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Versions: (draft-wang-teas-pce-native-ip) 00 01 02 03 04 05 10

TEAS Working Group                                               A. Wang
Internet-Draft                                             China Telecom
Intended status: Experimental                                B. Khasanov
Expires: February 11, 2021                           Huawei Technologies
                                                                 Q. Zhao
                                                        Etheric Networks
                                                                 H. Chen
                                                               Futurewei
                                                         August 10, 2020


                        PCE in Native IP Network
                    draft-ietf-teas-pce-native-ip-10

Abstract

   This document defines the architecture for traffic engineering within
   native IP network, using multiple BGP sessions strategy and PCE
   -based central control mechanism.  It uses the Central Control
   Dynamic Routing (CCDR) procedures described in this document, and the
   Path Computation Element Communication Protocol (PCEP) extension
   specified in draft ietf-pce-pcep-extension-native-ip.

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
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at https://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
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   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on February 11, 2021.

Copyright Notice

   Copyright (c) 2020 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
   to this document.  Code Components extracted from this document must
   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.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  CCDR Architecture in Simple Topology  . . . . . . . . . . . .   4
   4.  CCDR Architecture in Large Scale Topology . . . . . . . . . .   5
   5.  CCDR Multiple BGP Sessions Strategy . . . . . . . . . . . . .   6
   6.  PCEP Extension for Key Parameters Delivery  . . . . . . . . .   8
   7.  Deployment Consideration  . . . . . . . . . . . . . . . . . .   9
     7.1.  Scalability . . . . . . . . . . . . . . . . . . . . . . .   9
     7.2.  High Availability . . . . . . . . . . . . . . . . . . . .   9
     7.3.  Incremental deployment  . . . . . . . . . . . . . . . . .  10
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .  10
   9.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  10
   10. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . .  11
   11. References  . . . . . . . . . . . . . . . . . . . . . . . . .  11
     11.1.  Normative References . . . . . . . . . . . . . . . . . .  11
     11.2.  Informative References . . . . . . . . . . . . . . . . .  12
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  12

1.  Introduction

   [RFC8735] describes the scenarios and simulation results for traffic
   engineering in the native IP network to provide End-to-End (E2E)
   performance assurance and QoS using PCE based centralized control,
   referred to as Centralized Control Dynamic Routing (CCDR).  Based on
   the various scenarios and analysis as per [RFC8735], the solution for
   traffic engineering in native IP network should meet the following
   criteria:

   o  Same solution for native IPv4 and IPv6 traffic.

   o  Support for intra-domain and inter-domain scenarios.

   o  Achieve End to End traffic assurance, with determined QoS
      behavior.

   o  No upgrade to forwarding behaviour of the router.

   o  Capable to exploit the power of centrally control and the
      flexibility/robustness of distributed control protocol.



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

   o  Adjust the optimal path dynamically upon the change of network
      status.  No physical links resources reservation in advance.

   Stateful PCE [RFC8231] specifies a set of extensions to PCEP to
   enable stateful control of paths such as MPLS-TE Label Switched
   Paths(LSP)s between and across PCEP sessions in compliance with
   [RFC4657].  It includes mechanisms to achieve state synchronization
   between Path Computation Clients(PCCs) and PCEs, delegation of
   control of LSPs to PCEs, and PCE control of timing and sequence of
   path computations within and across PCEP sessions.  Furthermore,
   [RFC8281] specifies a mechanism to dynamically instantiate LSPs on a
   PCC based on the requests from a stateful PCE or a controller using
   stateful PCE.  [RFC8283] introduces the architecture for PCE as a
   central controller as an extension of the architecture described in
   [RFC4655] and assumes the continued use of PCEP as the protocol used
   between PCE and PCC.[RFC8283] further examines the motivations and
   applicability for PCEP as a Southbound Interface (SBI), and
   introduces the implications for the protocol.

   This document defines the framework for traffic engineering within
   native IP network, using multiple BGP session strategy, to meet the
   above criteria in dynamical and centrally control mode.  The
   framework is referred as CCDR framework.  It depends on the central
   control (PCE) element to compute the optimal path for selected
   traffic, and utilizes the dynamic routing behavior of traditional
   IGP/BGP protocols to forward such traffic.

   The control messages between PCE and underlying network node are
   transmitted via Path Computation Element Communications Protocol
   (PCEP) protocol.  The related PCEP extensions are provided in draft
   [I-D.ietf-pce-pcep-extension-native-ip].

2.  Terminology

   This document uses the following terms defined in [RFC5440]:

   o  PCE

   o  PCEP

   o  PCC

   The following terms are used in this document:

   o  CCDR: Central Control Dynamic Routing



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   o  E2E: End to End

   o  ECMP: Equal-Cost Multipath

   o  RR: Route Reflector

   o  SDN: Software Defined Network

3.  CCDR Architecture in Simple Topology

   Figure 1 illustrates the CCDR architecture for traffic engineering in
   simple topology.  The topology is comprised by four devices which are
   SW1, SW2, R1, R2.  There are multiple physical links between R1 and
   R2.  Traffic between prefix PF11(on SW1) and prefix PF21(on SW2) is
   normal traffic, traffic between prefix PF12(on SW1) and prefix
   PF22(on SW2) is priority traffic that should be treated with
   priority.

   In Intra-AS scenario, IGP and BGP are deployed between R1 and R2.  In
   inter-AS scenario, only native BGP protocol is deployed.  The traffic
   between each address pair may change in real time and the
   corresponding source/destination addresses of the traffic may also
   change dynamically.

   The key ideas of the CCDR framework for this simple topology are the
   followings:

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

   o  Send different prefixes via the established BGP sessions.  For
      example, PF11/PF21 via the BGP session 1 and PF12/PF22 via the BGP
      session 2.

   o  Set the explicit peer route on R1 and R2 respectively for BGP next
      hop to different physical link addresses between R1 and R2.  Such
      explicit peer route can be set in the format of static route to
      BGP peer address, which is different from the route learned from
      the IGP protocol.

   After the above actions, the bi-direction traffic between the PF11
   and PF21, and the bi-direction traffic between PF12 and PF22 will go
   through different physical links between R1 and R2, each set of
   traffic pass through different dedicated physical links.

   If there is more traffic between PF12 and PF22 that needs to be
   assured , one can add more physical links between R1 and R2 to reach




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   the the next hop for BGP session 2.  In this cases the prefixes that
   advertised by the BGP peers need not be changed.

   If, for example, there is bi-direction traffic from another address
   pair that needs to be assured (for example prefix PF13/PF23), and the
   total volume of assured traffic does not exceed the capacity of the
   previously provisioned physical links, one need only to advertise the
   newly added source/destination prefixes via the BGP session 2.  The
   bi-direction traffic between PF13/PF23 will go through the assigned
   dedicated physical links as the traffic between PF12/PF22.

   Such decouple philosophy gives network operator flexible control
   capability on the network traffic, achieve the determined QoS
   assurance effect to meet the application's requirement.  The router
   needs only support native IP and multiple BGP sessions setup via
   different loopback addresses.

                               +-----+
                    +----------+ PCE +--------+
                    |          +-----+        |
                    |                         |
                    | BGP Session 1(lo11/lo21)|
                    +-------------------------+
                    |                         |
                    | BGP Session 2(lo12/lo22)|
                    +-------------------------+
PF12                |                         |                    PF22
PF11                |                         |                    PF21
+---+         +-----+-----+             +-----+-----+              +---+
|SW1+---------+(lo11/lo12)+-------------+(lo21/lo22)+--------------+SW2|
+---+         |    R1     +-------------+    R2     |              +---+
              +-----------+             +-----------+

           Figure 1: CCDR framework in simple topology

4.  CCDR Architecture in Large Scale Topology

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

   For such scenario, we should consider using the Route Reflector (RR)
   [RFC4456] to achieve the similar effect.  Every edge router will
   establish two BGP sessions with the RR via different loopback
   addresses respectively.  The other steps for traffic differentiation
   are same as that described in the CCDR framework for simple topology.





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   As shown in Figure 2, if we select R3 as the RR, every edge router(R1
   and R7 in this example) will build two BGP session with the RR.  If
   the PCE selects the dedicated path as R1-R2-R4-R7, then the operator
   should set the explicit peer routes via PCEP protocol 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 selected forwarding address.

                                +-----+
               +----------------+ PCE +------------------+
               |                +--+--+                  |
               |                   |                     |
               |                   |                     |
               |                  ++-+                   |
               +------------------+R3+-------------------+
  PF12         |                  +--+                   |          PF22
  PF11         |                                         |          PF21
  +---+       ++-+          +--+          +--+         +-++        +---+
  |SW1+-------+R1+----------+R5+----------+R6+---------+R7+--------+SW2|
  +---+       ++-+          +--+          +--+         +-++        +---+
               |                                         |
               |                                         |
               |            +--+          +--+           |
               +------------+R2+----------+R4+-----------+
                            +--+          +--+
            Figure 2: CCDR framework in large scale network

5.  CCDR Multiple BGP Sessions Strategy

   In general situation, different applications may require different
   QoS criteria, which may include:

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

   o  Traffic that requires low packet loss and can endure higher
      latency.

   o  Traffic that requires low jitter.

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









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      +----------------+-------------+---------------+-----------------+
      | Prefix Set 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 Prefix Set No.1, we can select the shortest distance path to
   carry the traffic; for Prefix Set No.2, we can select the path that
   is comprised by under loading links from end to end; For Prefix Set
   No.3, we can let all assured traffic pass the determined single path,
   no Equal Cost Multipath (ECMP) distribution on the parallel links is
   desired.

   It is almost impossible to provide an End-to-End (E2E) path
   efficiently 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
   with the assistance of PCE, as that described in [RFC4655] and
   [RFC8283] because 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 various
   network performance requirements of different traffics.

   The framework to implement the CCDR Multiple BGP sessions strategy
   are the followings.  Here PCE is the main component of the Software
   Definition Network (SDN) controller and is responsible for optimal
   path computation for priority traffic.

   o  SDN controller gets topology via BGP-LS[RFC7752] and link
      utilization information via existing Network Monitor System (NMS)
      from the underlying network.

   o  PCE calculates the appropriate path upon application's
      requirements, sends the key parameters to edge/RR routers(R1, R7
      and R3 in Fig.3) to establish multiple BGP sessions and advertises
      different prefixes via them.  The loopback addresses used for BGP
      sessions should be planned in advance and distributed in the
      domain.

   o  PCE sends the route information to the routers (R1,R2,R4,R7 in
      Fig.3) on forwarding path via PCEP
      [I-D.ietf-pce-pcep-extension-native-ip], to build the path to the
      BGP next-hop of the advertised prefixes.



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   o  If the assured traffic prefixes were changed but the total volume
      of assured traffic does not exceed the physical capacity of the
      previous E2E path, PCE needs only change the prefixed advertised
      via the edge routers (R1,R7 in Fig.3).

   o  If the volume of assured traffic exceeds the capacity of previous
      calculated path, PCE can recalculate and add the appropriate paths
      to accommodate the exceeding traffic.  After that, PCE needs to
      update on-path routers to build the forwarding path hop by hop.

                            +------------+
                            | Application|
                            +------+-----+
                                   |
                          +--------+---------+
               +----------+SDN Controller/PCE+-----------+
               |          +--------^---------+           |
               |                   |                     |
               |                   |                     |
          PCEP |             BGP-LS|PCEP                 | PCEP
               |                   |                     |
               |                  +v-+                   |
               +------------------+R3+-------------------+
   PF12        |                  +--+                   |          PF22
   PF11        |                                         |          PF21
  +---+       +v-+          +--+          +--+         +-v+        +---+
  |SW1+-------+R1+----------+R5+----------+R6+---------+R7+--------+SW2|
  +---+       ++-+          +--+          +--+         +-++        +---+
               |                                         |
               |                                         |
               |            +--+          +--+           |
               +------------+R2+----------+R4+-----------+

             Figure 3: CCDR framework for Multi-BGP deployment

6.  PCEP Extension for Key Parameters Delivery

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

   o  Peer addresses pair that is used to build the BGP session

   o  Advertised prefixes and their associated BGP session.

   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



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   the prefixes that contained in the corresponding PCEP message, and
   build the end to end dedicated path hop by hop.

   The dedicated path is preferred by making sure that the explicit
   route created by PCE has the higher priority (lower route preference)
   than the route information created by any other protocols (including
   the route manually configured).

   All above dynamically created states (BGP sessions, Prefix advertised
   prefix, Explicit route) will be cleared on the expiration of state
   timeout interval which is based on the existing Stateful PCE
   [RFC8231] and PCECC [RFC8283] mechanism.

   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] .

7.  Deployment Consideration

7.1.  Scalability

   In CCDR framework, PCE needs only influence the edge routers for the
   prefixes advertisement via the multiple BGP sessions deployment.  The
   route information for these prefixes within the on-path routers were
   distributed via the BGP protocol.

   For multiple domains deployment, the PCE or the pool of PCEs that
   reponsible for these domains need only control the edge router to
   build multiple EBGP sessions, all other procedures are the same that
   in one domain.

   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 expandability when
   comparing with the solution from BGP flowspec or Openflow.  For
   example, if we want to differentiate 1000 prefixes from the normal
   traffic, CCDR needs only one explicit peer route in every on-path
   router, but the BGP flowspec or Openflow needs 1000 policy routes on
   them.

7.2.  High Availability

   The 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 unchanged.



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   If one node on the optimal path is failed, the priority traffic will
   fall over to the best-effort forwarding path.  One can even design
   several assurance paths to load balance/hot-standby the priority
   traffic to meet the path failure situation.

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

7.3.  Incremental deployment

   Not every router within the network 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.

8.  Security Considerations

   A PCE needs to assure calculation of E2E path based on the status of
   network and the service requirements in real-time.

   The PCE need consider the explicit route deployment order (for
   example, from tail router to head router) to eliminate the possible
   transient traffic loop.

   The setup of BGP session, prefix advertisement and explicit peer
   route establishment are all controlled by the PCE.  To prevent the
   bogus PCE to send harmful messages to the network nodes, the network
   devices should authenticate the validity of PCE and keep secures
   communication channel between them.  Mechanism described in [RFC8253]
   should be used to avoid such situation.

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

9.  IANA Considerations

   This document does not require any IANA actions.







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10.  Acknowledgement

   The author would like to thank Deborah Brungard, Adrian Farrel,
   Vishnu Beeram, Lou Berger, Dhruv Dhody, Raghavendra Mallya , Mike
   Koldychev, Haomian Zheng, Penghui Mi, Shaofu Peng and Jessica Chen
   for their supports and comments on this draft.

11.  References

11.1.  Normative References

   [RFC4456]  Bates, T., Chen, E., and R. Chandra, "BGP Route
              Reflection: An Alternative to Full Mesh Internal BGP
              (IBGP)", RFC 4456, DOI 10.17487/RFC4456, April 2006,
              <https://www.rfc-editor.org/info/rfc4456>.

   [RFC4655]  Farrel, A., Vasseur, J., and J. Ash, "A Path Computation
              Element (PCE)-Based Architecture", RFC 4655,
              DOI 10.17487/RFC4655, August 2006,
              <https://www.rfc-editor.org/info/rfc4655>.

   [RFC4657]  Ash, J., Ed. and J. Le Roux, Ed., "Path Computation
              Element (PCE) Communication Protocol Generic
              Requirements", RFC 4657, DOI 10.17487/RFC4657, September
              2006, <https://www.rfc-editor.org/info/rfc4657>.

   [RFC5440]  Vasseur, JP., Ed. and JL. Le Roux, Ed., "Path Computation
              Element (PCE) Communication Protocol (PCEP)", RFC 5440,
              DOI 10.17487/RFC5440, March 2009,
              <https://www.rfc-editor.org/info/rfc5440>.

   [RFC7752]  Gredler, H., Ed., Medved, J., Previdi, S., Farrel, A., and
              S. Ray, "North-Bound Distribution of Link-State and
              Traffic Engineering (TE) Information Using BGP", RFC 7752,
              DOI 10.17487/RFC7752, March 2016,
              <https://www.rfc-editor.org/info/rfc7752>.

   [RFC8231]  Crabbe, E., Minei, I., Medved, J., and R. Varga, "Path
              Computation Element Communication Protocol (PCEP)
              Extensions for Stateful PCE", RFC 8231,
              DOI 10.17487/RFC8231, September 2017,
              <https://www.rfc-editor.org/info/rfc8231>.

   [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,
              <https://www.rfc-editor.org/info/rfc8253>.



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   [RFC8281]  Crabbe, E., Minei, I., Sivabalan, S., and R. Varga, "Path
              Computation Element Communication Protocol (PCEP)
              Extensions for PCE-Initiated LSP Setup in a Stateful PCE
              Model", RFC 8281, DOI 10.17487/RFC8281, December 2017,
              <https://www.rfc-editor.org/info/rfc8281>.

   [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,
              <https://www.rfc-editor.org/info/rfc8283>.

   [RFC8735]  Wang, A., Huang, X., Kou, C., Li, Z., and P. Mi,
              "Scenarios and Simulation Results of PCE in a Native IP
              Network", RFC 8735, DOI 10.17487/RFC8735, February 2020,
              <https://www.rfc-editor.org/info/rfc8735>.

11.2.  Informative References

   [I-D.ietf-pce-pcep-extension-native-ip]
              Wang, A., Khasanov, B., Fang, S., and C. Zhu, "PCEP
              Extension for Native IP Network", draft-ietf-pce-pcep-
              extension-native-ip-05 (work in progress), February 2020.

Authors' Addresses

   Aijun Wang
   China Telecom
   Beiqijia Town, Changping District
   Beijing  102209
   China

   Email: wangaj3@chinatelecom.cn


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

   Email: khasanov.boris@huawei.com









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   Quintin Zhao
   Etheric Networks
   1009 S CLAREMONT ST
   SAN MATEO, CA  94402
   USA

   Email: qzhao@ethericnetworks.com


   Huaimo Chen
   Futurewei
   Boston, MA
   USA

   Email: huaimo.chen@futurewei.com




































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