SPRING C. Filsfils, Ed.
Internet-Draft P. Camarillo, Ed.
Intended status: Standards Track Cisco Systems, Inc.
Expires: August 26, 2020 J. Leddy
Individual Contributor
D. Voyer
Bell Canada
S. Matsushima
SoftBank
Z. Li
Huawei Technologies
February 23, 2020
SRv6 Network Programming
draft-ietf-spring-srv6-network-programming-10
Abstract
The SRv6 Network Programming framework enables a network operator or
an application to specify a packet packet processing program by
encoding a sequence of instructions in the IPv6 packet header.
Each instruction is implemented on one or several nodes in the
network and identified by an SRv6 Segment Identifier in the packet.
This document defines the SRv6 Network Programming concept and
specifies the base set of SRv6 behaviors that enables the creation of
interoperable overlays with underlay optimization (Service Level
Agreements).
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 August 26, 2020.
Filsfils, et al. Expires August 26, 2020 [Page 1]
Internet-Draft SRv6 Network Programming February 2020
Copyright Notice
Copyright (c) 2020 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 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 . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.1. Requirements Language . . . . . . . . . . . . . . . . . . 5
3. SRv6 SID . . . . . . . . . . . . . . . . . . . . . . . . . . 6
3.1. SID Format . . . . . . . . . . . . . . . . . . . . . . . 6
3.2. SID Reachability . . . . . . . . . . . . . . . . . . . . 7
4. SR Endpoint Behaviors . . . . . . . . . . . . . . . . . . . . 8
4.1. End: Endpoint . . . . . . . . . . . . . . . . . . . . . . 9
4.1.1. Upper-Layer Header . . . . . . . . . . . . . . . . . 9
4.2. End.X: Layer-3 Cross-Connect . . . . . . . . . . . . . . 10
4.3. End.T: Specific IPv6 Table Lookup . . . . . . . . . . . . 11
4.4. End.DX6: Decapsulation and IPv6 Cross-Connect . . . . . . 11
4.5. End.DX4: Decapsulation and IPv4 Cross-Connect . . . . . . 12
4.6. End.DT6: Decapsulation and Specific IPv6 Table Lookup . . 13
4.7. End.DT4: Decapsulation and Specific IPv4 Table Lookup . . 14
4.8. End.DT46: Decapsulation and Specific IP Table Lookup . . 15
4.9. End.DX2: Decapsulation and L2 Cross-Connect . . . . . . . 16
4.10. End.DX2V: Decapsulation and VLAN L2 Table Lookup . . . . 17
4.11. End.DT2U: Decapsulation and Unicast MAC L2 Table Lookup . 17
4.12. End.DT2M: Decapsulation and L2 Table Flooding . . . . . . 18
4.13. End.B6.Encaps: Endpoint Bound to an SRv6 Policy w/ Encaps 19
4.14. End.B6.Encaps.Red: End.B6.Encaps with Reduced SRH . . . . 21
4.15. End.BM: Endpoint Bound to an SR-MPLS Policy . . . . . . . 21
4.16. Flavors . . . . . . . . . . . . . . . . . . . . . . . . . 22
4.16.1. PSP: Penultimate Segment Pop of the SRH . . . . . . 22
4.16.2. USP: Ultimate Segment Pop of the SRH . . . . . . . . 23
4.16.3. USD: Ultimate Segment Decapsulation . . . . . . . . 23
5. SR Policy Headend Behaviors . . . . . . . . . . . . . . . . . 24
5.1. H.Encaps: SR Headend with Encapsulation in an SRv6 Policy 25
5.2. H.Encaps.Red: H.Encaps with Reduced Encapsulation . . . . 25
5.3. H.Encaps.L2: H.Encaps Applied to Received L2 Frames . . . 26
Filsfils, et al. Expires August 26, 2020 [Page 2]
Internet-Draft SRv6 Network Programming February 2020
5.4. H.Encaps.L2.Red: H.Encaps.Red Applied to Received L2
frames . . . . . . . . . . . . . . . . . . . . . . . . . 26
6. Operation . . . . . . . . . . . . . . . . . . . . . . . . . . 27
6.1. Counters . . . . . . . . . . . . . . . . . . . . . . . . 27
6.2. Flow-based Hash Computation . . . . . . . . . . . . . . . 27
7. Security Considerations . . . . . . . . . . . . . . . . . . . 27
8. Control Plane . . . . . . . . . . . . . . . . . . . . . . . . 27
8.1. IGP . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
8.2. BGP-LS . . . . . . . . . . . . . . . . . . . . . . . . . 28
8.3. BGP IP/VPN/EVPN . . . . . . . . . . . . . . . . . . . . . 28
8.4. Summary . . . . . . . . . . . . . . . . . . . . . . . . . 29
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 30
9.1. Ethernet Next Header Type . . . . . . . . . . . . . . . . 30
9.2. SRv6 Endpoint Behaviors Registry . . . . . . . . . . . . 30
9.2.1. Initial Registrations . . . . . . . . . . . . . . . . 31
10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 32
11. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 32
12. References . . . . . . . . . . . . . . . . . . . . . . . . . 35
12.1. Normative References . . . . . . . . . . . . . . . . . . 35
12.2. Informative References . . . . . . . . . . . . . . . . . 36
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 37
Filsfils, et al. Expires August 26, 2020 [Page 3]
Internet-Draft SRv6 Network Programming February 2020
1. Introduction
Segment Routing [RFC8402] leverages the source routing paradigm. An
ingress node steers a packet through an ordered list of instructions,
called segments. Each one of these instructions represents a
function to be called at a specific location in the network. A
function is locally defined on the node where it is executed and may
range from simply moving forward in the segment list to any complex
user-defined behavior. Network programming combines segment routing
functions, both simple and complex, to achieve a networking objective
that goes beyond mere packet routing.
This document defines the SRv6 Network Programming concept and
specifies the main segment routing behaviors to enable the creation
of interoperable overlays with underlay optimization (Service Level
Agreement).
The companion document
[I-D.filsfils-spring-srv6-net-pgm-illustration] illustrates the
concepts defined in this document.
Familiarity with the Segment Routing Header
[I-D.ietf-6man-segment-routing-header] is expected.
2. Terminology
The following terms used within this document are defined in
[RFC8402]: Segment Routing, SR Domain, Segment ID (SID), SRv6, SRv6
SID, Active Segment, SR Policy, Prefix SID and Adjacency SID.
The following terms used within this document are defined in
[I-D.ietf-6man-segment-routing-header]: SRH, SR Source Node, Transit
Node, SR Segment Endpoint Node and Reduced SRH.
NH: Next-header field of the IPv6 header[RFC8200]. NH=SRH means that
the next-header of the IPv6 header is Routing Header for IPv6(43)
with the Type field set to 4.
SL: The Segments Left field of the SRH
FIB: Forwarding Information Base. A FIB lookup is a lookup in the
forwarding table.
SA: Source Address
DA: Destination Address
Filsfils, et al. Expires August 26, 2020 [Page 4]
Internet-Draft SRv6 Network Programming February 2020
SRv6 SID function: The function part of the SID is an opaque
identification of a local behavior bound to the SID. It is formally
defined in Section 3.1 of this document.
SRv6 segment endpoint behavior: A packet processing behavior executed
at an SRv6 segment endpoint. Section 4 of this document defines SRv6
segment endpoint behaviors related to traffic-engineering and overlay
use-cases. Other behaviors (e.g. service programming) are outside
the scope of this document.
An SR Policy is resolved to a SID list. 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:
- Source Address is SA, Destination Address is DA, and next-header is
SRH
- SRH with SID list <S1, S2, S3> with Segments Left = 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.
- The payload of the packet is omitted.
SRH[n]: A shorter representation of Segment List[n], as defined in
[I-D.ietf-6man-segment-routing-header].
2.1. 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.
Filsfils, et al. Expires August 26, 2020 [Page 5]
Internet-Draft SRv6 Network Programming February 2020
3. SRv6 SID
RFC8402 defines an SRv6 Segment Identifier as an IPv6 address
explicitly associated with the segment.
When an SRv6 SID is in the Destination Address field of an IPv6
header of a packet, it is routed through an IPv6 network as an IPv6
address.
Its processing is defined in [I-D.ietf-6man-segment-routing-header]
section 4.3 and reproduced here as a reminder.
Without constraining the details of an implementation, the SR
segment endpoint node creates Forwarding Information Base (FIB)
entries for its local SIDs.
When an SRv6-capable node receives an IPv6 packet, it performs a
longest-prefix-match lookup on the packets destination address.
This lookup can return any of the following:
- A FIB entry that represents a locally instantiated SRv6 SID
- A FIB entry that represents a local interface, not locally
instantiated as an SRv6 SID
- A FIB entry that represents a non-local route
- No Match
This document formally defines behaviors and parameters for SRv6
SIDs.
3.1. SID Format
This document defines an SRv6 SID as consisting 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). L, the locator length, is flexible, and an operator
is free to use the locator length of their choice. F and A may be
any value as long as L+F+A <= 128. When L+F+A is less than 128 then
the reminder of the SID MUST be zero.
A locator may be represented as B:N where B is the SRv6 SID block
(IPv6 subnet allocated for SRv6 SIDs by the operator) and N is the
identifier of the parent node instantiating the SID.
When the LOC part of the SRv6 SIDs is routable, it leads to the node
which instantiates the SID.
Filsfils, et al. Expires August 26, 2020 [Page 6]
Internet-Draft SRv6 Network Programming February 2020
The FUNCT is an opaque identification of a local behavior bound to
the SID.
The term "function" refers to the bit-string in the SRv6 SID. The
term "behavior" identifies the behavior bound to the SID. The
behaviors are defined in Section 4 of this document.
An SRv6 endpoint behavior MAY require additional information for its
processing (e.g. related to the flow or service). This information
may be encoded in the ARG bits of the SID.
In such a case, the semantics and format of the ARG bits are defined
as part of the SRv6 endpoint behavior specification.
The ARG value of a routed SID SHOULD remain constant among packets in
a given flow. Varying ARG values among packets in a flow may result
in different ECMP hashing and cause re-ordering.
3.2. SID Reachability
Most often, the node N would advertise IPv6 prefix(es) matching the
LOC parts covering its SIDs or shorter-mask prefix. The distribution
of these advertisements and calculation of their reachability are
routing protocol specific aspects that are outside the scope of this
document.
An SRv6 SID is said to be routed if its SID belongs to an IPv6 prefix
advertised via a routing protocol. An SRv6 SID that does not fulfill
this condition is non-routed.
Let's provide a classic illustration:
Node N is configured explicitly with two SIDs: 2001:DB8:B:1:100:: and
2001:DB8:B:2:101::.
The network learns about a path to 2001:DB8:B:1::/64 via the IGP and
hence a packet destined to 2001:DB8:B:1:100:: would be routed up to
N. The network does not learn about a path to 2001:DB8:B:2::/64 via
the IGP and hence a packet destined to 2001:DB8:B:2:101:: would not
be routed up to N.
A packet could be steered to a non-routed SID 2001:DB8:B:2:101:: by
using a SID list <...,2001:DB8:B:1:100::,2001:DB8:B:2:101::,...>
where the non-routed SID is preceded by a routed SID to the same
node. Routed and non-routed SRv6 SIDs are the SRv6 instantiation of
global and local segments, respectively [RFC8402].
Filsfils, et al. Expires August 26, 2020 [Page 7]
Internet-Draft SRv6 Network Programming February 2020
4. SR Endpoint Behaviors
Each FIB entry indicates the behavior associated with a SID instance
and its parameters.
Following is a set of well-known behaviors that can be associated
with a SID.
End Endpoint function
The SRv6 instantiation of a prefix SID [RFC8402]
End.X Endpoint with Layer-3 cross-connect
The SRv6 instantiation of a Adj SID [RFC8402]
End.T Endpoint with specific IPv6 table lookup
End.DX6 Endpoint with decapsulation and IPv6 cross-connect
e.g. IPv6-L3VPN (equivalent to per-CE VPN label)
End.DX4 Endpoint with decaps and IPv4 cross-connect
e.g. IPv4-L3VPN (equivalent to per-CE VPN label)
End.DT6 Endpoint with decapsulation and IPv6 table lookup
e.g. IPv6-L3VPN (equivalent to per-VRF VPN label)
End.DT4 Endpoint with decapsulation and IPv4 table lookup
e.g. IPv4-L3VPN (equivalent to per-VRF VPN label)
End.DT46 Endpoint with decapsulation and IP table lookup
e.g. IP-L3VPN (equivalent to per-VRF VPN label)
End.DX2 Endpoint with decapsulation and L2 cross-connect
e.g. L2VPN use-case
End.DX2V Endpoint with decaps and VLAN L2 table lookup
e.g. EVPN Flexible cross-connect use-case
End.DT2U Endpoint with decaps and unicast MAC L2table lookup
e.g. EVPN Bridging unicast use-case
End.DT2M Endpoint with decapsulation and L2 table flooding
e.g. EVPN Bridging BUM use-case with ESI filtering
End.B6.Encaps Endpoint bound to an SRv6 policy with encapsulation
SRv6 instantiation of a Binding SID
End.B6.Encaps.RED End.B6.Encaps with reduced SRH
SRv6 instantiation of a Binding SID
End.BM Endpoint bound to an SR-MPLS Policy
SRv6 instantiation of an SR-MPLS Binding SID
The list is not exhaustive. In practice, any function can be
attached to a local SID: e.g. a node N can bind a SID to a local VM
or container which can apply any complex processing on the packet.
The following sub-sections detail the behaviors, introduced in this
document, that a node (N) binds to a SID (S).
Section 4.16 defines flavors of some of these behaviors.
Filsfils, et al. Expires August 26, 2020 [Page 8]
Internet-Draft SRv6 Network Programming February 2020
4.1. End: Endpoint
The Endpoint behavior ("End" for short) is the most basic behavior.
It is the instantiation of a Prefix-SID [RFC8402].
When N receives a packet whose IPv6 DA is S and S is a local End SID,
N does:
S01. When an SRH is processed {
S02. If (Segments Left == 0) {
S03. Send an ICMP Parameter Problem message to the Source Address
Code 4 (SR Upper-layer Header Error),
Pointer set to the offset of the upper-layer header.
Interrupt packet processing and discard the packet.
S04. }
S05. If (IPv6 Hop Limit <= 1) {
S06. Send an ICMP Time Exceeded message to the Source Address,
Code 0 (Hop limit exceeded in transit),
Interrupt packet processing and discard the packet.
S07. }
S08. max_LE = (Hdr Ext Len / 2) - 1
S09. If ((Last Entry > max_LE) or (Segments Left > Last Entry+1)) {
S10. 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.
S11. }
S12. Decrement Hop Limit by 1
S13. Decrement Segments Left by 1
S14. Update IPv6 DA with Segment List[Segments Left]
S15. Submit the packet to the egress IPv6 FIB lookup and
transmission to the new destination
S16. }
Notes:
The End behavior operates on the same FIB table (i.e. VRF, L3 relay
id) associated to the packet. Hence the FIB lookup on line S15 is
done in the same FIB table as the ingress interface.
4.1.1. Upper-Layer Header
When processing the Upper-layer Header of a packet matching a FIB
entry locally instantiated as an SRv6 End SID, if Upper-layer Header
processing is allowed by local configuration (e.g. ICMPv6), then
process the upper-layer header. Otherwise, send an ICMP parameter
problem message to the Source Address and discard the packet. Error
Filsfils, et al. Expires August 26, 2020 [Page 9]
Internet-Draft SRv6 Network Programming February 2020
code 4 (SR Upper-layer Header Error) and Pointer set to the offset of
the upper-layer header.
4.2. End.X: Layer-3 Cross-Connect
The "Endpoint with cross-connect to an array of layer-3 adjacencies"
behavior (End.X for short) is a variant of the End behavior.
It is the SRv6 instantiation of an Adjacency-SID [RFC8402] and it is
required to express any traffic-engineering policy.
An instance of the End.X behavior is associated with a set, J, of one
or more Layer-3 adjacencies.
When N receives a packet destined to S and S is a local End.X SID,
the line S15 from the End processing is replaced by the following:
S15. Submit the packet to the IPv6 module for transmission
to the new destination via a member of J
Notes:
S15. If the set J contains several L3 adjacencies, then one element
of the set is selected based on a hash of the packet's header
Section 6.2.
If a node N has 30 outgoing interfaces to 30 neighbors, usually the
operator would explicitly instantiate 30 End.X SIDs at N: one per
layer-3 adjacency to a neighbor. Potentially, more End.X could be
explicitly defined (groups of layer-3 adjacencies to the same
neighbor or to different neighbors).
Note that if N has an outgoing interface bundle I to a neighbor Q
made of 10 member links, N may allocate up to 11 End.X local SIDs:
one for the bundle(LAG) itself and then up to one for each Layer-2
member link.
When the End.X behavior is associated with a BGP Next-Hop, it is the
SRv6 instantiation of the BGP Peering Segments [RFC8402].
Filsfils, et al. Expires August 26, 2020 [Page 10]
Internet-Draft SRv6 Network Programming February 2020
4.3. End.T: Specific IPv6 Table Lookup
The "Endpoint with specific IPv6 table lookup" behavior (End.T for
short) is a variant of the End behavior.
The End.T behavior is used for multi-table operation in the core.
For this reason, an instance of the End.T behavior is associated with
an IPv6 FIB table T.
When N receives a packet destined to S and S is a local End.T SID,
the line S15 from the End processing is replaced by the following:
S15.1. Set the packet's associated FIB table to T
S15.2. Submit the packet to the egress IPv6 FIB lookup and
transmission to the new destination
4.4. End.DX6: Decapsulation and IPv6 Cross-Connect
The "Endpoint with decapsulation and cross-connect to an array of
IPv6 adjacencies" behavior (End.DX6 for short) is a variant of the
End.X behavior.
One of the applications of the End.DX6 behavior is the L3VPNv6 use-
case where a FIB lookup in a specific tenant table at the egress PE
is not required. This is equivalent to the per-CE VPN label in MPLS
[RFC4364].
The End.DX6 SID MUST be the last segment in a SR Policy, and it is
associated with one or more L3 IPv6 adjacencies J.
When N receives a packet destined to S and S is a local End.DX6 SID,
N does the following processing:
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. }
Filsfils, et al. Expires August 26, 2020 [Page 11]
Internet-Draft SRv6 Network Programming February 2020
When processing the Upper-layer header of a packet matching a FIB
entry locally instantiated as an SRv6 End.DX6 SID, the following is
done:
S01. If (Upper-Layer Header type != 41) {
S02. Process as per Section 4.1.1
S03. }
S04. Remove the outer IPv6 Header with all its extension headers
S05. Forward the exposed IPv6 packet to the L3 adjacency J
Notes:
S01. 41 refers to IPv6 encapsulation as defined by IANA allocation
for Internet Protocol Numbers.
S05. If the End.DX6 SID is bound to an array of L3 adjacencies, then
one entry of the array is selected based on the hash of the packet's
header Section 6.2.
4.5. End.DX4: Decapsulation and IPv4 Cross-Connect
The "Endpoint with decapsulation and cross-connect to an array of
IPv4 adjacencies" behavior (End.DX4 for short) is a variant of the
End.X behavior.
One of the applications of the End.DX4 behavior is the L3VPNv4 use-
case where a FIB lookup in a specific tenant table at the egress PE
is not required. This is equivalent to the per-CE VPN label in MPLS
[RFC4364].
The End.DX4 SID MUST be the last segment in a SR Policy, and it is
associated with one or more L3 IPv4 adjacencies J.
When N receives a packet destined to S and S is a local End.DX4 SID,
N does the following processing:
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. }
Filsfils, et al. Expires August 26, 2020 [Page 12]
Internet-Draft SRv6 Network Programming February 2020
When processing the Upper-layer header of a packet matching a FIB
entry locally instantiated as an SRv6 End.DX4 SID, the following is
done:
S01. If (Upper-Layer Header type != 4) {
S02. Process as per Section 4.1.1
S03. }
S04. Remove the outer IPv6 Header with all its extension headers
S05. Forward the exposed IPv4 packet to the L3 adjacency J
Notes:
S01. 4 refers to IPv4 encapsulation as defined by IANA allocation for
Internet Protocol Numbers
S05. If the End.DX4 SID is bound to an array of L3 adjacencies, then
one entry of the array is selected based on the hash of the packet's
header Section 6.2.
4.6. End.DT6: Decapsulation and Specific IPv6 Table Lookup
The "Endpoint with decapsulation and specific IPv6 table lookup"
behavior (End.DT6 for short) is a variant of the End.T behavior.
One of the applications of the End.DT6 behavior is the L3VPNv6 use-
case where a FIB lookup in a specific tenant table at the egress PE
is required. This is equivalent to the per-VRF VPN label in MPLS
[RFC4364].
Note that an End.DT6 may be defined for the main IPv6 table in which
case and End.DT6 supports the equivalent of an IPv6inIPv6
decapsulation (without VPN/tenant implication).
The End.DT6 SID MUST be the last segment in a SR Policy, and a SID
instance is associated with an IPv6 FIB table T.
When N receives a packet destined to S and S is a local End.DT6 SID,
N does the following processing:
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. }
Filsfils, et al. Expires August 26, 2020 [Page 13]
Internet-Draft SRv6 Network Programming February 2020
When processing the Upper-layer header of a packet matching a FIB
entry locally instantiated as an SRv6 End.DT6 SID, N does the
following:
S01. If (Upper-Layer Header type != 41) {
S02. Process as per Section 4.1.1
S03. }
S04. Remove the outer IPv6 Header with all its extension headers
S05. Set the packet's associated FIB table to T
S06. Submit the packet to the egress IPv6 FIB lookup and
transmission to the new destination
4.7. End.DT4: Decapsulation and Specific IPv4 Table Lookup
The "Endpoint with decapsulation and specific IPv4 table lookup"
behavior (End.DT4 for short) is a variant of the End behavior.
One of the applications of the End.DT4 behavior is the L3VPNv4 use-
case where a FIB lookup in a specific tenant table at the egress PE
is required. This is equivalent to the per-VRF VPN label in MPLS
[RFC4364].
Note that an End.DT4 may be defined for the main IPv4 table in which
case an End.DT4 supports the equivalent of an IPv4inIPv6
decapsulation (without VPN/tenant implication).
The End.DT4 SID MUST be the last segment in a SR Policy, and a SID
instance is associated with an IPv4 FIB table T.
When N receives a packet destined to S and S is a local End.DT4 SID,
N does the following processing:
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 SRv6 End.DT4 SID, N does the
following:
Filsfils, et al. Expires August 26, 2020 [Page 14]
Internet-Draft SRv6 Network Programming February 2020
S01. If (Upper-Layer Header type != 4) {
S02. Process as per Section 4.1.1
S03. }
S04. Remove the outer IPv6 Header with all its extension headers
S05. Set the packet's associated FIB table to T
S06. Submit the packet to the egress IPv4 FIB lookup and
transmission to the new destination
4.8. End.DT46: Decapsulation and Specific IP Table Lookup
The "Endpoint with decapsulation and specific IP table lookup"
behavior (End.DT46 for short) is a variant of the End.DT4 and End.DT6
behavior.
One of the applications of the End.DT46 behavior is the L3VPN use-
case where a FIB lookup in a specific IP tenant table at the egress
PE is required. This is equivalent to single per-VRF VPN label (for
IPv4 and IPv6) in MPLS[RFC4364].
Note that an End.DT46 may be defined for the main IP table in which
case an End.DT46 supports the equivalent of an IPinIPv6
decapsulation(without VPN/tenant implication).
The End.DT46 SID MUST be the last segment in a SR Policy, and a SID
instance is associated with an IPv4 FIB table T4 and an IPv6 FIB
table T6.
When N receives a packet destined to S and S is a local End.DT46 SID,
N does the following processing:
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 SRv6 End.DT46 SID, N does the
following:
Filsfils, et al. Expires August 26, 2020 [Page 15]
Internet-Draft SRv6 Network Programming February 2020
S01. If (Upper-layer Header type == 4) {
S02. Remove the outer IPv6 Header with all its extension headers
S03. Set the packet's associated FIB table to T4
S04. Submit the packet to the egress IPv4 FIB lookup and
transmission to the new destination
S05. } Else if (Upper-layer Header type == 41) {
S06. Remove the outer IPv6 Header with all its extension headers
S07. Set the packet's associated FIB table to T6
S08. Submit the packet to the egress IPv6 FIB lookup and
transmission to the new destination
S09. } Else {
S10. Process as per Section 4.1.1
S11. }
4.9. End.DX2: Decapsulation and L2 Cross-Connect
The "Endpoint with decapsulation and Layer-2 cross-connect to an
outgoing L2 interface (OIF)" (End.DX2 for short) is a variant of the
endpoint behavior.
One of the applications of the End.DX2 behavior is the L2VPN/
EVPN[RFC7432] VPWS use-case.
The End.DX2 SID MUST be the last segment in a SR Policy, and it is
associated with one outgoing interface I.
When N receives a packet destined to S and S is a local End.DX2 SID,
N does:
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 SRv6 End.DX2 SID, the following is
done:
Filsfils, et al. Expires August 26, 2020 [Page 16]
Internet-Draft SRv6 Network Programming February 2020
S01. If (Upper-Layer Header type != 143) {
S02. Process as per Section 4.1.1
S03. }
S04. Remove the outer IPv6 Header with all its extension headers and
forward the Ethernet frame to the OIF I.
Notes:
S04. An End.DX2 behavior could be customized to expect a specific
IEEE header (e.g. VLAN tag) and rewrite the egress IEEE header
before forwarding on the outgoing interface.
4.10. End.DX2V: Decapsulation and VLAN L2 Table Lookup
The "Endpoint with decapsulation and specific VLAN table lookup"
behavior (End.DX2V for short) is a variant of the End.DX2 behavior.
One of the applications of the End.DX2V behavior is the EVPN Flexible
cross-connect use-case. The End.DX2V behavior is used to perform a
lookup of the Ethernet frame VLANs in a particular L2 table. Any SID
instance of the End.DX2V behavior is associated with an L2 Table T.
When N receives a packet whose IPv6 DA is S and S is a local End.DX2
SID, the processing is identical to the End.DX2 behavior except for
the Upper-layer header processing which is modified as follows:
S04. Remove the outer IPv6 Header with all its extension headers,
lookup the exposed VLANs in L2 table T, and forward
via the matched table entry.
Notes:
An End.DX2V behavior could be customized to expect a specific VLAN
format and rewrite the egress VLAN header before forwarding on the
outgoing interface.
4.11. End.DT2U: Decapsulation and Unicast MAC L2 Table Lookup
The "Endpoint with decapsulation and specific unicast MAC L2 table
lookup" behavior (End.DT2U for short) is a variant of the End
behavior.
One of the applications of the End.DT2U behavior is the EVPN Bridging
unicast. Any SID instance of the End.DT2U behavior is associated
with an L2 Table T.
Filsfils, et al. Expires August 26, 2020 [Page 17]
Internet-Draft SRv6 Network Programming February 2020
When N receives a packet whose IPv6 DA is S and S is a local End.DT2U
SID, the processing is identical to the End.DX2 behavior except for
the Upper-layer header processing which is as follows:
S01. If (Upper-Layer Header type != 143) {
S02. Process as per Section 4.1.1
S03. }
S04. Remove the IPv6 header and all its extension headers
S05. Learn the exposed MAC Source Address in L2 Table T
S06. Lookup the exposed MAC Destination Address in L2 Table T
S07. If (matched entry in T) {
S08. Forward via the matched table T entry
S09. } Else {
S10. Forward via all L2 OIFs entries in table T
S11. }
Notes:
S05. In EVPN, the learning of the exposed inner MAC SA is done via
the control plane.
4.12. End.DT2M: Decapsulation and L2 Table Flooding
The "Endpoint with decapsulation and specific L2 table flooding"
behavior (End.DT2M for short) is a variant of the End.DT2U behavior.
Two of the applications of the End.DT2M behavior are the EVPN
Bridging BUM with ESI filtering and the EVPN ETREE use-cases.
Any SID instance of this behavior is associated with a L2 table T.
Additionally the behavior MAY take an argument: "Arg.FE2". It is an
argument specific to EVPN ESI filtering and EVPN-ETREE used to
exclude specific OIF (or set of OIFs) from L2 table T flooding.
When N receives a packet whose IPv6 DA is S and S is a local End.DT2M
SID, the processing is identical to the End.DT2M behavior except for
the Upper-layer header processing which is as follows:
S01. If (Upper-Layer Header type != 143) {
S02. Process as per Section 4.1.1
S03. }
S04. Remove the IPv6 header and all its extension headers
S05. Learn the exposed inner MAC Source Address in L2 Table T
S06. Forward via all L2 OIFs excluding the one specified in Arg.FE2
Notes:
Filsfils, et al. Expires August 26, 2020 [Page 18]
Internet-Draft SRv6 Network Programming February 2020
S05. In EVPN, the learning of the exposed inner MAC SA is done via
control plane
Arg.FE2 is encoded in the SID as an (k*x)-bit value. These bits
represent a list of up to k OIFs, each identified with an x-bit
value. Values k and x are defined on a per End.DT2M SID basis. The
interface identifier 0 indicates an empty entry in the interface
list.
4.13. End.B6.Encaps: Endpoint Bound to an SRv6 Policy w/ Encaps
This is a variation of the End behavior.
One of its applications is to express scalable traffic-engineering
policies across multiple domains. It is the one of the SRv6
instantiations of a Binding SID [RFC8402].
An End.B6.Encaps SID is never the last segment in a SID list. Any
SID instantiation is associated with an SR Policy B and a source
address A.
When N receives a packet whose IPv6 DA is S and S is a local
End.B6.Encaps SID, does:
Filsfils, et al. Expires August 26, 2020 [Page 19]
Internet-Draft SRv6 Network Programming February 2020
S01. When an SRH is processed {
S02. If (Segments Left == 0) {
S03. Send an ICMP Parameter Problem message to the Source Address
Code 4 (SR Upper-layer Header Error),
Pointer set to the offset of the upper-layer header.
Interrupt packet processing and discard the packet.
S04. }
S05. If (IPv6 Hop Limit <= 1) {
S06. Send an ICMP Time Exceeded message to the Source Address,
Code 0 (Hop limit exceeded in transit),
Interrupt packet processing and discard the packet.
S07. }
S08. max_LE = (Hdr Ext Len / 2) - 1
S09. If ((Last Entry > max_LE) or (Segments Left > (Last Entry+1)) {
S10. 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.
S11. }
S12. Decrement Hop Limit by 1
S13. Decrement Segments Left by 1
S14. Push a new IPv6 header with its own SRH containing B
S15. Set the outer IPv6 SA to A
S16. Set the outer IPv6 DA to the first SID of B
S17. Set the outer PayloadLength, Traffic Class, FlowLabel and
Next-Header fields
S18. Submit the packet to the egress IPv6 FIB lookup and
transmission to the new destination
S19. }
Notes:
S14. The SRH MAY be omitted when the SRv6 Policy B only contains one
SID and there is no need to use any flag, tag or TLV.
S17. The Payload Length, Traffic Class and Next-Header fields are
set as per [RFC2473]. The Flow Label is computed as per [RFC6437].
When processing the Upper-layer header of a packet matching a FIB
entry locally instantiated as an SRv6 End.B6.Encaps SID, process the
packet as per Section 4.1.1.
Filsfils, et al. Expires August 26, 2020 [Page 20]
Internet-Draft SRv6 Network Programming February 2020
4.14. End.B6.Encaps.Red: End.B6.Encaps with Reduced SRH
This is an optimization of the End.B6.Encaps behavior.
End.B6.Encaps.Red reduces the size of the SRH by one SID by excluding
the first SID in the SRH of the new IPv6 header. Thus the first
segment is only placed in the IPv6 Destination Address of the new
IPv6 header and the packet is forwarded according to it.
The SRH Last Entry field is set as defined in Section 4.1.1 of
[I-D.ietf-6man-segment-routing-header].
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.
4.15. End.BM: Endpoint Bound to an SR-MPLS Policy
The "Endpoint bound to an SR-MPLS Policy" is a variant of the End
behavior.
The End.BM behavior is required to express scalable traffic-
engineering policies across multiple domains where some domains
support the MPLS instantiation of Segment Routing. This is an SRv6
instantiation of an SR-MPLS Binding SID [RFC8402].
An End.BM SID is never the last SID, and any SID instantiation is
associated with an SR-MPLS Policy B.
When N receives a packet whose IPv6 DA is S and S is a local End.BM
SID, does:
Filsfils, et al. Expires August 26, 2020 [Page 21]
Internet-Draft SRv6 Network Programming February 2020
S01. When an SRH is processed {
S02. If (Segments Left == 0) {
S03. Send an ICMP Parameter Problem message to the Source Address
Code 4 (SR Upper-layer Header Error),
Pointer set to the offset of the upper-layer header.
Interrupt packet processing and discard the packet.
S04. }
S05. If (IPv6 Hop Limit <= 1) {
S06. Send an ICMP Time Exceeded message to the Source Address,
Code 0 (Hop limit exceeded in transit),
Interrupt packet processing and discard the packet.
S07. }
S08. max_LE = (Hdr Ext Len / 2) - 1
S09. If ((Last Entry > max_LE) or (Segments Left > (Last Entry+1)) {
S10. 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.
S11. }
S12. Decrement Hop Limit by 1
S13. Decrement Segments Left by 1
S14. Push the MPLS label stack for B
S15. Submit the packet to the MPLS engine for transmission to the
topmost label.
S16. }
When processing the Upper-layer header of a packet matching a FIB
entry locally instantiated as an SRv6 End.BM SID, process the packet
as per Section 4.1.1.
4.16. Flavors
The PSP, USP and USD flavors are variants of the End, End.X and End.T
behaviors. For each of these behaviors these flavors MAY be
supported for a SID either individually or in combinations.
4.16.1. PSP: Penultimate Segment Pop of the SRH
The SRH processing of the End, End.X and End.T behaviors are
modified: after the instruction "S14. Update IPv6 DA with Segment
List[Segments Left]" is executed, the following instructions must be
executed as well:
Filsfils, et al. Expires August 26, 2020 [Page 22]
Internet-Draft SRv6 Network Programming February 2020
S14.1. If (Segments Left == 0) {
S14.2. Update the Next Header field in the preceding header to the
Next Header value of the SRH
S14.3. Decrease the IPv6 header Payload Length by the Hdr Ext Len
value of the SRH
S14.4. Remove the SRH from the IPv6 extension header chain
S14.5. }
4.16.2. USP: Ultimate Segment Pop of the SRH
The SRH processing of the End, End.X and End.T behaviors are
modified: the instructions S02-S04 are substituted by the following
ones:
S02. If (Segments Left == 0) {
S03.1. Update the Next Header field in the preceding header to the
Next Header value of the SRH
S03.2. Decrease the IPv6 header Payload Length by the Hdr Ext Len
value of the SRH
S03.3. Remove the SRH from the IPv6 extension header chain
S03.4. Proceed to process the next header in the packet
S04. }
4.16.3. USD: Ultimate Segment Decapsulation
The SRH processing of the End, End.X and End.T behaviors are
modified: the instructions S02-S04 are substituted by the following
ones:
S02. If (Segments Left == 0) {
S03. Skip the SRH processing and proceed to the next header
S04. }
Further on, the Upper-layer header processing of the End, End.X and
End.T behaviors are modified as follows:
End:
S01. If (Upper-layer Header type == 41 || 4) {
S02. Remove the outer IPv6 Header with all its extension headers
S03. Submit the packet to the egress IP FIB lookup and
transmission to the new destination
S04. } Else {
S05. Process as per Section 4.1.1
S06. }
Filsfils, et al. Expires August 26, 2020 [Page 23]
Internet-Draft SRv6 Network Programming February 2020
End.T:
S01. If (Upper-layer Header type == 41 || 4) {
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 egress IP FIB lookup and
Transmission to the new destination
S05. } Else {
S06. Process as per Section 4.1.1
S07. }
End.X:
S01. If (Upper-layer Header type == 41 || 4) {
S02. Remove the outer IPv6 Header with all its extension headers
S03. Forward the exposed IP packet to the L3 adjacency J
S04. } Else {
S05. Process as per Section 4.1.1
S06. }
An implementation that supports the USD flavor in conjunction with
the USP flavor MAY optimize the packet processing by first looking
whether the conditions for the USD flavor are met, in which case it
can proceed with USD processing else do USP processing.
5. SR Policy Headend Behaviors
This section describes a set of SR Policy Headend behaviors.
H.Encaps SR Headend Behavior with Encapsulation in an SR Policy
H.Encaps.Red H.Encaps with Reduced Encapsulation
H.Encaps.L2 H.Encaps Applied to Received L2 Frames
H.Encaps.L2.Red H.Encaps.Red Applied to Received L2 Frames
This list can be expanded in case any new functionality requires it.
Filsfils, et al. Expires August 26, 2020 [Page 24]
Internet-Draft SRv6 Network Programming February 2020
5.1. H.Encaps: SR Headend with Encapsulation in an SRv6 Policy
Node N receives two packets P1=(A, B2) and P2=(A,B2)(B3, B2, B1;
SL=1). B2 is neither a local address nor SID of N.
N steers the transit packets P1 and P2 into an SR Policy with a
Source Address T and a Segment list <S1, S2, S3>.
The H.Encaps encapsulation behavior is defined as follows:
S01. Push an IPv6 header with its own SRH (S3, S2, S1; SL=2)
S02. Set outer IPv6 SA = T and outer IPv6 DA = S1
S03. Set outer payload length, traffic class and flow label
S04. Set the outer Next-Header value
S05. Decrement inner Hop Limit or TTL
S06. Submit the packet to the IPv6 module for transmission to S1
After the H.Encaps behavior, P1' and P2' respectively look like:
- (T, S1) (S3, S2, S1; SL=2) (A, B2)
- (T, S1) (S3, S2, S1; SL=2) (A, B2) (B3, B2, B1; SL=1)
The received packet is encapsulated unmodified (with the exception of
the TTL or Hop Limit that is decremented as described in [RFC2473]).
The H.Encaps behavior is valid for any kind of Layer-3 traffic. This
behavior is commonly used for L3VPN with IPv4 and IPv6 deployments.
It may be also used for TI-LFA[I-D.ietf-rtgwg-segment-routing-ti-lfa]
at the point of local repair.
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.
S03: As described in [RFC6437] (IPv6 Flow Label Specification)
5.2. H.Encaps.Red: H.Encaps with Reduced Encapsulation
The H.Encaps.Red behavior is an optimization of the H.Encaps
behavior.
H.Encaps.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.
After the H.Encaps.Red behavior, P1' and P2' respectively look like:
- (T, S1) (S3, S2; SL=2) (A, B2)
Filsfils, et al. Expires August 26, 2020 [Page 25]
Internet-Draft SRv6 Network Programming February 2020
- (T, S1) (S3, S2; SL=2) (A, B2) (B3, B2, B1; SL=1)
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.
5.3. H.Encaps.L2: H.Encaps Applied to Received L2 Frames
The H.Encaps.L2 behavior encapsulates a received Ethernet [Ethernet]
frame and its attached VLAN header, if present, in an IPv6 packet
with an SRH. The Ethernet frame becomes the payload of the new IPv6
packet.
The Next Header field of the SRH MUST be set to 143.
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.
The encapsulating node MUST remove the preamble or frame check
sequence (FCS) from the Ethernet frame upon encapsulation and the
decapsulating node MUST regenerate the preamble or FCS before
forwarding Ethernet frame.
5.4. H.Encaps.L2.Red: H.Encaps.Red Applied to Received L2 frames
The H.Encaps.L2.Red behavior is an optimization of the H.Encaps.L2
behavior.
H.Encaps.L2.Red reduces the length of the SRH by excluding the first
SID in teh SRH of the pushed IPv6 header. The first SID is only
places 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.
Filsfils, et al. Expires August 26, 2020 [Page 26]
Internet-Draft SRv6 Network Programming February 2020
6. Operation
6.1. Counters
A node supporting this document SHOULD implement a combined traffic
counter (packets and bytes) per local SID entry, for traffic that
matched that SID and was processed correctly.
6.2. Flow-based Hash Computation
When a flow-based selection within a set needs to be performed, the
source address, the destination address and the flow label MUST be
included in the flow-based hash.
This occurs when a FIB lookup is performed and multiple ECMP paths
exist to the updated destination address.
This occurs when End.X, End.DX4, or End.DX6 are bound to an array of
adjacencies.
This occurs when the packet is steered in an SR policy whose selected
path has multiple SID lists.
Additionally, any transit router in an SRv6 domain includes the outer
flow label in its ECMP load-balancing hash [RFC6437].
7. Security Considerations
The security considerations for Segment Routing are discussed in
[RFC8402]. More specifically for SRv6 the security considerations
and the mechanisms for securing an SR domain are discussed in
[I-D.ietf-6man-segment-routing-header]. Together, they describe the
required security mechanisms that allow establishment of an SR domain
of trust to operate SRv6-based services for internal traffic while
preventing any external traffic from accessing or exploiting the
SRv6-based services.
This document introduces SRv6 Endpoint and SR Policy Headend
behaviors for implementation on SRv6 capable nodes in the network.
As such, this document does not introduce any new security
considerations.
8. Control Plane
In an SDN environment, one expects the controller to explicitly
provision the SIDs and/or discover them as part of a service
discovery function. Applications residing on top of the controller
Filsfils, et al. Expires August 26, 2020 [Page 27]
Internet-Draft SRv6 Network Programming February 2020
could then discover the required SIDs and combine them to form a
distributed network program.
The concept of "SRv6 network programming" refers to the capability
for an application to encode any complex program as a set of
individual functions distributed through the network. Some functions
relate to underlay SLA, others to overlay/tenant, others to complex
applications residing in VM and containers.
This section provides a high level overview of the control-plane
protocols involved with SRv6 and their specification.
8.1. IGP
The End, End.T and End.X SIDs express topological behaviors and hence
are expected to be signaled in the IGP together with the flavors PSP,
USP and USD[I-D.ietf-lsr-isis-srv6-extensions]. The IGP also
advertises the support for SRv6 capabilities of the node.
The presence of SIDs in the IGP do not imply any routing semantics to
the addresses represented by these SIDs. The routing reachability to
an IPv6 address is solely governed by the, non-SID-related, IGP
prefix reachability information that includes locators. Routing is
not governed neither influenced in any way by a SID advertisement in
the IGP.
These SIDs provide important topological behaviors for the IGP to
build TI-LFA[I-D.ietf-rtgwg-segment-routing-ti-lfa] based FRR
solutions and for TE processes relying on IGP topology database to
build SR policies.
8.2. BGP-LS
BGP-LS provides the functionality for topology discovery that
includes the SRv6 capabilities of the nodes, their locators and
locally instantiated SIDs [I-D.ietf-idr-bgpls-srv6-ext]. This
enables controllers or applications to build an inter-domain topology
that can be used for computation of SR Policies using the SRv6 SIDs.
8.3. BGP IP/VPN/EVPN
The End.DX4, End.DX6, End.DT4, End.DT6, End.DT46, End.DX2, End.DX2V,
End.DT2U and End.DT2M SIDs can be signaled in BGP
[I-D.ietf-bess-srv6-services].
Filsfils, et al. Expires August 26, 2020 [Page 28]
Internet-Draft SRv6 Network Programming February 2020
8.4. Summary
The following table summarizes behaviors for SIDs that can be
signaled in which each respective control plane protocol.
+-----------------------+-----+--------+-----------------+
| | IGP | BGP-LS | BGP IP/VPN/EVPN |
+-----------------------+-----+--------+-----------------+
| End (PSP, USP, USD) | X | X | |
| End.X (PSP, USP, USD) | X | X | |
| End.T (PSP, USP, USD) | X | X | |
| End.DX6 | X | X | X |
| End.DX4 | X | X | X |
| End.DT6 | X | X | X |
| End.DT4 | X | X | X |
| End.DT46 | X | X | X |
| End.DX2 | | X | X |
| End.DX2V | | X | X |
| End.DT2U | | X | X |
| End.DT2M | | X | X |
| End.B6.Encaps | | X | |
| End.B6.Encaps.Red | | X | |
| End.B6.BM | | X | |
+-----------------------+-----+--------+-----------------+
Table 1: SRv6 locally instantiated SIDs signaling
The following table summarizes which SR Policy Headend capabilities
are signaled in which signaling protocol.
+-----------------+-----+--------+-----------------+
| | IGP | BGP-LS | BGP IP/VPN/EVPN |
+-----------------+-----+--------+-----------------+
| H.Encaps | X | X | |
| H.Encaps.Red | X | X | |
| H.Encaps.L2 | | X | |
| H.Encaps.L2.Red | | X | |
+-----------------+-----+--------+-----------------+
Table 2: SRv6 Policy Headend behaviors signaling
The previous table describes generic capabilities. It does not
describe specific instantiated SR policies.
For example, a BGP-LS advertisement of H.Encaps behavior would
describe the capability of node N to perform a H.Encaps behavior,
specifically it would describe how many SIDs could be pushed by N
without significant performance degradation.
Filsfils, et al. Expires August 26, 2020 [Page 29]
Internet-Draft SRv6 Network Programming February 2020
As a reminder, an SR policy is always assigned a Binding SID
[RFC8402]. BSIDs are also advertised in BGP-LS as shown in Table 1.
Hence, the Table 2 only focuses on the generic capabilities related
to H.Encaps.
9. IANA Considerations
9.1. Ethernet Next Header Type
This document requests IANA to allocate, in the "Protocol Numbers"
registry (https://www.iana.org/assignments/protocol-numbers/protocol-
numbers.xhtml), a new value for "Ethernet" with the following
definition: The value 143 in the Next Header field of an IPv6 header
or any extension header indicates that the payload is an Ethernet
[Ethernet].
IANA has done a temporary allocation of Protocol Number 143.
9.2. SRv6 Endpoint Behaviors Registry
This document requests IANA to create a new top-level registry called
"Segment Routing Parameters". This registry is being defined to
serve as a top-level registry for keeping all other Segment Routing
sub-registries.
Additionally, a new sub-registry "SRv6 Endpoint Behaviors" is to be
created under top-level "Segment Routing Parameters" registry. This
sub-registry maintains 16-bit identifiers for the SRv6 Endpoint
behaviors. This registry is established to provide consistency for
control plane protocols which need to refer to these behaviors.
These values are not encoded in the function bits within a SID.
The range of the registry is 0-65535 (0x0000 - 0xFFFF) and has the
following registration rules and allocation policies:
+-------------+---------------+---------------------------+---------+
| Range | Hex | Registration procedure | Notes |
+-------------+---------------+---------------------------+---------+
| 0 | 0x0000 | Reserved | Invalid |
| 1-32767 | 0x0001-0x7FFF | FCFS | |
| 32768-65534 | 0x8000-0xFFFE | Reserved. Not to be | |
| | | allocated. | |
| 65535 | 0xFFFF | Reserved | Opaque |
+-------------+---------------+---------------------------+---------+
Table 3: SRv6 Endpoint Behaviors Registry
Filsfils, et al. Expires August 26, 2020 [Page 30]
Internet-Draft SRv6 Network Programming February 2020
9.2.1. Initial Registrations
The initial registrations for the sub-registry are as follows:
+-------------+--------+----------------------+---------------------+
| Value | Hex | Endpoint behavior | Reference |
+-------------+--------+----------------------+---------------------+
| 0 | 0x0000 | Invalid | [This.ID] |
| 1 | 0x0001 | End (no PSP, no USP) | [This.ID] |
| 2 | 0x0002 | End with PSP | [This.ID] |
| 3 | 0x0003 | End with USP | [This.ID] |
| 4 | 0x0004 | End with PSP&USP | [This.ID] |
| 5 | 0x0005 | End.X (no PSP, no | [This.ID] |
| | | USP) | |
| 6 | 0x0006 | End.X with PSP | [This.ID] |
| 7 | 0x0007 | End.X with USP | [This.ID] |
| 8 | 0x0008 | End.X with PSP&USP | [This.ID] |
| 9 | 0x0009 | End.T (no PSP, no | [This.ID] |
| | | USP) | |
| 10 | 0x000A | End.T with PSP | [This.ID] |
| 11 | 0x000B | End.T with USP | [This.ID] |
| 12 | 0x000C | End.T with PSP&USP | [This.ID] |
| 13 | 0x000D | Reserved | - |
| 14 | 0x000E | End.B6.Encaps | [This.ID] |
| 15 | 0x000F | End.BM | [This.ID] |
| 16 | 0x0010 | End.DX6 | [This.ID] |
| 17 | 0x0011 | End.DX4 | [This.ID] |
| 18 | 0x0012 | End.DT6 | [This.ID] |
| 19 | 0x0013 | End.DT4 | [This.ID] |
| 20 | 0x0014 | End.DT46 | [This.ID] |
| 21 | 0x0015 | End.DX2 | [This.ID] |
| 22 | 0x0016 | End.DX2V | [This.ID] |
| 23 | 0x0017 | End.DT2U | [This.ID] |
| 24 | 0x0018 | End.DT2M | [This.ID] |
| 25 | 0x0019 | Reserved | [This.ID] |
| 26 | 0x001A | Reserved | - |
| 27 | 0x001B | End.B6.Encaps.Red | [This.ID] |
| 28 | 0x001C | End with USD | [This.ID] |
| 29 | 0x001D | End with PSP&USD | [This.ID] |
| 30 | 0x001E | End with USP&USD | [This.ID] |
| 31 | 0x001F | End with PSP, USP & | [This.ID] |
| | | USD | |
| 32 | 0x0020 | End.X with USD | [This.ID] |
| 33 | 0x0021 | End.X with PSP&USD | [This.ID] |
| 34 | 0x0022 | End.X with USP&USD | [This.ID] |
| 35 | 0x0023 | End.X with PSP, USP | [This.ID] |
| | | & USD | |
| 36 | 0x0024 | End.T with USD | [This.ID] |
Filsfils, et al. Expires August 26, 2020 [Page 31]
Internet-Draft SRv6 Network Programming February 2020
| 37 | 0x0025 | End.T with PSP&USD | [This.ID] |
| 38 | 0x0026 | End.T with USP&USD | [This.ID] |
| 39 | 0x0027 | End.T with PSP, USP | [This.ID] |
| | | & USD | |
| 40-32767 | | Unassigned | |
| 32768-65534 | | Reserved | Change control |
| | | | under IETF |
| 65535 | 0xFFFF | Opaque | [This.ID] |
+-------------+--------+----------------------+---------------------+
Table 4: IETF - SRv6 Endpoint Behaviors
Requests for allocation from within the FCFS range must include a
point of contact and preferably also a brief description of how the
value will be used. This information may be provided with a
reference to an Internet Draft or an RFC or in some other
documentation that is permanently and readily available.
10. Acknowledgements
The authors would like to acknowledge Stefano Previdi, Dave Barach,
Mark Townsley, Peter Psenak, Thierry Couture, Kris Michielsen, Paul
Wells, Robert Hanzl, Dan Ye, Gaurav Dawra, Faisal Iqbal, Jaganbabu
Rajamanickam, David Toscano, Asif Islam, Jianda Liu, Yunpeng Zhang,
Jiaoming Li, Narendra A.K, Mike Mc Gourty, Bhupendra Yadav, Sherif
Toulan, Satish Damodaran, John Bettink, Kishore Nandyala Veera Venk,
Jisu Bhattacharya and Saleem Hafeez.
11. Contributors
Daniel Bernier
Bell Canada
Canada
Email: daniel.bernier@bell.ca
Dirk Steinberg
Lapishills Consulting Limited
Cyprus
Email: dirk@lapishills.com
Robert Raszuk
Bloomberg LP
United States of America
Email: robert@raszuk.net
Filsfils, et al. Expires August 26, 2020 [Page 32]
Internet-Draft SRv6 Network Programming February 2020
Bruno Decraene
Orange
France
Email: bruno.decraene@orange.com
Bart Peirens
Proximus
Belgium
Email: bart.peirens@proximus.com
Hani Elmalky
Google
United States of America
Email: helmalky@google.com
Prem Jonnalagadda
Barefoot Networks
United States of America
Email: prem@barefootnetworks.com
Milad Sharif
SambaNova Systems
United States of America
Email: milad.sharif@sambanova.ai
David Lebrun
Google
Belgium
Email: dlebrun@google.com
Stefano Salsano
Universita di Roma "Tor Vergata"
Italy
Email: stefano.salsano@uniroma2.it
Ahmed AbdelSalam
Gran Sasso Science Institute
Italy
Email: ahmed.abdelsalam@gssi.it
Filsfils, et al. Expires August 26, 2020 [Page 33]
Internet-Draft SRv6 Network Programming February 2020
Gaurav Naik
Drexel University
United States of America
Email: gn@drexel.edu
Arthi Ayyangar
Arrcus, Inc
United States of America
Email: arthi@arrcus.com
Satish Mynam
Arrcus, Inc
United States of America
Email: satishm@arrcus.com
Wim Henderickx
Nokia
Belgium
Email: wim.henderickx@nokia.com
Shaowen Ma
Juniper
Singapore
Email: mashao@juniper.net
Ahmed Bashandy
Individual
United States of America
Email: abashandy.ietf@gmail.com
Francois Clad
Cisco Systems, Inc.
France
Email: fclad@cisco.com
Kamran Raza
Cisco Systems, Inc.
Canada
Email: skraza@cisco.com
Filsfils, et al. Expires August 26, 2020 [Page 34]
Internet-Draft SRv6 Network Programming February 2020
Darren Dukes
Cisco Systems, Inc.
Canada
Email: ddukes@cisco.com
Patrice Brissete
Cisco Systems, Inc.
Canada
Email: pbrisset@cisco.com
Zafar Ali
Cisco Systems, Inc.
United States of America
Email: zali@cisco.com
Ketan Talaulikar
Cisco Systems, Inc.
India
Email: ketant@cisco.com
12. References
12.1. Normative References
[Ethernet]
DigitalEquipment, Intel, and Xerox, "The Ethernet -- A
Local Area Network: Data Link Layer and Physical Layer
(Version 2.0)", November 1982.
[]
Filsfils, C., Dukes, D., Previdi, S., Leddy, J.,
Matsushima, S., and D. Voyer, "IPv6 Segment Routing Header
(SRH)", draft-ietf-6man-segment-routing-header-26 (work in
progress), October 2019.
[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>.
[RFC2473] Conta, A. and S. Deering, "Generic Packet Tunneling in
IPv6 Specification", RFC 2473, DOI 10.17487/RFC2473,
December 1998, <https://www.rfc-editor.org/info/rfc2473>.
Filsfils, et al. Expires August 26, 2020 [Page 35]
Internet-Draft SRv6 Network Programming February 2020
[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>.
[RFC8200] Deering, S. and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", STD 86, RFC 8200,
DOI 10.17487/RFC8200, July 2017,
<https://www.rfc-editor.org/info/rfc8200>.
[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>.
12.2. Informative References
[I-D.filsfils-spring-srv6-net-pgm-illustration]
Filsfils, C., Camarillo, P., Li, Z., Matsushima, S.,
Decraene, B., Steinberg, D., Lebrun, D., Raszuk, R., and
J. Leddy, "Illustrations for SRv6 Network Programming",
draft-filsfils-spring-srv6-net-pgm-illustration-01 (work
in progress), August 2019.
[I-D.ietf-bess-srv6-services]
Dawra, G., Filsfils, C., Raszuk, R., Decraene, B., Zhuang,
S., and J. Rabadan, "SRv6 BGP based Overlay services",
draft-ietf-bess-srv6-services-01 (work in progress),
November 2019.
[I-D.ietf-idr-bgpls-srv6-ext]
Dawra, G., Filsfils, C., Talaulikar, K., Chen, M.,
daniel.bernier@bell.ca, d., and B. Decraene, "BGP Link
State Extensions for SRv6", draft-ietf-idr-bgpls-
srv6-ext-02 (work in progress), January 2020.
[I-D.ietf-lsr-isis-srv6-extensions]
Psenak, P., Filsfils, C., Bashandy, A., Decraene, B., and
Z. Hu, "IS-IS Extension to Support Segment Routing over
IPv6 Dataplane", draft-ietf-lsr-isis-srv6-extensions-05
(work in progress), February 2020.
[I-D.ietf-rtgwg-segment-routing-ti-lfa]
Litkowski, S., Bashandy, A., Filsfils, C., Decraene, B.,
Francois, P., Voyer, D., Clad, F., and P. Camarillo,
"Topology Independent Fast Reroute using Segment Routing",
draft-ietf-rtgwg-segment-routing-ti-lfa-02 (work in
progress), January 2020.
Filsfils, et al. Expires August 26, 2020 [Page 36]
Internet-Draft SRv6 Network Programming February 2020
[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>.
[RFC6437] Amante, S., Carpenter, B., Jiang, S., and J. Rajahalme,
"IPv6 Flow Label Specification", RFC 6437,
DOI 10.17487/RFC6437, November 2011,
<https://www.rfc-editor.org/info/rfc6437>.
[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>.
Authors' Addresses
Clarence Filsfils (editor)
Cisco Systems, Inc.
Belgium
Email: cf@cisco.com
Pablo Camarillo Garvia (editor)
Cisco Systems, Inc.
Spain
Email: pcamaril@cisco.com
John Leddy
Individual Contributor
United States of America
Email: john@leddy.net
Daniel Voyer
Bell Canada
Canada
Email: daniel.voyer@bell.ca
Filsfils, et al. Expires August 26, 2020 [Page 37]
Internet-Draft SRv6 Network Programming February 2020
Satoru Matsushima
SoftBank
1-9-1,Higashi-Shimbashi,Minato-Ku
Tokyo 105-7322
Japan
Email: satoru.matsushima@g.softbank.co.jp
Zhenbin Li
Huawei Technologies
China
Email: lizhenbin@huawei.com
Filsfils, et al. Expires August 26, 2020 [Page 38]
