TEAS Working Group A. Wang Internet-Draft China Telecom Intended status: Experimental B. Khasanov Expires: February 26, 2021 Huawei Technologies Q. Zhao Etheric Networks H. Chen Futurewei August 25, 2020 PCE in Native IP Network draft-ietf-teas-pce-native-ip-11 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 and may be updated, replaced, or obsoleted by other documents at any 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 26, 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 Wang, et al. Expires February 26, 2021 [Page 1] Internet-Draft PCE in Native IP Network August 2020 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. Wang, et al. Expires February 26, 2021 [Page 2] Internet-Draft PCE in Native IP Network August 2020 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 architecture for traffic engineering within native IP network, using multiple BGP session strategy, to meet the above criteria in dynamical and centrally control mode. The architecture is referred as CCDR architecture. 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 Wang, et al. Expires February 26, 2021 [Page 3] Internet-Draft PCE in Native IP Network August 2020 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 architecture 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 Wang, et al. Expires February 26, 2021 [Page 4] Internet-Draft PCE in Native IP Network August 2020 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 architecture 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 architecture for simple topology. Wang, et al. Expires February 26, 2021 [Page 5] Internet-Draft PCE in Native IP Network August 2020 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 architecture 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: Wang, et al. Expires February 26, 2021 [Page 6] Internet-Draft PCE in Native IP Network August 2020 +----------------+-------------+---------------+-----------------+ | 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 architecture 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. Wang, et al. Expires February 26, 2021 [Page 7] Internet-Draft PCE in Native IP Network August 2020 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 architecture 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 Wang, et al. Expires February 26, 2021 [Page 8] Internet-Draft PCE in Native IP Network August 2020 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 architecture, 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 architecture 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. Wang, et al. Expires February 26, 2021 [Page 9] Internet-Draft PCE in Native IP Network August 2020 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 needs 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 architecture 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. Wang, et al. Expires February 26, 2021 [Page 10] Internet-Draft PCE in Native IP Network August 2020 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, . [RFC4655] Farrel, A., Vasseur, J., and J. Ash, "A Path Computation Element (PCE)-Based Architecture", RFC 4655, DOI 10.17487/RFC4655, August 2006, . [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, . [RFC5440] Vasseur, JP., Ed. and JL. Le Roux, Ed., "Path Computation Element (PCE) Communication Protocol (PCEP)", RFC 5440, DOI 10.17487/RFC5440, March 2009, . [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, . [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, . [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, . Wang, et al. Expires February 26, 2021 [Page 11] Internet-Draft PCE in Native IP Network August 2020 [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, . [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, . [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, . 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-06 (work in progress), August 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 Wang, et al. Expires February 26, 2021 [Page 12] Internet-Draft PCE in Native IP Network August 2020 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 Wang, et al. Expires February 26, 2021 [Page 13]