Network Working Group
Internet Engineering Task Force (IETF) K. Patel
Internet-Draft
Request for Comments: 9816 Arrcus, Inc.
Intended status:
Category: Informational A. Lindem
Expires: 27 July 2025
ISSN: 2070-1721 LabN Consulting, L.L.C.
S. Zandi
LinkedIn
G. Dawra
Linkedin
J. Dong
Huawei Technologies
23 January
July 2025
Usage and Applicability of BGP Link-State Shortest Path Routing (BGP-
SPF) in Data Centers
draft-ietf-lsvr-applicability-22
Abstract
This document discusses the usage and applicability of BGP Link-State
Shortest Path First (BGP-SPF) extensions in data center networks
utilizing Clos or Fat-Tree Fat Tree topologies. The document is intended to
provide simplified guidance for the deployment of BGP-SPF extensions.
Status of This Memo
This Internet-Draft document is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents not an Internet Standards Track specification; it is
published for informational purposes.
This document is a product of the Internet Engineering Task Force
(IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list It represents the consensus of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Not all documents valid
approved by the IESG are candidates for a maximum any level of Internet
Standard; see Section 2 of RFC 7841.
Information about the current status of six months this document, any errata,
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This Internet-Draft will expire on 27 July 2025.
https://www.rfc-editor.org/info/rfc9816.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Recommended Reading . . . . . . . . . . . . . . . . . . . . . 3
3. Common Deployment Scenario . . . . . . . . . . . . . . . . . 3
4. Justification for the BGP-SPF Extension . . . . . . . . . . . . . 4
5. BGP-SPF Applicability to Clos Networks . . . . . . . . . . . 4
5.1. Usage of BGP-LS SPF BGP-LS-SPF SAFI . . . . . . . . . . . . . . . . 5
5.1.1. Relationship to Other BGP AFI/SAFI Tuples . . . . . . 5
5.2. Peering Models . . . . . . . . . . . . . . . . . . . . . 5
5.2.1. Sparse Peering Model . . . . . . . . . . . . . . . . 6
5.2.2. Bi-Connected Biconnected Graph Heuristic . . . . . . . . . . . . 7
5.3. BGP Spine/Leaf Topology Policy . . . . . . . . . . . . . 7
5.4. BGP Peer Discovery Considerations . . . . . . . . . . . . 8
5.5. BGP Peer Discovery . . . . . . . . . . . . . . . . . . . 9
5.5.1. BGP IPv6 Simplified Peering . . . . . . . . . . . . . 9
5.5.2. BGP-LS SPF Topology Visibility for Management . . . . 9
5.5.3. Data Center Interconnect (DCI) Applicability . . . . 10
6. Non-CLOS/FAT Non-Clos / Fat Tree Topology Applicability . . . . . . . . . . 10
7. Non-Transit Node Capability . . . . . . . . . . . . . . . . . 10
8. BGP Policy Applicability . . . . . . . . . . . . . . . . . . 10
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10
10. Security Considerations . . . . . . . . . . . . . . . . . . . 11
11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 11
12. References . . . . . . . . . . . . . . . . . . . . . . . . . 11
12.1.
11.1. Normative References . . . . . . . . . . . . . . . . . . 11
12.2.
11.2. Informative References . . . . . . . . . . . . . . . . . 11
Acknowledgements
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 13
1. Introduction
This document complements [I-D.ietf-lsvr-bgp-spf] [RFC9815] by discussing the applicability
of the BGP-SPF technology in a simple and fairly common deployment
scenario, which is described in Section 3.
Section 4 describes the reasons for BGP modifications for such
deployments.
Section 5 covers the BGP Link-State Shortest Path First (IGP-SPF) BGP-SPF protocol enhancements to BGP to meet
these requirements and their applicability to data center [Clos]
networks.
2. Recommended Reading
This document assumes knowledge of existing data center networks and
data center network topologies [Clos]. This document also assumes
knowledge of data center routing protocols such as BGP [RFC4271],
BGP-SPF [I-D.ietf-lsvr-bgp-spf], [RFC9815], and OSPF [RFC2328] [RFC5340], [RFC5340] as well as data
center Operations, Administration, and Maintenance (OAM) protocols
like the Link Layer Discovery Protocol (LLDP) [RFC4957] and Bi-
Directional
Bidirectional Forwarding Detection (BFD) [RFC5580]. [RFC5880].
3. Common Deployment Scenario
Within a data center, servers are commonly interconnected using the
Clos topology [Clos]. The Clos topology is fully non-blocking non-blocking, and
the topology is realized using Equal Cost Multi-Path Equal-Cost Multipath (ECMP). In a
multi-stage Clos topology, the minimum number of parallel paths in
each tier is determined by the width of the stage as shown in the
figure
Figure 1.
Tier 1
+-----+
|NODE |
+->| 1 |--+
| +-----+ |
Tier 2 | | Tier 2
+-----+ | +-----+ | +-----+
+------------->|NODE |--+->|NODE |--+--|NODE |--------------+
| +-----| 5 |--+ | 2 | +--| 7 |-----+ |
| | +-----+ +-----+ +-----+ | |
| | | |
| | +-----+ +-----+ +-----+ | |
| +------+---->|NODE |--+ |NODE | +--|NODE |-----+------+ |
| | | +---| 6 |--+->| 3 |--+--| 8 |---+ | | |
| | | | +-----+ | +-----+ | +-----+ | | | |
| |Tier 3| | | | | |Tier 3| |
+-----+ +-----+ | +-----+ | +-----+ +-----+
|NODE | |NODE | +->|NODE |--+ |NODE | |NODE |
| 9 | | 10 | | 4 | | 11 | | 12 |
+-----+ +-----+ +-----+ +-----+ +-----+
| | | | | | | | | | | |
<- Servers -> <- Servers ->
Figure 1: Illustration of the Basic Clos
* Tier 1 is comprised of Nodes 1, 2, 3, and 4
* Tier 2 is comprised of Nodes 5, 6, 7, and 8
* Tier 3 is comprised of Nodes 9, 10, 11, and 12
Figure 1: Illustration of the basic Clos
4. Justification for the BGP-SPF Extension
To simplify L3 Layer 3 (L3) routing and operations, many data centers
use BGP as a routing protocol to create both an underlay and an
overlay network for their Clos Topologies topologies [RFC7938]. However, BGP is
a path-vector routing protocol. Since it does not create a fabric
topology, it uses hop-by-hop External BGP (EBGP) peering to
facilitate hop-by-hop routing to create the underlay network and to
resolve any overlay next hops. The hop-by-hop BGP peering paradigm
imposes several restrictions within a Clos. It prohibits the
deployment of Route
Reflectors/Route Controllers route reflectors / route controllers as the EBGP
sessions are congruent with the data path. The BGP best-path
algorithm is prefix-based prefix based, and it prevents announcements of prefixes
to other BGP speakers until the best-path decision process has been
performed for the prefix at each intermediate hop. These
restrictions significantly delay the overall convergence of the
underlay network within a Clos network.
The BGP-SPF modifications allow BGP to overcome these limitations.
Furthermore, using the BGP-LS Network Layer Reachability Information
(NLRI) format allows the BGP-SPF data to be advertised for nodes,
links, and prefixes in the BGP routing domain and used for Short-
Path-First (SPF) SPF
computations [RFC9552].
Additional motivation for deploying BGP-SPF is included in
[I-D.ietf-lsvr-bgp-spf]. [RFC9815].
5. BGP-SPF Applicability to Clos Networks
With the BGP-SPF extensions [I-D.ietf-lsvr-bgp-spf], [RFC9815], the BGP best-
path best-path computation
and route computation are replaced with link-state algorithms such as
those used by OSPF [RFC2328], both to determine whether an a BGP-LS-SPF
NLRI has changed and needs to be re-advertised readvertised and to compute the BGP
routes. These modifications will significantly improve convergence
of the underlay while affording the operational benefits of a single
routing protocol [RFC7938].
Data center controllers typically require visibility to the BGP
topology to compute traffic-engineered paths. These controllers
learn the topology and other relevant information via the BGP-LS
address family [RFC9552] [RFC9552], which is totally independent of the
underlay address families (usually IPv4/IPv6 unicast). Furthermore,
in traditional BGP underlays, all the BGP routers will need to
advertise their BGP-LS information independently. With the BGP-SPF
extensions, controllers can learn the topology using the same BGP
advertisements used to compute the underlay routes. Furthermore,
these data center controllers can avail the convergence advantages of
the BGP-SPF extensions. The placement of controllers can be outside
of the forwarding path or within the forwarding path.
Alternatively, as each and every router in the BGP-SPF domain will
have a complete view of the topology, the operator can also choose to
configure BGP sessions in the hop-by-hop peering model described in
[RFC7938] along with BFD [RFC5580]. In doing so, while the hop-by-
hop peering model lacks the inherent benefits of the controller-based
model, BGP updates need not be serialized by the BGP best-path
algorithm in either of these models. This helps overall network
convergence.
5.1. Usage of BGP-LS SPF BGP-LS-SPF SAFI
Section 5.1 of [I-D.ietf-lsvr-bgp-spf] [RFC9815] defines a new BGP-LS-SPF SAFI for
announcement of the BGP-SPF link-state. The NLRI format and its
associated attributes follow the format of BGP-LS for node, link, and
prefix announcements. Whether the peering model within a Clos
follows hop-by-hop peering described in [RFC7938] or any controller-
based or route-reflector peering, an operator can exchange BGP-LS-SPF
SAFI routes over the BGP peering by simply configuring BGP-LS-SPF
SAFI between the necessary BGP speakers.
The BGP-LS-SPF SAFI can also co-exist coexist with BGP IP Unicast SAFI
[RFC4760]
[RFC4760], which could exchange overlapping IP routes. One use case
for this is where BGP-LS-SPF routes are used for the underlay and BGP
IP Unicast routes for VPNs are advertised in the overlay as described
in [RFC4364]. The routes received by these SAFIs are evaluated,
stored, and announced independently according to the rules of
[RFC4760]. The tie-breaking tiebreaking of route installation is a matter of the
local policies and preferences of the network operator.
Finally, as the BGP-SPF peering is done following the procedures
described in [RFC4271], all the existing transport security
mechanisms including those in [RFC5925] are available for the BGP-LS-SPF BGP-LS-
SPF SAFI.
5.1.1. Relationship to Other BGP AFI/SAFI Tuples
Normally, the BGP-LS-SPF AFI/SAFI is used solely to compute the
underlay and is given precedence over other AFI/SAFIs in route
processing. Other BGP SAFIs, e.g., IPv6/IPv6 Unicast VPN unicast VPN, would use
the BGP-SPF computed routes for next hop next-hop resolution.
5.2. Peering Models
As previously stated, BGP-SPF can be deployed using the existing
peering model where there is a single-hop BGP session on each and
every link in the data center fabric [RFC7938]. This provides for
both the advertisement of routes and the determination of link and
neighboring router availability. With BGP-SPF, the underlay will
converge faster due to changes to the decision process that will
allow NLRI changes to be advertised faster after detecting a change.
5.2.1. Sparse Peering Model
Alternately, BFD [RFC5580] can be used to swiftly determine the
availability of links links, and the BGP peering model can be significantly
sparser than the data center fabric. BGP-SPF sessions only need to
be established with enough peers to provide a bi-connected biconnected graph. If
Internal BGP (IBGP) is used, then the BGP routers at tier N-1 will
act as route-reflectors for the routers at tier N.
The obvious usage of sparse peering is to avoid parallel BGP sessions
on links between the same two routers in the data center fabric.
However, this use case is not very useful since parallel L3 links
between the same two BGP routers are rare in Clos or Fat-Tree Fat Tree
topologies. Additionally, when there are multiple links, they are
often aggregated at the link layer using Link Aggregation Groups (LAGs) at the link
layer [IEEE.802.1AX] rather than at the IP layer. Two more
interesting scenarios are described below.
In current data center topologies, there is often a very dense mesh
of links between levels, e.g., leaf and spine, providing 32-way,
64-way, 32-way
paths, 64-way paths, or more Equal-Cost Multi-Path (ECMP) paths. ECMPs. In these topologies, it is
desirable not to have a BGP session on every link link, and techniques
such as the one described in Section 5.2.2 can be used to establish
sessions on some subset of northbound links. For example, in a Spine-Leaf
Spine/Leaf topology, each leaf router would only peer with a subset
of the spines dependent on the flooding redundancy required to be
reasonably certain that every node within the BGP-SPF routing domain
has the complete topology.
Alternately, controller-based data center topologies are envisioned
where BGP speakers within the data center only establish BGP sessions
with two or more controllers. In these topologies, fabric nodes
below the first tier, as shown in Figure 1 of [RFC7938], will
establish BGP multi-hop sessions with the controllers. For the
multi-hop sessions, determining the route to the controllers without
depending on BGP would need to be through some other means beyond the
scope of this document. However, the BGP discovery mechanisms
described in Section 5.5 would be one possibility.
5.2.2. Bi-Connected Biconnected Graph Heuristic
With this a biconnected graph heuristic, discovery of BGP SPF peers is
assumed, e.g., as described in Section 5.5. In this context, "bi-connected"
"biconnected" refers to the fact that there must be an adverised link advertised
Link NLRI for both BGP and SPF peers associated with the link before
the link can be used in the BGP SPF route calcuation. calculation. Additionally,
it is assumed that the direction of the peering can be ascertained.
In the context of a data center fabric, the direction is either
northbound (toward the spine), southbound (toward the Top-Of-Rack Top-of-Rack
(ToR) routers) routers), or east-west (same level in the hierarchy). The
determination of the direction is beyond the scope of this document.
However, it would be reasonable to assume a technique where the ToR
routers can be identified and the number of hops to the ToR is used
to determine the direction.
In this heuristic, BGP speakers allow passive session establishment
for southbound BGP sessions. For northbound sessions, BGP speakers
will attempt to maintain two northbound BGP sessions with different
routers. For east-west sessions, passive BGP session establishment
is allowed. However, a BGP speaker will never actively establish an
east-west BGP session unless it cannot establish two northbound BGP
sessions.
BGP SPF sparse peering deployments not using this hueristic heuristic are
possible but are not described herein and are considered out of
scope.
5.3. BGP Spine/Leaf Topology Policy
One of the advantages of using BGP-SPF as the underlay protocol is
that BGP policy can be applied at any level. For example, depending
on the topology, it may be possible to aggregate or filter prefix
advertisements using the existing BGP policy. In Spine/Leaf
topologies, it is not necessary to advertise a BGP-LS Prefix NLRI
received by leaf nodes from the spine back to other spine nodes. If
a common AS Autonomous System (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 the spine if the first AS in the AS
path is the spine AS.
In the figure below, the leaves would not advertise any NLRI NLRIs with AS
64512 as the first AS in the AS path.
+--------+ +--------+ +--------+
AS 64512 | | | | | |
for Spine | Spine 1+----+ Spine 2+- ......... -+ Spine N|
Nodes at | | | | | |
this Level +-+-+-+-++ ++-+-+-+-+ +-+-+-+-++
+------+ | | | | | | | | | | |
| +-----|-|-|------+ | | | | | | |
| | +--|-|-|--------+-|-|-----------------+ | | |
| | | | | | +---+ | | | | |
| | | | | | | +--|-|-------------------+ | |
| | | | | | | | | | +------+ +----+
| | | | | | | | | +--------------|----------+ |
| | | | | | | | +-------------+ | | |
| | | | | +----|--|----------------|--|--------+ | |
| | | | +------|--|--------------+ | | | | |
| | | +------+ | | | | | | | |
++--+--++ +-+-+--++ ++-+--+-+ ++-+--+-+
| Leaf 1| | Leaf 2| ........ | Leaf X| | Leaf Y|
+-------+ +-------+ +-------+ +-------+
Figure 2: Spine/Leaf Topology Policy
5.4. BGP Peer Discovery Considerations
The basic functionality of peer discovery is to be discover the address
of a single-hop peer in the case where the peer address is not
pre-configured.
preconfigured. This is being accomplished today by using IPv6 Router
Advertisements (RA) (RAs) [RFC4861] and assuming that a BGP session is
desired with any discovered peer. Beyond the basic functionality, it
may be useful to have the following information relating to the BGP
session:
* Autonomous System (AS) The AS and BGP Identifier of a potential peer.
* Security capabilities supported Supported security capabilities, and for cryptographic
authentication, the security capabilities and possibly a key-chain key chain
[RFC8177] to be used. for use.
* A Session Policy Identifier - A Identifier, which is a group number or name used
to associate common session parameters with the peer. For
example, in a data center, BGP sessions with a ToR device could
have different parameters than BGP sessions between leaf and
spine.
In a data center fabric, it is often useful to know whether a peer is
southbound (towards the servers) or northbound (towards the spine or
super-spine), e.g., see Section 5.2.2. One mechanism, without
specifying all the details, might be for the ToR routers to be
identified when installed and for the others other routers in the fabric to
determine their level based on the distance from the closest ToR
router.
If there are multiple links between BGP speakers or the links between
BGP speakers are unnumbered, it is also useful to be able to
establish multi-hop sessions using the loopback addresses. This will
often require the discovery protocol to install route(s) one or more routes
toward the potential peer loopback addresses prior to BGP session
establishment.
Finally, a simple BGP discovery protocol may be used to establish a
multi-hop session with one or more controllers by advertising
connectivity to one or more controllers.
5.5. BGP Peer Discovery
5.5.1. BGP IPv6 Simplified Peering
To conserve IPv4 address space and simplify operations, BGP-SPF
routers in Clos/Fat Clos / Fat Tree deployments can use IPv6 addresses as the
peer address. For IPv4 address families, IPv6 peering as specified
in [RFC8950] can be deployed to avoid configuring IPv4 addresses on
router interfaces. When this is done, dynamic discovery mechanisms,
as described in Section 5.5, can be used to learn the global or link-
local IPv6 peer addresses 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 [RFC7404]
.
[RFC7404]. The Link Local/Remote Identifiers of the peering
interfaces MUST be used in the link Link NLRI as described in section
Section 5.2.2 of
[I-D.ietf-lsvr-bgp-spf]. [RFC9815].
5.5.2. BGP-LS SPF Topology Visibility for Management
Irrespective of whether or not BGP-SPF is used for route calculation,
the BGP-LS-SPF route advertisements can be used to periodically
construct the Clos/Fat Clos / Fat Tree topology. This is especially useful in
deployments where an Interior Gateway Protocol (IGP) is not used and
the base BGP-LS routes [RFC9552] 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 or other management tool which that could also be used for
fabric data path verification. The precise algorithms and
heuristics, as well as the complete set of management applications applications,
is beyond the scope of this document.
5.5.3. Data Center Interconnect (DCI) Applicability
Since BGP-SPF is to be used for the routing underlay and DCI Data Center
Interconnect (DCI) gateway boxes typically have direct or very simple
connectivity, BGP external sessions would typically not include the
BGP-LS-SPF SAFI.
6. Non-CLOS/FAT Non-Clos / Fat Tree Topology Applicability
The BGP-SPF extensions [I-D.ietf-lsvr-bgp-spf] [RFC9815] can be used in other topologies and
avail the inherent convergence improvements. Additionally, sparse
peering techniques may be utilized Section 5.2. However, determining
whether to establish a BGP session is more
complex complex, and the heuristic
described in Section 5.2.2 cannot be used. In such topologies, other
techniques such as those described in [RFC9667] may be employed. One
potential deployment would be the underlay for a Service Provider
(SP) backbone where usage of a single protocol, i.e., BGP, is
desired.
7. Non-Transit Node Capability
In certain scenarios, a BGP node wishes to participate in the BGP-SPF
topology but never be used for transit traffic. These include
situations where a server wants to make application services
available to clients homed at subnets throughout the BGP-SPF domain
but does not ever want to be used as a router (i.e., carry transit
traffic). Another specific instance is where a controller is
resident on a server and direct connectivity to the controller is
required throughout the entire domain. This can readily be
accomplished using the BGP-LS BGP-LS-SPF Node NLRI Attribute SPF Status TLV
as described in [I-D.ietf-lsvr-bgp-spf]. [RFC9815].
8. BGP Policy Applicability
Existing BGP policy such as prefix filtering may be used in
conjunction with the BGP-LS-SPF SAFI. When BGP policy is used with
the BGP-LS-SPF SAFI, BGP speakers in the BGP-LS-SPF routing domain
will not all have the same set of NLRI NLRIs and will compute a different
BGP local routing table. Consequently, care must be taken to assure
routing is consistent and blackholes or routing loops do not ensue.
However, this is no different than if traditional BGP routing using
the IPv4 and IPv6 address families were used.
9. IANA Considerations
No
This document has no IANA updates are requested by this document. actions.
10. Security Considerations
This document introduces no new security considerations above and
beyond those already specified in the [RFC4271] and
[I-D.ietf-lsvr-bgp-spf]. [RFC9815].
11. Acknowledgements
The authors would like to thank Alvaro Retana, Yan Filyurin, Boris
Hassanov, Stig Venaas, Ron Bonica, Mallory Knodel, Dhruv Dhody, Erik
Kline, Eric Vyncke, and John Scudder for their review and comments.
12. References
12.1.
11.1. Normative References
[I-D.ietf-lsvr-bgp-spf]
[RFC9815] 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-51, 14
January RFC 9815,
DOI 10.17487/RFC9815, July 2025,
<https://datatracker.ietf.org/api/v1/doc/document/draft-
ietf-lsvr-bgp-spf/>.
12.2.
<https://www.rfc-editor.org/info/rfc9815>.
11.2. Informative References
[Clos] Clos, C., "A Study of Non-Blocking Switching Networks",
The Bell System Technical Journal, Vol. 32(2), vol. 32, no. 2, pp.
406-424, DOI 10.1002/j.1538-7305.1953.tb01433.x, March 1953.
1953,
<https://doi.org/10.1002/j.1538-7305.1953.tb01433.x>.
[IEEE.802.1AX]
IEEE, "IEEE Standard for Local and Metropolitan Area
Networks: Link
Networks--Link Aggregation", IEEE Std 802.1AX-2020,
DOI 10.1109/IEEESTD.2020.9105034, May 2020,
<https://standards.ieee.org/standard/802_1AX-2020.html>.
<https://doi.org/10.1109/IEEESTD.2020.9105034>.
[RFC2328] Moy, J., "OSPF Version 2", STD 54, RFC 2328,
DOI 10.17487/RFC2328, April 1998,
<https://www.rfc-editor.org/info/rfc2328>.
[RFC4271] Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A
Border Gateway Protocol 4 (BGP-4)", RFC 4271,
DOI 10.17487/RFC4271, January 2006,
<https://www.rfc-editor.org/info/rfc4271>.
[RFC4364] Rosen, E. and Y. Rekhter, "BGP/MPLS IP Virtual Private
Networks (VPNs)", RFC 4364, DOI 10.17487/RFC4364, February
2006, <https://www.rfc-editor.org/info/rfc4364>.
[RFC4760] Bates, T., Chandra, R., Katz, D., and Y. Rekhter,
"Multiprotocol Extensions for BGP-4", RFC 4760,
DOI 10.17487/RFC4760, January 2007,
<https://www.rfc-editor.org/info/rfc4760>.
[RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman,
"Neighbor Discovery for IP version 6 (IPv6)", RFC 4861,
DOI 10.17487/RFC4861, September 2007,
<https://www.rfc-editor.org/info/rfc4861>.
[RFC4957] Krishnan, S., Ed., Montavont, N., Njedjou, E., Veerepalli,
S., and A. Yegin, Ed., "Link-Layer Event Notifications for
Detecting Network Attachments", RFC 4957,
DOI 10.17487/RFC4957, August 2007,
<https://www.rfc-editor.org/info/rfc4957>.
[RFC5340] Coltun, R., Ferguson, D., Moy, J., and A. Lindem, "OSPF
for IPv6", RFC 5340, DOI 10.17487/RFC5340, July 2008,
<https://www.rfc-editor.org/info/rfc5340>.
[RFC5580] Tschofenig, H., Ed., Adrangi, F., Jones, M., Lior, A., and
B. Aboba, "Carrying Location Objects in RADIUS and
Diameter", RFC 5580, DOI 10.17487/RFC5580, August 2009,
<https://www.rfc-editor.org/info/rfc5580>.
[RFC5880] Katz, D. and D. Ward, "Bidirectional Forwarding Detection
(BFD)", RFC 5880, DOI 10.17487/RFC5880, June 2010,
<https://www.rfc-editor.org/info/rfc5880>.
[RFC5925] Touch, J., Mankin, A., and R. Bonica, "The TCP
Authentication Option", RFC 5925, DOI 10.17487/RFC5925,
June 2010, <https://www.rfc-editor.org/info/rfc5925>.
[RFC7404] Behringer, M. and E. Vyncke, "Using Only Link-Local
Addressing inside an IPv6 Network", RFC 7404,
DOI 10.17487/RFC7404, November 2014,
<https://www.rfc-editor.org/info/rfc7404>.
[RFC7938] Lapukhov, P., Premji, A., and J. Mitchell, Ed., "Use of
BGP for Routing in Large-Scale Data Centers", RFC 7938,
DOI 10.17487/RFC7938, August 2016,
<https://www.rfc-editor.org/info/rfc7938>.
[RFC8177] Lindem, A., Ed., Qu, Y., Yeung, D., Chen, I., and J.
Zhang, "YANG Data Model for Key Chains", RFC 8177,
DOI 10.17487/RFC8177, June 2017,
<https://www.rfc-editor.org/info/rfc8177>.
[RFC8950] Litkowski, S., Agrawal, S., Ananthamurthy, K., and K.
Patel, "Advertising IPv4 Network Layer Reachability
Information (NLRI) with an IPv6 Next Hop", RFC 8950,
DOI 10.17487/RFC8950, November 2020,
<https://www.rfc-editor.org/info/rfc8950>.
[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/info/rfc9552>.
[RFC9667] Li, T., Ed., Psenak, P., Ed., Chen, H., Jalil, L., and S.
Dontula, "Dynamic Flooding on Dense Graphs", RFC 9667,
DOI 10.17487/RFC9667, October 2024,
<https://www.rfc-editor.org/info/rfc9667>.
Acknowledgements
The authors would like to thank Alvaro Retana, Yan Filyurin, Boris
Hassanov, Stig Venaas, Ron Bonica, Mallory Knodel, Dhruv Dhody, Erik
Kline, Éric Vyncke, and John Scudder for their reviews and comments.
Authors' Addresses
Keyur Patel
Arrcus, Inc.
2077 Gateway Pl
San Jose, CA, CA 95110
United States of America
Email: keyur@arrcus.com
Acee Lindem
LabN Consulting, L.L.C.
301 Midenhall Way
Cary, NC, NC 95110
United States of America
Email: acee.ietf@gmail.com
Shawn Zandi
Linkedin
LinkedIn
222 2nd Street
San Francisco, CA 94105
United States of America
Email: szandi@linkedin.com
Gaurav Dawra
Linkedin
222 2nd Street
San Francisco, CA 94105
United States of America
Email: gdawra@linkedin.com
Jie Dong
Huawei Technologies
No. 156 Beiqing Road
Beijing
China
Email: jie.dong@huawei.com