Internet DRAFT - draft-duan-bess-mvpn-ipv6-infras
draft-duan-bess-mvpn-ipv6-infras
Network Working Group F. Duan
Internet-Draft J. Xie
Updates: 6514 (if approved) S. Chen
Intended status: Standards Track Huawei Technologies
Expires: 24 May 2024 21 November 2023
BGP MVPN in IPv6 Infrastructure Networks: Problems and Solution
Approaches
draft-duan-bess-mvpn-ipv6-infras-05
Abstract
MVPN deployment faces some problems while used in provider's IPv6
infrastructure networks. This document describes these problems, and
corresponding solutions.
Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"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.
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
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Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
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material or to cite them other than as "work in progress."
This Internet-Draft will expire on 24 May 2024.
Copyright Notice
Copyright (c) 2023 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/
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Please review these documents carefully, as they describe your rights
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 2
3. Problems and Solutions . . . . . . . . . . . . . . . . . . . 2
3.1. Problems . . . . . . . . . . . . . . . . . . . . . . . . 2
3.2. Modification of C-Multicast Route NLRI . . . . . . . . . 4
3.3. Route Reflection Control . . . . . . . . . . . . . . . . 6
4. Security Considerations . . . . . . . . . . . . . . . . . . . 6
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 6
7. Normative References . . . . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7
1. Introduction
BGP MVPN procedure is defined in [RFC6514]. As a mature MVPN
technology, it has been accepted by most operators and vendors. In
[RFC6515], BGP MVPN is updated for IPv6 infrastructure networks.
However, the deployment of BGP MVPN in IPv6 network still faces some
problems. This document describes these problems and corresponding
solutions.
2. Terminology
Readers of this document are assumed to be familiar with the
terminology and concepts of the documents listed as Normative
References.
3. Problems and Solutions
3.1. Problems
In [RFC6514] and [RFC6515], the following issues are critical for
IPv6 infrastructure scenarios while a non-segmented inter-AS P-tunnel
is being established between root PE and its leaf PEs, of which the
reason is that the Source AS field (4 octets) of C-multicast route
cannot hold a IPv6 address (16 octets).
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1. In order to distinguish the C-multicast routes for a specific
multicast c-flow (C-S, C-G) sent to different root PEs, section
11.1.3 of [RFC6514] proposed that "To support non-segmented
inter-AS tunnels, the Source AS field in the C-multicast route is
set to value of the Originating Router's IP Address field of the
found Intra-AS I-PMSI A-D route". However, in NLRI of
C-multicast route, Source AS field is 4 octets in length, while
the Originating Router's IP Address field of Intra-AS I-PMSI A-D
route is 16 octets length in provider's IPv6 networks. The
4-octet Source AS field cannot hold the Originating Router's IP
Address in IPv6 network.
2. In order to control the propagation of C-multicast routes between
different ASes, section 11.2 of [RFC6514] proposed that "Instead
of matching the RD and Source AS carried in the C-multicast route
against the RD and Source AS of an Inter-AS I-PMSI A-D route, the
ASBR should match it against the RD and the Originating Router's
IP Address of the Intra-AS I-PMSI A-D routes". However, Source
AS field in NLRI of C-multicast route cannot be translated to the
Originating Router's IP Address of the Intra-AS I-PMSI A-D routes
in provider's IPv6 networks, because of the mismatch of their
field length.
In the process of evolution to IPv6, IPv4 and IPv6 infrastructure
addresses will coexist in the provider's network. The following
figure is an example of BGP MVPN evolution to IPv6.
+-----------+ +---+ +---+ +-----------+
| +-------+ | | | | | | +-------+ |
| | O-MVRF| |=BGP Peer4=| | | |=BGP Peer4=| | O-MVRF| |
| +-------+ | | | | | | +-------+ |
| | | | | | | |
| PE1 | |RR1| ... |RRn| | PE2 |
| | | | | | | |
| +-------+ | | | | | | +-------+ |
| | N-MVRF| |=BGP Peer6=| | | |=BGP Peer6=| | N-MVRF| |
| +-------+ | | | | | | +-------+ |
+-----------+ +---+ +---+ +-----------+
O-MVRF = Old Multicast VRF using IPv4 infrastructure addresses
N-MVRF = New Multicast VRF using IPv6 infrastructure addresses
Figure 1: BGP MVPN Evolution to IPv6 Infrastructure
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During the evolution process, IPv4 and IPv6 parallel BGP sessions are
established between Provider Edge routers and route reflectors(RR).
If the BGP MVPN routes are sent to all IPv4 and IPv6 BGP peers
without any control, the number of the PATHs of these routes will be
doubled with each reflection while BGP ADD-PATH [RFC7911] procedure
is enabled on route reflectors.
3.2. Modification of C-Multicast Route NLRI
The solution to distinguish the C-multicast routes sent to different
root PEs is related to the way to distinguish UMH routes for a
specific multicast source (C-S) sent from different root PEs, which
the later is not a problem of IPv6 infrastructure specific. In
[RFC6514], it recommended that the RDs of root PEs of a same MVPN
were configured distinctly to perform selective forwarding selection,
which was broken by GTM procedures defined in [RFC7716] because the
UMH routes sent from different root PEs through BGP SAFI 1 or SAFI 2
lack RD informations. There are also some MVPN deployment cases that
the RDs of root PEs may be configuered with a same value for
provisioning reasons. According to above description, whether the
RDs of PEs of a MVPN are same or not are two different deployment
cases. This document addresses the C-multicast routes distinguishing
issue for both cases. How to distinguish UMH routes in the cases of
root PEs with same RD is out of the scope of this document, because
it is not IPv6 infrastructure specific.
To support non-segmented inter-AS tunnels in IPv6 infrastructure
network, the C-multicast route NLRI is redefined as follow:
+-----------------------------------+
| RD (8 octets) |
+-----------------------------------+
| Root Distinguisher (4 octets) |
+-----------------------------------+
| Multicast Source Length (1 octet) |
+-----------------------------------+
| Multicast Source (variable) |
+-----------------------------------+
| Multicast Group Length (1 octet) |
+-----------------------------------+
| Multicast Group (variable) |
+-----------------------------------+
In the above figure, the Root Distinguisher field replaces the Source
As field defined in [RFC6514]. When constructing a C-multicast
route, leaf PE follows the following specification:
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1. For the cases of IPv4 infrastructure or Intra-AS P-tunnel
establishment in IPv6 infrastructure, the Root Distinguisher
field MUST be treated as Source AS field and section 11.1.3 of
[RFC6514] MUST be fully followed.
2. For non-segmented Inter-AS P-tunnel establishment in IPv6
infrastructure scenarios, if the RDs of ingress PEs are distinct
(which can be detected from UMH routes), the Root Distinguisher
field MUST be filled with the number of ingress AS.
3. For non-segmented Inter-AS P-tunnel establishment in IPv6
infrastructure scenarios, if the RDs of ingress PEs are same, a
4-octet distinct value MUST be assigned by leaf PE for each root
PE. For example, each leaf PE uses a same well-known /
configured hash algorithm to transform the IPv6 root IP to
4-octet distinct value for each ingress PE, or a provisioning
method is used to globally assign different 4-octet IDs for each
ingress PE. The Root Distinguisher field in C-multicast NLRI is
filled with this value and a distinct C-multicast route will be
sent to individual upstream root PE.
The solution to control the propagation of C-multicast route between
different ASes is to use the IPv6 address included in IPv6 VRF Route
Import Extended Community insteading of Source AS field of
C-multicast NLRI while locating Intra-AS AD route of the
corresponding root PE the C-multicast sent to on ASBRs. This
document recommends that the Local Administrator field of IPv6 VRF
Route Import Extended Community is set to a non-zero value by root
PEs even in GTM scenarios, of which the value is local assigned
distinctly by root PE for both each MVPN and GTM instance.
Accordingly, the IPv6 root address of a C-multicast route can be
extracted from the only IPv6 VRF Route Import Extended Community
carring a non-zero Local Administrator field.
When receiving a C-multicast route from E-BGP neighbors, the ASBR
checks whether an IPv6 VRF Route Import Extended Community with a
non-zero Local Administrator field is included in this route and
takes following actions:
1. If the IPv6 VRF Route Import Extended Community does not exist in
the C-multicast route, the ASBR will treat the Root Distinguisher
field as Source AS field and follows the description in section
11.2 of [RFC6514].
2. If the IPv6 VRF Route Import Extended Community does exist in the
C-multicast route, the ASBR will match the IPv6 address carried
in this extended community and the RD in C-multicast route NLRI
against the Originating Router's IP Address and the RD of the
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Intra-AS I-PMSI A-D routes. If the corresponding Intra-AS I-PMSI
A-D route exists, the ASBR will propagate the C-multicast route
in its local AS.
3.3. Route Reflection Control
To reduce BGP MVPN routes in Parallel IPv4 and IPv6 BGP sessions
scenario, the following actions should be taken by sender PEs:
1. For Intra-AS I-PMSI A-D Route, S-PMSI A-D Route and Leaf A-D
Route, if the Originating Router's IP Address field in the route
is filled with an IPv6 address, it will be sent to the IPv6 BGP
neighbors; otherwise, it will be sent to the IPv4 BGP neighbors.
2. For Inter-AS I-PMSI A-D Route and Source Active A-D Route, it is
sent to both IPv6 BGP neighbors and IPv4 BGP neighbors.
3. For C-multicast route, if the IPv6 VRF Route Import Extended
Community exists in the route, it will be sent to the IPv6 BGP
neighbors; otherwise, it will be sent to the IPv4 BGP neighbors.
In the route reflectors, the part of routes which are received from
IPv6 BGP neighbors will be reflected to other IPv6 BGP neighbors and
the other part of routes which are received from IPv4 BGP neighbors
will be reflected to other IPv4 BGP neighbors.
4. Security Considerations
This document introduces no new security considerations beyond those
already specified in [RFC6514] and [RFC6515].
5. IANA Considerations
This document contains no actions for IANA.
6. Acknowledgements
Your name here
7. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
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[RFC6514] Aggarwal, R., Rosen, E., Morin, T., and Y. Rekhter, "BGP
Encodings and Procedures for Multicast in MPLS/BGP IP
VPNs", RFC 6514, DOI 10.17487/RFC6514, February 2012,
<https://www.rfc-editor.org/info/rfc6514>.
[RFC6515] Aggarwal, R. and E. Rosen, "IPv4 and IPv6 Infrastructure
Addresses in BGP Updates for Multicast VPN", RFC 6515,
DOI 10.17487/RFC6515, February 2012,
<https://www.rfc-editor.org/info/rfc6515>.
[RFC7716] Zhang, J., Giuliano, L., Rosen, E., Ed., Subramanian, K.,
and D. Pacella, "Global Table Multicast with BGP Multicast
VPN (BGP-MVPN) Procedures", RFC 7716,
DOI 10.17487/RFC7716, December 2015,
<https://www.rfc-editor.org/info/rfc7716>.
[RFC7911] Walton, D., Retana, A., Chen, E., and J. Scudder,
"Advertisement of Multiple Paths in BGP", RFC 7911,
DOI 10.17487/RFC7911, July 2016,
<https://www.rfc-editor.org/info/rfc7911>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
Authors' Addresses
Fanghong Duan
Huawei Technologies
Email: duanfanghong@huawei.com
Jingrong Xie
Huawei Technologies
Email: xiejingrong@huawei.com
Siyu Chen
Huawei Technologies
Email: chensiyu27@huawei.com
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