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Versions: (draft-dunbar-idr-bgp-sdwan-overlay-ext) 00 01 02 03 04 05

Network Working Group                                         L. Dunbar
Internet Draft                                                Futurewei
Intended status: Informational                                 S. Hares
Expires: May 4, 2020                       Hickory Hill Consulting

                                                       November 4, 2019




           SDWAN WAN Ports Property Advertisement in BGP UPDATE
                    draft-dunbar-idr-sdwan-port-safi-05

Abstract

   The document specifies information encoded in BGP UPDATE for
   advertising WAN ports properties of a SDWAN edge node to its
   controller. SDWAN edge node's WAN ports may face untrusted networks,
   such as the public internet, may get assigned IP addresses from the
   Internet Service Providers (ISPs), may get assigned dynamic IP
   addresses via DHCP, or may have private addresses (e.g. inside third
   party Cloud DCs). Packets forwarded through those SDWAN WAN ports
   might need to be encrypted (depending on the user policies) or need
   to go through NAT. SDWAN edge nodes need to propagate those WAN
   ports properties to its controller which in turn distribute to the
   peers who are authorized to communicate across different types of
   underlay networks including the untrusted networks.

   This document assumes the BGP Route Reflectors (RR) as the
   controller, i.e. SDWAN edges send the WAN ports properties encoded
   in BGP UPDATE to the RR which in turns propagate the information to
   a group of authorized SDWAN edges reachable via overlay networks.

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), its areas, and its working groups.  Note that
   other groups may also distribute working documents as Internet-
   Drafts.




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   Internet-Drafts are draft documents valid for a maximum of six
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   Copyright (c) 2019 IETF Trust and the persons identified as the
   document authors. All rights reserved.

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Table of Contents


   1. Introduction...................................................3
   2. Conventions used in this document..............................3
      2.1. Information to be propagated for SDWAN UPDATE.............4
      2.2. SAFI under the MP-NLRI....................................6
      2.3. How about a new Path Attribute under BGP UPDATE?..........6
   3. SDWAN WAN Port ID encoding in the MP-NLRI Path Attribute.......6
   4. WAN Port Properties encoding in the Tunnel Path Attribute......8
      4.1. Port Ext SubTLV...........................................8
      4.2. IPsec Security Association Property......................10
      4.3. Remote Endpoint..........................................11
   5. Manageability Considerations..................................12


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   6. Security Considerations.......................................12
   7. IANA Considerations...........................................12
   8. References....................................................12
      8.1. Normative References.....................................12
      8.2. Informative References...................................12
   9. Acknowledgments...............................................13

1. Introduction

   [Net2Cloud-Problem] introduces using SDWAN to reach dynamic
   workloads in multiple third-party data centers and aggregate
   multiple underlay paths, including public untrusted networks,
   provided by different service providers.

   [SDWAN-BGP-USAGE] describes multiple SDWAN scenarios and how/why
   using BGP as control plane for the SDWAN networks. [SDWAN-BGP-USAGE]
   introduced two distinct SDWAN scenarios: Homogeneous SDWAN and
   Hybrid SDWAN.

   This document describes multiple options of encoding under the
   Hybrid SDWAN scenario for SDWAN edge nodes to propagate their WAN
   Ports properties to their peer SDWAN nodes.


2. Conventions used in this document

   Cloud DC:   Off-Premise Data Centers that usually host applications
               and workload owned by different organizations or
               tenants.

   Controller: Used interchangeably with SDWAN controller to manage
               SDWAN overlay path creation/deletion and monitor the
               path conditions between sites.

   CPE-Based VPN: Virtual Private Secure network formed among CPEs.
               This is to differentiate from most commonly used PE-
               based VPNs a la RFC 4364.

   MP-NLRI:    The MP_REACH_NLRI Path Attribute defined in RFC4760.





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   SDWAN End-point:  An WAN port (logical or physical) of a SDWAN edge
               node.  (If "endpoint" is used, it refers to a SDWAN End-
               point).

   OnPrem:     On Premises data centers and branch offices

   SDWAN:      Software Defined Wide Area Network. In this document,
               "SDWAN" refers to the solutions of pooling WAN bandwidth
               from multiple underlay networks to get better WAN
               bandwidth management, visibility & control. When the
               underlay networks are private networks, traffic can be
               forwarded without additional encryption; when the
               underlay networks are public, such as Internet, some
               traffic needs to be encrypted when forwarding through
               those WAN ports(depending on user provided policies).


 2.1. Information to be propagated for SDWAN UPDATE

   [Tunnel-Encap] describes a BGP UPDATE Path Attribute (with Code =
   23) that advertise endpoints' tunnel encapsulation capabilities for
   the respective attached client routes, so that the receivers of the
   BGP UPDATE can establish appropriate tunnels to the endpoints for
   the aforementioned client routes. The detailed tunnel information
   encoded in the Tunnel Path Attribute apply to all client routes
   carried by the UPDATE's MP-NLRI, which refers to the MP_REACH_NLRI
   Path Attribute described in RFC4760.

   Following the same approach used by [idr-segment-routing-te-policy]
   where the SR Policy identifier is encoded in the MP-NLRI Path
   Attribute and the detailed SR Polices are encoded in the Tunnel Path
   attribute, SDWAN WAN port UPDATE can have the WAN Port Identifier
   encoded in the MP-NLRI Path Attribute and the associated WAN Port
   properties encoded in the Tunnel Path Attribute. Sometimes, a WAN
   Port identifier can be only locally significant within the SDWAN
   node. Therefore, it is necessary to include the Node ID and Site ID
   to identify a SDWAN WAN Port.

   This approach has the benefit of cleaner implementation when the
   properties of a SDWAN node's WAN Port changes, such as ISP service
   agreement changes for the service connected to a WAN Port, a WAN



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   port being disabled, or its IPsec property changes, etc.  Since most
   SDWAN edges only have a small number of WAN ports, the disadvantage
   of multiple BGP UPDATE messages to advertise properties of those WAN
   ports is relatively small.

   For example, a SDWAN edge node with 3 WAN ports (A1/A2/A3) can send
   3 separate SDWAN UPDATE messages to propagate the properties of its
   WAN Port A1, A2, and A3.

   UPDATE message for WAN Port A1:
   Border Gateway Protocol - UPDATE Message

     Path Attribute - MP_REACH_NLRI
     /* independent from the routes attached to the SDWAN node */
          - Address family identifier (AFI)
          - Subsequent address family identifier (SAFI)
          - /* New: Port Identifier, which can be assigned IPv4/Ipv6
            address, or locally significant port ID  (similar to SR policy ID)*/
          - Next hop network address
          - /* New: the SDWAN node identifier */
          - /* New: Site-ID of this SD-WAN node */

     Path Attribute - Tunnel-Encap  (Type Code=23)
     /*Detailed properties for WAN Port A1*/
          - Tunnel-Type = Untrusted-Internet  /* need IANA assignment */
          - Encoding of A1's properties in subTLVs
            /* see later section for detailed encoding */
               - Ipsec properties for Ipsec tunnel terminated at A1
               - NAT properties if A1 has private address
               - ISP information


   The SDWAN node identifier (or loopback address) might be only
   locally significant among its peer group and not routable in the
   WAN.

   Receivers of the UPDATE can associate the SDWAN node identifier,
   site identifier with the node's WAN Port properties. The SDWAN-A can
   send a regular BGP UPDATE messages to advertise the SDWAN-A node
   being the NextHop for CN3 & CN2, without attaching the WAN port
   property.



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 2.2. SAFI under the MP-NLRI

   It is possible to continue using the same IP SAFI in the MP-NLRI
   [RFC4760] Path Attribute for advertising the SDWAN WAN port
   properties. If the same IP SAFI used, receiver needs extra logic to
   differentiate regular BGP MP-NLRI routes advertisement from the
   SDWAN WAN port properties advertisement and recognize the extra Site
   ID field added to the MP-NLRI. The benefit of using the same IP SAFI
   is that the UPDATE can traverse existing routers without being
   dropped. However, the SDWAN UPDATE is only between SDWAN edge and
   the RR, all the intermediate nodes treat the UPDATE message as
   regular IP data frame.

   Alternatively, we can follow the same approach used by [idr-segment-
   routing-te-policy] to have a unique SAFI (IANA assigned SDWAN SAFI =
   74) mainly to differentiate the SDWAN UPDATE from regular route
   UPDATE or SR policy UPDATE.

   This SDWAN SAFI is for a scenario where one SDWAN edge node has
   multiple WAN ports, some of which connected to private networks and
   others connected to public untrusted networks [Scenario #2 described
   in the [SDWAN-BGP-USAGE]]. The same routes attached to the SDWAN can
   be reached by the private networks without encryption (for better
   performance) or by the public networks with encryption.



 2.3. How about a new Path Attribute under BGP UPDATE?

   It is also possible to have a new Path Attribute, say SDWAN Path
   Attribute, combined with Tunnel Path Attribute to advertise SDWAN
   WAN Port properties. Besides having a different Path Attribute ID,
   everything else is same as using MP-NLRI & Tunnel Path Attributes.



3. SDWAN WAN Port ID encoding in the MP-NLRI Path Attribute

   SDWAN WAN Port Identifier can be encoded in the NLRI field within
   the MP_REACH_NLRI Path Attribute of RFC4760, under a SDWAN SAFI
   (code = 74):





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   +------------------+
   |   NLRI Length    | 1 octet
   +------------------+
   |   SDWAN-Type     | 2 Octets
   +------------------+
   |Port-Distinguisher| 4 octets
   +------------------+
   |  SDWAN-Site-ID   | 4 octets
   +------------------+
   |  SDWAN-Node-ID   | 4 or 16 octets
   +------------------+



   where:

     - NLRI Length: 1 octet of length expressed in bits as defined in
       [RFC4760].
     - SDWAN-Type: to define the encoding of the rest of the SDWAN
       NLRI. There could be different sub-TLVs for different SDWAN WAN
       ports and their associated policies.
     - Port Distinguisher: SDWAN edge node Port identifier, which can
       be locally significant. Each port can have unique properties.
       For example, some ports may get ISP or DHCP assigned IP
       addresses (IPv4 or IPv6), some may have private IP addresses
       that packets to/from those ports have to traverse NAT.
       The detailed properties about the port are further encoded in
       the subTLVs, e.g. Port-subTLV under the Tunnel Path Attribute.

     - SDWAN-Site-ID: used to identify a common property shared by a
       set of SDWAN edge nodes, such as the property of a specific
       geographic location shared by a group of SDWAN edge nodes. The
       property is used to steer an overlay route to traverse specific
       geographic locations for various reasons, such as to comply
       regulatory rules, to utilize specific value added services, or
       others.
     - SDWAN EdgeNode ID: the SDWAN edge node identifier, which can be
       the node's system ID or the loopback address (IPv4 or IPv6) of
       the SDWAN edge node.



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4. WAN Port Properties encoding in the Tunnel Path Attribute

   The content of the SDWAN Port properties is encoded in the Tunnel
   Encapsulation Attribute defined in [Tunnel-Encap] using a new
   Tunnel-Type TLV (code point to be assigned by IANA from the "BGP
   Tunnel Encapsulation Attribute Tunnel Types" registry).

   Tunnel Encaps Path Attribute (Code = 23)

     Tunnel Type: SDWAN-WAN-Port
     Followed by the detailed properties encoded as subTLV, such as
          SubTLV for NAT
          SubTLV for IPsec-SA Attribute
          SubTLV for ISP connected to the WAN port


   The Tunnel Encaps Attribute are defined as follows:

   0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | Tunnel-Type(=SDWAN-WAN-Port )| Length (2 Octets)              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   |                             Value                             |
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
           SDWAN Tunnel Encapsulation TLV Value Field

   Where:
      Tunnel Type is SDWAN-WAN-Port (to be assigned by IANA).


     4.1. Port Ext SubTLV

      Port Ext sub-TLV is for describing the NAT property if the port
      has private address and the network identifier to which the WAN
      port is connected, etc.

      A SDWAN edge node can inquire STUN (Session Traversal of UDP
      Through Network Address Translation RFC 3489) Server to get the
      NAT property, the public IP address and the Public Port number to
      pass to peers.


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        0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |Port Ext Type  |  EncapExt subTLV Length       |I|O|R|R|R|R|R|R|
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       | NAT Type      |  Encap-Type   |Trans networkID|     RD ID     |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                  Local  IP Address                            |
                  32-bits for IPv4, 128-bits for Ipv6
                          ~~~~~~~~~~~~
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                  Local  Port                                  |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                Public IP                                      |
                  32-bits for IPv4, 128-bits for Ipv6
                          ~~~~~~~~~~~~
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                Public Port                                    |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   Where:

     o Port Ext Type: indicate it is the Port Ext SubTLV.
     o PortExt subTLV Length: the length of the subTLV.
     o Flags:
          - I bit (CPE port address or Inner address scheme)
             If set to 0, indicate the inner (private) address is IPv4.
             If set to 1, it indicates the inner address is IPv6.

          - O bit (Outer address scheme):
             If set to 0, indicate the public (outer) address is IPv4.
             If set to 1, it indicates the public (outer) address is
             IPv6.

          - R bits: reserved for future use. Must be set to 0 now.


     o NAT Type.without NAT; 1:1 static NAT; Full Cone; Restricted
        Cone; Port Restricted Cone; Symmetric; or Unknown (i.e. no
        response from the STUN server).




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     o Encap Type.the supported encapsulation types for the port
        facing public network, such as IPsec+GRE, IPsec+VxLAN, IPsec
        without GRE, GRE (when packets don't need encryption)
     o Transport Network ID.Central Controller assign a global unique
        ID to each transport network.
     o RD ID.Routing Domain ID.Need to be global unique.
     o Local IP.The local (or private) IP address of the port.
     o Local Port.used by Remote SDWAN edge node for establishing
        IPsec to this specific port.
     o Public IP.The IP address after the NAT. If NAT is not used,
        this field is set to NULL.
     o Public Port.The Port after the NAT. If NAT is not used, this
        field is set to NULL.

     4.2. IPsec Security Association Property

     The IPsecSA sub-TLV is for the SDWAN edge node to establish IPsec
     security association with their peers via the port that face
     untrusted network:

        0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |IPsec-SA Type  |IPsecSA Length                 | Flag          |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |  Transform    | Transport    | AH             |   ESP         |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |         SPI                                                   |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       | key1 length   |         key1                                  |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       | key2 length   |         key2                                  |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       | key3 length   |         key3                                  |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |        Duration                                               |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   Where:






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     o IPsec-SA SubTLV Type: to be assigned by IANA. The type value
        has to be between 128~255 because IPsec-SA subTLV needs 2 bytes
        for length to carry the needed information.
     o IPsec-SA subTLV Length (2 Byte): 25 (or more)
     o Flags: 1 octet of flags. None are defined at this stage. Flags
        SHOULD be set to zero on transmission and MUST be ignored on
        receipt.
     o Transform (1 Byte):  the value can be AH, ESP, or AH+ESP.
     o Transport (1 byte): the value can be Tunnel Mode or Transport
        mode
     o AH (1 byte): AH authentication algorithms supported, which can
        be md5 | sha1 | sha2-256 | sha2-384 | sha2-512 | sm3. Each
        SDWAN edge node can have multiple authentication algorithms;
        send to its peers to negotiate the strongest one.
     o ESP (1 byte): ESP authentication algorithms supported, which
        can be md5 | sha1 | sha2-256 | sha2-384 | sha2-512 | sm3. Each
        SDWAN edge node can have multiple authentication algorithms;
        send to its peers to negotiate the strongest one. Default
        algorithm is AES-256.
     o SPI: 4 bytes
     o Key1.AH authentication key
     o Key2.ESP authentication key
     o Key3.ESP encryption "public" key
     o Duration: SA life span.

     4.3. Remote Endpoint

   The Remote Endpoint sub-TLV is not used for SDWAN NLRI because
     o The SDWAN Node ID and Site ID are already encoded in the SDWAN
        NLRI,
     o The network connected by the SDWAN WAN port might have
        identifier that is more than the AS number. SDWAN controller
        might use its own specific identifier for the network.
     o The Transport-Network-ID in the EncapExt sub-TLV represents the
        SDWAN unique network identifier.

     If the Remote Endpoint Sub-TLV is present, it is ignored by other
     SDWAN edge nodes.





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5. Manageability Considerations

      TBD - this needs to be filled out before publishing

6. Security Considerations

     The document describes the encoding for SDWAN edge nodes to
     advertise its SDWAN WAN ports properties to their peers via
     untrusted & unsecure networks.

     The secure propagation is achieved by secure channels, such as
     TLS, SSL, or IPsec, between the SDWAN edge nodes and the local
     controller RR.

    [More details need to be filled in here]


7. IANA Considerations

   This document requires the following IANA actions.

       o SDWAN Overlay SAFI = 74 assigned by IANA
       o SDWAN Route Type

8. References


     8.1. Normative References

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

   [RFC8192] S. Hares, et al, "Interface to Network Security Functions
             (I2NSF) Problem Statement and Use Cases", July 2017

   [RFC5521] P. Mohapatra, E. Rosen, "The BGP Encapsulation Subsequent
             Address Family Identifier (SAFI) and the BGP Tunnel
             Encapsulation Attribute", April 2009.





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   [Tunnel-Encap]E. Rosen, et al, "The BGP Tunnel Encapsulation
             Attribute", draft-ietf-idr-tunnel-encaps-09, Feb 2018.

   [VPN-over-Internet] E. Rosen, "Provide Secure Layer L3VPNs over
             Public Infrastructure", draft-rosen-bess-secure-l3vpn-00,
             work-in-progress, July 2018

   [DMVPN] Dynamic Multi-point VPN:
             https://www.cisco.com/c/en/us/products/security/dynamic-
             multipoint-vpn-dmvpn/index.html

   [DSVPN] Dynamic Smart VPN:
             http://forum.huawei.com/enterprise/en/thread-390771-1-
             1.html



   [ITU-T-X1036] ITU-T Recommendation X.1036, "Framework for creation,
             storage, distribution and enforcement of policies for
             network security", Nov 2007.

   [Net2Cloud-Problem] L. Dunbar and A. Malis, "Seamless Interconnect
             Underlay to Cloud Overlay Problem Statement", draft-dm-
             net2cloud-problem-statement-02, June 2018

   [Net2Cloud-gap] L. Dunbar, A. Malis, and C. Jacquenet, "Gap Analysis
             of Interconnecting Underlay with Cloud Overlay", draft-dm-
             net2cloud-gap-analysis-02, work-in-progress, Aug 2018.

   [Tunnel-Encap] E. Rosen, et al "The BGP Tunnel Encapsulation
             Attribute", draft-ietf-idr-tunnel-encaps-10, Aug 2018.



9. Acknowledgments

   Acknowledgements to Wang Haibo, Hao Weiguo, and ShengCheng for
   implementation contribution; Many thanks to Jim Guichard, John
   Scudder, Darren Dukes, Andy Malis, Rachel Huang and Donald Eastlake
   for their review and contributions.



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   This document was prepared using 2-Word-v2.0.template.dot.















































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Authors' Addresses


   Linda Dunbar
   Futurewei
   Email: ldunbar@futurewei.com

   Sue Hares
   Hickory Hill Consulting
   Email: shares@ndzh.com





































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