Internet DRAFT - draft-templin-rtgwg-scalable-bgp
draft-templin-rtgwg-scalable-bgp
Network Working Group F. Templin, Ed.
Internet-Draft G. Saccone
Intended status: Informational Boeing Research & Technology
Expires: August 2, 2019 G. Dawra
LinkedIn
A. Lindem
V. Moreno
Cisco Systems, Inc.
January 29, 2019
Scalable De-Aggregation for Overlays Using the Border Gateway Protocol
(BGP)
draft-templin-rtgwg-scalable-bgp-01.txt
Abstract
The Border Gateway Protocol (BGP) has well-known limitations in terms
of the numbers of routes that can be carried and stability of the
routing system. This is especially true when mobile nodes frequently
change their network attachment points, which in the past has
resulted in excessive announcements and withdrawals of de-aggregated
prefixes. This document discusses a means of accommodating scalable
de-aggregation of IPv6 prefixes for overlay networks using BGP.
Status of This Memo
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This Internet-Draft will expire on August 2, 2019.
Copyright Notice
Copyright (c) 2019 IETF Trust and the persons identified as the
document authors. All rights reserved.
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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
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Overview and Analysis . . . . . . . . . . . . . . . . . . . . 2
3. Opportunities and Limitations . . . . . . . . . . . . . . . . 4
4. Use Cases . . . . . . . . . . . . . . . . . . . . . . . . . . 4
5. Implementation Status . . . . . . . . . . . . . . . . . . . . 4
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
7. Security Considerations . . . . . . . . . . . . . . . . . . . 5
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 5
9.1. Normative References . . . . . . . . . . . . . . . . . . 5
9.2. Informative References . . . . . . . . . . . . . . . . . 5
Appendix A. Change Log . . . . . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6
1. Introduction
The Border Gateway Protocol (BGP) [RFC4271] has well-known
limitations in terms of the numbers of routes that can be carried and
the stability of the routing system. This is especially true for
routing systems that include mobile nodes that frequently change
their network attachment points, which in the past have resulted in
excessive announcements and withdrawals of de-aggregated prefixes.
This document discusses a means of accommodating scalable de-
aggregation of IPv6 prefixes [RFC8200] for overlay networks using
BGP.
2. Overview and Analysis
As discussed in [I-D.ietf-rtgwg-atn-bgp] and
[I-D.templin-intarea-6706bis], the method for accommodating de-
aggregation is to institute an overlay network instance of BGP that
is separate and independent from the global Internet BGP routing
system. The overlay is presented to the global Internet as a small
number of aggregated IPv6 prefixes (also known as Mobility Service
Prefixes (MSPs)) that never change. In this way, the Internet BGP
routing system sees only stable aggregated MSPs (e.g., 2001:db8::/32)
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and is completely unaware of any de-aggregation or mobility-related
churn that may be occurring within the overlay.
The overlay is operated by an Overlay Service Provider (OSP), and
consists of a core Autonomous System (AS) with core AS Border Routers
(c-ASBRs) that connect to stub ASes with stub ASBRs (s-ASBRs) in a
hub-and-spokes fashion. Mobile nodes associate with nearby (i.e.,
regional) stub ASes for extended timeframes, and change to new stub
ASes only after movements of significant topological or geographical
distance. Mobility-related changes between stub ASes are therefore
normally infrequent.
The s-ASBRs use eBGP to announce de-aggregated Mobile Network
Prefixes (MNPs) of mobile nodes (e.g., 2001:db8:1:2::/64, etc.) to
their neighboring c-ASBRs, but do not announce fine-grained mobility
events such as a mobile node moving to a new network attachment
point. Instead, mobile nodes coordinate with stub ASes using
mobility protocols such as MIPv6, LISP, AERO, etc. and stub ASes
accommodate these localized mobility events without disturbing the
c-ASBRs.
The c-ASBRs originate "default" to their neighboring s-ASBRs but do
not announce any MNP routes. In this way, MNP announcements and
withdrawals are unidirectional from s-ASBRs to c-ASBRs only, thereby
suppressing BGP updates on the reverse path. The c-ASBRs in turn use
iBGP to maintain a consistent view of the full topology. BGP Route
Reflectors (RRs) [RFC4456] can also be used to support increased
c-ASBR scaling.
Each c-ASBR should be able to carry at least as many routes as a
typical core router in the global public Internet BGP routing system.
Since the number of active routes in the Internet is rapidly
approaching 1 million (1M), viable c-ASBRs must be capable of
carrying at least 1M MNP routes (this has been proven even for BGP
running on lightweight virtual machines). The method for increasing
scaling therefore is to divide the MSP into longer sub-MSPs, and to
assign a different set of c-ASBRs for each sub-MSP.
For example, the MSP 2001:db8::/32 could be sub-divided into sub-MSPs
such as 2001:db8:0010::/44, 2001:db8:0020::/44, 2001:db8:0030::/44,
etc. with each sub-MSP assigned to a different set of c-ASBRs. Each
s-ASBR peers with at least one member of each c-ASBR set and uses
route filters such that BGP updates are only sent to the c-ASBR(s)
that aggregate the specific sub-MSP. Then, assuming 1 thousand (1K)
or more sub-MSPs (each with its own set of c-ASBRs) the entire BGP
overlay routing system should be able to service 1 billion (1B) MNPs
or more.
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3. Opportunities and Limitations
Since a lightweight virtual machine (e.g., a linux image running
quagga in the cloud) can service up to 1M MNPs using BGP, it is
likely that dedicated high-performance IPv6 router hardware could
support even more. With such dedicated high-performance hardware,
the number of MNPs could be increased further.
The deployed numbers of s-ASBRs even for very large overlays should
not exceed a c-ASBR's capacity for BGP peering sessions. For
example, c-ASBRs should be capable of servicing1K or more BGP peering
sessions, with the upper bound limited by keepalive and update
control messaging overhead. Conversely, s-ASBRs should be capable of
supporting even more sessions since they only receive keepalives and
only send updates for mobile nodes within their local stub ASes.
Mobile nodes should refrain from moving rapidly between stub ASes for
no good reason, since the objective is only to reduce routing stretch
due to movement of significant distances. OSPs could employ
disincentives such as surcharge penalties for gratuitous mobility,
but intentional abuse would also yield little reward since only the
bad actor (i.e., and not others) would be subject to MNP instability.
Packets sent between mobile nodes that associate with different stub
ASes would initially need to be forwarded through the core AS, which
presents a forwarding bottleneck. For this reason, a route
optimization function is needed to reduce congestion in the core.
Since c-ASBRs should be commercial off-the-shelf (COTS) dedicated
high-performance IPv6 routers, however, they should not be required
to participate directly in any out-of-band route optimization
signaling. Instead, route optimization should be coordinated by stub
AS network elements and/or the mobile nodes themselves.
4. Use Cases
Use cases include Unmanned Air Systems (UAS) in controlled and
uncontrolled airspaces, Intelligent Transportation Systems (ITS) in
urban air/ground mobility environments, aviation networks, enterprise
mobile device users, and cellular network users. Any other use cases
in which an OSP services large numbers of mobile nodes are also in
scope.
5. Implementation Status
The arrangement of stub and core ASes described in this document has
been implemented using standards-compliant linux operating systems
and BGP routing protocol implementations (i.e., quagga). No new code
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was included, and all requirements were satisfied through standard
configuration options.
6. IANA Considerations
This document does not introduce any IANA considerations.
7. Security Considerations
Security considerations are discussed in the references.
8. Acknowledgements
This work is aligned with the FAA as per the SE2025 contract number
DTFAWA-15-D-00030.
This work is aligned with the NASA Safe Autonomous Systems Operation
(SASO) program under NASA contract number NNA16BD84C.
This work is aligned with the Boeing Information Technology (BIT)
MobileNet program.
9. References
9.1. Normative References
[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>.
[RFC4456] Bates, T., Chen, E., and R. Chandra, "BGP Route
Reflection: An Alternative to Full Mesh Internal BGP
(IBGP)", RFC 4456, DOI 10.17487/RFC4456, April 2006,
<https://www.rfc-editor.org/info/rfc4456>.
[RFC8200] Deering, S. and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", STD 86, RFC 8200,
DOI 10.17487/RFC8200, July 2017,
<https://www.rfc-editor.org/info/rfc8200>.
9.2. Informative References
[I-D.ietf-rtgwg-atn-bgp]
Templin, F., Saccone, G., Dawra, G., Lindem, A., and V.
Moreno, "A Simple BGP-based Mobile Routing System for the
Aeronautical Telecommunications Network", draft-ietf-
rtgwg-atn-bgp-01 (work in progress), January 2019.
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[I-D.templin-intarea-6706bis]
Templin, F., "Asymmetric Extended Route Optimization
(AERO)", draft-templin-intarea-6706bis-03 (work in
progress), December 2018.
Appendix A. Change Log
<< RFC Editor - remove prior to publication >>
Changes from -00 to -01:
o added Route Reflectors
o introduced term "Overlay Service Provider (OSP)"
o removed estimate of number of routes for high-performance routers
o revised text on route optimization
o added use case and implementation sections
Status as of 01/23/2018:
o -00 draft published
Authors' Addresses
Fred L. Templin (editor)
Boeing Research & Technology
P.O. Box 3707
Seattle, WA 98124
USA
Email: fltemplin@acm.org
Greg Saccone
Boeing Research & Technology
P.O. Box 3707
Seattle, WA 98124
USA
Email: gregory.t.saccone@boeing.com
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Gaurav Dawra
LinkedIn
USA
Email: gdawra.ietf@gmail.com
Acee Lindem
Cisco Systems, Inc.
USA
Email: acee@cisco.com
Victor Moreno
Cisco Systems, Inc.
USA
Email: vimoreno@cisco.com
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