draft-ietf-lsvr-applicability-04.txt   draft-ietf-lsvr-applicability-05.txt 
LSVR K. Patel LSVR K. Patel
Internet-Draft Arrcus, Inc. Internet-Draft Arrcus, Inc.
Intended status: Informational A. Lindem Intended status: Informational A. Lindem
Expires: May 5, 2020 Cisco Systems Expires: September 25, 2020 Cisco Systems
S. Zandi S. Zandi
G. Dawra G. Dawra
Linkedin Linkedin
November 2, 2019 March 24, 2020
Usage and Applicability of Link State Vector Routing in Data Centers Usage and Applicability of Link State Vector Routing in Data Centers
draft-ietf-lsvr-applicability-04 draft-ietf-lsvr-applicability-05
Abstract Abstract
This document discusses the usage and applicability of Link State This document discusses the usage and applicability of Link State
Vector Routing (LSVR) extensions in data center networks utilizing Vector Routing (LSVR) extensions in data center networks utilizing
CLOS or Fat-Tree topologies. The document is intended to provide a CLOS or Fat-Tree topologies. The document is intended to provide a
simplified guide for the deployment of LSVR extensions. simplified guide for the deployment of LSVR extensions.
Status of This Memo Status of This Memo
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/. Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on May 5, 2020. This Internet-Draft will expire on September 25, 2020.
Copyright Notice Copyright Notice
Copyright (c) 2019 IETF Trust and the persons identified as the Copyright (c) 2020 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
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the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
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6. LSVR Applicability to CLOS Networks . . . . . . . . . . . . . 5 6. LSVR Applicability to CLOS Networks . . . . . . . . . . . . . 5
6.1. Usage of BGP-LS SPF SAFI . . . . . . . . . . . . . . . . 5 6.1. Usage of BGP-LS SPF SAFI . . . . . . . . . . . . . . . . 5
6.1.1. Relationship to Other BGP AFI/SAFI Tuples . . . . . . 6 6.1.1. Relationship to Other BGP AFI/SAFI Tuples . . . . . . 6
6.2. Peering Models . . . . . . . . . . . . . . . . . . . . . 6 6.2. Peering Models . . . . . . . . . . . . . . . . . . . . . 6
6.2.1. Sparse Peering Model . . . . . . . . . . . . . . . . 6 6.2.1. Sparse Peering Model . . . . . . . . . . . . . . . . 6
6.2.2. Bi-Connected Graph Heuristic . . . . . . . . . . . . 7 6.2.2. Bi-Connected Graph Heuristic . . . . . . . . . . . . 7
6.3. BGP Spine/Leaf Topology Policy . . . . . . . . . . . . . 7 6.3. BGP Spine/Leaf Topology Policy . . . . . . . . . . . . . 7
6.4. BGP Peer Discovery Requirements . . . . . . . . . . . . . 8 6.4. BGP Peer Discovery Requirements . . . . . . . . . . . . . 8
6.5. BGP Peer Discovery . . . . . . . . . . . . . . . . . . . 9 6.5. BGP Peer Discovery . . . . . . . . . . . . . . . . . . . 9
6.5.1. BGP Peer Discovery Alternatives . . . . . . . . . . . 9 6.5.1. BGP Peer Discovery Alternatives . . . . . . . . . . . 9
6.5.2. Data Center Interconnect (DCI) Applicability . . . . 9 6.5.2. BGP IPv6 Simplified Peering . . . . . . . . . . . . . 9
6.5.3. BGP-LS SPF Topology Visibility for Management . . . . 10
6.5.4. Data Center Interconnect (DCI) Applicability . . . . 10
7. Non-CLOS/FAT Tree Topology Applicability . . . . . . . . . . 10 7. Non-CLOS/FAT Tree Topology Applicability . . . . . . . . . . 10
8. Non-Transit Node Capability . . . . . . . . . . . . . . . . . 10 8. Non-Transit Node Capability . . . . . . . . . . . . . . . . . 10
9. BGP Policy Applicability . . . . . . . . . . . . . . . . . . 10 9. BGP Policy Applicability . . . . . . . . . . . . . . . . . . 11
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11
11. Security Considerations . . . . . . . . . . . . . . . . . . . 11 11. Security Considerations . . . . . . . . . . . . . . . . . . . 11
12. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 11 12. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 11
13. References . . . . . . . . . . . . . . . . . . . . . . . . . 11 13. References . . . . . . . . . . . . . . . . . . . . . . . . . 11
13.1. Normative References . . . . . . . . . . . . . . . . . . 11 13.1. Normative References . . . . . . . . . . . . . . . . . . 11
13.2. Informative References . . . . . . . . . . . . . . . . . 11 13.2. Informative References . . . . . . . . . . . . . . . . . 12
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 13 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 13
1. Introduction 1. Introduction
This document complements [I-D.ietf-lsvr-bgp-spf] by discussing the This document complements [I-D.ietf-lsvr-bgp-spf] by discussing the
applicability of the technology in a simple and fairly common applicability of the technology in a simple and fairly common
deployment scenario, which is described in Section 4. deployment scenario, which is described in Section 4.
After describing the deployment scenario, Section 5 will describe the After describing the deployment scenario, Section 5 will describe the
reasons for BGP modifications for such deployments. reasons for BGP modifications for such deployments.
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beyond the scope of this document. However, it would be reasonable beyond the scope of this document. However, it would be reasonable
to assume a technique where the TOR switches can be identified and to assume a technique where the TOR switches can be identified and
the number of hops to the TOR is used to determine the direction. the number of hops to the TOR is used to determine the direction.
In this heuristic, BGP speakers allow passive session establishment In this heuristic, BGP speakers allow passive session establishment
for southbound BGP sessions. For northbound sessions, BGP speakers for southbound BGP sessions. For northbound sessions, BGP speakers
will attempt to maintain two northbound BGP sessions with different will attempt to maintain two northbound BGP sessions with different
switches (in data center fabrics there is normally a single layer-3 switches (in data center fabrics there is normally a single layer-3
connection anyway). For east-west sessions, passive BGP session connection anyway). For east-west sessions, passive BGP session
establishment is allowed. However, BGP speaker will never actively establishment is allowed. However, BGP speaker will never actively
establish an east-west BGP session unless it can't establish two establish an east-west BGP session unless it cannot establish two
northbound BGP sessions. northbound BGP sessions.
6.3. BGP Spine/Leaf Topology Policy 6.3. BGP Spine/Leaf Topology Policy
One of the advantages of using BGP SPF as the underlay protocol is One of the advantages of using BGP SPF as the underlay protocol is
that BGP policy can be applied at any level. In Spine/Leaf that BGP policy can be applied at any level. In Spine/Leaf
topologies, it is not necessary to advertise BGP-LS NLRI received by topologies, it is not necessary to advertise BGP-LS NLRI received by
leaves northbound to the spine nodes at the level above. If a common leaves northbound to the spine nodes at the level above. If a common
AS is used for the spine nodes, this can easily be accomplished with AS is used for the spine nodes, this can easily be accomplished with
EBGP and a simple policy to filter advertisements from the leaves to EBGP and a simple policy to filter advertisements from the leaves to
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BGP SPF in data centers. The BGP discovery mechanism should BGP SPF in data centers. The BGP discovery mechanism should
discovery both peer addresses and endpoints for BFD discovery. discovery both peer addresses and endpoints for BFD discovery.
Additionally, it would be great if there were a heuristic for Additionally, it would be great if there were a heuristic for
determining whether the peer is at a tier above or below the determining whether the peer is at a tier above or below the
discovering BGP speaker (refer to Section 6.2.2). discovering BGP speaker (refer to Section 6.2.2).
The BGP discovery mechanisms under consideration are The BGP discovery mechanisms under consideration are
[I-D.acee-idr-lldp-peer-discovery], [I-D.acee-idr-lldp-peer-discovery],
[I-D.xu-idr-neighbor-autodiscovery], and [I-D.ietf-lsvr-l3dl]. [I-D.xu-idr-neighbor-autodiscovery], and [I-D.ietf-lsvr-l3dl].
6.5.2. Data Center Interconnect (DCI) Applicability 6.5.2. BGP IPv6 Simplified Peering
In order to conserve IPv4 address space and simplify operations, BGP-
LS SPF routers in CLOS/Fat-Tree deployments can use IPv6 addresses as
peer address. For IPv4 address families, IPv6 peering as specified
in [RFC5549] can be deployed to avoid configuring IPv4 addresses on
BGP-LS SPF router interfaces. When this is done, dynamic discovery
mechanisms, as described in Section 6.5, can used to learn the global
or link-local IPv6 peer addresses and IPv4 addresses need not be
configured on these interfaces. If IPv6 link-local peering is used,
then configuration of IPv6 global addresses is also not required and
these IPv6 link-local addresses must then be advertised in the BGP-LS
Link Descriptor IPv6 Address TLV (262) [RFC7752].
6.5.3. BGP-LS SPF Topology Visibility for Management
Irrespective of whether or not BGP-LS SPF is used for route
calculation, the BGP-LS SPF route advertisements can be used to
periodically construct the CLOS/FAT Tree topology. This is
especially useful in deployments where an IGP is not used and the
base BGP-LS routes [RFC7752] are not available. The resultant
topology visibility can then be used for troubleshooting and
consistency checking. This would normally be done on a central
controller but distributed consistency checking is not precluded.
The precise algorithms and heuristics, as well as, the complete set
of management applications is beyond the scope of this document.
6.5.4. Data Center Interconnect (DCI) Applicability
Since BGP SPF is to be used for the routing underlay and DCI gateway Since BGP SPF is to be used for the routing underlay and DCI gateway
boxes typically have direct or very simple connectivity, BGP external boxes typically have direct or very simple connectivity, BGP external
sessions would typically not include the BGP SPF SAFI. sessions would typically not include the BGP SPF SAFI.
7. Non-CLOS/FAT Tree Topology Applicability 7. Non-CLOS/FAT Tree Topology Applicability
The BGP SPF extensions [I-D.ietf-lsvr-bgp-spf] can be used in other The BGP SPF extensions [I-D.ietf-lsvr-bgp-spf] can be used in other
topologies and avail the inherent convergence improvements. topologies and avail the inherent convergence improvements.
Additionally, sparse peering techniques may be utilized Section 6.2. Additionally, sparse peering techniques may be utilized Section 6.2.
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[I-D.ietf-lsr-dynamic-flooding] may be employed. One potential [I-D.ietf-lsr-dynamic-flooding] may be employed. One potential
deployment would be the underlay for a Service Provider (SP) backbone deployment would be the underlay for a Service Provider (SP) backbone
where usage of a single protocol, i.e., BGP, is desired. where usage of a single protocol, i.e., BGP, is desired.
8. Non-Transit Node Capability 8. Non-Transit Node Capability
In certain scenarios, a BGP node wishes to participate in the BGP SPF In certain scenarios, a BGP node wishes to participate in the BGP SPF
topology but never be used for transit traffic. These in include topology but never be used for transit traffic. These in include
situations where a server wants to make application services situations where a server wants to make application services
available to clients homed at subnets throughout the BGP SPF domain available to clients homed at subnets throughout the BGP SPF domain
but doesn't ever want to be used as a router (i.e., carry transit but does not ever want to be used as a router (i.e., carry transit
traffic). Another specific instance is where a controller is traffic). Another specific instance is where a controller is
resident on a server and direct connectivity to the controller is resident on a server and direct connectivity to the controller is
required throughout the entire domain. This can readily be required throughout the entire domain. This can readily be
accomplished using the BGP-LS Node NLRI Attribute SPF Status TLV as accomplished using the BGP-LS Node NLRI Attribute SPF Status TLV as
described in [I-D.ietf-lsvr-bgp-spf]. described in [I-D.ietf-lsvr-bgp-spf].
9. BGP Policy Applicability 9. BGP Policy Applicability
Existing BGP policy including aggregation and prefix filtering may be Existing BGP policy including aggregation and prefix filtering may be
used in conjunction with the BGP-LS SPF SAFI. When aggregation used in conjunction with the BGP-LS SPF SAFI. When aggregation
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No IANA updates are requested by this document. No IANA updates are requested by this document.
11. Security Considerations 11. Security Considerations
This document introduces no new security considerations above and This document introduces no new security considerations above and
beyond those already specified in the [RFC4271] and beyond those already specified in the [RFC4271] and
[I-D.ietf-lsvr-bgp-spf]. [I-D.ietf-lsvr-bgp-spf].
12. Acknowledgements 12. Acknowledgements
The authors would like to thank Alvaro Retana and Yan Filyurin for The authors would like to thank Alvaro Retana, Yan Filyurin, and
the review and comments. Boris Hassanov for their review and comments.
13. References 13. References
13.1. Normative References 13.1. Normative References
[I-D.ietf-lsvr-bgp-spf] [I-D.ietf-lsvr-bgp-spf]
Patel, K., Lindem, A., Zandi, S., and W. Henderickx, Patel, K., Lindem, A., Zandi, S., and W. Henderickx,
"Shortest Path Routing Extensions for BGP Protocol", "Shortest Path Routing Extensions for BGP Protocol",
draft-ietf-lsvr-bgp-spf-06 (work in progress), September draft-ietf-lsvr-bgp-spf-07 (work in progress), December
2019. 2019.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>. <https://www.rfc-editor.org/info/rfc2119>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>. May 2017, <https://www.rfc-editor.org/info/rfc8174>.
13.2. Informative References 13.2. Informative References
[CLOS] "A Study of Non-Blocking Switching Networks", The Bell [CLOS] "A Study of Non-Blocking Switching Networks", The Bell
System Technical Journal, Vol. 32(2), DOI System Technical Journal, Vol. 32(2), DOI
10.1002/j.1538-7305.1953.tb01433.x, March 1953. 10.1002/j.1538-7305.1953.tb01433.x, March 1953.
[I-D.acee-idr-lldp-peer-discovery] [I-D.acee-idr-lldp-peer-discovery]
Lindem, A., Patel, K., Zandi, S., Haas, J., and X. Xu, Lindem, A., Patel, K., Zandi, S., Haas, J., and X. Xu,
"BGP Logical Link Discovery Protocol (LLDP) Peer "BGP Logical Link Discovery Protocol (LLDP) Peer
Discovery", draft-acee-idr-lldp-peer-discovery-05 (work in Discovery", draft-acee-idr-lldp-peer-discovery-06 (work in
progress), July 2019. progress), November 2019.
[I-D.ietf-lsr-dynamic-flooding] [I-D.ietf-lsr-dynamic-flooding]
Li, T., Psenak, P., Ginsberg, L., Chen, H., Przygienda, Li, T., Psenak, P., Ginsberg, L., Chen, H., Przygienda,
T., Cooper, D., Jalil, L., and S. Dontula, "Dynamic T., Cooper, D., Jalil, L., and S. Dontula, "Dynamic
Flooding on Dense Graphs", draft-ietf-lsr-dynamic- Flooding on Dense Graphs", draft-ietf-lsr-dynamic-
flooding-03 (work in progress), June 2019. flooding-04 (work in progress), November 2019.
[I-D.ietf-lsvr-l3dl] [I-D.ietf-lsvr-l3dl]
Bush, R., Austein, R., and K. Patel, "Layer 3 Discovery Bush, R., Austein, R., and K. Patel, "Layer 3 Discovery
and Liveness", draft-ietf-lsvr-l3dl-02 (work in progress), and Liveness", draft-ietf-lsvr-l3dl-03 (work in progress),
July 2019. November 2019.
[I-D.xu-idr-neighbor-autodiscovery] [I-D.xu-idr-neighbor-autodiscovery]
Xu, X., Talaulikar, K., Bi, K., Tantsura, J., and N. Xu, X., Talaulikar, K., Bi, K., Tantsura, J., and N.
Triantafillis, "BGP Neighbor Discovery", draft-xu-idr- Triantafillis, "BGP Neighbor Discovery", draft-xu-idr-
neighbor-autodiscovery-11 (work in progress), April 2019. neighbor-autodiscovery-12 (work in progress), November
2019.
[RFC2328] Moy, J., "OSPF Version 2", STD 54, RFC 2328, [RFC2328] Moy, J., "OSPF Version 2", STD 54, RFC 2328,
DOI 10.17487/RFC2328, April 1998, DOI 10.17487/RFC2328, April 1998,
<https://www.rfc-editor.org/info/rfc2328>. <https://www.rfc-editor.org/info/rfc2328>.
[RFC4271] Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A [RFC4271] Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A
Border Gateway Protocol 4 (BGP-4)", RFC 4271, Border Gateway Protocol 4 (BGP-4)", RFC 4271,
DOI 10.17487/RFC4271, January 2006, DOI 10.17487/RFC4271, January 2006,
<https://www.rfc-editor.org/info/rfc4271>. <https://www.rfc-editor.org/info/rfc4271>.
skipping to change at page 12, line 40 skipping to change at page 13, line 16
"Neighbor Discovery for IP version 6 (IPv6)", RFC 4861, "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861,
DOI 10.17487/RFC4861, September 2007, DOI 10.17487/RFC4861, September 2007,
<https://www.rfc-editor.org/info/rfc4861>. <https://www.rfc-editor.org/info/rfc4861>.
[RFC4957] Krishnan, S., Ed., Montavont, N., Njedjou, E., Veerepalli, [RFC4957] Krishnan, S., Ed., Montavont, N., Njedjou, E., Veerepalli,
S., and A. Yegin, Ed., "Link-Layer Event Notifications for S., and A. Yegin, Ed., "Link-Layer Event Notifications for
Detecting Network Attachments", RFC 4957, Detecting Network Attachments", RFC 4957,
DOI 10.17487/RFC4957, August 2007, DOI 10.17487/RFC4957, August 2007,
<https://www.rfc-editor.org/info/rfc4957>. <https://www.rfc-editor.org/info/rfc4957>.
[RFC5549] Le Faucheur, F. and E. Rosen, "Advertising IPv4 Network
Layer Reachability Information with an IPv6 Next Hop",
RFC 5549, DOI 10.17487/RFC5549, May 2009,
<https://www.rfc-editor.org/info/rfc5549>.
[RFC5580] Tschofenig, H., Ed., Adrangi, F., Jones, M., Lior, A., and [RFC5580] Tschofenig, H., Ed., Adrangi, F., Jones, M., Lior, A., and
B. Aboba, "Carrying Location Objects in RADIUS and B. Aboba, "Carrying Location Objects in RADIUS and
Diameter", RFC 5580, DOI 10.17487/RFC5580, August 2009, Diameter", RFC 5580, DOI 10.17487/RFC5580, August 2009,
<https://www.rfc-editor.org/info/rfc5580>. <https://www.rfc-editor.org/info/rfc5580>.
[RFC5925] Touch, J., Mankin, A., and R. Bonica, "The TCP [RFC5925] Touch, J., Mankin, A., and R. Bonica, "The TCP
Authentication Option", RFC 5925, DOI 10.17487/RFC5925, Authentication Option", RFC 5925, DOI 10.17487/RFC5925,
June 2010, <https://www.rfc-editor.org/info/rfc5925>. June 2010, <https://www.rfc-editor.org/info/rfc5925>.
[RFC7752] Gredler, H., Ed., Medved, J., Previdi, S., Farrel, A., and [RFC7752] Gredler, H., Ed., Medved, J., Previdi, S., Farrel, A., and
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