TEAS Working Group                                             A.Wang
Internet Draft                                           China Telecom
                                                           Quintin Zhao
                                                         Boris Khasanov
                                                    Huawei Technologies
                                                               Kevin Mi
                                                        Tencent Company
                                                     Raghavendra Mallya
                                                       Juniper Networks
                                                            Shaofu Peng
                                                        ZTE Corporation
Intended status: Standard Track                            March 6, 2017
Expires: September 5, 2017

                         PCE in Native IP Network

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   This document defines the scenario and solution for traffic
   engineering within Native IP network, using Dual/Multi-BGP session
   strategy and PCE-based central control architecture. The proposed
   central mode control solution conforms to the concept that defined
   in draft [I-D.draft-ietf-teas-pce-control-function]. And together
   with draft [I-D.draft-ietf-teas-pcecc-use-cases], the solution
   portfolio for traffic engineering in MPLS and Native IP network is
   almost completed.

Table of Contents

   1. Introduction ................................................ 3
   2. Conventions used in this document............................ 3
   3. Dual-BGP solution for simple topology........................ 3
   4. Dual-BGP in large Scale Topology............................. 5
   5. Multi-BGP for Extended Traffic Differentiation ...............6
   6. PCE based solution for Multi-BGP strategy deployment......... 6
   7. PCEP extension for key parameters delivery. .................. 8
   8. Deployment Consideration ..................................... 8
   9. Security Considerations...................................... 9
   10. IANA Considerations......................................... 9
   11. Conclusions ............................................... 10
   12. References ................................................ 10
      12.1. Normative References.................................. 10
      12.2. Informative References................................ 10
   13. Acknowledgments ........................................... 11

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1. Introduction

   Currently, PCE based traffic assurance requires the underlying
   network devices support MPLS and the network must deploy multiple
   LSPs to assure the end-to-end traffic performance. LDP/RSVP-TE or
   Segment Routing should be enabled within the network to establish
   various MPLS paths. Such solution will certainly work but they does
   not cover the needs in legacy Native IP network, which demands less
   signaling protocol and less complex traffic steering policy.

   Within Native IP network, the solution for traffic engineering is
   generally hop-by-hop differentiate treatment. To achieve the end2end
   QoS performance assurance, one can only deploy some dedicated links
   statically, but such solution is not feasible in the service provider
   network, because the complexity of underlying network and the
   variation of application traffic from time to time.

   In summary, the requirements for traffic engineering in Native IP
   network are the following:
   1) No complex MPLS signaling procedure.
   2) End to End traffic assurance, determined QoS behavior.
   3) Flexible deployment and automation control.

   This document defines the solution for traffic engineering within
   Native IP network, using Dual/Multi-BGP session strategy and PCE-
   based central control 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-

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 solution for simple topology.

   This section introduces the dual-BGP solution for simple topology
   that illustrated in Fig.1, which is comprised by SW1, SW2, R1, R2.
   There are multiple physical links between R1 and R2. Let's assume
   traffic between IP11 and IP21 is normal traffic, traffic between IP12

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   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 solution for this simple topology is the
    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 IP12, and the traffic between
   IP21 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 IP13 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.

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

              Fig.1 Design Philosophy for Dual-BGP Solution

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 neighbor by neighbor 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, that is to say, select
   one router which performs the role of RR (for example R3 in Fig.2 -
   Dual-BGP Solution using Route Reflector for large scale network),
   every other router will establish two BGP 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

                     |                            |
                     |        |          |        |

             Fig.2 Dual-BGP solution for large scale network

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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 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 PCE-based 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. PCE based solution for Multi-BGP strategy deployment.

   With the advent of SDN concepts towards pure IP networks, it is
   possible to deploy the PCE related technology into the underlying

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   native IP network, 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
                     *             *              *
                     *             *           \  * /
                   \ * /           *            \ */
                     |                            |
                     |                            |
                     |        |          |        |
                     |        |          |        |

            Fig.3 PCE based solution for Multi-BGP deployment

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7. PCEP extension for key parameters delivery.

   We need to extend the PCEP protocol 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 very 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

   This solution 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 current solution, only the edge router of the end2end path needs
   to keep the detail prefixes of the assured traffic, other on-path
   routers need only keep explicit peer routes to the edge routers.

   The key scalability factor is the number of BGP sessions as on
   ingress/egress routers as on RRs. Similarly with L3VPN solution, it
   has very high scalability to deploy in real network.

8.2 High Availability

   Current solution is based on the traditional distributed IP protocol,
   then if the central control PCE failed, the assurance traffic will

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   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.

8.4 Deployment within Pure IGP network

   For some small underlying networks that the routers support only the
   pure IGP protocol, we can use similar procedures that described
   within this draft to differentiate the forwarding paths for different

   1) Define different loopback addresses on the IGP edge router(ASBR).

   2) Redistribute external prefixes into IGP at ASBR, use route tag to
      label these prefixes at the ASBR.

   3) Use route policy to set the explicit peer routes for the tagged
      prefixes on every on-path routers to the different loopback
      addresses on ASBR.

   The detail of deployment scenario and the corresponding PCEP
   extension will be exploited further later.

9. Security Considerations


10. IANA Considerations


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11. Conclusions


12. References

12.1. Normative References

   [RFC4655] Farrel, A., Vasseur, J.-P., and J. Ash, "A Path

             Computation Element (PCE)-Based Architecture", RFC

             4655, August 2006,<http://www.rfc-editor.org/info/rfc4655>.

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

             Computation Element (PCE) Communication Protocol

             (PCEP)", RFC 5440, March 2009,


12.2. Informative References


   A.Farrel, Q.Zhao et al. "An Architecture for use of PCE and PCEP in
      a Network with Central Control"

   control/  September, 2016

   [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-

13. Acknowledgments

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

   The authors would also like to thank Lou Berger, Adrian Farrel, 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

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

   EMail: quintin.zhao@huawei.com

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

   EMail: khasanov.boris@huawei.com

   Kevin Mi
   Tencent Company
   Tencent Building, Kejizhongyi Avenue,
   Hi-techPark,Nanshan District,Shenzhen

   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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