Inter-Domain Routing K. Talaulikar, Ed.
Internet-Draft Arrcus, Inc
Intended status: Standards Track P. Psenak
Expires: 26 February 2023 Cisco Systems
S. Zandi
G. Dawra
LinkedIn
25 August 2022
Flexible Algorithm Advertisement using BGP Link-State
draft-ietf-idr-bgp-ls-flex-algo-12
Abstract
Flexible Algorithm is a solution that allows some routing protocols
(e.g., OSPF and IS-IS) to compute paths over a network based on user-
defined (and hence, flexible) constraints and metrics. The
computation is performed by routers participating in the specific
network in a distributed manner using a Flexible Algorithm
Definition. This Definition is provisioned on one or more routers
and propagated through the network by OSPF and IS-IS flooding.
BGP Link-State (BGP-LS) enables the collection of various topology
information from the network. This document defines extensions to
the BGP-LS address family to advertise the Flexible Algorithm
Definition as a part of the topology information from the network.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on 26 February 2023.
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Copyright Notice
Copyright (c) 2022 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents (https://trustee.ietf.org/
license-info) in effect on the date of publication of this document.
Please review these documents carefully, as they describe your rights
and restrictions with respect to this document. Code Components
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provided without warranty as described in the Revised BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 4
2. Overview of BGP-LS Extensions for Flexible Algorithm . . . . 4
3. Flexible Algorithm Definition TLV . . . . . . . . . . . . . . 4
3.1. Flexible Algorithm Exclude Any Affinity Sub-TLV . . . . . 6
3.2. Flexible Algorithm Include Any Affinity Sub-TLV . . . . . 6
3.3. Flexible Algorithm Include All Affinity Sub-TLV . . . . . 7
3.4. Flexible Algorithm Definition Flags Sub-TLV . . . . . . . 8
3.5. Flexible Algorithm Exclude SRLG Sub-TLV . . . . . . . . . 9
3.6. Flexible Algorithm Unsupported Sub-TLV . . . . . . . . . 10
4. Flexible Algorithm Prefix Metric TLV . . . . . . . . . . . . 11
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12
6. Manageability Considerations . . . . . . . . . . . . . . . . 13
7. Security Considerations . . . . . . . . . . . . . . . . . . . 13
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 14
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 14
9.1. Normative References . . . . . . . . . . . . . . . . . . 14
9.2. Informative References . . . . . . . . . . . . . . . . . 15
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 16
1. Introduction
The classical IGP (e.g., OSPF and IS-IS) computation of best paths
over the network is based on the IGP metric assigned to the links in
the network. Many network deployments use RSVP-TE-based [RFC3209] or
Segment Routing (SR) Policy-based [RFC8402] solutions to enforce
traffic over a path that is computed using different metrics or
constraints than the shortest IGP path. [I-D.ietf-lsr-flex-algo]
defines the Flexible Algorithm solution that allows IGPs themselves
to compute constraint based paths over the network.
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Flexible Algorithm is so called because it allows a user the
flexibility to define
* the type of calculation to be used (e.g., shortest path)
* the metric type to be used (e.g., IGP metric or TE metric)
* the set of constraints to be used (e.g., inclusion or exclusion of
certain links using affinities)
The operations of the IGP flexible algorithm solution are described
in detail in [I-D.ietf-lsr-flex-algo].
The BGP-LS extensions for SR are defined in [RFC9085] and
[I-D.ietf-idr-bgpls-srv6-ext] for SR-MPLS and Segment Routing over
IPv6 (SRv6), respectively. They include the extensions for
advertisement of SR information including various types of Segment
Identifiers (SIDs) as below:
* SR Algorithm TLV to indicate the participation of a node in a
flexible algorithm computation
* Prefix-SID TLV to indicate the association of the Prefix-SIDs to a
specific flexible algorithm for SR-MPLS forwarding
* SRv6 Locator TLV to indicate the Locator for specific flexible
algorithm for SRv6 forwarding
This document defines extensions to BGP-LS for the advertisement of
the Flexible Algorithm Definition (FAD) information to enable
learning of the mapping of the flexible algorithm number to its
Definition in each area/domain of the underlying IGP. This
Definition indicates the type of computation used and the constraints
for a given flexible algorithm. This information can then be used
for setting up SR Policy paths end to end across domains by using the
appropriate flexible algorithm-specific SIDs in its Segment List
[RFC9256]. For example, picking the flexible algorithm Prefix SID
(in case of SR-MPLS) or End SID (in case of SRv6) of Area Border
Routers (ABRs) or Autonomous System Border Routers (ASBRs)
corresponding to a Definition that optimizes on the delay metric
enables the building of an end to end low latency path across IGP
domains with minimal SIDs in the SID list.
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1.1. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
2. Overview of BGP-LS Extensions for Flexible Algorithm
BGP-LS [RFC7752] specifies the Node Network Layer Reachability
Information (NLRI) for the advertisement of nodes along with their
attributes using the BGP-LS Attribute, the Link NLRI for the
advertisement of links along with their attributes using the BGP-LS
Attribute and the Prefix NLRI for the advertisement of prefixes along
with their attributes using the BGP-LS Attribute.
The FADs advertised by a node are considered as a node-level
attribute and advertised as specified in Section 3.
Various link attributes like affinities and Shared Risk Link Group
(SRLG) that are used during the Flexible Algorithm route calculations
in IS-IS and OSPF are advertised in those protocols using the
Application Specific Link Attribute (ASLA) advertisements as
described in [RFC8919], [RFC8920], and [I-D.ietf-lsr-flex-algo]. The
BGP-LS extensions for ASLA advertisements are specified in [RFC9294].
The Flexible Algorithm Prefix Metric (FAPM) is considered as a prefix
attribute and advertised as specified in Section 4.
3. Flexible Algorithm Definition TLV
This document defines a new optional BGP-LS Attribute TLV associated
with the Node NLRI called the Flexible Algorithm Definition (FAD) TLV
and its format is as follows:
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flex Algo | Metric-Type | Calc-Type | Priority |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| sub-TLVs ... //
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: Flexible Algorithm Definition TLV
where:
* Type: 1039
* Length: The total length of the value field (including any sub-
TLVs) in octets. The length value MUST be 4 or larger.
* Flexible Algorithm (Flex Algo): Single octet value carrying the
flexible algorithm number between 128 and 255 inclusive, as
defined in [I-D.ietf-lsr-flex-algo].
* Metric-Type: Single octet value carrying the metric type, as
defined in [I-D.ietf-lsr-flex-algo].
* Calc-Type: Single octet value carrying the calculation type, as
defined in [I-D.ietf-lsr-flex-algo].
* Priority: Single octet value carrying the priority of the FAD
advertisement, as defined in [I-D.ietf-lsr-flex-algo].
* sub-TLVs: zero or more sub-TLVs may be included as described
further in this section.
The FAD TLV that is advertised in the BGP-LS Attribute along with the
Node NLRI of a node is derived from the following IGP protocol-
specific advertisements:
* In the case of IS-IS, from the IS-IS Flexible Algorithm Definition
sub-TLV in [I-D.ietf-lsr-flex-algo].
* In the case of OSPFv2/OSPFv3, from the OSPF Flexible Algorithm
Definition TLV in [I-D.ietf-lsr-flex-algo].
The BGP-LS Attribute associated with a Node NLRI may include one or
more FAD TLVs corresponding to the FAD for each algorithm that the
particular node is advertising.
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The following sub-sections define sub-TLVs of the FAD TLV.
3.1. Flexible Algorithm Exclude Any Affinity Sub-TLV
The Flexible Algorithm Exclude Any Affinity sub-TLV is an optional
sub-TLV that is used to carry the affinity constraints associated
with the FAD and enable the exclusion of links carrying any of the
specified affinities from the computation of the specific algorithm
as described in [I-D.ietf-lsr-flex-algo]. The affinity is expressed
in terms of Extended Admin Group (EAG) as defined in [RFC7308].
The sub-TLV has the following format:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Exclude-Any EAG (variable) //
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: Flexible Algorithm Exclude Any Affinity sub-TLV
where:
* Type: 1040
* Length: The total length of the value field in octets dependent on
the size of the EAG. It MUST be a non-zero value and a multiple
of 4.
* Exclude-Any EAG: the EAG value as defined in
[I-D.ietf-lsr-flex-algo].
The information in the Flexible Algorithm Exclude Any Affinity sub-
TLV is derived from the IS-IS and OSPF protocol-specific Flexible
Algorithm Exclude Admin Group sub-TLV as defined in
[I-D.ietf-lsr-flex-algo].
3.2. Flexible Algorithm Include Any Affinity Sub-TLV
The Flexible Algorithm Include Any Affinity sub-TLV is an optional
sub-TLV that is used to carry the affinity constraints associated
with the FAD and enable the inclusion of links carrying any of the
specified affinities in the computation of the specific algorithm as
described in [I-D.ietf-lsr-flex-algo]. The affinity is expressed in
terms of Extended Admin Group (EAG) as defined in [RFC7308].
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The sub-TLV has the following format:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Include-Any EAG (variable) //
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3: Flexible Algorithm Include Any Affinity sub-TLV
where:
* Type: 1041
* Length: The total length of the value field in octets dependent on
the size of the EAG. It MUST be a non-zero value and a multiple
of 4.
* Include-Any EAG: the EAG value as defined in
[I-D.ietf-lsr-flex-algo].
The information in the Flexible Algorithm Include Any Affinity sub-
TLV is derived from the IS-IS and OSPF protocol-specific Flexible
Algorithm Include-Any Admin Group sub-TLV as defined in
[I-D.ietf-lsr-flex-algo].
3.3. Flexible Algorithm Include All Affinity Sub-TLV
The Flexible Algorithm Include All Affinity sub-TLV is an optional
sub-TLV that is used to carry the affinity constraints associated
with the FAD and enable the inclusion of links carrying all of the
specified affinities in the computation of the specific algorithm as
described in [I-D.ietf-lsr-flex-algo]. The affinity is expressed in
terms of Extended Admin Group (EAG) as defined in [RFC7308].
The sub-TLV has the following format:
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Include-All EAG (variable) //
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 4: Flexible Algorithm Include All Affinity sub-TLV
where:
* Type: 1042
* Length: The total length of the value field in octets dependent on
the size of the EAG. It MUST be a non-zero value and a multiple
of 4.
* Include-All EAG: the EAG value as defined in
[I-D.ietf-lsr-flex-algo].
The information in the Flexible Algorithm Include All Affinity sub-
TLV is derived from the IS-IS and OSPF protocol-specific Flexible
Algorithm Include-All Admin Group sub-TLV as defined in
[I-D.ietf-lsr-flex-algo].
3.4. Flexible Algorithm Definition Flags Sub-TLV
The Flexible Algorithm Definition Flags sub-TLV is an optional sub-
TLV that is used to carry the flags associated with the FAD that are
used in the computation of the specific algorithm as described in
[I-D.ietf-lsr-flex-algo].
The sub-TLV has the following format:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags (variable) //
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 5: Flexible Algorithm Definition Flags sub-TLV
where:
* Type: 1043
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* Length: The total length of the value field in octets dependent on
the size of the Flags. It MUST be a non-zero value and a multiple
of 4.
* Flags: the bitmask used to represent the flags for the FAD, as
defined in [I-D.ietf-lsr-flex-algo].
The information in the Flexible Algorithm Definition Flags sub-TLV is
derived from the IS-IS and OSPF protocol-specific Flexible Algorithm
Definition Flags sub-TLV as defined in [I-D.ietf-lsr-flex-algo].
3.5. Flexible Algorithm Exclude SRLG Sub-TLV
The Flexible Algorithm Exclude SRLG sub-TLV is an optional sub-TLV
that is used to carry the Shared Risk Link Group (SRLG) information
associated with the FAD and enable the exclusion of links that are
associated with any of the specified SRLG in the computation of the
specific algorithm as described in [I-D.ietf-lsr-flex-algo]. The
SRLGs associated with a link are carried in the BGP-LS Shared Link
Risk Group (TLV 1096) [RFC7752].
The sub-TLV has the following format:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Shared Risk Link Group Values (variable) //
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 6: Flexible Algorithm Exclude SRLG sub-TLV
where:
* Type: 1045
* Length: The total length of the value field in octets dependent on
the number of SRLG values carried. It MUST be a non-zero value
and a multiple of 4.
* Shared Risk Link Group Values: One or more SRLG values, each of 4
octet size, as defined in [I-D.ietf-lsr-flex-algo].
The information in the Flexible Algorithm SRLG Exclude sub-TLV is
derived from the IS-IS and OSPF protocol-specific Flexible Algorithm
Exclude SRLG sub-TLV as defined in [I-D.ietf-lsr-flex-algo].
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3.6. Flexible Algorithm Unsupported Sub-TLV
The OSPF and IS-IS signaling for FAD allows for extensions via new
sub-TLVs under the respective IGP's Flexible Algorithm Definition
TLV. As specified in section 5.3 of [I-D.ietf-lsr-flex-algo], it is
important that the entire FAD be understood by anyone using it for
computation purpose. Therefore, the FAD is different from most other
protocol extensions where the skipping or ignoring of unsupported
sub-TLV information does not affect the base behavior.
The Flexible Algorithm Unsupported sub-TLV is an optional sub-TLV
that is used to indicate the presence of unsupported FAD sub-TLVs.
The need for this sub-TLV arises when the BGP-LS implementation on
the advertising node does not support one or more of the FAD sub-TLVs
present in the IGP advertisement.
The sub-TLV has the following format:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Protocol-ID | sub-TLV types (variable) ... //
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 7: Flexible Algorithm Unsupported sub-TLV
where:
* Type: TBD (Note to Editor: The code point allocation, once made by
IANA, needs to be updated here - refer to Section 5)
* Length: The total length of the value field in octets (including
any included sub-TLV types).
* Protocol-ID: Indicates the BGP-LS Protocol-ID of the protocol from
which the FAD is being advertised via BGP-LS. The values are from
the "BGP-LS Protocol-IDs" registry
<https://www.iana.org/assignments/bgp-ls-parameters/bgp-ls-
parameters.xhtml#protocol-ids> under the IANA BGP-LS Parameters
registry.
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* sub-TLV types: Zero or more sub-TLV types that are not supported
by the node originating the BGP-LS advertisement. The size of
each sub-TLV type depends on the protocol indicated by the
Protocol-ID field. For example, for IS-IS each sub-TLV type would
be of size 1 octet while for OSPF each sub-TLV type would be of
size 2 octets.
The node originating the advertisement MUST include the Flexible
Algorithm Unsupported sub-TLV when it comes across an unsupported
sub-TLV in the corresponding FAD in the IS-IS and OSPF advertisement.
When advertising the Flexible Algorithm Unsupported sub-TLV, the
protocol-specific sub-TLV types that are not supported SHOULD be
included. This information serves as a diagnostic aid.
The discussion on the use of the FAD information by the consumers of
the BGP-LS information is beyond the scope of this document.
However, it is RECOMMENDED that the choice of the node used for
originating the IGP topology information into BGP-LS be made such
that the advertising node supports all the FAD extensions in use in
its part of the network. This avoids the scenario where an
incomplete FAD gets advertised via BGP-LS.
4. Flexible Algorithm Prefix Metric TLV
This document defines a new optional BGP-LS Attribute TLV associated
with the Prefix NLRI called the Flexible Algorithm Prefix Metric
(FAPM) TLV and its format is as follows:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flex Algo | Flags | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Metric |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 8: Flexible Algorithm Prefix Metric TLV
where:
* Type: 1044
* Length: 8 octets.
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* Flexible Algorithm (Flex Algo): Single octet value carrying the
flexible algorithm number between 128 and 255 inclusive, as
defined in [I-D.ietf-lsr-flex-algo].
* Flags: single octet value and only applicable for OSPF as defined
in [I-D.ietf-lsr-flex-algo]. The value MUST be set to 0 for IS-
IS.
* Reserved: 2 octet value that MUST be set to 0 by the originator
and MUST be ignored by the receiver.
* Metric: 4 octets field to carry the metric information.
The FAPM TLV that is advertised in the BGP-LS Attribute along with
the Prefix NLRI from a node is derived from the following IGP
protocol-specific advertisements:
* In the case of IS-IS, from the IS-IS Flexible Algorithm Prefix
Metric sub-TLV in [I-D.ietf-lsr-flex-algo].
* In the case of OSPFv2/OSPFv3, from the OSPF Flexible Algorithm
Prefix Metric sub-TLV in [I-D.ietf-lsr-flex-algo].
The BGP-LS Attribute associated with a Prefix NLRI may include one or
more FAPM TLVs corresponding to the Flexible Algorithm Prefix Metric
for each algorithm associated with that particular prefix.
5. IANA Considerations
IANA has allocated code points from the registry "BGP-LS Node
Descriptor, Link Descriptor, Prefix Descriptor, and Attribute TLVs"
<https://www.iana.org/assignments/bgp-ls-parameters/bgp-ls-
parameters.xhtml#node-descriptor-link-descriptor-prefix-descriptor-
attribute-tlv> based on the table below for the TLVs/sub-TLVs
introduced by this document. This document requests IANA to allocate
the pending code point for the Flexible Algorithm Unsupported sub-TLV
as suggested below. The column "IS-IS TLV/Sub-TLV" defined in the
registry does not require any value and should be left empty.
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+------------+-----------------------------------------+
| Code Point | Description |
+------------+-----------------------------------------+
| 1039 | Flexible Algorithm Definition |
| 1040 | Flexible Algorithm Exclude Any Affinity |
| 1041 | Flexible Algorithm Include Any Affinity |
| 1042 | Flexible Algorithm Include All Affinity |
| 1043 | Flexible Algorithm Definition Flags |
| 1044 | Flexible Algorithm Prefix Metric |
| 1045 | Flexible Algorithm Exclude SRLG |
| 1046 (Sugg)| Flexible Algorithm Unsupported |
+------------+-----------------------------------------+
Table 1: Flexible Algorithm Code Points
6. Manageability Considerations
The new protocol extensions introduced in this document augment the
existing IGP topology information that can be distributed via
[RFC7752]. Procedures and protocol extensions defined in this
document do not affect the BGP protocol operations and management
other than as discussed in the Manageability Considerations section
of [RFC7752]. Specifically, the malformed NLRIs attribute tests in
the Fault Management section of [RFC7752] now encompass the new TLVs
for the BGP-LS NLRI in this document.
The extensions specified in this document do not specify any new
configuration or monitoring aspects in BGP or BGP-LS. The
specification of BGP models is an ongoing work based on
[I-D.ietf-idr-bgp-model].
7. Security Considerations
Security considerations for acquiring and distributing BGP-LS
information are discussed in [RFC7752].
The TLVs introduced in this document are used to propagate the IGP
Flexible Algorithm extensions defined in [I-D.ietf-lsr-flex-algo].
It is assumed that the IGP instances originating these TLVs will
support all the required security (as described in
[I-D.ietf-lsr-flex-algo]) for Flexible Algorithm deployment.
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This document specifies extensions for the advertisement of node and
prefix related flexible algorithm information. Tampering with this
flexible algorithm-related information may affect applications using
it, including impacting route calculation and programming. As the
advertisements defined in this document are related to a specific
flexible algorithm topology, the impact of tampering is similarly
limited in scope.
8. Acknowledgements
The authors would like to thank Les Ginsberg, Amalesh Maity, Y F Siu,
Vijay Gurbani, and Donald Eastlake III for their reviews and
contributions to this work. The authors would like to thank Jie Dong
for his shepherd review. The authors would like to thank Alvaro
Retana for his detailed AD review and suggestions for improving this
document.
9. References
9.1. Normative References
[I-D.ietf-lsr-flex-algo]
Psenak, P., Hegde, S., Filsfils, C., Talaulikar, K., and
A. Gulko, "IGP Flexible Algorithm", Work in Progress,
Internet-Draft, draft-ietf-lsr-flex-algo-20, 18 May 2022,
<https://www.ietf.org/archive/id/draft-ietf-lsr-flex-algo-
20.txt>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC7308] Osborne, E., "Extended Administrative Groups in MPLS
Traffic Engineering (MPLS-TE)", RFC 7308,
DOI 10.17487/RFC7308, July 2014,
<https://www.rfc-editor.org/info/rfc7308>.
[RFC7752] Gredler, H., Ed., Medved, J., Previdi, S., Farrel, A., and
S. Ray, "North-Bound Distribution of Link-State and
Traffic Engineering (TE) Information Using BGP", RFC 7752,
DOI 10.17487/RFC7752, March 2016,
<https://www.rfc-editor.org/info/rfc7752>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
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9.2. Informative References
[I-D.ietf-idr-bgp-model]
Jethanandani, M., Patel, K., Hares, S., and J. Haas, "BGP
YANG Model for Service Provider Networks", Work in
Progress, Internet-Draft, draft-ietf-idr-bgp-model-14, 3
July 2022, <https://www.ietf.org/archive/id/draft-ietf-
idr-bgp-model-14.txt>.
[I-D.ietf-idr-bgpls-srv6-ext]
Dawra, G., Filsfils, C., Talaulikar, K., Chen, M.,
Bernier, D., and B. Decraene, "BGP Link State Extensions
for SRv6", Work in Progress, Internet-Draft, draft-ietf-
idr-bgpls-srv6-ext-09, 10 November 2021,
<https://www.ietf.org/archive/id/draft-ietf-idr-bgpls-
srv6-ext-09.txt>.
[RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V.,
and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP
Tunnels", RFC 3209, DOI 10.17487/RFC3209, December 2001,
<https://www.rfc-editor.org/info/rfc3209>.
[RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L.,
Decraene, B., Litkowski, S., and R. Shakir, "Segment
Routing Architecture", RFC 8402, DOI 10.17487/RFC8402,
July 2018, <https://www.rfc-editor.org/info/rfc8402>.
[RFC8919] Ginsberg, L., Psenak, P., Previdi, S., Henderickx, W., and
J. Drake, "IS-IS Application-Specific Link Attributes",
RFC 8919, DOI 10.17487/RFC8919, October 2020,
<https://www.rfc-editor.org/info/rfc8919>.
[RFC8920] Psenak, P., Ed., Ginsberg, L., Henderickx, W., Tantsura,
J., and J. Drake, "OSPF Application-Specific Link
Attributes", RFC 8920, DOI 10.17487/RFC8920, October 2020,
<https://www.rfc-editor.org/info/rfc8920>.
[RFC9085] Previdi, S., Talaulikar, K., Ed., Filsfils, C., Gredler,
H., and M. Chen, "Border Gateway Protocol - Link State
(BGP-LS) Extensions for Segment Routing", RFC 9085,
DOI 10.17487/RFC9085, August 2021,
<https://www.rfc-editor.org/info/rfc9085>.
[RFC9256] Filsfils, C., Talaulikar, K., Ed., Voyer, D., Bogdanov,
A., and P. Mattes, "Segment Routing Policy Architecture",
RFC 9256, DOI 10.17487/RFC9256, July 2022,
<https://www.rfc-editor.org/info/rfc9256>.
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[RFC9294] Talaulikar, K., Ed., Psenak, P., and J. Tantsura,
"Application-Specific Link Attributes Advertisement Using
the Border Gateway Protocol - Link State (BGP-LS)",
RFC 9294, DOI 10.17487/RFC9294, August 2022,
<https://www.rfc-editor.org/info/rfc9294>.
Authors' Addresses
Ketan Talaulikar (editor)
Arrcus, Inc
India
Email: ketant.ietf@gmail.com
Peter Psenak
Cisco Systems
Slovakia
Email: ppsenak@cisco.com
Shawn Zandi
LinkedIn
United States of America
Email: szandi@linkedin.com
Gaurav Dawra
LinkedIn
United States of America
Email: gdawra.ietf@gmail.com
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