Internet-Draft | BGP CAR Problem Statement | November 2021 |
Rao, et al. | Expires 26 May 2022 | [Page] |
- Workgroup:
- BESS WorkGroup
- Internet-Draft:
- draft-dskc-bess-bgp-car-problem-statement-04
- Published:
- Intended Status:
- Informational
- Expires:
BGP Color-Aware Routing Problem Statement
Abstract
This document explores the scope, use-cases and requirements for a BGP based routing solution to establish end-to-end intent-aware paths across a multi-domain service provider network environment.¶
Status of This Memo
This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79.¶
Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet-Drafts is at https://datatracker.ietf.org/drafts/current/.¶
Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress."¶
This Internet-Draft will expire on 26 May 2022.¶
Copyright Notice
Copyright (c) 2021 IETF Trust and the persons identified as the document authors. All rights reserved.¶
This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Revised BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Revised BSD License.¶
1. Introduction
1.1. Objective
This document explores the scope, use-cases and requirements for a BGP based routing solution to establish end-to-end intent-aware paths across a multi-domain service provider network environment.¶
The targeted design outcome is to define the technology and protocol extensions that may be required in a manner that addresses the widest application.¶
The problem that the document initially focuses on is the BGP-based delivery of an intent across several transport domains. To do this, it describes existing intent-aware routing solutions that are deployed and then extends the solution scope and architecture to BGP.¶
The problem space is then widened to include any intent (including NFV chains and their location), any dataplane and the application of the intent-based routing to the Service/VPN routes. All of this is detailed in the rest of the document.¶
1.2. Color-Aware Routing
Color-Aware Routing (CAR) establishes routed paths that satisfy specific intent in a network. This section describes the basic concepts that define CAR and the protocols that currently support it.¶
The figure below is used as reference.¶
1.2.1. Intent
Intent in routing may be any combination of the following behaviors:¶
- Topology path selection (e.g. minimize metric, avoid resource)¶
- NFV service insertion (e.g. service chain steering)¶
- Per-hop behavior (e.g. QoS for 5G slice)¶
An intent-aware routed path may be within a single network domain or across multiple domains.¶
1.2.2. Color
Color is a 32-bit numerical value that is associated with an intent, as defined in [I-D.ietf-spring-segment-routing-policy]¶
1.2.3. Colored Service Route
An Egress PE E2 colors a BGP service (e.g., VPN) route V/v to indicate the particular intent that E2 requests for the traffic bound to V/v. The color (C) is encoded as a BGP Color Extended community [I-D.ietf-idr-tunnel-encaps].¶
1.2.4. Color-Aware Route
(E2, C) is a color-aware route to E2 which satisfies the intent associated with color C.¶
Multiple technologies already provide color-aware paths in solutions that are widely deployed.¶
In the context of large-scale SR-MPLS networks, SR Policy is applicable to both intra-domain and inter-domain deployments; whereas IGP Flex-Algo is better suited to intra-domain scenarios.¶
1.2.5. Service Route Automated Steering on color-aware route
An ingress PE E1 automatically steers V-destined packets onto a Color-Aware path bound to (E2, C). If several such paths exist, a preference scheme is used to select the best path: E.g. IGP Flex-Algo first, then SR Policy.¶
1.2.6. Inter-Domain color-aware routing with SR Policy
If E1 and E2 are in different domains, E1 may request an SR-PCE in its domain for a path to (E2, C). The SR-PCE (or a set of them) computes the end-to-end path and installs it at E1 as an SR Policy. The end-to-end color-aware path may seamlessly cross multiple domains.¶
1.2.7. Need for a BGP-based color-aware routing solution
- An operator with an existing Seamless-MPLS/BGP-LU inter-domain deployment [I-D.ietf-mpls-seamless-mpls] may prefer a BGP based extension as a more incremental approach¶
- There may be an expectation that BGP would support a larger scale¶
- Trust boundaries in an inter-domain deployment leads to a preference for a BGP peering based solution¶
1.2.8. BGP Color-Aware Routing
BGP Color-Aware Routing (CAR) is a new BGP solution which signals intent-aware routes to reach a given destination (e.g., E2). (E2, C) represents a BGP hop-by-hop distributed route that builds an inter-domain color-aware path to E2 for color C.¶
1.2.9. Architectural consistency among color-aware routing solutions
As seen above, multiple technologies exist that provide color-aware routing in a network. A BGP based solution must be compliant with the existing principles that apply to them:¶
-
Service routes MUST be colored using BGP Color Extended-Community to request intent¶
- V/v via E, colored with C¶
-
Colored service routes MUST be automatically steered on an appropriate color-aware path¶
-
Color-aware routes MAY resolve recursively via other color-aware routes¶
- (E, C) via N recursively resolves via (N, C)¶
Here is a brief example that illustrates these principles.¶
In the figure above, all the nodes are part of an inter-domain network under a single authority and with a consistent color-to-intent mapping:¶
-
Color C1 is mapped to "low delay"¶
- Flex-Algo FA1 is mapped to "low delay" and hence to C1¶
-
Color C2 is mapped to "low delay and avoid resource R"¶
- Flex-Algo FA2 is mapped to "low delay and avoid resource R" and hence to C2¶
E1 receives two BGP colored service routes from E2:¶
E1 has the following inter-domain color-aware paths:¶
-
(E2, C1) provided by BGP CAR which recursively resolves via intra-domain color-aware paths:¶
- (E2, C2) provided by SR Policy¶
E1 automatically steers the received colored service routes as follows:¶
The example illustrates the benefits provided by leveraging the architectural principles:¶
-
Seamless co-existence of multiple color-aware technologies, e.g., BGP CAR and SR Policy¶
-
Seamless and complementary interworking between different color-aware technologies¶
- V/v is steered on a BGP CAR color-aware path that is itself resolved within domain 2 onto an SR Policy bound to the color of V/v¶
1.2.10. Color Domains
1.2.11. Per-Destination and Per-Flow Steering with BGP CAR
Ingress PE E1 steers packets destined for a service (VPN) route V/v via BGP Color-Aware Route R/r to E2¶
- Per-Destination Steering: Incoming packets on E1 match BGP service route V/v to be steered based on the destination IP address of the packets.¶
- Per-Flow Steering: Incoming packets on E1 match BGP service route V/v to be steered based on the combination of the destination IP address and additional elements in the packet header (i.e., IP flow). Such a packet lookup may recurse on a forwarding array where some of the entries are BGP color-aware routes to E2. A given flow is mapped to a specific entry in this array i.e. via a specific BGP color-aware route to E2.¶
2. Intent bound to a Color
The BGP CAR solution must support the following intents bound to a color:¶
-
Minimization of a cost metric vs a latency metric¶
- Minimization of different metric types, static and dynamic¶
- Exclusion/Inclusion of SRLG and/or Link Affinity and/or minimum MTU/number of hops¶
- Bandwidth management¶
- In the inter-domain context, exclusion/inclusion of entire domains, and border routers¶
-
Inclusion of one or several virtual network function chains¶
- Located in a regional domain and/or core domain, in a DC¶
-
Localization of the virtual network function chains¶
- Some functions may be desired in the regional DC or vice versa¶
- Per-Destination and Per-Flow steering¶
3. BGP CAR Use-cases
The BGP CAR route may be a transport route or a service route (in this document, we use the term VPN instead of service for simplicity).¶
3.1. BGP Transport CAR
-
Transport Intent¶
-
The network diagram below illustrates the reference network topology used in this section for Transport CAR:¶
The following network design assumptions apply to the reference topology above, as an example:¶
- Independent ISIS/OSPF SR instance in each domain.¶
- eBGP peering link between ASBRs (121-211, 121-212, 122-211, 122-212, 231-321, 231-322, 232-321 and 232-322).¶
- Peering links have equal cost metric.¶
- Peering links have delay configured or measured as shown by "D". D=50 for cross peering links.¶
- VPN service is running from PE31 to PE11 via service RRs (S-RRn in figure).¶
- The following sections illustrate a few examples of intent use-cases applicable to transport routes.¶
3.1.1. Use-case of minimization of a cost metric vs a latency metric
-
Cost Optimized¶
- Color C1 - Minimum cost intent. (Here, a BGP CAR route with Color C1 is being used, instead of BGP-LU.)¶
-
On PE11, VPN routes colored with C1 are steered via (C1, PE31) BGP CAR route¶
-
Minimize latency¶
- Color C2 - Minimum latency intent.¶
-
On PE11, VPN routes colored with C2 are steered via (C2, PE31) BGP CAR route.¶
- BGP CAR for C2 advertises paths between PEs for minimum end-to-end delay.¶
- (2) These paths traverse over intra-domain Flex Algo 128 in each domain and account for peering link delay between ASBRs.¶
- (3) Example: PE11 learns (C2, PE31) BGP CAR route and best path is through FA128 to node 122, link 122-212, FA128 to 232, link 232-322, FA128 to PE31.¶
3.1.2. Use-case of exclusion/inclusion of link affinity
- Color C3 - Intent to Minimize cost metric and avoid purple links¶
-
On PE11, VPN routes colored with C3 are steered via (C3, PE31) BGP CAR route.¶
- BGP CAR for C3 sets up paths between PEs for minimum end-to-end cost and avoiding purple link affinity.¶
- These paths traverse over intra domain Flex Algo 129 in each domain and accounts for peering link cost between ASBR and avoiding purple links.¶
-
Example: PE11 learns (C3, PE31) BGP CAR route via 2 paths.¶
3.1.3. Use-case of exclusion/inclusion of domains
Color C4 - Avoid sending selected traffic via Domain 3¶
3.1.4. Use-case of virtual network function chains in local and core domains
3.2. BGP VPN CAR
-
VPN (Service layer) intent¶
-
Extend the signaling of intent awareness end-to-end: CE site to CE site across provider networks¶
-
Provide ability for a CE to select paths through specific PEs for a given intent¶
- Example-1: Certain intent in transport not available via specific PEs¶
- Example-2: Certain CE-PE connection does not support specific intent¶
- Example-3: Site access via certain CE does not support specific intent. For instance, link connecting a specific CE to a DC hosting loss-sensitive service may have better quality than a link from another CE¶
- Provide ability for a CE to send traffic indicating a specific intent (via suitable encapsulation) to the PE for optimal steering.¶
-
-
Intent aware routing support for multiple service (VPN) interworking models¶
-
-
The network diagram below illustrates the reference network topology used in this section for VPN CAR.¶
The following network design assumptions apply to the reference topology above, as an example:¶
- Independent ISIS/OSPF SR instance in each AS.¶
- eBGP peering link between VPN ASBRs 121-211, 121-212, 122-211, 122-212.¶
- VPN service is running between PEs via service RRs in each AS to local ASBRs. Between ASBRs, its Option-B i.e. next hop self for VPN SAFI.¶
- CE1 is dual homed to PE11 and PE12. Similarly, CE2 is dual homed to PE21 and PE22.¶
- Peering links have equal cost metric¶
- Peering links have delay configured or measured as shown by "D".¶
- CE2 advertises prefix V/24 to CE1. It is advertised as RD:V/24 between PEs, including color-awareness¶
- The following sections illustrate a few examples of intent use-cases applicable to VPN (service) routes.¶
3.2.1. Use-case of minimization of a cost metric vs a latency metric
-
Cost Optimized¶
- Color C1 - Minimum cost intent.¶
-
On CE1, flows requiring cost optimized paths to V/24 are steered over (C1, V/24) route.¶
- BGP CAR for C1 sets up paths between CEs for minimum end-to-end cost.¶
- This advertisement needs BGP CAR between PE-CE for V/24 prefix and color C1 awareness.¶
- It also needs BGP VPN CAR between PEs and ASBRs for RD:V/24 prefix and color C1 awareness (C1, RD:V/24).¶
- Paths traverse over PE-CE links, intra-domain Flex Algo 0 in each AS and peering links between ASBRs, minimizing cost for VPN.¶
-
Example: CE1 learns (C1, V/24) CAR route through several equal cost paths:¶
-
Minimize latency¶
- Color C2 - Minimum latency intent¶
-
On CE1, flows requiring low latency paths to prefix V/24 are steered over (C2, V/24) CAR route.¶
- BGP CAR for C2 sets up paths between CEs for minimum end-to-end delay.¶
- This advertisement needs BGP CAR between PE-CE for V/24 prefix and color C2 awareness.¶
- It also needs BGP VPN CAR between PEs and ASBR for RD:V/24 prefix and color C2 awareness (C2, RD:V/24).¶
- Paths traverse over intra-domain Flex Algo 128 in each AS and accounts for inter ASBR link delays and PE-CE link delays for the VPN.¶
- Example: CE1 learns (C2, V/24) CAR best route through link CE1-PE12, FA128 to 122, link 122-212, FA128 to PE22 and link PE22-CE2.¶
3.2.2. Use-case of exclusion/inclusion of link affinity
- Color C3 - Intent to Minimize cost metric and avoid purple links¶
-
On CE1, flows requiring minimum cost path avoiding purple links to V/24 are steered over (C3, V/24) BGP CAR route.¶
- BGP CAR for C3 setup paths between CEs for minimum end-to-end cost and avoiding purple link affinity.¶
- This advertisement needs BGP CAR between PE-CE for V/24 prefix and color C3 awareness¶
- It also needs BGP VPN CAR between PEs and ASBRs for RD:V/24 prefix and color C3 awareness (C3, RD:V/24).¶
- The path avoids purple PE-CE links, traverses over intra-domain Flex Algo 129 in each AS and avoids purple links between VPN ASBRs.¶
- Example: CE1 learns (C3, V/24) CAR route through link CE1-PE11, FA129 to 121, link 121-211, FA129 to PE21 and link PE21-CE2.¶
3.2.3. Use-case of virtual network function chains in local and core domains
4. Deployment Requirements
The figure below shows a reference large-scale multi-domain network topology for targeted deployments. E1 and E2 are PEs; the other nodes are border routers between domains in different tiers of the network. A VPN route is advertised via service RRs (S-RR) between an egress PE (E2) and an ingress PE (E1). BGP must provide reachability from E1 to E2 based on various intent.¶
The solution must support the following :¶
- Co-existence, compatibility and interworking with currently deployed SR-PCE based multi-domain color-aware solution¶
-
Support different multi-domain deployment designs¶
-
Support end-to-end path crossing transport domains with different technologies and encapsulations¶
- Support interworking between domains with different encapsulations (e.g, SR-MPLS and SRv6)¶
- Support multiple transport encapsulations within a domain for co-existence and migration¶
- Provide a BGP-based control-plane solution for the use-case illustrated in [RFC8604] together with deployment design guidelines for the leverage of anycast and binding SIDs.¶
5. Scalability
5.1. Scale Requirements
-
Support for massive scaled transport network¶
-
Scalable MPLS dataplane solution¶
- With one label per (C, Remote PE), the 1M MPLS dataplane does not work.¶
-
A notion of hierarchy or segment list is required.¶
- Additionally, PE and transit nodes (ABRs) may be devices with limited forwarding table space¶
- Devices may have constraints on packet processing (e.g., label operations, number of labels pushed) and performance¶
-
Ability to abstract the topology from remote domains - for scale, stability and faster convergence¶
- Abstracting PE and/or ABR related state and network events¶
-
Support for an Emulated-PULL model for the BGP signaling¶
- The SR-PCE solution natively supports a PULL model: when PE1 installs a VPN route V/v via (C, PE2), PE1 requests its serving SR-PCE to compute the SR Policy to (C, PE2). I.e. PE1 does not learn unneeded SR policies.¶
- BGP Signaling is natively a PUSH model.¶
- Emulated-PULL refers to the ability for a BGP CAR node PE1 to "subscribe" to (C, PE2) route such that only the related paths are signaled to PE1.¶
-
The subscription and related filtering solution must apply to any BGP CAR node¶
-
Transport CAR routes¶
-
Service/VPN CAR routes¶
-
Automation of the subscription/filter route¶
- Similar to the SR-PCE solution, when an ingress PE1 installs VPN V/v via (C, PE2), PE1 originates its subscription/filter route for (C, PE2).¶
- Efficient propagation and processing of subscription/filter routes.¶
- Ability to perform aggregation and suppression of subscription/filter routes at nodes in the route propagation path to reduce explosion and churn in propagation of the filter routes themselves.¶
- The solution may be optional for networks that do not have the large scaling requirements¶
-
5.2. Scale Analysis
It is useful to analyze the multiple scaling requirements and specifically the data plane constraints in the context of a few common reference designs and use-cases.¶
A couple of example scenarios are listed below for reference.¶
6. Network Availability
- The BGP CAR solution should provide high network availability for typical deployment topologies, with minimum loss of connectivity in different network failure scenarios.¶
- The network failure scenarios, applicable technologies and design options described in [I-D.ietf-mpls-seamless-mpls] should be used as a reference.¶
-
In the Seamless-MPLS reference topology in previous section:¶
- Failure of intra-domain links should limit loss of connectivity (LoC) to < 50ms. E.g., PE11 to a P node (not shown), 121 to a P node in Domain1 or Domain2)¶
- Failure of an intra-domain node (P node in any domain) should limit LoC to < 50ms¶
- Failure of an ABR node (e.g., 121, 231) should limit LoC to < 1sec¶
- Failure of a remote PE node (e.g., PE3) should limit LoC to < 1sec¶
-
In the Inter-AS Option C VPN reference topology in previous section:¶
- Failure of intra-domain links should limit LoC to < 50ms. E.g., PE11 to a P node (not shown), 121 to a P node in Domain1 or Domain2)¶
- Failure of an intra-domain node (P node in any domain) should limit LoC to < 50ms¶
- Failure of an ASBR node (e.g., 121, 211) should limit LoC to < 1sec¶
- Failure of a remote PE node (e.g., PE3) should limit LoC to < 1sec¶
- Failure of an external link (e.g., 121-211) should limit LoC to < 1sec¶
- The solution should explore and describe additional techniques and design options that are applicable to further improve handling of the failure cases listed above.¶
7. BGP Protocol Requirements
-
Support signaling and distribution of different Color-Aware routes to reach a participating node, e.g., a PE. Intent should be indicated by the notion of a Color as defined in SR Policy Architecture.¶
-
Support for a flexible NLRI definition to accommodate both efficiency of processing (e.g., packing) and future extensibility¶
- Avoid limitations associated with existing SAFI NLRI definitions. For example, 24-bit label.¶
-
Support for validation of paths¶
-
Next-hop resolution for Color-Aware route¶
- Flexibility to use different intra-domain and inter-domain mechanisms - IGP-FA, SR-TE, RSVP-TE, IGP, BGP-LU etc.¶
- Recursive resolution over BGP Color-Aware routes¶
- Ability to carry end-to-end cumulative metric for a given color¶
- Support setting up an end-to-end Color-Aware path using a different/less preferred or best-effort paths in domains where a particular intent is not available¶
-
Separation of transport and VPN service semantics.¶
- Allow for different route distribution planes for service vs transport routes.¶
- Support signaling of different transport encapsulations¶
- Support for signaling multiple encapsulations for co-existence and migration¶
- Generation of BGP Color-Aware routes sourced from IGP-FA, SR-TE policies and BGP-LU from a domain¶
- Support signaling across domains with different color mappings for a given intent.¶
8. Future Considerations
Multicast service intent¶
9. Acknowledgements
Many people contributed to this document.¶
The authors would especially like to thank Jim Uttaro for his guidance on the work and feedback on many aspects of the problem statement. We would also like to thank Daniel Voyer, Luay Jalil and Robert Raszuk for their review and valuable suggestions.¶
We also express our appreciation to Bruno Decreane, Keyur Patel, Jim Guichard, Alex Bogdanov, Dirk Steinberg, Hannes Gredler and Xiaohu Hu for discussions on several topics that have helped provide input to the document. We also thank Huaimo Chen for his valuable review comments.¶
The authors would like to thank Stephane Litkowski for his detailed review and for making valuable suggestions to improve the quality of the document. We would also like to thank Kamran Raza and Kris Michelson for their review and comments on the document and to Simon Spraggs, Jose Liste and Jiri Chaloupka for their early inputs on the problem statement.¶
10. References
10.1. Normative References
- [I-D.agrawal-spring-srv6-mpls-interworking]
- Agrawal, S., ALI, Z., Filsfils, C., Voyer, D., and Z. Li, "SRv6 and MPLS interworking", Work in Progress, Internet-Draft, draft-agrawal-spring-srv6-mpls-interworking-06, , <https://www.ietf.org/archive/id/draft-agrawal-spring-srv6-mpls-interworking-06.txt>.
- [I-D.ietf-bess-srv6-services]
- Dawra, G., Filsfils, C., Talaulikar, K., Raszuk, R., Decraene, B., Zhuang, S., and J. Rabadan, "SRv6 BGP based Overlay Services", Work in Progress, Internet-Draft, draft-ietf-bess-srv6-services-08, , <https://www.ietf.org/archive/id/draft-ietf-bess-srv6-services-08.txt>.
- [I-D.ietf-idr-bgp-ipv6-rt-constrain]
- Patel, K., Raszuk, R., Djernaes, M., Dong, J., and M. Chen, "IPv6 Extensions for Route Target Distribution", Work in Progress, Internet-Draft, draft-ietf-idr-bgp-ipv6-rt-constrain-12, , <https://www.ietf.org/archive/id/draft-ietf-idr-bgp-ipv6-rt-constrain-12.txt>.
- [I-D.ietf-idr-tunnel-encaps]
- Patel, K., Velde, G. V. D., Sangli, S. R., and J. Scudder, "The BGP Tunnel Encapsulation Attribute", Work in Progress, Internet-Draft, draft-ietf-idr-tunnel-encaps-22, , <https://www.ietf.org/archive/id/draft-ietf-idr-tunnel-encaps-22.txt>.
- [I-D.ietf-lsr-flex-algo]
- Psenak, P., Hegde, S., Filsfils, C., Talaulikar, K., and A. Gulko, "IGP Flexible Algorithm", Work in Progress, Internet-Draft, draft-ietf-lsr-flex-algo-18, , <https://www.ietf.org/archive/id/draft-ietf-lsr-flex-algo-18.txt>.
- [I-D.ietf-spring-segment-routing-policy]
- Filsfils, C., Talaulikar, K., Voyer, D., Bogdanov, A., and P. Mattes, "Segment Routing Policy Architecture", Work in Progress, Internet-Draft, draft-ietf-spring-segment-routing-policy-14, , <https://www.ietf.org/archive/id/draft-ietf-spring-segment-routing-policy-14.txt>.
- [I-D.ietf-spring-sr-service-programming]
- Clad, F., Xu, X., Filsfils, C., Bernier, D., Li, C., Decraene, B., Ma, S., Yadlapalli, C., Henderickx, W., and S. Salsano, "Service Programming with Segment Routing", Work in Progress, Internet-Draft, draft-ietf-spring-sr-service-programming-05, , <https://www.ietf.org/archive/id/draft-ietf-spring-sr-service-programming-05.txt>.
- [I-D.ietf-spring-srv6-network-programming]
- Filsfils, C., Garvia, P. C., Leddy, J., Voyer, D., Matsushima, S., and Z. Li, "Segment Routing over IPv6 (SRv6) Network Programming", Work in Progress, Internet-Draft, draft-ietf-spring-srv6-network-programming-28, , <https://www.ietf.org/archive/id/draft-ietf-spring-srv6-network-programming-28.txt>.
- [I-D.voyer-pim-sr-p2mp-policy]
- Voyer, D., Filsfils, C., Parekh, R., Bidgoli, H., and Z. Zhang, "Segment Routing Point-to-Multipoint Policy", Work in Progress, Internet-Draft, draft-voyer-pim-sr-p2mp-policy-02, , <https://www.ietf.org/archive/id/draft-voyer-pim-sr-p2mp-policy-02.txt>.
- [RFC2119]
- Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, , <https://www.rfc-editor.org/info/rfc2119>.
- [RFC4360]
- Sangli, S., Tappan, D., and Y. Rekhter, "BGP Extended Communities Attribute", RFC 4360, DOI 10.17487/RFC4360, , <https://www.rfc-editor.org/info/rfc4360>.
- [RFC4684]
- Marques, P., Bonica, R., Fang, L., Martini, L., Raszuk, R., Patel, K., and J. Guichard, "Constrained Route Distribution for Border Gateway Protocol/MultiProtocol Label Switching (BGP/MPLS) Internet Protocol (IP) Virtual Private Networks (VPNs)", RFC 4684, DOI 10.17487/RFC4684, , <https://www.rfc-editor.org/info/rfc4684>.
- [RFC4760]
- Bates, T., Chandra, R., Katz, D., and Y. Rekhter, "Multiprotocol Extensions for BGP-4", RFC 4760, DOI 10.17487/RFC4760, , <https://www.rfc-editor.org/info/rfc4760>.
- [RFC5512]
- Mohapatra, P. and E. Rosen, "The BGP Encapsulation Subsequent Address Family Identifier (SAFI) and the BGP Tunnel Encapsulation Attribute", RFC 5512, DOI 10.17487/RFC5512, , <https://www.rfc-editor.org/info/rfc5512>.
- [RFC5701]
- Rekhter, Y., "IPv6 Address Specific BGP Extended Community Attribute", RFC 5701, DOI 10.17487/RFC5701, , <https://www.rfc-editor.org/info/rfc5701>.
- [RFC7311]
- Mohapatra, P., Fernando, R., Rosen, E., and J. Uttaro, "The Accumulated IGP Metric Attribute for BGP", RFC 7311, DOI 10.17487/RFC7311, , <https://www.rfc-editor.org/info/rfc7311>.
- [RFC7606]
- Chen, E., Ed., Scudder, J., Ed., Mohapatra, P., and K. Patel, "Revised Error Handling for BGP UPDATE Messages", RFC 7606, DOI 10.17487/RFC7606, , <https://www.rfc-editor.org/info/rfc7606>.
- [RFC8126]
- Cotton, M., Leiba, B., and T. Narten, "Guidelines for Writing an IANA Considerations Section in RFCs", BCP 26, RFC 8126, DOI 10.17487/RFC8126, , <https://www.rfc-editor.org/info/rfc8126>.
- [RFC8174]
- Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, , <https://www.rfc-editor.org/info/rfc8174>.
- [RFC8277]
- Rosen, E., "Using BGP to Bind MPLS Labels to Address Prefixes", RFC 8277, DOI 10.17487/RFC8277, , <https://www.rfc-editor.org/info/rfc8277>.
- [RFC8402]
- Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L., Decraene, B., Litkowski, S., and R. Shakir, "Segment Routing Architecture", RFC 8402, DOI 10.17487/RFC8402, , <https://www.rfc-editor.org/info/rfc8402>.
- [RFC8664]
- Sivabalan, S., Filsfils, C., Tantsura, J., Henderickx, W., and J. Hardwick, "Path Computation Element Communication Protocol (PCEP) Extensions for Segment Routing", RFC 8664, DOI 10.17487/RFC8664, , <https://www.rfc-editor.org/info/rfc8664>.
- [RFC8669]
- Previdi, S., Filsfils, C., Lindem, A., Ed., Sreekantiah, A., and H. Gredler, "Segment Routing Prefix Segment Identifier Extensions for BGP", RFC 8669, DOI 10.17487/RFC8669, , <https://www.rfc-editor.org/info/rfc8669>.
10.2. Informative References
- [I-D.filsfils-spring-sr-policy-considerations]
- Filsfils, C., Talaulikar, K., Krol, P., Horneffer, M., and P. Mattes, "SR Policy Implementation and Deployment Considerations", Work in Progress, Internet-Draft, draft-filsfils-spring-sr-policy-considerations-08, , <https://www.ietf.org/archive/id/draft-filsfils-spring-sr-policy-considerations-08.txt>.
- [I-D.ietf-idr-performance-routing]
- Xu, X., Hegde, S., Talaulikar, K., Boucadair, M., and C. Jacquenet, "Performance-based BGP Routing Mechanism", Work in Progress, Internet-Draft, draft-ietf-idr-performance-routing-03, , <https://www.ietf.org/archive/id/draft-ietf-idr-performance-routing-03.txt>.
- [I-D.ietf-mpls-seamless-mpls]
- Leymann, N., Decraene, B., Filsfils, C., Konstantynowicz, M., and D. Steinberg, "Seamless MPLS Architecture", Work in Progress, Internet-Draft, draft-ietf-mpls-seamless-mpls-07, , <https://www.ietf.org/archive/id/draft-ietf-mpls-seamless-mpls-07.txt>.
- [RFC3906]
- Shen, N. and H. Smit, "Calculating Interior Gateway Protocol (IGP) Routes Over Traffic Engineering Tunnels", RFC 3906, DOI 10.17487/RFC3906, , <https://www.rfc-editor.org/info/rfc3906>.
- [RFC4271]
- Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A Border Gateway Protocol 4 (BGP-4)", RFC 4271, DOI 10.17487/RFC4271, , <https://www.rfc-editor.org/info/rfc4271>.
- [RFC4272]
- Murphy, S., "BGP Security Vulnerabilities Analysis", RFC 4272, DOI 10.17487/RFC4272, , <https://www.rfc-editor.org/info/rfc4272>.
- [RFC4364]
- Rosen, E. and Y. Rekhter, "BGP/MPLS IP Virtual Private Networks (VPNs)", RFC 4364, DOI 10.17487/RFC4364, , <https://www.rfc-editor.org/info/rfc4364>.
- [RFC6952]
- Jethanandani, M., Patel, K., and L. Zheng, "Analysis of BGP, LDP, PCEP, and MSDP Issues According to the Keying and Authentication for Routing Protocols (KARP) Design Guide", RFC 6952, DOI 10.17487/RFC6952, , <https://www.rfc-editor.org/info/rfc6952>.
- [RFC7911]
- Walton, D., Retana, A., Chen, E., and J. Scudder, "Advertisement of Multiple Paths in BGP", RFC 7911, DOI 10.17487/RFC7911, , <https://www.rfc-editor.org/info/rfc7911>.