Internet DRAFT - draft-dong-lsvr-bgp-spf-vtn
draft-dong-lsvr-bgp-spf-vtn
LSVR Working Group J. Dong
Internet-Draft Z. Li
Intended status: Standards Track H. Wang
Expires: April 27, 2022 Huawei Technologies
October 24, 2021
BGP SPF for Virtual Transport Network (VTN)
draft-dong-lsvr-bgp-spf-vtn-02
Abstract
A Virtual Transport Network (VTN) is a virtual underlay network which
consists of a customized network topology and a set of network
resource allocated from the physical network. In a network, multiple
VTNs can be created to meet different service requirements, and
services may be mapped to the same or different VTNs.
In networks where BGP Shortest Path First (SPF) is used to distribute
the link-state information among network nodes, the information of
VTNs needs to be distributed along with the basic network
information. This document specifies the BGP SPF mechanisms with
necessary extensions to distribute the VTN information and perform
VTN-specific path computaton.
Status of This Memo
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This Internet-Draft will expire on April 27, 2022.
Copyright Notice
Copyright (c) 2021 IETF Trust and the persons identified as the
document authors. All rights reserved.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3
2. Applicability of VTN related BGP-LS Extensions to BGP SPF . . 3
2.1. Reuse of BGP-LS TLVs for BGP SPF VTN . . . . . . . . . . 3
2.2. VTN Topology and Resource Distribution . . . . . . . . . 5
3. SPF Calculation for VTNs . . . . . . . . . . . . . . . . . . 5
4. Security Considerations . . . . . . . . . . . . . . . . . . . 6
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 6
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 6
7.1. Normative References . . . . . . . . . . . . . . . . . . 6
7.2. Informative References . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8
1. Introduction
The concept of Virtual Transport Network (VTN) is introduced in
[I-D.ietf-teas-enhanced-vpn]. A VTN is a virtual underlay network
which has customized network topology and a set of dedicated or
shared network resources. In a network, different VTNs may be
created to meet different service requirements, and services can be
mapped to the same or different VTNs.
[I-D.ietf-spring-sr-for-enhanced-vpn] describes the use of resource-
aware segments [I-D.ietf-spring-resource-aware-segments] to build SR
based VTNs. The SIDs of each VTN and the associated topology and
resource attributes need to be distributed using the control plane.
[I-D.dong-lsr-sr-enhanced-vpn] specifies the IGP mechanism and
extensions to build a set of SR based VTNs.
[I-D.dong-idr-bgpls-sr-enhanced-vpn] further specifies the BGP-LS
mechanisms and extensions to advertise the VTN information in each
domain and the VTN information on the inter-domain links to the
network controller, so that the controller could use the collected
information to build the inter-domain SR VTNs.
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In networks where BGP SPF is used to distribute the link-state
information among network nodes, the VTN information needs to be
distributed along with the basic network link state and TE
information. And comparing with the Internal Gateway Protocols
(IGPs), BGP SPF may have some advantage in supporting a relatively
large number of VTNs. This document specifies the BGP SPF mechanisms
with necessary extensions to advertise the information of VTNs. The
proposed mechanism is applicable to segment routing with MPLS data
plane (SR-MPLS), segment routing with IPv6 data plane (SRv6), and
native IPv6 data plane.
1.1. 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
BCP14 RFC 2119 [RFC2119] RFC 8174 [RFC8174] when, and only when, they
appear in all capitals, as shown here.
2. Applicability of VTN related BGP-LS Extensions to BGP SPF
2.1. Reuse of BGP-LS TLVs for BGP SPF VTN
As described in [I-D.ietf-lsvr-bgp-spf], the NLRI and TLVs of BGP-LS
can be reused by BGP SPF, this section describes the TLVs which are
defined in BGP-LS and can be reused in BGP SPF for the distribution
of VTN related information.
According to [I-D.ietf-teas-enhanced-vpn], a virtual transport
network (VTN) has a customized network topology and a set of
dedicated or shared network resources. Thus a VTN can be defined as
the combination of a set of network attributes, including the
topology attribute and the network resource attribute. A VTN is
associated with a Multi-Topology ID (MT-ID) and/or an Algorithm ID
which are used to define the VTN topology and path computation
constraints. In some cases, each VTN may be associated with a
separate MT-ID or a Flex-Algo ID. When the amount of VTNs in a
network is large, as described in
[I-D.dong-teas-enhanced-vpn-vtn-scalability], multiple VTNs may be
associated with the same topology and/or algorithm, so that the
amount of topology-specific path computation can be shared by a group
of VTNs, this could help to reduce the computation overhead in the
control plane.
[I-D.ietf-lsvr-bgp-spf] does not cover the usage of Multi-Topology or
Flex-Algo with BGP SPF. While the mechanism in this document is
based on Multi-Topology [RFC4915][RFC5120] or Flex-Algo
[I-D.ietf-lsr-flex-algo] with BGP SPF for topology and/or algorithm
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-specific link-state information distribution and path computation.
For this purpose, the Multi-topology TLV as defined in
[I-D.ietf-idr-rfc7752bis], the SR Algorithm TLV as defined [RFC9085],
and the Flex-Algo Definition TLV as defined in
[I-D.ietf-idr-bgp-ls-flex-algo] are reused for BGP SPF.
[I-D.ietf-lsvr-bgp-spf] does not explicitly describes the usage with
Segment Routing data plane. To build SR based VTN, the SR-MPLS and
SRv6 TLVs as defined in [RFC9085] and [I-D.ietf-idr-bgpls-srv6-ext]
are reused for BGP SPF.
The VTN extensions to BGP-LS as defined in
[I-D.dong-idr-bgpls-sr-enhanced-vpn] applies to BGP SPF as well.
This section lists the TLVs which are reused by BGP SPF, the detailed
format of the TLVs are described in
[I-D.dong-idr-bgpls-sr-enhanced-vpn].
The BGP-LS Attribute TLVs which are defined in
[I-D.dong-idr-bgpls-sr-enhanced-vpn] and reused with BGP-LS-SPF SAFI
are listed as below:
o Virtual Transport Network Definition (VTND) TLV: This is used to
advertise the association between the VTN and the topology ID and/
or algorithm ID. It can be carried in BGP-LS attribute associated
with a Node NLRI.
o VTN ID TLV: This is used to describe the identifiers of one or
more VTNs a link belongs to. It can be carried in BGP-LS
attribute which is associated with a Link NLRI, or it could be
carried as a sub-TLV in the L2 Bundle Member Attribute TLV.
o Link Attribute Flags TLV: This is used to specify the
characteristics of a link, its functionality is similar to the IS-
IS Link Attribute sub-TLV defined in [RFC5029]. It can be carried
in BGP-LS attribute which is associated with a Link NLRI, or it
could be carried as a sub-TLV in the L2 Bundle Member Attribute
TLV.
o VTN-specific prefix-SID TLV: This is used to advertise the prefix-
SID and its associated VTN. It can be carried in BGP-LS attribute
which is associated with a Prefix NLRI.
o VTN-specific Adj-SID TLV: This is used to advertise the adj-SID
and its associated VTN. It can be carried in BGP-LS attribute of
the associated Link NLRI.
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Further BGP-LS TLVs may be defined in
[I-D.dong-idr-bgpls-sr-enhanced-vpn], their usage with BGP SPF will
be specified in a future version of this document.
2.2. VTN Topology and Resource Distribution
In network scenarios where each VTN is associated with a unique MT-
ID, The BGP-LS mechanisms used to distribute the VTN topology and
resource information to the network controller are described in
[I-D.xie-idr-bgpls-sr-vtn-mt]. Such mechanism can be reused for the
distribution of VTN information with BGP SPF.
In network scenarios where each VTN is associated with a unique Flex-
Algo ID, The BGP-LS mechanisms used to distribute the VTN topology
and resource information to the network controller are described in
[I-D.zhu-idr-bgpls-sr-vtn-flexalgo]. Such mechanism can be reused
for the distribution of VTN information with BGP SPF.
In network scenarios where multiple VTNs are associated with the same
<topology, algorithm> tuple, while each VTN has different resource
attributes, the BGP-LS mechanisms which can be used to distribute the
VTN topology and resource information to the network controller are
described in [I-D.dong-idr-bgpls-sr-enhanced-vpn]. Such mechanism
can be reused for the distribution of VTN information with BGP SPF.
The Sequence Number TLV as defined in [I-D.ietf-lsvr-bgp-spf] MUST be
carried in the BGP-LS attribute associated with the BGP-LS-SPF NLRI.
If the Sequence-Number TLV is not received then the corresponding
Link NLRI is considered as malformed and MUST be handled as 'Treat-
as- withdraw'. An implementation MAY log an error for further
analysis.
3. SPF Calculation for VTNs
[I-D.ietf-lsvr-bgp-spf] describes the mechanisms of using the BGP-LS-
SPF Node, Link, and Prefix NLRI for shortest path computation. With
the introduction of VTN, the same mechanism is used for the shortest
path computation of each VTN. The path computation for a VTN is
based on the topology attributes and the constraints specified with
the MT-ID and/or Algorithm ID associated with the VTN. When multiple
VTNs are associated with the same topology, the result of the
shortest path computation based on that topology could be shared by
these VTNs.
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4. Security Considerations
This document introduces no additional security vulnerabilities to
BGP SPF.
The mechanism proposed in this document is subject to the same
vulnerabilities as any other protocol that relies on BGP SPF.
5. IANA Considerations
This document request no IANA actions.
6. Acknowledgments
The authors would like to thank Haibo Wang for the review and
discussion of this document.
7. References
7.1. Normative References
[I-D.dong-idr-bgpls-sr-enhanced-vpn]
Dong, J., Hu, Z., Li, Z., Tang, X., and R. Pang, "BGP-LS
Extensions for Segment Routing based Enhanced VPN", draft-
dong-idr-bgpls-sr-enhanced-vpn-03 (work in progress),
February 2021.
[I-D.ietf-idr-bgp-ls-flex-algo]
Talaulikar, K., Psenak, P., Zandi, S., and G. Dawra,
"Flexible Algorithm Definition Advertisement with BGP
Link-State", draft-ietf-idr-bgp-ls-flex-algo-07 (work in
progress), June 2021.
[I-D.ietf-idr-bgpls-srv6-ext]
Dawra, G., Filsfils, C., Talaulikar, K., Chen, M.,
Bernier, D., and B. Decraene, "BGP Link State Extensions
for SRv6", draft-ietf-idr-bgpls-srv6-ext-08 (work in
progress), June 2021.
[I-D.ietf-idr-rfc7752bis]
Talaulikar, K., "Distribution of Link-State and Traffic
Engineering Information Using BGP", draft-ietf-idr-
rfc7752bis-08 (work in progress), July 2021.
[I-D.ietf-lsvr-bgp-spf]
Patel, K., Lindem, A., Zandi, S., and W. Henderickx, "BGP
Link-State Shortest Path First (SPF) Routing", draft-ietf-
lsvr-bgp-spf-15 (work in progress), July 2021.
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[I-D.ietf-spring-resource-aware-segments]
Dong, J., Bryant, S., Miyasaka, T., Zhu, Y., Qin, F., Li,
Z., and F. Clad, "Introducing Resource Awareness to SR
Segments", draft-ietf-spring-resource-aware-segments-03
(work in progress), July 2021.
[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/info/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/info/rfc8174>.
[RFC9085] Previdi, S., Talaulikar, K., Ed., Filsfils, C., Gredler,
H., and M. Chen, "Border Gateway Protocol - Link State
(BGP-LS) Extensions for Segment Routing", RFC 9085,
DOI 10.17487/RFC9085, August 2021,
<https://www.rfc-editor.org/info/rfc9085>.
7.2. Informative References
[I-D.dong-lsr-sr-enhanced-vpn]
Dong, J., Hu, Z., Li, Z., Tang, X., Pang, R., JooHeon, L.,
and S. Bryant, "IGP Extensions for Scalable Segment
Routing based Enhanced VPN", draft-dong-lsr-sr-enhanced-
vpn-06 (work in progress), July 2021.
[I-D.dong-teas-enhanced-vpn-vtn-scalability]
Dong, J., Li, Z., Gong, L., Yang, G., Guichard, J. N.,
Mishra, G., and F. Qin, "Scalability Considerations for
Enhanced VPN (VPN+)", draft-dong-teas-enhanced-vpn-vtn-
scalability-03 (work in progress), July 2021.
[I-D.ietf-lsr-flex-algo]
Psenak, P., Hegde, S., Filsfils, C., Talaulikar, K., and
A. Gulko, "IGP Flexible Algorithm", draft-ietf-lsr-flex-
algo-17 (work in progress), July 2021.
[I-D.ietf-spring-sr-for-enhanced-vpn]
Dong, J., Bryant, S., Miyasaka, T., Zhu, Y., Qin, F., Li,
Z., and F. Clad, "Segment Routing based Virtual Transport
Network (VTN) for Enhanced VPN", draft-ietf-spring-sr-for-
enhanced-vpn-01 (work in progress), July 2021.
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[I-D.ietf-teas-enhanced-vpn]
Dong, J., Bryant, S., Li, Z., Miyasaka, T., and Y. Lee, "A
Framework for Enhanced Virtual Private Network (VPN+)
Services", draft-ietf-teas-enhanced-vpn-08 (work in
progress), July 2021.
[I-D.xie-idr-bgpls-sr-vtn-mt]
Xie, C., Li, C., Dong, J., and Z. Li, "BGP-LS with Multi-
topology for Segment Routing based Virtual Transport
Networks", draft-xie-idr-bgpls-sr-vtn-mt-03 (work in
progress), July 2021.
[I-D.zhu-idr-bgpls-sr-vtn-flexalgo]
Zhu, Y., Dong, J., and Z. Hu, "BGP-LS with Flex-Algo for
Segment Routing based Virtual Transport Networks", draft-
zhu-idr-bgpls-sr-vtn-flexalgo-01 (work in progress),
February 2021.
[RFC4915] Psenak, P., Mirtorabi, S., Roy, A., Nguyen, L., and P.
Pillay-Esnault, "Multi-Topology (MT) Routing in OSPF",
RFC 4915, DOI 10.17487/RFC4915, June 2007,
<https://www.rfc-editor.org/info/rfc4915>.
[RFC5029] Vasseur, JP. and S. Previdi, "Definition of an IS-IS Link
Attribute Sub-TLV", RFC 5029, DOI 10.17487/RFC5029,
September 2007, <https://www.rfc-editor.org/info/rfc5029>.
[RFC5120] Przygienda, T., Shen, N., and N. Sheth, "M-ISIS: Multi
Topology (MT) Routing in Intermediate System to
Intermediate Systems (IS-ISs)", RFC 5120,
DOI 10.17487/RFC5120, February 2008,
<https://www.rfc-editor.org/info/rfc5120>.
Authors' Addresses
Jie Dong
Huawei Technologies
Huawei Campus, No. 156 Beiqing Road
Beijing 100095
China
Email: jie.dong@huawei.com
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Zhenbin Li
Huawei Technologies
Huawei Campus, No. 156 Beiqing Road
Beijing 100095
China
Email: lizhenbin@huawei.com
Haibo Wang
Huawei Technologies
Huawei Campus, No. 156 Beiqing Road
Beijing 100095
China
Email: rainsword.wang@huawei.com
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