LSR Working Group W. Britto
Internet-Draft S. Hegde
Intended status: Standards Track P. Kaneriya
Expires: May 19, 2021 R. Shetty
R. Bonica
Juniper Networks
P. Psenak
Cisco Systems
November 15, 2020
IGP Flexible Algorithms (Flex-Algorithm) In IP Networks
draft-bonica-lsr-ip-flexalgo-01
Abstract
An IGP Flexible Algorithm (Flex-Algorithm) allows IGP to compute
constraint-based paths. As currently defined, IGP Flex-Algorithm is
used with Segment Routing (SR) data planes - SR MPLS and SRv6.
Therefore, Flex-Algorithm cannot be deployed in the absence of SR.
This document extends IGP Flex-Algorithm, so that it can be used for
regular IPv4 and IPv6 prefixes. This allows Flex-Algorithm to be
deployed in any IP network, even in the absence of SR.
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 May 19, 2021.
Copyright Notice
Copyright (c) 2020 IETF Trust and the persons identified as the
document authors. All rights reserved.
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This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
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described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Requirements Language . . . . . . . . . . . . . . . . . . . . 3
3. Egress Node Procedures . . . . . . . . . . . . . . . . . . . 3
4. Advertising Flex-Algorithm Definitions (FAD) . . . . . . . . 3
5. Advertising IP Flex-Algorithm Participation . . . . . . . . . 3
5.1. The ISIS IP Algorithm Sub-TLV . . . . . . . . . . . . . . 4
5.2. The OSPF IP Algorithm TLV . . . . . . . . . . . . . . . . 5
6. Advertising IP Flex-Algorthm Reachability . . . . . . . . . . 6
6.1. The ISIS IPv4 Algorithm Prefix Reachability TLV . . . . . 6
6.2. The ISIS IPv6 Algorithm Prefix Reachability TLV . . . . . 8
6.3. The OSPFv2 Algorithm Prefix Reachability TLV . . . . . . 9
6.4. The OSPFv3 Flex-Algorithm IP Prefix Opaque LSA . . . . . 11
7. Calculating of IP Flex-Algorthm Paths . . . . . . . . . . . . 11
8. IP Flex-Algorthm Forwarding . . . . . . . . . . . . . . . . . 12
9. Deployment Considerations . . . . . . . . . . . . . . . . . . 12
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13
11. Security Considerations . . . . . . . . . . . . . . . . . . . 14
12. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 14
13. References . . . . . . . . . . . . . . . . . . . . . . . . . 14
13.1. Normative References . . . . . . . . . . . . . . . . . . 14
13.2. Informative References . . . . . . . . . . . . . . . . . 15
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 16
1. Introduction
An IGP Flex-Algorithm as specified in [I-D.ietf-lsr-flex-algo]
computes a constraint-based path to:
o All Flex-Algorithm specific Prefix Segment Identifiers (SIDs)
[RFC8402].
o All Flex-Algorityhm specific SRv6 Locators
[I-D.ietf-spring-srv6-network-programming].
Therefore, Flex-Algorithm cannot be deployed in the absence of SR and
SRv6.
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This document extends Flex-Algorithm, allowing it to compute paths
to:
o An IPv4 [RFC0791] address.
o An IPv6 [RFC8200] address.
This allows Flex-Algorithm to be deployed in any IP network, even in
the absence of SR and SRv6.
2. 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.
3. Egress Node Procedures
Network operators configure multiple loopback interfaces on an egress
node. They associate one or more IP addresses with each loopback
interface and one Flex-Algorithm with each IP address.
If a packet is sent to a loopback address, and the loopback address
is not associated with a Flex-Algorithm, the packet follows the IGP
least-cost path to the egress node. If a packet is sent to a
loopback address, and the loopback address is associated with a Flex-
Algorithm, the packet follows the constraint-base path that the Flex-
Algorithm calculated.
4. Advertising Flex-Algorithm Definitions (FAD)
To guarantee loop free forwarding, all routers that participate in a
Flex-Algorithm MUST agree on the Flex-Algorithm Definition (FAD).
Selected nodes within the IGP domain MUST advertise FADs as described
in Sections 5, 6 and 7 of [I-D.ietf-lsr-flex-algo].
5. Advertising IP Flex-Algorithm Participation
A node may use various algorithms when calculating paths to nodes and
prefixes. Algorithm values are defined in the IGP Algorithm Type
Registry [IANA-ALG].
A node MUST participate in a Flex-Algorithm to be:
o able to compute path for such Flex-Algorithm
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o be part of the topology for such Flex-Algorithm
Flex-Algorithm participation MUST be advertised for each Flex-
Algorithm application independently, as specified in Section 10.2 of
[I-D.ietf-lsr-flex-algo]. Using Flex-Algorithm for regular IPv4 and
IPv6 prefixes represents a new Flex-Algorithm application (IP Flex-
Algorithm), and as such the Flex-Algorithm participation for the IP
Flex-Algorithm application MUST be signalled independently of any
other Flex-Algorithm applications (e.g. SR).
Following sections describe how the IP Flex-Algorithm participation
is advertised in IGP protocols.
5.1. The ISIS IP Algorithm Sub-TLV
The ISIS IP Algorithm Sub-TLV is a sub-TLV of the ISIS Router
Capability TLV [RFC7981] and 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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Algorithm 1 | Algorithm 2 | Algorithm ... | Algorithm n |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: ISIS IP Algorithm Sub-TLV
o Type: IP Algorithm Sub-TLV (Value TBD by IANA)
o Length: Variable
o Algorithm (1 octet): value from 1 to 255.
The IP Algorithm Sub-TLV MUST be propagated throughout the level and
MUST NOT be advertised across level boundaries. Therefore, the S bit
in the Router Capability TLV, in which the IP Algorithm Sub-TLV is
advertised, MUST NOT be set.
The IP Algorithm Sub-TLV is optional. It MUST NOT be advertised more
than once at a given level. A router receiving multiple IP Algorithm
sub-TLVs from the same originator SHOULD select the first
advertisement in the lowest-numbered LSP and subsequent instances of
the IP Algorithm Sub-TLV MUST be ignored.
The IP Algorithm Sub-TLV advertises the participation in Flex-
Algorithms, and MUST NOT impact the router participation in default
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algorithm 0. The IP Algorithm Sub-TLV could be used to advertise
support for non-zero standard algorithms, but that is outside the
scope of this document.
The IP Flex-Algorithm participation advertised in ISIS IP Algorithm
Sub-TLV is topology independent. When a router advertises
participation in ISIS IP Algorithm Sub-TLV, the participation applies
to all topologies in which the advertising node participates.
5.2. The OSPF IP Algorithm TLV
The OSPF IP Algorithm TLV is a top-level TLV of the Router
Information Opaque LSA [RFC7770] and 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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Algorithm 1 | Algorithm... | Algorithm n | |
+- -+
| |
+ +
Figure 2: OSPF IP Algorithm TLV
o Type: IP Algorithm TLV (Value TBD by IANA)
o Length: Variable
o Algorithm (1 octet): value from 1 to 255.
The IP Algorithm TLV is optional. It SHOULD only be advertised once
in the Router Information Opaque LSA.
When multiple IP Algorithm TLVs are received from a given router, the
receiver MUST use the first occurrence of the TLV in the Router
Information Opaque LSA. If the IP Algorithm TLV appears in multiple
Router Information Opaque LSAs that have different flooding scopes,
the IP Algorithm TLV in the Router Information Opaque LSA with the
area-scoped flooding scope MUST be used. If the IP Algorithm TLV
appears in multiple Router Information Opaque LSAs that have the same
flooding scope, the IP Algorithm TLV in the Router Information (RI)
Opaque LSA with the numerically smallest Instance ID MUST be used and
subsequent instances of the IP Algorithm TLV MUST be ignored.
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The RI LSA can be advertised at any of the defined opaque flooding
scopes (link, area, or Autonomous System (AS)). For the purpose of
IP Algorithm TLV advertisement, area-scoped flooding is REQUIRED.
The IP Algorithm TLV advertises the participation in Flex-Algorithms,
and MUST NOT impact the router participation in default algorithm 0.
The IP Algorithm TLV could be used to advertise support for non-zero
standard algorithms, but that is outside the scope of this document.
The IP Flex-Algorithm participation advertised in OSPF IP Algorithm
TLV is topology independent. When a router advertises participation
in OSPF IP Algorithm TLV, the participation applies to all topologies
in which the advertising node participates.
6. Advertising IP Flex-Algorthm Reachability
To be able to associate the prefix with the Flex-Algorithm, the
existing prefix reachability advertisements can not be used, because
they advertise the prefix reachability in default algorithm 0.
Instead, a new IP Flex-Algorithm reachability advertisements are
defined in ISIS and OSPF.
Two new top-level TLVs are defined in ISIS [ISO10589] to advertise
prefix reachability associated with a Flex-Algorithm.
o The IPv4 Algorithm Prefix Reachability TLV
o The IPv6 Algorithm Prefix Reachability TLV
New top-level TLV of OSPFv2 Extended Prefix Opaque LSA [RFC7684] is
defined to advertise prefix reachability associated with a Flex-
Algorithm in OSPFv2.
6.1. The ISIS IPv4 Algorithm Prefix Reachability TLV
A new top level TLV is defined for advertising IPv4 Flex-Algorithm
Prefix Reachability in ISIS - IPv4 Algorithm Prefix Reachability TLV.
This new TLV shares the sub-TLV space defined for TLVs 135, 235, 236
and 237.
The ISIS IPv4 Algorithm Prefix Reachability 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 |R|R|R|R| MTID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
ISIS IPv4 Algorithm Prefix Reachability TLV
o Type: IPv4 Algorithm Prefix Reachability TLV (Value TBD by IANA).
o Length: variable.
o R bits (4 bits): reserved for future use. They MUST be set to
zero on transmission and MUST be ignored on receipt.
o MTID (12 bits): Multitopology Identifier as defined in [RFC5120].
Note that the value 0 is legal.
Followed by one or more prefix entries of the form:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Metric |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags | Algorithm |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Pfx Length | Prefix (variable)...
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sub-tlv-len | Sub-TLVs (variable) . . . |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
ISIS IPv4 Algorithm Prefix Reachability TLV
o Metric (4 octets): Metric information.
o Flags (1 octet):
0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+
|D|S| | |
+-+-+-+-+-+-+-+-+
D-flag: When the Prefix is leaked from level-2 to level-1, the
D bit MUST be set. Otherwise, this bit MUST be clear.
Prefixes with the D bit set MUST NOT be leaked from level-1 to
level-2. This is to prevent looping.
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S-flag: Set when Sub-TLVs are present for the prefix entry.
o Algorithm (1 octet): Associated Algorithm from 1 to 255.
o Prefix Len (1 octet): Prefix length measured in bits.
o Prefix (variable length): Prefix mapped to Flex-Algorithm.
o Optional Sub-TLV-length (1 octet): Number of octets used by sub-
TLVs
o Optional sub-TLVs (variable length).
A router receiving multiple IPv4 Algorithm Prefix Reachability
advertisements for the same prefix, from the same originator, each
with a different Algorithm, MUST select the first advertisement in
the lowest-numbered LSP and ignore any subsequent IPv4 Algorithm
Prefix Reachability advertisements for the same prefix for any other
Algorithm.
A router receiving multiple IPv4 Algorithm Prefix Reachability
advertisements for the same prefix, from different originators, each
with a different Algorithm, MUST ignore all of them and MUST NOT
install any forwarding entries based on these advertisements.
In cases where a prefix advertisement is received in both a IPv4
Prefix Reachability TLV and an IPv4 Algorithm Prefix Reachability
TLV, the IPv4 Prefix Reachability advertisement MUST be preferred
when installing entries in the forwarding plane.
6.2. The ISIS IPv6 Algorithm Prefix Reachability TLV
The ISIS IPv6 Algorithm Prefix Reachability TLV is identical to the
ISIS IPv4 Algorithm Prefix Reachability TLV, except that it has a
unique type. The type is TBD by IANA.
A router receiving multiple IPv6 Algorithm Prefix Reachability
advertisements for the same prefix, from the same originator, each
with a different Algorithm, MUST select the first advertisement in
the lowest-numbered LSP and ignore any subsequent IPv6 Algorithm
Prefix Reachability advertisements for the same prefix for any other
Algorithm.
A router receiving multiple IPv6 Algorithm Prefix Reachability
advertisements for the same prefix, from different originators, each
with a different Algorithm, MUST ignore all of them and MUST NOT
install any forwarding entries based on these advertisements.
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In cases where a prefix advertisement is received in both a IPv6
Prefix Reachability TLV and an IPv6 Algorithm Prefix Reachability
TLV, the IPv6 Prefix Reachability advertisement MUST be preferred
when installing entries in the forwarding plane.
6.3. The OSPFv2 Algorithm Prefix Reachability TLV
A new top level TLV of OSPFv2 Extended Prefix Opaque LSA is defined
for advertising IPv4 Algorithm Prefix Reachability in OSPFv2 - OSPF
Algorithm Prefix Reachability TLV
Multiple Algorithm Prefix Reachability TLV MAY be advertised in each
OSPFv2 Extended Prefix Opaque LSA. However, since the opaque LSA
type defines the flooding scope, the LSA flooding scope MUST satisfy
the application specific requirements for all the prefixes included
in a single OSPFv2 Extended Prefix Opaque LSA. The Algorithm Prefix
Reachability 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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Route Type | Prefix Length | AF | Flags |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MT-ID | Algorithm | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Address Prefix (variable) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Metric |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sub-TLVs (variable) |
+- -+
| |
OSPFv2 Algorithm Prefix Reachability TLV
Type: Algorithm Prefix Reachability TLV (Value TBD by IANA).
Length: Variable dependent on sub-TLVs.
Route Type (1 octet): type of the OSPF route. Supported types
are:
1 - Intra-Area
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2 - Inter-Area
3 - AS External with Type-1 Metric
4 - AS External with Type-2 Metric
5 - NSSA External with Type-1 Metric
6 - NSSA External with Type-2 Metric
Prefix Length (1 octet): Length of prefix in bits.
AF (1 octet): Address family for the prefix. Currently, the only
supported value is 0 for IPv4 unicast. The inclusion of address
family in this TLV allows for future extension.
Flags (1 octet): Flags applicable to the prefix. Supported Flags
include:
0x80 - A-Flag (Attach flag): An Area Border Router (ABR)
generating an Extended Prefix TLV for inter-area prefix that is
locally connected or attached in other connected area SHOULD
set this flag.
0x40 - N-Flag (Node Flag): Set when the prefix identifies the
advertising router i.e., the prefix is a host prefix
advertising a globally reachable address typically associated
with a loopback address. The advertising router MAY choose to
not set this flag even when the above conditions are met. If
the flag is set and the prefix length is not a host prefix then
the flag MUST be ignored. The flag is preserved when the
OSPFv2 Extended Prefix Opaque LSA is propagated between areas.
MT-ID (1 octet): Multi-Topology ID as defined in [RFC8402]
Algorithm: (1 octet). Associated Algorithm from 1 to 255.
Adress Prefix: For the address family IPv4 unicast, the prefix
itself encoded as a 32-bit value. The default route is
represented by a prefix of length 0. Prefix encoding for other
address families is beyond the scope of this specification.
Metric (4 octets): Metric information.
If this TLV is advertised multiple times for the same prefix in the
same OSPFv2 Extended Prefix Opaque LSA, only the first instance of
the TLV is used by receiving OSPFv2 Routers. This situation SHOULD
be logged as an error.
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If this TLV is advertised multiple times for the same prefix in
different OSPFv2 Extended Prefix Opaque LSAs originated by the same
OSPF router, the OSPF advertising router is re-originating Extended
Prefix Opaque LSAs for multiple prefixes and is most likely repacking
Algorithm Prefix Reachability TLVs in Extended Prefix Opaque LSAs.
In this case, the Algorithm Prefix Reachability TLV in the Extended
Prefix Opaque LSA with the smallest Opaque ID is used by receiving
OSPFv2 Routers. This situation may be logged as a warning.
It is RECOMMENDED that OSPF routers advertising Algorithm Prefix
Reachability TLVs in different Extended Prefix Opaque LSAs re-
originate these LSAs in ascending order of Opaque ID to minimize the
disruption.
A router receiving multiple Algorithm Prefix Reachability TLVs for
the same prefix, from different originators, each with a different
Algorithm, MUST ignore all of them and MUST NOT install any
forwarding entries based on these advertisements.
In cases where a prefix advertisement is received in any of the LSAs
advertising the prefix reachability for algorithm 0 (Router-LSA,
Summary-LSA, AS-external-LSA or NSSA AS-external LSA) and in an IPv4
Algorithm Prefix Reachability TLV, the prefix reachability
advertisement for algorithm 0 MUST be preferred when installing
entries in the forwarding plane, regardless of the Route Type
advertised in IPv4 Algorithm Prefix Reachability TLV.
6.4. The OSPFv3 Flex-Algorithm IP Prefix Opaque LSA
TBD.
7. Calculating of IP Flex-Algorthm Paths
IP Flex-Algorthm is considered as yet another application of the
Flex-Algorithm as described in Section 10 and Section 12 of the
[I-D.ietf-lsr-flex-algo].
Participation for the IP Flex-Algorithm is signalled as described in
Section 5 and is specific to the IP Flex-Algorithm application.
Calculation of IP Flex-Algorithm paths follows the Section 12 of
[I-D.ietf-lsr-flex-algo]. This computation uses the IP Flex-
Algorithm participation and is independent of the Flex-Algorithm
calculation done for any other Flex-Algorithm applications (e.g. SR,
SRv6).
IP Flex-Algorithm application only considers participating nodes
during the Flex-Algorithm calculation. When computing paths for a
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given Flex-Algorithm, all nodes that do not advertise participation
for IP Flex-Algorithm, as described in Section 5, MUST be pruned from
the topology.
8. IP Flex-Algorthm Forwarding
IP Algorithm Prefix Reachability advertisement as described in
Section 5 includes the MTID value that associates the prefix with a
specific topology. Algorithm Prefix Reachability advertisement also
includes an Algorithm value that explicitly associates the prefix
with a specific Flex-Algorithm. The paths to the prefix MUST be
calculated using the specified Flex-Algorithm in the associated
topology.
Forwarding entries for the IP Flex-Algorithm prefixes advertised in
IGPs MUST be installed in the forwarding plane of the receiving IP
Flex-Algorithm prefix capable routers when they participate in the
associated topology and algorithm. Forwarding entries for IP Flex-
Algorithm prefixes associated with Flex-Algorithms in which the node
is not participating MUST NOT be installed in the forwarding plane.
When the IP Flex-Algorithm prefix is associated with a Flex-
Algorithm, LFA paths to the prefix MUST be calculated using such
Flex-Algorithm in the associated topology, to guarantee that they
follow the same constraints as the calculation of the primary paths.
9. Deployment Considerations
IGP Flex-Algorithm can be used by many applications. Original
specification was done for SR and SRv6, this specification adds IP as
another application that can use IGP Flex-Algorithm. Other
applications may be defined in the future. This section provides
some details about the coexistence of the various applications of the
IGP Flex-Algorithm.
Flex-Algorithm definition (FAD), as described in
[I-D.ietf-lsr-flex-algo], is application independent and is used by
all Flex-Algorithm applications.
Participation in the Flex-Algorithm, as described in
[I-D.ietf-lsr-flex-algo], is application specific.
Calculation of the flex-algo paths is application specific and uses
application specific participation advertisements.
Application specific participation and calculation guarantee that the
forwarding of the traffic over the Flex-Algorithm application
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specific paths is consistent between all nodes over which the traffic
is being forwarded.
Multiple application can use the same Flex-Algorithm value at the
same time and and as such share the FAD for it. For example SR-MPLS
and IP can both use such common Flex-Algorithm. Traffic for SR-MPLS
will be forwarded based on Flex-algorithm specific SR SIDs. Traffic
for IP Flex-Algorithm will be forwarded based on Flex-Algorithm
specific prefix reachability announcements.
10. IANA Considerations
This specification updates the OSPF Router Information (RI) TLVs
Registry as follows:
+-------+------------------+---------------------------+
| Value | TLV Name | Reference |
+-------+------------------+---------------------------+
| TBD | IP Algorithm TLV | This Document Section 5.2 |
+-------+------------------+---------------------------+
This document also updates the "Sub-TLVs for TLV 242" registry as
follows:
+-------+----------------------+---------------------------+
| Value | TLV Name | Reference |
+-------+----------------------+---------------------------+
| TBD | IP Algorithm Sub-TLV | This Document Section 5.1 |
+-------+----------------------+---------------------------+
This document also updates the "ISIS TLV Codepoints Registry"
registry as follows:
+-------+----------------------------------+------------------------+
| Value | TLV Name | Reference |
+-------+----------------------------------+------------------------+
| TBD | IPv4 Algorithm Prefix | This document, |
| | Reachability TLV | Section 6.1 |
| TBD | IPv6 Algorithm Prefix | This document, |
| | Reachability TLV | Section 6.2 |
| TBD |
+-------+----------------------------------+------------------------+
This document updates the "OSPFv2 Extended Prefix Opaque LSA TLVs"
registry as follows::
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+-------+----------------------------------+------------------------+
| Value | TLV Name | Reference |
+-------+----------------------------------+------------------------+
| TBD | OSPFv2 Algorithm Prefix | This Document, |
| | Reachability TLV | Section 6.1 |
+-------+----------------------------------+------------------------+
11. Security Considerations
TBD
12. Acknowledgements
TBD.
13. References
13.1. Normative References
[I-D.ietf-lsr-flex-algo]
Psenak, P., Hegde, S., Filsfils, C., Talaulikar, K., and
A. Gulko, "IGP Flexible Algorithm", draft-ietf-lsr-flex-
algo-13 (work in progress), October 2020.
[ISO10589]
IANA, "Intermediate system to Intermediate system routing
information exchange protocol for use in conjunction with
the Protocol for providing the Connectionless-mode Network
Service (ISO 8473)", August 1987, <ISO/IEC 10589:2002>.
[RFC0791] Postel, J., "Internet Protocol", STD 5, RFC 791,
DOI 10.17487/RFC0791, September 1981,
<https://www.rfc-editor.org/info/rfc791>.
[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>.
[RFC2328] Moy, J., "OSPF Version 2", STD 54, RFC 2328,
DOI 10.17487/RFC2328, April 1998,
<https://www.rfc-editor.org/info/rfc2328>.
[RFC3630] Katz, D., Kompella, K., and D. Yeung, "Traffic Engineering
(TE) Extensions to OSPF Version 2", RFC 3630,
DOI 10.17487/RFC3630, September 2003,
<https://www.rfc-editor.org/info/rfc3630>.
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[RFC4915] Psenak, P., Mirtorabi, S., Roy, A., Nguyen, L., and P.
Pillay-Esnault, "Multi-Topology (MT) Routing in OSPF",
RFC 4915, DOI 10.17487/RFC4915, June 2007,
<https://www.rfc-editor.org/info/rfc4915>.
[RFC5120] Przygienda, T., Shen, N., and N. Sheth, "M-ISIS: Multi
Topology (MT) Routing in Intermediate System to
Intermediate Systems (IS-ISs)", RFC 5120,
DOI 10.17487/RFC5120, February 2008,
<https://www.rfc-editor.org/info/rfc5120>.
[RFC5305] Li, T. and H. Smit, "IS-IS Extensions for Traffic
Engineering", RFC 5305, DOI 10.17487/RFC5305, October
2008, <https://www.rfc-editor.org/info/rfc5305>.
[RFC5340] Coltun, R., Ferguson, D., Moy, J., and A. Lindem, "OSPF
for IPv6", RFC 5340, DOI 10.17487/RFC5340, July 2008,
<https://www.rfc-editor.org/info/rfc5340>.
[RFC7684] Psenak, P., Gredler, H., Shakir, R., Henderickx, W.,
Tantsura, J., and A. Lindem, "OSPFv2 Prefix/Link Attribute
Advertisement", RFC 7684, DOI 10.17487/RFC7684, November
2015, <https://www.rfc-editor.org/info/rfc7684>.
[RFC7770] Lindem, A., Ed., Shen, N., Vasseur, JP., Aggarwal, R., and
S. Shaffer, "Extensions to OSPF for Advertising Optional
Router Capabilities", RFC 7770, DOI 10.17487/RFC7770,
February 2016, <https://www.rfc-editor.org/info/rfc7770>.
[RFC7981] Ginsberg, L., Previdi, S., and M. Chen, "IS-IS Extensions
for Advertising Router Information", RFC 7981,
DOI 10.17487/RFC7981, October 2016,
<https://www.rfc-editor.org/info/rfc7981>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC8200] Deering, S. and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", STD 86, RFC 8200,
DOI 10.17487/RFC8200, July 2017,
<https://www.rfc-editor.org/info/rfc8200>.
13.2. Informative References
Britto, et al. Expires May 19, 2021 [Page 15]
Internet-Draft IP Flex-Algorithm November 2020
[I-D.ietf-spring-srv6-network-programming]
Filsfils, C., Camarillo, P., Leddy, J., Voyer, D.,
Matsushima, S., and Z. Li, "SRv6 Network Programming",
draft-ietf-spring-srv6-network-programming-24 (work in
progress), October 2020.
[IANA-ALG]
IANA, "Sub-TLVs for TLV 242 (IS-IS Router CAPABILITY
TLV)", August 1987, <https://www.iana.org/assignments/igp-
parameters/igp-parameters.xhtml#igp-algorithm-types>.
[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>.
Authors' Addresses
William Britto
Juniper Networks
Elnath-Exora Business Park Survey
Bangalore, Karnataka 560103
India
Email: bwilliam@juniper.net
Shraddha Hegde
Juniper Networks
Elnath-Exora Business Park Survey
Bangalore, Karnataka 560103
India
Email: shraddha@juniper.net
Parag Kaneriya
Juniper Networks
Elnath-Exora Business Park Survey
Bangalore, Karnataka 560103
India
Email: pkaneria@juniper.net
Britto, et al. Expires May 19, 2021 [Page 16]
Internet-Draft IP Flex-Algorithm November 2020
Rejesh Shetty
Juniper Networks
Elnath-Exora Business Park Survey
Bangalore, Karnataka 560103
India
Email: mrajesh@juniper.net
Ron Bonica
Juniper Networks
2251 Corporate Park Drive
Herndon, Virginia 20171
USA
Email: rbonica@juniper.net
Peter Psenak
Cisco Systems
Apollo Business Center
Mlynske nivy 43, Bratislava 82109
Slovakia
Email: ppsenak@cisco.com
Britto, et al. Expires May 19, 2021 [Page 17]
