Extension of Transport Aware Mobility in Data Network
draft-mcd-rtgwg-extension-tn-aware-mobility-02

Document Type Active Internet-Draft (individual)
Authors Kausik Majumdar  , Uma Chunduri  , Linda Dunbar 
Last updated 2021-07-12
Stream (None)
Intended RFC status (None)
Formats pdf htmlized bibtex
Stream Stream state (No stream defined)
Consensus Boilerplate Unknown
RFC Editor Note (None)
IESG IESG state I-D Exists
Telechat date
Responsible AD (None)
Send notices to (None)
RTG Working Group                                           K. Majumdar
Internet Draft                                                CommScope
Intended status: Informational                              U. Chunduri
Expires: October 12, 2022                                         Intel
                                                              L. Dunbar
                                                              Futurewei
                                                         July 12, 2021

           Extension of Transport Aware Mobility in Data Network
              draft-mcd-rtgwg-extension-tn-aware-mobility-02

Abstract

   The existing Transport Network Aware Mobility for 5G [TN-AWARE-
   MOBILITY] draft specifies a framework for mapping the 5G mobile
   systems Slice and Service Types (SSTs) to corresponding underlying
   network paths in IP and Layer 2 Transport networks.The focus of that
   work is limited to the mobility domain and transport network
   characteristics till the UPF and doesn't go beyond the UPF to the
   Data Network.

   To maintain E2E transport network characteristics the framework
   needs to be extended beyond UPF. This document describes a framework
   for extending the mobility aware transport network characteristics
   from the UPF through the Data Network.

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.

   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."

xxx, et al.            Expires January 12, 2022                [Page 1]
Internet-Draft      Extension of TN Aware Mobility            July 2021

   The list of current Internet-Drafts can be accessed at
   http://www.ietf.org/ietf/1id-abstracts.txt

   The list of Internet-Draft Shadow Directories can be accessed at
   http://www.ietf.org/shadow.html

   This Internet-Draft will expire on April 23, 2021.

Copyright Notice

   Copyright (c) 2021 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
   (http://trustee.ietf.org/license-info) in effect on the date of
   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...................................................3
   2. Conventions used in this document..............................4
   3. Framework for Extension of Transport Network Aware Mobility....4
   4. Mobility Packet Transition to the Data Network.................5
   5. Transport Network Characteristics Mapping to SR-TE Paths.......7
      5.1. Extend TN Aware Mobility for BGP SR-TE Policy.............9
      5.2. Extend TN Aware Mobility for SR-PCE Controller...........13
      5.3. Extend TN Aware Mobility for RestConf/gRPC based SR-TE
      Controller....................................................16
      5.4. Extend BGP FlowSpec for TN Aware Mobility................18
   6. Mapping of TN Characteristics on SD-WAN Edge Node.............21
      6.1. SD-WAN Hybrid Use Case with SR-TE Integration............23
   7. IANA Considerations...........................................25
   8. Security Considerations.......................................25
   9. Contributors..................................................25
   10. References...................................................25
      10.1. Normative References....................................25

Majumdar, et al.       Expires October15, 2022                 [Page 2]
Internet-Draft      Extension of TN Aware Mobility            July 2021

      10.2. Informative References..................................26
   11. Acknowledgments..............................................26
   Authors' Addresses...............................................28

1. Introduction

   The [TN-AWARE-MOBILITY] draft defines the transport path
   characteristics in backhaul, midhaul, and fronthaul segments between
   the radio side network functions and user plane functions (UPF). It
   describes how various transport network underlay routing mechanisms
   apply to the framework laid out including RSVP-TE, SR, and also a
   data plane agnostic integrated routing and TE mechanism - Preferred
   Path Routing (PPR) to map the network slice properties into the
   IP/L2 transport network.

   The current [TN-AWARE-MOBILITY] draft doesn't extend the transport
   network characteristics from the UPF through the Data Network. If
   the user service termination happens in the data network, the
   Transport Path Network characteristics through the Data Network
   would be lost.

   This proposed Extension of Transport Aware Mobility in Data Network
   extends the mobility aware transport network characteristics from
   the UPF through the Data Network.

   The UPF can be placed on the edge of the network where it can
   perform entry or exit point to the Data Network. It can connect to a
   Provider Edge node as well and bring all the mobile connections in a
   distributed way to the Data Network.

   The UPF can as well connect to the SD-WAN edge node or L3 aggregator
   device and would try to bring all the 5G mobility connections for
   small, medium, and large enterprises. This would be a scenario for
   Enterprise 5G.

   The current draft proposes mechanisms on how mobility aware
   transport network characteristics to be mapped into SR-TE paths or
   Un-secure, Secure, Secure SR-TE paths based in the Data Network on
   different use cases scenarios.

Majumdar, et al.       Expires October15, 2022                 [Page 3]
Internet-Draft      Extension of TN Aware Mobility            July 2021

2. Conventions used in this document

   BSID       - Binding SID

   DC         - Data Center

   DN         - Data Network (5G)

   EMBB       - enhanced Mobile Broadband (5G)

   gNB        - 5G NodeB

   GTP-U      - GPRS Tunneling Protocol - Userplane (3GPP)

   MIOT       - Massive IOT (5G)

   PECP       - Path Computation Element (PCE) Communication Protocol

   SD-WAN     - Software-Defined Wide Area Network

   SID        - Segment Identifier

   SLA        - Service Layer Agreement

   SST        - Slice and Service Types (5G)

   SR         - Segment Routing

   SR-PCE     - SR Path Computation Element

   UE         - User Equipment

   UPF        - User Plane Function (5G)

   URLLC      - Ultra reliable and low latency communications (5G)

3. Framework for Extension of Transport Network Aware Mobility

  Architecture wise, the proposed Extension of Transport Aware
  Mobility in the Data Network solution focuses on the following areas:

Majumdar, et al.       Expires October15, 2022                 [Page 4]
Internet-Draft      Extension of TN Aware Mobility            July 2021

  a) The Mobility packet transition in and out from the UPF to the C-PE
     Node maintaining the Transport Path Characteristics.

  b) On a PE node, based on the transport characteristics, use
     different methods of fetching SR-TE path segments from the SR-TE
     Controller and map the SR-TE segments with the mobility aware
     transport packets.

  c) On an SD-WAN CE Node, based on the transport characteristics,
     mapping of mobility aware transport packets to the secure and un-
     secure tunnel path.

  Figure 1 captured under Section 4 provides the representation of a
  network on how UE could be connected to the UPF and C-PE nodes in the
  Data Network. The C-PE node represents a combined CE and PE node. In
  some cases, UPF would be connected to the pure PE or CE node.

4. Mobility Packet Transition to the Data Network

     As the Transport Aware Mobility packets transition in and out from
     the UPF to the PE or C-PE (in SDWAN case) node, the Mobility
     Transport Characteristics need to be maintained in the Data
     Network. The current solution proposes a generic approach to how
     the mobility packet transition can happen in the Data Network
     maintaining the same transport characteristics.

     There are two scenarios could happen here:

     A) The UPF is not co-located with the C-PE in the same device.
     Based on the local policy the proposed new header format for the
     TN Aware Mobility Packets transitioning from the UPF to the C-PE
     device and vice-versa is proposed below:

       . From the UPF to the C-PE Node:
     Inner IP Hdr (UE Packet) + Transport Hdr (Carrying UDP Src Port) +
     Outer IP (C-PE Node Address)

       . From the C-PE to the UPF Node:
     Outer IP (UPF Node Address) + Transport Hdr (Carrying UDP Src
     Port) + Inner IP Hdr (UE Packet)

     B)            The UPF is co-located with the C-PE in the same device. Based on
       the local policy the original UDP Source Port information can be
       passed to the local C-PE node and no new header is needed here.

Majumdar, et al.       Expires October15, 2022                 [Page 5]
Internet-Draft      Extension of TN Aware Mobility            July 2021

     The current draft proposes to create a new encapsulation header in
     scenario A. At the UPF node, the TN aware mobility UE packet
     carrying the original UDP header Source Port information along
     with the Inner IP packet to get encapsulated with the outer IP
     header of the outgoing C-PE node IP address.

     In below Figure 1, both scenarios are captured. Scenario A
     captures the UPF is physically separated from the C-PE node over
     an IP network. Scenario B captures the edge networking deployment.
     In that case, the virtual UPF could be co-located with the
     physical C-PE node in the same device.

     Scenario A:

                 +-----------+       +-----+       +-----+
                 |           |       |     |       |     |
      UE---------| gNB-CU(UP)|-------| UPF |-------| C-PE|------DN
                 |           |       |     |       |     |
                 +-----------+       +-----+       +-- --+

                      |--- N3 OR N9 ---||---- N6 ----|

       |-------- Mobile Network -------||------ IP Network ------|

     Scenario B:

          +-----------+      +------+
           |           |      |      |
      UE---| gNB-CU(UP)|------| UPF +|--------DN-------
           |           |      | C-PE |
           +-----------+      +------+

                   |- N3 OR N9 -||----N6 -------------|

      |------ Mobile Network ----||-- IP Network-------|

                  Figure 1: Mobile and IP Data Network for UE

     The Figure 2 captures the TN Aware Mobility packet format under
     the scenario A.

Majumdar, et al.       Expires October15, 2022                 [Page 6]
Internet-Draft      Extension of TN Aware Mobility            July 2021

      1. UE Packet format in the Mobile Network to the UPF:

       +---------+----------+-------+------------+----------+
       | UE Data | Inner IP | GTP-U | UDP Header | Outer IP |
       +---------+----------+-------+------------+----------+

       2. UE Packet format in the IP Network to the Ingress C-PE Node:

       +---------+----------+------------------+------------+
       | UE Data | Inner IP | Transport Header | C-PE Header|
       +---------+----------+------------------+------------+

            Figure 2: UE Packet Transition from Mobile to IP Network

   The source port in the original UDP header indicates the TN Aware
   Mobility SST type.

5. Transport Network Characteristics Mapping to SR-TE Paths

     With the 5G Mobile Networking, the UPF would be terminating the
     mobile connection from the UE. In some Edge Networking scenarios,
     the virtual UPF would be co-located with the C-PE or it would be
     connected to the C-PE node over IP Network.

     The 5G UE traffic coming to the UPF might be carrying Transport
     Network Characteristics. In that scenario, there would be a need
     to maintain the Transport Path Characteristic through the core of
     the network so that end to end SLA can be maintained for the UE
     traffic.

     In scenarios, where ingress PE acting as SR-TE node, the mapping
     of Transport Network Aware Mobility {5G UDP Src Port Range} to
     {BGP SR-TE Policy, BSID} to be done at the ingress PE. Once this
     mapping is done, the mobility Transport Path Characteristics can
     be maintained in the data network.

     On a PE node, based on the transport characteristics, the current
     solution proposes different methods of applying SR-TE path
     segments:

     Scenario 1: In this scenario, the assumption is that the Ingress
     PE node is connected to the BGP SR-TE Controller through the BGP
     SR-TE Policy SAFI Session. This solution defines a mechanism to

Majumdar, et al.       Expires October15, 2022                 [Page 7]
Internet-Draft      Extension of TN Aware Mobility            July 2021

     map the BGP SR-TE Underlay Path Segments based on the Mobility
     Transport Characteristics.

       . This mechanism would require a new BGP Sub-TLV as part of the
          existing SR Policy SAFI NLRI to download SR-TE Policies
          corresponds to the mobility Transport Path characteristics.
          If the TN aware mobility packet UDP Source Port value falls
          within the UDP Src Port range value of this Sub-TLV, then the
          pre-downloaded SR-TE Policy MUST be applied on the mobility
          traffic to map to the correct network slice in the Data
          Network. Once the Policy is fetched it would be cached by the
          PE node for operating in line with the subsequent mobility TN
          aware packets.

     Scenario 2: In this scenario, the assumption is that the Ingress
     PE node is connected to the SR-PCE (Path Compute Element)
     Controller through the PCEP Session. This draft defines a
     mechanism to map the SR-TE Underlay Segments based on the Mobility
     Transport Path Characteristics.

       . Currently, this mechanism does not require new encoding in
          the PCEP based communication, though it needs local
          Configuration in the PE node to request the SR-TE Paths from
          the PCEP based Controller based on on-demand TN aware
          mobility traffic metric types.

     Scenario 3: In this scenario, the assumption is that the Ingress
     PE node is connected to the SR-TE Controller over Restconf/
     Netconf or gRPC session. The existing mechanism would be used to
     download the SR-TE Underlay Path Segments to the PE node based on
     the Mobility Transport Path Characteristics.

       . The Yang Data Model or Protobuf definition is required to
          define a new Sub-TLV like Scenario 1. The SR-TE Controller
          would pre-download the SR-TE Policies with the new Sub-TLV in
          the Ingress PE using the existing session. Once the specific
          SR-TE Policy is fetched, it would be cached by the Ingress PE
          to apply for the mobility TN aware traffic in-line to
          maintain the network characteristics in the Data Network.

     Scenario 4: In this scenario, the assumption is that the Ingress
     PE node is connected to the BGP SR FlowSpec Controller through the
     BGP FlowSpec Session. This draft defines a mechanism to map the

Majumdar, et al.       Expires October15, 2022                 [Page 8]
Internet-Draft      Extension of TN Aware Mobility            July 2021

     FlowSpec redirect to indirection-id community-based SR Traffic
     rules to the Mobility Transport Path Characteristics.

       . Currently, this mechanism does not require any new encoding
          in the BGP SR FlowSpec path redirect draft [FLOWSPEC-PATH-
          REDIRECT], though it needs local Configuration in the Ingress
          PE node that is acting as BGP FlowSpec Client to map the
          Mobility traffic based on the SR FlowSpec traffic re-
          direction rules.

5.1. Extend TN Aware Mobility for BGP SR-TE Policy

  1) To integrate Transport Network Aware Mobility with BGP SR-TE
     Policy at the Ingress PE UPF, the Class-map needs to be defined to
     classify the incoming mobility traffic with different Transport
     Path Characteristic.

  2) The Ingress PE UPF is assumed to have a BGP SR-TE Policy SAFI
     connection with the BGP SR-TE Controller. The Mobility traffic
     destination would resolve in the BGP Peer Next Hop for which SR-TE
     Policy to be applied to maintain the same network characteristics
     beyond the mobility domain.

  3) A new 5G Metadata Sub-TLV has been defined for existing SR-Policy
     SAFI with the UDP Source Port Range to identify the SR-TE path
     based on the Transport Path characteristics.

  4) The BGP SR-TE Controller would be programmed with {5G UDP Src Port
     Range}. That would create internal mapping Table for {5G UDP Src
     Port Range} < -- > {BGP SR-TE Policy, BSID}.

  5) The BGP SR-TE Controller would download the SR-TE Policy in the
     Ingress PE through the existing BGP SR-Policy SAFI session, and
     that the BGP update would include an additional 5G Metadata Sub-
     TLV. The UDP Src Port range in the 5G Metadata Sub-TLV MUST fall
     within the UDP Source Port range for the SSTs defined by the [TN-
     AWARE-MOBILITY] draft. If the UDP Src Port range falls outside the
     range defined by the [TN-AWARE-MOBILITY] draft, then the SR-TE
     Policy SHOULD be ignored by the Ingress PE.

  6) The SR-TE Policy-based traffic steering would be applied in the
     Ingress PE and it would maintain the local mapping for the reverse
     Mobility traffic to the UE.

Majumdar, et al.       Expires October15, 2022                 [Page 9]
Internet-Draft      Extension of TN Aware Mobility            July 2021

   The following class-map definition needs to be applied in the
   headend PE for the incoming Transport Network aware mobility traffic
   path:

   Class-map type traffic match MIOT

        Match UDP Src Port Range Xx - Xy

   Class-map type traffic match URLLC

        Match UDP Src Port Range Yx - Yy

   Class-map type traffic match EMBB

        Match UDP Src Port Range Zx - Zy

   The class-map would help to identify the incoming mobility traffic
   characteristics. Based on these characteristics the headend PE would
   be able to map the Transport Network aware mobility traffic to the
   appropriate BGP SR-TE Policy path over the Data Network to reach the
   UE's destination.

   The below figure tries to capture the overall topology, and how to
   map the mobility traffic in the Ingress PE having BGP SR-Policy SAFI
   connection with the BGP SR-TE Controller:

Majumdar, et al.       Expires October15, 2022                [Page 10]
Internet-Draft      Extension of TN Aware Mobility            July 2021

                         +-----------+   +----+{5G UDP Src Port Range}
                         | BGP SR-TE |-->| Map|       <-->
                         | Controller|   | DB |{BGP SR-TE Policy, BSID}
                         +-----------+   +----+
                           /
                          /
                         /
                        /
                       /                                    +--------+
                      / BGP SR-TE Policy with               |IOT Data|
                     /  5G Metadata Sub-TLV                 +--------+
                    /                                           /Public
                   /                                      MIoT / Cloud
                  /                                    +------+
             +------+  Policy1: UDP Src Port Xx-Xy    /
             |      A1-------------------------------+
             |      |  Policy2: UDP Src Port Yx-Yy    URLLC
     UE------| UPF  A2-----------------------------------------
             | +PE1 |  Policy3: UDP Src Port Zx-Zy
             |      A3------------------------------+
             |      |                                \
             +------+                                 +-------+
     {UDP Src Port Num# <--> SR Policy N}                 eMBB \
                                                                \
                                                              +--------+
                                                              | Content|
                                                              +--------+
                                                               Private DC
                  ---------->
       +------+----------+-------+-----+----------+
       | Data | Inner IP | GTP-U | UDP | Outer IP |
       +------+----------+-------+-----+----------+

                                      ---------->
                     +------+----------+-------------+
                     | Data | Inner IP |   SR Header |
                     +------+----------+-------------+

       Figure 3: TN Aware Mobility Traffic Mapping to BGP SR-TE Policy Path

Note that, in the above figure SR Header is shown as an illustrative
purpose and the actual outgoing packet format is based on the BGP SR-TE
mechanism (SR-MPLS or SRv6) on the Ingress PE. That could be SR-MPLS or
SRv6 Header. Though if the BSID is not present with the BGP SR-TE
Policy, the local Ingress PE would map the incoming traffic to the best
effort policy map path in the underlay.

Majumdar, et al.       Expires October15, 2022                [Page 11]
Internet-Draft      Extension of TN Aware Mobility            July 2021

  To support the Transport Network Mobility Traffic Mapping to BGP SR-
  TE Policy Path in the headend PE, a new 5G Metadata Sub-TLV needs to
  be supported. The proposed BGP SR Policy Encoding from the BGP SR-TE
  Policy Controller to the headend PE node is defined below:

   SR Policy SAFI NLRI: <Distinguisher, Policy-Color, Endpoint>
      Attributes:
         Tunnel Encap Attr (23)
           Tunnel Type: SR Policy
             Existing Policy Sub-TLV
             5G Metadata Sub-TLV

   The draft [BGP-SR-TE-POLICY] defines BGP SR-TE Policy encodings.
   There is no change in the existing encoding that is being used from
   the BGP SR-TE Controller to the headend PE node. The current
   solution proposes the new 5G Metadata Sub-TLV for BGP SR-TE
   Controller to download the SR Policies to the headend PE and to
   apply the SR-TE Policy-driven path for the Transport Network aware
   mobility traffic.

   The incoming TN aware mobility traffic with UDP Src port and BGP NH
   to the traffic destination would be used as a key to find the BGP
   SR-TE Policy. If the BGP Next Hop of the traffic matches with the SR
   Policy SAFI NLRI Endpoint, and UDP Src Port value falls within the
   UDP Src Port range defined by the 5G Metadata Sub-TLV, the SR Policy
   would be applied to the mobility traffic to maintain the traffic
   characteristics in the data network. The BGP SR-TE Controller would
   be pre-provisioned with the 5G UDP SRC Port Range based on the [TN-
   AWARE-MOBILITY] draft, and their corresponding BGP SR-TE Policy.

    The 5G Metadata sub-TLV is optional and it MUST NOT appear more than
   once in the SR-TE Policy.

   The format of the new SR-TE 5G Metadata Sub-TLV is captured below:

Majumdar, et al.       Expires October15, 2022                [Page 12]
Internet-Draft      Extension of TN Aware Mobility            July 2021

   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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |      Type     |    Sub-Type   |     Length    |     Flags     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |    UDP Src Port Start Value   |    UDP Src Port End Value     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                          5G Metadata Sub-TLV

    where:

    o  Type: To be defined by IANA.

   o  Sub-Type: This field has one of the following values:

         0: Reserved.
         1: UDP Source Port Range.
         2 - 255: Reserved for future use.

   o  Length: 6 octets.

   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  UDP Src Port Start Value: 2 octets value to define the staring of
     the value of the UDP Src Port range.

  o  UDP Src Port End Value: 2 octets value to define the end value of
     the UDP Src Port range.

5.2. Extend TN Aware Mobility for SR-PCE Controller

  1) To integrate Transport Network Aware Mobility with SR-TE ODN based
     PCE Controller at the Ingress PE UPF, the Class-map needs to be
     defined to classify the incoming mobility traffic with different
     Transport Path Characteristic.

  2) The Ingress PE UPF is assumed to have PCEP based communication
     with the SR-PCE Controller.

Majumdar, et al.       Expires October15, 2022                [Page 13]
Internet-Draft      Extension of TN Aware Mobility            July 2021

  3) The Ingress PE would define the Policy-map to map the Transport
     Path characteristics into SR-TE Color.

  4) The Segment Routing TE Configuration for different Metric types
     will associate the SR-TE Colors with their corresponding TE metric
     type.

  5) The existing SR-TE ODN based PCEP messages with TE metric type and
     value MUST be used to associate the SR-TE Path corresponding to
     the 5G UDP Src Port.

  6) In this case, the mapping between {5G UDP Src Port} and {SR-TE
     Policy} would be maintained by the Ingress PE.

  7) Once the TN aware mobility traffic destination resolves into a
     destination of BGP Peer Next Hop, the SR-TE ODN based traffic
     steering MUST be applied based on the UDP Src Port value of the
     incoming traffic.

   The class-map definition to identify the incoming mobility traffic
   characteristics is already defined in Section 5.1. The same class-
   map definition applicable here as well.

   The policy-map definition to associate SR-TE color with Transport
   Path characteristics is defined below:

   Policy-map type Transport-Network-Aware-Mobility

       Class type traffic MIOT

           Set color <MIOT-10>

       Class type traffic URLLC

           Set color <URLLC-20>

       Class type traffic EMBB

           Set color <EMBB-30>

   The Segment Routing TE Configuration mechanism can associate the SR-
   TE Colors with their corresponding metric type. That exists today,
   and there is no change there. It is captured here to show how TN

Majumdar, et al.       Expires October15, 2022                [Page 14]
Internet-Draft      Extension of TN Aware Mobility            July 2021

   aware mobility network characteristics get mapped to different TE
   metrics through this mechanism.

   Segment-routing traffic-eng

     On-demand color <MIOT-10> dynamic

        Metric

          Type <MIOT>

     On-demand color <URLLC-20> dynamic

        Metric

          Type <URLLC>

     On-demand color <EMBB-30> dynamic

        Metric

          Type <EMBB>

   As a result, mobility Transport Network aware of different traffic
   characteristics like MIOT, URLLC, or EMBB get to assigned
   corresponding "te" metric types. To fetch the corresponding SR-TE
   dynamic path from the SR-PCE Controller based on the newly defined
   "te" metric types <MIOT>, <URLLC> or <EMBB> needs to be extended in
   the PCEP RFC [RFC5440].

   The below figure tries to capture the overall topology, and how to
   map the mobility traffic in the headend PE having PCEP connection
   with the SR-PCE Controller:

Majumdar, et al.       Expires October15, 2022                [Page 15]
Internet-Draft      Extension of TN Aware Mobility            July 2021

                         +-----------+
                         | SR-PCE    |
                         | Controller|
                         +-----------+
                            /
                           /
           PCReq Message  /
         with Metric Type/
                        /                                   +--------+
                       /                                    |IOT Data|
                      /  PCRep Message                      +--------+
                     /   with Segment List                     /Public
                    /                                    MIOT / Cloud
                   /                                  +----- +
             +------+  Policy1: UDP Src Port Xx-Xy   /
             |      A1------------------------------+
             |      |  Policy2: UDP Src Port Yx-Yy    URLLC
     UE------| UPF  A2--------------------------------------------
             | +PE1 |  Policy3: UDP Src Port Zx-Zy
             |      A3-------------------------------+
             |      |                                 \
             +------+                                  +-----+
     {UDP Src Port Num# <--> SR Policy N}                EMBB \
                                                               \
                                                            +--------+
                                                            | Content|
                                                            +--------+
                                                             Private DC

            Figure 4: TN Aware Mobility Traffic Mapping to SR-TE Path

5.3. Extend TN Aware Mobility for RestConf/gRPC based SR-TE Controller

  1) To integrate Transport Network Aware Mobility with SR-TE Policy at
     the Ingress PE UPF, the Class-map needs to be defined to classify
     the incoming mobility traffic with different Transport Path
     Characteristic.

  2) The Ingress PE UPF is assumed to have Restconf or gRPC connection
     with the SR-TE Controller. The Mobility traffic destination would
     resolve in the BGP Peer Next Hop for which SR-TE Policy to be
     applied to maintain the same network characteristics beyond the
     mobility domain.

Majumdar, et al.       Expires October15, 2022                [Page 16]
Internet-Draft      Extension of TN Aware Mobility            July 2021

  3) A new 5G Metadata Yang data model and Protobuf to be defined for
     SR-Policy SAFI with UDP Source Port Range to identify the SR-TE
     path based on the Transport Path characteristics.

  4) The SR-TE Controller would be programmed with {5G UDP Src Port
     Range}. That would create internal mapping Table for {5G UDP Src
     Port Range} < -- > {BGP SR-TE Policy, BSID}.

  5) As the Headend PE sends the 5G metadata Yang data model or
     Protobuf, the Controller will find a matching SR-TE Policy based
     on the UDP Source Port.

  6) The SR-TE Controller would download the SR-TE Policy in the
     Ingress PE through the existing Restconf or gRPC session, and that
     BGP update would include an additional 5G Metadata Sub-TLV. The
     UDP Src Port range in the 5G Metadata Sub-TLV MUST fall within the
     UDP Source Port range for the SSTs defined by the [TN-AWARE-
     MOBILITY] draft. If the UDP Src Port range falls outside the range
     defined by the [TN-AWARE-MOBILITY] draft, then the SR-TE Policy
     SHOULD be ignored by the Ingress PE.

  7) The SR-TE Policy-based traffic steering would be applied in the
     Ingress PE UPF and it would maintain the local mapping for the
     reverse Mobility traffic to the UE.

   The class-map definition to identify the incoming mobility traffic
   characteristics is already defined in Section 5.1. The same class-
   map definition works here as well.

   The below figure tries to capture the overall topology, and how to
   map the mobility traffic in the headend PE having BGP SR-Policy SAFI
   connection with the BGP SR-PCE Controller:

Majumdar, et al.       Expires October15, 2022                [Page 17]
Internet-Draft      Extension of TN Aware Mobility            July 2021

                            +-----------+   +----+{5G UDP Src Port Range}
                            | BGP SR-TE |-->| Map|       <-->
                            | Controller|   | DB |{BGP SR-TE Policy, BSID}
                            +-----------+   +----+
                              /
                             /
                            /
          Restconf or gRPC /
             Session      /                                    +--------+
                         / SR-Policy with                      |IOT Data|
                        /  5G Metadata Sub-TLV                 +--------+
                       /                                         /Public
                      /                                    MIOT / Cloud
                     /                                  +------+
             +-------+  Policy1: UDP Src Port Xx-Xy    /
             |       A1------------------------------ +
             |       |  Policy2: UDP Src Port Yx-Yy     URLLC
     UE------| UPF + A2-------------------------------------------
             | PE1   |  Policy3: UDP Src Port Zx-Zy
             |       A3------------------------------ -+
             |       |                                  \
             +-------+                                   +-----+
     {UDP Src Port Num# <--> SR Policy N}                  EMBB \
                                                                 \
                                                               +--------+
                                                               | Content|
                                                               +--------+
                                                                Private DC

             Figure 5: TN Aware Mobility Traffic Mapping to SR-TE Path

5.4. Extend BGP FlowSpec for TN Aware Mobility

  1) To integrate Transport Network Aware Mobility with SR-TE Policy at
     the Ingress PE UPF, the Class-map needs to be defined to classify
     the incoming mobility traffic with different Transport Path
     Characteristic.

  2) The Ingress PE UPF that is acting as BGP FlowSpec Client is
     assumed to have a BGP FlowSpec session with the FlowSpec
     Controller. The Mobility traffic destination would resolve in the
     BGP Peer Next Hop for which SR FlowSpec traffic re-direct policy
     to be applied to maintain the same network characteristics in the
     data network.

Majumdar, et al.       Expires October15, 2022                [Page 18]
Internet-Draft      Extension of TN Aware Mobility            July 2021

  3) The current proposal tries to integrate FlowSpec Redirect to
     Indirection ID [FLOWSPEC-PATH-REDIRECT] based traffic rules with
     the TN aware mobility traffic based on the UDP Source Port range
     at the FlowSpec Client Router/Ingress PE.

  4) Based on the BGP FlowSpec RFC 8955 the BGP FlowSpec NLRI can carry
     out the UDP Source Port range. The 5G SST specific UDP Source Port
     range values can be pushed over a BGP FlowSpec session between the
     FlowSpec Controller and the Ingress PE node.

  5) There are no additional changes required on the BGP FlowSpec side
     other than provisioning 5G SST specific UDP Source Port range at
     the FlowSpec Controller along with the corresponding FlowSpec
     Redirect to indirection-id.

  6) The BGP FlowSpec Controller would be programmed with {5G UDP Src
     Port Range} to map different SSTs defined in [TN-AWARE-MOBILITY]
     draft to map the corresponding FlowSpec Redirect to Indirection-
     id. That would create internal mapping Table for {5G UDP Src Port
     Range} < -- > {BGP FlowSpec Generalized Indirection-ID}.

  7) The BGP FlowSpec NLRI carrying 5G UDP Source Port Range along with
     the corresponding Redirect to indirection-id Extended Community
     can be pushed to the Ingress PE node.

  8) The Mobility traffic coming from the UPF to the Ingress PE in the
     Data Network carrying specific UDP Source Port from UE can be
     classified based on the local Policy and apply the BGP FlowSpec
     based re-direction rule based on the matching FlowSpec policy.

   The class-map definition to identify the incoming mobility traffic
   characteristics is already defined in Section 5.1. The same class-
   map definition works here as well.

   The below figure tries to capture the overall topology, and how to
   map the mobility traffic in the Ingress PE acting as FlowSpec Client
   having BGP FlowSpec SAFI connection with the BGP FlowSpec
   Controller:

Majumdar, et al.       Expires October15, 2022                [Page 19]
Internet-Draft      Extension of TN Aware Mobility            July 2021

                            +-----------+   +----+{5G UDP Src Port Range}
                            |  FlowSpec |-->| Map|       <-->
                            | Controller|   | DB |{Generalized Indirection-ID}
                            +-----------+   +----+
                              /
                             /
                            / BGP FlowSpec NLRI with 5G
              BGP FlowSpec /   UDP Source Port Range
                Session   /                                    +--------+
                         / BGP FlowSpec Redirect               |IOT Data|
                        / Indirection-ID Ext Comm              +--------+
                       /                                         /Public
                      /                                    MIOT / Cloud
                     /                                  +------+
             +-------+ Ind-ID1: UDP Src Port Xx-Xy     /
             |       A1-------------------------------+
             |       | Ind-ID2: UDP Src Port Yx-Yy            URLLC
     UE------| UPF + A2--------------------------------------------
             | PE1   | Ind-ID3: UDP Src Port Zx-Zy
             |       A3-------------------------------+
             |       |                                 \EMBB
             +-------+                                  +-----+
 {UDP Src Port Num# <--> FlowSpec Indirect-ID# ->Transport Hdr} \
                                                                \
                                                               +--------+
                                                               | Content|
                                                               +--------+
                                                                Private DC

                  ---------->
       +------+----------+-------+-----+----------+
       | Data | Inner IP | GTP-U | UDP | Outer IP |
       +------+----------+-------+-----+----------+

                                      ---------->
                     +------+----------+------------------+
                     | Data | Inner IP | Transport Header |
                     +------+----------+------------------+

           Figure 6: TN Aware Mobility Traffic Mapping to FS Redirect Path

Majumdar, et al.       Expires October15, 2022                [Page 20]
Internet-Draft      Extension of TN Aware Mobility            July 2021

6. Mapping of TN Characteristics on SD-WAN Edge Node

     On an SD-WAN CE Node, based on the mobility Transport Network
     characteristics, mapping of mobility aware transport packets to
     the secure and un-secure tunnel path needs to be achieved.

     The [BGP-IPSEC-Discover] draft defines how SD-WAN Edge Node maps
     the overlay/client routes to the underlay secure tunnel routes.

     The current proposal specifies a generic approach on how SD-WAN
     Edge Node maps the Mobility Transport Network aware traffic to the
     Secure Tunnels, or Un-Secure TE Paths, or Secure SR-TE Tunnel
     Paths.

     The [SDWAN-BGP-USAGE] draft describes how BGP can be used as a
     Control Plane for the SD-WAN network and defines the use case for
     the Hybrid SD-WAN network.

     In the case of a hybrid SD-WAN use case, UPF can run part of the
     SD-WAN edge node or it could be connected to it over an IP
     network. This would be a use case scenario for Enterprise 5G.

     In that scenario, the Transport Path Characteristic for the 5G
     mobile traffic need to be mapped to Secure (IPSec Tunnel) or Un-
     secure path (could be MPLS based).

     The existing [TN-AWARE-MOBILITY] draft is extended to support new
     Transport Path Characteristics "Security" for the mobile traffic
     where security is important for certain mobile traffic.

     Based on the UDP Src Port characteristics coming from the mobile
     network, the SD-WAN edge node would be able to decide what traffic
     it needs to put in the secure tunnel vs. an un-secure tunnel where
     low latency more important than security.

Majumdar, et al.       Expires October15, 2022                [Page 21]
Internet-Draft      Extension of TN Aware Mobility            July 2021

     The below figure tries to capture the overall topology, and how to
     map the mobility traffic in the SD-WAN Edge Device for Enterprise
     5G cases:

                                 +----------+
                                 |  BGP RR  |
                            +----|Controller|----+
                           /     +----------+     \
                          /                        \           Internet
                         /                          \           /
                        /                            \         /
                       /                              \  URLLC/
                      /                                \     /
                     /                                  \   /
            +-------+  MPLS Path: URLLC Traffic   +------+ /
            |       A1---------------------------B1      |/
            |       |  Secure Path1: MIOT Traffic |      | MIOT +--------+
     UE-----| UPF + A2---------------------------B2 C-PE2|------|IOT Data|
            | C-PE1 |  Secure Path2: EMBB Traffic |      |      +--------+
            |       A3---------------------------B3      |\      Public
            |       |                             |      | \     Cloud
            +-------+                             +------+  \
     {UDP Src Port X <--> MPLS}                              \
     {UDP Src Port Y:Security <--> IPSec SA Identifier}  EMBB \
                                                               \ +-------+
                                                                \|Content|
                                                                 +-------+
                                                                    Public
                                                                    Cloud
                  ---------->
       +------+----------+-------+-----+----------+
       | Data | Inner IP | GTP-U | UDP | Outer IP |
       +------+----------+-------+-----+----------+

                                           ---------->
                         +------+----------+--------------+
                         | Data | Inner IP | IPSec Header |
                         +------+----------+--------------+

    Figure 7: Secure TN Aware Mobility Traffic Mapping in the SD-WAN Edge Device

   Here in this diagram, the traffic coming from the mobility side with
   Transport Network characteristics gets mapped to the underlay un-
   secure or secure traffic path.

Majumdar, et al.       Expires October15, 2022                [Page 22]
Internet-Draft      Extension of TN Aware Mobility            July 2021

   The SD-WAN Edge Node can map the URLLC traffic without any security
   characteristics to the underlay MPLS path, whereas MIOT, and EMBB
   traffic with security characteristics gets mapped to the underlay
   Secure IPSec Tunnel path. The mapping between SD-WAN overlay and
   underlay routes are described in the [BGP-IPSEC-Discovery] draft.

   This solution extends it for Transport Network aware mobility
   traffic. The SD-WAN Edge Node here identifies the incoming mobility
   traffic characteristics using the class-map definition, and that is
   already defined under Section 5.1. Based on the incoming traffic
   characteristics, the Edge Node will be able to map the mobility
   overlay traffic to the respective SD-WAN underlay tunnel.

6.1. SD-WAN Hybrid Use Case with SR-TE Integration

  1) In the case of SD-WAN hybrid use cases, UPF can run part of the
     SD-WAN edge node, or it could be connected to it over an IP
     network. This would be a use case scenario for Enterprise 5G.

  2) The SD-WAN edge node can act as an SR-TE Headend PE in some use
     case scenarios that are described in [SDWAN-BGP-USAGE] draft.

  3) In that case, the Headend PE could be connected with SR-TE Policy
     Controller over the BGP SR-Policy SAFI session, or SR-PCE
     Controller over the PCEP session, or SR-TE Controller over
     Netconf/ Restconf, or GRPC session, or even SR FlowSpec Controller
     over BGP FlowSpec session.

  4) The SD-WAN edge node can map the "Un-secure" mobility traffic to
     the SR-TE path the same way as described under PE acting as
     ingress SR-TE headend.

  5) Though the mapping for "Secure" mobility traffic to the SR-TE path
     would be slightly different than "Un-secure" mobility traffic.

  6) The mobility 5G UE client traffic with the Transport Path
     Characteristics "Security" would be encapsulated with Tunnel mode
     IPSec header between the two SD-WAN SAFI underlay endpoints
     (belong to the same BGP AS domain). This encapsulated secure
     traffic will become the new overlay for the SR-TE traffic.

  7) The rest of the mechanism for the secure mobility traffic with SR-
     TE traffic forwarding is the same as un-secure SR-TE based traffic
     forwarding.

Majumdar, et al.       Expires October15, 2022                [Page 23]
Internet-Draft      Extension of TN Aware Mobility            July 2021

     The below figure tries to capture the overall topology, and how to
     map the mobility traffic in the SD-WAN Edge Device for SD-WAN
     Hybrid Use Cases described above:

                    +-------------+
                    | BGP SR-Based|
                    | Controller  |
                    +-------------+
                         /
                        /
                       /         +----------+
     BGP SR-TE Policy with       |  BGP RR  |
     5G Metadata Sub-TLV    +----|Controller|----+
                     /     /     +----------+     \
                    /     /                        \           Internet
                   /     /                          \           /
                  /     /                            \         /
                 /     /                              \  URLLC/
                /     /                                \     /
               /     /                                  \   /
            +-------+  SR-Pol1: URLLC Traffic     +------+ /
            |       A1---------------------------B1      |/
            |       | SA1,SR-Pol2: MIOT Traffic   |      | MIOT +--------+
     UE-----| UPF + A2---------------------------B2 C-PE2|------|IOT Data|
            | C-PE1 | SA2,SR-Pol3: EMBB Traffic   |      |      +--------+
            |       A3---------------------------B3      |\      Public
            |       |                             |      | \     Cloud
            +-------+                             +------+  \
     {UDP Src Port Num X <--> SR Policy1}                    \
     {UDP Src Port: Security Y, Z <-->                   EMBB \
                    IPSec SA 1,2; SR-TE Policy 2,3}            \ +-------+
                                                                \|Content|
                                                                 +-------+
                                                                    Public
                                                                    Cloud
                  ---------->
       +------+----------+-------+-----+----------+
       | Data | Inner IP | GTP-U | UDP | Outer IP |
       +------+----------+-------+-----+----------+

                                     ---------->
         +------+----------+--------------+-----------+
         | Data | Inner IP | IPSec Header | SR Header |
         +------+----------+--------------+-----------+

   Figure 8: Secure TN Aware Mobility Traffic Mapping for Hybrid SD-WAN Use Case

Majumdar, et al.       Expires October15, 2022                [Page 24]
Internet-Draft      Extension of TN Aware Mobility            July 2021

   In Figure 8, the traffic coming from the mobility side with
   Transport Network characteristics gets mapped to the underlay un-
   secure or secure SR-TE path to maintain the traffic network
   characteristics in the Data Network.

   The SD-WAN Edge Node can map the URLLC traffic without any security
   characteristics to the underlay SR-TE path without any IPSec
   encapsulation. Whereas MIOT and EMBB traffic with the security
   characteristics can be mapped to the underlay Secure IPSec Tunnel
   path with the SR-TE encapsulation to the SD-WAN endpoints.

7. IANA Considerations

   The newly defined 5G Metadata Sub-TLV would need an IANA code point
   allocation for the Type field. A request for any IANA code point
   allocation would be submitted.

8. Security Considerations

    This document does not introduce any new security issues.

9. Contributors

   The following people have contributed to this document.

   Dhruv Dhody
   Divyashree Techno Park, Whitefield
   Bangalore, Karnataka 560066
   India

   Email: dhruv.ietf@gmail.com

10. References

10.1. Normative References

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

Majumdar, et al.       Expires October15, 2022                [Page 25]
Internet-Draft      Extension of TN Aware Mobility            July 2021

10.2. Informative References

   [RFC5440] JP. Vasseur, Ed., JL. Le Roux, Ed., "Path Computation
   Element (PCE) Communication Protocol (PCEP)", March 2009

   [TN-AWARE-MOBILITY] U. Chunduri, et al, "Transport Network aware
   Mobility for 5G", draft-clt-dmm-tn-aware-mobility-07, April 2021

   [BGP-SR-TE-POLICY] S. Previdi, et al, "Advertising Segment Routing
   Policies in BGP", draft-ietf-idr-segment-routing-te-policy-09,
   November 2020

   [SDWAN-BGP-USAGE] L. Dunber, et al, "BGP Usage for SDWAN Overlay
   Networks", draft-dunbar-bess-bgp-sdwan-usage-08, January 2021

   [BGP-IPSEC-Discover] L. Dunber, et al, "BGP UPDATE for SDWAN Edge
   Discovery", draft-dunbar-idr-sdwan-edge-discovery-00, January 2021

   [Tunnel-Encap] E. Rosen, et al "The BGP Tunnel Encapsulation
             Attribute", draft-ietf-idr-tunnel-encaps-19, March 2021.

11. Acknowledgments

   TBD.

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

Majumdar, et al.       Expires October15, 2022                [Page 26]
Internet-Draft      Extension of TN Aware Mobility            July 2021

Majumdar, et al.       Expires October15, 2022                [Page 27]
Internet-Draft      Extension of TN Aware Mobility            July 2021

Authors' Addresses

   Kausik Majumdar
   CommScope
   350 W Java Drive, Sunnyvale, CA 94089

   Email: kausik.majumdar@commscope.com

   Uma Chunduri
   Intel
   2200 Mission College Blvd
   Santa Clara, CA  95052

   Email: umac.ietf@gmail.com

   Linda Dunbar
   Futurewei
   2330 Central Expressway
   Santa Clara, CA  95050

   Email: linda.dunbar@futurewei.com

Majumdar, et al.       Expires October15, 2022                [Page 28]