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Network Working Group                                       A. Choudhary
Internet-Draft                                             Cisco Systems
Intended status: Standards Track                            May 12, 2018
Expires: November 13, 2018


                       QoS Telemetry Requirements
               draft-asechoud-rtgwg-qos-telemetry-req-00

Abstract

   This document discusses QoS requirements for data model based network
   telemetry.  QoS configuration and operational models have been
   defined as part of [I-D.asechoud-rtgwg-qos-model] and
   [I-D.asechoud-rtgwg-qos-oper-model] respectively.  This document
   describes the requirement to extend the models to support QoS
   Telemetry.

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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   This Internet-Draft will expire on November 13, 2018.

Copyright Notice

   Copyright (c) 2018 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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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.  Motivation  . . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   2
   3.  Requirements  . . . . . . . . . . . . . . . . . . . . . . . .   2
     3.1.  Granularity and Completeness  . . . . . . . . . . . . . .   2
     3.2.  Scale . . . . . . . . . . . . . . . . . . . . . . . . . .   3
     3.3.  Cadence . . . . . . . . . . . . . . . . . . . . . . . . .   3
     3.4.  Time-stamping . . . . . . . . . . . . . . . . . . . . . .   3
     3.5.  Grouping  . . . . . . . . . . . . . . . . . . . . . . . .   3
     3.6.  Filtering . . . . . . . . . . . . . . . . . . . . . . . .   3
     3.7.  Aggregation . . . . . . . . . . . . . . . . . . . . . . .   3
     3.8.  Threshold . . . . . . . . . . . . . . . . . . . . . . . .   4
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .   4
   5.  Acknowledgement . . . . . . . . . . . . . . . . . . . . . . .   4
   6.  Normative References  . . . . . . . . . . . . . . . . . . . .   4
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   5

1.  Motivation

   Network visibility is an important aspect of Network availability.
   QoS counters provide good insight into network device performance,
   congestion and security.  Continuous monitoring of each QoS resource
   may not be always desired.  Mechanism to monitor data set of QoS
   resources is needed.  The motivation of this document is to come up
   with the set of requirements of such a mechanism.

2.  Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [RFC2119].

3.  Requirements

3.1.  Granularity and Completeness

   Statistics passed for a QoS resource should be complete at the same
   time granular to avoid sending undesired information.  A particular
   counter in isolation may not provide sufficient information about a
   QoS resource.  E.g tail-drop counter of a queue is not sufficient to
   define state of a Queue unless some other counters like maximum queue
   size and average queue size is known.  Hence, it is important to get
   complete context of a resource based on device capability.




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3.2.  Scale

   It is important to have visibility into vast number of QoS resources
   in a network device on a regular basis.  Some of the devices, e.g.,
   may support millions of queues in a single device.  To be able to
   scale, it is desired to have data sets of important resources and
   monitor based on the need.

3.3.  Cadence

   Cadence defines the frequency of data collection from the forwarding
   path.  Cadence can be limited by device capability as well as based
   on the amount of data requested.  It can also be desired to have
   higher cadence of a resource in critical condition versus when it is
   not in critical condition.

3.4.  Time-stamping

   Time stamping defines the time when the data was collected from the
   data path.  Time stamping helps in calculating various traffic rates
   and draw right patterns.

3.5.  Grouping

   There may be multiple collectors of same telemetry data.  The purpose
   and focus of each collector may be different.  By defining the right
   set of groupings, a collector may be able to easily fetch the desired
   data.  E.g A network slice may define set of QoS resources on each
   interface.  A collector may be interested in a particular network
   slice may request the data accordingly.  Similarly, queues data on an
   interfaces or set of interfaces can be defined as group.

3.6.  Filtering

   Many times a collector is interested in specific data, e.g.  Real-
   time queue on an egress interface or metering ([RFC2697] and
   [RFC2698]) data on a best-effort traffic of an ingress interface.  An
   effective filtering mechanism can be done in the network device or by
   the collector.

3.7.  Aggregation

   Sometime aggregation of data becomes important to define meaning of
   the data.  E.g.  Consider a QoS policy applied on various ingress
   interfaces.  An underway DDOS attack can be better understood when
   all the traffic to a particular destination coming through various
   interfaces is summed up.  Aggregation can also be done for multiple




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   QoS resources within a Policy to save important hardware counter
   resources.

3.8.  Threshold

   Collector may not be interested in a QoS resource data till it is
   in critical condition.  E.g. a tail-drop is seen on a particular
   best-effort queue or queue is built up on a critical data of WFQ.
   Many times it follows a pattern, like 9 am in the morning when
   the trading starts, drops are seen on a particular queue but
   otherwise there are no drops.  So, it becomes important to observe a
   resource in a critical condition and avoid otherwise.  Defining a
   threshold helps collector and device alike.  Also, it is important to
   define how long a resource will be monitored once it is out of
   critical condition.

4.  Security Considerations

5.  Acknowledgement

6.  Normative References

   [I-D.asechoud-rtgwg-qos-model]
              Choudhary, A., Jethanandani, M., Strahle, N., Aries, E.,
              and I. Chen, "YANG Model for QoS", draft-asechoud-rtgwg-
              qos-model-05 (work in progress), March 2018.

   [I-D.asechoud-rtgwg-qos-oper-model]
              Choudhary, A. and I. Chen, "YANG Model for QoS Operational
              Parameters", draft-asechoud-rtgwg-qos-oper-model-01 (work
              in progress), May 2018.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

   [RFC2697]  Heinanen, J. and R. Guerin, "A Single Rate Three Color
              Marker", RFC 2697, DOI 10.17487/RFC2697, September 1999,
              <https://www.rfc-editor.org/info/rfc2697>.

   [RFC2698]  Heinanen, J. and R. Guerin, "A Two Rate Three Color
              Marker", RFC 2698, DOI 10.17487/RFC2698, September 1999,
              <https://www.rfc-editor.org/info/rfc2698>.







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Author's Address

   Aseem Choudhary
   Cisco Systems
   170 W. Tasman Drive
   San Jose, CA  95134
   US

   Email: asechoud@cisco.com


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