--- 1/draft-ietf-idr-bgp-optimal-route-reflection-24.txt 2021-06-14 15:13:42.608022831 -0700 +++ 2/draft-ietf-idr-bgp-optimal-route-reflection-25.txt 2021-06-14 15:13:42.636023536 -0700 @@ -1,25 +1,25 @@ IDR Working Group R. Raszuk, Ed. Internet-Draft NTT Network Innovations -Intended status: Standards Track C. Cassar -Expires: December 2, 2021 +Intended status: Standards Track B. Decraene, Ed. +Expires: December 16, 2021 Orange + C. Cassar + E. Aman - B. Decraene, Ed. - Orange K. Wang Juniper Networks - May 31, 2021 + June 14, 2021 BGP Optimal Route Reflection (BGP-ORR) - draft-ietf-idr-bgp-optimal-route-reflection-24 + draft-ietf-idr-bgp-optimal-route-reflection-25 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 December 2, 2021. + This Internet-Draft will expire on December 16, 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 @@ -107,29 +107,29 @@ Section 11 of [RFC4456] describes a deployment approach and a set of constraints which, if satisfied, would result in the deployment of route reflection yielding the same results as the IBGP full mesh approach. This deployment approach makes route reflection compatible with the application of hot potato routing policy. In accordance with these design rules, route reflectors have often been deployed in the forwarding path and carefully placed on the POP to core boundaries. The evolving model of intra-domain network design has enabled - deployments of route reflectors outside of the forwarding path. - Initially this model was only employed for new services, e.g. IP + deployments of route reflectors outside the forwarding path. + Initially this model was only employed for new services, e.g., IP VPNs [RFC4364], however it has been gradually extended to other BGP - services including IPv4 and IPv6 Internet. In such environments, hot - potato routing policy remains desirable. + services, including the IPv4 and IPv6 Internet. In such + environments, hot potato routing policy remains desirable. - Route reflectors outside of the forwarding path can be placed on the - POP to core boundaries, but they are often placed in arbitrary - locations in the core of large networks. + Route reflectors outside the forwarding path can be placed on the POP + to core boundaries, but they are often placed in arbitrary locations + in the core of large networks. Such deployments suffer from a critical drawback in the context of BGP Route Selection: A route reflector with knowledge of multiple paths for a given prefix will typically pick its best path and only advertise that best path to its clients. If the best path for a prefix is selected on the basis of an IGP tie-break, the path advertised will be the exit point closest to the route reflector. However, the clients are in a different place in the network topology than the route reflector. In networks where the route reflectors are not in the forwarding path, this difference will be even more acute. @@ -152,50 +152,50 @@ "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, it is identified by an IP address of this node (e.g. a + 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. For purposes of route selection, the perspective of a client can differ from that of a route reflector or another client in two distinct ways: - o it has a different position in the IGP topology, and + o it has a different position in the IGP topology, o it can have a different routing policy. These factors correspond to the issues described earlier. This document defines, for BGP Route Reflectors [RFC4456], two changes to the BGP Route Selection algorithm: o The first change, introduced in Section 3.1, is related to the IGP cost to the BGP Next Hop in the BGP decision process. The change - consists in using the IGP cost from a different IGP location than + consists of using the IGP cost from a different IGP location than the route reflector itself. o The second change, introduced in Section 3.2, is to extend the granularity of the BGP decision process, to allow for running multiple decisions processes using different perspective or policies. A significant advantage of these approaches is that the route reflector clients do not need to be modified. @@ -229,25 +229,24 @@ 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]. 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. + cost to reach such next hop. Implementations which cannot 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. 3.2. Multiple Route Selections BGP Route Reflector as per [RFC4456] runs a single BGP Decision Process. Optimal route reflection may require multiple BGP Decision Processes or subsets of the Decision Process in order to consider different IGP locations or BGP policies for different sets of clients. If the required routing optimization is limited to the IGP cost to @@ -282,24 +281,24 @@ user configured policies. The achievement of optimal routing between clients of different clusters relies upon all route reflectors learning all paths that are eligible for consideration. In order to satisfy this requirement, BGP add-path [RFC7911] needs to be deployed between route reflectors. This solution can be deployed in traditional hop-by-hop forwarding 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. + without encapsulation, such optimizations SHOULD be consistently + enabled 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. 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 @@ -323,55 +322,58 @@ 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 + 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. 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 + 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, + 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 extension provides a new metric value using additional + information for computing routes for BGP router reflectors. While + any improperly used metric value could impact the resiliency of the + network, this extension does not change the underlying security + issues inherent in the existing IBGP per [RFC4456]. 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, Randy Bush and Alvaro Retana - for their valuable input. + Ceccarelli, Kieran Milne, Job Snijders, Randy Bush, Alvaro Retana and + Lars Eggert 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 @@ -440,29 +443,29 @@ DOI 10.17487/RFC7911, July 2016, . Authors' Addresses Robert Raszuk (editor) NTT Network Innovations Email: robert@raszuk.net + Bruno Decraene (editor) + Orange + + Email: bruno.decraene@orange.com + Christian Cassar 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