TEAS Working Group                                               A. Wang
Internet-Draft                                             China Telecom
Intended status: Experimental                                    Q. Zhao
Expires: December 28, 2018                                   B. Khasanov
                                                                 H. Chen
                                                                   P. Mi
                                                     Huawei Technologies
                                                               R. Mallya
                                                        Juniper Networks
                                                                 S. Peng
                                                         ZTE Corporation
                                                           June 26, 2018

                        PCE in Native IP Network


   This document defines the framework for CCDR 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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   This Internet-Draft will expire on December 28, 2018.

Copyright Notice

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

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   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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   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Conventions used in this document . . . . . . . . . . . . . .   3
   3.  Dual-BGP framework for simple topology  . . . . . . . . . . .   3
   4.  Dual-BGP in large Scale Topology  . . . . . . . . . . . . . .   4
   5.  Multi-BGP for Extended Traffic Differentiation  . . . . . . .   5
   6.  CCDR based framework for Multi-BGP strategy deployment  . . .   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. Normative References  . . . . . . . . . . . . . . . . . . . .   9
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  10

1.  Introduction

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

   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 CCDR traffic engineering
   within Native IP network, using Dual/Multi-BGP session strategy and
   CCDR architecture, to meet the above requirements in dynamical and
   central control mode.  Future PCEP protocol extensions to transfer
   the key parameters between PCE and the underlying network
   devices(PCC) are provided in draft

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 idea of the Dual-BGP framework for this simple topology is
   the following:

   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

   So, 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 the different dedicated physical

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   If there is more traffic between IP12 and IP22 that needs to be
   assured , one can add more physical links on R1 and R2 to reach the
   loopback address lo1(also the next hop for BGP Peer pair2).  In this
   cases the prefixes that advertised by two BGP peer need not be

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

   Such decouple philosophy gives the network operator more flexible
   control ability on the network traffic, get 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 protocol.

                                  |  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 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 one described in the Dual-BGP
   simple topology usage case.

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   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
   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 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.

   o  Traffic that requires high bandwidth links

   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 the traffic pass one
   single path, no ECMP distribution on the parallel links is required.

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   It is difficult and almost impossible to provide an end-to-end (E2E)
   path with latency, latency variation, packet loss, and bandwidth
   utilization constraints to meet the above requirements in large scale
   IP-based network via the traditional distributed routing protocol,
   but these requirements can be solved using the CCDR architecture
   since the PCE has the overall network view, can collect real network
   topology and network performance information about the underlying
   network, select the appropriate path to meet the various network
   performance requirements of different traffic type.

6.  CCDR based framework for Multi-BGP strategy deployment

   With the advent of SDN concepts towards pure IP networks, it is
   possible now to accomplish the central and dynamic control of network
   traffic according to the application's various requirements.  The
   procedure to implement the dynamic deployment of Multi-BGP strategy
   is the following:

   o  PCE gets topology and link utilization information from the
      underlying network, calculate 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 advertise 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 volume of the 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
      link.  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 why 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 traditional 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 scalability when comparing with the solution
   from BGP flowspec or Openflow.

8.2.  High Availability

   CCDR framework is based on the traditional 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.

   From PCE/SDN-controller HA side we will rely on existing HA solutions
   of SDN controllers such as clustering.

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 sub
   domain can be upgraded first, and then the traffic can be assured
   between different sub domains.  Within each sub domain, the traffic
   will be forwarded along the best-effort path.  Service provider can
   selectively upgrade the routers on each sub-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 described in document
   [RFC5440] and [RFC8253]

10.  IANA Considerations

   This document does not require any IANA actions.

11.  Normative References

              Wang, A., Khasanov, B., Cheruathur, S., and C. Zhu, "PCEP
              Extension for Native IP Network", draft-ietf-pce-pcep-
              extension-native-ip-00 (work in progress), June 2018.

              Wang, A., Huang, X., Qou, C., Huang, L., and K. Mi, "CCDR
              Scenario, Simulation and Suggestion", draft-ietf-teas-
              native-ip-scenarios-00 (work in progress), February 2018.

              Zhao, Q., Li, Z., Khasanov, B., Ke, Z., Fang, L., Zhou,
              C., Communications, T., and A. Rachitskiy, "The Use Cases
              for Using PCE as the Central Controller(PCECC) of LSPs",
              draft-ietf-teas-pcecc-use-cases-01 (work in progress), May

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

   [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,

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   [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, 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

   Huaimo Chen
   Huawei Technologies
   Boston, MA

   Email: huaimo.chen@huawei.com

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   Penghui Mi
   Huawei Technologies
   Tower C of Bldg.2, Cloud Park, No.2013 of Xuegang Road
   Bantian,Longgang District, Shenzhen  518129

   Email: mipenghui@huawei.com

   Raghavendra Mallya
   Juniper Networks
   1133 Innovation Way
   Sunnyvale, California  94089

   Email: rmallya@juniper.net

   Shaofu Peng
   ZTE Corporation
   No.68 Zijinghua Road,Yuhuatai District
   Nanjing  210012

   Email: peng.shaofu@zte.com.cn

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