs using a system-independent API.  In many implementations,
   the GRASP code will therefore be split between user space and kernel
   space.  In user space, library functions provide the API and
   communicate directly with ASAs.  In kernel space is a daemon, or a
   set of sub-services, providing GRASP core functions that are
   independent of specific ASAs, such as multicast handling and
   relaying, and common data structures such as the discovery cache.
   The GRASP API library would need to communicate with the GRASP core
   via an inter-process communication (IPC) mechanism.  The details of
   this are system-dependent.

                +--------------+          +--------------+
                |     ASAs     |          |     ASAs     |
                +--------------+          +--------------+
                  |          |                    |
                  | +------------------+          |
                  | | GRASP Extended   |          |
                  | | Function API     |          |
                  | +------------------+          |
                  |          |                    |
               +------------------------------------------+
               |            GRASP API Library             |
               +------------------------------------------+
                                   |
                                  IPC
                                   |
               +------------------------------------------+
               |  GRASP Core                              |
               |  (functions, data structures, daemon(s)) |
               +------------------------------------------+

                         Figure 1: Software layout








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   Both the GRASP library and the extended function modules should be
   available to the ASAs.  However, since the extended functions are
   expected to be added in an incremental manner, they will be the
   subject of future documents.  This document only describes the basic
   GRASP API.

   The functions provided by the API do not map one-to-one onto GRASP
   messages.  Rather, they are intended to offer convenient support for
   message sequences (such as a discovery request followed by responses
   from several peers, or a negotiation request followed by various
   possible responses).  This choice was made to assist ASA programmers
   in writing code based on their application requirements rather than
   needing to understand protocol details.

   Note that a simple autonomic node might contain very few ASAs in
   addition to the autonomic infrastructure components described in
   [I-D.ietf-anima-bootstrapping-keyinfra] and
   [I-D.ietf-anima-autonomic-control-plane].  Such a node might directly
   integrate a GRASP protocol stack in its code and therefore not
   require this API to be installed.  However, the programmer would then
   need a deeper understanding of the GRASP protocol than is needed to
   use the API.

   This document gives a conceptual outline of the API.  It is not a
   formal specification for any particular programming language or
   operating system, and it is expected that details will be clarified
   in individual implementations.

2.  GRASP API for ASA

2.1.  Design Assumptions

   The assumption of this document is that any Autonomic Service Agent
   (ASA) needs to call a GRASP module.  The latter handles protocol
   details (security, sending and listening for GRASP messages, waiting,
   caching discovery results, negotiation looping, sending and receiving
   sychronization data, etc.) but understands nothing about individual
   GRASP objectives (Section 2.10 of [I-D.ietf-anima-grasp]).  The
   semantics of objectives are unknown to the GRASP module and are
   handled only by the ASAs.  Thus, this is an abstract API for use by
   ASAs.  Individual language bindings should be defined in separate
   documents.

   Different ASAs may make different use of GRASP features:

   *  Use GRASP only for discovery purposes.

   *  Use GRASP negotiation but only as an initiator (client).



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   *  Use GRASP negotiation but only as a responder.

   *  Use GRASP negotiation as an initiator or responder.

   *  Use GRASP synchronization but only as an initiator (recipient).

   *  Use GRASP synchronization but only as a responder and/or flooder.

   *  Use GRASP synchronization as an initiator, responder and/or
      flooder.

   The API also assumes that one ASA may support multiple objectives.
   Nothing prevents an ASA from supporting some objectives for
   synchronization and others for negotiation.

   The API design assumes that the operating system and programming
   language provide a mechanism for simultaneous asynchronous
   operations.  This is discussed in detail in Section 2.2.

   A few items are out of scope in this version, since practical
   experience is required before including them:

   *  Authorization of ASAs is not defined as part of GRASP and is not
      supported.

   *  User-supplied explicit locators for an objective are not
      supported.  The GRASP core will supply the locator, using the ACP
      address of the node concerned.

   *  The Rapid mode of GRASP (Section 2.5.4 of [I-D.ietf-anima-grasp])
      is not supported.

2.2.  Asynchronous Operations

   GRASP depends on asynchronous operations and wait states, and its
   messages are not idempotent, meaning that repeating a message may
   cause repeated changes of state in the recipient ASA.  Many ASAs will
   need to support several concurrent operations; for example an ASA
   might need to negotiate one objective with a peer while discovering
   and synchronizing a different objective with a different peer.
   Alternatively, an ASA which acts as a resource manager might need to
   run simultaneous negotiations for a given objective with multiple
   different peers.  Such an ASA will probably need to support
   uninterruptible atomic changes to its internal data structures, using
   a mechanism provided by the operating system and programming language
   in use.





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2.2.1.  Alternative Asynchronous Mechanisms

   Thus, some ASAs need to support asynchronous operations, and
   therefore the GRASP core must do so.  Depending on both the operating
   system and the programming language in use, there are various
   techniques for such parallel operations, three of which we consider
   here: multi-threading, an event loop structure using polling, and an
   event loop structure using callback functions.

   1.  In multi-threading, the operating system and language will
       provide the necessary support for asynchronous operations,
       including creation of new threads, context switching between
       threads, queues, locks, and implicit wait states.  In this case,
       API calls can be treated as simple synchronous function calls
       within their own thread, even if the function includes wait
       states, blocking and queueing.  Concurrent operations will each
       run in their own threads.  For example, the discover() call may
       not return until discovery results have arrived or a timeout has
       occurred.  If the ASA has other work to do, the discover() call
       must be in a thread of its own.

   2.  In an event loop implementation with polling, blocking calls are
       not acceptable.  Therefore all calls must be non-blocking, and
       the main loop could support multiple GRASP sessions in parallel
       by repeatedly polling each one for a change of state.  To
       facilitate this, the API implementation would provide non-
       blocking versions of all the functions that otherwise involve
       blocking and queueing.  In these calls, a 'noReply' code will be
       returned by each call instead of blocking, until such time as the
       event for which it is waiting (or a failure) has occurred.  Thus,
       for example, discover() would return 'noReply' instead of waiting
       until discovery has succeeded or timed out.  The discover() call
       would be repeated in every cycle of the main loop until it
       completes.  Effectively, it becomes a polling call.

   3.  In an event loop implementation with callbacks, the ASA
       programmer would provide a callback function for each
       asynchronous operation, e.g. discovery_received().  This would be
       called asynchronously when a reply is received or a failure such
       as a timeout occurs.

   The following calls involve waiting for a remote operation, so they
   could use a polling or callback mechanism.  In a threaded mechanism,
   they will usually require to be called in a separate thread:

      discover() whose callback would be discovery_received().





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      request_negotiate() whose callback would be
      negotiate_step_received().

      negotiate_step() whose callback would be
      negotiate_step_received().

      listen_negotiate() whose callback would be
      negotiate_step_received().

      synchronize() whose callback would be synchronization_received().

2.2.2.  Multiple Negotiation Scenario

   The design of GRASP allows the following scenario.  Consider an ASA
   "A" that acts as a resource allocator for some objective.  An ASA "B"
   launches a negotiation with "A" to obtain or release a quantity of
   the resource.  While this negotatition is under way, "B" chooses to
   launch a second simultaneous negotiation with "A" for a different
   quantity of the same resource.  "A" must therefore conduct two
   separate negotiation sessions at the same time with the same peer,
   and must not mix them up.

   Note that ASAs could be designed to avoid such a scenario, i.e.
   restricted to exactly one negotiation session at a time for a given
   objective, but this would be a voluntary restriction not required by
   the GRASP protocol.  In fact it is an assumption of GRASP that any
   ASA managing a resource may need to conduct multiple parallel
   negotiations, possibly with the same peer.  Communication patterns
   could be very complex, with a group of ASAs overlapping negotiations
   among themselves, as described in [I-D.ciavaglia-anima-coordination].
   Therefore, the API design allows for such scenarios.

   In the callback model, for the scenario just described, the ASAs "A"
   and "B" will each provide two instances of negotiate_step_received(),
   one for each session.  For this reason, each ASA must be able to
   distinguish the two sessions, and the peer's IP address is not
   sufficient for this.  It is also not safe to rely on transport port
   numbers for this, since future variants of GRASP might use shared
   ports rather than a separate port per session.  Hence the GRASP
   design includes a session identifier.  Thus, when necessary, a
   'session_nonce' parameter is used in the API to distinguish
   simultaneous GRASP sessions from each other, so that any number of
   sessions may proceed asynchronously in parallel.








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2.2.3.  Overlapping Sessions and Operations

   On the first call in a new GRASP session, the API returns a
   'session_nonce' value based on the GRASP session identifier.  This
   value must be used in all subsequent calls for the same session, and
   will be provided as a parameter in the callback functions.  By this
   mechanism, multiple overlapping sessions can be distinguished, both
   in the ASA and in the GRASP core.  The value of the 'session_nonce"
   is opaque to the ASA.

   An additional mechanism that might increase efficiency for polling
   implementations is to add a general call, say notify(), which would
   check the status of all outstanding operations for the calling ASA
   and return the session_nonce values for all sessions that have
   changed state.  This would eliminate the need for repeated calls to
   the individual functions returning a 'noReply'.  This call is not
   described below as the details are likely to be implementation-
   specific.

   An implication of the above for all GRASP implementations is that the
   GRASP core must keep state for each GRASP operation in progress, most
   likely keyed by the GRASP Session ID and the GRASP source address of
   the session initiator.  Even in a threaded implementation, the GRASP
   core will need such state internally.  The session_nonce parameter
   exposes this aspect of the implementation.

2.3.  API definition

   Some example logic flows for a resource management ASA are given in
   [I-D.carpenter-anima-asa-guidelines], which may be of help in
   understanding the following descriptions.  The next section describes
   parameters and data structures used in multiple API calls.  The
   following sections describe various groups of function APIs.  Those
   APIs that do not list asynchronous mechanisms are implicitly
   synchronous in their behaviour.

2.3.1.  Parameters and data structures

2.3.1.1.  Errorcode

   All functions in the API have an unsigned 'errorcode' integer as
   their return value (the first returned value in languages that allow
   multiple returned parameters).  An errorcode of zero indicates
   success.  Any other value indicates failure of some kind.  The first
   three errorcodes have special importance:






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   1.  Declined: used to indicate that the other end has sent a GRASP
       Negotiation End message (M_END) with a Decline option
       (O_DECLINE).

   2.  No reply: used in non-blocking calls to indicate that the other
       end has sent no reply so far (see Section 2.2).

   3.  Unspecified error: used when no more specific error code applies.

   Appendix A gives a full list of currently suggested error codes,
   based on implementation experience.  While there is no absolute
   requirement for all implementations to use the same error codes, this
   is highly recommended for portability of applications.

2.3.1.2.  Timeout

   Wherever a 'timeout' parameter appears, it is an integer expressed in
   milliseconds.  If it is zero, the GRASP default timeout
   (GRASP_DEF_TIMEOUT, see [I-D.ietf-anima-grasp]) will apply.  If no
   response is received before the timeout expires, the call will fail
   unless otherwise noted.

2.3.1.3.  Objective

   An 'objective' parameter is a data structure with the following
   components:

*  name (UTF-8 string) - the objective's name

*  neg (Boolean flag) - True if objective supports negotiation
   (default False)

*  synch (Boolean flag) - True if objective supports synchronization
   (default False)

*  dry (Boolean flag) - True if objective supports dry-run
   negotiation (default False)

   -  Note 1: Only one of 'synch' or 'neg' may be True.

   -  Note 2: 'dry' must not be True unless 'neg' is also True.

   -  Note 3: In a language such as C the preferred implementation
      may be to represent the Boolean flags as bits in a single byte.

*  loop_count (integer) - Limit on negotiation steps etc. (default
   GRASP_DEF_LOOPCT, see [I-D.ietf-anima-grasp])




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*  value - a specific data structure expressing the value of the
   objective.  The format is language dependent, with the constraint
   that it can be validly represented in CBOR.

   An essential requirement for all language mappings and all
   implementations is that, regardless of what other options exist
   for a language-specific representation of the value, there is
   always an option to use a raw CBOR data item as the value.  The
   API will then wrap this with CBOR Tag 24 as an encoded CBOR data
   item [RFC7049] for transmission via GRASP, and unwrap it after
   reception.

   The 'name' and 'value' fields are of variable length.  GRASP does
   not set a maximum length for these fields, but only for the total
   length of a GRASP message.  Implementations might impose length
   limits.

   An example data structure definition for an objective in the C
   language, assuming the use of a particular CBOR library, is:

 typedef struct {
    char *name;
    uint8_t flags;            // flag bits as defined by GRASP
    int loop_count;
    int value_size;           // size of value in bytes
    cbor_mutable_data cbor_value;
                              // CBOR bytestring (libcbor/cbor/data.h)
                 } objective;

   An example data structure definition for an objective in the
   Python language is:

 class objective:
    """A GRASP objective"""
    def __init__(self, name):
        self.name = name    # Unique name (string)
        self.negotiate = False  #True if objective supports negotiation
        self.dryrun = False     #True if objective supports dry-run neg.
        self.synch = False  # True if objective supports synch
        self.loop_count = GRASP_DEF_LOOPCT  # Default starting value
        self.value = 0      # Place holder; any valid Python object

2.3.1.4.  ASA_locator

   An 'ASA_locator' parameter is a data structure with the following
   contents:





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   *  locator - The actual locator, either an IP address or an ASCII
      string.

   *  ifi (integer) - The interface identifier index via which this was
      discovered - probably no use to a normal ASA

   *  expire (system dependent type) - The time on the local system
      clock when this locator will expire from the cache

   *  The following cover all locator types currently supported by
      GRASP:

      -  is_ipaddress (Boolean) - True if the locator is an IP address

      -  is_fqdn (Boolean) - True if the locator is an FQDN

      -  is_uri (Boolean) - True if the locator is a URI

   *  diverted (Boolean) - True if the locator was discovered via a
      Divert option

   *  protocol (integer) - Applicable transport protocol (IPPROTO_TCP or
      IPPROTO_UDP)

   *  port (integer) - Applicable port number

   The 'locator' field is of variable length in the case of an FQDN or a
   URI.  GRASP does not set a maximum length for this field, but only
   for the total length of a GRASP message.  Implementations might
   impose length limits.

2.3.1.5.  Tagged_objective

   A 'tagged_objective' parameter is a data structure with the following
   contents:

   *  objective - An objective

   *  locator - The ASA_locator associated with the objective, or a null
      value.











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2.3.1.6.  Asa_nonce

   Although an authentication and authorization scheme for ASAs has not
   been defined, the API provides a very simple hook for such a scheme.
   When an ASA starts up, it registers itself with the GRASP core, which
   provides it with an opaque nonce that, although not cryptographically
   protected, would be difficult for a third party to predict.  The ASA
   must present this nonce in future calls.  This mechanism will prevent
   some elementary errors or trivial attacks such as an ASA manipulating
   an objective it has not registered to use.

   Thus, in most calls, an 'asa_nonce' parameter is required.  It is
   generated when an ASA first registers with GRASP, and the ASA must
   then store the asa_nonce and use it in every subsequent GRASP call.
   Any call in which an invalid nonce is presented will fail.  It is an
   up to 32-bit opaque value (for example represented as a uint32_t,
   depending on the language).  It should be unpredictable; a possible
   implementation is to use the same mechanism that GRASP uses to
   generate Session IDs [I-D.ietf-anima-grasp].  Another possible
   implementation is to hash the name of the ASA with a locally defined
   secret key.

2.3.1.7.  Session_nonce

   In some calls, a 'session_nonce' parameter is required.  This is an
   opaque data structure as far as the ASA is concerned, used to
   identify calls to the API as belonging to a specific GRASP session
   (see Section 2.2).  In fully threaded implementations this parameter
   might not be needed, but it is included to act as a session handle if
   necessary.  It will also allow GRASP to detect and ignore malicious
   calls or calls from timed-out sessions.  A possible implementation is
   to form the nonce from the underlying GRASP Session ID and the source
   address of the session.

2.3.2.  Registration

   These functions are used to register an ASA and the objectives that
   it supports with the GRASP module.  If an authorization model is
   added to GRASP, these API calls would need to be modified
   accordingly.

   *  register_asa()

      -  Input parameter:

            name of the ASA (UTF-8 string)

      -  Return parameters:



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            errorcode (integer)

            asa_nonce (integer) (if successful)

      -  This initialises state in the GRASP module for the calling
         entity (the ASA).  In the case of success, an 'asa_nonce' is
         returned which the ASA must present in all subsequent calls.
         In the case of failure, the ASA has not been authorized and
         cannot operate.

   *  deregister_asa()

      -  Input parameters:

            asa_nonce (integer)

            name of the ASA (UTF-8 string)

      -  Return parameter:

            errorcode (integer)

      -  This removes all state in the GRASP module for the calling
         entity (the ASA), and deregisters any objectives it has
         registered.  Note that these actions must also happen
         automatically if an ASA crashes.

      -  Note - the ASA name is strictly speaking redundant in this
         call, but is present for clarity.

   *  register_objective()

      -  Input parameters:

            asa_nonce (integer)

            objective (structure)

            ttl (integer - default GRASP_DEF_TIMEOUT)

            discoverable (Boolean - default False)

            overlap (Boolean - default False)

            local (Boolean - default False)

      -  Return parameter:




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            errorcode (integer)

      -  This registers an objective that this ASA supports and may
         modify.  The 'objective' becomes a candidate for discovery.
         However, discovery responses should not be enabled until the
         ASA calls listen_negotiate() or listen_synchronize(), showing
         that it is able to act as a responder.  The ASA may negotiate
         the objective or send synchronization or flood data.
         Registration is not needed for "read-only" operations, i.e.,
         the ASA only wants to receive synchronization or flooded data
         for the objective concerned.

      -  The 'ttl' parameter is the valid lifetime (time to live) in
         milliseconds of any discovery response for this objective.  The
         default value should be the GRASP default timeout
         (GRASP_DEF_TIMEOUT, see [I-D.ietf-anima-grasp]).

      -  If the parameter 'discoverable' is True, the objective is
         immediately discoverable.  This is intended for objectives that
         are only defined for GRASP discovery, and which do not support
         negotiation or synchronization.

      -  If the parameter 'overlap' is True, more than one ASA may
         register this objective in the same GRASP instance.

      -  If the parameter 'local' is True, discovery must return a link-
         local address.  This feature is for objectives that must be
         restricted to the local link.

      -  This call may be repeated for multiple objectives.

   *  deregister_objective()

      -  Input parameters:

            asa_nonce (integer)

            objective (structure)

      -  Return parameter:

            errorcode (integer)

      -  The 'objective' must have been registered by the calling ASA;
         if not, this call fails.  Otherwise, it removes all state in
         the GRASP module for the given objective.





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2.3.3.  Discovery

   *  discover()

      -  Input parameters:

            asa_nonce (integer)

            objective (structure)

            timeout (integer)

            age_limit (integer)

      -  Return parameters:

            errorcode (integer)

            locator_list (structure)

      -  This returns a list of discovered 'ASA_locator's for the given
         objective.  Note that this structure includes all the fields
         described in Section 2.3.1.4.

      -  If the parameter 'age_limit' is greater than zero, any locally
         cached locators for the objective whose remaining lifetime in
         milliseconds is less than or equal to 'age_limit' are deleted
         first.  Thus 'age_limit' = 0 will flush all entries.

      -  If the parameter 'timeout' is zero, any remaining locally
         cached locators for the objective are returned immediately and
         no other action is taken.  (Thus, a call with 'age_limit' and
         'timeout' both equal to zero is pointless.)

      -  If the parameter 'timeout' is greater than zero, GRASP
         discovery is performed, and all results obtained before the
         timeout in milliseconds expires are returned.  If no results
         are obtained, an empty list is returned after the timeout.
         That is not an error condition.

      -  Asynchronous Mechanisms:

         o  Threaded implementation: This should be called in a separate
            thread if asynchronous operation is required.

         o  Event loop implementation: An additional read/write
            'session_nonce' parameter is used.  A callback may be used
            in the case of a non-zero tiemout.



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2.3.4.  Negotiation

   *  request_negotiate()

      -  Input parameters:

            asa_nonce (integer)

            objective (structure)

            peer (ASA_locator)

            timeout (integer)

      -  Return parameters:

            errorcode (integer)

            session_nonce (structure) (if successful)

            proffered_objective (structure) (if successful)

            reason (string) (if negotiation declined)

      -  This function opens a negotiation session between two ASAs.
         Note that GRASP currently does not support multi-party
         negotiation, which would need to be added as an extended
         function.

      -  The 'objective' parameter must include the requested value, and
         its loop count should be set to a suitable starting value by
         the ASA.  If not, the GRASP default will apply.

      -  Note that a given negotiation session may or may not be a dry-
         run negotiation; the two modes must not be mixed in a single
         session.

      -  The 'peer' parameter is the target node; it must be an
         'ASA_locator' as returned by discover().  If 'peer' is null,
         GRASP discovery is automatically performed first to find a
         suitable peer (i.e., any node that supports the objective in
         question).

      -  If the 'errorcode' return parameter is 0, the negotiation has
         successfully started.  There are then two cases:






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         1.  The 'session_nonce' parameter is null.  In this case the
             negotiation has succeeded immediately (the peer has
             accepted the request).  The returned 'proffered_objective'
             contains the value accepted by the peer.

         2.  The 'session_nonce' parameter is not null.  In this case
             negotiation must continue.  The 'session_nonce' must be
             presented in all subsequent negotiation steps.  The
             returned 'proffered_objective' contains the first value
             proffered by the negotiation peer.  The contents of this
             instance of the objective must be used in the subsequent
             negotiation call because it contains the updated loop
             count, sent by the negotiation peer.  The GRASP code
             automatically decrements the loop count by 1 at each step,
             and returns an error if it becomes zero.

             This function must be followed by calls to 'negotiate_step'
             and/or 'negotiate_wait' and/or 'end_negotiate' until the
             negotiation ends. 'request_negotiate' may then be called
             again to start a new negotiation.

      -  If the 'errorcode' parameter has the value 1 ('declined'), the
         negotiation has been declined by the peer (M_END and O_DECLINE
         features of GRASP).  The 'reason' string is then available for
         information and diagnostic use, but it may be a null string.
         For this and any other error code, an exponential backoff is
         recommended before any retry.

      -  Asynchronous Mechanisms:

         o  Threaded implementation: This should be called in a separate
            thread if asynchronous operation is required.

         o  Event loop implementation: The 'session_nonce' parameter is
            used to distinguish multiple simultaneous sessions.

      -  Use of dry run mode: This must be consistent within a GRASP
         session.  The state of the 'dry' flag in the initial
         request_negotiate() call must be the same in all subsequent
         negotiation steps of the same session.  The semantics of the
         dry run mode are built into the ASA; GRASP merely carries the
         flag bit.

      -  Special note for the ACP infrastructure ASA: It is likely that
         this ASA will need to discover and negotiate with its peers in
         each of its on-link neighbors.  It will therefore need to know
         not only the link-local IP address but also the physical
         interface and transport port for connecting to each neighbor.



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         One implementation approach to this is to include these details
         in the 'session_nonce' data structure, which is opaque to
         normal ASAs.

   *  listen_negotiate()

      -  Input parameters:

            asa_nonce (integer)

            objective (structure)

      -  Return parameters:

            errorcode (integer)

            session_nonce (structure) (if successful)

            requested_objective (structure) (if successful)

      -  This function instructs GRASP to listen for negotiation
         requests for the given 'objective'.  It also enables discovery
         responses for the objective, as mentioned under
         register_objective() in Section 2.3.2.

      -  Asynchronous Mechanisms:

         o  Threaded implementation: It will block waiting for an
            incoming request, so should be called in a separate thread
            if asynchronous operation is required.  Unless there is an
            unexpected failure, this call only returns after an incoming
            negotiation request.  If the ASA supports multiple
            simultaneous transactions, a new thread must be spawned for
            each new session.

         o  Event loop implementation: A 'session_nonce' parameter is
            used to distinguish individual sessions.  If the ASA
            supports multiple simultaneous transactions, a new event
            must be inserted in the event loop for each new session.

      -  This call only returns (threaded model) or triggers (event
         loop) after an incoming negotiation request.  When this occurs,
         'requested_objective' contains the first value requested by the
         negotiation peer.  The contents of this instance of the
         objective must be used in the subsequent negotiation call
         because it contains the loop count sent by the negotiation
         peer.  The 'session_nonce' must be presented in all subsequent
         negotiation steps.



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      -  This function must be followed by calls to 'negotiate_step'
         and/or 'negotiate_wait' and/or 'end_negotiate' until the
         negotiation ends. 'listen_negotiate' may then be called again
         to await a new negotiation.

      -  If an ASA is capable of handling multiple negotiations
         simultaneously, it may call 'listen_negotiate' simultaneously
         from multiple threads, or insert multiple events.  The API and
         GRASP implementation must support re-entrant use of the
         listening state and the negotiation calls.  Simultaneous
         sessions will be distinguished by the threads or events
         themselves, the GRASP session nonces, and the underlying
         unicast transport sockets.

   *  stop_listen_negotiate()

      -  Input parameters:

            asa_nonce (integer)

            objective (structure)

      -  Return parameter:

            errorcode (integer)

      -  Instructs GRASP to stop listening for negotiation requests for
         the given objective, i.e., cancels 'listen_negotiate'.

      -  Asynchronous Mechanisms:

         o  Threaded implementation: Must be called from a different
            thread than 'listen_negotiate'.

         o  Event loop implementation: no special considerations.

   *  negotiate_step()

      -  Input parameters:

            asa_nonce (integer)

            session_nonce (structure)

            objective (structure)

            timeout (integer)




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      -  Return parameters:

            Exactly as for 'request_negotiate'

      -  Executes the next negotation step with the peer.  The
         'objective' parameter contains the next value being proffered
         by the ASA in this step.

      -  Asynchronous Mechanisms:

         o  Threaded implementation: Called in the same thread as the
            preceding 'request_negotiate' or 'listen_negotiate', with
            the same value of 'session_nonce'.

         o  Event loop implementation: Must use the same value of
            'session_nonce' returned by the preceding
            'request_negotiate' or 'listen_negotiate'.

   *  negotiate_wait()

      -  Input parameters:

            asa_nonce (integer)

            session_nonce (structure)

            timeout (integer)

      -  Return parameters:

            errorcode (integer)

      -  Delay negotiation session by 'timeout' milliseconds, thereby
         extending the original timeout.  This function simply triggers
         a GRASP Confirm Waiting message (see [I-D.ietf-anima-grasp] for
         details).

      -  Asynchronous Mechanisms:

         o  Threaded implementation: Called in the same thread as the
            preceding 'request_negotiate' or 'listen_negotiate', with
            the same value of 'session_nonce'.

         o  Event loop implementation: Must use the same value of
            'session_nonce' returned by the preceding
            'request_negotiate' or 'listen_negotiate'.

   *  end_negotiate()



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      -  Input parameters:

            asa_nonce (integer)

            session_nonce (structure)

            result (Boolean)

            reason (UTF-8 string)

      -  Return parameters:

            errorcode (integer)

      -  End the negotiation session.

         'result' = True for accept (successful negotiation), False for
         decline (failed negotiation).

         'reason' = optional string describing reason for decline.

      -  Asynchronous Mechanisms:

         o  Threaded implementation: Called in the same thread as the
            preceding 'request_negotiate' or 'listen_negotiate', with
            the same value of 'session_nonce'.

         o  Event loop implementation: Must use the same value of
            'session_nonce' returned by the preceding
            'request_negotiate' or 'listen_negotiate'.

2.3.5.  Synchronization and Flooding

   *  synchronize()

      -  Input parameters:

            asa_nonce (integer)

            objective (structure)

            peer (ASA_locator)

            timeout (integer)

      -  Return parameters:

            errorcode (integer)



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            objective (structure) (if successful)

      -  This call requests the synchronized value of the given
         'objective'.

      -  Since this is essentially a read operation, any ASA can do it,
         unless an authorization model is added to GRASP in future.
         Therefore the API checks that the ASA is registered, but the
         objective does not need to be registered by the calling ASA.

      -  If the objective was already flooded, the flooded value is
         returned immediately in the 'result' parameter.  In this case,
         the 'peer' and 'timeout' are ignored.

      -  Otherwise, synchronization with a discovered ASA is performed.
         The 'peer' parameter is an 'ASA_locator' as returned by
         discover().  If 'peer' is null, GRASP discovery is
         automatically performed first to find a suitable peer (i.e.,
         any node that supports the objective in question).

      -  This call should be repeated whenever the latest value is
         needed.

      -  Asynchronous Mechanisms:

         o  Threaded implementation: Call in a separate thread if
            asynchronous operation is required.

         o  Event loop implementation: An additional read/write
            'session_nonce' parameter is used.

      -  Since this is essentially a read operation, any ASA can use it.
         Therefore GRASP checks that the calling ASA is registered but
         the objective doesn't need to be registered by the calling ASA.

      -  In the case of failure, an exponential backoff is recommended
         before retrying.

   *  listen_synchronize()

      -  Input parameters:

            asa_nonce (integer)

            objective (structure)

      -  Return parameters:




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            errorcode (integer)

      -  This instructs GRASP to listen for synchronization requests for
         the given objective, and to respond with the value given in the
         'objective' parameter.  It also enables discovery responses for
         the objective, as mentioned under register_objective() in
         Section 2.3.2.

      -  This call is non-blocking and may be repeated whenever the
         value changes.

   *  stop_listen_synchronize()

      -  Input parameters:

            asa_nonce (integer)

            objective (structure)

      -  Return parameters:

            errorcode (integer)

      -  This call instructs GRASP to stop listening for synchronization
         requests for the given 'objective', i.e. it cancels a previous
         listen_synchronize.

   *  flood()

      -  Input parameters:

            asa_nonce (integer)

            ttl (integer)

            tagged_objective_list (structure)

      -  Return parameters:

            errorcode (integer)

      -  This call instructs GRASP to flood the given synchronization
         objective(s) and their value(s) and associated locator(s) to
         all GRASP nodes.

      -  The 'ttl' parameter is the valid lifetime (time to live) of the
         flooded data in milliseconds (0 = infinity)




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      -  The 'tagged_objective_list' parameter is a list of one or more
         'tagged_objective' couplets.  The 'locator' parameter that tags
         each objective is normally null but may be a valid
         'ASA_locator'.  Infrastructure ASAs needing to flood an
         {address, protocol, port} 3-tuple with an objective create an
         ASA_locator object to do so.  If the IP address in that locator
         is the unspecified address ('::') it is replaced by the link-
         local address of the sending node in each copy of the flood
         multicast, which will be forced to have a loop count of 1.
         This feature is for objectives that must be restricted to the
         local link.

      -  The function checks that the ASA registered each objective.

      -  This call may be repeated whenever any value changes.

   *  get_flood()

      -  Input parameters:

            asa_nonce (integer)

            objective (structure)

      -  Return parameters:

            errorcode (integer)

            tagged_objective_list (structure) (if successful)

      -  This call instructs GRASP to return the given synchronization
         objective if it has been flooded and its lifetime has not
         expired.

      -  Since this is essentially a read operation, any ASA can do it.
         Therefore the API checks that the ASA is registered but the
         objective doesn't need to be registered by the calling ASA.

      -  The 'tagged_objective_list' parameter is a list of
         'tagged_objective' couplets, each one being a copy of the
         flooded objective and a coresponding locator.  Thus if the same
         objective has been flooded by multiple ASAs, the recipient can
         distinguish the copies.

      -  Note that this call is for advanced ASAs.  In a simple case, an
         ASA can simply call synchronize() in order to get a valid
         flooded objective.




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   *  expire_flood()

      -  Input parameters:

            asa_nonce (integer)

            tagged_objective (structure)

      -  Return parameters:

            errorcode (integer)

      -  This is a call that can only be used after a preceding call to
         get_flood() by an ASA that is capable of deciding that the
         flooded value is stale or invalid.  Use with care.

      -  The 'tagged_objective' parameter is the one to be expired.

2.3.6.  Invalid Message Function

   *  send_invalid()

      -  Input parameters:

            asa_nonce (integer)

            session_nonce (structure)

            info (bytes)

      -  Return parameters:

            errorcode (integer)

      -  Sends a GRASP Invalid Message (M_INVALID) message, as described
         in [I-D.ietf-anima-grasp].  Should not be used if
         end_negotiate() would be sufficient.  Note that this message
         may be used in response to any unicast GRASP message that the
         receiver cannot interpret correctly.  In most cases this
         message will be generated internally by a GRASP implementation.

         'info' = optional diagnostic data.  May be raw bytes from the
         invalid message.








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3.  Implementation Status [RFC Editor: please remove]

   A prototype open source Python implementation of GRASP, including an
   API similar to this document, has been used to verify the concepts
   for the threaded model.  It may be found at
   https://github.com/becarpenter/graspy with associated documentation
   and demonstration ASAs.

4.  Security Considerations

   Security issues for the GRASP protocol are discussed in
   [I-D.ietf-anima-grasp].  Authorization of ASAs is a subject for
   future study.

   The 'asa_nonce' parameter is used in the API as a first line of
   defence against a malware process attempting to imitate a
   legitimately registered ASA.  The 'session_nonce' parameter is used
   in the API as a first line of defence against a malware process
   attempting to hijack a GRASP session.

5.  IANA Considerations

   This document makes no request of the IANA.

6.  Acknowledgements

   Excellent suggestions were made by Ignas Bagdonas, Laurent Ciavaglia,
   Toerless Eckert, Guangpeng Li, Michael Richardson, Rob Wilton, and
   other participants in the ANIMA WG.

7.  References

7.1.  Normative References

   [I-D.ietf-anima-grasp]
              Bormann, C., Carpenter, B., and B. Liu, "A Generic
              Autonomic Signaling Protocol (GRASP)", Work in Progress,
              Internet-Draft, draft-ietf-anima-grasp-15, 13 July 2017,
              <https://tools.ietf.org/html/draft-ietf-anima-grasp-15>.

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

7.2.  Informative References






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   [I-D.carpenter-anima-asa-guidelines]
              Carpenter, B., Ciavaglia, L., Jiang, S., and P. Pierre,
              "Guidelines for Autonomic Service Agents", Work in
              Progress, Internet-Draft, draft-carpenter-anima-asa-
              guidelines-09, 25 July 2020, <https://tools.ietf.org/html/
              draft-carpenter-anima-asa-guidelines-09>.

   [I-D.ciavaglia-anima-coordination]
              Ciavaglia, L. and P. Peloso, "Autonomic Functions
              Coordination", Work in Progress, Internet-Draft, draft-
              ciavaglia-anima-coordination-01, 21 March 2016,
              <https://tools.ietf.org/html/draft-ciavaglia-anima-
              coordination-01>.

   [I-D.ietf-anima-autonomic-control-plane]
              Eckert, T., Behringer, M., and S. Bjarnason, "An Autonomic
              Control Plane (ACP)", Work in Progress, Internet-Draft,
              draft-ietf-anima-autonomic-control-plane-29, 11 September
              2020, <https://tools.ietf.org/html/draft-ietf-anima-
              autonomic-control-plane-29>.

   [I-D.ietf-anima-bootstrapping-keyinfra]
              Pritikin, M., Richardson, M., Eckert, T., Behringer, M.,
              and K. Watsen, "Bootstrapping Remote Secure Key
              Infrastructures (BRSKI)", Work in Progress, Internet-
              Draft, draft-ietf-anima-bootstrapping-keyinfra-44, 21
              September 2020, <https://tools.ietf.org/html/draft-ietf-
              anima-bootstrapping-keyinfra-44>.

   [I-D.ietf-anima-grasp-distribution]
              Liu, B., Xiao, X., Hecker, A., Jiang, S., Despotovic, Z.,
              and B. Carpenter, "Information Distribution over GRASP",
              Work in Progress, Internet-Draft, draft-ietf-anima-grasp-
              distribution-01, 1 September 2020,
              <https://tools.ietf.org/html/draft-ietf-anima-grasp-
              distribution-01>.

   [I-D.ietf-anima-reference-model]
              Behringer, M., Carpenter, B., Eckert, T., Ciavaglia, L.,
              and J. Nobre, "A Reference Model for Autonomic
              Networking", Work in Progress, Internet-Draft, draft-ietf-
              anima-reference-model-10, 22 November 2018,
              <https://tools.ietf.org/html/draft-ietf-anima-reference-
              model-10>.







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Appendix A.  Error Codes

   This Appendix lists the error codes defined so far, with suggested
   symbolic names and corresponding descriptive strings in English.  It
   is expected that complete API implementations will provide for
   localisation of these descriptive strings, and that additional error
   codes will be needed according to implementation details.

   ok               0 "OK"
   declined         1 "Declined"
   noReply          2 "No reply"
   unspec           3 "Unspecified error"
   ASAfull          4 "ASA registry full"
   dupASA           5 "Duplicate ASA name"
   noASA            6 "ASA not registered"
   notYourASA       7 "ASA registered but not by you"
   notBoth          8 "Objective cannot support both negotiation
                       and synchronization"
   notDry           9 "Dry-run allowed only with negotiation"
   notOverlap      10 "Overlap not supported by this implementation"
   objFull         11 "Objective registry full"
   objReg          12 "Objective already registered"
   notYourObj      13 "Objective not registered by this ASA"
   notObj          14 "Objective not found"
   notNeg          15 "Objective not negotiable"
   noSecurity      16 "No security"
   noDiscReply     17 "No reply to discovery"
   sockErrNegRq    18 "Socket error sending negotiation request"
   noSession       19 "No session"
   noSocket        20 "No socket"
   loopExhausted   21 "Loop count exhausted"
   sockErrNegStep  22 "Socket error sending negotiation step"
   noPeer          23 "No negotiation peer"
   CBORfail        24 "CBOR decode failure"
   invalidNeg      25 "Invalid Negotiate message"
   invalidEnd      26 "Invalid end message"
   noNegReply      27 "No reply to negotiation step"
   noValidStep     28 "No valid reply to negotiation step"
   sockErrWait     29 "Socket error sending wait message"
   sockErrEnd      30 "Socket error sending end message"
   IDclash         31 "Incoming request Session ID clash"
   notSynch        32 "Not a synchronization objective"
   notFloodDisc    33 "Not flooded and no reply to discovery"
   sockErrSynRq    34 "Socket error sending synch request"
   noListener      35 "No synch listener"
   noSynchReply    36 "No reply to synchronization request"
   noValidSynch    37 "No valid reply to synchronization request"
   invalidLoc      38 "Invalid locator"



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Appendix B.  Change log [RFC Editor: Please remove]

   draft-ietf-anima-grasp-api-07, 2020-10-13:

   *  Improved diagram and its description

   *  Added pointer to example logic flows

   *  Added note on variable length parameters

   *  Clarified that API decrements loop count automatically

   *  Other corrections and clarifications from AD review

   draft-ietf-anima-grasp-api-06, 2020-06-07:

   *  Improved diagram

   *  Numerous clarifications and layout changes

   draft-ietf-anima-grasp-api-05, 2020-05-08:

   *  Converted to xml2rfc v3

   *  Editorial fixes.

   draft-ietf-anima-grasp-api-04, 2019-10-07:

   *  Improved discussion of layering, mentioned daemon.

   *  Added callbacks and improved description of asynchronous
      operations.

   *  Described use case for 'session_nonce'.

   *  More explanation of 'asa_nonce'.

   *  Change 'discover' to use 'age_limit' instead of 'flush'.

   *  Clarified use of 'dry run'.

   *  Editorial improvements.

   draft-ietf-anima-grasp-api-03, 2019-01-21:

   *  Replaced empty "logic flows" section by "implementation status".

   *  Minor clarifications.



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   *  Editorial improvements.

   draft-ietf-anima-grasp-api-02, 2018-06-30:

   *  Additional suggestion for event-loop API.

   *  Discussion of error code values.

   draft-ietf-anima-grasp-api-01, 2018-03-03:

   *  Editorial updates

   draft-ietf-anima-grasp-api-00, 2017-12-23:

   *  WG adoption

   *  Editorial improvements.

   draft-liu-anima-grasp-api-06, 2017-11-24:

   *  Improved description of event-loop model.

   *  Changed intended status to Informational.

   *  Editorial improvements.

   draft-liu-anima-grasp-api-05, 2017-10-02:

   *  Added send_invalid()

   draft-liu-anima-grasp-api-04, 2017-06-30:

   *  Noted that simple nodes might not include the API.

   *  Minor clarifications.

   draft-liu-anima-grasp-api-03, 2017-02-13:

   *  Changed error return to integers.

   *  Required all implementations to accept objective values in CBOR.

   *  Added non-blocking alternatives.

   draft-liu-anima-grasp-api-02, 2016-12-17:

   *  Updated for draft-ietf-anima-grasp-09




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   draft-liu-anima-grasp-api-02, 2016-09-30:

   *  Added items for draft-ietf-anima-grasp-07

   *  Editorial corrections

   draft-liu-anima-grasp-api-01, 2016-06-24:

   *  Updated for draft-ietf-anima-grasp-05

   *  Editorial corrections

   draft-liu-anima-grasp-api-00, 2016-04-04:

   *  Initial version

Authors' Addresses

   Brian Carpenter
   School of Computer Science
   University of Auckland
   PB 92019
   Auckland 1142
   New Zealand

   Email: brian.e.carpenter@gmail.com


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

   Email: leo.liubing@huawei.com


   Wendong Wang
   BUPT University
   Beijing University of Posts & Telecom.
   No.10 Xitucheng Road
   Hai-Dian District, Beijing 100876
   P.R. China

   Email: wdwang@bupt.edu.cn




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Internet-Draft                  GRASP API                   October 2020


   Xiangyang Gong
   BUPT University
   Beijing University of Posts & Telecom.
   No.10 Xitucheng Road
   Hai-Dian District, Beijing 100876
   P.R. China

   Email: xygong@bupt.edu.cn











































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