Internet DRAFT - draft-duan-bess-simplified-mvpn-for-bier-and-ir
draft-duan-bess-simplified-mvpn-for-bier-and-ir
Network Working Group F. Duan
Internet-Draft S. Chen
Intended status: Standards Track Huawei Technologies
Expires: 10 September 2023 9 March 2023
Simplified MVPN for BIER and IR
draft-duan-bess-simplified-mvpn-for-bier-and-ir-00
Abstract
Per RFC6513 and RFC6514, seven MCAST-VPN NLRIs and relevant
procedures are defined to build multicast forwarding tree over the
service provider backbone. RFC8556 introduces that MVPN can use BIER
as PMSI tunnel to perform optimal multicast forwarding. However, the
complicated NLRI exchange and the switching from I-PMSI to S-PMSI
tunnel is not necessary for BIER and IR tunnel. The architectural
advantages of BIER and IR cannot be fully utilized. Therefore, a new
simplified MVPN for BIER and IR is proposed to substitute current
NLRIs exchange and procedures. This document would like to discuss
the value of the MVPN simplification and provide suggestive solution.
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
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 10 September 2023.
Duan & Chen Expires 10 September 2023 [Page 1]
Internet-Draft Simplified MVPN for BIER and IR March 2023
Copyright Notice
Copyright (c) 2023 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 carefully, as they describe your rights
and restrictions with respect to this document. Code Components
extracted from this document must include Revised BSD License text as
described in Section 4.e of the Trust Legal Provisions and are
provided without warranty as described in the Revised BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Specification . . . . . . . . . . . . . . . . . . . . . . . . 4
3.1. Simplification of Type 1 to Type 4 NLRI . . . . . . . . . 4
3.2. Simplification of Type 6 to Type 7 NLRI . . . . . . . . . 5
4. Back compatibility . . . . . . . . . . . . . . . . . . . . . 5
5. Security Considerations . . . . . . . . . . . . . . . . . . . 5
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 6
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 6
8.1. Normative References . . . . . . . . . . . . . . . . . . 6
8.2. Informative References . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6
1. Introduction
In [RFC4364], IP Virtual Private Networks (VPNs) are proposed to
forward unicast traffic from one VPN site to another. Afterwards,
[RFC6037] firstly combined VPN with IP Multicast and multicast
forwarding tree can be built over the provider backbone. PIM was the
only protocol to build the PMSI tunnels. [RFC6513] and [RFC6514]
then improved the MVPN procedure such as it introduced more flexible
tunnel type such as P2MP and IR. Besides, seven MCAST-VPN NLRIs are
defined to advertise the information of PEs, tunnels and join/prune.
Both MVPN solutions started with instantiate inclusive PMSI as the
first step to build the multicast distribution trees over the
provider network. In order to optimize the bandwidth utilization of
the provider backbone network, Type 3 NLRI is designed so that
selective multicast can be performed when the traffic of (C-S,C-G)
exceeds the preset threshold. The switching from I-PMSI to S-PMSI is
an inevitable action for selective multicast when the tunnel type is
mLDP or RSVP-TE. The switching results in the complicated NLRI
Duan & Chen Expires 10 September 2023 [Page 2]
Internet-Draft Simplified MVPN for BIER and IR March 2023
exchanging procedures. [RFC8556] introduces that MVPN can use BIER
to conduct optimal multicast forwarding. The complicated NLRI
exchanging procedures are still maintained while those are
unnecessary for BIER and Ingress Replication Tunnel. There are
several problems in current MVPN procedures:
a. Even though per-flow multicast state is not maintained in the P
routers, ingress root PE still follows the traditional process of
building multicast tunnel. Root PE also needs to check whether
the amount of multicast flow exceeds the preset threshold at any
time so that it can initiate the switching from I-PMSI to S-PMSI.
The exchange of control-plane and data-plane are still very
complicated.
b. There are three types of NLRIs involved in the process of
customer's routes advertisement. Besides, four types of NLRIs
are leveraged to collect tunnel informations. The exchange of
NLRIs between each router is complicated.
The architectural advantages of BIER and IR are that they can
intrinsically support explicit tracking at the ingress PE. Each leaf
PE is unique from the perspective of ingress PE. S-PMSI tunnel can
be constructed directly at first. The switching from I-PMSI to
S-PMSI tunnel can be omitted. On the other hand, segment routing is
widely discussed and implemented nowadays and it is regarded as a
simplification of MPLS. SR-MPLS, SR-BIER and SR-IR are
simplification of existing tunnel types in a sense. With SR, current
MVPN architecture and NLRI exchanges seem to be too heavy. Under
these circumstances, a light-weight architecture of MVPN needs to be
considered. In that way, the feature of explicit tracking can also
be fully utilized.
One possible method is proposed in this document to simplify the MVPN
procedure for BIER and IR. There would be no inclusive PMSI tunnel.
Two new multicast routes and procedures are proposed to substitute
the existing seven NLRIs.
2. Terminology
The terminology used in this document is the terminology defined
in[RFC6513], [RFC6514] and [RFC8556].
For convenience of description, the abbreviations used in this
document is listed below.
NLRI: Network Layer Reachability Information
UMH: Upstream Multicast Hop
Duan & Chen Expires 10 September 2023 [Page 3]
Internet-Draft Simplified MVPN for BIER and IR March 2023
PMSI: P-Multicast Service Interface
VPN: Virtual Private Network
MVPN: Multicast VPN
RD: Route Distinguisher
IR: Ingress Replication
3. Specification
3.1. Simplification of Type 1 to Type 4 NLRI
Type 1 to 4 NLRI may be replaced by a new eligible UMH Route. The
eligible UMH route was initially introduced in [RFC6513]. It
contains Source AS Extended Community and VRF Route Import Extended
Community. In this document, MS-ID and underlay BIER attribute are
added into the eligible UMH route so that type 1 to 4 NLRIs are no
longer needed. When the leaf PE receives the eligible UMH routes, it
will import the unicast route into its local instance.
Simultaneously, the MS-ID will be used to generate the correspondence
between the MS-id and local instance. When the leaf PE receives the
join or prune messages, it will find the multicast source or RP in
the unicast routing-table of corresponding instance. The underlay
BIER attribute of the unicast route will be used. Leaf PE will check
whether the sub-domain-id inside the BIER attribute is same as its
sub-domain-id. If the two IDs are same, leaf PE will create a BGP
multicast route and advertise it to root PE.
+------------------------------------------------+
| MS-ID (4 or 16 octets) |
+------------------------------------------------+
| Sub-domain ID (2 octets ) |
+------------------------------------------------+
| BFR-ID (2 octets ) |
+------------------------------------------------+
Figure 1: New MVPN Eligible UMH Route
Duan & Chen Expires 10 September 2023 [Page 4]
Internet-Draft Simplified MVPN for BIER and IR March 2023
3.2. Simplification of Type 6 to Type 7 NLRI
The above-mentioned BGP multicast route is proposed to replace Type 6
to 7 NLRI. Just like leaf A-D route, it contains RD, originator IP,
source address and group address. Additionally, it includes one-
octet field called Flag. Flag is used to distinguish (C-*,C-G) Join,
(C-S,C-G) Join and (C-S,C-G,rpt) Prune. The route also includes BIER
sub-domain-id and BFR-id of leaf PE. The conventional Join and Prune
of c-multicast route are substituted by the update and withdraw of
BGP multicast route. Moreover, Source AS Extended Community and VRF
Route Import Extended Community are also carried by the BGP multicast
route.
+------------------------------------------------+
| RD (8 octets) |
+------------------------------------------------+
| Source Address (4 or 16 octets, 0 to 32 / 128)|
+------------------------------------------------+
| Group Address (4 or 16 octets, 0 to 32 / 128) |
+------------------------------------------------+
| Flag (1 octet) |
+------------------------------------------------+
| Originating Router's IP Addr (4 / 16 octets) |
+------------------------------------------------+
| Sub-domain ID (2 octets ) |
+------------------------------------------------+
| BFR-ID (2 octets ) |
+------------------------------------------------+
Figure 2: New BGP Multicast Route
4. Back compatibility
Back compatibility is a significant issue and will be discussed in
the future.
5. Security Considerations
//TODO
6. IANA Considerations
//TODO
Duan & Chen Expires 10 September 2023 [Page 5]
Internet-Draft Simplified MVPN for BIER and IR March 2023
7. Acknowledgements
//TODO
8. References
8.1. 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>.
[RFC4364] Rosen, E. and Y. Rekhter, "BGP/MPLS IP Virtual Private
Networks (VPNs)", RFC 4364, DOI 10.17487/RFC4364, February
2006, <https://www.rfc-editor.org/info/rfc4364>.
[RFC6513] Rosen, E., Ed. and R. Aggarwal, Ed., "Multicast in MPLS/
BGP IP VPNs", RFC 6513, DOI 10.17487/RFC6513, February
2012, <https://www.rfc-editor.org/info/rfc6513>.
[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>.
[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>.
[RFC8556] Rosen, E., Ed., Sivakumar, M., Przygienda, T., Aldrin, S.,
and A. Dolganow, "Multicast VPN Using Bit Index Explicit
Replication (BIER)", RFC 8556, DOI 10.17487/RFC8556, April
2019, <https://www.rfc-editor.org/info/rfc8556>.
8.2. Informative References
[RFC6037] Rosen, E., Ed., Cai, Y., Ed., and IJ. Wijnands, "Cisco
Systems' Solution for Multicast in BGP/MPLS IP VPNs",
RFC 6037, DOI 10.17487/RFC6037, October 2010,
<https://www.rfc-editor.org/info/rfc6037>.
Authors' Addresses
Fanghong Duan
Huawei Technologies
Email: duanfanghong@huawei.com
Duan & Chen Expires 10 September 2023 [Page 6]
Internet-Draft Simplified MVPN for BIER and IR March 2023
Siyu Chen
Huawei Technologies
Email: chensiyu27@huawei.com
Duan & Chen Expires 10 September 2023 [Page 7]
