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ippm                                                        H. Song, Ed.
Internet-Draft                                                   T. Zhou
Intended status: Standards Track                                  Huawei
Expires: October 18, 2018                                 April 16, 2018


                   In-situ OAM Data Validation Option
             draft-song-ippm-ioam-data-validation-option-02

Abstract

   This document describes several potential performance scalability and
   capability issues when implementing in-situ OAM on heterogenous
   target network elements.  The document proposes the corresponding
   solutions and modifications to the current in-situ OAM specification
   to mitigate the issues.  Specifically, in-situ OAM is extended with
   data validation fields to cope with the node processing capability.
   We provide use cases to motivate our proposal and base the
   modifications on the current in-situ OAM header format specification.

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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   Internet-Drafts are draft documents valid for a maximum of six months
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   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on October 18, 2018.

Copyright Notice

   Copyright (c) 2018 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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   (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



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   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  In-situ OAM Sampling and Data Validation  . . . . . . . . . .   3
     2.1.  Valid Node Bitmap and Valid Data Bitmap . . . . . . . . .   3
     2.2.  Use Cases . . . . . . . . . . . . . . . . . . . . . . . .   5
   3.  Security Considerations . . . . . . . . . . . . . . . . . . .   6
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
   5.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .   6
   6.  Contributors  . . . . . . . . . . . . . . . . . . . . . . . .   6
   7.  Informative References  . . . . . . . . . . . . . . . . . . .   6
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   6

1.  Introduction

   In-situ OAM (iOAM) [I-D.brockners-inband-oam-requirements] records
   OAM information within user packets while the packets traverse a
   network.  The data types and data formats for in-situ OAM data
   records have been defined in [I-D.ietf-ippm-ioam-data].  We identify
   several scalability issues for implementing the current iOAM
   specification and propose solutions in this draft.

   iOAM can designate the flow to add the iOAM header and collect data
   on the flow forwarding path.  The flow can have arbitrary
   granularity.  However, processing the data can be a heavy burden for
   the network nodes, especially when some data needs to be calculated
   by the node (e.g., the transit delay).  If the flow traffic is heavy,
   the node may not be able to handle the iOAM processing so many
   performance issues may occur, such as long latency and packet drop.

   Although it is good for the OAM applications to gain the detailed
   information on every packet at every node, in many cases, such
   information is often repetitive and redundant.  The large quantity of
   data would also burden the management plane which needs to collect
   and stream the data for analytics.  It is also possible that some
   nodes cannot provide the requested data at all or are unwilling to
   provide some data for security or privacy concerns.  So a trade-off
   is needed to balance the performance impact and the data availability
   and completeness.

   We provide several motivating examples.  To minimize the network
   impact, a network operator decides to collect the iOAM data only for
   initial and last flow packets (e.g., TCP packets with SYN, FIN, and
   RST flags).



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   In another example, a head node alternates two iOAM headers with each
   requesting a subset of iOAM data.  Hence, each node on the flow path
   only needs to handle partial data.  The requests can be balanced
   without exhausting the network nodes.

   The above two cases can be realized by manipulating the iOAM header
   at the domain edge.  It is also possible that a node is temporarily
   under heavy traffic load.  It is in danger of dropping packets if it
   tries to satisfy all the iOAM data requests.  It is also possible
   that, due to the privacy concern or capability issues, a node cannot
   satisfy the data request indicated in the iOAM header.  In these
   cases, it would rather deny some requests than drop user traffic.
   This case can be realized by adding some auxiliary fields in the iOAM
   header.

   More examples are listed in Section 2.2.

2.  In-situ OAM Sampling and Data Validation

   Based on the observation in Section 1, the source edge node should be
   able to define either the period or the probability to add the iOAM
   header to the selected flow packet.  In this way, only a subset of
   the flow/sec packets would carry the OAM data, which not only reduces
   the overall iOAM data quantity but also reduces the processing work
   load of the network nodes.

   Different data type bitmap templates can also be defined and used
   selectively.  For example, template A includes a subset of data and
   template B includes another subset of data.  The two templates can be
   used in the iOAM header for a flow alternately or in any predefined
   pattern.  This is also an effective way to reduce the node processing
   load.

2.1.  Valid Node Bitmap and Valid Data Bitmap

   It is possible that even an iOAM capable node will not add data to
   the node data list as requested.  In some cases, a node can be too
   busy to handle the data request or some types of the requested data
   is not available due to privacy and capability reasons.  Therefore,
   we propose to add two bitmaps, a valid node bitmap and a valid data
   bitmap, to the iOAM specification.

   The Node Valid Bitmap (NVB) is inserted before the Node Data List as
   shown in Figure 1.  Each bit in the NVB corresponds to a hop on the
   packet's forwarding path.  The bits are listed in the same order as
   the hop on the packet's forwarding path.  The bitmap is set to all
   one at first.  If a hop cannot add data to the Node Data List, the
   corresponding bit in the NVB is cleared to 0.  The bit location for a



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   hop can be calculated from the length field (e.g, the bit index is
   equal to SSize-RHop).The valid node data items in the node data list
   is equal to the number of 1's in the NVB.


       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |    Base OAM Trace Type        |NodeLen|  Flags  | Octets-left |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                 Node Valid Bitmap (NVB)                       |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                                                               |
      |                  Node Data List []                            |
      |                                                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


         Figure 1: iOAM Header Format with Node Valid Bitmap (NVB)

   NVB allows the head node to invalidate some nodes in advance.  For
   example, if the head node wants to exclude the odd-numbered nodes
   from adding iOAM data, it can set all the corresponding bits to 0.
   Then at each node, if it finds its corresponding bit in the NVB is 0,
   it will simply skip the iOAM processing.

   In addition to NVB, for each node data in the node data list, a Data
   Valid Bitmap (DVB) is added before the node data.  The number of bits
   in the DVB is equal to the number of 1's in the OAM Trace Type
   bitmaps (excluding the next trace type bitmap indicator bits).  When
   the bit is set, the corresponding data is valid in the node;
   otherwise, the corresponding data is invalid so the management plane
   should ignore it after the data is collected.

   The size of the DVB can be padded to two or four bytes, which allow
   up to 16 or 32 types of data to be included in a node.  The node data
   list format with the enhanced DVB is shown in Figure 2.














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       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |   Data Valid Bitmap (DVB) |             Padding               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                                                               |
      |                 Node Data List [i]                            |
      |                                                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


           Figure 2: iOAM Node Data with Data Valid Bitmap (DVB)

2.2.  Use Cases

   We give some examples to show the usefulness of in-situ OAM sampling
   and data validation features.

   o  An application needs to track a flow's forwarding path and knows
      the path will not change frequently, so it sets a low sampling
      rate to periodically insert the iOAM header to request the node
      ID.

   o  In a heterogeneous data plane, some nodes support to provide data
      x but the other nodes do not support it.  However, an application
      is still interested in collecting data x if available.  In this
      case, iOAM header can still be configured to ask for data x but
      the nodes that cannot provide the data simply invalidates it by
      resetting the corresponding bit in the valid data bitmap.

   o  Multiple sampling rate and multiple data request schema can be
      defined for a flow based on applications requirements and the data
      property, so for a flow packet, there can be no iOAM header or
      different iOAM headers.  The node does not need to process all
      data all the time.

   o  For security reason, a node decides to not participate in the iOAM
      data collection.  While it processes the other iOAM header fields
      as usual, it does not set the node valid bit in the Node Valid
      Bitmap and add node data to the Node Data List.

   o  To reduce the node processing load, the head node alternately uses
      two NVBs with one of them invalidating all the even-numbered nodes
      and the other invalidating all the odd-numbered nodes.  Therefore,
      a node only needs to process the iOAM for every two packets of the
      flow.





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3.  Security Considerations

   There is no extra security considerations beyond those have been
   identified by in-situ OAM protocol.

4.  IANA Considerations

   This memo includes no request to IANA.

5.  Acknowledgments

   We would like to thank Frank Brockners, Carlos Pignataro, Shwetha
   Bhandari, and Tal Mizrahi for helpful comments and suggestions.

6.  Contributors

   The document is inspired by numerous discussions with James N.
   Guichard.  He also provided significant comments and suggestions to
   help improve this document.

7.  Informative References

   [I-D.brockners-inband-oam-requirements]
              Brockners, F., Bhandari, S., Dara, S., Pignataro, C.,
              Gredler, H., Leddy, J., Youell, S., Mozes, D., Mizrahi,
              T., <>, P., and r. remy@barefootnetworks.com,
              "Requirements for In-situ OAM", draft-brockners-inband-
              oam-requirements-02 (work in progress), October 2016.

   [I-D.ietf-ippm-ioam-data]
              Brockners, F., Bhandari, S., Pignataro, C., Gredler, H.,
              Leddy, J., Youell, S., Mizrahi, T., Mozes, D., Lapukhov,
              P., Chang, R., and d. daniel.bernier@bell.ca, "Data Fields
              for In-situ OAM", draft-ietf-ippm-ioam-data-00 (work in
              progress), September 2017.

Authors' Addresses

   Haoyu Song (editor)
   Huawei
   2330 Central Expressway
   Santa Clara, 95050
   USA

   Email: haoyu.song@huawei.com






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   Tianran Zhou
   Huawei
   156 Beiqing Road
   Beijing, 100095
   P.R. China

   Email: zhoutianran@huawei.com












































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