Network Working Group J. Xie
Internet-Draft X. Geng
Intended status: Standards Track Huawei Technologies
Expires: 28 April 2022 Y. Liu
China Mobile
25 October 2021
Source Segment for Multicast Source Routing over IPv6
draft-xl-msr6-source-segment-00
Abstract
This document defines the general concept of source segment which is
used as the IPv6 source address in an IPv6 packet. Source segment
for multicast service is introduced in this document.
Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119]
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 28 April 2022.
Copyright Notice
Copyright (c) 2021 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.
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Please review these documents carefully, as they describe your rights
and restrictions with respect to this document. Code Components
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminologies . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Source Segment Definition . . . . . . . . . . . . . . . . . . 3
4. SID Format . . . . . . . . . . . . . . . . . . . . . . . . . 4
5. Source Segment for MVPN . . . . . . . . . . . . . . . . . . . 4
5.1. Behaviors . . . . . . . . . . . . . . . . . . . . . . . . 4
5.2. SRC.DT4 . . . . . . . . . . . . . . . . . . . . . . . . . 5
5.3. SRC.DT6 . . . . . . . . . . . . . . . . . . . . . . . . . 5
5.4. SRC.DT46 . . . . . . . . . . . . . . . . . . . . . . . . 5
5.5. Src.DT2 . . . . . . . . . . . . . . . . . . . . . . . . . 6
6. Use Case . . . . . . . . . . . . . . . . . . . . . . . . . . 6
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
8. Security Considerations . . . . . . . . . . . . . . . . . . . 7
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 7
9.1. Normative References . . . . . . . . . . . . . . . . . . 7
9.2. Informative References . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10
1. Introduction
Segment Routing ([RFC8402]) leverages the mechanism of source
routing. An ingress node steers a packet through an ordered list of
instructions, called "segments". Each one of these instructions
represents a function to be implemented at a specific location in the
network. A function is locally defined on the node where it is
executed. Network Programming combines Segment Routing functions to
achieve a networking objective that goes beyond mere packet routing.
[RFC8986] defines the SRv6 Network Programming concept and specifies
the main Segment Routing behaviors and network programming functions.
Previous segments defined in SRv6 can be used as the destination
address of an IPv6 packet. This document introduces the new
segments, source segments, which can be used as the IPv6 source
address of an IPv6 packet. This document defines the general concept
of source segment and the source segment used for multicast service.
Protocol extensions on the control plane are not in the scope of this
document.
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This document defines the general concept of source segment and the
source segment used for multicast service. Protocol extensions on
the control plane are not in the scope of this document.
2. Terminologies
The following new terms are used throughout this document:
MSR6: Multicast Source Routing over IPv6;
MSR6 Domain: a set of nodes participating in the multicast source
routing;
3. Source Segment Definition
Source segment is different from the existing SID defined in RFC8402
from the following aspects:
* Source segment is unchanged along the SRv6 path
* Source segment is distributed by the ingress node but indicates
functions in other nodes along the path, e.g., egress node.
Forwarding table should be maintained in the nodes where the
instruction takes place.
* When the source segment is encapsulated in an SRv6 packet, it is
activated by other instructions in the data plane because source
address is not parsed in existing forwarding process of a unicast
packet
Using source segment for SRv6 Network Programming have several
benefits including:
* Enhance network programming capability for more SRv6 functions and
extend the programming space in IPv6 header;
* Provide sematic for source address with similar IPv6 address
allocation and management method as SRv6;
* Facilitates security management inside the limited domain;
Source segment should be avoided to process hop by hop. Per-hop
process of source segment which will degrade forwarding performance
and bring compatibility issues.
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4. SID Format
Source segment leverages the format of SID defined in SRv6 network
programming.
Source segment consists of LOC:FUNCT:ARG, where a locator (LOC) is
encoded in the L most significant bits of the SID, followed by F bits
of function (FUNCT) and A bits of arguments (ARG).
A locator may be represented as B:N where B is the SRv6 SID block
(IPv6 prefix allocated for SRv6 SIDs by the operator) and N is the
identifier of the ingress node .
The FUNCT is an opaque identification of the behavior bound to the
SID. The behavior could be executed in other nodes except ingress
node.
The behavior indicated by FUNCT may require additional information
for its processing. This information may be encoded in the ARG bits
of the SID.
5. Source Segment for MVPN
In the multicast service, packet is replicated along the tree towards
a set of leaf nodes. MVPN routing and the corresponding information
could be encapsulated in the source segment carried in the IPv6
source address. Source Segment for MVPN is distributed by the
multicast source node and the function is executed by the multicast
leaf nodes.As described in section 3, Source Segment for MVPN is not
changed when the packet is replicated and forwarded along the P2MP
path.
This section defines the source segment for MVPN.
5.1. Behaviors
The following is a set of behaviors that can be associated with a
source segment for MVPN.
+------------+------------------------------------------------------+
| Src.DT4 |Source address for decapsulation and IPv4 table lookup|
|------------|------------------------------------------------------+
| Src.DT6 |Source address for decapsulation and IPv6 table lookup|
|------------|------------------------------------------------------+
| Src.DT46 |Source address for decapsulation and IP table lookup |
|------------|------------------------------------------------------+
| Src.DT2 |Source address for decapsulation and L2 table lookup |
|------------|------------------------------------------------------+
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5.2. SRC.DT4
The "Source address for decapsulation and IPv4 table lookup" behavior
("Src.DT4" for short) is used in MVPNv4 use case where an MFIB lookup
in a specific VRF table T at the egress node is required. The
Src.DT4 SID is an SID associated with an IPv4 MFIB table T on the
egress PE, either through a control-plane message advertised by the
ingress PE, or through a local configuration on the egress PE. When
an IPv6 encapsulated packet with IPv6 source address being S is
received on an egress PE, and S is associated with an Src.DT4 SID on
the egress PE, the egress PE does the following behavior:
S01. If (Upper-Layer header type == 4(IPv4) ) {
S02. Remove the outer IPv6 header with all its extension headers
S03. Set the packet's associated MFIB table to T
S04. Submit the packet to the egress IPv4 MFIB lookup for
transmission to the new multicast downstreams
S05. } Else {
S06. Drop the packet;
S07. }
5.3. SRC.DT6
SRC.DT6 behavior could be used in MVPNv6 use case where a MFIB lookup
in a specific VRF table at the egress node is required.
S01. If (Upper-Layer header type == 41(IPv6) ) {
S02. Remove the outer IPv6 header with all its extension headers
S03. Set the packet's associated IPv6 MFIB table to T
S04. Submit the packet to the egress IPv6 MFIB lookup for
transmission to the new multicast downstreams
S05. } Else {
S06. Drop the packet;
S07. }
5.4. SRC.DT46
SRC.DT46 behavior could be used in MVPN use case where a MFIB lookup
in a specific VRF table at the egress node is required.
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S01. If (Upper-Layer header type == 4(IPv4) ) {
S02. Remove the outer IPv6 header with all its extension headers
S03. Set the packet's associated MFIB table to T
S04. Submit the packet to the egress IPv4 MFIB lookup for
transmission to the new destination
S05. } Else if (Upper-Layer header type == 41(IPv6) ) {
S06. Remove the outer IPv6 header with all its extension headers
S07. Set the packet's associated MFIB table to T
S08. Submit the packet to the egress IPv6 MFIB lookup for
transmission to the new destination
S09. } Else {
S10. Drop the packet;
S11. }
5.5. Src.DT2
SRC.DT2 behavior could be used in MVPN use case where a L2 table
lookup in a specific Layer-2 Multicast forwarding table at the egress
node is required.
S01. If (Upper-Layer header type == 143(Ethernet) ) {
S02. Remove the outer IPv6 header with all its extension headers
S03. Set the packet's associated Layer-2 Multicast forwarding table to T
S04. Submit the packet to the egress Layer-2 Multicast forwarding table
lookup for transmission to the new multicast downstreams
S05. } Else {
S06. Send an ICMP Parameter Problem to the Source Address
with Code 4 (SR Upper-layer Header Error)
and Pointer set to the offset of the Upper-Layer header,
interrupt packet processing, and discard the packet
S07. }
6. Use Case
The source segment could be applied in the following case:
1. MSR6: The MSR6 MVPN uses the source segment in the IPv6 source
address for identifying a VRF in IPv6 multicast source routing.
2. Tree SID over SRv6: MVPN service can use Tree SID over SRv6
[I-D.ietf-bess-mvpn-evpn-sr-p2mp] for point-to-multipoint
transport of a packet. When a Tree SID over SRv6 P-tunnel is
shared across different MVPNs, an IPv6 address in IPv6 source
address for identifying a VRF is possible.
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3. MVPN service can use Ingress Replication(IR) [RFC6513] to
simulate a point-to-multipoint P-tunnel. In an IPv6 environment,
Ingress Replication can use IPv6 encapsulation for each branch.
When the egress PE of an Ingress Replication P-tunnel branch
receives a packet, it gets to know the VRF of the packet through
the Destination address in the IPv6 header. This means that,
every egress PE of the IR P-tunnel branch need to allocate an
IPv6 address to identify a VRF. If the source segment is used
for the IPv6 source address, only one IPv6 address of the Ingress
PE is needed for identifying a VRF, and thus save the IPv6
addresses and their operation costs.
7. IANA Considerations
TBD
8. Security Considerations
TBD
9. References
9.1. Normative References
[RFC4443] Conta, A., Deering, S., and M. Gupta, Ed., "Internet
Control Message Protocol (ICMPv6) for the Internet
Protocol Version 6 (IPv6) Specification", STD 89,
RFC 4443, DOI 10.17487/RFC4443, March 2006,
<https://www.rfc-editor.org/info/rfc4443>.
[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>.
[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>.
[RFC6625] Rosen, E., Ed., Rekhter, Y., Ed., Hendrickx, W., and R.
Qiu, "Wildcards in Multicast VPN Auto-Discovery Routes",
RFC 6625, DOI 10.17487/RFC6625, May 2012,
<https://www.rfc-editor.org/info/rfc6625>.
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[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>.
[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>.
[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>.
[RFC8754] Filsfils, C., Ed., Dukes, D., Ed., Previdi, S., Leddy, J.,
Matsushima, S., and D. Voyer, "IPv6 Segment Routing Header
(SRH)", RFC 8754, DOI 10.17487/RFC8754, March 2020,
<https://www.rfc-editor.org/info/rfc8754>.
[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>.
9.2. Informative References
[I-D.cheng-spring-ipv6-msr-design-consideration]
Cheng, W., Mishra, G., Li, Z., Wang, A., Qin, Z., and C.
Fan, "Design Consideration of IPv6 Multicast Source
Routing (MSR6)", Work in Progress, Internet-Draft, draft-
cheng-spring-ipv6-msr-design-consideration-00, 12 July
2021, <https://www.ietf.org/archive/id/draft-cheng-spring-
ipv6-msr-design-consideration-00.txt>.
[I-D.ietf-6man-spring-srv6-oam]
Ali, Z., Filsfils, C., Matsushima, S., Voyer, D., and M.
Chen, "Operations, Administration, and Maintenance (OAM)
in Segment Routing Networks with IPv6 Data plane (SRv6)",
Work in Progress, Internet-Draft, draft-ietf-6man-spring-
srv6-oam-11, 2 June 2021,
<https://www.ietf.org/archive/id/draft-ietf-6man-spring-
srv6-oam-11.txt>.
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[I-D.ietf-bess-mvpn-evpn-sr-p2mp]
Parekh, R., Filsfils, C., Venkateswaran, A., Bidgoli, H.,
Voyer, D., and Z. Zhang, "Multicast and Ethernet VPN with
Segment Routing P2MP", Work in Progress, Internet-Draft,
draft-ietf-bess-mvpn-evpn-sr-p2mp-04, 19 October 2021,
<https://www.ietf.org/archive/id/draft-ietf-bess-mvpn-
evpn-sr-p2mp-04.txt>.
[I-D.ietf-bess-srv6-services]
Dawra, G., Filsfils, C., Talaulikar, K., Raszuk, R.,
Decraene, B., Zhuang, S., and J. Rabadan, "SRv6 BGP based
Overlay Services", Work in Progress, Internet-Draft,
draft-ietf-bess-srv6-services-07, 11 April 2021,
<https://www.ietf.org/archive/id/draft-ietf-bess-srv6-
services-07.txt>.
[I-D.ietf-rtgwg-dst-src-routing]
Lamparter, D. and A. Smirnov, "Destination/Source
Routing", Work in Progress, Internet-Draft, draft-ietf-
rtgwg-dst-src-routing-07, 10 March 2019,
<https://www.ietf.org/archive/id/draft-ietf-rtgwg-dst-src-
routing-07.txt>.
[I-D.ietf-spring-sr-replication-segment]
(editor), D. V., Filsfils, C., Parekh, R., Bidgoli, H.,
and Z. Zhang, "SR Replication Segment for Multi-point
Service Delivery", Work in Progress, Internet-Draft,
draft-ietf-spring-sr-replication-segment-05, 20 August
2021, <https://www.ietf.org/archive/id/draft-ietf-spring-
sr-replication-segment-05.txt>.
[I-D.raszuk-teas-ip-te-np]
Raszuk, R., "IP Traffic Engineering Architecture with
Network Programming", Work in Progress, Internet-Draft,
draft-raszuk-teas-ip-te-np-00, 2 October 2019,
<https://www.ietf.org/archive/id/draft-raszuk-teas-ip-te-
np-00.txt>.
[I-D.xie-bier-ipv6-encapsulation]
Xie, J., Geng, L., McBride, M., Asati, R., Dhanaraj, S.,
Zhu, Y., Qin, Z., Shin, M., Mishra, G., and X. Geng,
"Encapsulation for BIER in Non-MPLS IPv6 Networks", Work
in Progress, Internet-Draft, draft-xie-bier-ipv6-
encapsulation-10, 22 February 2021,
<https://www.ietf.org/archive/id/draft-xie-bier-ipv6-
encapsulation-10.txt>.
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[I-D.xie-bier-ipv6-mvpn]
Xie, J., McBride, M., Dhanaraj, S., Geng, L., and G.
Mishra, "Use of BIER IPv6 Encapsulation (BIERv6) for
Multicast VPN in IPv6 networks", Work in Progress,
Internet-Draft, draft-xie-bier-ipv6-mvpn-03, 10 October
2020, <https://www.ietf.org/archive/id/draft-xie-bier-
ipv6-mvpn-03.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>.
[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
Jingrong Xie
Huawei Technologies
Email: xiejingrong@huawei.com
Xuesong Geng
Huawei Technologies
Email: gengxuesong@huawei.com
Yisong Liu
China Mobile
Email: liuyisong@chinamobile.com
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