Usage of BGP-LS-SPF in Multi-segment SD-WAN
draft-sheng-lsvr-bgp-spf-for-sdwan-02
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| Document | Type | Active Internet-Draft (individual) | |
|---|---|---|---|
| Authors | Cheng Sheng , Hang Shi | ||
| Last updated | 2024-07-08 | ||
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draft-sheng-lsvr-bgp-spf-for-sdwan-02
LSVR C. Sheng
Internet-Draft H. Shi, Ed.
Intended status: Standards Track Huawei
Expires: 9 January 2025 8 July 2024
Usage of BGP-LS-SPF in Multi-segment SD-WAN
draft-sheng-lsvr-bgp-spf-for-sdwan-02
Abstract
This document introduces the usage of BGP-LS-SPF protocol in multi-
segment SD-WAN scenarios. It allows SD-WAN tunnels to be published
as logical links, which can cross the internet, MPLS networks, and
various operator network. The BGP-LS-SPF protocol can construct an
overlay network topology for logical links and physical links across
these heterogeneous networks, and calculate the reachability routes
of overlay network nodes based on this topology.
Status of This Memo
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This Internet-Draft will expire on 9 January 2025.
Copyright Notice
Copyright (c) 2024 IETF Trust and the persons identified as the
document authors. All rights reserved.
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This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents (https://trustee.ietf.org/
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Please review these documents carefully, as they describe your rights
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
2.1. Requirements Language . . . . . . . . . . . . . . . . . . 3
3. Usage of BGP-LS-SPF in Multi-segment SD-WAN . . . . . . . . . 3
4. Extensions to BGP-LS . . . . . . . . . . . . . . . . . . . . 5
4.1. SDWAN Protocol ID . . . . . . . . . . . . . . . . . . . . 5
4.2. Node Descriptor Sub-tlv . . . . . . . . . . . . . . . . . 5
4.3. Link-Type TLV . . . . . . . . . . . . . . . . . . . . . . 5
5. Security Considerations . . . . . . . . . . . . . . . . . . . 6
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
6.1. BGP-LS Protocol-IDs . . . . . . . . . . . . . . . . . . . 7
6.2. BGP-LS TLVs . . . . . . . . . . . . . . . . . . . . . . . 7
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 7
7.1. Normative References . . . . . . . . . . . . . . . . . . 7
7.2. Informative References . . . . . . . . . . . . . . . . . 8
Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 8
Appendix B. Contributors . . . . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8
1. Introduction
As pointed out in [I-D.draft-ietf-rtgwg-net2cloud-problem-statement],
enterprises are migrating their workloads to cloud service. The
enterprise branch interconnection and enterprise site to cloud DC
connection may cross heterogeneous network such as operator networks,
enterprise-owned backbone networks or direct connection lines.
For large enterprises to access the cloud service and interconnect
their branches, a PoP GWs network can be built to provide multi-
cloud, multi-tenant, and multi-branch interconnection. Depending on
the geographical distribution of the enterprise branches, the PoP GWs
network may be a cross-regional or even a global network. The PoP GW
can be connected to the operator network or the enterprise-owned
backbone network. The PoP GWs devices can also be directly connected
through dedicated lines.
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According to [I-D.draft-ietf-bess-bgp-sdwan-usage], SD-WAN tunnels
can be established between two GWs devices connected to the operator
network, MPLS VPN network, or internet network through the WAN ports
of the two PoP GWs devices. All GWs are under the control of one BGP
instance. [I-D.draft-ietf-idr-sdwan-edge-discovery] defines the
mechanism for SD-WAN edges to discover each other's properties via
BGP update through RR. This allows the interconnection between
enterprise branches and multi-cloud to pass through multiple SD-WAN
tunnels or direct connection lines, as shown in Figure 1.
This draft provides a way to use the BGP-LS-SPF protocol to collect
the identification of PoP GW device node and the topology of SD-WAN
tunnel and direct connection lines. In this way, each PoP GW device
can learn the PoP GWs network topology, and calculate the route to
any other PoP GW.
2. Terminology
This specification reuses terms defined in Section 5.2 of
[I-D.draft-ietf-lsvr-bgp-spf] including BGP-LS-SPF Node NLRI, BGP-LS-
SPF Link NLRI, Dijkstra Algorithm.
* PoP GW: Point of Presence Gateway
* SD-WAN: Software Defined Wide Area Network. In this document,
"SD-WAN" refers to policy-driven transporting IP packets over
multiple different underlay networks to get better WAN bandwidth
management, visibility and control.
* RR: Route Reflector
* Cloud DC: Off-Premise Data Centers that usually host applications
and workload owned by different organizations or tenants.
2.1. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in
BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
3. Usage of BGP-LS-SPF in Multi-segment SD-WAN
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+ - - - +- - - - - - - - - - - -|RR| - - - - - - - - - -+ - - - - +
| | | | |
| +--|--+ +--|--+ +--|--+ |
| | GW1 |------------------| GW2 | -Physical link-| GW3 | |
| +--|--+10.1.1.1 20.1.1.1+-----+ +--|--+ |
| | SD-WAN Tunnel / Physical |30.1.1.1 |
| | ---------------- Link | |
| | / over Internet |40.1.1.1 |
| +--|--+ +--|--+ |
|+--+| GW5 |---------SD-WAN Tunnel over MPLS---------| GW4 |+-----+
+--|--+ +--|--+
| |
+ - -+ + - -+ + - -+ + - -+
|User|---|CPE1| |CPE2|---|APPs|
+ - -+ + - -+ + - -+ + - -+
Figure 1: PoP GWs network
As shown in Figure 1, GW1, GW2, GW5 are connected to the same
internet/ISP network. The GW2 and GW3 are connected through direct
dedicated links. GW5 and GW4 are connected by MPLS VPN. BGP-SD-WAN
neighbors are established between GWs through RR. BGP-LS-SPF
neighbors are established between each GW and RR. SD-WAN tunnel
links are established between GWs through BGP-SD-WAN neighbors
reflecting SD-WAN routes(see
[I-D.draft-ietf-idr-sdwan-edge-discovery]), as shown in the SD-WAN
Tunnel between GW1 and GW2 with WAN port IP addresses of 10.1.1.1 and
20.1.1.1, respectively. GW nodes reflect the SD-WAN tunnel topology
information to all GWs, including dedicated line-connected GWs,
through BGP-LS-SPF neighbors with RR.
GW2-GW3-GW4 are connected through dedicated lines. BGP-LS-SPF
neighbors are established between GWs through dedicated lines, and
also between GWs and RR. The BGP-LS-SPF neighbors between dedicated
lines are used to discover the topology information of the dedicated
lines, such as the direct link with port IP addresses of 30.1.1.1 and
40.1.1.1 between GW3 and GW4 shown in the figure. The dedicated line
topology information is reflected to all GWs, including SD-WAN
tunnel-connected GWs, through BGP-LS-SPF neighbors with RR.
BGP-LS-SPF can be used in two scenarios in Multi-segment SD-WAN: 1.
TE. When TE is used, SLA of all SD-WAN tunnels will be collected to
calculate shortest path. The protocol ID of BGP-LS is BGP. The BGP-
LS-SPF LINK NLRI is used to carry the two endpoint IP address of the
SD-WAN tunnel or dedicated lines. The BGP-LS-SPF NODE NLRI is used
to carry PoP GW device node identification. 2. BE. When BE is used,
only reachability of a SD-WAN site is collected. An SD-WAN site may
contains multiple GWs. There is no need to collect the SLA of every
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SD-WAN tunnels between two sites. In this case, a new BGP-LS
Protocol-ID is used and new Node Descriptor sub-tlv is defined to
carry the site ID.
In both scenarios, BGP-LS-SPF LINK NLRI and NODE NLRI are advertised
to other GWs through the RR. In this way, all GW learns the topology
of whole PoP GWs network and can calculate the next hop to any other
GW using Dijkstra Algorithm.
4. Extensions to BGP-LS
4.1. SDWAN Protocol ID
This document specifies the advertisement of SDWAN topology
information via BGP-LS-SPF Link NLRI type and Node NLRI type, which
requires use of a new BGP-LS Protocol-ID (value 10). The use of a
new Protocol-ID allows separation and differentiation between the
BGP-LS NLRIs carrying SDWAN topology information from the BGP-LS
NLRIs carrying other link-state information defined in [RFC9552].
4.2. Node Descriptor Sub-tlv
This document introduces a new Node Descriptor Sub-TLV to carry the
SDWAN Site ID to identify an SDWAN site. A site may contains
multiple GWs. This field has the same meaning of SD-WAN-Color in
Section 6.1 of [I-D.draft-ietf-idr-sdwan-edge-discovery],
representing a group of tunnels terminated at SD-WAN GWs co-located
at the site.
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 | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Site-id |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: Node Descriptor Sub-TLV Format
4.3. Link-Type TLV
The link could be Overlay link (Such as Internet, MPLS, LTE etc.,)
and Underlay/Physical link (Such as Dedicated line, Direct link
etc.,). Different customer may require different types of link. For
example, FinTech customer has very high security requirement and
would like to exclude Internet and LTE, only use MPLS or Dedicated
line; some customer only wants to use the Dedicated line/Direct link
to get the highest quality path; some customer prefers to use LTE
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only as backup link to save the cost. The calculation of these
customized SD-WAN path needs to include or exclude one or more
specific link types, therefore, when SD-WAN link information is
advertised through BGP-LS-SPF Link NLRI, the SD-WAN link type needs
to be explicitly indicated.
In this document, a new BGP-LS-SPF Attribute TLV of the BGP-LS-SPF
Link NLRI is added to identify a SD-WAN link type, called Link-Type
TLV. The format of the Link-Type TLV is 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Link-Type |
+-+-+-+-+-+-+-+-+
Figure 3: Link-Type TLV Format
where: Type: TBA
Length: Specifies the length of the value field (i.e., not including
Type and Length fields) in terms of octets. The value MUST be 1.
Link-Type:
* 0: Reserved
* 1: Physical/Dedicated Line/Direct link
* 2: Internet
* 3: MPLS
* 4: LTE
This BGP-LS-SPF Attribute TLV of the BGP-LS-SPF Link NLRI is defined
to indicate the Link-Type of the SD-WAN link.
5. Security Considerations
This document does not introduce any new security considerations.
6. IANA Considerations
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6.1. BGP-LS Protocol-IDs
IANA maintains a registry called "BGP-LS Protocol-IDs" in the "Border
Gateway Protocol - Link State (BGP-LS) Parameters" registry group.
This document requests IANA to allocate the following Protocol-ID
codepoint:
+=============+==================================+===============+
| Protocol ID | NLRI information source protocol | Reference |
+=============+==================================+===============+
| 10 | SDWAN | this document |
+-------------+----------------------------------+---------------+
Table 1
6.2. BGP-LS TLVs
IANA maintains a registry called "BGP-LS NLRI and Attribute TLVs" in
the "Border Gateway Protocol - Link State (BGP-LS) Parameters"
registry group.
This document requests IANA to allocate the following TLV codepoint:
+================+========================+===============+
| TLV Code Point | Description | Reference |
+================+========================+===============+
| TBD | SDWAN Node Descriptors | this document |
+----------------+------------------------+---------------+
| TBD | Link-Type | this document |
+----------------+------------------------+---------------+
Table 2
7. References
7.1. Normative References
[I-D.draft-ietf-bess-bgp-sdwan-usage]
Dunbar, L., Sajassi, A., Drake, J., Najem, B., and S.
Hares, "BGP Usage for SD-WAN Overlay Networks", Work in
Progress, Internet-Draft, draft-ietf-bess-bgp-sdwan-usage-
23, 29 April 2024, <https://datatracker.ietf.org/doc/html/
draft-ietf-bess-bgp-sdwan-usage-23>.
[I-D.draft-ietf-idr-sdwan-edge-discovery]
Dunbar, L., Majumdar, K., Hares, S., Raszuk, R., and V.
Kasiviswanathan, "BGP UPDATE for SD-WAN Edge Discovery",
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Work in Progress, Internet-Draft, draft-ietf-idr-sdwan-
edge-discovery-13, 4 June 2024,
<https://datatracker.ietf.org/doc/html/draft-ietf-idr-
sdwan-edge-discovery-13>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/rfc/rfc2119>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/rfc/rfc8174>.
[RFC9552] Talaulikar, K., Ed., "Distribution of Link-State and
Traffic Engineering Information Using BGP", RFC 9552,
DOI 10.17487/RFC9552, December 2023,
<https://www.rfc-editor.org/rfc/rfc9552>.
7.2. Informative References
[I-D.draft-ietf-rtgwg-net2cloud-problem-statement]
Dunbar, L., Malis, A. G., Jacquenet, C., Toy, M., and K.
Majumdar, "Dynamic Networks to Hybrid Cloud DCs: Problems
and Mitigation Practices", Work in Progress, Internet-
Draft, draft-ietf-rtgwg-net2cloud-problem-statement-39, 15
April 2024, <https://datatracker.ietf.org/doc/html/draft-
ietf-rtgwg-net2cloud-problem-statement-39>.
[I-D.draft-ietf-lsvr-bgp-spf]
Patel, K., Lindem, A., Zandi, S., and W. Henderickx, "BGP
Link-State Shortest Path First (SPF) Routing", Work in
Progress, Internet-Draft, draft-ietf-lsvr-bgp-spf-31, 17
June 2024, <https://datatracker.ietf.org/doc/html/draft-
ietf-lsvr-bgp-spf-31>.
Appendix A. Acknowledgements
The authors would like to thank Donglei Pang for his contribution to
the document.
Appendix B. Contributors
Shunwan Zhuang Huawei Email: zhuangshunwan@huawei.com
Authors' Addresses
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Cheng Sheng
Huawei
Beiqing Road
Beijing
Email: shengcheng@huawei.com
Hang Shi (editor)
Huawei
Beiqing Road
Beijing
China
Email: shihang9@huawei.com
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