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BGP Dissemination of FlowSpec for Transport Aware Mobility
draft-dmc-idr-flowspec-tn-aware-mobility-03

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This is an older version of an Internet-Draft whose latest revision state is "Expired".
Authors Linda Dunbar , Kausik Majumdar , Uma Chunduri
Last updated 2023-07-10 (Latest revision 2022-06-27)
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draft-dmc-idr-flowspec-tn-aware-mobility-03
RTG Working Group                                     L. Dunbar
Internet Draft                                        Futurewei
Intended status: Standard track                     K. Majumdar
Expires: January 10, 2024                            Microsoft
                                                    U. Chunduri
                                                          Intel
                                                     July 10, 2023

     BGP Dissemination of FlowSpec for Transport Aware Mobility
             draft-dmc-idr-flowspec-tn-aware-mobility-03

Abstract

   This document defines a BGP Flow Specification (FlowSpec)
   extension to disseminate flows from 5G mobile networks so that
   the 5G mobile systems slices and Service Types (SSTs) can be
   mapped to optimal underlying network paths in the data network
   outside the 5G UPFs, or the N6 interface in 3GPP 5G
   Architecture [3GPP TR 23.501].

Status of this Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

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

Copyright Notice

   Copyright (c) 2023 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
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   document must include Simplified BSD License text as described
   in Section 4.e of the Trust Legal Provisions and are provided
   without warranty as described in the Simplified BSD License.

Table of Contents

   1. Introduction............................................... 2
   2. Conventions used in this document.......................... 3
   3. TN-Aware matching conditions............................... 4
   4. Redirect a flow over an underlay tunnel.................... 6
   5. FlowSpec Redirect to Indirection-ID Non-Transitive Extended
   Community..................................................... 8
   6. IANA Considerations........................................ 9
   7. Security Considerations.................................... 9
   8. Contributors............................................... 9
   9. References................................................. 9
      9.1. Normative References................................. 10
      9.2. Informative References............................... 10
   10. Acknowledgments.......................................... 11
   Authors' Addresses........................................... 12

1. Introduction

   The [TN-AWARE-MOBILITY-EXT] describes a framework for extending
   the mobility aware transport network characteristics through
   the Data Network outside the 5G UPFs.

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          +-----------+      +------+
           |           |      |      |
      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 5G UPF terminates the 5G GTP tunnels from gNB and pass the
   IP packets to the N6 data networks, which deliver the packets
   over hybrid paths, like MPLS, SR paths, Private-IP, or public
   Internet to reach the packets' destinations.

   This document focuses on using FlowSpec to disseminate rules
   that utilize the mobility aware transport network
   characteristics to forward 5G flows.

   Border Gateway Protocol (BGP) Flow Specification (FlowSpec)
   [RFC8955] and FlowSpec for IPv6 [RFC8956] leverage the BGP
   Control Plane to simplify the distribution of rules for the
   specified flows. FlowSpec filter rules can be injected to all
   BGP peers simultaneously without changing router configuration.

2. Conventions used in this document

   BSID       - Binding SID

   DC         - Data Center

   DN         - Data Network (5G)

   EMBB       - enhanced Mobile Broadband (5G)

   gNB        - 5G NodeB

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   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. TN-Aware matching conditions

   [RFC8955] defines a BGP Network Layer Reachability Information
   (NLRI) format used to distribute traffic flow specification
   rules. The NLRI for (AFI=1, SAFI=133) specifies IPv4 unicast
   filtering. The NLRI for (AFI=1, SAFI=134) specifies IPv4
   BGP/MPLS VPN filtering [RFC7432]. The Flow Specification match
   part defined in [RFC8955] includes L3/L4 information like IPv4
   source/destination prefix, protocol, ports, and the like, so
   traffic flows can be filtered based on L3/L4 information. This
   has been extended by [RFC8956] to cover IPv6 (AFI=2) L3/L4.

   The NLRI FlowSpec components described in RFC8955 and RFC8956
   are adequate for specifying the UDP Source Port Range which is

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   used to differentiate SLAs of flows from UPFs [EXT-TN-AWARE-
   Mobility].

   The Ingress PE, which can be a function within a UPF or an edge
   router directly connected to UFP, acting as BGP FlowSpec
   Receiver, is assumed to have a BGP FlowSpec session with the
   FlowSpec Controller. The Mobility traffic destination would
   resolve in the BGP Peer Next Hop in the data network. The BGP
   FlowSpec Controller would be programmed with {5G UDP Src Port
   Range} to map different SSTs defined in [TN-AWARE-MOBILITY] to
   create an internal mapping Table for {5G UDP Src Port Range} <
   -- > {BGP FlowSpec Generalized Indirection-ID}. The Mobility IP
   packets coming out of the UPF, i.e., the GTP header being
   decapsulated, carrying a specific UDP Source Port, can be
   classified based on the matching policy carried by the FlowSpec
   NLRI.

   For example, to filter out flows with source UDP port number
   between [i, j], the following encoding can be used in the NLRI
   (SAFI=133 or SAFI 134):

   Encoding

     <Type = 6, [numeric_op1, i][numberic_op2, j]>

     <Type = 2, [numeric_op3, Src-Prefix]>

     <Type = 1, [numeric_op4, Dest-prefix]>

   Numberic_Op1 is:

       0    1   2   3   4   5   6   7
      +---+---+---+---+---+---+---+---+
      | e | a | len   | 0 |lt |gt |eq |
      | 0 | 1 |  00   | 0 | 0 | 1 | 0 |
      +---+---+---+---+---+---+---+---+

   Numberic_Op2 is:

       0    1   2   3   4   5   6   7
      +---+---+---+---+---+---+---+---+
      | e | a | len   | 0 |lt |gt |eq |
      | 1 | 1 |  00   | 0 | 1 | 0 | 0 |
      +---+---+---+---+---+---+---+---+

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   Where len ==0, meaning two bytes of value [i] follows the
   Numeric_op1 and two bytes of value [j] follows the
   Numberic_op2.

   The "numeric_op3" and "numeric_op4" are for comparing the
   source and destination addresses of the UE traffic.

4. Redirect a flow over an underlay tunnel

   For the flows matching with the filter conditions carried by
   the FlowSpec NLRI, the policy for redirect path can indicate a
   set of underlay tunnels or one underlay tunnel.

   As the action of taking specific underlay tunnels is performed
   by the headend router, a non-transitive Extended Community for
   Path Redirect [Flowspec-path-redirect] and [SRv6-flowspec-path-
   redirect] should be used.

   [IANA Action: need a new type:

      0x49  FlowSpec Redirect to Indirection-id Non-transitive
   Extended Community.

   ]

   For hierarchical RR deployments where the FlowSpec rules need
   to be propagated, the Transitive Path Redirect Extended
   Community [FlowSpec-path-redirect] can be used.

   The below figure tries to capture the overall topology, showing
   the mobility traffic from UPF being redirected to different
   paths per the BGP FlowSpec from the Controller:

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

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

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

        Figure 2: TN Aware Mobility Traffic Mapping to FS Redirect Path

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5. FlowSpec Redirect to Indirection-ID Non-Transitive Extended
   Community

   This section defines "FlowSpec Redirect to Indirection-ID Non-
   Transitive Extended Community for IPSec Tunnel ID". The format
   of this extended community is shown below:

    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          |IPSecSA SubType| Flags(1 octet)|IPSecSA ID-Type|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                   IPsec Tunnel ID (4 octets)                  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      Figure 3: Redirect to Ind-ID Ext Community for IPSec Tunnel

   Where

   Type = 0x49 (to be assigned by IANA): Non-Transitive FlowSpec
   Redirect to Indirection-ID Extended Community for IPSec Tunnel
   ID.

   [Note: Type = 0x09 for Transitive FlowSpec Redirect to
   Indirection-ID Extended Community can also be used for
   Hierarchical deployment, where the FlowSpec Update needs to be
   propagated]

   IPSec SA Sub-Type: 1 octet, its value (TBD) will be assigned by
   IANA to indicate the ID carried by the Extended Community is
   IPsec SA ID. Assuming the IPsec SA is pre-established, its
   Security Association (SA) ID is within a single administrative
   domain a globally unique identifier. The allocation and
   establishment of the IPsec SA among peers is outside scope of
   the document.

   Flags: Same as that defined in [Flowspec-path-redirect].

   IPSec SA ID-Type: 1 octet value. Here are the new values needed
   for IPsec IPv4 tunnel (to be assigned by IANA)

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     v1 -  Inner Encap type = IPSec+GRE

     v2 -  Inner Encap type = IPSec+Vxlan

6. IANA Considerations

   This draft needs an IANA code point allocation for the Non-
   Transitive FlowSpec Redirect to Indirection-ID Extended
   Community.

     Type: Non-Transitive FlowSpec Redirect to Indirection-ID
     Extended Community for IPSec Tunnel ID.

     IPsec SA Sub-Type:

     IPSec SA ID-Type:
      v1 -  Inner encap type = IPSec+GRE
      v2 -  Inner encap type = IPSec+Vxlan

7. Security Considerations

    TBD.

8. Contributors

   The following people have contributed to this document.

9. References

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9.1. Normative References

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

   [RFC8955] C. Loibl, et al, "Dissemination of Flow specification
             Rules", Dec 2020.

   [RFC8956] C. Loibl, et, al, "Dissemination of Flow
             Specification Rules for IPv6".  Dec 2020.

9.2. Informative References

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

   [Flowspec-path-redirect] G. Van De Velde, et al, "Flowspec
   Indirection-id Redirect", draft-ietf-idr-flowspec-path-
   redirect-11, March 2020

   [SRv6-Flowspec-path-redirect] G. Van De Velde, et al, "Flowspec
   Indirection-id Redirect for SRv6], draft-ietf0-idr-srv6-
   flowspec-path-redirect-05, Jan. 2021

   [TN-AWARE-MOBILITY] U. Chunduri, et al, "Mobility aware
   Transport Network Slicing for 5G", draft-ietf-dmm-tn-aware-
   mobility-07, July 2023

   [TN-AWARE-MOBILITY-EXT] K. majumdar, et al, "Extension of
   Transport Aware Mobility in Data Network", draft-mcd-rtgwg-
   extension-tn-aware-mobility-06, July 2023

   [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-ietf-bess-bgp-sdwan-usage-14, July
   2023

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   [SDWAN-Edge-Discover] L. Dunber, et al, "BGP UPDATE for SDWAN
   Edge Discovery", draft-ietf-idr-sdwan-edge-discovery-10, June
   2023

10. Acknowledgments

   TBD.

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

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Authors' Addresses

   Linda Dunbar
   Futurewei
   2330 Central Expressway
   Santa Clara, CA  95050

   Email: linda.dunbar@futurewei.com

   Kausik Majumdar
   Microsoft
   Email: kmajumdar@microsoft.com

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

   Email: umac.ietf@gmail.com

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