Inter-Domain Routing
Internet-Draft
Intended status: Standards Track G. Dawra, Ed.
Expires: December 27, 2018 LinkedIn
C. Filsfils
D. Dukes
P. Brissette
P. Camarilo
Cisco Systems
J. Leddy
Comcast
D. Voyer
D. Bernier
Bell Canada
D. Steinberg
Steinberg Consulting
R. Raszuk
Bloomberg LP
B. Decraene
Orange
S. Matsushima
SoftBank
S. Zhuang
Huawei Technologies
June 25, 2018
BGP Signaling of IPv6-Segment-Routing-based VPN Networks
draft-dawra-idr-srv6-vpn-04
Abstract
This draft defines procedures and messages for BGP SRv6-based L3VPN
and EVPN. It builds on RFC4364 "BGP/MPLS IP Virtual Private Networks
(VPNs)" and RFC7432 "BGP MPLS-Based Ethernet VPN" and provides a
migration path from MPLS-based VPNs to SRv6 based VPNs.
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/.
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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
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 December 27, 2018.
Copyright Notice
Copyright (c) 2018 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
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include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. SRv6-VPN SID TLV . . . . . . . . . . . . . . . . . . . . . . 4
3. BGP based L3 over SRv6 . . . . . . . . . . . . . . . . . . . 5
3.1. IPv4 VPN Over SRv6 Core . . . . . . . . . . . . . . . . . 6
3.2. IPv6 VPN Over SRv6 Core . . . . . . . . . . . . . . . . . 6
3.3. Global IPv4 over SRv6 Core . . . . . . . . . . . . . . . 7
3.4. Global IPv6 over SRv6 Core . . . . . . . . . . . . . . . 7
4. BGP based Ethernet VPN(EVPN) over SRv6 . . . . . . . . . . . 8
4.1. Ethernet Auto-discovery Route over SRv6 Core . . . . . . 9
4.1.1. EVPN Route Type-1(Per ES AD) . . . . . . . . . . . . 9
4.1.2. Prefix Type-1(Per EVI/ES AD) . . . . . . . . . . . . 10
4.2. MAC/IP Advertisement Route(Type-2) with SRv6 Core . . . . 10
4.3. Inclusive Multicast Ethernet Tag Route with SRv6 Core . . 12
4.4. Ethernet Segment Route with SRv6 Core . . . . . . . . . . 13
4.5. IP prefix router(Type-5) with SRv6 Core . . . . . . . . . 14
4.6. Multicast routes (EVPN Route Type-6, Type-7, Type-8) . . 14
5. Migration from L3 MPLS based Segment Routing to SRv6 Segment
Routing . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
6. Implementation Status . . . . . . . . . . . . . . . . . . . . 15
7. Error Handling of BGP SRv6 SID Updates . . . . . . . . . . . 16
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16
9. Security Considerations . . . . . . . . . . . . . . . . . . . 17
10. Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . 17
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 17
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11.1. Normative References . . . . . . . . . . . . . . . . . . 17
11.2. Informative References . . . . . . . . . . . . . . . . . 18
11.3. URIs . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 19
Appendix B. Contributors . . . . . . . . . . . . . . . . . . . . 19
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 19
1. Introduction
SRv6 refers to Segment Routing instantiated on the IPv6 dataplane [I-
D.filsfils-spring-srv6-network-programming][I-D.ietf-6man-segment-rou
ting-header].
SRv6-based VPN (SRv6-VPN) refers to the creation of VPN between PE's
leveraging the SRv6 dataplane and more specifically the END.DT*
(crossconnect to a VRF) and END.DX* (crossconnect to a nexthop).
SRv6-L3VPN refers to the creation of Layer3 VPN service between PE's
supporting an SRv6 data plane. SRv6-EVPN refers to the creation of
Layer2/Layer3 VPN service between PE's supporting an SRv6 data plane.
SRv6 SID refers to a SRv6 Segment Identifier as defined in
[I-D.filsfils-spring-srv6-network-programming].
SRv6-VPN SID refers to an SRv6 SID that MAY be associated with one of
the END.DT or END.DX functions as defined in
[I-D.filsfils-spring-srv6-network-programming].
To provide SRv6-VPN service with best-effort connectivity, the egress
PE signals an SRv6-VPN SID with the VPN route. The ingress PE
encapsulates the VPN packet in an outer IPv6 header where the
destination address is the SRv6-VPN SID provided by the egress PE.
The underlay between the PE's only need to support plain IPv6
forwarding [RFC2460].
To provide SRv6-VPN service in conjunction with an underlay SLA from
the ingress PE to the egress PE, the egress PE colors the overlay VPN
route with a color extended community. The ingress PE encapsulates
the VPN packet in an outer IPv6 header with an SRH that contains the
SR policy associated with the related SLA followed by the SRv6-VPN
SID associated with the route. The underlay nodes whose SRv6 SID's
are part of the SRH must support SRv6 data plane.
BGP is used to advertise the reachability of prefixes in a particular
VPN from an egress Provider Edge (egress-PE) to ingress Provider Edge
(ingress-PE) nodes.
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This document describes how existing BGP messages between PEs may
carry SRv6 Segment IDs (SIDs) as a means to interconnect PEs and form
VPNs.
2. SRv6-VPN SID TLV
The SRv6-VPN SID TLV is defined as another TLV for BGP-Prefix-SID
Attribute [I-D.ietf-idr-bgp-prefix-sid]. The value field of the BGP
Prefix SID attribute is defined here to be a set of elements encoded
as "Type/Length/Value" (i.e., a set of TLVs). Type for SRv6-VPN SID
TLV is defined to be TBD.
When an egress-PE is capable of SRv6 data-plane, it SHOULD signal
SRv6-VPN SID TLV within the Prefix-SID attribute attached to MP-BGP
VPN NLRI defined in [RFC4659][RFC5549][RFC7432][RFC4364] when egress-
PE is capable of SRv6 data-plane.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | RESERVED |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SRv6 SID information(Variable) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
SRv6 SID information is encoded as follows:
+---------------------------------------+
| SID Type (1 Octet) |
+---------------------------------------+
| SID Flags (1 octet) |
+---------------------------------------+
| SRv6 SID (16 octet) |
+---------------------------------------+
Where:
o Type is TBD
o Length: 16bit field. The total length of the value portion of the
TLV.
o RESERVED: 8 bit field. SHOULD be 0 on transmission and MUST be
ignored on reception.
Current Type of SID defined as:
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o Type-1 - corresponds to the equivalent functionality provided by a
VPN MPLS Label attribute when received with a route containing a
MPLS label[RFC4364]. Some functions which MAY be encoded are
End.DX4, End.DT4, End.DX6, End.DT6 etc.
o Type-2 - corresponds to the equivalent functionality provided by a
MPLS Label1 for EVPN Route-Types as defined in [RFC7432]. Some
functions which MAY be encoded are End.DX2, End.DX2V, End.DT2U,
End.DT2M / Arg.FE2 etc.
o SID Flags: 8 bit field which define the flags associated with the
SID. SHOULD be 0 on transmission and MUST be ignored on
reception.
3. BGP based L3 over SRv6
BGP egress nodes (egress-PEs) advertise a set of reachable prefixes.
Standard BGP update propagation schemes [RFC4271], which MAY make use
of route reflectors [RFC4456], are used to propagate these prefixes.
BGP ingress nodes (ingress-PE) receive these advertisements and may
add the prefix to the RIB in an appropriate VRF.
Egress-PEs which supports SRv6-VPN advertises an SRv6-VPN SID with
VPN routes. This SRv6-VPN SID only has local significance at the
egress-PE, where it is allocated or configured on a per-CE or per-VRF
basis. In practice, the SID encodes a cross-connect to a specific
Address Family table (END.DT) or next-hop/interface (END.DX) as
defined in the SRv6 Network Programming Document
[I-D.filsfils-spring-srv6-network-programming]
The SRv6-VPN SID MAY be routable within the AS of the egress-PE and
serves the dual purpose of providing reachability between ingress-PE
and egress-PE while also encoding the VPN identifier.
To support SRv6 based L3VPN overlay, a SID is advertised with BGP
MPLS L3VPN route update[RFC4364]. SID is encoded in a SRv6-VPN SID
TLV, which is optional transitive BGP Prefix SID
attribute[I-D.ietf-idr-bgp-prefix-sid]. This attribute serves two
purposes; first it indicates that the BGP egress device is reachable
via an SRv6 underlay and the BGP ingress device receiving this route
MAY choose to encapsulate or insert an SRv6 SRH, second it indicates
the value of the SID to include in the SRH encapsulation. For L3VPN,
only a single SRv6-VPN SID MAY be necessary. A BGP speaker
supporting an SRv6 underlay MAY distribute SID per route via the BGP
SRv6-VPN Attribute. If the BGP speaker supports MPLS based L3VPN
simultaneously, it MAY also populate the Label values in L3VPN route
types and allow the BGP ingress device to decide which encapsulation
to use. If the BGP speaker does not support MPLS based L3VPN
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services the MPLS Labels in L3VPN route types MUST be set to
IMPLICIT-NULL. Similarly, to support SRv6 based EVPN a SID (or
multiple SIDs) are advertised in route-types 1, 2, 3 and 5[RFC7432]
At an ingress-PE, BGP installs the advertised prefix in the correct
RIB table, recursive via an SR Policy leveraging the received
SRv6-VPN SID.
Assuming best-effort connectivity to the egress PE, the SR policy has
a path with a SID list made up of a single SID: the SRv6-VPN SID
received with the related BGP route update.
However, when VPN route is colored with an extended color community C
and signaled with Next-Hop N and the ingress PE has a valid SRv6
Policy (N, C) associated with SID list <S1,S2, S3>
[I-D.filsfils-spring-segment-routing-policy] then the SR Policy is
<S1, S2, S3, SRv6-VPN SID>.
Multiple VPN routes MAY resolve recursively on the same SR Policy.
3.1. IPv4 VPN Over SRv6 Core
IPv4 VPN Over IPv6 Core is defined in [RFC5549], the MP_REACH_NLRI is
encoded as follows for an SRv6 Core:
o AFI = 1
o SAFI = 128
o Length of Next Hop Network Address = 16 (or 32)
o Network Address of Next Hop = IPv6 address of the egress PE
o NLRI = IPv4-VPN routes
o Label = Implicit-Null
SRv6-VPN SID is encoded as part of the SRv6-VPN SID TLV defined in
Section 2. The function of the SRv6 SID is entirely up to the
originator of the advertisement. In practice, the function may
likely be End.DX4 or End.DT4.
3.2. IPv6 VPN Over SRv6 Core
IPv6 VPN over IPv6 Core is defined in [RFC4659], the MP_REACH_NLRI is
enclosed as follows for an SRv6 Core:
o AFI = 2
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o SAFI = 128
o Length of Next Hop Network Address = 16 (or 32)
o Network Address of Next Hop = IPv6 address of the egress PE
o NLRI = IPv6-VPN routes
o Label = Implicit-Null
SRv6-VPN SID are encoded as part of the SRv6-VPN SID TLV defined in
Section 2. The function of the IPv6 SRv6 SID is entirely up to the
originator of the advertisement. In practice the function may likely
be End.DX6 or End.DT6.
3.3. Global IPv4 over SRv6 Core
IPv4 over IPv6 Core is defined in [RFC5549]. The MP_REACH_NLRI is
encoded with:
o AFI = 1
o SAFI = 1
o Length of Next Hop Network Address = 16 (or 32)
o Network Address of Next Hop = IPv6 address of Next Hop
o NLRI = IPv4 routes
SRv6 SID for Global IPv4 routes is encoded as part of the SRv6-VPN
SID defined in Section 2. The function of the SRv6 SID is entirely
up to the originator of the advertisement. In practice, the function
may likely be End.DX6 or End.DT6.
3.4. Global IPv6 over SRv6 Core
The MP_REACH_NLRI is encoded with:
o AFI = 2
o SAFI = 1
o Length of Next Hop Network Address = 16 (or 32)
o Network Address of Next Hop = IPv6 address of Next Hop
o NLRI = IPv6 routes
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SRv6 SID for Global IPv6 routes is encoded as part of the SRv6-VPN
SID defined in Section 2. The function of the SRv6 SID is entirely
up to the originator of the advertisement. In practice, the function
may likely be End.DX6 or End.DT6.
Also, by utilizing the SRv6-VPN SID TLV, as defined in Section 2, to
encode the Global SID, BGP free core is possible by encapsulating all
BGP traffic from edge to edge over SRv6.
4. BGP based Ethernet VPN(EVPN) over SRv6
Ethernet VPN(EVPN), as defined in [RFC7432] provides an extendable
method of building an EVPN overlay. It primarily focuses on MPLS
based EVPNs but calls out the extensibility to IP based EVPN
overlays. It defines 4 route-types which carry prefixes and MPLS
Label attributes, the Labels each have specific use for MPLS
encapsulation of EVPN traffic. The fifth route-type carrying MPLS
label information (and thus encapsulation information) for EVPN is
defined in[I-D.ietf-bess-evpn-prefix-advertisement]. The Route Types
discussed below are:
o Ethernet Auto-discovery Route
o MAC/IP Advertisement Route
o Inclusive Multicast Ethernet Tag Route
o Ethernet Segment route
o IP prefix route
o Selective Multicast route
o IGMP join sync route
o IGMP leave sync route
To support SRv6 based EVPN overlays a SID is advertised in route-type
1,2,3 and 5 above. The SID (or SIDs) per route-type are advertised
in a new SRv6-VPN SID TLV which is optional transitive BGP Prefix SID
attribute. This attribute serves two purposes; first it indicates
that the BGP egress device is reachable via an SRv6 underlay and the
BGP ingress device receiving this route MAY choose to encapsulate or
insert an SRv6 SRH, second it indicates the value of the SID or SIDs
to include in the SRH encapsulation. A BGP speaker supporting an
SRv6 underlay MAY distribute SIDs per route via the BGP SRv6
Attribute. If the BGP speaker supports MPLS based EVPN
simultaneously it MAY also populate the Label values in EVPN route
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types and allow the BGP ingress device to decide which encapsulation
to use. If the BGP speaker does not support MPLS based EVPN services
the MPLS Labels in EVPN route types MUST be set to IMPLICIT-NULL.
4.1. Ethernet Auto-discovery Route over SRv6 Core
Ethernet Auto-discovery (A-D) routes are Type-1 route type defined in
[RFC7432]and may be used to achieve split horizon filtering, fast
convergence and aliasing. EVPN route type-1 is also used in EVPN-
VPWS as well as in EVPN flexible cross-connect; mainly used to
advertise point-to-point services id.
Multi-homed PEs MAY advertise an Ethernet auto discovery route per
Ethernet segment with the introduced ESI MPLS label extended
community defined in [RFC7432]. PEs may identify other PEs connected
to the same Ethernet segment after the EVPN type-4 ES route exchange.
All the multi-homed and remote PEs that are part of same EVI may
import the auto discovery route.
EVPN Route Type-1 is encoded as follows for SRv6 Core:
+---------------------------------------+
| RD (8 octets) |
+---------------------------------------+
|Ethernet Segment Identifier (10 octets)|
+---------------------------------------+
| Ethernet Tag ID (4 octets) |
+---------------------------------------+
| MPLS label (3 octets) |
+---------------------------------------+
For a SRv6 only BGP speaker for an SRv6 Core:
o SRv6-VPN SID TLV MAY be advertised with the route.
4.1.1. EVPN Route Type-1(Per ES AD)
Where:
o BGP next-hop: IPv6 address of an egress PE
o Ethernet Tag ID: all FFFF's
o MPLS Label: always set to zero value
o Extended Community: Per ES AD, ESI label extended community
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SRv6-VPN TLV MAY be advertised along with the route advertisement and
the behavior of the SRv6-VPN SID is entirely up to the originator of
the advertisement. In practice, the behavior would likely be
Arg.FE2.
4.1.2. Prefix Type-1(Per EVI/ES AD)
Where:
o BGP next-hop: IPv6 address of an egress PE
o Ethernet Tag ID: non-zero for VLAN aware bridging, EVPN VPWS and
FXC
o MPLS Label: Implicit-Null
SRv6-VPN TLV MAY be advertised along with the route advertisement and
the behavior of the SRv6-VPN SID is entirely up to the originator of
the advertisement. In practice, the behavior would likely be
END.DX2, END.DX2V or END.DT2U.
4.2. MAC/IP Advertisement Route(Type-2) with SRv6 Core
EVPN route type-2 is used to advertise unicast traffic MAC+IP address
reachability through MP-BGP to all other PEs in a given EVPN
instance.
A MAC/IP Advertisement route type is encoded as follows for SRv6
Core:
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+---------------------------------------+
| RD (8 octets) |
+---------------------------------------+
|Ethernet Segment Identifier (10 octets)|
+---------------------------------------+
| Ethernet Tag ID (4 octets) |
+---------------------------------------+
| MAC Address Length (1 octet) |
+---------------------------------------+
| MAC Address (6 octets) |
+---------------------------------------+
| IP Address Length (1 octet) |
+---------------------------------------+
| IP Address (0, 4, or 16 octets) |
+---------------------------------------+
| MPLS Label1 (3 octets) |
+---------------------------------------+
| MPLS Label2 (0 or 3 octets) |
+---------------------------------------+
where:
o BGP next-hop: IPv6 address of an egress PE
o MPLS Label1: Implicit-null
o MPLS Label2: Implicit-null
SRv6-VPN SID TLV MAY be advertised. The behavior of the SRv6-VPN SID
is entirely up to the originator of the advertisement. In practice,
the behavior of the SRv6 SID is as follows:
o END.DX2, END.DT2U (Layer 2 portion of the route)
o END.DT6/4 or END.DX6/4 (Layer 3 portion of the route)
Described below are different types of Type-2 advertisements.
o MAC/IP Advertisement Route(Type-2) with MAC Only
* BGP next-hop: IPv6 address of egress PE
* MPLS Label1: Implicit-null
* MPLS Label2: Implicit-null
* SRv6-VPN SID TLV MAY encode END.DX2 or END.DT2U behavior
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o MAC/IP Advertisement Route(Type-2) with MAC+IP
* BGP next-hop: IPv6 address of egress PE
* MPLS Label1: Implicit-Null
* MPLS Label2: Implicit-Null
* SRv6-VPN SID TLV MAY encode Layer2 END.DX2 or END.DT2U behavior
and Layer3 END.DT6/4 or END.DX6/4 behavior
4.3. Inclusive Multicast Ethernet Tag Route with SRv6 Core
EVPN route Type-3 is used to advertise multicast traffic reachability
information through MP-BGP to all other PEs in a given EVPN instance.
+---------------------------------------+
| RD (8 octets) |
+---------------------------------------+
| Ethernet Tag ID (4 octets) |
+---------------------------------------+
| IP Address Length (1 octet) |
+---------------------------------------+
| Originating Router's IP Address |
| (4 or 16 octets) |
+---------------------------------------+
An Inclusive Multicast Ethernet Tag route type specific EVPN NLRI
consists of the following [RFC7432] where:
o BGP next-hop: IPv6 address of egress PE
o SRv6-VPN TLV MAY encode END.DX2/END.DT2M function.
o BGP Attribute: PMSI Tunnel Attribute[RFC6514] MAY contain MPLS
implicit-null label and Tunnel Type would be similar to defined in
EVPN Type-6 i.e. Ingress replication route.
The format of PMSI Tunnel Attribute attribute is encoded as follows
for an SRv6 Core:
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+---------------------------------------+
| Flag (1 octet) |
+---------------------------------------+
| Tunnel Type (1 octet) |
+---------------------------------------+
| MPLS label (3 octet) |
+---------------------------------------+
| Tunnel Identifier (variable) |
+---------------------------------------+
o Flag: zero value defined per [RFC7432]
o Tunnel Type: defined per [RFC6514]
o MPLS label: Implicit-Null
o Tunnel Identifier: IP address of egress PE
SRv6 SID MAY be encoded as part of the SRv6-VPN SID TLV. The
behavior of the SRv6-VPN SID is entirely up to the originator of the
advertisement. In practice, the behavior of the SRv6 SID is as
follows:
o END.DX2 or END.DT2M function
o The lower 32 bits of the SRv6-VPN SID TLV MAY be all zero's. The
ESI Filtering argument(Arg.FE2) carried along with EVPN Route
Type-1 MAY be merged together by doing a bitwise logical OR to
create a single SID on the ingress PE for Split-horizon and other
filtering mechanisms. Details of filtering mechanisms are
described in[RFC7432]
4.4. Ethernet Segment Route with SRv6 Core
An Ethernet Segment route type specific EVPN NLRI consists of the
following defined in [RFC7432]
+---------------------------------------+
| RD (8 octets) |
+---------------------------------------+
| Ethernet Tag ID (4 octets) |
+---------------------------------------+
| IP Address Length (1 octet) |
+---------------------------------------+
| Originating Router's IP Address |
| (4 or 16 octets) |
+---------------------------------------+
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where:
o BGP next-hop: IPv6 address of egress PE
As oppose as previous route types, SRv6-VPN TLV is NOT advertised
along with the route. The processing of that route has not changed;
it remains as described in [RFC7432].
4.5. IP prefix router(Type-5) with SRv6 Core
EVPN route Type-5 is used to advertise IP address reachability
through MP-BGP to all other PEs in a given EVPN instance. IP address
may include host IP prefix or any specific subnet. EVPN route Type-5
is defined in[I-D.ietf-bess-evpn-prefix-advertisement]
An IP Prefix advertisement is encoded as follows for an SRv6 Core:
+---------------------------------------+
| RD (8 octets) |
+---------------------------------------+
|Ethernet Segment Identifier (10 octets)|
+---------------------------------------+
| Ethernet Tag ID (4 octets) |
+---------------------------------------+
| IP Prefix Length (1 octet) |
+---------------------------------------+
| IP Prefix (4 or 16 octets) |
+---------------------------------------+
| GW IP Address (4 or 16 octets) |
+---------------------------------------+
| MPLS Label (3 octets) |
+---------------------------------------+
o BGP next-hop: IPv6 address of egress PE
o MPLS Label: Implicit-Null
SRv6-VPN SID TLV MAY be advertised. The behavior of the SRv6-VPN SID
is entirely up to the originator of the advertisement. In practice,
the behavior of the SRv6 SID is an End.DT6/4 or End.DX6/4.
4.6. Multicast routes (EVPN Route Type-6, Type-7, Type-8)
These routes do not require any additional SRv6-VPN TLV. As per EVPN
route-type 4, the BGP nexthop is equal to the IPv6 address of egress
PE. More details may be added in future revisions of this document.
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5. Migration from L3 MPLS based Segment Routing to SRv6 Segment Routing
Migration from IPv4 to IPv6 is independent of SRv6 BGP endpoints, and
the selection of which route to use (received via the IPv4 or IPv6
session) is a local configurable decision of the ingress-PE, and is
outside the scope of this document.
Migration from IPv6 MPLS based underlay to an SRv6 underlay with BGP
speakers is achieved with a few simple rules at each BGP speaker.
At Egress-PE
If BGP offers an SRv6-VPN service
Then BGP allocates an SRv6-VPN SID for the VPN service
and adds the BGP SRv6-VPN SID TLV while advertising VPN prefixes.
If BGP offers an MPLS VPN service
Then BGP allocates an MPLS Label for the VPN service and
use it in NLRI as normal for MPLS L3 VPNs.
else MPLS label for VPN service is set to IMPLICIT-NULL.
At Ingress-PE
*Selection of which encapsulation below (SRv6-VPN or MPLS-VPN) is
defined by local BGP policy
If BGP supports SRv6-VPN service, and
receives a BGP SRv6-VPN SID Attribute with an SRv6 SID
Then BGP programs the destination prefix in RIB recursive via
the related SR Policy.
If BGP supports MPLS VPN service, and
the MPLS Label is not Implicit-Null
Then the MPLS label is used as a VPN label and inserted with the
prefix into RIB via the BGP Nexthop.
6. Implementation Status
The SRv6-VPN is available for SRv6 on various Cisco hardware and
other software platforms. An end-to-end integration of SRv6 L3VPN,
SRv6 Traffic-Engineering and Service Chaining. All of that with
data-plane interoperability across different implementations [1]:
o Three Cisco Hardware-forwarding platforms: ASR 1K, ASR 9k and NCS
5500
o Huawei network operating system
o Two Cisco network operating systems: IOS XE and IOS XR
o Barefoot Networks Tofino on OCP Wedge-100BF
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o Linux Kernel officially upstreamed in 4.10
o Fd.io
7. Error Handling of BGP SRv6 SID Updates
The SRv6-VPN SID TLV is considered malformed, if the length of the
field SRv6 SID Information is not a multiple of 18.
If the SRv6-VPN SID TLV within the received Prefix-SID attribute is
malformed, consider the entire Prefix-SID attribute as malformed,
discard it and not propagate it further to other peers i.e. use the
-attribute discard- action specified in [RFC7606] an error MAY be
logged for further analysis.
The SRv6-VPN SID TLV is not considered to be malformed in the
following cases. The rest of the Prefix-SID attribute MUST be
processed normally. An error MAY be logged for further analysis.
o The length of the TLV is 0 or 1: Ignore the TLV but store and
propagate it further to other peers.
o The SID Type is unrecognized: all unrecognized SID Types must be
stored locally and propagated further to other peers. It is a
matter of local implementation whether to use locally any
recognized SID Types that may be present in the TLV along with the
unrecognized Types.
In addition, the following rules apply for processing NLRIs received
with Prefix-SID attribute containing SRv6-VPN SID TLV:
o If the TLV is advertised by a CE peer, the receiving PE may
discard it before advertising the route to its PE peers.
o If the received NLRI has neither a valid SRv6-VPN SID nor a valid
MPLS label as specified in [RFC4659][RFC5549][RFC7432][RFC4364] ,
the NLRI MUST be considered unreachable i.e. apply the -treat as
withdraw- action specified in [RFC7606].
8. IANA Considerations
This document defines a new TLV, SRv6-VPN SID, within Prefix-SID
attribute. A new Type, is requested in the BGP Prefix-SID TLV Types
registry and is assigned to SRv6-VPN SID TLV defined in this
document.
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9. Security Considerations
This document introduces no new security considerations beyond those
already specified in [RFC4271] and [RFC8277].
10. Conclusions
This document proposes extensions to the BGP to allow advertising
certain attributes and functionalities related to SRv6.
11. References
11.1. Normative References
[I-D.filsfils-spring-segment-routing-policy]
Filsfils, C., Sivabalan, S., Hegde, S.,
daniel.voyer@bell.ca, d., Lin, S., bogdanov@google.com,
b., Krol, P., Horneffer, M., Steinberg, D., Decraene, B.,
Litkowski, S., Mattes, P., Ali, Z., Talaulikar, K., Liste,
J., Clad, F., and K. Raza, "Segment Routing Policy
Architecture", draft-filsfils-spring-segment-routing-
policy-06 (work in progress), May 2018.
[I-D.filsfils-spring-srv6-network-programming]
Filsfils, C., Li, Z., Leddy, J., daniel.voyer@bell.ca, d.,
daniel.bernier@bell.ca, d., Steinberg, D., Raszuk, R.,
Matsushima, S., Lebrun, D., Decraene, B., Peirens, B.,
Salsano, S., Naik, G., Elmalky, H., Jonnalagadda, P., and
M. Sharif, "SRv6 Network Programming", draft-filsfils-
spring-srv6-network-programming-04 (work in progress),
March 2018.
[]
Previdi, S., Filsfils, C., Leddy, J., Matsushima, S., and
d. daniel.voyer@bell.ca, "IPv6 Segment Routing Header
(SRH)", draft-ietf-6man-segment-routing-header-13 (work in
progress), May 2018.
[RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", RFC 2460, DOI 10.17487/RFC2460,
December 1998, <https://www.rfc-editor.org/info/rfc2460>.
[RFC4456] Bates, T., Chen, E., and R. Chandra, "BGP Route
Reflection: An Alternative to Full Mesh Internal BGP
(IBGP)", RFC 4456, DOI 10.17487/RFC4456, April 2006,
<https://www.rfc-editor.org/info/rfc4456>.
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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>.
[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>.
[RFC7606] Chen, E., Ed., Scudder, J., Ed., Mohapatra, P., and K.
Patel, "Revised Error Handling for BGP UPDATE Messages",
RFC 7606, DOI 10.17487/RFC7606, August 2015,
<https://www.rfc-editor.org/info/rfc7606>.
[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>.
11.2. Informative References
[I-D.ietf-bess-evpn-prefix-advertisement]
Rabadan, J., Henderickx, W., Drake, J., Lin, W., and A.
Sajassi, "IP Prefix Advertisement in EVPN", draft-ietf-
bess-evpn-prefix-advertisement-11 (work in progress), May
2018.
[I-D.ietf-idr-bgp-prefix-sid]
Previdi, S., Filsfils, C., Lindem, A., Sreekantiah, A.,
and H. Gredler, "Segment Routing Prefix SID extensions for
BGP", draft-ietf-idr-bgp-prefix-sid-26 (work in progress),
June 2018.
[I-D.ietf-isis-segment-routing-extensions]
Previdi, S., Ginsberg, L., Filsfils, C., Bashandy, A.,
Gredler, H., Litkowski, S., Decraene, B., and J. Tantsura,
"IS-IS Extensions for Segment Routing", draft-ietf-isis-
segment-routing-extensions-18 (work in progress), June
2018.
[I-D.ietf-spring-segment-routing]
Filsfils, C., Previdi, S., Ginsberg, L., Decraene, B.,
Litkowski, S., and R. Shakir, "Segment Routing
Architecture", draft-ietf-spring-segment-routing-15 (work
in progress), January 2018.
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[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>.
[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>.
[RFC4659] De Clercq, J., Ooms, D., Carugi, M., and F. Le Faucheur,
"BGP-MPLS IP Virtual Private Network (VPN) Extension for
IPv6 VPN", RFC 4659, DOI 10.17487/RFC4659, September 2006,
<https://www.rfc-editor.org/info/rfc4659>.
[RFC5549] Le Faucheur, F. and E. Rosen, "Advertising IPv4 Network
Layer Reachability Information with an IPv6 Next Hop",
RFC 5549, DOI 10.17487/RFC5549, May 2009,
<https://www.rfc-editor.org/info/rfc5549>.
11.3. URIs
[1] http://www.segment-routing.net
Appendix A. Acknowledgements
The authors would like to thank Shyam Sethuram for comments and
discussion of TLV processing and validation.
Appendix B. Contributors
Bart Peirens
Proximus
Belgium
Email: bart.peirens@proximus.com
Authors' Addresses
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Gaurav Dawra (editor)
LinkedIn
USA
Email: gdawra.ietf@gmail.com
Clarence Filsfils
Cisco Systems
Belgium
Email: cfilsfil@cisco.com
Darren Dukes
Cisco Systems
Canada
Email: ddukes@cisco.com
Patrice Brissette
Cisco Systems
Canada
Email: pbrisset@cisco.com
Pablo Camarilo
Cisco Systems
Spain
Email: pcamaril@cisco.com
Jonn Leddy
Comcast
USA
Email: john_leddy@cable.comcast.com
Daniel Voyer
Bell Canada
Canada
Email: daniel.voyer@bell.ca
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Daniel Bernier
Bell Canada
Canada
Email: daniel.bernier@bell.ca
Dirk Steinberg
Steinberg Consulting
Germany
Email: dws@steinberg.net
Robert Raszuk
Bloomberg LP
USA
Email: robert@raszuk.net
Bruno Decraene
Orange
France
Email: bruno.decraene@orange.com
Satoru Matsushima
SoftBank
1-9-1,Higashi-Shimbashi,Minato-Ku
Japan 105-7322
Email: satoru.matsushima@g.softbank.co.jp
Shunwan Zhuang
Huawei Technologies
China
Email: zhuangshunwan@huawei.com
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