Control In-situ OAM Overhead with Segment IOAM
draft-song-ippm-segment-ioam-01

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ippm                                                        H. Song, Ed.
Internet-Draft                                                   T. Zhou
Intended status: Standards Track                                  Huawei
Expires: October 19, 2018                                 April 17, 2018

             Control In-situ OAM Overhead with Segment IOAM
                    draft-song-ippm-segment-ioam-01

Abstract

   This document describes a proposal which partitions an in-situ OAM
   (iOAM) domain into multiple segments in order to control the iOAM
   data overhead, adapt to the path MTU limitations, and enable new
   applications.  We discuss several use cases to motivate our proposal
   and base the necessary modifications on the current in-situ OAM
   header format specification.

Status of This Memo

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   This Internet-Draft will expire on October 19, 2018.

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   Copyright (c) 2018 IETF Trust and the persons identified as the
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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.  Segment In-situ OAM . . . . . . . . . . . . . . . . . . . . .   3
     2.1.  Segment and Hops  . . . . . . . . . . . . . . . . . . . .   3
     2.2.  Considerations for Data Handling  . . . . . . . . . . . .   4
     2.3.  Use Cases . . . . . . . . . . . . . . . . . . . . . . . .   4
   3.  Security Considerations . . . . . . . . . . . . . . . . . . .   4
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   5
   5.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .   5
   6.  Contributors  . . . . . . . . . . . . . . . . . . . . . . . .   5
   7.  Informative References  . . . . . . . . . . . . . . . . . . .   5
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   5

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].

   iOAM may incur significant overhead on user packets.  The overhead
   includes the iOAM header and the node data list for each network
   element.

   The total size of data is limited by the MTU.  When the number of
   required data types is large and the forwarding path length is long,
   it is possible that there is not enough space in the user packets to
   hold the iOAM header and data.  The current proposal is to label the
   overflow status and stop adding new node data to the packet, leading
   to the loss of information.

   Even if the header has enough space to hold the iOAM data, the
   overhead may be too large and consumes too much bandwidth.  For
   example, if we assume moderate 20 bytes of data per node, a path with
   length of 10 will need 200 bytes to hold the data.  This will inflate
   small 64-byte packets by more than four times.  Even for the largest
   packet size (e.g., 1500 bytes), the overhead (>10%) is not
   negligible.  Therefore, we need to limit the iOAM data overhead
   without sacrificing the data collection capability.

   Here we have another interesting related issue.  Packets can be
   dropped anywhere in a network for various reasons.  If we can only
   collect iOAM data at the path end, we lose all data from the dropped

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   packets and have no idea where the packets are dropped.  This defies
   the purpose of iOAM and makes those iOAM-enabled nodes work in vain.
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