Control In-situ OAM Overhead with Segment IOAM
draft-song-ippm-segment-ioam-00

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ippm                                                        H. Song, Ed.
Internet-Draft                                                   T. Zhou
Intended status: Standards Track                                  Huawei
Expires: April 20, 2018                                 October 17, 2017

             Control In-situ OAM Overhead with Segment IOAM
                    draft-song-ippm-segment-ioam-00

Abstract

   This document describes a proposal to segment an in-situ OAM domain
   in order to control the iOAM data overhead, adapt to the path MTU
   limitations, and enable new applications.  We provide use cases to
   motivate our proposal and base the necessary modifications on the
   current in-situ OAM header format specification.

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Song & Zhou              Expires April 20, 2018                 [Page 1]
Internet-Draft                Segment IOAM                  October 2017

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 . . . . . . . . . . . . . . . . . . . . .   4
   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 iOAM header to
   save the data.  The current proposal is to label the overflow status
   and stop adding new node data to the packet, leading to loss of
   information.

   Even if the header has enough space to hold the iOAM data, the
   overhead may be too large and consume 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
   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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