draft-ietf-idr-bgp-optimal-route-reflection-23.txt   draft-ietf-idr-bgp-optimal-route-reflection-24.txt 
IDR Working Group R. Raszuk, Ed. IDR Working Group R. Raszuk, Ed.
Internet-Draft NTT Network Innovations Internet-Draft NTT Network Innovations
Intended status: Standards Track C. Cassar Intended status: Standards Track C. Cassar
Expires: November 13, 2021 Tesla Expires: December 2, 2021
E. Aman E. Aman
B. Decraene, Ed. B. Decraene, Ed.
Orange Orange
K. Wang K. Wang
Juniper Networks Juniper Networks
May 12, 2021 May 31, 2021
BGP Optimal Route Reflection (BGP-ORR) BGP Optimal Route Reflection (BGP-ORR)
draft-ietf-idr-bgp-optimal-route-reflection-23 draft-ietf-idr-bgp-optimal-route-reflection-24
Abstract Abstract
This document defines an extension to BGP route reflectors. On route This document defines an extension to BGP route reflectors. On route
reflectors, BGP route selection is modified in order to choose the reflectors, BGP route selection is modified in order to choose the
best route from the standpoint of their clients, rather than from the best route from the standpoint of their clients, rather than from the
standpoint of the route reflectors. Depending on the scaling and standpoint of the route reflectors. Depending on the scaling and
precision requirements, route selection can be specific for one precision requirements, route selection can be specific for one
client, common for a set of clients or common for all clients of a client, common for a set of clients or common for all clients of a
route reflector. This solution is particularly applicable in route reflector. This solution is particularly applicable in
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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-
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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 November 13, 2021. This Internet-Draft will expire on December 2, 2021.
Copyright Notice Copyright Notice
Copyright (c) 2021 IETF Trust and the persons identified as the Copyright (c) 2021 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
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of (https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
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2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Modifications to BGP Route Selection . . . . . . . . . . . . 4 3. Modifications to BGP Route Selection . . . . . . . . . . . . 4
3.1. Route Selection from a different IGP location . . . . . . 5 3.1. Route Selection from a different IGP location . . . . . . 5
3.1.1. Restriction when BGP next hop is a BGP prefix . . . . 6 3.1.1. Restriction when BGP next hop is a BGP prefix . . . . 6
3.2. Multiple Route Selections . . . . . . . . . . . . . . . . 6 3.2. Multiple Route Selections . . . . . . . . . . . . . . . . 6
4. Deployment Considerations . . . . . . . . . . . . . . . . . . 6 4. Deployment Considerations . . . . . . . . . . . . . . . . . . 6
5. Security Considerations . . . . . . . . . . . . . . . . . . . 8 5. Security Considerations . . . . . . . . . . . . . . . . . . . 8
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 8 7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 8
8. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 8 8. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 8
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 8 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 9
9.1. Normative References . . . . . . . . . . . . . . . . . . 8 9.1. Normative References . . . . . . . . . . . . . . . . . . 9
9.2. Informative References . . . . . . . . . . . . . . . . . 9 9.2. Informative References . . . . . . . . . . . . . . . . . 9
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10
1. Introduction 1. Introduction
There are three types of BGP deployments within Autonomous Systems There are three types of BGP deployments within Autonomous Systems
today: full mesh, confederations and route reflection. BGP route today: full mesh, confederations and route reflection. BGP route
reflection [RFC4456] is the most popular way to distribute BGP routes reflection [RFC4456] is the most popular way to distribute BGP routes
between BGP speakers belonging to the same Autonomous System. between BGP speakers belonging to the same Autonomous System.
However, in some situations, this method suffers from non-optimal However, in some situations, this method suffers from non-optimal
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"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP "OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here. capitals, as shown here.
3. Modifications to BGP Route Selection 3. Modifications to BGP Route Selection
The core of this solution is the ability for an operator to specify The core of this solution is the ability for an operator to specify
the IGP location for which the route reflector calculates interior 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 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, IGP topology, it is identified by an IP address of this node (e.g. a
per set of clients, or per client basis. This ability enables the loopback address), and may be configured on a per route reflector
route reflector to send to a given set of clients routes with 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 shortest distance to the next hops from the position of the selected
IGP location. This provides for freedom of route reflector physical IGP location. This provides for freedom of route reflector physical
location, and allows transient or permanent migration of this network location, and allows transient or permanent migration of this network
control plane function to an arbitrary location. control plane function to an arbitrary location.
The choice of specific granularity (route reflector, set of clients, The choice of specific granularity (route reflector, set of clients,
or client) is configured by the network operator. An implementation or client) is configured by the network operator. An implementation
is considered compliant with this document if it supports at least is considered compliant with this document if it supports at least
one listed grouping of IGP location. one listed grouping of IGP location.
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interior cost. The interior cost of a route is determined by interior cost. The interior cost of a route is determined by
calculating the metric from the selected IGP location to the calculating the metric from the selected IGP location to the
NEXT_HOP for the route using the shortest IGP path tree rooted at NEXT_HOP for the route using the shortest IGP path tree rooted at
the selected IGP location. the selected IGP location.
In order to be able to compute the shortest path tree rooted at the 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/ selected IGP locations, knowledge of the IGP topology for the area/
level that includes each of those locations is needed. This level that includes each of those locations is needed. This
knowledge can be gained with the use of the link state IGP such as 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]. IS-IS [ISO10589] or OSPF [RFC2328] [RFC5340] or via BGP-LS [RFC7752].
One or more backup IGP locations SHOULD be allowed to be specified
The way the IGP location is configured is outside the scope of this for redundancy.
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.
3.1.1. Restriction when BGP next hop is a BGP prefix 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 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 metric of a route used for its resolution SHOULD be the final IGP
cost to reach such next hop. Implementations which can not inform 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 BGP of the final IGP metric to a recursive next hop MUST treat such
paths as least preferred during next hop metric comparison. However paths as least preferred during next hop metric comparison. However
such paths MUST still be considered valid for BGP Phase 2 Route such paths MUST still be considered valid for BGP Phase 2 Route
Selection. Selection.
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networks as well as in end-to-end tunneled environments. In networks networks as well as in end-to-end tunneled environments. In networks
where there are multiple route reflectors and hop-by-hop forwarding where there are multiple route reflectors and hop-by-hop forwarding
without encapsulation, such optimizations SHOULD be enabled in a without encapsulation, such optimizations SHOULD be enabled in a
consistent way on all route reflectors. Otherwise, clients may consistent way on all route reflectors. Otherwise, clients may
receive an inconsistent view of the network, in turn leading to receive an inconsistent view of the network, in turn leading to
intra-domain forwarding loops. intra-domain forwarding loops.
As discussed in section 11 of [RFC4456], the IGP locations of BGP As discussed in section 11 of [RFC4456], the IGP locations of BGP
route reflectors is important and has routing implications. This route reflectors is important and has routing implications. This
equally applies to the choice of the IGP locations configured on equally applies to the choice of the IGP locations configured on
optimal route reflectors. After selecting suitable IGP locations, an optimal route reflectors. If a backup location is provided, it is
operator may let one or multiple route reflectors handle route used when the primary IGP location disappears from the IGP (i.e.
selection for all of them. The operator may alternatively deploy one fails). Just like the failure of a RR [RFC4456], it may result in
or multiple route reflector for each IGP location or create any changing the paths selected and advertised to the clients and in
design in between. This choice may depend on operational model general the post-failure paths are expected to be less optimal. This
(centralized vs per region), acceptable blast radius in case of is dependent on the IGP topologies and the IGP distance between the
failure, acceptable number of IBGP sessions for the mesh between the primary and the backup IGP locations: the smaller the distance the
route reflectors, performance and configuration granularity of the smaller the potential impact.
equipment.
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 With this approach, an ISP can effect a hot potato routing policy
even if route reflection has been moved out of the forwarding plane, 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 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 encapsulation. Compared with a deployment of ADD-PATH on all
routers, BGP ORR reduces the amount of state which needs to be pushed 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. to the edge of the network in order to perform hot potato routing.
Modifying the IGP location of BGP ORR does not interfere with Modifying the IGP location of BGP ORR does not interfere with
policies enforced before IGP tie-breaking (step e) in the BGP policies enforced before IGP tie-breaking (step e) in the BGP
Decision Process Route. Decision Process Route.
Calculating routes for different IGP locations requires multiple SPF Calculating routes for different IGP locations requires multiple SPF
calculations and multiple (subsets of) BGP Decision Processes, which calculations and multiple (subsets of) BGP Decision Processes, which
requires more computing resources. This document allows for requires more computing resources. This document allows for
different granularity such as one Decision Process per route 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 granularity may translate into more optimal hot potato routing at the
cost of more computing power. The ability to run fine grained cost of more computing power. Selecting to configure an IGP location
computations depends on the platform/hardware deployed, the number of per client has the highest precision as each client can be associated
clients, the number of BGP routes and the size of the IGP topology. with their ideal (own) IGP location. However, doing so may have an
In essence, sizing considerations are similar to the deployments of impact on the performance (as explained above). Using an IGP
BGP Route Reflector. 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 5. Security Considerations
Similarly to [RFC4456], this extension to BGP does not change the Similarly to [RFC4456], this extension to BGP does not change the
underlying security issues inherent in the existing IBGP. underlying security issues inherent in the existing IBGP.
This document does not introduce requirements for any new protection This document does not introduce requirements for any new protection
measures. measures.
6. IANA Considerations 6. IANA Considerations
This document does not request any IANA allocations. This document does not request any IANA allocations.
7. Acknowledgments 7. Acknowledgments
Authors would like to thank Keyur Patel, Eric Rosen, Clarence Authors would like to thank Keyur Patel, Eric Rosen, Clarence
Filsfils, Uli Bornhauser, Russ White, Jakob Heitz, Mike Shand, Jon Filsfils, Uli Bornhauser, Russ White, Jakob Heitz, Mike Shand, Jon
Mitchell, John Scudder, Jeff Haas, Martin Djernaes, Daniele Mitchell, John Scudder, Jeff Haas, Martin Djernaes, Daniele
Ceccarelli, Kieran Milne, Job Snijders and Randy Bush for their Ceccarelli, Kieran Milne, Job Snijders, Randy Bush and Alvaro Retana
valuable input. for their valuable input.
8. Contributors 8. Contributors
Following persons substantially contributed to the current format of Following persons substantially contributed to the current format of
the document: the document:
Stephane Litkowski Stephane Litkowski
Cisco System Cisco System
slitkows.ietf@gmail.com slitkows.ietf@gmail.com
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<https://www.rfc-editor.org/info/rfc7911>. <https://www.rfc-editor.org/info/rfc7911>.
Authors' Addresses Authors' Addresses
Robert Raszuk (editor) Robert Raszuk (editor)
NTT Network Innovations NTT Network Innovations
Email: robert@raszuk.net Email: robert@raszuk.net
Christian Cassar Christian Cassar
Tesla
43 Avro Way
Weybridge KT13 0XY
UK
Email: ccassar@tesla.com Email: cassar.christian@gmail.com
Erik Aman Erik Aman
Email: erik.aman@aman.se Email: erik.aman@aman.se
Bruno Decraene (editor) Bruno Decraene (editor)
Orange Orange
Email: bruno.decraene@orange.com Email: bruno.decraene@orange.com
Kevin Wang Kevin Wang
Juniper Networks Juniper Networks
10 Technology Park Drive 10 Technology Park Drive
Westford, MA 01886 Westford, MA 01886
USA USA
Email: kfwang@juniper.net Email: kfwang@juniper.net
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