TEAS Working Group                                               A. Wang
Internet-Draft                                             China Telecom
Intended status: Experimental                                    Q. Zhao
Expires: April 24, 2019                                      B. Khasanov
                                                                 H. Chen
                                                     Huawei Technologies
                                                               R. Mallya
                                                        Juniper Networks
                                                        October 21, 2018

                        PCE in Native IP Network


   This document defines the CCDR framework for traffic engineering
   within native IP network, using Dual/Multi-BGP session strategy and
   PCE-based central control architecture.  The proposed central mode
   control framework conforms to the concept that defined in [RFC8283].
   The scenario and simulation results of CCDR traffic engineering is
   described in draft [I-D.ietf-teas-native-ip-scenarios].

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."

   This Internet-Draft will expire on April 24, 2019.

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
   Provisions Relating to IETF Documents
   (https://trustee.ietf.org/license-info) in effect on the date of

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   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Conventions used in this document . . . . . . . . . . . . . .   3
   3.  Dual-BGP Framework for Simple Topology  . . . . . . . . . . .   3
   4.  Dual-BGP Framework in Large Scale Topology  . . . . . . . . .   4
   5.  Multi-BGP Strategy for Extended Traffic Differentiation . . .   5
   6.  CCDR Procedures for Multi-BGP Strategy  . . . . . . . . . . .   6
   7.  PCEP Extension for Key Parameters Delivery  . . . . . . . . .   7
   8.  Deployment Consideration  . . . . . . . . . . . . . . . . . .   7
     8.1.  Scalability . . . . . . . . . . . . . . . . . . . . . . .   8
     8.2.  High Availability . . . . . . . . . . . . . . . . . . . .   8
     8.3.  Incremental deployment  . . . . . . . . . . . . . . . . .   8
   9.  Security Considerations . . . . . . . . . . . . . . . . . . .   8
   10. IANA Considerations . . . . . . . . . . . . . . . . . . . . .   9
   11. Contributors  . . . . . . . . . . . . . . . . . . . . . . . .   9
   12. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . .   9
   13. Normative References  . . . . . . . . . . . . . . . . . . . .   9
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  10

1.  Introduction

   Draft [I-D.ietf-teas-native-ip-scenarios] describes the scenario and
   simulation results for traffic engineering in native IP network.  In
   summary, the requirements for traffic engineering in native IP
   network are the followings:

   o  No complex MPLS signaling procedure.

   o  End to End traffic assurance, determined QoS behavior.

   o  Identical deployment method for intra- and inter- domain.

   o  No influence to existing router forward behavior.

   o  Can utilize the power of centrally control(PCE) and flexibility/
      robustness of distributed control protocol.

   o  Coping with the differentiation requirements for large amount
      traffic and prefixes.

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   o  Flexible deployment and automation control.

   This document defines the framework for traffic engineering within
   native IP network, using Dual/Multi-BGP session strategy, to meet the
   above requirements in dynamical and central control mode.  The
   related PCEP protocol extensions to transfer the key parameters
   between PCE and the underlying network devices(PCC) are provided in
   draft [I-D.ietf-pce-pcep-extension-native-ip].

2.  Conventions used in this document

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   document are to be interpreted as described in RFC 2119 [RFC2119] .

3.  Dual-BGP Framework for Simple Topology

   Dual-BGP framework for simple topology is illustrated in Fig.1, which
   is comprised by SW1, SW2, R1, R2.  There are multiple physical links
   between R1 and R2.  Traffic between IP11 and IP21 is normal traffic,
   traffic between IP12 and IP22 is priority traffic that should be
   treated differently.

   Only native IGP/BGP protocol is deployed between R1 and R2.  The
   traffic between each address pair may change timely and the
   corresponding source/destination addresses of the traffic may also
   change dynamically.

   The key ideas of the Dual-BGP framework for this simple topology are
   the followings:

   o  Build two BGP sessions between R1 and R2, via the different
      loopback address lo0, lo1 on these routers.

   o  Send different prefixes via the two BGP sessions.  (For example,
      IP11/IP21 via the BGP pair 1 and IP12/IP22 via the BGP pair 2).

   o  Set the explicit peer route on R1 and R2 respectively for BGP next
      hop of lo0, lo1 to different physical link address between R1 and

   The traffic between the IP11 and IP21, and the traffic between IP12
   and IP22 will go through different physical links between R1 and R2,
   each type of traffic occupy different dedicated physical links.

   If there is more traffic between IP12 and IP22 that needs to be
   assured , one can add more physical links between R1 and R2 to reach
   the loopback address lo1(also the next hop for BGP Peer pair2).  In

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   this cases the prefixes that advertised by two BGP peers need not be

   If, for example, there is traffic from another address pair that
   needs to be assured (for example IP13/IP23), and the total volume of
   assured traffic does not exceed the capacity of the previous
   appointed physical links, one need only to advertise the newly added
   source/destination prefixes via the BGP peer pair2.  The traffic
   between IP13/IP23 will go through the assigned dedicated physical
   links as the traffic between IP12/IP22.

   Such decouple philosophy gives network operator flexible control
   ability on the network traffic, achieve the determined QoS assurance
   effect to meet the application's requirement.  No complex MPLS signal
   procedures is introduced, the router need only support native IP

                                  |  BGP Peer Pair2  |
                                  |lo1           lo1 |
                                  |                  |
                                  |  BGP Peer Pair1  |
                       IP12       |lo0           lo0 |       IP22
                       IP11       |                  |       IP21
                                      Links Group

                     Fig.1 Design Philosophy for Dual-BGP Framework

4.  Dual-BGP Framework in Large Scale Topology

   When the assured traffic spans across one large scale network, as
   that illustrated in Fig.2, the dual BGP sessions cannot be
   established hop by hop especially for the iBGP within one AS.

   For such scenario, we should consider to use the Route Reflector (RR)
   to achieve the similar Dual-BGP effect, select one router which
   performs the role of RR (for example R3 in Fig.2), every other edge
   router will establish two BGP peer sessions with the RR, using their
   different loopback addresses respectively.  The other two steps for
   traffic differentiation are same as that described in the Dual-BGP
   simple topology usage case.

   For the example shown in Fig.2, if we select the R1-R2-R4-R7 as the
   dedicated path, then we should set the explicit peer routes on these
   routers respectively, pointing to the BGP next hop (loopback

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   addresses of R1 and R7, which are used to send the prefix of the
   assured traffic) to the actual address of the physical link.

                         |                            |
                         |        |          |        |

               Fig.2 Dual-BGP Framework for Large Scale Network

5.  Multi-BGP Strategy for Extended Traffic Differentiation

   In general situation, several additional traffic differentiation
   criteria exist, including:

   o  Traffic that requires low latency links and is not sensitive to
      packet loss.

   o  Traffic that requires low packet loss but can endure higher

   o  Traffic that requires lowest jitter path.

   These different traffic requirements can be summarized in the
   following table:

         | Flow No. |    Latency  |  Packet Loss  |   Jitter        |
         |  1       |    Low      |   Normal      |   Don't care    |
         |  2       |   Normal    |   Low         |   Dont't care   |
         |  3       |   Normal    |   Normal      |   Low           |
                    Table 1. Traffic Requirement Criteria

   For Flow No.1, we can select the shortest distance path to carry the
   traffic; for Flow No.2, we can select the idle links to form its end
   to end path; for Flow No.3, we can let all assured traffic pass one
   single path, no ECMP distribution on the parallel links is required.

   It is almost impossible to provide an end-to-end (E2E) path with
   latency, jitter, packet loss constraints to meet the above
   requirements in large scale IP-based network via the distributed
   routing protocol, but these requirements can be solved using the CCDR
   framework since the PCE has the overall network view, can collect

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   real network topology and network performance information about the
   underlying network, select the appropriate path to meet various
   network performance requirements of different traffic.

6.  CCDR Procedures for Multi-BGP Strategy

   The procedures to implement the Multi-BGP strategy are the

   o  PCE gets topology and link utilization information from the
      underlying network, calculates the appropriate link path upon
      application's requirements..

   o  PCE sends the key parameters to edge/RR routers(R1, R7 and R3 in
      Fig.3) to build multi-BGP peer relations and advertises different
      prefixes via them.

   o  PCE sends the route information to the routers (R1,R2,R4,R7 in
      Fig.3) on forwarding path via PCEP, to build the path to the BGP
      next-hop of the advertised prefixes.

   o  If the assured traffic prefixes were changed but the total volume
      of assured traffic does not exceed the physical capacity of the
      previous end-to-end path, then PCE needs only change the related
      information on edge routers (R1,R7 in Fig.3).

   o  If the volume of assured traffic exceeds the capacity of previous
      calculated path, PCE must recalculate the appropriate path to
      accommodate the exceeding traffic via some new end-to-end physical
      links.  After that PCE needs to update on-path routers to build
      such path hop by hop.

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                        ***********+ PCE+*************
                        *          +--*-+            *
                        *           / * \            *
                        *             *              *
                    PCEP*       BGP-LS/SNMP          *PCEP
                        *             *              *
                        *             *           \  * /
                      \ * /           *            \ */
                        |                            |
                        |                            |
                        |        |          |        |
                        |        |          |        |

              Fig.3 PCE based framework for Multi-BGP deployment

7.  PCEP Extension for Key Parameters Delivery

   The PCEP protocol needs to be extended to transfer the following key

   o  BGP peer address and advertised prefixes.

   o  Explicit route information to BGP next hop of advertised prefixes.

   Once the router receives such information, it should establish the
   BGP session with the peer appointed in the PCEP message, advertise
   the prefixes that contained in the corresponding PCEP message, and
   build the end to end dedicated path hop by hop.  Details of
   communications between PCEP and BGP subsystems in router's control
   plane are out of scope of this draft and will be described in
   separate draft [I-D.ietf-pce-pcep-extension-native-ip] .

   The reason that we selected PCEP as the southbound protocol instead
   of OpenFlow, is that PCEP is suitable for the changes in control
   plane of the network devices, there OpenFlow dramatically changes the
   forwarding plane.  We also think that the level of centralization
   that requires by OpenFlow is hardly achievable in many today's SP
   networks so hybrid BGP+PCEP approach looks much more interesting.

8.  Deployment Consideration

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8.1.  Scalability

   In CCDR framework, PCE needs only to influence the edge routers for
   the prefixes differentiation via the multi-BGP deployment.  The route
   information for these prefixes within the on-path routers were
   distributed via the BGP protocol.  Unlike the solution from BGP
   Flowspec, the on-path router need only keep the specific policy
   routes to the BGP next-hop of the differentiate prefixes, not the
   specific routes to the prefixes themselves.  This can lessen the
   burden from the table size of policy based routes for the on-path
   routers, and has more scalabilities when comparing with the solution
   from BGP flowspec or Openflow.

8.2.  High Availability

   CCDR framework is based on the distributed IP protocol.  If the PCE
   failed, the forwarding plane will not be impacted, as the BGP session
   between all devices will not flap, and the forwarding table will
   remain the same.  If one node on the optimal path is failed, the
   assurance traffic will fall over to the best-effort forwarding path.
   One can even design several assurance paths to load balance/hot
   standby the assurance traffic to meet the path failure situation, as
   done in MPLS FRR.

   For high availability of PCE/SDN-controller, operator should rely on
   existing HA solutions for SDN controller, such as clustering
   technology and deployment.

8.3.  Incremental deployment

   Not every router within the network support will support the PCEP
   extension that defined in [I-D.ietf-pce-pcep-extension-native-ip]
   simultaneously.  For such situations, router on the edge of domain
   can be upgraded first, and then the traffic can be assured between
   different domains.  Within each domain, the traffic will be forwarded
   along the best-effort path.  Service provider can selectively upgrade
   the routers on each domain in sequence.

9.  Security Considerations

   Solution described in this draft puts more requirements on the
   function of PCE and its communication with the underlay devices.  The
   PCE should have the capability to calculate the loop-free e2e path
   upon the status of network condition and the service requirements in
   real time.  The PCE need also to consider the router order during
   deployment to eliminate the possible transient traffic loop.

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   This solution does not require the change of forward behavior on the
   underlay devices, then there will no additional security impact for
   the devices.

   When deploy the solution on network, service provider should also
   consider more on the protection of SDN controller and their
   communication with the underlay devices, which is described in
   document [RFC5440] and [RFC8253]

10.  IANA Considerations

   This document does not require any IANA actions.

11.  Contributors

   Penghui Mi and Shaofu Peng contribute the contents of this draft.

12.  Acknowledgement

   The author would like to thank Deborah Brungard, Adrian Farrel,
   Huaimo Chen, Vishnu Beeram, Lou Berger, Dhruv Dhody and Jessica Chen
   for their supports and comments on this draft.

13.  Normative References

              Wang, A., Khasanov, B., Cheruathur, S., and C. Zhu, "PCEP
              Extension for Native IP Network", draft-ietf-pce-pcep-
              extension-native-ip-01 (work in progress), June 2018.

              Wang, A., Huang, X., Qou, C., Li, Z., Huang, L., and P.
              Mi, "CCDR Scenario, Simulation and Suggestion", draft-
              ietf-teas-native-ip-scenarios-01 (work in progress), June

              Zhao, Q., Li, Z., Khasanov, B., Dhody, D., Ke, Z., Fang,
              L., Zhou, C., Communications, T., Rachitskiy, A., and A.
              Gulida, "The Use Cases for Path Computation Element (PCE)
              as a Central Controller (PCECC).", draft-ietf-teas-pcecc-
              use-cases-02 (work in progress), October 2018.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,

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   [RFC5440]  Vasseur, JP., Ed. and JL. Le Roux, Ed., "Path Computation
              Element (PCE) Communication Protocol (PCEP)", RFC 5440,
              DOI 10.17487/RFC5440, March 2009,

   [RFC8253]  Lopez, D., Gonzalez de Dios, O., Wu, Q., and D. Dhody,
              "PCEPS: Usage of TLS to Provide a Secure Transport for the
              Path Computation Element Communication Protocol (PCEP)",
              RFC 8253, DOI 10.17487/RFC8253, October 2017,

   [RFC8283]  Farrel, A., Ed., Zhao, Q., Ed., Li, Z., and C. Zhou, "An
              Architecture for Use of PCE and the PCE Communication
              Protocol (PCEP) in a Network with Central Control",
              RFC 8283, DOI 10.17487/RFC8283, December 2017,

Authors' Addresses

   Aijun Wang
   China Telecom
   Beiqijia Town, Changping District
   Beijing  102209

   Email: wangaj.bri@chinatelecom.cn

   Quintin Zhao
   Huawei Technologies
   125 Nagog Technology Park
   Acton, MA  01719

   Email: quintin.zhao@huawei.com

   Boris Khasanov
   Huawei Technologies
   Moskovskiy Prospekt 97A
   St.Petersburg  196084

   Email: khasanov.boris@huawei.com

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   Huaimo Chen
   Huawei Technologies
   Boston, MA

   Email: huaimo.chen@huawei.com

   Raghavendra Mallya
   Juniper Networks
   1133 Innovation Way
   Sunnyvale, California  94089

   Email: rmallya@juniper.net

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