BGP Dissemination of FlowSpec for Transport Aware Mobility
draft-dmc-idr-flowspec-tn-aware-mobility-00
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| Document | Type | Active Internet-Draft (individual) | |
|---|---|---|---|
| Authors | Linda Dunbar , Kausik Majumdar , Uma Chunduri | ||
| Last updated | 2021-07-07 | ||
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draft-dmc-idr-flowspec-tn-aware-mobility-00
RTG Working Group L. Dunbar
Internet Draft Futurewei
Intended status: Standard track K. Majumdar
Expires: October 7, 2022 CommScope
U. Chunduri
Intel
July 7, 2021
BGP Dissemination of FlowSpec for Transport Aware Mobility
draft-dmc-idr-flowspec-tn-aware-mobility-00
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
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provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on April 23, 2021.
Copyright Notice
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Table of Contents
1. Introduction.................................................. 2
2. Conventions used in this document............................. 3
3. TN-Aware matching conditions.................................. 4
4. Redirect a flow over underlay tunnels......................... 6
5. Indirection-id Community for IPv4 IPsec Tunnel................ 7
6. IANA Considerations........................................... 9
7. Security Considerations....................................... 9
8. Contributors.................................................. 9
9. References.................................................... 9
9.1. Normative References..................................... 9
9.2. Informative References.................................. 10
10. Acknowledgments............................................. 10
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 used to
differentiate SLAs of flows from UPFs [EXT-TN-AWARE-Mobility].
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The Ingress PE, which is either a function inside UPF or 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 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., GTP header being decapsulated, carrying 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 |
+---+---+---+---+---+---+---+---+
Where len ==0, meaning two bytes of value [i] follows the
Numeric_op1 and two bytes of value [j] follows the Numberic_op2.
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The "numeric_op3" and "numeric_op4" are for comparing the source
and destination addresses of the UE traffic.
4. Redirect a flow over underlay tunnels
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.
The Transitive Extended Community described by [Flowspec-path-
redirect] and [SRv6-flowspec-path-redirect] can be extended to
steer flows to hybrid underlay paths.
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:
+-----------+ +----+{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 URLLC
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 \
\
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---------->
+------+----------+-------+-----+----------+
| Data | Inner IP | GTP-U | UDP | Outer IP |
+------+----------+-------+-----+----------+
---------->
+------+----------+------------------+
| Data | Inner IP | Transport Header |
+------+----------+------------------+
Figure 2: TN Aware Mobility Traffic Mapping to FS Redirect Path
5. Indirection-id Community for IPv4 IPsec Tunnel
This section defines a new sub-type value for in "FlowSpec
Redirect to indirection-id Extended Community". The format of this
extended community with the new sub-type value is show 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 |Sub-Type (TBD) | Flags(1 octet)| ID-Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPsec redirection ID (16 octets) |
~ ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3: FlowSpec IPsec Redirection ID Sub-TLV
Where
Type: 1 octet, defined in [flowspec-path-redirect].
Sub-Type: 1 octet, its value (TBD) will be assigned by IANA.
Flags: Same as that defined in [flowspec-path-redirect].
ID-Type: 1 octet value. Here is the new value needed for IPsec
IPv4 tunnel.
6 - IPsec SA ID (Assuming the IPsec SA is pre-established, its
Security Association (SA) ID is within a single administrative
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domain a globally unique identifier. The allocation and
establishment of the IPsec SA among peers is outside scope of
the document).
The IPsec-SA-ID sub-TLV specified by [SDWAN-Edge-Discovery] can
be placed in the IPsec Indirection ID field in Figure 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= IPsec-SA-ID subTLV | Length (2 Octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPsec SA Identifier #1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPsec SA Identifier #2 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
This draft continues using the Context Types specified by
[Flowspec-RedirectSRv6]:
0 - Localised ID (The flowspec client uses the received
indirection-id to lookup forwarding information within the
localised indirection-id table. The allocation and programming
of the localised indirection-id table is outside scope of the
document)
1 - Node ID with SID/index in MPLS-based Segment Routing (This
means the indirection-id is mapped to an MPLS label using the
index as a global offset in the SID/label space)
2 - Node ID with SID/label in MPLS-based Segment Routing (This
means the indirection-id is mapped to an MPLS label using the
indirection-id as global label)
3 - Binding Segment ID with SID/index in MPLS-based Segment
Routing (This means the indirection-id is mapped to an MPLS
binding label using the indirection-id as index for global
offset in the SID/label space).
4 - Binding Segment ID with SID/label in MPLS-based Segment
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Routing (This means indirection-id is mapped to an MPLS binding
label using the indirection-id as global label).
5 - Tunnel ID (Tunnel ID is within a single administrative
domain a globally unique tunnel identifier. The allocation and
programming of the Tunnel ID within the localized indirection-id
table is outside scope of the document)
6. IANA Considerations
This draft needs an IANA code point allocation for
Sub-Type: IPsec SA.
A request for any IANA code point allocation would be submitted.
7. Security Considerations
TBD.
8. Contributors
The following people have contributed to this document.
9. References
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.
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[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, "Transport Network aware
Mobility for 5G", draft-clt-dmm-tn-aware-mobility-07, April 2021
[TN-AWARE-MOBILITY-EXT] K. majumdar, et al, "Extension of
Transport Aware Mobility in Data Network", draft-mcd-rtgwg-
extension-tn-aware-mobility-01, May 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
[SDWAN-Edge-Discover] L. Dunber, et al, "BGP UPDATE for SDWAN Edge
Discovery", draft-dunbar-idr-sdwan-edge-discovery-04, April 2021
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
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
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