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bess                                                            Z. Zhang
Internet-Draft                                          Juniper Networks
Intended status: Standards Track                               R. Parekh
Expires: May 7, 2020                                       Cisco Systems
                                                                Z. Zhang
                                                        November 4, 2019

              MVPN and EVPN BUM Signaling with Controllers


   This document specifies optional procedures for BGP-MVPN and EVPN BUM
   signaling with controllers.  When P2MP tunnels used for BGP-MVPN and
   EVPN BUM are to be signaled from controllers, the controllers can
   learn tunnel information (identifier, root, leaf) by participating
   BGP-MVPN and EVPN BUM signaling, instead of relying on ingress PEs to
   collect the information and then pass to the controllers.
   Additionally, Inclusive/Selective PMSI Auto Discovery Routes can be
   originated from controllers based on central provisioning, instead of
   from PEs based on local provisioning.

Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "OPTIONAL" in this document are to be interpreted as described in BCP
   14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

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."

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   This Internet-Draft will expire on May 7, 2020.

Copyright Notice

   Copyright (c) 2019 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
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   described in the Simplified BSD License.

Table of Contents

   1.  Terminologies . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Specification . . . . . . . . . . . . . . . . . . . . . . . .   4
     3.1.  Controller Address Extended Community . . . . . . . . . .   4
     3.2.  Targeting Leaf A-D Routes to Controllers  . . . . . . . .   4
     3.3.  Controller Originated I/S-PMSI Routes . . . . . . . . . .   5
       3.3.1.  Inter-AS/Region Segmentation  . . . . . . . . . . . .   5
     3.4.  Automatic DCB Label Allocation by Controllers . . . . . .   6
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .   6
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
   6.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   7
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   7
     7.1.  Normative References  . . . . . . . . . . . . . . . . . .   7
     7.2.  Informative References  . . . . . . . . . . . . . . . . .   7
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   8

1.  Terminologies

   Familiarity with MVPN/EVPN protocols and procedures is assumed.  Some
   terminologies are listed below for convenience.

   o  PMSI: P-Multicast Service Interface - a conceptual interface for a
      PE to send customer multicast traffic to all or some PEs in the
      same VPN/BD.

   o  I-PMSI: Inclusive PMSI - to all PEs in the same VPN/BD.

   o  S-PMSI: Selective PMSI - to some of the PEs in the same VPN/BD.

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   o  Leaf A-D routes: For explicit leaf tracking purpose.  Triggered by
      S-PMSI A-D routes and targeted at triggering route's originator.

   o  IMET A-D route: Inclusive Multicast Ethernet Tag A-D route.  The
      EVPN equivalent of MVPN Intra-AS I-PMSI A-D route.

   As pointed out above, the EVPN IMET route is the equivalent of MVPN
   I-PMSI A-D route.  In the rest of the document, unless explicitly
   stated, I-PMSI A-D route refers to MVPN Intra-AS I-PMSI A-D route
   and/or EVPN IMET route.

2.  Introduction

   Consider a provider network with BGP-MVPN/EVPN where controllers are
   used to set up P2MP tunnels per [draft-zzhang-bess-bgp-multicast-
   controller] or [draft-voyer-pim-sr-p2mp-policy].  For a controller to
   calculate the corresponding trees and set up the tunnels, it needs to
   learn the (ID, root, leaf) information for those trees.  Currently,
   [draft-parekh-bess-mvpn-sr-p2mp] specifies that an ingress PE assigns
   the SR P2MP ID and collects leaf information via Leaf A-D routes, and
   then pass onto the controller.  Observing that BGP-MVPN/EVPN
   signaling typically involves Router Reflectors, which may typically
   be hosted on or co-located with controllers, it makes sense to have
   the controllers participating BGP-MVPN/EVPN signaling to learn (ID,
   root, leaf) information.  This will relieve the PEs from maintaining
   Leaf A-D routes, and remove the extra hop of leaf information

   Also Consider that in the same network many selective tunnels are
   used, and their usages are dynamically provisioned based on specific
   needs at different time.  For example, the provider provides video
   transmission services for events at various time, location and to
   various receivers.  With traditional methods the provider would
   provision the PEs at the transmission sources with various selective
   tunnels, which triggers corresponding S-PMSI A-D routes.  The
   provisioning is put in place shortly before an event takes place and
   removed shortly after the event ends.  Alternatively and preferrably,
   a controller can originate S-PMSI A-D routes based on centralized
   provisioning on behalf of the source PEs.  The controller also
   collects the leaf information (either based on centralized
   provisioning or based on Leaf A-D routes), calculates the tree and
   signal tree nodes.  Additionally, when tunnel aggregation labels are
   allocated from Domain-wide Common Block (DCB), originating I/S-PMSI
   A-D routes from controllers makes the DCB label allocation a lot

   It is possible that an operator prefers automatic DCB aggregation
   label allocation by the controller but prefers I/S-PMSI A-D routes

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   origination from individual PEs.  In that case, a PE can target an I/
   S-PMSI A-D route at the controller and the controller will allocate a
   DCB label and return it in a corresponding Leaf A-D route.

3.  Specification

   The procedures specified in this section applies if one or more
   controllers participate MVPN/EVPN signaling for the purpose of leaf
   discovery for P2MP tree calculation, and/or if controllers are to
   originate I/S-PMSI A-D routes or BGP-MVPN and/or BGP-EVPN BUM.

3.1.  Controller Address Extended Community

   This document defines a new Transitive IPv4-Address-Specific Extended
   Community Sub-Type: "Controller Address".  This document also defines
   a new BGP Transitive IPv6-Address-Specific Extended Community Sub-
   Type: "Controller Address".

   A Controller Address Extended Community (referred to as Controller
   EC) is constructed by setting the Global Administrator field to the
   IP address of the controller and the Local Administrator field to 0.

3.2.  Targeting Leaf A-D Routes to Controllers

   When a PE originates an I/S-PMSI A-D route with PTA's tunnel type set
   to PIM-SSM/ASM, mLDP or SR P2MP that are to be set up by controllers,
   the PE MUST attach a Controller EC constructed as above.  If there
   are multiple controllers, then one Controller EC is attached for each
   of the controllers.

   In case of tunnel segmentation and a new controller is used for the
   next segmentation region, when an ABR/ASBR/RBR re-advertises the I/
   S-PMSI A-D route to the next segmentation region it MUST modify the
   Controller EC to specify the new controller address.

   When a PE/ABR/ASBR/RBR receives an I/S-PMSI A-D route with the
   Controller EC, it MUST originate a corresponding Leaf A-D route.  The
   PTA from the I/S-PMSI A-D route is copied to the Leaf A-D route, and
   an IP Address Specific Route Target to attached to the Leaf A-D
   route.  The Global Administrator field of the RT is set to the
   address of the controller (as encoded in the received Controller EC),
   and the Local Administrator field is set to 0.

   Note that, the above is done even if the Leaf Information Required
   (LIR) bit in the Flags field of the I/S-PMSI A-D route's PMSI Tunnel
   Attribute (PTA) is not set.  If the LIR bit in the Flags field of the
   I/S-PMSI A-D route's PTA is set, then the above mentioned RTs are in
   addition to the RT that the PE attaches according to the procedures

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   in [RFC6514], [RFC7524], or [draft-zzhang-bess-evpn-bum-procedure-
   updates].  In other words, the Leaf A-D route will have RTs for both
   the controllers and the upstream PE or segmentation points.

   When a controller receives the advertisement and/or withdrawl of Leaf
   A-D routes, it derives the set of leaves for the tunnel identified in
   the PTA, calculate and set up the tree according to procedurs in
   [draft-zzhang-bess-bgp-multicast-controller] or [draft-voyer-pim-sr-
   p2mp-policy].  The controller does not further propagate the received
   advertisement and/or withdrawl, unless there are other RTs attached.

3.3.  Controller Originated I/S-PMSI Routes

   When I/S-PMSI A-D routes are to be originated from the controllers,
   it is expected that the controller, based on central planning, has
   the knowledge of each VPN/BD's Route Target, each PE's RD for the
   VPN/BD, and the Tunnel Type and Identifier for each I/S-PMSI.  If the
   tunnel aggregation is used, the controllers also allocate labels from
   the DCB for the I/S-PMSIs.

   The controller constructs the I/S-PMSI A-D route the same way as if
   an ingress PE would be originating the routes.  There are some
   exceptions in case inter-AS/region segmentation is used, as specified
   in Section 3.3.1.

   Specifically, the controller uses the ingress PE's RD and RTs for the
   VPN/BD, and use the ingress PE's address as "Originating Router's IP
   Address" when constructing the I/S-PMSI A-D routes.  The routes are
   sent with the controller's address as next-hop initially, though the
   next-hop may change as the routes propagates.

   When the Ingress PE router receives the I/S-PMSI A-D routes, it sets
   up corresponding forwarding state as if it originated the routes per
   its local provisioning.  Note that the next-hop address of the routes
   will be different from the case where the ingress PE originates the
   routes, but this should not matter.

3.3.1.  Inter-AS/Region Segmentation

   In case of segmentation, instead of using the Route Target for the
   VPN/BD, the controller constructs an IP Address specific Route Target
   with the Global Administrator Field set to the corresponding ingress
   PE's address and the Local Administrator Field set to 0.  This
   targets the I/S-PMSI A-D routes to the Ingress PEs only.

   The controller also sets the Originating Router's IP Address field of
   the I/S-PMSI A-D route to its own address.

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   The receiving Ingress PE associate the I/S-PMSI A-D route to the
   corresponding VRF/BD based on the RD of the received route.  It then
   re-originate a corresponding I/S-PMSI A-D route based on the received
   I/S-PMSI A-D route from the controller by doing the following:

   o  Changing the Originating Router's IP address to its own

   o  Replacing the Route Target with the Route Target for the VPN/BD

3.4.  Automatic DCB Label Allocation by Controllers

   If it is desired for a PE to originate I/S-PMSI A-D routes on its own
   but with DCB labels dynamically allcated by a controller, the PE
   originates the I/S-PMSI A-D route with the Tunnel Type in the PTA set
   to "no tunnel information present", the LIR bit in the PTA'S Flags
   field set to 1, and attaches an IP Address Specific RT.  The RT's
   Global Administrator Field is set to the Controller's address and
   Local Administrator field is set to 0.

   When the controller receives the I/S-PMSI A-D route, it allocates a
   DCB label and responds with a Leaf A-D route.  The Label field of the
   Leaf A-D route's PTA is set to the allocated DCB label.

   When the PE receives the Leaf A-D route, it re-advertises the I/
   S-PMSI A-D route, with an additional RT for the corresponding VPN/BD.
   The PTA's tunnel information is set as needed and the Label field is
   set to the DCB label received in the Leaf A-D route.  The LIR bit in
   the Flags field of the PTA is set to 1 or 0 as needed.  If it is set
   to 0, the controller withdraws the Leaf A-D route but does not
   release the allocated label.

   When the PE withdraws the I/S-PMSI A-D route, the controller release
   the DCB label and withdraws the corresponding Leaf A-D route if it
   had not been withdrawn before.

4.  Security Considerations

   This document does not change security aspects as discussed in
   [RFC4360], [6514], [7432], and [ietf-bess-evpn-bum-procedure-

5.  IANA Considerations

   To be added.

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6.  Acknowledgements

7.  References

7.1.  Normative References

              Zhang, Z., Lin, W., Rabadan, J., Patel, K., and A.
              Sajassi, "Updates on EVPN BUM Procedures", draft-ietf-
              bess-evpn-bum-procedure-updates-07 (work in progress),
              August 2019.

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

   [RFC6514]  Aggarwal, R., Rosen, E., Morin, T., and Y. Rekhter, "BGP
              Encodings and Procedures for Multicast in MPLS/BGP IP
              VPNs", RFC 6514, DOI 10.17487/RFC6514, February 2012,

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

7.2.  Informative References

              Zhang, Z., Rosen, E., Lin, W., Li, Z., and I. Wijnands,
              "MVPN/EVPN Tunnel Aggregation with Common Labels", draft-
              ietf-bess-mvpn-evpn-aggregation-label-03 (work in
              progress), October 2019.

              Parekh, R., Filsfils, C., Venkateswaran, A., Bidgoli, H.,
              daniel.voyer@bell.ca, d., and C. Hassen, "Multicast VPN
              with Segment Routing Point-to-Multipoint Segment", draft-
              parekh-bess-mvpn-sr-p2mp-00 (work in progress), March

              daniel.voyer@bell.ca, d., Filsfils, C., Parekh, R.,
              Bidgoli, H., and Z. Zhang, "Segment Routing Point-to-
              Multipoint Policy", draft-voyer-pim-sr-p2mp-policy-00
              (work in progress), October 2019.

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              Zhang, Z., Raszuk, R., Pacella, D., and A. Gulko,
              "Controller Based BGP Multicast Signaling", draft-zzhang-
              bess-bgp-multicast-controller-01 (work in progress),
              February 2019.

   [RFC7524]  Rekhter, Y., Rosen, E., Aggarwal, R., Morin, T.,
              Grosclaude, I., Leymann, N., and S. Saad, "Inter-Area
              Point-to-Multipoint (P2MP) Segmented Label Switched Paths
              (LSPs)", RFC 7524, DOI 10.17487/RFC7524, May 2015,

Authors' Addresses

   Zhaohui Zhang
   Juniper Networks

   EMail: zzhang@juniper.net

   Rishabh Parekh
   Cisco Systems

   EMail: riparekh@cisco.com

   Zheng Zhang

   EMail: zhang.zheng@zte.com.cn

   Hooman Bidgoli

   EMail: hooman.bidgoli@nokia.com

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