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Network Working Group                                             B. Liu
Internet-Draft                                       Huawei Technologies
Intended status: Standards Track                            July 8, 2019
Expires: January 9, 2020


  Instant Congestion Assessment Network (iCAN) for Data Plane Traffic
                              Engineering
                           draft-liu-ican-00

Abstract

   iCAN (instant Congestion Assessment Network) is a set of mechanisms
   running directly on network nodes:

   o  To adjust the flows paths based on real-time measurement of the
      candidate paths.

   o  The measurement is to reflect the congestion situation of each
      path, so that the ingress nodes could decide which flows need to
      be switched from a path to another.

   This is something that current SDN and TE technologies can hardly
   achieve:

   o  SDN Controller is slow and far from the data plane, it is neither
      able to assess the real-time congestion situation of each path,
      nor able to assure the data plane always go as expected
      (especially in SRv6 scenarios).  However, iCAN can work with SDN
      perfectly: controller planning multi-path transmission, and iCAN
      does the flow optimization automatically.

   o  Traditional TE is not able to adjust the flow paths in real-time.

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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   material or to cite them other than as "work in progress."



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   This Internet-Draft will expire on January 9, 2020.

Copyright Notice

   Copyright (c) 2019 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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   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  iCAN Architecture and Key Technical Requirements  . . . . . .   3
     2.1.  Architecture  . . . . . . . . . . . . . . . . . . . . . .   3
     2.2.  Key technical requirements  . . . . . . . . . . . . . . .   5
       2.2.1.  Path quality assessment . . . . . . . . . . . . . . .   5
       2.2.2.  Recognition and statistic of flows in devices . . . .   5
       2.2.3.  Flow switching between paths  . . . . . . . . . . . .   5
   3.  Use Cases of iCAN . . . . . . . . . . . . . . . . . . . . . .   6
     3.1.  Network load balancing  . . . . . . . . . . . . . . . . .   6
     3.2.  SLA assurance . . . . . . . . . . . . . . . . . . . . . .   6
     3.3.  Fine-Granularity reliability  . . . . . . . . . . . . . .   6
   4.  Implementation Scenarios  . . . . . . . . . . . . . . . . . .   6
     4.1.  iCAN with SRv6  . . . . . . . . . . . . . . . . . . . . .   6
     4.2.  iCAN with VxLAN . . . . . . . . . . . . . . . . . . . . .   7
     4.3.  iCAN with MPLS/MPLS-TE  . . . . . . . . . . . . . . . . .   7
   5.  Standardization Requirements  . . . . . . . . . . . . . . . .   7
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   7
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   7
   8.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   7
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   8
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .   8
     9.2.  Informative References  . . . . . . . . . . . . . . . . .   8
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   8

1.  Introduction

   Traditional IP routing is shortest path based on static metrics,
   which can fulfil basic requirement of connectivity.  MPLS-TE brings
   the capability of utilizing non-shortest paths, thus traffic dispatch



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   is doable; however, MPLS-TE in only a complementary mechanism because
   of the scalability issue.  Segment routing provides even more
   flexibility that paths could be easily programmed; and along with the
   controller, it could be scaled.

   However, the above mentioned mechanism all run in the control plane,
   which implies that they are not able to sense the data plane
   situation in real-time, thus they are mostly for relative static
   planning/controlling (minuets, hours or even day-level) of network
   traffic and not able to adapt to the microscopic traffic change in
   real-time (e.g. mili-second level).  So, in real bearer networks
   (metro, backbones etc.), it is always underload so that the redundant
   resources could tolerant the traffic burst, results in a significant
   waste of network resources.

   This draft proposes the iCAN (Instant Congestion Assessment Network)
   architecture to achieve autonomous adapt to traffic changes in real-
   time in terms of switching flows between multiple forwarding paths.
   iCAN includes following things:

   o  A mechanism between ingress and egress nodes to assess the path
      congestion situation in RTT level speed, to recognize which paths
      are underload and which are heavy loaded.

   o  Recognizing big flows and small flows in the device, in real time

   o  Ingress node dispatches flows to multiple paths, to make load
      balance, or to guarantee SLA for specific flows

   This draft also discusses use cases and implementation scenarios of
   iCAN.

2.  iCAN Architecture and Key Technical Requirements

2.1.  Architecture
















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                 +-----------+
                 |           |
                 | Controller|
                 |           |
                 +-----------+
                       |
          0.Multi-path |
              Planning |
                       |
                       |
                       v
                 +-----------+  --------Path 1------------  +----------+
 Imcoming Flows  |  Ingress  |3.Flow swithing between paths | Egress   |
 --------------> |  Router   |  --------Path N------------  | Router   |
                 |           |                              |          |
                 +-/------\--+ <--------------------------> +----------+
                  /        \   1.Path Quality Assessment
                 / 2. Flow  \ (simultaneusly on multiple paths)
                /  recognition
               /              \

   As above figure shows, there are 3 entities:

   1.  Controller

       -  Responsible for planning multiple paths for a set of flows
          that could be aggregated to a pair of Ingress/Egress routers.

       -  After delivering the planned paths to the ingress router, the
          controller would need nothing to do.

   2.  Ingress router:

       -  Serves as a local "controller" for the iCAN system.

       -  Responsible for triggering the path congestion assessment,
          which is coordinated with the egress router through a
          measurement protocol.

       -  After getting the assessment results, the ingress router would
          calculate which flows need to be switched to a different path,
          in order to make the paths load balanced or to assure the
          transport quality of a certain of important flows.

       -  In order to do the path switching calculation, the ingress
          router needs to recognize the TopN flow passing by it, since
          switching the big flows would make the most effort.




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   3.  Egress router:

       -  Only needs to coordinate with the ingress router to do the
          path assessment.

2.2.  Key technical requirements

2.2.1.  Path quality assessment

   o  Req-1: the assessment MUST reflex the congestion status of the
      paths.  (Note: a candidate congestion metric is proposed as:
      [I-D.dang-ippm-congestion].)

   o  Req-2: the assessment SHOULD be done within a RTT timeslot.  Since
      iCAN is to adapt the traffic change in real-time, the assessment
      needs to be done very fast.

   o  Req-3: the assessment MUST be done for multiple paths between the
      same ingress/egress routes simultaneously.  (Note: a candidate
      congestion metric is proposed as:
      [I-D.dang-ippm-multiple-path-measurement].)

2.2.2.  Recognition and statistic of flows in devices

   o  Req-1: the device SHOULD be able to recognize TopN big flows
      within a timeslot.

   o  Req-2: the device MAY need to statistic all flows' amount within a
      timeslot.

2.2.3.  Flow switching between paths

   o  Req-1: the device SHOULD be able to recognize flow let.  The flow
      switching is done from the next flow let.

   o  Req-2: the device MAY need to actively generate gap to
      artificially create flow let.  If the flow needs to be switched
      immediately, then the device would need to make the gap, to avoid
      out-of-order packets arriving to the destination through multiple
      paths.

   o  Req-3: the device SHOULD avoid oscillation of frequently switching
      flows from one to another.

   o  Req-4: multiple ingress devices SHOULD be able to coordinate so
      that they won't switch flows to the shared path at the same time,
      to avoid potential congestion in the shared path.




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3.  Use Cases of iCAN

3.1.  Network load balancing

   Background problem: traffic is not balanced in current metro network.

   While some links are heavily loaded, others might be still lightly
   loaded: unbalance could lows down the service quality (e.g.  SLA
   could not be guaranteed in the heavily loaded links/paths); unbalance
   could lows down the network utilization ratio (normally with 30%,
   e.g. a 100G physical capacity network can only bear at most 30G
   traffic, a huge waste of network infrastructure).

   iCAN could be used for load balance among the multiple paths between
   a pair of ingress/egress nodes.  Once the network is balanced, the
   real throughput of the network could be elevated significantly.

3.2.  SLA assurance

   Since iCAN could switch flow in real-time, it can guarantee a set of
   important flows.  Once the path which carries the important flows is
   to be congested, the other flows could be switched to alternative
   paths, and the important flows would stablely running in the original
   path.

   (More content TBD)

3.3.  Fine-Granularity reliability

   Traditional reliability protocols such as BFD, can only assess the
   link on or off.  With the path congestion assessment ability, iCAN
   could also asses the quality degradation.

   (More content TBD)

4.  Implementation Scenarios

4.1.  iCAN with SRv6

   -  SR Multiple Explicit Paths

      For example, there are 3 paths between the ingress and egress
      nodes, and the multi-path is defined as a SR-List containing
      LSP1/2/3.

      The probe message detects the congestion status of the three SR-
      list paths.  The edge device adjusts the load balancing between
      the three paths according to the congestion status of the three



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      SR-lists, and switch the flows from the path with a high
      congestion to the path with a low congestion.

   -  SR Multiple Explicit+Loose Paths

      In loose path scenario, there needs to be an additional approach
      to probe the specific paths of a SR tunnel.  After that,
      operations on the probed paths are the same as explicit path
      scenario.

4.2.  iCAN with VxLAN

   TBD.

4.3.  iCAN with MPLS/MPLS-TE

   TBD.

5.  Standardization Requirements

   1.  Multi-path Planning (North Interface between Controller and
       devices)

   2.  Path Congestion Assesment (Horizontal Interface between devices),
       mostly regarding to Req-1&2&3 described in Section 2.2.1 .

   3.  Flow Switching Negotiation (Horizontal Interface between
       devices), mostly regarding to Req-3&4 described in Section 2.2.3
       .

   (More content TBD.)

6.  Security Considerations

   TBD.

7.  IANA Considerations

   TBD.

8.  Acknowledgements

   Very valuable comments were from Shunsuke Homma, Mikael Abrahamsson
   and Bruno Decraene.

   A commercial router hardware based prototype had been implemented to
   prove the machinisms discussed in the document are workable.




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9.  References

9.1.  Normative References

   [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>.

   [RFC2629]  Rose, M., "Writing I-Ds and RFCs using XML", RFC 2629,
              DOI 10.17487/RFC2629, June 1999,
              <https://www.rfc-editor.org/info/rfc2629>.

9.2.  Informative References

   [I-D.dang-ippm-congestion]
              Dang, J. and J. Wang, "A One-Path Congestion Metric for
              IPPM", draft-dang-ippm-congestion-01 (work in progress),
              March 2019.

   [I-D.dang-ippm-multiple-path-measurement]
              Dang, J. and J. Wang, "A Multi-Path Concurrent Measurement
              Protocol for IPPM", draft-dang-ippm-multiple-path-
              measurement-01 (work in progress), March 2019.

Author's Address

   Bing Liu
   Huawei Technologies
   Q14, Huawei Campus
   No.156 Beiqing Road
   Hai-Dian District, Beijing  100095
   P.R. China

   Email: leo.liubing@huawei.com
















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