Internet DRAFT - draft-agrawal-bess-bgp-srv6-mpls-interworking
draft-agrawal-bess-bgp-srv6-mpls-interworking
BESS WorkGroup S. Agrawal, Ed.
Internet-Draft D. Rao
Intended status: Standards Track Z. Ali
Expires: 27 April 2023 C. Filsfils
Cisco Systems
D. Voyer
Bell Canada
G. Dawra
LinkedIn
Z. Li
Huawei Technologies
24 October 2022
BGP extensions for SRv6 and MPLS interworking
draft-agrawal-bess-bgp-srv6-mpls-interworking-00
Abstract
This document define the BGP protocol extensions required to provide
interworking between SRv6 and SR-MPLS/MPLS for SRv6 deployment.
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 27 April 2023.
Copyright Notice
Copyright (c) 2022 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
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and restrictions with respect to this document. Code Components
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provided without warranty as described in the Revised BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3
2. SRv6 SID advertisement in BGP update for PE address . . . . . 3
2.1. SRv6 tunnel for label route TLV . . . . . . . . . . . . . 3
2.2. SRv6 SID bound to prefix in NLRI . . . . . . . . . . . . 4
2.2.1. Address in NLRI is only bound to SRv6 SID . . . . . . 4
2.2.2. MPLS label and SRv6 SID bound to prefix in NLRI . . . 5
2.3. Propogation of SRv6 SID in BGP update for PE address . . 6
3. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
3.1. BGP Prefix-SID TLV Types registry . . . . . . . . . . . . 7
4. Security Considerations . . . . . . . . . . . . . . . . . . . 7
5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 7
6. References . . . . . . . . . . . . . . . . . . . . . . . . . 7
6.1. Normative References . . . . . . . . . . . . . . . . . . 7
6.2. Informative References . . . . . . . . . . . . . . . . . 9
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9
1. Introduction
The deployment of SRv6 into existing networks require SRv6 to
interwork with SR-MPLS/MPLS. Draft
[I-D.agrawal-spring-srv6-mpls-interworking] describes SRv6 and MPLS
interworking architecture in multi domain network where each domain
run SRv6 or MPLS data plane independently. Specifically section
7.1.2 of draft details BGP inter-domain routing procedures to
advertise PE locators or PE loopbacks address across such network
with next hop self at domain border routers. When performing next
hop self on domain border router and further propagation, draft
proposes to allocate and signal additional upstream data plane
specific information. This document extract the BGP protocol
extensions proposed in [I-D.agrawal-spring-srv6-mpls-interworking] to
signal SRv6 SID with BGP SAFI 4 or SAFI 1 advertisements. This is
done to independently state BGP protocol extensions and future
applicability of them for other use cases.
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1.1. 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.
2. SRv6 SID advertisement in BGP update for PE address
[RFC9252] extended BGP Prefix SID Attribute (PFA) to signal SRv6 SID
in "SRv6 L3 Service" and "SRv6 L2 Service" TLVs for layer 3 and layer
2 services. This document introduces new "SRv6 tunnel for label
route" TLV for safi 4 [RFC8277] and extends usage of "SRv6 L3
Service" TLV for SAFI 4.
2.1. SRv6 tunnel for label route TLV
[RFC8669] introduced Prefix-SID attribute with TLV type 1 for label
index and TLV type 3 for Originator SRGB for AFI=1/2 and SAFI 4 (BGP
LU). This document introduces a new TLV called "SRv6 tunnel for
label route" of the BGP Prefix-SID Attribute to signal SRv6 SIDs
along with MPLS label bound to prefix in NLRI. Behavior that may be
encoded but not limited to is End.DTM. "SRv6 tunnel for label route"
TLV signals "AND" semantics i.e. push label signaled in NLRI and
perform H.Encaps.M with DA as SRv6 SID signaled in TLV. This
document limits the usage of this new TLV to AFI=1/2 SAFI 4. The
usage of this TLV for other AFI/SAFI is out of scope of this
document.
"SRv6 tunnel for label route" TLV is encoded exactly like SRv6
Service TLVs in Prefix-SID Attribute [RFC9252] with following
modification:
* TLV Type (1 octet): This field is assigned values from the IANA
registry "BGP Prefix-SID TLV Types". It is set to 7 for "SRv6
tunnel for label route" TLV.
* No transposition scheme is allowed i.e. transposition length MUST
be 0 in SRv6 SID Structure Sub-Sub-TLV.
Please refer to section 7.1.2.2.1 of
[I-D.agrawal-spring-srv6-mpls-interworking] for usage of "SRv6 tunnel
for label route" TLV and overall procedures along with control and
forwarding state
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2.2. SRv6 SID bound to prefix in NLRI
Bound the SRv6 SID of DPM behavior to PE loopback address carried in
NLRI of BGP update of SAFI 1 or SAFI 4. Receiving node perform
H.Encaps, where destination of IPv6 header is set to SRv6 SID for
traffic destined to address in NLRI.
Please refer to section 7.1.2.2.2 of
[I-D.agrawal-spring-srv6-mpls-interworking] for overall procedures
when SRv6 SID is bound to PE address.
This document proposes below 2 options to advertise SRv6 SID bound to
prefix in NLRI
2.2.1. Address in NLRI is only bound to SRv6 SID
Address in NLRI is only bound to SRv6 SID by advertising node. In
this case, SAFI 4 cannot be used to advertise PE loopback across SRv6
domain as label is required in NLRI [RFC8277]. Therefore SRv6 SID
with End.DPM behavior bound to prefix in NLRI is advertised in SAFI 1
as per section 5.3 and 5.4 of [RFC9252]. To distinguish from global
internet routes on receiver, local policy matching PE loopback
addresses or BGP community/extended community attached to such
advertisement may be used. Such policy on receiver helps to allocate
MPLS label and advertise route further upstream in SAFI 4 in MPLS
domain for PE addresses with next hop self. Figure 1 shows BGP
update example through SRv6 domain.
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+-----+ +-----+ RD:V/v via 10 +-----+
.......|S-RR1|<...............|S-RR2|<.................|S-RR3| <..
: +-----+ +-----+ +-----+ :
: :
: :
+--:-------------------+----------------------+---------------------:-+
| : | | : |
| : | | : |
| : SAFI 4 | SAFI 1 | SAFI 4 : |
| : <-E10,Label via 4 | <-E10 via 7 | <-E10,0x3 via E10 : |
| : | SRv6 SID=B7:E10:: | : |
|----+ +---+ +---+ +----|
| E1 | | 4 | | 7 | |E10 |
|----+ +---+ +---+ +----|
| | | |
| | | |
| | | |
| | | |
| MPLS | SRv6 | MPLS |
+----------------------+----------------------+-----------------------+
iPE iBR eBR ePE
<----------LI---------><----------C----------><-----------LE---------->
Figure 1: SRv6 SID bound to NLRI of SAFI 1
2.2.2. MPLS label and SRv6 SID bound to prefix in NLRI
Advertise MPLS label and SRv6 SID bound to prefix in NLRI. RFC 8669
introduced Prefix-SID attribute with TLV type 1 for label index and
TLV type 3 for Originator SRGB for AFI=1/2 and SAFI 4 (BGP LU). This
document extends the BGP Prefix-SID attribute [RFC8669] to carry
"SRv6 L3 Service TLV" defined in [RFC9252] with AFI=1/2 and SAFI 4.
TLV is encoded exactly like SRv6 Service TLVs in Prefix-SID Attribute
without transposition. Such an update can be processed by both
legacy MPLS ABR and SRv6 capable ABR and use relevant encapsulation.
For example, in Figure 2 node 4 being SRv6 capable chooses SRv6
encapsulation and node 44 being legacy continue MPLS encapsulation.
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+-----+ +-----+ RD:V/v via 10 +-----+
.......|S-RR1|<...............|S-RR2|<.................|S-RR3| <..
: +-----+ +-----+ +-----+ :
: :
: :
+--:-------------------+----------------------+---------------------:-+
| : | | : |
| : +---+ | : |
| : | 4 | | : |
| : SAFI 4 +---+ SAFI 4 | SAFI 4 : |
| : <-E10,Label via 4 | <-E10,Label via 7 | <-E10,0x3 via E10 : |
|----+ | SRv6 SID=B7:E10:: +---+ +----|
| E1 | | | 7 | |E10 |
|----+ +---+ +---+ +----|
| |44 | | |
| +---+ | |
| | | |
| | | |
| MPLS | SRv6/MPLS | MPLS |
+----------------------+----------------------+-----------------------+
iPE iBR eBR ePE
<----------LI---------><----------C----------><-----------LE---------->
Figure 2: SRv6 SID bound to NLRI of SAFI 4
2.3. Propogation of SRv6 SID in BGP update for PE address
A BGP speaker receiving updates with PE address in NLRI and Prefix-
SID Attribute with "SRv6 tunnel for label route" TLV or "SRv6 L3
Service" TLV observe the following rules when advertising the route
to other peers:
* If the nexthop is unchanged, the TLVs, including any unrecognized
Types of Sub-TLV and Sub-Sub-TLV, SHOULD be propagated further.
In addition, all Reserved fields in the TLV or Sub-TLV or Sub-Sub-
TLV MUST be propagated unchanged.
* If the nexthop is modified, the TLV and associated sub-TLVs/Sub-
Sub-TLVs SHOULD be updated based on local policy. For example, if
upstream is MPLS domain, then TLVs carrying SRv6 SID should be
removed and local MPLS label bound to address in NLRI is sent in
SAFI 4.
3. IANA Considerations
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3.1. BGP Prefix-SID TLV Types registry
This document introduce a new TLV Type of the BGP Prefix-SID
attribute. IANA is requested to assign Type value in the registry
"BGP Prefix-SID TLV Types" as follows
Value Type Reference
----------------------------------------------------------
TBD "SRv6 tunnel for label route" TLV <this document>
4. Security Considerations
5. Acknowledgements
The authors would like to acknowledge Stephane Litkowski and Ketan
Talaulikar for review and comments.
6. References
6.1. Normative References
[I-D.agrawal-spring-srv6-mpls-interworking]
Agrawal, S., ALI, Z., Filsfils, C., Voyer, D., and H.
Technologies, "SRv6 and MPLS interworking", Work in
Progress, Internet-Draft, draft-agrawal-spring-srv6-mpls-
interworking-09, 8 September 2022,
<https://www.ietf.org/archive/id/draft-agrawal-spring-
srv6-mpls-interworking-09.txt>.
[I-D.ietf-spring-segment-routing-policy]
Filsfils, C., Talaulikar, K., Voyer, D., Bogdanov, A., and
P. Mattes, "Segment Routing Policy Architecture", Work in
Progress, Internet-Draft, draft-ietf-spring-segment-
routing-policy-22, 22 March 2022,
<https://www.ietf.org/archive/id/draft-ietf-spring-
segment-routing-policy-22.txt>.
[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>.
[RFC3032] Rosen, E., Tappan, D., Fedorkow, G., Rekhter, Y.,
Farinacci, D., Li, T., and A. Conta, "MPLS Label Stack
Encoding", RFC 3032, DOI 10.17487/RFC3032, January 2001,
<https://www.rfc-editor.org/info/rfc3032>.
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[RFC4023] Worster, T., Rekhter, Y., and E. Rosen, Ed.,
"Encapsulating MPLS in IP or Generic Routing Encapsulation
(GRE)", RFC 4023, DOI 10.17487/RFC4023, March 2005,
<https://www.rfc-editor.org/info/rfc4023>.
[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>.
[RFC7432] Sajassi, A., Ed., Aggarwal, R., Bitar, N., Isaac, A.,
Uttaro, J., Drake, J., and W. Henderickx, "BGP MPLS-Based
Ethernet VPN", RFC 7432, DOI 10.17487/RFC7432, February
2015, <https://www.rfc-editor.org/info/rfc7432>.
[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>.
[RFC8277] Rosen, E., "Using BGP to Bind MPLS Labels to Address
Prefixes", RFC 8277, DOI 10.17487/RFC8277, October 2017,
<https://www.rfc-editor.org/info/rfc8277>.
[RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L.,
Decraene, B., Litkowski, S., and R. Shakir, "Segment
Routing Architecture", RFC 8402, DOI 10.17487/RFC8402,
July 2018, <https://www.rfc-editor.org/info/rfc8402>.
[RFC8664] Sivabalan, S., Filsfils, C., Tantsura, J., Henderickx, W.,
and J. Hardwick, "Path Computation Element Communication
Protocol (PCEP) Extensions for Segment Routing", RFC 8664,
DOI 10.17487/RFC8664, December 2019,
<https://www.rfc-editor.org/info/rfc8664>.
[RFC8669] Previdi, S., Filsfils, C., Lindem, A., Ed., Sreekantiah,
A., and H. Gredler, "Segment Routing Prefix Segment
Identifier Extensions for BGP", RFC 8669,
DOI 10.17487/RFC8669, December 2019,
<https://www.rfc-editor.org/info/rfc8669>.
[RFC8986] Filsfils, C., Ed., Camarillo, P., Ed., Leddy, J., Voyer,
D., Matsushima, S., and Z. Li, "Segment Routing over IPv6
(SRv6) Network Programming", RFC 8986,
DOI 10.17487/RFC8986, February 2021,
<https://www.rfc-editor.org/info/rfc8986>.
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[RFC9252] Dawra, G., Ed., Talaulikar, K., Ed., Raszuk, R., Decraene,
B., Zhuang, S., and J. Rabadan, "BGP Overlay Services
Based on Segment Routing over IPv6 (SRv6)", RFC 9252,
DOI 10.17487/RFC9252, July 2022,
<https://www.rfc-editor.org/info/rfc9252>.
6.2. Informative References
[I-D.ietf-mpls-seamless-mpls]
Leymann, N., Decraene, B., Filsfils, C., Konstantynowicz,
M., and D. Steinberg, "Seamless MPLS Architecture", Work
in Progress, Internet-Draft, draft-ietf-mpls-seamless-
mpls-07, 28 June 2014, <https://www.ietf.org/archive/id/
draft-ietf-mpls-seamless-mpls-07.txt>.
Authors' Addresses
Swadesh Agrawal (editor)
Cisco Systems
Email: swaagraw@cisco.com
Dhananjaya Rao
Cisco Systems
Email: dhrao@cisco.com
Zafar ALI
Cisco Systems
Email: zali@cisco.com
Clarence Filsfils
Cisco Systems
Email: cfilsfil@cisco.com
Daniel Voyer
Bell Canada
Canada
Email: daniel.voyer@bell.ca
Gaurav dawra
LinkedIn
United States of America
Email: gdawra.ietf@gmail.com
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Zhenbin Li
Huawei Technologies
China
Email: lizhenbin@huawei.com
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