TEAS Working Group                                               A.Wang
Internet Draft                                            China Telecom
                                                           Quintin Zhao
                                                         Boris Khasanov
                                                            HuaiMo Chen
                                                    Huawei Technologies
                                                             Penghui Mi
                                                        Tencent Company

Intended status: Experimental Track                   February 13, 2018
Expires: August 12, 2018

                         PCE in Native IP Network

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    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.

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    The proposed central mode control framework conforms to the concept
    that defined in RFC " An Architecture for Use of PCE and the PCE
    Communication Protocol (PCEP) in a Network with Central Control".

    The scenario and simulation results of CCDR traffic engineering is
    described in draft "CCDR Scenario, Simulation and Suggestion".

Table of Contents

   1. Introduction ................................................. 2
   2. Dual-BGP framework for simple topology. ...................... 3
   3. Dual-BGP in large Scale Topology ............................. 4
   4. Multi-BGP for Extended Traffic Differentiation ............... 5
   5. CCDR based framework for Multi-BGP strategy deployment........ 6
   6. PCEP extension for key parameters delivery. .................. 7
   7. CCDR Deployment Consideration ................................ 7
   8. Security Considerations....................................... 8
   9. IANA Considerations .......................................... 8
   10. Conclusions ................................................. 8
   11. References .................................................. 9
      11.1. Normative References.................................... 9
      11.2. Informative References.................................. 9
   12. Acknowledgments ............................................ 10

1. Introduction

   Draft [I-D.draft-wang-teas-ccdr] 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 followings.
   1) No complex MPLS signaling procedure.
   2) End to End traffic assurance, determined QoS behavior.
   3) Identical deployment method for intra- and inter- domain.
   4) No influence to existing router forward behavior.
   5) Can utilize the power of centrally control(PCE) and
      flexibility/robustness of distributed control protocol.
   6) Coping with the differentiation requirements for large amount
      traffic and prefixes.
   7) 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 [draft-wang-pcep-extension-native-IP]

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2. 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:
    1) Build two BGP sessions between R1 and R2, via the different loopback
       address lo0, lo1 on these routers.
    2) 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).
    3) 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

   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.

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   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

3. 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.

   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

                     |                            |

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                     |        |          |        |

             Fig.2 Dual-BGP Framework for large scale network

4. 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 latency
   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.

   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

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   network, select the appropriate path to meet the various network
   performance requirements of different traffic type.

5. 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:
    1) PCE gets topology and link utilization information from the
      underlying network, calculate the appropriate link path upon
      application's requirements.
    2) 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.
    3) 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.
    4) 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).
    5) 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.

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

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                     |        |          |        |
                     |        |          |        |

           Fig.3 PCE based framework for Multi-BGP deployment

6. PCEP extension for key parameters delivery.

   The PCEP protocol needs to be extended to transfer the following key
   1) BGP peer address and advertised prefixes.
   2) 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.[draft-wang-pce-extension for 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.

7. CCDR Deployment Consideration

   CCDR framework requires the parallel work of 2 subsystems in router's
   control plane: PCE (PCEP) and BGP as well as coordination between
   them, so it might require additional planning work before deployment.

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

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   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 [draft-wang-pce-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.

8. Security Considerations


9. IANA Considerations


10. Conclusions


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11. References

11.1. Normative References

   [RFC5440]Vasseur, JP., Ed., and JL. Le Roux, Ed., "Path

             Computation Element (PCE) Communication Protocol

             (PCEP)", RFC 5440, March 2009,


   [RFC8283] A.Farrel, Q.Zhao et al.," An Architecture for Use of PCE
   and the PCE Communication Protocol (PCEP) in a Network with Central
   Control", [RFC8283], December 2017

11.2. Informative References


   A.Wang, X.Huang et al. "CCDR Scenario, Simulation and Suggestion"


   [I-D. draft-ietf-teas-pcecc-use-cases]

   Quintin Zhao, Robin Li, Boris Khasanov et al. "The Use Cases for
   Using PCE as the Central Controller(PCECC) of LSPs



   [draft-wang-pcep-extension for native IP]

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   Aijun Wang, Boris Khasanov et al. "PCEP Extension for Native IP
   Network" https://datatracker.ietf.org/doc/draft-wang-pce-extension-

12. Acknowledgments

   The authors would like to thank George Swallow, Xia Chen, Jeff
   Tantsura,Scharf Michael,Daniele Ceccarelli and Dhruv Dhody for their
   valuable comments and suggestions.

   The authors would also like to thank Lou Berger, Adrian Farrel,
   Vishnu Pavan Beeram, Deborah Brungard and King Daniel for their
   suggestions to put forward this draft.

Authors' Addresses

   Aijun Wang
   China Telecom
   Beiqijia Town, Changping District

   Email: wangaj.bri@chinatelecom.cn

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   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

   Penghui Mi
   Tencent Building, Kejizhongyi Avenue,
   Hi-techPark, Nanshan District,Shenzhen 518057, P.R.China

   Email kevinmi@tencent.com

   Raghavendra Mallya
   Juniper Networks
   1133 Innovation Way
   Sunnyvale, California 94089 USA

   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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