--- 1/draft-ietf-idr-bgp-optimal-route-reflection-23.txt 2021-05-31 08:13:12.341855821 -0700 +++ 2/draft-ietf-idr-bgp-optimal-route-reflection-24.txt 2021-05-31 08:13:12.369856519 -0700 @@ -1,25 +1,25 @@ IDR Working Group R. Raszuk, Ed. Internet-Draft NTT Network Innovations Intended status: Standards Track C. Cassar -Expires: November 13, 2021 Tesla +Expires: December 2, 2021 E. Aman B. Decraene, Ed. Orange K. Wang Juniper Networks - May 12, 2021 + May 31, 2021 BGP Optimal Route Reflection (BGP-ORR) - draft-ietf-idr-bgp-optimal-route-reflection-23 + draft-ietf-idr-bgp-optimal-route-reflection-24 Abstract This document defines an extension to BGP route reflectors. On route reflectors, BGP route selection is modified in order to choose the best route from the standpoint of their clients, rather than from the standpoint of the route reflectors. Depending on the scaling and precision requirements, route selection can be specific for one client, common for a set of clients or common for all clients of a route reflector. This solution is particularly applicable in @@ -41,21 +41,21 @@ 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 November 13, 2021. + This Internet-Draft will expire on December 2, 2021. 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 @@ -71,22 +71,22 @@ 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 3. Modifications to BGP Route Selection . . . . . . . . . . . . 4 3.1. Route Selection from a different IGP location . . . . . . 5 3.1.1. Restriction when BGP next hop is a BGP prefix . . . . 6 3.2. Multiple Route Selections . . . . . . . . . . . . . . . . 6 4. Deployment Considerations . . . . . . . . . . . . . . . . . . 6 5. Security Considerations . . . . . . . . . . . . . . . . . . . 8 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8 7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 8 8. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 8 - 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 8 - 9.1. Normative References . . . . . . . . . . . . . . . . . . 8 + 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 9 + 9.1. Normative References . . . . . . . . . . . . . . . . . . 9 9.2. Informative References . . . . . . . . . . . . . . . . . 9 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10 1. Introduction There are three types of BGP deployments within Autonomous Systems today: full mesh, confederations and route reflection. BGP route reflection [RFC4456] is the most popular way to distribute BGP routes between BGP speakers belonging to the same Autonomous System. However, in some situations, this method suffers from non-optimal @@ -152,23 +152,24 @@ "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here. 3. Modifications to BGP Route Selection The core of this solution is the ability for an operator to specify the IGP location for which the route reflector calculates interior cost for the NEXT_HOP. The IGP location is defined as a node in the - IGP topology and may be configured on a per route reflector basis, - per set of clients, or per client basis. This ability enables the - route reflector to send to a given set of clients routes with + IGP topology, it is identified by an IP address of this node (e.g. a + loopback address), and may be configured on a per route reflector + basis, per set of clients, or per client basis. This ability enables + the route reflector to send to a given set of clients routes with shortest distance to the next hops from the position of the selected IGP location. This provides for freedom of route reflector physical location, and allows transient or permanent migration of this network control plane function to an arbitrary location. The choice of specific granularity (route reflector, set of clients, or client) is configured by the network operator. An implementation is considered compliant with this document if it supports at least one listed grouping of IGP location. @@ -221,26 +222,22 @@ interior cost. The interior cost of a route is determined by calculating the metric from the selected IGP location to the NEXT_HOP for the route using the shortest IGP path tree rooted at the selected IGP location. In order to be able to compute the shortest path tree rooted at the selected IGP locations, knowledge of the IGP topology for the area/ level that includes each of those locations is needed. This knowledge can be gained with the use of the link state IGP such as IS-IS [ISO10589] or OSPF [RFC2328] [RFC5340] or via BGP-LS [RFC7752]. - - The way the IGP location is configured is outside the scope of this - document. The operator may configure it manually, an implementation - may automate it based on heuristics, or it can be computed centrally - and configured by an external system. One or more backup locations - SHOULD be allowed to be specified for redundancy. + One or more backup IGP locations SHOULD be allowed to be specified + for redundancy. 3.1.1. Restriction when BGP next hop is a BGP prefix In situations where the BGP next hop is a BGP prefix itself, the IGP metric of a route used for its resolution SHOULD be the final IGP cost to reach such next hop. Implementations which can not inform BGP of the final IGP metric to a recursive next hop MUST treat such paths as least preferred during next hop metric comparison. However such paths MUST still be considered valid for BGP Phase 2 Route Selection. @@ -293,72 +290,88 @@ networks as well as in end-to-end tunneled environments. In networks where there are multiple route reflectors and hop-by-hop forwarding without encapsulation, such optimizations SHOULD be enabled in a consistent way on all route reflectors. Otherwise, clients may receive an inconsistent view of the network, in turn leading to intra-domain forwarding loops. As discussed in section 11 of [RFC4456], the IGP locations of BGP route reflectors is important and has routing implications. This equally applies to the choice of the IGP locations configured on - optimal route reflectors. After selecting suitable IGP locations, an - operator may let one or multiple route reflectors handle route - selection for all of them. The operator may alternatively deploy one - or multiple route reflector for each IGP location or create any - design in between. This choice may depend on operational model - (centralized vs per region), acceptable blast radius in case of - failure, acceptable number of IBGP sessions for the mesh between the - route reflectors, performance and configuration granularity of the - equipment. + optimal route reflectors. If a backup location is provided, it is + used when the primary IGP location disappears from the IGP (i.e. + fails). Just like the failure of a RR [RFC4456], it may result in + changing the paths selected and advertised to the clients and in + general the post-failure paths are expected to be less optimal. This + is dependent on the IGP topologies and the IGP distance between the + primary and the backup IGP locations: the smaller the distance the + smaller the potential impact. + + After selecting suitable IGP locations, an operator may let one or + multiple route reflectors handle route selection for all of them. + The operator may alternatively deploy one or multiple route reflector + for each IGP location or create any design in between. This choice + may depend on operational model (centralized vs per region), + acceptable blast radius in case of failure, acceptable number of IBGP + sessions for the mesh between the route reflectors, performance and + configuration granularity of the equipment. With this approach, an ISP can effect a hot potato routing policy even if route reflection has been moved out of the forwarding plane, and hop-by-hop switching has been replaced by end-to-end MPLS or IP encapsulation. Compared with a deployment of ADD-PATH on all routers, BGP ORR reduces the amount of state which needs to be pushed to the edge of the network in order to perform hot potato routing. Modifying the IGP location of BGP ORR does not interfere with policies enforced before IGP tie-breaking (step e) in the BGP Decision Process Route. Calculating routes for different IGP locations requires multiple SPF calculations and multiple (subsets of) BGP Decision Processes, which requires more computing resources. This document allows for different granularity such as one Decision Process per route reflector, per set of clients or per client. A more fine grained granularity may translate into more optimal hot potato routing at the - cost of more computing power. The ability to run fine grained - computations depends on the platform/hardware deployed, the number of - clients, the number of BGP routes and the size of the IGP topology. - In essence, sizing considerations are similar to the deployments of - BGP Route Reflector. + cost of more computing power. Selecting to configure an IGP location + per client has the highest precision as each client can be associated + with their ideal (own) IGP location. However, doing so may have an + impact on the performance (as explained above). Using an IGP + location per set of clients implies a loss of precision, but reduces + the impact on the performance of the route reflector. Similarly, if + an IGP location is selected for the whole routing instance, the + lowest precision is achieved but the performance impact is minimal + (both should be equal to the [RFC4456] ones). The ability to run + fine grained computations depends on the platform/hardware deployed, + the number of clients, the number of BGP routes and the size of the + IGP topology. In essence, sizing considerations are similar to the + deployments of BGP Route Reflector. 5. Security Considerations Similarly to [RFC4456], this extension to BGP does not change the underlying security issues inherent in the existing IBGP. This document does not introduce requirements for any new protection measures. 6. IANA Considerations This document does not request any IANA allocations. 7. Acknowledgments Authors would like to thank Keyur Patel, Eric Rosen, Clarence Filsfils, Uli Bornhauser, Russ White, Jakob Heitz, Mike Shand, Jon Mitchell, John Scudder, Jeff Haas, Martin Djernaes, Daniele - Ceccarelli, Kieran Milne, Job Snijders and Randy Bush for their - valuable input. + Ceccarelli, Kieran Milne, Job Snijders, Randy Bush and Alvaro Retana + for their valuable input. 8. Contributors Following persons substantially contributed to the current format of the document: Stephane Litkowski Cisco System slitkows.ietf@gmail.com @@ -429,33 +441,28 @@ . Authors' Addresses Robert Raszuk (editor) NTT Network Innovations Email: robert@raszuk.net Christian Cassar - Tesla - 43 Avro Way - Weybridge KT13 0XY - UK - Email: ccassar@tesla.com + Email: cassar.christian@gmail.com Erik Aman Email: erik.aman@aman.se Bruno Decraene (editor) Orange Email: bruno.decraene@orange.com - Kevin Wang Juniper Networks 10 Technology Park Drive Westford, MA 01886 USA Email: kfwang@juniper.net