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Versions: 00

Network Working Group                                       B. Carpenter
Internet-Draft                                         Univ. of Auckland
Intended status: Informational                                  S. Jiang
Expires: March 16, 2018                                           B. Liu
                                            Huawei Technologies Co., Ltd
                                                      September 12, 2017


  Transferring Bulk Data over the GeneRic Autonomic Signaling Protocol
                                (GRASP)
                  draft-carpenter-anima-grasp-bulk-00

Abstract

   This document describes how bulk data may be transferred between
   Autonomic Service Agents via the GeneRic Autonomic Signaling Protocol
   (GRASP).

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
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   Drafts is at https://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
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   This Internet-Draft will expire on March 16, 2018.

Copyright Notice

   Copyright (c) 2017 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
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   publication of this document.  Please review these documents
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   include Simplified BSD License text as described in Section 4.e of




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   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  General Method for Bulk Transfer  . . . . . . . . . . . . . .   3
   3.  Example for File Transfer . . . . . . . . . . . . . . . . . .   4
   4.  Datagram Transport Layer  . . . . . . . . . . . . . . . . . .   7
   5.  Maximum Transmission Unit . . . . . . . . . . . . . . . . . .   8
   6.  Other Considerations  . . . . . . . . . . . . . . . . . . . .   8
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .   8
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   8
   9.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   8
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .   8
     10.1.  Normative References . . . . . . . . . . . . . . . . . .   9
     10.2.  Informative References . . . . . . . . . . . . . . . . .   9
   Appendix A.  Change log [RFC Editor: Please remove] . . . . . . .  10
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  10

1.  Introduction

   The document [I-D.liu-anima-grasp-distribution] discusses how
   information may be distributed within the secure Autonomic Networking
   Infrastructure (ANI) [I-D.ietf-anima-reference-model].  Specifically,
   it describes using the Synchronization and Flood Synchronization
   mechanisms of the GeneRic Autonomic Signaling Protocol (GRASP)
   [I-D.ietf-anima-grasp] for this purpose.  However, those mechanisms
   are limited to distributing GRASP Objective Options contained in
   messages that cannot exceed the GRASP maximum message size of 2048
   bytes.

   There are scenarios in autonomic networks where this restriction is a
   problem.  One example is the distribution of network policy in
   lengthy formats such as YANG or JSON.  Another case might be an
   Autonomic Service Agent (ASA) uploading a log file to the Network
   Operations Center (NOC).  A third case might be a supervisory system
   downloading a software upgrade to an autonomic node.

   Naturally, an existing solution such as a secure file transfer
   protocol or secure HTTP might be used for this.  Other management
   protocols such as syslog [RFC5424] or NETCONF [RFC6241] might also be
   used for related purposes, or might be mapped directly over GRASP.
   The present document, however, applies to any scenario where it is
   preferable to re-use the autonomic networking infrastructure itself
   rather than an additional mechanism, but there is a need to transfer
   a large amount of data.  The basic model is to use the GRASP




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   Negotiation process to transfer and acknowledge multiple blocks of
   data in successive negotiation steps.

   NOTE: This is an early draft of a solution.  As the specification
   becomes more mature, the authors expect it to become precise enough
   to be placed on the standards track.

2.  General Method for Bulk Transfer

   As for any GRASP operation, the two participants are considered to be
   Autonomic Service Agents (ASAs) and they communicate using a specific
   GRASP Objective Option, containing its own name, some flag bits, a
   loop count, and a value.  In bulk transfer, we can model the ASA
   acting as the source of the transfer as a download server, and the
   destination as a download client.  Compared to a normal GRASP
   negotiation, the communication pattern is slightly asymmetric:

   1.  The client first discovers the server by the GRASP discovery
       mechanism (M_DISCOVERY and M_RESPONSE messages).

   2.  The client then sends a GRASP negotiation request (M_REQ_NEG
       message).  The value of the objective expresses the requested
       item (e.g., a file name - see the next section for a detailed
       example).

   3.  The server replies with a negotiation step (M_NEGOTIATE message).
       The value of the objective is the first section of the requested
       item (e.g., the first block of the requested file as a raw byte
       string).

   4.  The client replies with a negotiation step (M_NEGOTIATE message).
       The value of the objective is a simple acknowledgement (e.g., the
       text string 'ACK').

   The last two steps repeat until the transfer is complete.  The server
   signals the end by transferring an empty byte string as the final
   value.  In this case the client responds with a normal end to the
   negotiation (M_END message with an O_ACCEPT option).

   Errors of any kind are handled with the normal GRASP mechanisms, in
   particular by an M_END message with an O_DECLINE option in either
   direction.

   The block size must be chosen such that each step does not exceed the
   GRASP message size limit of 2048 bits.

   This approach is safe since each block must be positively
   acknowledged, and data transfer errors will be detected by TCP.  If a



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   future variant of GRASP runs over UDP, the mandatory UDP checksum for
   IPv6 will detect such errors.  The method does not currently specify
   retransmission for failed blocks, so a failed transfer will need to
   be restarted.  In an enterprise network with low bit error rates,
   this is not considered a serious issue.

   An observant reader will notice that the GRASP loop count mechanism,
   intended to terminate endless negotiations, will cause a problem for
   large transfers.  For this reason, both the client and server must
   artificially increment the loop count by 1 before each negotiation
   step.

   If network load is a concern, the data rate can be limited by
   inserting a delay before each negotiation step, with the GRASP
   timeout set accordingly.  Either the server or the client, or both,
   could insert such a delay.  Also, either side could use the GRASP
   Confirm Waiting (M_WAIT) message to slow the other side down.

   The description above concerns bulk download from a server
   (responding ASA) to a client (requesting ASA).  The data transfer
   could also be in the opposite (upload) direction with minor
   modifications to the procedure: the client would send the data blocks
   and the server would send acknowledgements.

3.  Example for File Transfer

   This example describes a client ASA requesting a file download from a
   server ASA.

   Firstly we define a GRASP objective informally:

   ["411:mvFile", 3, 6, value]

   The formal CDDL definition [I-D.ietf-cbor-cddl] is:

   mvfile-objective = ["411:mvFile", objective-flags, loop-count, value]

   objective-flags = ; as in the GRASP specification
   loop-count = ; as in the GRASP specification
   value = any

   The objective-flags field is set to indicate negotiation.

   Dry run mode must not be used.

   The loop-count is set to a suitable value to limit the scope of
   discovery.  A suggested default value is 6.




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   The value takes the following forms:

   o  In the initial request from the client, a UTF-8 string containing
      the requested file name (with file path if appropriate).

   o  In negotiation steps from the server, a byte string containing at
      most 1024 bytes.  However:

      *  If the file does not exist, the first negotiation step will
         return an M_END, O_DECLINE response.

      *  After sending the last block, the next and final negotiation
         step will send an empty byte string as the value.

   o  In negotiation steps from the client, the value is the UTF-8
      string 'ACK'.

   Note that the block size of 1024 is chosen to guarantee not only that
   each GRASP message is below the size limit, but also that only one
   TCP data packet will be needed, even on an IPv6 network with a
   minimum link MTU.

   We now present outline pseudocode for the client and the server ASA.
   The API documented in [I-D.liu-anima-grasp-api] is used in a
   simplified way, and error handling is not shown in detail.


























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   Pseudo code for client ASA (request and receive a file):

   requested_obj = objective('411:mvFile')
   locator = discover(requested_obj)
   requested_obj.value = 'etc/test.pdf'
   received_obj = request_negotiate(requested_obj, locator)
   if error_code == declined:
       #no such file
       exit

   file = open(requested_obj.value)
   file.write(received_obj.value) #write to file
   eof = False
   while not eof:
       received_obj.value = 'ACK'
       received_obj.loop_count = received_obj.loop_count + 1
       received_obj = negotiate_step(received_obj)
       if received_obj.value == null:
           end_negotiate(True)
           file.close()
           eof = True
       else:
           file.write(received_obj.value) #write to file

   #file received
   exit

























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   Pseudo code for server ASA (await request and send a file):

   supported_obj = objective('411:mvFile')
   requested_obj = listen_negotiate(supported_obj)
   file = open(requested_obj.value) #open the source file
   if no such file:
       end_negotiate(False) #decline negotiation
       exit

   eof = False
   while not eof:
       chunk = file.read(1024) #next block of file
       requested_obj.value = chunk
       requested_obj.loop_count = requested_obj.loop_count + 1
       requested_obj = negotiate_step(requested_obj)
       if chunk == null:
           file.close()
           eof = True
           end_negotiate(True)
           exit
       if requested_obj.value != 'ACK':
           #unexpected reply...

4.  Datagram Transport Layer

   The above description and example assume that GRASP is implemented
   over a reliable transport layer such as TCP, such that lost or
   corrupted messages need not be considered.  In the event that GRASP
   is implemented over an unreliable transport layer such as UDP, it
   would be necessary to add a block number to both the data block and
   acknowledgement objectives, so that missing blocks can be
   retransmitted, or duplicate blocks can be ignored.  For example, the
   objective in Section 3 would become:

   mvfile-objective = ["411:mvFile", objective-flags, loop-count, value]

   objective-flags = ; as in the GRASP specification
   loop-count = ; as in the GRASP specification
   value = [block-number, any]
   block-number = uint

   It would also be necessary for the transport layer to detect data
   errors, for example by enabling UDP checksums.








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5.  Maximum Transmission Unit

   In an IPv6 environment, a minimal MTU of 1280 bytes can be assumed,
   and assuming that high throughput is not a requirement, bulk
   transfers can be designed to match that MTU.  However, there are
   environments where the underlying physical MTU is much smaller.  For
   example, on an IEEE 802.15.4 network it may be less than 100 bytes
   [RFC4944].  In such a case, a bulk transfer solution has several
   choices:

   1.  Accept the overhead of an adaptation layer, and therefore assume
       a network-layer MTU of 1280 bytes.

   2.  Attempt to determine the actual MTU available without lower-layer
       fragmentation.

   3.  Attempt to determine a message size that provides optimum
       performance.

   TBD: further discussion?

6.  Other Considerations

   TBD - discussion of specific use cases?

   TBD - discussion of user space API for bulk transfer?

7.  Security Considerations

   All GRASP transactions are secured by the mandatory security
   substrate required by [I-D.ietf-anima-grasp].  No additional security
   issues are created by the application of GRASP described in this
   document.

8.  IANA Considerations

   This document makes no request of the IANA.

9.  Acknowledgements

   TBD.

10.  References








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10.1.  Normative References

   [I-D.ietf-anima-grasp]
              Bormann, C., Carpenter, B., and B. Liu, "A Generic
              Autonomic Signaling Protocol (GRASP)", draft-ietf-anima-
              grasp-15 (work in progress), July 2017.

   [I-D.ietf-cbor-cddl]
              Birkholz, H., Vigano, C., and C. Bormann, "Concise data
              definition language (CDDL): a notational convention to
              express CBOR data structures", draft-ietf-cbor-cddl-00
              (work in progress), July 2017.

10.2.  Informative References

   [I-D.ietf-anima-reference-model]
              Behringer, M., Carpenter, B., Eckert, T., Ciavaglia, L.,
              Pierre, P., Liu, B., Nobre, J., and J. Strassner, "A
              Reference Model for Autonomic Networking", draft-ietf-
              anima-reference-model-04 (work in progress), July 2017.

   [I-D.liu-anima-grasp-api]
              Carpenter, B., Liu, B., Wang, W., and X. Gong, "Generic
              Autonomic Signaling Protocol Application Program Interface
              (GRASP API)", draft-liu-anima-grasp-api-04 (work in
              progress), June 2017.

   [I-D.liu-anima-grasp-distribution]
              Liu, B. and S. Jiang, "Information Distribution over
              GRASP", draft-liu-anima-grasp-distribution-04 (work in
              progress), May 2017.

   [RFC4944]  Montenegro, G., Kushalnagar, N., Hui, J., and D. Culler,
              "Transmission of IPv6 Packets over IEEE 802.15.4
              Networks", RFC 4944, DOI 10.17487/RFC4944, September 2007,
              <https://www.rfc-editor.org/info/rfc4944>.

   [RFC5424]  Gerhards, R., "The Syslog Protocol", RFC 5424,
              DOI 10.17487/RFC5424, March 2009,
              <https://www.rfc-editor.org/info/rfc5424>.

   [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,
              <https://www.rfc-editor.org/info/rfc6241>.






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

   draft-carpenter-anima-grasp-bulk-00, 2017-09-12:

   Initial version.

Authors' Addresses

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

   Email: brian.e.carpenter@gmail.com


   Sheng Jiang
   Huawei Technologies Co., Ltd
   Q14, Huawei Campus, No.156 Beiqing Road
   Hai-Dian District, Beijing, 100095
   P.R. China

   Email: jiangsheng@huawei.com


   Bing Liu
   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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