SRv6 and MPLS interworking
draft-ietf-spring-srv6-mpls-interworking-01
| Document | Type | Active Internet-Draft (spring WG) | |
|---|---|---|---|
| Authors | Swadesh Agrawal , Clarence Filsfils , Daniel Voyer , Gaurav Dawra , Zhenbin Li , Shraddha Hegde | ||
| Last updated | 2025-07-07 | ||
| Replaces | draft-agrawal-spring-srv6-mpls-interworking | ||
| RFC stream | Internet Engineering Task Force (IETF) | ||
| Intended RFC status | (None) | ||
| Formats | |||
| Additional resources | Mailing list discussion | ||
| Stream | WG state | WG Document | |
| Document shepherd | (None) | ||
| IESG | IESG state | I-D Exists | |
| Consensus boilerplate | Unknown | ||
| Telechat date | (None) | ||
| Responsible AD | (None) | ||
| Send notices to | (None) |
draft-ietf-spring-srv6-mpls-interworking-01
SPRING S. Agrawal, Ed.
Internet-Draft C. Filsfils
Intended status: Standards Track Cisco Systems
Expires: 8 January 2026 D. Voyer
Bell Canada
G. Dawra
LinkedIn
Z. Li
Huawei Technologies
S. Hegde
Juniper Networks
7 July 2025
SRv6 and MPLS interworking
draft-ietf-spring-srv6-mpls-interworking-01
Abstract
This document describes SRv6 and MPLS/SR-MPLS interworking
procedures. Interworking problem is generalized into various
interworking scenarios. These scenarios are stitched either by
transport interworking or service interworking. New SRv6 behaviors
are defined for the purpose. These new behaviors and MPLS labels
stitch end to end path across different data plane.
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 8 January 2026.
Agrawal, et al. Expires 8 January 2026 [Page 1]
Internet-Draft SRv6 and MPLS interworking July 2025
Copyright Notice
Copyright (c) 2025 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 . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3
2. Interworking(IW) scenarios . . . . . . . . . . . . . . . . . 3
2.1. Transport IW . . . . . . . . . . . . . . . . . . . . . . 4
2.2. Service IW . . . . . . . . . . . . . . . . . . . . . . . 5
3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5
4. SRv6 SID behavior . . . . . . . . . . . . . . . . . . . . . . 6
4.1. End.DTM . . . . . . . . . . . . . . . . . . . . . . . . . 6
4.2. End.DT46M . . . . . . . . . . . . . . . . . . . . . . . . 7
4.3. End.DPM . . . . . . . . . . . . . . . . . . . . . . . . . 8
5. SRv6 Policy Headend Behaviors . . . . . . . . . . . . . . . . 9
5.1. H.Encaps.M: H.Encaps applied to MPLS label stack . . . . 9
5.2. H.Encaps.M.Red: H.Encaps.Red applied to MPLS label
stack . . . . . . . . . . . . . . . . . . . . . . . . . . 9
6. Interconnecting Binding SIDs . . . . . . . . . . . . . . . . 9
7. Interworking Procedures . . . . . . . . . . . . . . . . . . . 10
7.1. Transport IW . . . . . . . . . . . . . . . . . . . . . . 10
7.1.1. SR-PCE multi-domain On Demand Nexthop . . . . . . . . 11
7.1.2. BGP inter domain routing procedures . . . . . . . . . 13
7.2. Service IW . . . . . . . . . . . . . . . . . . . . . . . 19
7.2.1. Gateway Interworking . . . . . . . . . . . . . . . . 19
7.2.2. Translation between Service labels and SRv6 service
SIDs . . . . . . . . . . . . . . . . . . . . . . . . 20
8. Migration and co-existence . . . . . . . . . . . . . . . . . 22
9. Availability . . . . . . . . . . . . . . . . . . . . . . . . 22
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 22
10.1. SRv6 Endpoint Behaviors . . . . . . . . . . . . . . . . 22
11. Security Considerations . . . . . . . . . . . . . . . . . . . 22
12. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 23
13. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 23
14. References . . . . . . . . . . . . . . . . . . . . . . . . . 23
14.1. Normative References . . . . . . . . . . . . . . . . . . 23
Agrawal, et al. Expires 8 January 2026 [Page 2]
Internet-Draft SRv6 and MPLS interworking July 2025
14.2. Informative References . . . . . . . . . . . . . . . . . 25
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 25
1. Introduction
The incremental deployment of SRv6 into existing networks require
SRv6 to interwork and co-exist with SR-MPLS/MPLS. This document
introduces interworking scenarios and building blocks for solutions
to interconnect them.
This document assumes SR-MPLS-IPv4 for MPLS domains but the design
equally works for SR-MPLS-IPv6, LDP-IPv4/IPv6 and RSVP-TE-MPLS label
binding protocols.
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. Interworking(IW) scenarios
A multi-domain network (Figure 1) can be generalized as a central
domain C with many leaf domains around it. Specifically, the
document looks at a service flow from an ingress PE in an ingress
leaf domain (LI), through the C domain and up to an egress PE of the
egress leaf domain (LE). Each domain runs its own IGP instance. A
domain has a single data plane type applicable both for its overlay
and its underlay.
Agrawal, et al. Expires 8 January 2026 [Page 3]
Internet-Draft SRv6 and MPLS interworking July 2025
+-----+ +-----+ RD:V/v via 10 +-----+
.......|S-RR1|<...............|S-RR2|<.................|S-RR3| <..
: +-----+ +-----+ +-----+ :
: :
: :
+--:-------------------+----------------------+---------------------:-+
| : | 2 | | | 5 | | | 8 | : |
| : +---+ | +---+ | +---+ : |
| : | | : |
| : | | : |
| : | | : |
|----+ IGP1 +---+ IGP2 +---+ IGP3 +----|
| 1 | | 4 | | 7 | | 10 |
|----+ +---+ +---+ +----|
| | | |
| | | |
| | | |
| +---+ | +---+ | +---+ |
| | 3 | | | 6 | | | 9 | |
+----------------------+----------------------+-----------------------+
iPE iBR eBR ePE
<----------LI---------><----------C----------><-----------LE---------->
Figure 1: Reference multi-domain network topology
There are various SRv6 and SR-MPLS-IPv4 interworking scenarios
possible.
Below scenarios cover various cascading of SRv6 and MPLS networks,
e.g., SR-MPLS-IPv4 <-> SRv6 <-> SR-MPLS-IPv4 <-> SRv6 <-> SR-MPLS-
IPv4 etc, though not all combinations are described for brevity.
2.1. Transport IW
Provider Edge (PE) devices deploy MPLS based [RFC4364] or SRv6
Service SID based [RFC9252] BGP services (L3VPN, EVPN, GRT) through
service Route Reflectors. Service endpoint (PE loopback address,
SRv6 locator) signaling through borders routers and corresponding
forwarding state provide interworking over intermediate transport
domain.
* SRv6 over MPLS (6oM)
- LI and LE domains are SRv6 data plane, C is MPLS data plane.
Agrawal, et al. Expires 8 January 2026 [Page 4]
Internet-Draft SRv6 and MPLS interworking July 2025
- L3/L2 BGP SRv6 service [RFC9252] extend between PEs. The
ingress PE encapsulates the service traffic in an outer IPv6
header where the SRv6 Service SID is the last segment or
destination address(DA).
- Transport IW border nodes forward SRv6 encapsulated traffic
destined to egress PE over MPLS C domain.
* MPLS over SRv6 (Mo6)
- LI and LE domains are MPLS data plane, C is SRv6 data plane.
- L3/L2 BGP MPLS service ([RFC4364], [RFC7432]) extend between
PEs. The ingress PE encapsulates the service traffic in an
MPLS service label and tunnel it through MPLS LSP to egress PE.
- Transport IW nodes forward encapsulated label stack to egress
PE over SRv6 C domain.
Note: Easiest and most probable deployment is ships in the night i.e.
supporting dual stack and IPv4 MPLS in each domain.
2.2. Service IW
BGP L2/L3 service signaling discontinuity between PEs i.e. SRv6
service SID based PE interworks with BGP MPLS based PE for service
connectivity. BGP L2/L3 service signaling encapsulation type change
and corresponding forwarding state at border router provide
interworking between domains.
* SRv6 to MPLS(6toM): The ingress PE encapsulates the service
traffic in an outer IPv6 header where the destination address is
the SRv6 Service SID[RFC9252]. Service traffic reaches egress PE
with an MPLS encapsulation where bottom most label is a service
label [RFC4364] that PE advertised with the service prefix.
* MPLS to SRv6 (Mto6): The ingress PE encapsulates the service
traffic in an MPLS encapsulation where bottom most label is a
service label. Service traffic reaches egress PE with IPv6
encapsulation where IPv6 destination address is a SRv6 service SID
that PE advertised with the service prefix.
3. Terminology
The following terms used within this document are defined in
[RFC8402]: Segment Routing, SR-MPLS, SRv6, SR Domain, Segment ID
(SID), SRv6 SID, Prefix-SID.
Agrawal, et al. Expires 8 January 2026 [Page 5]
Internet-Draft SRv6 and MPLS interworking July 2025
Domain: Without loss of the generality, domain is assumed to be
instantiated by a single IGP instance or a network within IGP if
there is clear separation of data plane.
Node k has a classic IPv6 loopback address Ak::1/128.
A SID at node k with locator block B and function F is represented by
B:k:F::
A SID list is represented as <S1, S2, S3> where S1 is the first SID
to visit, S2 is the second SID to visit and S3 is the last SID to
visit along the SR path.
(SA,DA) (S3, S2, S1; SL) represents an IPv6 packet with:
IPv6 header with source address SA, destination addresses DA and SRH
as next-header
SRH with SID list <S1, S2, S3> with SegmentsLeft = SL
Note the difference between the <> and () symbols: <S1, S2, S3>
represents a SID list where S1 is the first SID and S3 is the last
SID to traverse. (S3, S2, S1; SL) represents the same SID list but
encoded in the SRH format where the rightmost SID in the SRH is the
first SID and the leftmost SID in the SRH is the last SID. When
referring to an SR policy in a high-level use-case, it is simpler to
use the <S1, S2, S3> notation. When referring to an illustration of
the detailed packet behavior, the (S3, S2, S1; SL) notation is more
convenient.
4. SRv6 SID behavior
This document introduces a new SRv6 SID behaviors. These behaviors
are executed on border router between the SRv6 and MPLS domain.
4.1. End.DTM
The "Endpoint with decapsulation and MPLS table lookup" behavior.
The End.DTM SID MUST be the last segment in a SR Policy, and a SID
instance is associated with an MPLS table.
When N receives a packet destined to S and S is a local End.DTM SID,
N does:
Agrawal, et al. Expires 8 January 2026 [Page 6]
Internet-Draft SRv6 and MPLS interworking July 2025
S01. When an SRH is processed {
S02. If (Segments Left != 0) {
S03. Send an ICMP Parameter Problem to the Source Address,
Code 0 (Erroneous header field encountered),
Pointer set to the Segments Left field,
interrupt packet processing and discard the packet.
S04. }
S05. Proceed to process the next header in the packet
S06. }
When processing the Upper-layer header of a packet matching a FIB
entry locally instantiated as an End.DTM SID, N does:
S01. If (Upper-Layer Header type == 137(MPLS) ) {
S02. Remove the outer IPv6 Header with all its extension headers
S03. Set the packet's associated FIB table to T
S04. Submit the packet to the MPLS FIB lookup for
transmission according to the lookup result.
S05. } Else {
S06. Process as per RFC8986 section 4.1.1
S07. }
4.2. End.DT46M
The "Endpoint with decapsulation and MPLS or Global IP table lookup"
behavior.
The End.DT46M SID MUST be the last segment in a SR Policy, and a SID
instance is associated with an MPLS table and a Global IPv4 FIB table
and a Global IPv6 FIB table. This behavior is superset of End.DTM
and the procedures defined in the document using End.DTM works with
End.DT46M as well.
When N receives a packet destined to S and S is a local End.DT46M
SID, N does:
Agrawal, et al. Expires 8 January 2026 [Page 7]
Internet-Draft SRv6 and MPLS interworking July 2025
S01. When an SRH is processed {
S02. If (Segments Left != 0) {
S03. Send an ICMP Parameter Problem to the Source Address,
Code 0 (Erroneous header field encountered),
Pointer set to the Segments Left field,
interrupt packet processing and discard the packet.
S04. }
S05. Proceed to process the next header in the packet
S06. }
When processing the Upper-layer header of a packet matching a FIB
entry locally instantiated as an End.DT46M SID, N does:
S01. If (Upper-Layer Header type == 137(MPLS) ) {
S02. Remove the outer IPv6 Header with all its extension headers
S03. Set the packet's associated table to MPLS table
S04. Submit the packet to the MPLS FIB lookup for
transmission according to the lookup result.
S05. } Else if (Upper-Layer header type == 4(IPv4) ) {
S06. Remove the outer IPv6 header with all its extension headers
S07. Set the packet's associated FIB table to Global IPv4 table
S08. Submit the packet to the egress IPv4 FIB lookup for
transmission to the new destination
S09. } Else if (Upper-Layer header type == 41(IPv6) ) {
S10. Remove the outer IPv6 header with all its extension headers
S11. Set the packet's associated FIB table to Global IPv6 table
S12 Submit the packet to the egress IPv6 FIB lookup for
transmission to the new destination
S13 } Else {
S14. Process as per RFC8986 section 4.1.1
S15. }
4.3. End.DPM
The "Endpoint with decapsulation and MPLS label push" behavior.
The End.DPM SID MUST be the last segment and a SID instance is
associated with label stack.
When N receives a packet destined to S and S is a local End.DPM SID,
N does:
Agrawal, et al. Expires 8 January 2026 [Page 8]
Internet-Draft SRv6 and MPLS interworking July 2025
S01. When an SRH is processed {
S02. If (Segments Left != 0) {
S03. Send an ICMP Parameter Problem to the Source Address,
Code 0 (Erroneous header field encountered),
Pointer set to the Segments Left field,
interrupt packet processing and discard the packet.
S04. }
S05. Proceed to process the next header in the packet
S06. }
When processing the Upper-layer header of a packet matching a FIB
entry locally instantiated as an End.DPM SID, N does:
S01. Remove the outer IPv6 Header with all its extension headers
S02. Push the MPLS label stack associated with S
S03. Submit the packet to the MPLS engine for transmission
5. SRv6 Policy Headend Behaviors
5.1. H.Encaps.M: H.Encaps applied to MPLS label stack
The H.Encaps.M behavior encapsulates a received MPLS Label stack
[RFC3032] packet in an IPv6 header with an SRH. Together MPLS label
stack and its payload becomes the payload of the new IPv6 packet.
The Next Header field of the SRH MUST be set to 137 [RFC4023].
5.2. H.Encaps.M.Red: H.Encaps.Red applied to MPLS label stack
The H.Encaps.M.Red behavior is an optimization of the H.Encaps.M
behavior. H.Encaps.M.Red reduces the length of the SRH by excluding
the first SID in the SRH of the pushed IPv6 header. The first SID is
only placed in the Destination Address field of the pushed IPv6
header. The push of the SRH MAY be omitted when the SRv6 Policy only
contains one segment and there is no need to use any flag, tag or
TLV. In such case, the Next Header field of the IPv6 header MUST be
set to 137 [RFC4023].
6. Interconnecting Binding SIDs
Binding Segment (BSID) is bound to an SR policy [RFC8402] and
provides domain opacity. Opacity fits well for interworking because
an SR-MPLS label can be bound to an SRv6 Policy and an SRv6 SID can
be bound to an SR-MPLS Policy. Such BSIDs are called as
interconnecting BSIDs and help to represent intermediate domain of
different data plane type as a SID of ingress domain dataplane type
in the headend policy. The IW SR-PCE solution Section 7.1.1 leverage
these BSIDs as segments of SR policy on headend domain.
Agrawal, et al. Expires 8 January 2026 [Page 9]
Internet-Draft SRv6 and MPLS interworking July 2025
7. Interworking Procedures
Figure 1 shows reference multi-domain network topology and Section 2
its description. The procedure in this section are illustrated using
the topology.
Following is assumed for data plane support of various nodes:
* Nodes 2,3,5,6,8,9 are provider(P) routers which need to support
single data plane type.
* 1 and 10 are PEs. They support single data plane type in overlay
and underlay.
* Border routers 4 and 7 need to support both the SRv6 and SR-MPLS-
IPv4 data plane.
A VPN route is advertised via service RRs (S-RR) between an egress
PE(node 10) and an ingress PE (node 1).
For illustrations, the SRGB range starts from 16000 and prefix SID of
a node is 16000 plus node number
7.1. Transport IW
As described in Section 2.1, transport IW requires:
* For 6oM, tunnel traffic destined to SRv6 Service SID of egress PE
over MPLS C domain.
* For Mo6, tunnel MPLS label stack bound to IPv4 loopback address of
egress PE over SRv6 C domain.
This draft enhances two well-known solutions to achieve above:
* An SR-PCE [RFC8664] multi-domain On Demand Next-hop (ODN) SR
policy [RFC9256] stitching end to end across different data plane
domains using interconnecting binding SIDs. These procedures can
be used when overlay prefixes are signaled with a color extended
community [RFC9012].
* BGP Inter-Domain routing procedures advertising PE locator or IPv4
Loopback address for best effort or intent aware end to end
connectivity.
Agrawal, et al. Expires 8 January 2026 [Page 10]
Internet-Draft SRv6 and MPLS interworking July 2025
7.1.1. SR-PCE multi-domain On Demand Nexthop
This procedure provides a best-effort path as well as a path that
satisfies the intent (e.g. low latency), across multiple domains.
Service routes (VPN/EVPN) are received on ingress PE with color
extended community from egress PE. A Color is a 32-bit numerical
value that associates an SR Policy with an intent [RFC9256]. Ingress
PE does not know how to compute the traffic engineered path through
the multi-domain network to egress PE and requests SR-PCE for it.
The SR-PCE is aware of interworking requirement at border nodes as
its fed with BGP-LS topological information from each domain. It
programs intermediate domain data plane specific policy on border
nodes for the given intent and represents it in end to end path SID
list on ingress PE leveraging Section 6.
Below sections describe 6oM and Mo6 IW with SR-PCE
7.1.1.1. 6oM
Service prefix (e.g. VPN or EVPN) is received on head-end (node 1)
with color extended community (C1) from egress PE (node 10) with SRv6
service SID. The PCE computes (C1,10) path via node 2, 5 and 8. It
programs an SR policy at border node 4 with segment list node 5 and 7
bounded to an End.BM BSID [RFC8986]. SR-PCE responds back to node 1
with SRv6 segments along required SLA including End.BM at node 4 to
traverse SR-MPLS-IPv4 C domain.
For example, SR-PCE create SR-MPLS policy (C1,7) at node 4 with
segments <16005,16007>. It is bound to End.BM behavior with SRv6
BSID as B:4:BM-C1-7::
The data plane operations for the above-mentioned interworking
example are:
* Node 1 performs SRv6 function H.Encaps.Red with VPN service SID
and SRv6 Policy (C1,10):
Packet leaving node 1 IPv6 ((A:1::, B:2:E::) (B:10::DT4, B:8:E::,
B:4:BM-C1-7:: ; SL=3))
* Node 2 performs End function
Packet leaving node 2 IPv6 ((A:1::, B:4:BM-C1-7::) (B:10::DT4,
B:8:E::, B:4:BM-C1-7:: ; SL=2))
* Node 4(border rout4er) performs End.BM function
Agrawal, et al. Expires 8 January 2026 [Page 11]
Internet-Draft SRv6 and MPLS interworking July 2025
Packet leaving node 4 MPLS (16005,16007,2)((A:1::, B:8:E::)
(B:10::DT4, B:8:E::, B:4:BM-C1-7-:: ; SL=1)).
* Node 7 performs a native IPv6 lookup on due PHP behavior for 16007
Packet leaving node 7 IPv6 ((A:1::, B:8:E::) (B:10::DT4, B:8:E::,
B:4:BM-C1-7:: ; SL=1))
* Node 8 performs End(PSP) function
Packet leaving node 8 IPv6 ((A:1::, B:10::DT4))
* Node 10 performs End.DT function and lookups IP in VRF and send
traffic to CE.
7.1.1.2. Mo6
Refer Section 2.1 for Mo6 scenario. MPLS Service prefix (e.g. VPN or
EVPN) is received on head-end(node 1) with color extended
community(C1) from egress PE(node 10). The PCE computes color-aware
C1 path via node 2, 5 and 8. It programs a SRv6 policy bound to MPLS
BSID at border node 4 with SRv6 segment list along required color-
aware path with last segment of behavior End.DTM Section 4.1. SR-PCE
responds back to node 1 with MPLS segment list including MPLS BSID of
SRv6 policy at node 4 to traverse SRv6 core domain.
For example, SR-PCE create SRv6 policy (C1,7) at node 4 with segments
<B:5:E::,B:7:DTM::>. It is bound to MPLS BSID 24407.
The data plan operations for the above-mentioned interworking example
are:
1. Node 1 performs MPLS label stack encapsulation with VPN label and
SR-MPLS Policy (C1,10):
Packet leaving node 1 towards 2 (Note: PHP of node 2 prefix SID):
MPLS packet (16004,24407,16008,16010,vpn_label)
2. Node 2 forwards traffic towards 4 (PHP of 16004)
Packet leaving node 2 MPLS packet (24407,16008,16010,vpn_label)
3. Node 4 steers MPLS traffic into SRv6 policy bound to 24407
Packet leaving node 4 IPv6(A:4::, B:5:E::) (B:7:DTM:: ;
SL=1)NH=137) MPLS((16008,16010,vpn_label)
Agrawal, et al. Expires 8 January 2026 [Page 12]
Internet-Draft SRv6 and MPLS interworking July 2025
4. Node 7 receive IPv6 packet with DA=B:7:DTM::. It performs DTM
behavior to remove IPv6 header and perform 16008 lookup in MPLS
table.
Packet leaves node 7 towards node 8(PHP of 16008) MPLS packet
(16010,vpn_label)
5. Node 8 forwards traffic towards 10 (PHP of 16010)
Packet leaving node 8 MPLS packet (vpn_label)
6. Node 10 performs vpn_label lookup and send traffic to CE.
7.1.2. BGP inter domain routing procedures
Procedures described below build upon BGP Label Unicast (BGP-LU)
[I-D.ietf-mpls-seamless-mpls] and [RFC4798] to advertise transport
reachability of PE IPv4 loopbacks or SRv6 locators across a multi-
domain network. The procedures leverage existing SAFIs (for example,
BGP-LU(AFI=1 or 2 and SAFI=4) and IPv6 (SAFI=1,AFI=2)). Nexthop self
on border routers provide independence of intra domain tunnel
technology in different domains.
The sections below describe 6oM and Mo6 IW with BGP procedures for
best effort paths to a locator or loopback prefix. The procedures
are equally applicable to intent aware paths, i.e., locator assigned
for a given intent, for instance from an IGP-FlexAlgo. They are also
applicable to color-aware routes [I-D.ietf-idr-bgp-car] recursing
over intent aware intra-domain paths.
7.1.2.1. 6oM
Refer Section 2.1 for 6oM scenario. SRv6 based L3/L2 BGP services
are signaled with SRv6 Service SID allocated from egress PE locator
prefix and with no BGP Color Extended community. Ingress PE learns
the service routes and need to resolve SRv6 Service SID over egress
PE locator or its summary. Below describes propagation of locators
or its summary to create end to end underlay path.
* Egress border router learns LE domain PE locators through IGP and
redistribute in BGP. Alternatively, locator is originated by
egress PE in the BGP IPv6 unicast address family (AFI=2,SAFI=1) to
border nodes.
Agrawal, et al. Expires 8 January 2026 [Page 13]
Internet-Draft SRv6 and MPLS interworking July 2025
* Egress border router uses [RFC4798] 6PE procedure and advertise
these locator in BGP-LU [AFI=2,SAFI=4] with locally allocated
label or IPv6 Explicit NULL to ingress border router with IPv4
next hop. Next hop has SR MPLS IPv4 LSP paths built in C domain.
Note: Egress border router may advertise summary prefix covering
all PE locators in LE domain.
* Ingress border router advertise these remote locators or its
summary in LI domain. Options to advertise are:
- To ingress PE in BGP IPv6 address family (AFI=2,SAFI=1) with
SRv6 transport SID of local End behavior in Prefix-SID
attribute TLV type 5 [RFC9252]. This option will result in
additional SRv6 encapsulation at ingress PE.
- BGP hop by hop routing model to each of P and PE routers
through infrastructure route reflector. This option will avoid
additional SRv6 transport SID encapsulation at ingress PE.
- Leak remote locators or their summary in LI IGP (Typically on
transport ABR only infrastructure prefixes are present in BGP.
If that is not the case, proper filters need to be configured
for such leaking into IGP).
* Ingress PE learn remote locators or their summary with or without
SRv6 transport SID encapsulation. When learnt with SRv6 SID, it
builds the packet encapsulation that contains the SRv6 Service SID
and SRv6 transport SID in the SID list. SRv6 transport SID
tunnels traffic to ingress border node in LI domain (P routers
like 2 and 3 does not need remote locator state). When learnt
without SRv6 transport SID, the packet encapsulation contains the
SRv6 Service SID and forwarded hop by hop based on remote locator
IPv6 prefix lookup.
Example to advertise node 10 locator to node 1 with SRv6 SID
encapsulation:
| : | | : |
|----+ IGP1 +---+ IGP2 +---+ IGP3 +----|
| 1 | | 4 | | 7 | | 10 |
|----+ +---+ +---+ +----|
+----------------------+----------------------+-----------------------+
iPE iBR eBR ePE
<----------LI---------><----------C----------><-----------LE---------->
Agrawal, et al. Expires 8 January 2026 [Page 14]
Internet-Draft SRv6 and MPLS interworking July 2025
Figure 2: SNIPPET of Reference multi-domain network topology
1. Routing Protocol(RP) @10:
* In ISIS advertise locator B:10::/48
* BGP (AFI=1,SAFI=128) originates a VPN route RD:V/v via B:10::1
and Prefix-SID attribute B:10:DT4::. This route is advertised
to service RR.
2. RP @ 7:
* ISIS redistribute B:10::/48 into BGP
* BGP Originates B:10::/48 in (AFI=2,SAFI=4) with next hop node
7 and IPv6 Explicit Null label among border routers.
3. RP @ 4:
* BGP learns B:10::/48 with next hop node 7 and outgoing label.
* BGP advertise B:10::/48 in (AFI=2,SAFI=1) with next hop B:4::1
and Prefix-SID attribute tlv type 5 carrying local End
behavior function B:4:END:: to node 1
4. RP @ 1:
* BGP learns B:10::/48 via B:4::1 and Prefix-SID attribute TLV
type 5 with SRv6 SID B:4:END::
* BGP AFI=1,SAFI=128 learn service prefix RD:V/v, next hop
B:10::1 and PrefixSID attribute TLV type 5 with SRv6 SID
B:10:DT4
FIB state
@1: IPv4 VRF V/v => H.Encaps.red <B:4:END::, B:10:DT4::>
with SRH, SRH.NH=IPv4
@4: IPv6 Table: B:4:END:: => Update DA with B:10:DT4::,
set IPv6.NH=IPv4, pop the SRH
@4: IPv6 Table: B:10::/48 => push MPLS label 2 (Explicit NULL),
push MPLS Label 16007
@7: MPLS label 2 => pop and lookup next IPv6 DA
@7: IPv6 Table B:10::/48 => forward via ISIS path to 10
@10: IPv6 Table B:10:DT4:: => pop the outer header and lookup
the inner IPv4 DA in the VRF
Agrawal, et al. Expires 8 January 2026 [Page 15]
Internet-Draft SRv6 and MPLS interworking July 2025
7.1.2.2. Mo6
Refer Section 2.1 for Mo6 scenario. MPLS based L3/L2 BGP services
are signaled with IPv4 next-hop of egress PE through Service RRs with
no color extended community. Ingress PE need labelled reachability
to remote PE IPv4 loopback address advertised as next hop with
service routes.
BGP-LU [RFC8277] advertise IPv4 PE loopbacks. Next hop self is
performed on the border routers.
Following are options and protocol extensions to tunnel IPv4 PE
loopback LSP through SRv6 C domain
7.1.2.2.1. Tunnel BGP-LU LSP across SRv6 C domain
Intuitive solution for an MPLS-minded operator
* Existing BGP-LU label cross-connect on border routers for each PE
IPv4 loopback address.
* The lookups at the ingress border router are based on BGP-LU label
as usual
* Just the SR-MPLS IGP label to next hop is replaced by an IPv6
tunnel with DA = SRv6 SID associated with DTM behavior in C
domain.
* Ingress border router forwarding perform 3107 label swap and
H.Encaps.M with DA = SRv6 SID associated with DTM behavior
* Similar to MPLS-over-IP
Existing BGP-LU updates between border routers need to signal SRv6
SID associated with DTM behavior.
[I-D.agrawal-bess-bgp-srv6-mpls-interworking] proposes "SRv6 tunnel
for label route" TLV of the BGP Prefix-SID Attribute to signal SRv6
SID to tunnel MPLS packet with label in NLRI at the top of its label
stack through SRv6/IPv6 domain. Below describes the control plane
and corresponding FIB state to achieve such tunneling:
Control plane example
1. Routing Protocol(RP) @10:
* ISIS originates its IPv4 PE loopback with Node SID 16010
Agrawal, et al. Expires 8 January 2026 [Page 16]
Internet-Draft SRv6 and MPLS interworking July 2025
* BGP AFI=1,SAFI=4 originate IPv4 loopback address with next hop
node 10 and optionally label index=10 in Label-Index TLV of
Prefix-SID attribute.
* BGP AFI=1,SAFI=128 originates a VPN route RD:V/v next hop node
10. This route is advertised to service RR.
2. RP @ 7:
* ISIS v6, advertise locator B:7::/48 in C domain
* BGP learns node 10 IPv4 loopback address with outgoing label.
It allocates local label (based on label index if present) and
programs label swap to outgoing label and MPLS LSP to next
hop.
* BGP AFI=1,SAFI=4 advertise IPv4 loopback address of node 10 to
node 4. NLRI label is set to local label and SRv6 SID
B:7:DTM:: carried in SRv6 SID Information Sub-TLV of "SRv6
tunnel for label route" TLV in Prefix-Sid attribute. If
received, label index=10 in Label-Index TLV of Prefix-SID
attribute is also signaled.
3. RP @ 4:
* ISIS v4 originates its IPv4 loopback with prefix SID 16004 in
LI domain.
* BGP learns node10 IPv4 loopback address from node 7 with
outgoing label. It allocate local label (based on label index
if present) and programs label swap and H.Encaps.M.red with
IPv6 header destination address as SRv6 SID received in "SRv6
tunnel for label route" TLV of Prefix-Sid attribute i.e.
B:7:DTM::.
* BGP AFI=1,SAFI=4 advertise IPv4 Loopback address of node 10 to
node 1. NLRI label is set to local label and do not signal
"SRv6 tunnel for label route" TLV in Prefix-SID attribute.
4. RP @ 1:
* BGP learns IPv4 loopback address of node 10 from node 4 with
outgoing label. It programs route to push outgoing label and
MPLS LSP to next hop i.e. node 4
* BGP AFI=1,SAFI=128 learn service prefix RD:V/v, next hop IPv4
loopback address of node 10 and service label.
Agrawal, et al. Expires 8 January 2026 [Page 17]
Internet-Draft SRv6 and MPLS interworking July 2025
Forwarding state at different nodes:
@1: IPv4 VRF: V/v => out label=vpn_label, next hop=IPv4 address of node 10
@1: IPv4 table: IPv4 address of node 10 => out label=16010, next hop=node4
@1: IPv4 table: IPv4 address of node 4 => out label=16004, next hop=interface to reach 2
@4: MPLS Table: 16010 => out label=16010, H.Encaps.M.red with DA=B:7:DTM::
@4: IPv6 table: B:7::/48 => next hop=interface to reach 5
@7: SRv6 My SID table: B:7:DTM:: => decaps IPv6 header and lookup top label.
@7: MPLS table: 16010 => out label=16010, next hop=interface to reach 8
@10: MPLS table: vpn label => pop label and lookup the inner IPv4 DA in the VRF
During transition when MPLS data plane is still enabled in C domain,
an ABR that does not understand "SRv6 tunnel for label route" TLV in
BGP Prefix-SID Attribute or based on operator configured local policy
can continue MPLS encapsulation using label in NLRI and LSP to next
hop.
7.1.2.2.2. Label and SRv6 SID translation per BGP LU route
For each PE IPv4 loopback address, existing BGP-LU label cross-
connect on area border router is replaced by label to SRv6 SID cross-
connect or vice versa. In effect, it creates a translation between
from 3107 label to SRv6 SID at ingress of SRv6 domain and SRv6 SID to
3107 label on egress.
* For each BGP-LU route (IPv4 loopback address of PE) received from
LE domain on egress border router, allocate SRv6 SID of DPM
behavior bound to the PE address. Lookup of SRv6 SID result in
decapsulation of IPv6 header and push of BGP-LU outgoing label and
MPLS LSP to next hop.
* Advertise BGP route to PE address with SRv6 SID to ingress border
router.
* Ingress border router allocate local label and advertise to LI
domain.
* The lookups at the ingress border router are based on BGP-LU label
as usual. Lookup results SRv6 SID of DPM behavior signaled by
egress border node. Decap BGP-LU label and perform H.Encaps.M
with DA = SRv6 SID.
Section 2.2 of [I-D.agrawal-bess-bgp-srv6-mpls-interworking]
describes how existing BGP advertisement can signal SRv6 SID
associated with DPM behavior from egress to ingress border router.
Agrawal, et al. Expires 8 January 2026 [Page 18]
Internet-Draft SRv6 and MPLS interworking July 2025
7.1.2.3. Global table services over BGP-LU transport
Procedures as defined in Section 7.1.2.2 works for global table
services ([RFC4271], [RFC2545]) over BGP-LU transport when service
endpoint is beyond border node (example node 10). In scenarios where
service endpoint is border node, additional SRv6 decapsulation
behavior is required that performs service traffic IP destination
lookup in global IPv4 or IPv6 table. In such deployment, border node
advertise its existing IPv4 PE loopback address in BGP-LU as per
Section 7.1.2.2.1 where SRv6 SID is associated with End.DT46M
behavior instead of END.DTM.
7.2. Service IW
As described in Section 2.2 Service IW need BGP SRv6 based L2/L3 PE
interworking with BGP MPLS based L2/L3 PE.
There are a number of different ways of handling this scenario as
detailed below.
7.2.1. Gateway Interworking
Gateway is IW role that which supports both BGP SRv6 based L2/L3
services and BGP MPLS based L2/L3 services for a service instance
(e.g. L3 VRF, EVPN EVI). It terminates service encapsulation and
perform L2/L3 destination lookup in service instance. This is
similar to inter-as option A on the single node instead of back to
back VRF interfaces between ABRs/ASBRs.
* A border router between SRv6 domain and SR-MPLS-IPv4 domain is
suitable for Gateway role.
* Transport reachability to SRv6 PE and gateway locators in SRv6
domain or MPLS LSP to PE/gateway IPv4 Loopbacks can be exchanged
in IGP or through mechanism detailed in Section 2.1.
* Gateway exchange BGP L2/L3 service prefix with SRv6 based Service
PEs via set of service RRs. This session will learn/advertise L3/
L2 service prefixes with SRv6 service SID in prefix SID attribute
[RFC9252].
* Gateway exchange BGP L2/L3 service prefix with MPLS based Service
PEs via set of distinct service RRs. This session will learn/
advertise L3/L2 service prefixes with service labels [RFC4364]
[RFC7432].
Agrawal, et al. Expires 8 January 2026 [Page 19]
Internet-Draft SRv6 and MPLS interworking July 2025
* L2/L3 prefix received from a domain is locally installed in
service instance and re advertised to other domain with modified
service encapsulation information.
* Prefix learned with SRv6 service SID from SRv6 PE is installed in
service instance with instruction to perform H.Encaps. It is
advertised to MPLS service PE with service label. When gateway
receives traffic with service label from MPLS service PE, it
perform destination lookup in service instance. Lookup result in
instruction to perform H.Encaps with DA being SRv6 Service SID
learnt with prefix from SRv6 PE.
* Prefix learned with MPLS service label from MPLS service PE is
installed in service instance with instruction to perform service
label encapsulation and send to MPLS LSP to nexthop. It is
advertised to SRv6 service PE with SRv6 service SID of behavior
(e.g. DT4/DT6/DT2U) [RFC8986]. When gateway receives traffic with
SRv6 Service SID as DA of IPv6 header from SRv6 service PE, it
perform destination lookup in service instance after decaps of
IPv6 header. Lookup result in instruction to push service label
and send it to nexthop.
+-------------------+ +-------------------+
| ....|S-RR|.... | | ....|S-RR|..... |
| : +----+ : | | : +----+ : |
| : : | | : : |
|----+ +-------------------------------------+ +----|
|PE1 | | IW border node | | PE2|
|----+ | VPN Label<->L2/L3 lookup<->SRv6 SID | +----|
| | | |
| +-------------------------------------+ |
| MPLS | | SRv6 |
+-------------------+ +-------------------+
<------MPLS VPN-----> <------SRv6 VPN----->
Figure 3: Gateway IW
Couple of border routers can act as gateway for redundancy. It can
scale horizontally by distributing service instance among them.
7.2.2. Translation between Service labels and SRv6 service SIDs
This is similar to inter-as option B procedures described in
[RFC4364] just that service label cross-connect on border router is
replaced with service label to SRv6 service SID or vice verse
translation on IW node.
Agrawal, et al. Expires 8 January 2026 [Page 20]
Internet-Draft SRv6 and MPLS interworking July 2025
* IW node does not need service instance like VRF or EVI.
* IW node exchange BGP L2/L3 service prefix with SRv6 based Service
PEs via set of service RRs. This BGP session will learn/advertise
L3/L2 service prefixes with SRv6 service SID in prefix SID
attribute [RFC9252].
* IW node exchange BGP L2/L3 service prefix with MPLS based service
PEs via set of distinct service RRs. This BGP session will learn/
advertise L3/L2 service prefixes with service labels [RFC4364]
[RFC7432].
* IW node allocates SRv6 SID of behavior End.DPM that result in
pushing service label and MPLS label stack to service nexthop for
BGP L2/L3 service learnt from MPLS PE. It advertises the service
to SRv6 domain.
* IW node allocates service label that results in H.Encaps with IPv6
header DA set to SRv6 SID signaled in BGP L2/L3 service learnt
from SRv6 PE. Advertises the service to MPLS domain with
allocated service label.
+-------------------+ +-------------------+
| ....|S-RR|.... | | ....|S-RR|..... |
| : +----+ : | | : +----+ : |
| : : | | : : |
|----+ +-------------------------------------+ +----|
|PE1 | | IW border node | | PE2|
|----+ | VPN Label -> SRv6 SID | +----|
| | VPN label, LSP PE1 <- SRv6 SID | |
| +-------------------------------------+ |
| MPLS | | SRv6 |
+-------------------+ +-------------------+
<------MPLS VPN-----> <------SRv6 VPN----->
Figure 4: Service translation
Certain L2 service specific information (eg. control word)
translation is out of the scope. It will be covered in separate
document.
Agrawal, et al. Expires 8 January 2026 [Page 21]
Internet-Draft SRv6 and MPLS interworking July 2025
8. Migration and co-existence
In addition, the draft also addresses migration and coexistence of
the SRv6 and SR-MPLS-IPv4. Co-existence means a network that
supports both SRv6 and MPLS in a given domain. This may be a
transient state when brownfield SR-MPLS-IPv4 network upgrades to SRv6
(migration) or permanent state when some devices are not capable of
SRv6 but supports native IPv6 and SR-MPLS-IPv4.
These procedures would be detailed in a future revision
9. Availability
* Failure within domain are taken care by existing FRR mechanisms
[I-D.ietf-rtgwg-segment-routing-ti-lfa].
* Procedures listed in [RFC9256] provides protection in SR-PCE
multi-domain On Demand Nexthop (ODN) SR policy based approach.
* Convergence on failure of border routers can be achieved by well
known methods for BGP inter domain routing approach:
- BGP Add Path provide diverse path visibility
- BGP backup path pre-programming
- Sub-second convergence on border router failure notified by
local IGP.
10. IANA Considerations
10.1. SRv6 Endpoint Behaviors
This document introduces a new SRv6 Endpoint behaviors "End.DTM" and
"End.DPM". IANA is requested to assign identifier value in the "SRv6
Endpoint Behaviors" sub-registry under "Segment Routing Parameters"
registry.
+-------------+--------+-------------------------+------------------+
| Value | Hex | Endpoint behavior | Reference |
+-------------+--------+-------------------------+------------------+
| 73 | 0x0049 | End.DTM | <this document> |
+-------------+--------+-------------------------+------------------+
| TBD | TBD | End.DPM | <this document> |
+-------------+--------+-------------------------+------------------+
11. Security Considerations
Agrawal, et al. Expires 8 January 2026 [Page 22]
Internet-Draft SRv6 and MPLS interworking July 2025
12. Contributors
Zafar Ali
Cisco Systems
Email: zali@cisco.com
Srihari Sangli
Juniper Networks
Email: ssangli@juniper.net
13. Acknowledgements
The authors would like to acknowledge Kamran Raza, Dhananjaya Rao,
Stephane Litkowski, Pablo Camarillo, Ketan Talaulikar, Jorge Rabadan,
Bruno Decraene for their comments and review.
14. References
14.1. Normative References
[I-D.agrawal-bess-bgp-srv6-mpls-interworking]
Agrawal, S., Rao, D., Ali, Z., Filsfils, C., Voyer, D.,
Dawra, G., and Z. Li, "BGP extensions for SRv6 and MPLS
interworking", Work in Progress, Internet-Draft, draft-
agrawal-bess-bgp-srv6-mpls-interworking-01, 23 July 2024,
<https://datatracker.ietf.org/doc/html/draft-agrawal-bess-
bgp-srv6-mpls-interworking-01>.
[I-D.ietf-idr-bgp-car]
Rao, D. and S. Agrawal, "BGP Color-Aware Routing (CAR)",
Work in Progress, Internet-Draft, draft-ietf-idr-bgp-car-
16, 20 February 2025,
<https://datatracker.ietf.org/doc/html/draft-ietf-idr-bgp-
car-16>.
[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>.
[RFC2545] Marques, P. and F. Dupont, "Use of BGP-4 Multiprotocol
Extensions for IPv6 Inter-Domain Routing", RFC 2545,
DOI 10.17487/RFC2545, March 1999,
<https://www.rfc-editor.org/info/rfc2545>.
Agrawal, et al. Expires 8 January 2026 [Page 23]
Internet-Draft SRv6 and MPLS interworking July 2025
[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>.
[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>.
[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>.
[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>.
[RFC4798] De Clercq, J., Ooms, D., Prevost, S., and F. Le Faucheur,
"Connecting IPv6 Islands over IPv4 MPLS Using IPv6
Provider Edge Routers (6PE)", RFC 4798,
DOI 10.17487/RFC4798, February 2007,
<https://www.rfc-editor.org/info/rfc4798>.
[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>.
Agrawal, et al. Expires 8 January 2026 [Page 24]
Internet-Draft SRv6 and MPLS interworking July 2025
[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>.
[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>.
[RFC9256] Filsfils, C., Talaulikar, K., Ed., Voyer, D., Bogdanov,
A., and P. Mattes, "Segment Routing Policy Architecture",
RFC 9256, DOI 10.17487/RFC9256, July 2022,
<https://www.rfc-editor.org/info/rfc9256>.
14.2. 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://datatracker.ietf.org/doc/html/draft-ietf-mpls-
seamless-mpls-07>.
[I-D.ietf-rtgwg-segment-routing-ti-lfa]
Bashandy, A., Litkowski, S., Filsfils, C., Francois, P.,
Decraene, B., and D. Voyer, "Topology Independent Fast
Reroute using Segment Routing", Work in Progress,
Internet-Draft, draft-ietf-rtgwg-segment-routing-ti-lfa-
21, 12 February 2025,
<https://datatracker.ietf.org/doc/html/draft-ietf-rtgwg-
segment-routing-ti-lfa-21>.
[RFC9012] Patel, K., Van de Velde, G., Sangli, S., and J. Scudder,
"The BGP Tunnel Encapsulation Attribute", RFC 9012,
DOI 10.17487/RFC9012, April 2021,
<https://www.rfc-editor.org/info/rfc9012>.
Authors' Addresses
Swadesh Agrawal (editor)
Cisco Systems
Email: swaagraw@cisco.com
Agrawal, et al. Expires 8 January 2026 [Page 25]
Internet-Draft SRv6 and MPLS interworking July 2025
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
Zhenbin Li
Huawei Technologies
China
Email: lizhenbin@huawei.com
Shraddha Hegde
Juniper Networks
Email: shraddha@juniper.net
Agrawal, et al. Expires 8 January 2026 [Page 26]