draft-ietf-lsr-flex-algo-08.txt   draft-ietf-lsr-flex-algo-09.txt 
Network Working Group P. Psenak, Ed. Network Working Group P. Psenak, Ed.
Internet-Draft Cisco Systems Internet-Draft Cisco Systems
Intended status: Standards Track S. Hegde Intended status: Standards Track S. Hegde
Expires: January 11, 2021 Juniper Networks, Inc. Expires: February 15, 2021 Juniper Networks, Inc.
C. Filsfils C. Filsfils
K. Talaulikar K. Talaulikar
Cisco Systems, Inc. Cisco Systems, Inc.
A. Gulko A. Gulko
Refinitiv Refinitiv
July 10, 2020 August 14, 2020
IGP Flexible Algorithm IGP Flexible Algorithm
draft-ietf-lsr-flex-algo-08.txt draft-ietf-lsr-flex-algo-09.txt
Abstract Abstract
IGP protocols traditionally compute best paths over the network based IGP protocols traditionally compute best paths over the network based
on the IGP metric assigned to the links. Many network deployments on the IGP metric assigned to the links. Many network deployments
use RSVP-TE based or Segment Routing based Traffic Engineering to use RSVP-TE based or Segment Routing based Traffic Engineering to
enforce traffic over a path that is computed using different metrics steer traffic over a path that is computed using different metrics or
or constraints than the shortest IGP path. This document proposes a constraints than the shortest IGP path. This document proposes a
solution that allows IGPs themselves to compute constraint based solution that allows IGPs themselves to compute constraint-based
paths over the network. This document also specifies a way of using paths over the network. This document also specifies a way of using
Segment Routing (SR) Prefix-SIDs and SRv6 locators to steer packets Segment Routing (SR) Prefix-SIDs and SRv6 locators to steer packets
along the constraint-based paths. along the constraint-based paths.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/. Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on January 11, 2021. This Internet-Draft will expire on February 15, 2021.
Copyright Notice Copyright Notice
Copyright (c) 2020 IETF Trust and the persons identified as the Copyright (c) 2020 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of (https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
skipping to change at page 2, line 42 skipping to change at page 2, line 42
6.2. ISIS Flexible Algorithm Include-Any Admin Group Sub-TLV . 11 6.2. ISIS Flexible Algorithm Include-Any Admin Group Sub-TLV . 11
6.3. ISIS Flexible Algorithm Include-All Admin Group Sub-TLV . 11 6.3. ISIS Flexible Algorithm Include-All Admin Group Sub-TLV . 11
6.4. ISIS Flexible Algorithm Definition Flags Sub-TLV . . . . 11 6.4. ISIS Flexible Algorithm Definition Flags Sub-TLV . . . . 11
6.5. ISIS Flexible Algorithm Exclude SRLG Sub-TLV . . . . . . 12 6.5. ISIS Flexible Algorithm Exclude SRLG Sub-TLV . . . . . . 12
7. Sub-TLVs of OSPF FAD TLV . . . . . . . . . . . . . . . . . . 13 7. Sub-TLVs of OSPF FAD TLV . . . . . . . . . . . . . . . . . . 13
7.1. OSPF Flexible Algorithm Exclude Admin Group Sub-TLV . . . 13 7.1. OSPF Flexible Algorithm Exclude Admin Group Sub-TLV . . . 13
7.2. OSPF Flexible Algorithm Include-Any Admin Group Sub-TLV . 14 7.2. OSPF Flexible Algorithm Include-Any Admin Group Sub-TLV . 14
7.3. OSPF Flexible Algorithm Include-All Admin Group Sub-TLV . 14 7.3. OSPF Flexible Algorithm Include-All Admin Group Sub-TLV . 14
7.4. OSPF Flexible Algorithm Definition Flags Sub-TLV . . . . 14 7.4. OSPF Flexible Algorithm Definition Flags Sub-TLV . . . . 14
7.5. OSPF Flexible Algorithm Exclude SRLG Sub-TLV . . . . . . 16 7.5. OSPF Flexible Algorithm Exclude SRLG Sub-TLV . . . . . . 16
8. ISIS Flex-Algorithm Prefix Metric Sub-TLV . . . . . . . . . . 16 8. ISIS Flexible Algorithm Prefix Metric Sub-TLV . . . . . . . . 16
9. OSPF Flex-Algorithm Prefix Metric Sub-TLV . . . . . . . . . . 17 9. OSPF Flexible Algorithm Prefix Metric Sub-TLV . . . . . . . . 17
10. Advertisement of Node Participation in a Flex-Algorithm . . . 18 10. Advertisement of Node Participation in a Flex-Algorithm . . . 18
10.1. Advertisement of Node Participation for Segment Routing 18 10.1. Advertisement of Node Participation for Segment Routing 18
10.2. Advertisement of Node Participation for Other 10.2. Advertisement of Node Participation for Other
Applications . . . . . . . . . . . . . . . . . . . . . . 19 Applications . . . . . . . . . . . . . . . . . . . . . . 19
11. Advertisement of Link Attributes for Flex-Algorithm . . . . . 19 11. Advertisement of Link Attributes for Flex-Algorithm . . . . . 19
12. Calculation of Flexible Algorithm Paths . . . . . . . . . . . 20 12. Calculation of Flexible Algorithm Paths . . . . . . . . . . . 20
12.1. Multi-area and Multi-domain Considerations . . . . . . . 21 12.1. Multi-area and Multi-domain Considerations . . . . . . . 21
13. Flex-Algorithm and Forwarding Plane . . . . . . . . . . . . . 22 13. Flex-Algorithm and Forwarding Plane . . . . . . . . . . . . . 22
13.1. Segment Routing MPLS Forwarding for Flex-Algorithm . . . 22 13.1. Segment Routing MPLS Forwarding for Flex-Algorithm . . . 23
13.2. SRv6 Forwarding for Flex-Algorithm . . . . . . . . . . . 23 13.2. SRv6 Forwarding for Flex-Algorithm . . . . . . . . . . . 23
13.3. Other Applications' Forwarding for Flex-Algorithm . . . 24 13.3. Other Applications' Forwarding for Flex-Algorithm . . . 24
14. Operational considerations . . . . . . . . . . . . . . . . . 24 14. Operational considerations . . . . . . . . . . . . . . . . . 24
14.1. Inter-area Considerations . . . . . . . . . . . . . . . 24 14.1. Inter-area Considerations . . . . . . . . . . . . . . . 24
14.2. Usage of SRLG Exclude Rule with Flex-Algorithm . . . . . 25 14.2. Usage of SRLG Exclude Rule with Flex-Algorithm . . . . . 25
14.3. Max-metric consideration . . . . . . . . . . . . . . . . 26 14.3. Max-metric consideration . . . . . . . . . . . . . . . . 26
15. Backward Compatibility . . . . . . . . . . . . . . . . . . . 26 15. Backward Compatibility . . . . . . . . . . . . . . . . . . . 26
16. Security Considerations . . . . . . . . . . . . . . . . . . . 26 16. Security Considerations . . . . . . . . . . . . . . . . . . . 26
17. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 26 17. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 27
17.1. IGP IANA Considerations . . . . . . . . . . . . . . . . 27 17.1. IGP IANA Considerations . . . . . . . . . . . . . . . . 27
17.1.1. IGP Algorithm Types Registry . . . . . . . . . . . . 27 17.1.1. IGP Algorithm Types Registry . . . . . . . . . . . . 27
17.1.2. IGP Metric-Type Registry . . . . . . . . . . . . . . 27 17.1.2. IGP Metric-Type Registry . . . . . . . . . . . . . . 27
17.2. Flex-Algorithm Definition Flags Registry . . . . . . . . 27 17.2. Flexible Algorithm Definition Flags Registry . . . . . . 28
17.3. ISIS IANA Considerations . . . . . . . . . . . . . . . . 28 17.3. ISIS IANA Considerations . . . . . . . . . . . . . . . . 28
17.3.1. Sub TLVs for Type 242 . . . . . . . . . . . . . . . 28 17.3.1. Sub TLVs for Type 242 . . . . . . . . . . . . . . . 28
17.3.2. Sub TLVs for for TLVs 135, 235, 236, and 237 . . . . 28 17.3.2. Sub TLVs for for TLVs 135, 235, 236, and 237 . . . . 28
17.3.3. Sub-Sub-TLVs for Flexible Algorithm Definition Sub- 17.3.3. Sub-Sub-TLVs for Flexible Algorithm Definition Sub-
TLV . . . . . . . . . . . . . . . . . . . . . . . . 28 TLV . . . . . . . . . . . . . . . . . . . . . . . . 28
17.4. OSPF IANA Considerations . . . . . . . . . . . . . . . . 29 17.4. OSPF IANA Considerations . . . . . . . . . . . . . . . . 29
17.4.1. OSPF Router Information (RI) TLVs Registry . . . . . 29 17.4.1. OSPF Router Information (RI) TLVs Registry . . . . . 29
17.4.2. OSPFv2 Extended Prefix TLV Sub-TLVs . . . . . . . . 30 17.4.2. OSPFv2 Extended Prefix TLV Sub-TLVs . . . . . . . . 30
17.4.3. OSPFv3 Extended-LSA Sub-TLVs . . . . . . . . . . . . 30 17.4.3. OSPFv3 Extended-LSA Sub-TLVs . . . . . . . . . . . . 30
17.4.4. OSPF Flexible Algorithm Definition TLV Sub-TLV 17.4.4. OSPF Flexible Algorithm Definition TLV Sub-TLV
Registry . . . . . . . . . . . . . . . . . . . . . . 30 Registry . . . . . . . . . . . . . . . . . . . . . . 30
17.4.5. Link Attribute Applications Registry . . . . . . . . 31 17.4.5. Link Attribute Applications Registry . . . . . . . . 31
18. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 31 18. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 31
19. References . . . . . . . . . . . . . . . . . . . . . . . . . 32 19. References . . . . . . . . . . . . . . . . . . . . . . . . . 32
19.1. Normative References . . . . . . . . . . . . . . . . . . 32 19.1. Normative References . . . . . . . . . . . . . . . . . . 32
19.2. Informative References . . . . . . . . . . . . . . . . . 34 19.2. Informative References . . . . . . . . . . . . . . . . . 34
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 35 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 35
1. Introduction 1. Introduction
An IGP computed path based on the shortest IGP metric must often be An IGP-computed path based on the shortest IGP metric must often be
replaced by a traffic engineered path due to the traffic requirements replaced by a traffic-engineered path due to the traffic requirements
which are not reflected by the IGP metric. Some networks engineer which are not reflected by the IGP metric. Some networks engineer
the IGP metric assignments in a way that the IGP Metric reflects the the IGP metric assignments in a way that the IGP metric reflects the
link bandwidth or delay. If, for example, the IGP metric is link bandwidth or delay. If, for example, the IGP metric is
reflecting the bandwidth on the link and the application traffic is reflecting the bandwidth on the link and the application traffic is
delay sensitive, the best IGP path may not reflect the best path from delay sensitive, the best IGP path may not reflect the best path from
such an application's perspective. such an application's perspective.
To overcome this limitation, various sorts of traffic engineering To overcome this limitation, various sorts of traffic engineering
have been deployed, including RSVP-TE and SR-TE, in which case the TE have been deployed, including RSVP-TE and SR-TE, in which case the TE
component is responsible for computing paths based on additional component is responsible for computing paths based on additional
metrics and/or constraints. Such paths need to be installed in the metrics and/or constraints. Such paths need to be installed in the
forwarding tables in addition to, or as a replacement for, the forwarding tables in addition to, or as a replacement for, the
original paths computed by IGPs. Tunnels are often used to represent original paths computed by IGPs. Tunnels are often used to represent
the engineered paths and mechanisms like one described in [RFC3906] the engineered paths and mechanisms like one described in [RFC3906]
are used to replace the native IGP paths with such tunnel paths. are used to replace the native IGP paths with such tunnel paths.
This document specifies a set of extensions to ISIS, OSPFv2 and This document specifies a set of extensions to ISIS, OSPFv2, and
OSPFv3 that enable a router to send TLVs that identify (a) OSPFv3 that enable a router to advertise TLVs that identify (a)
calculation-type, (b) specify a metric-type, and (c )describe a set calculation-type, (b) specify a metric-type, and (c) describe a set
of constraints on the topology, that are to be used to compute the of constraints on the topology, that are to be used to compute the
best paths along the constrained topology. A given combination of best paths along the constrained topology. A given combination of
calculation-type, metric-type, and constraints is known as a calculation-type, metric-type, and constraints is known as a
"Flexible Algorithm Definition". A router that sends such a set of "Flexible Algorithm Definition". A router that sends such a set of
TLVs also assigns a Flex-Algorithm value, to the specified TLVs also assigns a Flex-Algorithm value to the specified combination
combination of calculation-type, metric-type, and constraints. of calculation-type, metric-type, and constraints.
This document also specifies a way for a router to use IGPs to This document also specifies a way for a router to use IGPs to
associate one or more SR Prefix-SIDs or SRv6 locators with a associate one or more SR Prefix-SIDs or SRv6 locators with a
particular Flex-Algorithm. Each such Prefix-SID or SRv6 locator then particular Flex-Algorithm. Each such Prefix-SID or SRv6 locator then
represents a path that is computed according to the identified Flex- represents a path that is computed according to the identified Flex-
Algorithm. Algorithm.
2. Requirements notation 2. Requirements notation
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in "OPTIONAL" in this document are to be interpreted as described in
[BCP14] [RFC2119] [RFC8174] when, and only when, they appear in all [BCP14] [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here. capitals, as shown here.
3. Terminology 3. Terminology
This section defines terms that are often used in this document. This section defines terms that are often used in this document.
Flexible Algorithm Definition - the set consisting of (a) Flexible Algorithm Definition (FAD) - the set consisting of (a)
calculation-type, (b) metric-type, and (c) a set of constraints,. calculation-type, (b) metric-type, and (c) a set of constraints.
Flexible Algorithm - a numeric identifier in the range 128-255 that Flexible Algorithm - a numeric identifier in the range 128-255 that
is associated via provisioning with the Flexible-Algorithm is associated via configuration with the Flexible-Algorithm
Definition. Definition.
Local Flexible Algorithm Definition - Flexible Algorithm Definition Local Flexible Algorithm Definition - Flexible Algorithm Definition
defined locally on the node. defined locally on the node.
Remote Flexible Algorithm Definition - Flexible Algorithm Definition Remote Flexible Algorithm Definition - Flexible Algorithm Definition
received from other nodes via IGP flooding. received from other nodes via IGP flooding.
Flexible Algorithm Participation - per application configuration Flexible Algorithm Participation - per application configuration
state that expresses whether the node is participating in a state that expresses whether the node is participating in a
particular Flexible Algorithm. particular Flexible Algorithm.
IGP Algorithm - value from the the "IGP Algorithm Types" registry IGP Algorithm - value from the the "IGP Algorithm Types" registry
defined under "Interior Gateway Protocol (IGP) Parameters" IANA defined under "Interior Gateway Protocol (IGP) Parameters" IANA
registries. IGP Algorithms represents the triplet (Calculation Type, registries. IGP Algorithms represents the triplet (Calculation Type,
Metric, Constraints), where the second and third elements of the Metric, Constraints), where the second and third elements of the
triple MAY not exist. triple MAY not be specified.
ABR - Area Border Router. In ISIS terminology it is also known as ABR - Area Border Router. In ISIS terminology it is also known as
L1/L2 router. L1/L2 router.
ASBR - Autonomous System Border Router. ASBR - Autonomous System Border Router.
4. Flexible Algorithm 4. Flexible Algorithm
Many possible constraints may be used to compute a path over a Many possible constraints may be used to compute a path over a
network. Some networks are deployed as multiple planes. A simple network. Some networks are deployed as multiple planes. A simple
form of constraint may be to use a particular plane. A more form of constraint may be to use a particular plane. A more
sophisticated form of constraint can include some extended metric as sophisticated form of constraint can include some extended metric as
described in [RFC7810]. Constraints which restrict paths to links described in [RFC8570]. Constraints which restrict paths to links
with specific affinities or avoid links with specific affinities are with specific affinities or avoid links with specific affinities are
also possible. Combinations of these are also possible. also possible. Combinations of these are also possible.
To provide maximum flexibility, we want to provide a mechanism that To provide maximum flexibility, we want to provide a mechanism that
allows a router to (a) identify a particular calculation-type, (b) allows a router to (a) identify a particular calculation-type, (b)
metric-type, (c) describe a particular set of constraints, and (d) metric-type, (c) describe a particular set of constraints, and (d)
assign a numeric identifier, referred to as Flex-Algorithm, to the assign a numeric identifier, referred to as Flex-Algorithm, to the
combination of that calculation-type, metric-type and those combination of that calculation-type, metric-type, and those
constraints. We want the mapping between the Flex-Algorithm and it's constraints. We want the mapping between the Flex-Algorithm and its
meaning to be flexible and defined by the user. As long as all meaning to be flexible and defined by the user. As long as all
routers in the domain have a common understanding as to what a routers in the domain have a common understanding as to what a
particular Flex-Algorithm represents, the resulting routing particular Flex-Algorithm represents, the resulting routing
computation is consistent and traffic is not subject to any looping. computation is consistent and traffic is not subject to any looping.
The set consisting of (a) calculation-type, (b) metric-type and (c) a The set consisting of (a) calculation-type, (b) metric-type, and (c)
set of constraints is referred to as a Flexible-Algorithm Definition. a set of constraints is referred to as a Flexible-Algorithm
Definition.
Flexible-Algorithm is a numeric identifier in the range 128-255 that Flexible-Algorithm is a numeric identifier in the range 128-255 that
is associated via provisioning with the Flexible-Algorithm is associated via configuratin with the Flexible-Algorithm
Definition. Definition.
IANA "IGP Algorithm Types" registry defines the set of values for IGP IANA "IGP Algorithm Types" registry defines the set of values for IGP
Algorithms. We propose to allocate the following values for Flex- Algorithms. We propose to allocate the following values for Flex-
Algorithms from this registry: Algorithms from this registry:
128-255 - Flex-Algorithms 128-255 - Flex-Algorithms
5. Flexible Algorithm Definition Advertisement 5. Flexible Algorithm Definition Advertisement
To guarantee the loop free forwarding for paths computed for a To guarantee the loop-free forwarding for paths computed for a
particular Flex-Algorithm, all routers that (a) are configured to particular Flex-Algorithm, all routers that (a) are configured to
participate in a particular Flex-Algorithm, and (b) are in the same participate in a particular Flex-Algorithm, and (b) are in the same
Flex-Algorithm definition advertisement scope MUST agree on the Flex-Algorithm definition advertisement scope MUST agree on the
definition of the Flex-Algorithm. definition of the Flex-Algorithm.
5.1. ISIS Flexible Algorithm Definition Sub-TLV 5.1. ISIS Flexible Algorithm Definition Sub-TLV
ISIS Flexible Algorithm Definition Sub-TLV (FAD Sub-TLV) is used to The ISIS Flexible Algorithm Definition Sub-TLV (FAD Sub-TLV) is used
advertise the definition of the Flex-Algorithm. to advertise the definition of the Flex-Algorithm.
ISIS FAD Sub-TLV is advertised as a Sub-TLV of the ISIS Router The ISIS FAD Sub-TLV is advertised as a Sub-TLV of the ISIS Router
Capability TLV-242 that is defined in [RFC7981]. Capability TLV-242 that is defined in [RFC7981].
ISIS FAD Sub-TLV has the following format: ISIS FAD Sub-TLV has the following format:
0 1 2 3 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 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 |Flex-Algorithm | Metric-Type | | Type | Length |Flex-Algorithm | Metric-Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Calc-Type | Priority | | Calc-Type | Priority |
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Length: variable, dependent on the included Sub-TLVs Length: variable, dependent on the included Sub-TLVs
Flex-Algorithm: Single octet value between 128 and 255 inclusive. Flex-Algorithm: Single octet value between 128 and 255 inclusive.
Metric-Type: Type of metric to be used during the calculation. Metric-Type: Type of metric to be used during the calculation.
Following values are defined: Following values are defined:
0: IGP Metric 0: IGP Metric
1: Min Unidirectional Link Delay as defined in [RFC7810]. 1: Min Unidirectional Link Delay as defined in
[I-D.ietf-isis-te-app].
2: TE default metric as defined in [RFC5305]. 2: TE default metric as defined in [I-D.ietf-isis-te-app].
Calc-Type: value from 0 to 127 inclusive from the "IGP Algorithm Calc-Type: value from 0 to 127 inclusive from the "IGP Algorithm
Types" registry defined under "Interior Gateway Protocol (IGP) Types" registry defined under "Interior Gateway Protocol (IGP)
Parameters" IANA registries. IGP algorithms in the range of 0-127 Parameters" IANA registries. IGP algorithms in the range of 0-127
have a defined triplet (Calculation Type, Metric, Constraints). have a defined triplet (Calculation Type, Metric, Constraints).
When used to specify the Calc-Type in the FAD Sub-TLV, only the When used to specify the Calc-Type in the FAD Sub-TLV, only the
Calculation Type defined for the specified IGP Algorithm is used. Calculation Type defined for the specified IGP Algorithm is used.
The Metric/Constraints MUST NOT be inherited. If the required The Metric/Constraints MUST NOT be inherited. If the required
calculation type is Shortest Path First, the value 0 SHOULD appear calculation type is Shortest Path First, the value 0 SHOULD appear
in this field. in this field.
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L1/L2 router MUST NOT re-generate any FAD Sub-TLV from level 1 to L1/L2 router MUST NOT re-generate any FAD Sub-TLV from level 1 to
level 2. level 2.
5.2. OSPF Flexible Algorithm Definition TLV 5.2. OSPF Flexible Algorithm Definition TLV
OSPF FAD TLV is advertised as a top-level TLV of the RI LSA that is OSPF FAD TLV is advertised as a top-level TLV of the RI LSA that is
defined in [RFC7770]. defined in [RFC7770].
OSPF FAD TLV has the following format: OSPF FAD TLV has the following format:
0 1 2 3 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 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 | | Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Flex-Algorithm | Metric-Type | Calc-Type | Priority | |Flex-Algorithm | Metric-Type | Calc-Type | Priority |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sub-TLVs | | Sub-TLVs |
+ + + +
| ... | | ... |
| | | |
skipping to change at page 9, line 9 skipping to change at page 9, line 9
The RI LSA can be advertised at any of the defined opaque flooding The RI LSA can be advertised at any of the defined opaque flooding
scopes (link, area, or Autonomous System (AS)). For the purpose of scopes (link, area, or Autonomous System (AS)). For the purpose of
OSPF FAD TLV advertisement, area-scoped flooding is REQUIRED. The OSPF FAD TLV advertisement, area-scoped flooding is REQUIRED. The
Autonomous System flooding scope SHOULD not be used by default unless Autonomous System flooding scope SHOULD not be used by default unless
local configuration policy on the originating router indicates domain local configuration policy on the originating router indicates domain
wide flooding. wide flooding.
5.3. Common Handling of Flexible Algorithm Definition TLV 5.3. Common Handling of Flexible Algorithm Definition TLV
This section describes the protocol independent handling of the FAD This section describes the protocol-independent handling of the FAD
TLV (OSPF) or FAD Sub-TLV (ISIS). We will refer to it as FAD TLV in TLV (OSPF) or FAD Sub-TLV (ISIS). We will refer to it as FAD TLV in
this section, even though in case of ISIS it is a Sub-TLV. this section, even though in case of ISIS it is a Sub-TLV.
The value of the Flex-Algorithm MUST be between 128 and 255 The value of the Flex-Algorithm MUST be between 128 and 255
inclusive. If it is not, the FAD TLV MUST be ignored. inclusive. If it is not, the FAD TLV MUST be ignored.
Only a subset of the routers participating in the particular Flex- Only a subset of the routers participating in the particular Flex-
Algorithm need to advertise the definition of the Flex-Algorithm. Algorithm need to advertise the definition of the Flex-Algorithm.
Every router, that is configured to participate in a particular Flex- Every router, that is configured to participate in a particular Flex-
skipping to change at page 9, line 31 skipping to change at page 9, line 31
following ordered rules. This allows for the consistent Flex- following ordered rules. This allows for the consistent Flex-
Algorithm definition selection in cases where different routers Algorithm definition selection in cases where different routers
advertise different definitions for a given Flex-Algorithm: advertise different definitions for a given Flex-Algorithm:
1. From the advertisements of the FAD in the area (including both 1. From the advertisements of the FAD in the area (including both
locally generated advertisements and received advertisements) locally generated advertisements and received advertisements)
select the one(s) with the highest priority value. select the one(s) with the highest priority value.
2. If there are multiple advertisements of the FAD with the same 2. If there are multiple advertisements of the FAD with the same
highest priority, select the one that is originated from the highest priority, select the one that is originated from the
router with the highest System-ID in case of ISIS or Router ID in router with the highest System-ID, in the case of ISIS, or Router
case of OSPFv2 and OSPFv3. For ISIS the System-ID is described in ID, in the case of OSPFv2 and OSPFv3. For ISIS, the System-ID is
[ISO10589]. For OSPFv2 and OSPFv3 standard Router ID is described described in [ISO10589]. For OSPFv2 and OSPFv3, standard Router
in [RFC2328] and [RFC5340] respectively. ID is described in [RFC2328] and [RFC5340] respectively.
A router that is not configured to participate in a particular Flex- A router that is not configured to participate in a particular Flex-
Algorithm MUST ignore FAD Sub-TLVs advertisements for such Flex- Algorithm MUST ignore FAD Sub-TLVs advertisements for such Flex-
Algorithm. Algorithm.
A router that is not participating in a particular Flex-Algorithm is A router that is not participating in a particular Flex-Algorithm is
allowed to advertise FAD for such Flex-Algorithm. Receiving routers allowed to advertise FAD for such Flex-Algorithm. Receiving routers
MUST consider FAD advertisement regardless of the Flex-Algorithm MUST consider FAD advertisement regardless of the Flex-Algorithm
participation of the FAD originator. participation of the FAD originator.
Any change in the Flex-Algorithm definition may result in temporary Any change in the Flex-Algorithm definition may result in temporary
disruption of traffic that is forwarded based on such Flex-Algorithm disruption of traffic that is forwarded based on such Flex-Algorithm
paths. The impact is similar to any other event that requires paths. The impact is similar to any other event that requires
network wide convergence. network-wide convergence.
If a node is configured to participate in a particular Flexible- If a node is configured to participate in a particular Flexible-
Algorithm, but the selected Flex-Algorithm definition includes Algorithm, but the selected Flex-Algorithm definition includes
calculation-type, metric-type, constraint, flag or Sub-TLV that is calculation-type, metric-type, constraint, flag, or Sub-TLV that is
not supported by the node, it MUST stop participating in such not supported by the node, it MUST stop participating in such
Flexible-Algorithm. That implies that it MUST NOT announce Flexible-Algorithm. That implies that it MUST NOT announce
participation for such Flexible-Algorithm as specified in Section 10 participation for such Flexible-Algorithm as specified in Section 10
and it MUST remove any forwarding state associated with it. and it MUST remove any forwarding state associated with it.
Flex-Algorithm definition is topology independent. It applies to all Flex-Algorithm definition is topology independent. It applies to all
topologies that a router participates in. topologies that a router participates in.
6. Sub-TLVs of ISIS FAD Sub-TLV 6. Sub-TLVs of ISIS FAD Sub-TLV
6.1. ISIS Flexible Algorithm Exclude Admin Group Sub-TLV 6.1. ISIS Flexible Algorithm Exclude Admin Group Sub-TLV
The Flexible-Algorithm definition can specify 'colors' that are used The Flexible Algorithm definition can specify 'colors' that are used
by the operator to exclude links during the Flex-Algorithm path by the operator to exclude links during the Flex-Algorithm path
computation. computation.
ISIS Flexible Algorithm Exclude Admin Group Sub-TLV is used to The ISIS Flexible Algorithm Exclude Admin Group Sub-TLV is used to
advertise the exclude rule that is used during the Flex-Algorithm advertise the exclude rule that is used during the Flex-Algorithm
path calculation as specified in Section 12. path calculation as specified in Section 12.
Flexible Algorithm Exclude Admin Group Sub-TLV (FAEAG Sub-TLV) is a The ISIS Flexible Algorithm Exclude Admin Group Sub-TLV (FAEAG Sub-
Sub-TLV of the ISIS FAD Sub-TLV. It has the following format: TLV) is a Sub-TLV of the ISIS FAD Sub-TLV. It has the following
format:
0 1 2 3 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 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 | | Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Extended Admin Group | | Extended Admin Group |
+- -+ +- -+
| ... | | ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
where: where:
Type: 1 Type: 1
Length: variable, dependent on the size of the Extended Admin Length: variable, dependent on the size of the Extended Admin
Group. MUST be a multiple of 4 octets. Group. MUST be a multiple of 4 octets.
Extended Administrative Group: Extended Administrative Group as Extended Administrative Group: Extended Administrative Group as
defined in [RFC7308]. defined in [RFC7308].
ISIS FAEAG Sub-TLV MAY NOT appear more then once in an ISIS FAD Sub- The ISIS FAEAG Sub-TLV MAY NOT appear more then once in an ISIS FAD
TLV. If it appears more then once, the ISIS FAD Sub-TLV MUST be Sub-TLV. If it appears more then once, the ISIS FAD Sub-TLV MUST be
ignored by the receiver. ignored by the receiver.
6.2. ISIS Flexible Algorithm Include-Any Admin Group Sub-TLV 6.2. ISIS Flexible Algorithm Include-Any Admin Group Sub-TLV
The Flexible-Algorithm definition can specify 'colors' that are used The Flexible Algorithm definition can specify 'colors' that are used
by the operator to include links during the Flex-Algorithm path by the operator to include links during the Flex-Algorithm path
computation. computation.
ISIS Flexible Algorithm Include-Any Admin Group Sub-TLV is used to The ISIS Flexible Algorithm Include-Any Admin Group Sub-TLV is used
advertise include-any rule that is used during the Flex-Algorithm to advertise include-any rule that is used during the Flex-Algorithm
path calculation as specified in Section 12. path calculation as specified in Section 12.
The format of the ISIS Flexible Algorithm Include-Any Admin Group The format of the ISIS Flexible Algorithm Include-Any Admin Group
Sub-TLV is identical to the format of the FAEAG Sub-TLV in Sub-TLV is identical to the format of the FAEAG Sub-TLV in
Section 6.1. Section 6.1.
Flexible Algorithm Include-Any Admin Group Sub-TLV Type is 2. The ISIS Flexible Algorithm Include-Any Admin Group Sub-TLV Type is
2.
ISIS Flexible Algorithm Include-Any Admin Group Sub-TLV MAY NOT The ISIS Flexible Algorithm Include-Any Admin Group Sub-TLV MAY NOT
appear more then once in an ISIS FAD Sub-TLV. If it appears more appear more then once in an ISIS FAD Sub-TLV. If it appears more
then once, the ISIS FAD Sub-TLV MUST be ignored by the receiver. then once, the ISIS FAD Sub-TLV MUST be ignored by the receiver.
6.3. ISIS Flexible Algorithm Include-All Admin Group Sub-TLV 6.3. ISIS Flexible Algorithm Include-All Admin Group Sub-TLV
The Flexible-Algorithm definition can specify 'colors' that are used The Flexible Algorithm definition can specify 'colors' that are used
by the operator to include link during the Flex-Algorithm path by the operator to include link during the Flex-Algorithm path
computation. computation.
ISIS Flexible Algorithm Include-All Admin Group Sub-TLV is used to The ISIS Flexible Algorithm Include-All Admin Group Sub-TLV is used
advertise include-all rule that is used during the Flex-Algorithm to advertise include-all rule that is used during the Flex-Algorithm
path calculation as specified in Section 12. path calculation as specified in Section 12.
The format of the ISIS Flexible Algorithm Include-All Admin Group The format of the ISIS Flexible Algorithm Include-All Admin Group
Sub-TLV is identical to the format of the FAEAG Sub-TLV in Sub-TLV is identical to the format of the FAEAG Sub-TLV in
Section 6.1. Section 6.1.
ISIS Flexible Algorithm Include-All Admin Group Sub-TLV Type is 3. The ISIS Flexible Algorithm Include-All Admin Group Sub-TLV Type is
3.
ISIS Flexible Algorithm Include-All Admin Group Sub-TLV MAY NOT The ISIS Flexible Algorithm Include-All Admin Group Sub-TLV MAY NOT
appear more then once in an ISIS FAD Sub-TLV. If it appears more appear more then once in an ISIS FAD Sub-TLV. If it appears more
then once, the ISIS FAD Sub-TLV MUST be ignored by the receiver. then once, the ISIS FAD Sub-TLV MUST be ignored by the receiver.
6.4. ISIS Flexible Algorithm Definition Flags Sub-TLV 6.4. ISIS Flexible Algorithm Definition Flags Sub-TLV
ISIS Flexible Algorithm Definition Flags Sub-TLV (FADF Sub-TLV) is a The ISIS Flexible Algorithm Definition Flags Sub-TLV (FADF Sub-TLV)
Sub-TLV of the ISIS FAD Sub-TLV. It has the following format: is a Sub-TLV of the ISIS FAD Sub-TLV. It has the following format:
0 1 2 3 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 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 | | Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags | | Flags |
+- -+ +- -+
| ... | | ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
where: where:
Type: 4 Type: 4
Length: variable, non-zero number of octets of the Flags field Length: variable, non-zero number of octets of the Flags field
Flags: Flags:
0 1 2 3 4 5 6 7... 0 1 2 3 4 5 6 7...
+-+-+-+-+-+-+-+-+... +-+-+-+-+-+-+-+-+...
|M| | | ... |M| | | ...
+-+-+-+-+-+-+-+-+... +-+-+-+-+-+-+-+-+...
M-flag: when set, Flex-Algorithm specific prefix metric MUST be M-flag: when set, the Flex-Algorithm specific prefix metric
used, if advertised with the prefix. This flag is not MUST be used, if advertised with the prefix. This flag is not
applicable to prefixes advertised as SRv6 locators. applicable to prefixes advertised as SRv6 locators.
Bits are defined/sent starting with Bit 0 defined above. Additional Bits are defined/sent starting with Bit 0 defined above. Additional
bit definitions that may be defined in the future SHOULD be assigned bit definitions that may be defined in the future SHOULD be assigned
in ascending bit order so as to minimize the number of bits that will in ascending bit order so as to minimize the number of bits that will
need to be transmitted. need to be transmitted.
Undefined bits MUST be transmitted as 0. Undefined bits MUST be transmitted as 0.
Bits that are NOT transmitted MUST be treated as if they are set to 0 Bits that are NOT transmitted MUST be treated as if they are set to 0
on receipt. on receipt.
ISIS FADF Sub-TLV MAY NOT appear more then once in an ISIS FAD Sub- The ISIS FADF Sub-TLV MAY NOT appear more then once in an ISIS FAD
TLV. If it appears more then once, the ISIS FAD Sub-TLV MUST be Sub-TLV. If it appears more then once, the ISIS FAD Sub-TLV MUST be
ignored by the receiver. ignored by the receiver.
If the ISIS FADF Sub-TLV is not present inside the ISIS FAD Sub-TLV, If the ISIS FADF Sub-TLV is not present inside the ISIS FAD Sub-TLV,
all the bits are assumed to be set to 0. all the bits are assumed to be set to 0.
6.5. ISIS Flexible Algorithm Exclude SRLG Sub-TLV 6.5. ISIS Flexible Algorithm Exclude SRLG Sub-TLV
The Flexible-Algorithm definition can specify Shared Risk Link Groups The Flexible Algorithm definition can specify Shared Risk Link Groups
(SRLGs) that the operator wants to exclude during the Flex-Algorithm (SRLGs) that the operator wants to exclude during the Flex-Algorithm
path computation. path computation.
ISIS Flexible Algorithm Exclude SRLG Sub-TLV (FAESRLG) is used to The ISIS Flexible Algorithm Exclude SRLG Sub-TLV (FAESRLG) is used to
advertise the exclude rule that is used during the Flex-Algorithm advertise the exclude rule that is used during the Flex-Algorithm
path calculation as specified in Section 12. path calculation as specified in Section 12.
ISIS FAESRLG Sub-TLV is a Sub-TLV of the ISIS FAD Sub-TLV. It has The ISIS FAESRLG Sub-TLV is a Sub-TLV of the ISIS FAD Sub-TLV. It
the following format: has the following format:
0 1 2 3 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 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 | | Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Shared Risk Link Group Value | | Shared Risk Link Group Value |
+- -+ +- -+
| ... | | ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
where: where:
Type: 5 Type: 5
Length: variable, dependent on number of SRLG values. MUST be a Length: variable, dependent on number of SRLG values. MUST be a
multiple of 4 octets. multiple of 4 octets.
Shared Risk Link Group Value: SRLG value as defined in [RFC5307]. Shared Risk Link Group Value: SRLG value as defined in [RFC5307].
ISIS FAESRLG Sub-TLV MAY NOT appear more then once in an ISIS FAD The ISIS FAESRLG Sub-TLV MAY NOT appear more then once in an ISIS FAD
Sub-TLV. If it appears more then once, the ISIS FAD Sub-TLV MUST be Sub-TLV. If it appears more then once, the ISIS FAD Sub-TLV MUST be
ignored by the receiver. ignored by the receiver.
7. Sub-TLVs of OSPF FAD TLV 7. Sub-TLVs of OSPF FAD TLV
7.1. OSPF Flexible Algorithm Exclude Admin Group Sub-TLV 7.1. OSPF Flexible Algorithm Exclude Admin Group Sub-TLV
Flexible Algorithm Exclude Admin Group Sub-TLV (FAEAG Sub-TLV) is a The Flexible Algorithm Exclude Admin Group Sub-TLV (FAEAG Sub-TLV) is
Sub-TLV of the OSPF FAD TLV. It's usage is described in Section 6.1. a Sub-TLV of the OSPF FAD TLV. It's usage is described in
It has the following format: Section 6.1. It has the following format:
0 1 2 3 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 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 | | Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Extended Admin Group | | Extended Admin Group |
+- -+ +- -+
| ... | | ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
where: where:
Type: 1 Type: 1
Length: variable, dependent on the size of the Extended Admin Length: variable, dependent on the size of the Extended Admin
Group. MUST be a multiple of 4 octets. Group. MUST be a multiple of 4 octets.
Extended Administrative Group: Extended Administrative Group as Extended Administrative Group: Extended Administrative Group as
defined in [RFC7308]. defined in [RFC7308].
OSPF FAEAG Sub-TLV MAY NOT appear more then once in an OSPF FAD TLV. The OSPF FAEAG Sub-TLV MAY NOT appear more then once in an OSPF FAD
If it appears more then once, the OSPF FAD TLV MUST be ignored by the TLV. If it appears more then once, the OSPF FAD TLV MUST be ignored
receiver. by the receiver.
7.2. OSPF Flexible Algorithm Include-Any Admin Group Sub-TLV 7.2. OSPF Flexible Algorithm Include-Any Admin Group Sub-TLV
The usage of this Sub-TLVs is described in Section 6.2. The usage of this Sub-TLVs is described in Section 6.2.
The format of the OSPF Flexible Algorithm Include-Any Admin Group The format of the OSPF Flexible Algorithm Include-Any Admin Group
Sub-TLV is identical to the format of the OSPF FAEAG Sub-TLV in Sub-TLV is identical to the format of the OSPF FAEAG Sub-TLV in
Section 7.1. Section 7.1.
Flexible Algorithm Include-Any Admin Group Sub-TLV Type is 2. The OSPF Flexible Algorithm Include-Any Admin Group Sub-TLV Type is
2.
OSPF Flexible Algorithm Include-Any Admin Group Sub-TLV MAY NOT The OSPF Flexible Algorithm Include-Any Admin Group Sub-TLV MAY NOT
appear more then once in an OSPF FAD TLV. If it appears more then appear more then once in an OSPF FAD TLV. If it appears more then
once, the OSPF FAD TLV MUST be ignored by the receiver. once, the OSPF FAD TLV MUST be ignored by the receiver.
7.3. OSPF Flexible Algorithm Include-All Admin Group Sub-TLV 7.3. OSPF Flexible Algorithm Include-All Admin Group Sub-TLV
The usage of this Sub-TLVs is described in Section 6.3. The usage of this Sub-TLVs is described in Section 6.3.
The format of the OSPF Flexible Algorithm Include-Any Admin Group The format of the OSPF Flexible Algorithm Include-Any Admin Group
Sub-TLV is identical to the format of the OSPF FAEAG Sub-TLV in Sub-TLV is identical to the format of the OSPF FAEAG Sub-TLV in
Section 7.1. Section 7.1.
Flexible Algorithm Include-Any Admin Group Sub-TLV Type is 3. The OSPF Flexible Algorithm Include-Any Admin Group Sub-TLV Type is
3.
OSPF Flexible Algorithm Include-All Admin Group Sub-TLV MAY NOT The OSPF Flexible Algorithm Include-All Admin Group Sub-TLV MAY NOT
appear more then once in an OSPF FAD TLV. If it appears more then appear more then once in an OSPF FAD TLV. If it appears more then
once, the OSPF FAD TLV MUST be ignored by the receiver. once, the OSPF FAD TLV MUST be ignored by the receiver.
7.4. OSPF Flexible Algorithm Definition Flags Sub-TLV 7.4. OSPF Flexible Algorithm Definition Flags Sub-TLV
OSPF Flexible Algorithm Definition Flags Sub-TLV (FADF Sub-TLV) is a The OSPF Flexible Algorithm Definition Flags Sub-TLV (FADF Sub-TLV)
Sub-TLV of the OSPF FAD TLV. It has the following format: is a Sub-TLV of the OSPF FAD TLV. It has the following format:
0 1 2 3 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 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 | | Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags | | Flags |
+- -+ +- -+
| ... | | ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
where: where:
Type: 4 Type: 4
Length: variable, dependent on the size of the Flags field. MUST Length: variable, dependent on the size of the Flags field. MUST
be a multiple of 4 octets. be a multiple of 4 octets.
Flags: Flags:
0 1 2 3 4 5 6 7... 0 1 2 3 4 5 6 7...
+-+-+-+-+-+-+-+-+... +-+-+-+-+-+-+-+-+...
|M| | | ... |M| | | ...
+-+-+-+-+-+-+-+-+... +-+-+-+-+-+-+-+-+...
M-flag: when set, Flex-Algorithm specific prefix metric MUST be M-flag: when set, the Flex-Algorithm specific prefix metric
used, if advertised with the prefix. This flag is not MUST be used, if advertised with the prefix. This flag is not
applicable to prefixes advertised as SRv6 locators. applicable to prefixes advertised as SRv6 locators.
Bits are defined/sent starting with Bit 0 defined above. Additional Bits are defined/sent starting with Bit 0 defined above. Additional
bit definitions that may be defined in the future SHOULD be assigned bit definitions that may be defined in the future SHOULD be assigned
in ascending bit order so as to minimize the number of bits that will in ascending bit order so as to minimize the number of bits that will
need to be transmitted. need to be transmitted.
Undefined bits MUST be transmitted as 0. Undefined bits MUST be transmitted as 0.
Bits that are NOT transmitted MUST be treated as if they are set to 0 Bits that are NOT transmitted MUST be treated as if they are set to 0
on receipt. on receipt.
OSPF FADF Sub-TLV MAY NOT appear more then once in an OSPF FAD TLV. The OSPF FADF Sub-TLV MAY NOT appear more then once in an OSPF FAD
If it appears more then once, the OSPF FAD TLV MUST be ignored by the TLV. If it appears more then once, the OSPF FAD TLV MUST be ignored
receiver. by the receiver.
If the OSPF FADF Sub-TLV is not present inside the OSPF FAD TLV, all If the OSPF FADF Sub-TLV is not present inside the OSPF FAD TLV, all
the bits are assumed to be set to 0. the bits are assumed to be set to 0.
7.5. OSPF Flexible Algorithm Exclude SRLG Sub-TLV 7.5. OSPF Flexible Algorithm Exclude SRLG Sub-TLV
OSPF Flexible Algorithm Exclude SRLG Sub-TLV (FAESRLG Sub-TLV) is a The OSPF Flexible Algorithm Exclude SRLG Sub-TLV (FAESRLG Sub-TLV) is
Sub-TLV of the OSPF FAD TLV. It's usage is described in Section 6.5. a Sub-TLV of the OSPF FAD TLV. Its usage is described in
It has the following format: Section 6.5. It has the following format:
0 1 2 3 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 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 | | Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Shared Risk Link Group Value | | Shared Risk Link Group Value |
+- -+ +- -+
| ... | | ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
where: where:
Type: 5 Type: 5
Length: variable, dependent on the number of SRLGs. MUST be a Length: variable, dependent on the number of SRLGs. MUST be a
multiple of 4 octets. multiple of 4 octets.
Shared Risk Link Group Value: SRLG value as defined in [RFC4203]. Shared Risk Link Group Value: SRLG value as defined in [RFC4203].
OSPF FAESRLG Sub-TLV MAY NOT appear more then once in an OSPF FAD The OSPF FAESRLG Sub-TLV MAY NOT appear more then once in an OSPF FAD
TLV. If it appears more then once, the OSPF FAD TLV MUST be ignored TLV. If it appears more then once, the OSPF FAD TLV MUST be ignored
by the receiver. by the receiver.
8. ISIS Flex-Algorithm Prefix Metric Sub-TLV 8. ISIS Flexible Algorithm Prefix Metric Sub-TLV
ISIS Flex-Algorithm Prefix Metric (FAPM) Sub-TLV supports the The ISIS Flexible Algorithm Prefix Metric (FAPM) Sub-TLV supports the
advertisement of a Flex-Algorithm specific prefix metric associated advertisement of a Flex-Algorithm specific prefix metric associated
with a given prefix advertisement. with a given prefix advertisement.
ISIS FAPM Sub-TLV is a sub-TLV of TLVs 135, 235, 236, and 237 and has The ISIS FAPM Sub-TLV is a sub-TLV of TLVs 135, 235, 236, and 237 and
the following format: has the following format:
0 1 2 3 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 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 |Flex-Algorithm | | Type | Length |Flex-Algorithm |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Metric | | Metric |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
where: where:
Type: 6 Type: 6
Length: 5 octets Length: 5 octets
Flex-Algorithm: Single octet value between 128 and 255 inclusive. Flex-Algorithm: Single octet value between 128 and 255 inclusive.
Metric: 4 octets of metric information Metric: 4 octets of metric information
ISIS FAPM Sub-TLV MAY appear multiple times in its parent TLV. If it The ISIS FAPM Sub-TLV MAY appear multiple times in its parent TLV.
appears more then once with the same Flex-Algorithm value, the first If it appears more then once with the same Flex-Algorithm value, the
appearance MUST be used and any subsequent ones MUST be ignored. first instance MUST be used and any subsequent instances MUST be
ignored.
If a prefix is advertised with a Flex-Algorithm prefix metric larger If a prefix is advertised with a Flex-Algorithm prefix metric larger
then MAX_PATH_METRIC as defined in [RFC5305] this prefix MUST NOT be then MAX_PATH_METRIC as defined in [RFC5305] this prefix MUST NOT be
considered during the Flexible-Algorithm computation. considered during the Flexible-Algorithm computation.
The usage of the Flex-Algorithm prefix metric is described in The usage of the Flex-Algorithm prefix metric is described in
Section 12. Section 12.
ISIS FAPM Sub-TLV MUST NOT be advertised as sub-TLV of the ISIS SRv6 The ISIS FAPM Sub-TLV MUST NOT be advertised as a sub-TLV of the ISIS
Locator TLV [I-D.ietf-lsr-isis-srv6-extensions]. ISIS SRv6 Locator SRv6 Locator TLV [I-D.ietf-lsr-isis-srv6-extensions]. The ISIS SRv6
TLV includes the Algorithm and Metric fields which MUST be used Locator TLV includes the Algorithm and Metric fields which MUST be
instead. If FAPM Sub-TLV is present as sub-TLV of the ISIS SRv6 used instead. If the FAPM Sub-TLV is present as a sub-TLV of the
Locator TLV in the received LSP, such FAPM Sub-TLV MUST be ignored. ISIS SRv6 Locator TLV in the received LSP, such FAPM Sub-TLV MUST be
ignored.
9. OSPF Flex-Algorithm Prefix Metric Sub-TLV 9. OSPF Flexible Algorithm Prefix Metric Sub-TLV
OSPF Flex-Algorithm Prefix Metric (FAPM) Sub-TLV supports the The OSPF Flexible Algorithm Prefix Metric (FAPM) Sub-TLV supports the
advertisement of a Flex-Algorithm specific prefix metric associated advertisement of a Flex-Algorithm specific prefix metric associated
with a given prefix advertisement. with a given prefix advertisement.
The OSPF Flex-Algorithm Prefix Metric (FAPM) Sub-TLVis a Sub-TLV of The OSPF Flex-Algorithm Prefix Metric (FAPM) Sub-TLVis a Sub-TLV of
the: the:
- OSPFv2 Extended Prefix TLV [RFC7684] - OSPFv2 Extended Prefix TLV [RFC7684]
- Following OSPFv3 TLVs as defined in [RFC8362]: - Following OSPFv3 TLVs as defined in [RFC8362]:
skipping to change at page 18, line 27 skipping to change at page 18, line 27
Type: 3 for OSPFv2, 26 for OSPFv3 Type: 3 for OSPFv2, 26 for OSPFv3
Length: 8 octets Length: 8 octets
Flex-Algorithm: Single octet value between 128 and 255 inclusive. Flex-Algorithm: Single octet value between 128 and 255 inclusive.
Reserved: Must be set to 0, ignored at reception. Reserved: Must be set to 0, ignored at reception.
Metric: 4 octets of metric information Metric: 4 octets of metric information
OSPF FAPM Sub-TLV MAY appear multiple times in its parent TLV. If it The OSPF FAPM Sub-TLV MAY appear multiple times in its parent TLV.
appears more then once with the same Flex-Algorithm value, the first If it appears more then once with the same Flex-Algorithm value, the
appearance MUST be used and any subsequent ones MUST be ignored. first instance MUST be used and any subsequent instances MUST be
ignored.
The usage of the Flex-Algorithm prefix metric is described in The usage of the Flex-Algorithm prefix metric is described in
Section 12. Section 12.
10. Advertisement of Node Participation in a Flex-Algorithm 10. Advertisement of Node Participation in a Flex-Algorithm
When a router is configured to support a particular Flex-Algorithm, When a router is configured to support a particular Flex-Algorithm,
we say it is participating in that Flex-Algorithm. we say it is participating in that Flex-Algorithm.
Paths computed for a specific Flex-Algorithm MAY be used by various Paths computed for a specific Flex-Algorithm MAY be used by various
applications, each potentially using its own specific data plane for applications, each potentially using its own specific data plane for
forwarding the data over such paths. To guarantee the presence of forwarding traffic over such paths. To guarantee the presence of the
the application specific forwarding state associated with a application specific forwarding state associated with a particular
particular Flex-Algorithm, a router MUST advertise its participation Flex-Algorithm, a router MUST advertise its participation for a
for a particular Flex-Algorithm for each application specifically. particular Flex-Algorithm for each application specifically.
10.1. Advertisement of Node Participation for Segment Routing 10.1. Advertisement of Node Participation for Segment Routing
[RFC8667], [RFC8665] and [RFC8666] (IGP Segment Routing extensions) [RFC8667], [RFC8665], and [RFC8666] (IGP Segment Routing extensions)
describe how SR-Algorithm is used to define how the best path is describe how the SR-Algorithm is used to compute the IGP best path.
computed by the IGP.
Routers advertise the support for the SR-Algorithm as a node Routers advertise the support for the SR-Algorithm as a node
capability as described in the above mentioned IGP Segment Routing capability as described in the above mentioned IGP Segment Routing
extensions. To advertise participation for a particular Flex- extensions. To advertise participation for a particular Flex-
Algorithm for Segment Routing, including both SR MPLS and SRv6, the Algorithm for Segment Routing, including both SR MPLS and SRv6, the
Flex-Algorithm value MUST be advertised in the SR-Algorithm TLV Flex-Algorithm value MUST be advertised in the SR-Algorithm TLV
(OSPF) or sub-TLV (ISIS). (OSPF) or sub-TLV (ISIS).
Segment Routing Flex-Algorithm participation advertisement is Segment Routing Flex-Algorithm participation advertisement is
topology independent. When a router advertises participation in an topology independent. When a router advertises participation in an
SR-Algorithm, the participation applies to all topologies in which SR-Algorithm, the participation applies to all topologies in which
the advertising node participates. the advertising node participates.
10.2. Advertisement of Node Participation for Other Applications 10.2. Advertisement of Node Participation for Other Applications
This section describes considerations related to how other This section describes considerations related to how other
applications can advertise its participation in a specific Flex- applications can advertise their participation in a specific Flex-
Algorithm. Algorithm.
Application specific Flex-Algorithm participation advertisements MAY Application-specific Flex-Algorithm participation advertisements MAY
be topology specific or MAY be topology independent, depending on the be topology specific or MAY be topology independent, depending on the
application itself. application itself.
Application specific advertisement for Flex-Algorithm participation Application-specific advertisement for Flex-Algorithm participation
MUST be defined for each application and is outside of the scope of MUST be defined for each application and is outside of the scope of
this document. this document.
11. Advertisement of Link Attributes for Flex-Algorithm 11. Advertisement of Link Attributes for Flex-Algorithm
Various link attributes may be used during the Flex-Algorithm path Various link attributes may be used during the Flex-Algorithm path
calculation. For example, include or exclude rules based on link calculation. For example, include or exclude rules based on link
affinities can be part of the Flex-Algorithm definition as defined in affinities can be part of the Flex-Algorithm definition as defined in
Section 6 and Section 7. Section 6 and Section 7.
Link attribute advertisements that are to be used during Flex- Link attribute advertisements that are to be used during Flex-
Algorithm calculation MUST use the Application Specific Link Algorithm calculation MUST use the Application-Specific Link
Attribute (ASLA) advertisements defined in [I-D.ietf-isis-te-app] or Attribute (ASLA) advertisements defined in [I-D.ietf-isis-te-app] or
[I-D.ietf-ospf-te-link-attr-reuse]. [I-D.ietf-ospf-te-link-attr-reuse]. In particular, the Min
Unidirectional Link Delay, TE Default Metric, Administrative Group,
Extended Administrative Group and Shared Risk Link Group TLVs MUST be
encoded in the ASLA advertisements for use with FlexAlgo.
A new Application Identifier Bit is defined to indicate that the ASLA A new Application Identifier Bit is defined to indicate that the ASLA
advertisement is associated with the Flex-Algorithm application. advertisement is associated with the Flex-Algorithm application.
This bit is set in the Standard Application Bit Mask (SABM) defined This bit is set in the Standard Application Bit Mask (SABM) defined
in [I-D.ietf-isis-te-app] or [I-D.ietf-ospf-te-link-attr-reuse]: in [I-D.ietf-isis-te-app] or [I-D.ietf-ospf-te-link-attr-reuse]:
Bit-3: Flexible Algorithm (X-bit) Bit-3: Flexible Algorithm (X-bit)
ASLA Admin Group Advertisements to be used by the Flexible Algorithm ASLA Admin Group Advertisements to be used by the Flexible Algorithm
Application MAY use either the Administrative Group or Extended Application MAY use either the Administrative Group or Extended
Administrative Group encodings. If the Administrative Group encoding Administrative Group encodings. If the Administrative Group encoding
is used then the first 32 bits of the corresponding FAD sub-TLVs are is used, then the first 32 bits of the corresponding FAD sub-TLVs are
mapped to the link attribute advertisements as specified in RFC 7308. mapped to the link attribute advertisements as specified in RFC 7308.
12. Calculation of Flexible Algorithm Paths 12. Calculation of Flexible Algorithm Paths
A router MUST be configured to participate in a given Flex-Algorithm A router MUST be configured to participate in a given Flex-Algorithm
K and MUST use the FAD selected based on the rules defined in K and MUST select the FAD based on the rules defined in Section 5.3
Section 5.3 before it can compute any path for that Flex-Algorithm. before it can compute any path for that Flex-Algorithm.
As described in Section 10, participation for any particular Flex- As described in Section 10, participation for any particular Flex-
Algorithm MUST be advertised on a per application basis. Calculation Algorithm MUST be advertised on a per-application basis. Calculation
of the paths for any particular Flex-Algorithm MUST be application of the paths for any particular Flex-Algorithm MUST be application
specific. specific.
The way applications handle nodes that do not participate in The way applications handle nodes that do not participate in
Flexible-Algorithm is application specific. If the application only Flexible-Algorithm is application specific. If the application only
wants to consider participating nodes during the Flex-Algorithm wants to consider participating nodes during the Flex-Algorithm
calculation, then when computing paths for a given Flex-Algorithm, calculation, then when computing paths for a given Flex-Algorithm,
all nodes that do not advertise participation for that Flex-Algorithm all nodes that do not advertise participation for that Flex-Algorithm
in the application specific advertisements MUST be pruned from the in their application-specific advertisements MUST be pruned from the
topology. Segment Routing, including both SR MPLS and SRv6, are topology. Segment Routing, including both SR MPLS and SRv6, are
applications that MUST use such pruning when computing Flex-Algorithm applications that MUST use such pruning when computing Flex-Algorithm
paths. paths.
When computing the path for a given Flex-Algorithm, the metric-type When computing the path for a given Flex-Algorithm, the metric-type
that is part of the Flex-Algorithm definition (Section 5) MUST be that is part of the Flex-Algorithm definition (Section 5) MUST be
used. used.
When computing the path for a given Flex-Algorithm, the calculation- When computing the path for a given Flex-Algorithm, the calculation-
type that is part of the Flex-Algorithm definition (Section 5) MUST type that is part of the Flex-Algorithm definition (Section 5) MUST
skipping to change at page 21, line 30 skipping to change at page 21, line 33
5. If the Flex-Algorithm definition uses other than IGP metric 5. If the Flex-Algorithm definition uses other than IGP metric
(Section 5), and such metric is not advertised for the particular (Section 5), and such metric is not advertised for the particular
link in a topology for which the computation is done, such link link in a topology for which the computation is done, such link
MUST be pruned from the computation. A metric of value 0 MUST NOT MUST be pruned from the computation. A metric of value 0 MUST NOT
be assumed in such case. be assumed in such case.
12.1. Multi-area and Multi-domain Considerations 12.1. Multi-area and Multi-domain Considerations
Any IGP Shortest Path Tree calculation is limited to a single area. Any IGP Shortest Path Tree calculation is limited to a single area.
This applies to Flex-Algorithm calculations as well. Given that the This applies to Flex-Algorithm calculations as well. Given that the
computing router does not have the visibility of the topology of next computing router does not have visibility of the topology of the next
areas or domain, the Flex-Algorithm specific path to an inter-area or areas or domain, the Flex-Algorithm specific path to an inter-area or
inter-domain prefix will be computed for the local area only. The inter-domain prefix will be computed for the local area only. The
egress L1/L2 router (ABR in OSPF), or ASBR for inter-domain case, egress L1/L2 router (ABR in OSPF), or ASBR for inter-domain case,
will be selected based on the best path for the given Flex-Algorithm will be selected based on the best path for the given Flex-Algorithm
in the local area and such egress ABR or ASBR router will be in the local area and such egress ABR or ASBR router will be
responsible to compute the best Flex-Algorithm specific path over the responsible to compute the best Flex-Algorithm specific path over the
next area or domain. This may produce an end-to-end path, which is next area or domain. This may produce an end-to-end path, which is
sub-optimal based on Flex-Algorithm constraints. In cases where the sub-optimal based on Flex-Algorithm constraints. In cases where the
ABR or ASBR has no reachability to a prefix for a given Flex- ABR or ASBR has no reachability to a prefix for a given Flex-
Algorithm in a next area or domain, the traffic may get dropped by Algorithm in the next area or domain, the traffic may be dropped by
the ABR/ASBR. the ABR/ASBR.
To allow the optimal end-to-end path for a inter-area or inter-domain To allow the optimal end-to-end path for an inter-area or inter-
prefixes for any Flex-Algorithm to be computed, the FAPM has been domain prefix for any Flex-Algorithm to be computed, the FAPM has
defined in Section 8 and Section 9. been defined in Section 8 and Section 9.
If the FAD selected based on the rules defined in Section 5.3 If the FAD selected based on the rules defined in Section 5.3
includes the M-flag, an ABR or ASBR MUST include the FAPM (Section 8, includes the M-flag, an ABR or ASBR MUST include the FAPM (Section 8,
Section 9) when advertising the prefix between areas or domains. Section 9) when advertising the prefix between areas or domains.
Such metric will be equal to the metric to reach the prefix for a Such metric will be equal to the metric to reach the prefix for a
given Flex-Algorithm in a source area or domain. This is similar in given Flex-Algorithm in a source area or domain. This is similar in
nature to how the metric is set when prefixes are advertised between nature to how the metric is set when prefixes are advertised between
areas or domains for default algorithm. areas or domains for the default algorithm.
If the FAD selected based on the rules defined in Section 5.3 If the FAD selected based on the rules defined in Section 5.3
includes the M-flag, FAPM MUST be used during calculation of prefix includes the M-flag, the FAPM MUST be used during calculation of
reachability for the inter-area and external prefixes. If the FAPM prefix reachability for the inter-area and external prefixes. If the
for the Flex-Algorithm is not advertised with the inter-area or FAPM for the Flex-Algorithm is not advertised with the inter-area or
external prefix reachability advertisement, the prefix MUST be external prefix reachability advertisement, the prefix MUST be
considered as unreachable for that Flex-Algorithm. considered as unreachable for that Flex-Algorithm.
Flex-Algorithm prefix metrics MUST NOT be used during the Flex- Flex-Algorithm prefix metrics MUST NOT be used during the Flex-
Algorithm computation unless the FAD selected based on the rules Algorithm computation unless the FAD selected based on the rules
defined in Section 5.3 includes the M-Flag, as described in defined in Section 5.3 includes the M-Flag, as described in
(Section 6.4 or Section 7.4). (Section 6.4 or Section 7.4).
If the FAD selected based on the rules defined in Section 5.3 does If the FAD selected based on the rules defined in Section 5.3 does
not includes the M-flag, it is NOT RECOMMENDED to use the Flex- not includes the M-flag, it is NOT RECOMMENDED to use the Flex-
Algoritm for inter-area or inter-domain prefix reachability. The Algorithm for inter-area or inter-domain prefix reachability. The
reason is that without the explicit Flex-Algorithm Prefix Metric reason is that without the explicit Flex-Algorithm Prefix Metric
advertisement it is not possible to conclude whether the ABR or ASBR advertisement, it is not possible to conclude whether the ABR or ASBR
has reachability to the inter-area or inter-domain prefix for a given has reachability to the inter-area or inter-domain prefix for a given
Flex-Algorithm in a next area or domain. Sending the Flex-Algoritm Flex-Algorithm in the next area or domain. Sending the Flex-Algoritm
traffic for such prefix towards the ABR or ASBR may result in traffic traffic for such prefix towards the ABR or ASBR may result in traffic
looping or black-holing. looping or black-holing.
FAPM MUST NOT be advertised with ISIS L1 or L2 intra-area, OSPFv2 The FAPM MUST NOT be advertised with ISIS L1 or L2 intra-area, OSPFv2
intra-area or OSPFv3 intra area routes. If the FAPM is advertised intra-area, or OSPFv3 intra-area routes. If the FAPM is advertised
for these route-types, it MUST be ignored during prefix reachability for these route-types, it MUST be ignored during the prefix
calculation. reachability calculation.
M-flag in FAD is not applicable to prefixes advertised as SRv6 The M-flag in FAD is not applicable to prefixes advertised as SRv6
locators. ISIS SRv6 Locator TLV includes the Algorithm and Metric locators. The ISIS SRv6 Locator TLV includes the Algorithm and
fields [I-D.ietf-lsr-isis-srv6-extensions]. When the ISIS SRv6 Metric fields [I-D.ietf-lsr-isis-srv6-extensions]. When the ISIS
Locator is advertised between areas or domains, the metric field in SRv6 Locator is advertised between areas or domains, the metric field
the Locator TLV MUST be used irrespective of the M flag in the FAD in the Locator TLV MUST be used irrespective of the M-flag in the FAD
advertisement. advertisement.
13. Flex-Algorithm and Forwarding Plane 13. Flex-Algorithm and Forwarding Plane
This section describes how Flex-Algorithm paths are used in This section describes how Flex-Algorithm paths are used in
forwarding. forwarding.
13.1. Segment Routing MPLS Forwarding for Flex-Algorithm 13.1. Segment Routing MPLS Forwarding for Flex-Algorithm
This section describes how Flex-Algorithm paths are used with SR MPLS This section describes how Flex-Algorithm paths are used with SR MPLS
forwarding. forwarding.
Prefix SID advertisements include an SR-Algorithm value and as such Prefix SID advertisements include an SR-Algorithm value and, as such,
are associated with the specified SR-Algorithm. Prefix-SIDs are also are associated with the specified SR-Algorithm. Prefix-SIDs are also
associated with a specific topology which is inherited from the associated with a specific topology which is inherited from the
associated prefix reachability advertisement. When the algorithm associated prefix reachability advertisement. When the algorithm
value advertised is a Flex-Algorithm value, the Prefix SID is value advertised is a Flex-Algorithm value, the Prefix SID is
associated with paths calculated using that Flex-Algorithm in the associated with paths calculated using that Flex-Algorithm in the
associated topology. associated topology.
A Flex-Algorithm path MUST be installed in the MPLS forwarding plane A Flex-Algorithm path MUST be installed in the MPLS forwarding plane
using the MPLS label that corresponds to the Prefix-SID that was using the MPLS label that corresponds to the Prefix-SID that was
advertised for that Flex-algorithm. If the Prefix SID for a given advertised for that Flex-algorithm. If the Prefix SID for a given
Flex-algorithm is not known, the Flex-Algorithm specific path cannot Flex-algorithm is not known, the Flex-Algorithm specific path cannot
be installed in the MPLS forwarding plane. be installed in the MPLS forwarding plane.
Traffic that is supposed to be routed via Flex-Algorithm specific Traffic that is supposed to be routed via Flex-Algorithm specific
paths, MUST be dropped where there are no such paths available. paths, MUST be dropped when there are no such paths available.
Loop Free Alternate (LFA) paths for a given Flex-Algorithm MUST be Loop Free Alternate (LFA) paths for a given Flex-Algorithm MUST be
computed using the same constraints as the calculation of the primary computed using the same constraints as the calculation of the primary
paths for that Flex-Algorithm. LFA paths MUST only use Prefix-SIDs paths for that Flex-Algorithm. LFA paths MUST only use Prefix-SIDs
advertised specifically for the given algorithm. LFA paths MUST NOT advertised specifically for the given algorithm. LFA paths MUST NOT
use an Adjacency-SID that belongs to a link that has been pruned from use an Adjacency-SID that belongs to a link that has been pruned from
the Flex-Algorithm computation. the Flex-Algorithm computation.
If LFA protection is being used to protect a given Flex-Algorithm If LFA protection is being used to protect a given Flex-Algorithm
paths, all routers in the area participating in the given Flex- paths, all routers in the area participating in the given Flex-
Algorithm SHOULD advertise at least one Flex-Algorithm specific Node- Algorithm SHOULD advertise at least one Flex-Algorithm specific Node-
SID. These Node-SIDs are used to enforce traffic over the LFA SID. These Node-SIDs are used to steer traffic over the LFA computed
computed backup path. backup path.
13.2. SRv6 Forwarding for Flex-Algorithm 13.2. SRv6 Forwarding for Flex-Algorithm
This section describes how Flex-Algorithm paths are used with SRv6 This section describes how Flex-Algorithm paths are used with SRv6
forwarding. forwarding.
In SRv6 a node is provisioned with topology/algorithm specific In SRv6 a node is provisioned with topology/algorithm specific
locators for each of the topology/algorithm pairs supported by that locators for each of the topology/algorithm pairs supported by that
node. Each locator is a covering prefix for all SIDs provisioned on node. Each locator is an aggregate prefix for all SIDs provisioned
that node which have the matching topology/algorithm. on that node which have the matching topology/algorithm.
SRv6 locator advertisement in IGPs The SRv6 locator advertisement in IGPs
([I-D.ietf-lsr-isis-srv6-extensions] ([I-D.ietf-lsr-isis-srv6-extensions]
[I-D.ietf-lsr-ospfv3-srv6-extensions]) includes the MTID value that [I-D.ietf-lsr-ospfv3-srv6-extensions]) includes the MTID value that
associates the locator with a specific topology. SRv6 locator associates the locator with a specific topology. SRv6 locator
advertisements also includes an Algorithm value that explicitly advertisements also includes an Algorithm value that explicitly
associates the locator with a specific algorithm. When the algorithm associates the locator with a specific algorithm. When the algorithm
value advertised with a locator represents a Flex-Algorithm, the value advertised with a locator represents a Flex-Algorithm, the
paths to the locator prefix MUST be calculated using the specified paths to the locator prefix MUST be calculated using the specified
Flex-Algorithm in the associated topology. Flex-Algorithm in the associated topology.
Forwarding entries for the locator prefixes advertised in IGPs MUST Forwarding entries for the locator prefixes advertised in IGPs MUST
be installed in the forwarding plane of the receiving SRv6 capable be installed in the forwarding plane of the receiving SRv6 capable
routers when the associated topology/algorithm is participating in routers when the associated topology/algorithm is participating in
them. Forwarding entries for locators associated with Flex- them. Forwarding entries for locators associated with Flex-
Algorithms in which the node is not participating MUST NOT be Algorithms in which the node is not participating MUST NOT be
installed in the forwarding. installed in the forwarding palne.
When the locator is associated with the Flex-Algorithm, LFA paths to When the locator is associated with a Flex-Algorithm, LFA paths to
the locator prefix MUST be calculated using such Flex-Algorithm in the locator prefix MUST be calculated using such Flex-Algorithm in
the associated topology, to guarantee that they follow the same the associated topology, to guarantee that they follow the same
constraints as the calculation of the primary paths. LFA paths MUST constraints as the calculation of the primary paths. LFA paths MUST
only use SRv6 SIDs advertised specifically for the given Flex- only use SRv6 SIDs advertised specifically for the given Flex-
Algorithm. Algorithm.
If LFA protection is being used to protect locators associated with a If LFA protection is being used to protect locators associated with a
given Flex-Algorithm, all routers in the area participating in the given Flex-Algorithm, all routers in the area participating in the
given Flex-Algorithm SHOULD advertise at least one Flex-Algorithm given Flex-Algorithm SHOULD advertise at least one Flex-Algorithm
specific locator and END SID per node and one END.X SID for every specific locator and END SID per node and one END.X SID for every
link that has not been pruned from such Flex-Algorithm computation. link that has not been pruned from such Flex-Algorithm computation.
These locators and SIDs are used to enforce traffic over the LFA These locators and SIDs are used to steer traffic over the LFA-
computed backup path. computed backup path.
13.3. Other Applications' Forwarding for Flex-Algorithm 13.3. Other Applications' Forwarding for Flex-Algorithm
Any application that wants to use Flex-Algorithm specific forwarding Any application that wants to use Flex-Algorithm specific forwarding
needs to install some form of Flex-Algorithm specific forwarding needs to install some form of Flex-Algorithm specific forwarding
entries. entries.
Application specific forwarding for Flex-Algorithm MUST be defined Application-specific forwarding for Flex-Algorithm MUST be defined
for each application and is outside of the scope of this document. for each application and is outside of the scope of this document.
14. Operational considerations 14. Operational considerations
14.1. Inter-area Considerations 14.1. Inter-area Considerations
The scope of the FA computation is an area, so is the scope of the The scope of the FA computation is an area, so is the scope of the
FAD. In ISIS the Router Capability TLV in which the FAD Sub-TLV is FAD. In ISIS, the Router Capability TLV in which the FAD Sub-TLV is
present MUST have the S-bit clear, which prevents it to be flooded advertised MUST have the S-bit clear, which prevents it to be flooded
outside of level in which it was originated. Even though in OSPF the outside of the level in which it was originated. Even though in OSPF
FAD Sub-TLV can be flooded in the RI LSA that has AS flooding scope, the FAD Sub-TLV can be flooded in an RI LSA that has AS flooding
the FAD selection is performed for individual area in which it is scope, the FAD selection is performed for each individual area in
being used. which it is being used.
There is no requirement for FAD for a particular Flex-Algorithm to be There is no requirement for the FAD for a particular Flex-Algorithm
identical in all areas in the network. For example, traffic for the to be identical in all areas in the network. For example, traffic
same Flex-Algorithm may be optimized for minimal delay (e.g., using for the same Flex-Algorithm may be optimized for minimal delay (e.g.,
delay metric) in one area or level, while being optimized for using delay metric) in one area or level, while being optimized for
available bandwidth (e.g., using IGP metric) in the other area or available bandwidth (e.g., using IGP metric) in another area or
level. level.
As described in Section 5.1, ISIS allows the re-generation of the As described in Section 5.1, ISIS allows the re-generation of the
winning FAD from level 2, without any modification to it, into a winning FAD from level 2, without any modification to it, into a
level 1 area. This allows the operator to configure the FAD in one level 1 area. This allows the operator to configure the FAD in one
or multiple routers in the level 2, without the need to repeat the or multiple routers in the level 2, without the need to repeat the
same task in each level 1 area, if the intent is to have the same FAD same task in each level 1 area, if the intent is to have the same FAD
for the particular Flex-Algorithm across all levels. Similar can be for the particular Flex-Algorithm across all levels. This can
achieved in OSPF by using the AS flooding scope of the RI LSA in similarly be achieved in OSPF by using the AS flooding scope of the
which the FAD Sub-TLV for the particular Flex-Algoritm is advertised. RI LSA in which the FAD Sub-TLV for the particular Flex-Algoritm is
advertised.
Re-generation of FAD from level 1 area to level 2 area is not Re-generation of FAD from a level 1 area to the level 2 area is not
supported in ISIS, so if the intent is to regenerate the FAD between supported in ISIS, so if the intent is to regenerate the FAD between
ISIS levels, the FAD MUST be defined on router(s) that are in level ISIS levels, the FAD MUST be defined on router(s) that are in level
2. In OSPF the FAD definition can be done in any area and be 2. In OSPF, the FAD definition can be done in any area and be
propagated to all router in AS by the AS flooding scope of the RI propagated to all routers in the OSPF routing domain by using the AS
LSA. flooding scope of the RI LSA.
14.2. Usage of SRLG Exclude Rule with Flex-Algorithm 14.2. Usage of SRLG Exclude Rule with Flex-Algorithm
There are two different ways in which SRLG information can be used There are two different ways in which SRLG information can be used
with Flex-Algorithm: with Flex-Algorithm:
In a context of a single Flex-Algorithm, it can be used for In a context of a single Flex-Algorithm, it can be used for
computation of backup paths, as described in computation of backup paths, as described in
[I-D.ietf-rtgwg-segment-routing-ti-lfa]. This usage does not [I-D.ietf-rtgwg-segment-routing-ti-lfa]. This usage does not
require association of any specific SRLG constraint with the given require association of any specific SRLG constraint with the given
skipping to change at page 26, line 33 skipping to change at page 26, line 39
link of last resort by setting the TE metric value in the Flex- link of last resort by setting the TE metric value in the Flex-
Algorithm ASLA delay advertisement for the link to the value of (2^24 Algorithm ASLA delay advertisement for the link to the value of (2^24
- 1) in ISIS and (2^32 - 1) in OSPF. - 1) in ISIS and (2^32 - 1) in OSPF.
15. Backward Compatibility 15. Backward Compatibility
This extension brings no new backward compatibility issues. This extension brings no new backward compatibility issues.
16. Security Considerations 16. Security Considerations
This draft adds two new ways to disrupt the IGP networks: This draft adds two new ways to disrupt IGP networks:
An attacker can hijack a particular Flex-Algorithm by advertising An attacker can hijack a particular Flex-Algorithm by advertising
a FAD with a priority of 255 (or any priority higher than that of a FAD with a priority of 255 (or any priority higher than that of
the legitimate nodes). the legitimate nodes).
An attacker could make it look like a router supports a particular An attacker could make it look like a router supports a particular
Flex-Algorithm when it actually doesn't, or vice versa. Flex-Algorithm when it actually doesn't, or vice versa.
Both of these attacks can be addressed by the existing security Both of these attacks can be addressed by the existing security
extensions as described in [RFC5304] and [RFC5310] for ISIS, in extensions as described in [RFC5304] and [RFC5310] for ISIS, in
[RFC2328] and [RFC7474] for OSPFv2 and in [RFC5340] and [RFC4552] for [RFC2328] and [RFC7474] for OSPFv2, and in [RFC5340] and [RFC4552]
OSPFv3. for OSPFv3.
17. IANA Considerations 17. IANA Considerations
17.1. IGP IANA Considerations 17.1. IGP IANA Considerations
17.1.1. IGP Algorithm Types Registry 17.1.1. IGP Algorithm Types Registry
This document makes the following registrations in the "IGP Algorithm This document makes the following registrations in the "IGP Algorithm
Types" registry: Types" registry:
Type: 128-255. Type: 128-255.
Description: Flexible Algorithms. Description: Flexible Algorithms.
skipping to change at page 27, line 37 skipping to change at page 27, line 40
Registry": Registry":
Type: 0 Type: 0
Description: IGP metric Description: IGP metric
Reference: This document (Section 5.1) Reference: This document (Section 5.1)
Type: 1 Type: 1
Description: Min Unidirectional Link Delay [RFC7810] Description: Min Unidirectional Link Delay [RFC8570]
Reference: This document (Section 5.1) Reference: This document (Section 5.1)
Type: 2 Type: 2
Description: TE Default Metric [RFC5305] Description: TE Default Metric [RFC5305]
Reference: This document (Section 5.1) Reference: This document (Section 5.1)
17.2. Flex-Algorithm Definition Flags Registry 17.2. Flexible Algorithm Definition Flags Registry
IANA is requested to set up a registry called "ISIS Flex-Algorithm IANA is requested to set up a registry called "ISIS Flexible
Definition Flags Registry" under a "Interior Gateway Protocol (IGP) Algorithm Definition Flags Registry" under a "Interior Gateway
Parameters" IANA registries. The registration policy for this Protocol (IGP) Parameters" IANA registries. The registration policy
registry is "Standards Action" ([RFC8126] and [RFC7120]). for this registry is "Standards Action" ([RFC8126] and [RFC7120]).
This document defines the following single bit in Flex-Algorithm This document defines the following single bit in Flexible Algorithm
Definition Flags registry: Definition Flags registry:
Bit # Name Bit # Name
----- ------------------------------ ----- ------------------------------
0 Prefix Metric Flag (M-flag) 0 Prefix Metric Flag (M-flag)
Reference: This document (Section 6.4, Section 7.4). Reference: This document (Section 6.4, Section 7.4).
17.3. ISIS IANA Considerations 17.3. ISIS IANA Considerations
skipping to change at page 28, line 36 skipping to change at page 28, line 41
Reference: This document (Section 5.1). Reference: This document (Section 5.1).
17.3.2. Sub TLVs for for TLVs 135, 235, 236, and 237 17.3.2. Sub TLVs for for TLVs 135, 235, 236, and 237
This document makes the following registrations in the "Sub-TLVs for This document makes the following registrations in the "Sub-TLVs for
for TLVs 135, 235, 236, and 237" registry. for TLVs 135, 235, 236, and 237" registry.
Type: 6 Type: 6
Description: Flex-Algorithm Prefix Metric. Description: Flexible Algorithm Prefix Metric.
Reference: This document (Section 8). Reference: This document (Section 8).
17.3.3. Sub-Sub-TLVs for Flexible Algorithm Definition Sub-TLV 17.3.3. Sub-Sub-TLVs for Flexible Algorithm Definition Sub-TLV
This document creates the following Sub-Sub-TLV Registry: This document creates the following Sub-Sub-TLV Registry:
Registry: Sub-Sub-TLVs for Flexible Algorithm Definition Sub-TLV Registry: Sub-Sub-TLVs for Flexible Algorithm Definition Sub-TLV
Registration Procedure: Expert review Registration Procedure: Expert review
skipping to change at page 30, line 12 skipping to change at page 30, line 12
Reference: This document (Section 5.2). Reference: This document (Section 5.2).
17.4.2. OSPFv2 Extended Prefix TLV Sub-TLVs 17.4.2. OSPFv2 Extended Prefix TLV Sub-TLVs
This document makes the following registrations in the "OSPFv2 This document makes the following registrations in the "OSPFv2
Extended Prefix TLV Sub-TLVs" registry. Extended Prefix TLV Sub-TLVs" registry.
Type: 3 Type: 3
Description: Flex-Algorithm Prefix Metric. Description: Flexible Algorithm Prefix Metric.
Reference: This document (Section 9). Reference: This document (Section 9).
17.4.3. OSPFv3 Extended-LSA Sub-TLVs 17.4.3. OSPFv3 Extended-LSA Sub-TLVs
This document makes the following registrations in the "OSPFv3 This document makes the following registrations in the "OSPFv3
Extended-LSA Sub-TLVs" registry. Extended-LSA Sub-TLVs" registry.
Type: 26 Type: 26
Description: Flex-Algorithm Prefix Metric. Description: Flexible Algorithm Prefix Metric.
Reference: This document (Section 9). Reference: This document (Section 9).
17.4.4. OSPF Flexible Algorithm Definition TLV Sub-TLV Registry 17.4.4. OSPF Flexible Algorithm Definition TLV Sub-TLV Registry
This document creates the following registry: This document creates the following registry:
Registry: OSPF Flexible Algorithm Definition TLV sub-TLV Registry: OSPF Flexible Algorithm Definition TLV sub-TLV
Registration Procedure: Expert review Registration Procedure: Expert review
Reference: This document (Section 5.2) Reference: This document (Section 5.2)
The "OSPF Flexible Algorithm Definition TLV sub-TLV" registry will The "OSPF Flexible Algorithm Definition TLV sub-TLV" registry will
define sub-TLVs at any level of nesting for Flexible Algorithm TLV define sub-TLVs at any level of nesting for the Flexible Algorithm
and should be added to the "Open Shortest Path First (OSPF) TLV and should be added to the "Open Shortest Path First (OSPF)
Parameters" registries group. New values can be allocated via IETF Parameters" registries group. New values can be allocated via IETF
Review or IESG Approval. Review or IESG Approval.
This document registers following Sub-TLVs in the "TLVs for Flexible This document registers following Sub-TLVs in the "TLVs for Flexible
Algorithm Definition TLV" registry: Algorithm Definition TLV" registry:
Type: 1 Type: 1
Description: Flexible Algorithm Exclude Admin Group Description: Flexible Algorithm Exclude Admin Group
skipping to change at page 32, line 15 skipping to change at page 32, line 15
Thanks to Eric Rosen, Tony Przygienda for their detailed review and Thanks to Eric Rosen, Tony Przygienda for their detailed review and
excellent comments. excellent comments.
Thanks to Cengiz Halit for his review and feedback during initial Thanks to Cengiz Halit for his review and feedback during initial
phase of the solution definition. phase of the solution definition.
Thanks to Kenji Kumaki for his comments. Thanks to Kenji Kumaki for his comments.
Thanks to William Britto A J. for his suggestions. Thanks to William Britto A J. for his suggestions.
Thanks to Acee Lindem for editorial comments.
19. References 19. References
19.1. Normative References 19.1. Normative References
[BCP14] , <https://tools.ietf.org/html/bcp14>. [BCP14] , <https://tools.ietf.org/html/bcp14>.
[I-D.ietf-isis-te-app] [I-D.ietf-isis-te-app]
Ginsberg, L., Psenak, P., Previdi, S., Henderickx, W., and Ginsberg, L., Psenak, P., Previdi, S., Henderickx, W., and
J. Drake, "IS-IS Application-Specific Link Attributes", J. Drake, "IS-IS Application-Specific Link Attributes",
draft-ietf-isis-te-app-19 (work in progress), June 2020. draft-ietf-isis-te-app-19 (work in progress), June 2020.
skipping to change at page 35, line 31 skipping to change at page 35, line 31
[RFC7120] Cotton, M., "Early IANA Allocation of Standards Track Code [RFC7120] Cotton, M., "Early IANA Allocation of Standards Track Code
Points", BCP 100, RFC 7120, DOI 10.17487/RFC7120, January Points", BCP 100, RFC 7120, DOI 10.17487/RFC7120, January
2014, <https://www.rfc-editor.org/info/rfc7120>. 2014, <https://www.rfc-editor.org/info/rfc7120>.
[RFC7474] Bhatia, M., Hartman, S., Zhang, D., and A. Lindem, Ed., [RFC7474] Bhatia, M., Hartman, S., Zhang, D., and A. Lindem, Ed.,
"Security Extension for OSPFv2 When Using Manual Key "Security Extension for OSPFv2 When Using Manual Key
Management", RFC 7474, DOI 10.17487/RFC7474, April 2015, Management", RFC 7474, DOI 10.17487/RFC7474, April 2015,
<https://www.rfc-editor.org/info/rfc7474>. <https://www.rfc-editor.org/info/rfc7474>.
[RFC7810] Previdi, S., Ed., Giacalone, S., Ward, D., Drake, J., and
Q. Wu, "IS-IS Traffic Engineering (TE) Metric Extensions",
RFC 7810, DOI 10.17487/RFC7810, May 2016,
<https://www.rfc-editor.org/info/rfc7810>.
[RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for [RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for
Writing an IANA Considerations Section in RFCs", BCP 26, Writing an IANA Considerations Section in RFCs", BCP 26,
RFC 8126, DOI 10.17487/RFC8126, June 2017, RFC 8126, DOI 10.17487/RFC8126, June 2017,
<https://www.rfc-editor.org/info/rfc8126>. <https://www.rfc-editor.org/info/rfc8126>.
[RFC8570] Ginsberg, L., Ed., Previdi, S., Ed., Giacalone, S., Ward,
D., Drake, J., and Q. Wu, "IS-IS Traffic Engineering (TE)
Metric Extensions", RFC 8570, DOI 10.17487/RFC8570, March
2019, <https://www.rfc-editor.org/info/rfc8570>.
Authors' Addresses Authors' Addresses
Peter Psenak (editor) Peter Psenak (editor)
Cisco Systems Cisco Systems
Apollo Business Center Apollo Business Center
Mlynske nivy 43 Mlynske nivy 43
Bratislava, 82109 Bratislava, 82109
Slovakia Slovakia
Email: ppsenak@cisco.com Email: ppsenak@cisco.com
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