wdiff draft-ietf-ospf-te-link-attr-reuse-10.txt draft-ietf-ospf-te-link-attr-reuse-11.txt

LSR Working Group P. Psenak, Ed.
Internet-Draft L. Ginsberg
Intended status: Standards Track Cisco Systems
Expires: May 2, November 8, 2020 W. Henderickx
Nokia
J. Tantsura
Apstra
J. Drake
Juniper Networks
October 30, 2019
May 7, 2020

OSPF Link Traffic Engineering Attribute Reuse
draft-ietf-ospf-te-link-attr-reuse-10.txt
draft-ietf-ospf-te-link-attr-reuse-11.txt

Abstract

Various

Existing traffic engineering related link attributes attribute advertisements
have been defined in OSPF in the context of
the MPLS Traffic Engineering (TE) and GMPLS. are used in RSVP-TE deployments. Since the
original RSVP-TE use case was defined, additional applications (e.g., SRTE,
LFA)
Segment Routing Traffic Engineering, Loop Free Alternate) have been
defined which also make use of the link attribute advertisements. This document defines how In
cases where multiple applications wish to distribute make use of these link
attributes the current advertisements do not support application
specific values for a given attribute nor do they support indication
of which applications are using the advertised value for a given
link. This document introduces new link attribute advertisements in
OSPFv2 and OSPFv3 for applications other than MPLS TE
or GMPLS. which address both of these shortcomings.

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 2, November 8, 2020.

This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.

Table of Contents

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. 3
2. Requirements notation Language . . . . . . . . . . . . . . . . . . 3
2. . . 4
3. Existing Advertisement of Link Attributes . . . . . . . . . . 4
4. Advertisement of Link Attributes . . . . 3
2.1. . . . . . . . . . . 4
4.1. OSPFv2 Extended Link Opaque LSA and OSPFv3 E-Router-LSA . 3
3. 4
5. Advertisement of Application Specific Values . . . . . . . . 4
4. 5
6. Reused TE link attributes . . . . . . . . . . . . . . . . . . 7
4.1. 8
6.1. Shared Risk Link Group (SRLG) . . . . . . . . . . . . . . 7
4.2. 8
6.2. Extended Metrics . . . . . . . . . . . . . . . . . . . . 8
4.3.
6.3. Administrative Group . . . . . . . . . . . . . . . . . . 9
4.4. TE
6.4. Traffic Engineering Metric . . . . . . . . . . . . . . . 10
7. Maximum Link Bandwidth . . . . . . . . . 9
5. Maximum Link Bandwidth . . . . . . . . . . 10
8. Considerations for Extended TE Metrics . . . . . . . . . 9
6. . . 10
9. Local Interface IPv6 Address Sub-TLV . . . . . . . . . . . . 10
7. 11
10. Remote Interface IPv6 Address Sub-TLV . . . . . . . . . . . . 10
8. Deployment Considerations 11
11. Attribute Advertisements and Enablement . . . . . . . . . . . 11
12. Deployment Considerations . . . . . . . 10
8.1. Use of TE LSA Advertisements . . . . . . . . . . . 12
12.1. Use of Legacy RSVP-TE LSA Advertisements . . . 10
8.2. . . . . . 12
12.2. Use of Zero Length Application Identifier Bit Masks . . . 11
9. Attribute Advertisements 13
12.3. Interoperability, Backwards Compatibility and Enablement Migration
Concerns . . . . . . . . . . . 11
10. Backward Compatibility . . . . . . . . . . . . . 13
12.3.1. Multiple Applications: Common Attributes with RSVP-
TE . . . . . . 12
11. . . . . . . . . . . . . . . . . . . . 13
12.3.2. Multiple Applications: Some Attributes Not Shared
with RSVP-TE . . . . . . . . . . . . . . . . . . . . 14
12.3.3. Interoperability with Legacy Routers . . . . . . . . 14
12.3.4. Use of Application Specific Advertisements for RSVP-
TE . . . . . . . . . . . . . . . . . . . . . . . . . 15
13. Security Considerations . . . . . . . . . . . . . . . . . . . 13
12. 15
14. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13
12.1. 15
14.1. OSPFv2 . . . . . . . . . . . . . . . . . . . . . . . . . 13
12.2. 16
14.2. OSPFv3 . . . . . . . . . . . . . . . . . . . . . . . . . 14
13. 16
15. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 15
14. 17
16. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 15
15. 18
17. References . . . . . . . . . . . . . . . . . . . . . . . . . 15
15.1. 18
17.1. Normative References . . . . . . . . . . . . . . . . . . 15
15.2. 18
17.2. Informative References . . . . . . . . . . . . . . . . . 16 19
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 18 20

1. Introduction

Various

Advertisement of link attributes have been defined in by the OSPFv2 [RFC2328] and OSPFv3
[RFC5340] protocols in the context support of the MPLS TE traffic engineering (TE) was
introduced by [RFC3630] and GMPLS. All these
attributes are distributed [RFC5329] respectively. It has been
extended by OSPFv2 as sub-TLVs [RFC4203], [RFC7308] and [RFC7471]. Use of the Link-TLV
advertised these
extensions has been associated with deployments supporting Traffic
Engineering over Multiprotocol Label Switching (MPLS) in the OSPFv2 TE Opaque LSA [RFC3630]. In OSPFv3, they
are distributed as sub-TLVs presence
of the Link-TLV advertised in the OSPFv3
Intra-Area-TE-LSA Resource Reservation Protocol (RSVP) - more succinctly
referred to as defined in [RFC5329].

Many of these link attributes are useful outside RSVP-TE [RFC3209].

For the purposes of traditional MPLS
Traffic Engineering or GMPLS. This brings its own set this document an application is a technology
which makes use of problems,
in particular how to distribute these link attributes in OSPFv2 and
OSPFv3 when MPLS TE and GMPLS are not deployed or attribute advertisements - examples of which
are deployed listed in
parallel with other Section 5.

In recent years new applications that use these link attributes.

[RFC7855] discusses use cases/requirements for Segment Routing (SR).
Included among these have been introduced which have use
cases is for many of the link attributes historically used by RSVP-TE.
Such applications include Segment Routing Traffic Engineering
(SRTE). If both RSVP-TE (SRTE)
[I-D.ietf-spring-segment-routing-policy] and SRTE are deployed Loop Free Alternates
(LFA) [RFC5286]. This has introduced ambiguity in that if a network, link
attribute advertisements can be used by one or both of these
applications. As there is no requirement for the link attributes
advertised on
deployment includes a given link used by mix of RSVP-TE support and SRTE to be identical to the link
attributes advertised on that same link used by RSVP-TE, there support (for
example) it is a
clear requirement not possible to unambiguously indicate independently which link attribute
advertisements are to be used by each application.

As the number of applications RSVP-TE and which may wish advertisements are
to utilize link
attributes may grow in be used by SRTE. If the future, topologies are fully congruent this may
not be an issue, but any incongruence leads to ambiguity.

An additional requirement is that
the extensions defined allow the association of additional issue arises in cases where both applications to are
supported on a link attributes without altering the format of but the link attribute values associated with
each application differ. Current advertisements or introducing new backwards compatibility do not support
advertising application specific values for the same attribute on a
specific link.

This document defines extensions which address these issues.

Finally, there may still be many Also,
as evolution of use cases where a single attribute value for link attributes can be shared among multiple applications, so expected to
continue in the years to come, this document defines a solution should
minimize advertising duplicate link/attribute when possible.

1.1. which
is easily extensible for the introduction of new applications and new
use cases.

2. Requirements notation 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 [RFC2119].

2. BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.

3. Existing Advertisement of Link Attributes

This section outlines the solution for advertising link attributes
originally defined for MPLS TE or GMPLS when they

There are existing advertisements used for other
applications.

2.1. in support of RSVP-TE. These
advertisements are carried in the OSPFv2 Extended Link TE Opaque LSA [RFC3630] and
OSPFv3 E-Router-LSA Intra-Area-TE-LSA [RFC5329]. Additional RSVP-TE link
attributes have been defined by [RFC4203], [RFC7308] and [RFC7471].

Extended Link Opaque LSAs as defined in [RFC7684] for OSPFv2 and
Extended Router-LSAs [RFC8362] for OSPFv3 are used to advertise link
attributes that are used by applications other then MPLS TE RSVP-TE or GMPLS.
These LSAs were defined as a generic containers for distribution of
the extended link attributes. There

4. Advertisement of Link Attributes

This section outlines the solution for advertising link attributes
originally defined for RSVP-TE or GMPLS when they are several advantages used for other
applications.

4.1. OSPFv2 Extended Link Opaque LSA and OSPFv3 E-Router-LSA

Advantages of Extended Link Opaque LSAs as defined in using
them: [RFC7684] for
OSPFv2 and Extended Router-LSAs [RFC8362] for OSPFv3 when used for
advertisement of link attributes originally defined for RSVP-TE or
GMPLS:

1. Advertisement of the link attributes does not make the link part
of the TE RSVP-TE topology. It avoids any conflicts and is fully
compatible with [RFC3630] and [RFC5329].

2. The OSPFv2 TE Opaque LSA and OSPFv3 Intra-Area-TE-LSA remains
truly opaque to OSPFv2 and OSPFv3 as originally defined in
[RFC3630] and [RFC5329] respectively. Their contents are not
inspected by OSPF, that acts as a pure transport.

3. There is clear distinction between link attributes used by RSVP-
TE and link attributes used by other OSPFv2 or OSPFv3
applications.

4. All link attributes that are used by other applications are
advertised in a single LSA, the Extended Link Opaque LSA in
OSPFv2 or the OSPFv3 E-Router-LSA [RFC8362] in OSPFv3.

The disadvantage of this approach is that in rare cases, the same
link attribute is advertised in both the TE Opaque and Extended Link
Attribute LSAs in OSPFv2 or the Intra-Area-TE-LSA and E-Router-LSA in
OSPFv3. Additionally, there will be additional standardization
effort. However, this could also be viewed as an advantage as the
non-TE use cases for the TE link attributes are documented and
validated by the LSR working group.

Extended Link Opaque LSA [RFC7684] and E-Router-LSA [RFC8362] are
used to advertise any link attributes used for non-TE non-RSVP-TE
applications in OSPFv2 or OSPFv3 respectively, including those that
have been originally defined for TE applications. RSVP-TE applications (See
Section 6).

TE link attributes used for RSVP-TE/GMPLS continue to use OSPFv2 TE
Opaque LSA [RFC3630] and OSPFv3 Intra-Area-TE-LSA [RFC5329].

The format of the link attribute TLVs that have been defined for TE
RSVP-TE applications will be kept unchanged even when they are used
for non-
TE non-RSVP-TE applications. Unique code points will be are allocated for
these TE link attribute TLVs from the OSPFv2 Extended Link TLV Sub-TLV
Registry [RFC7684] and from the OSPFv3 Extended LSA Sub-TLV Registry
[RFC8362]. For each reused TLV, the code point will be defined
[RFC8362], as specified in an
IETF document along with the expected use-case(s).

3. Section 14.

5. Advertisement of Application Specific Values

To allow advertisement of the application specific values of the link
attribute, a new Application Specific Link Attributes (ASLA) sub-TLV
is defined. The ASLA sub-TLV is a sub-TLV of the OSPFv2 Extended
Link TLV [RFC7471] [RFC7684] and OSPFv3 Router-Link TLV [RFC8362].

The ASLA sub-TLV is an optional sub-TLV and can appear multiple times
in the OSPFv2 Extended Link TLV and OSPFv3 Router-Link TLV. The ASLA
sub-TLV MUST be used for advertisement of the link attributes listed
at the end on this section if these are advertised inside OSPFv2
Extended Link TLV and OSPFv3 Router-Link TLV. It 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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SABM Length | UDABM Length | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Standard Application Identifier Bit-Mask |
+- -+
| ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| User Defined Application Identifier Bit-Mask |
+- -+
| ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Link Attribute sub-sub-TLVs |
+- -+
| ... |

where:

Type: 10 (OSPFv2), 11 (OSPFv3)

Length: variable

SABM Length: Standard Application Identifier Bit-Mask Length. It
MUST be a multiple of Length in
octets. The legal values are 0, 4 bytes. or 8. If the Standard
Application Bit-
Mask Bit-Mask is not present, the Standard Application Bit-Mask Bit-
Mask Length MUST be set to 0.

UDABM Length: User Defined Application Identifier Bit-Mask Length.
It MUST be a multiple of Length
in octets. The legal values are 0, 4 bytes. or 8. If the User Defined
Application Bit-Mask is not present, the User Defined Application
Bit-Mask Length MUST be set to 0.

Standard Application Identifier Bit-Mask: Optional set of bits,
where each bit represents a single standard application. Bits are
defined in [I-D.ietf-isis-te-app], which also request a new IANA
"Link Attribute Applications" registry under "Interior Gateway
Protocol (IGP) Parameters" for them. [I-D.ietf-isis-te-app]. The bits are repeated here for
informational purpose:

Bit-0 (R-bit): RSVP TE RSVP-TE

Bit-1 (S-bit): Segment Routing TE

Bit-2 (F-bit): Loop Free Alternate (LFA). Includes all LFA
types

User Defined Application Identifier Bit-Mask: Optional set of
bits, where each bit represents a single user defined application.

If the SABM or UDABM length is other than 0, 4, or 8, the ASLA sub-
TLV MUST be ignored by the receiver.

Standard Application Identifier Bits are defined/sent starting with
Bit 0. Additional bit definitions Undefined bits MUST be transmitted as 0 and MUST be ignored
on receipt. Bits that are defined in the future
SHOULD NOT transmitted MUST be assigned in ascending bit order so treated as if they
are set to minimize the
number of octets 0 on receipt. Bits that will need to are not supported by an
implementation MUST be transmitted. ignored on receipt.

User Defined Application Identifier Bits have no relationship to
Standard Application bits Identifier Bits and are NOT managed by IANA or
any other standards body. It is recommended that bits are used
starting with Bit 0 so as to minimize the number of octets required
to advertise all of them.

Undefined bits in both Bit-Masks MUST be transmitted as 0 and MUST be
ignored on receipt. Bits that are NOT transmitted MUST be treated as
if they are set to 0 on receipt. UDAs.

If the link attribute advertisement is limited to be used by a
specific set of applications, corresponding Bit-Masks MUST be present
and application specific bit(s) MUST be set for all applications that
use the link attributes advertised in the ASLA sub-TLV.

Application Bit-Masks apply to all link attributes that support
application specific values and are advertised in the ASLA sub-TLV.

The advantage of not making the Application Bit-Masks part of the
attribute advertisement itself is that we can keep the format of the any previously
defined link attributes that have been defined previously can be kept and reuse the same
format reused when advertising them
in the ASLA sub-TLV.

When neither the Standard Application Bits nor the User Defined
Application bits are set (i.e., both SABM Length and UDABM Length are
0) in the ASLA sub-TLV, then the link attributes included in it MUST
be considered as being applicable to all applications.

If, however, another advertisement of

If the same link attribute
includes any Application Bit-Mask in the ASLA sub-TLV, applications
that are listed is advertised in the Application Bit-Masks of such more than single ASLA sub-TLV
SHOULD use the attribute advertisement which has the application
specific bit set in the Application Bit-Masks.

If sub-TLVs
with the same application is listed in the Application Bit-Masks of
more then one ASLA sub-TLV, Bit-Masks, the
application SHOULD use the first instance of advertisement and ignore
any subsequent advertisements of the same that attribute.

This situation SHOULD be logged as an error.

This document defines the initial set of link attributes that MUST
use the ASLA sub-TLV if advertised in the OSPFv2 Extended Link TLV or
in the OSPFv3 Router-Link TLV. If the ASLA sub-TLV includes any link
attribute(s) NOT listed below, they MUST be ignored. Documents which define new link
attributes MUST state whether the new attributes support application
specific values and as such MUST be advertised in an ASLA sub-TLV.
The link attributes that MUST be advertised in ASLA sub-TLVs are:

- Shared Risk Link Group [RFC4203]

- Unidirectional Link Delay Dela [RFC7471]

- Min/Max Unidirectional Link Delay [RFC7471]
- Unidirectional Delay Variation [RFC7471]

- Unidirectional Link Loss [RFC7471]

- Unidirectional Residual Bandwidth [RFC7471]

- Unidirectional Available Bandwidth [RFC7471]

- Unidirectional Utilized Bandwidth [RFC7471]

- Administrative Group [RFC3630]

- Extended Administrative Group [RFC7308]

- TE Metric

4. [RFC3630]

6. Reused TE link attributes

This section defines the use case and indicates the code points
(Section 14) from the OSPFv2 Extended Link TLV Sub-TLV Registry and
OSPFv3 Extended LSA Sub-TLV Registry for some of the link attributes
that have been originally defined for TE RSVP-TE or GMPLS.

4.1.

6.1. Shared Risk Link Group (SRLG)

The SRLG of a link can be used in OSPF calculated IPFRR [RFC5714] to
compute a backup path that does not share any SRLG group with the
protected link.

To advertise the SRLG of the link in the OSPFv2 Extended Link TLV,
the same format for the sub-TLV defined in section 1.3 of [RFC4203]
is used and TLV type 11 is used. Similarly, for OSPFv3 to advertise
the SRLG in the OSPFv3 Router-Link TLV, TLV type 12 is used.

4.2.

6.2. Extended Metrics

[RFC3630] defines several link bandwidth types. [RFC7471] defines
extended link metrics that are based on link bandwidth, delay and
loss characteristics. All these can be used to compute primary and
backup paths within an OSPF area to satisfy requirements for
bandwidth, delay (nominal or worst case) or loss.

To advertise extended link metrics in the OSPFv2 Extended Link TLV,
the same format for the sub-TLVs defined in [RFC7471] is used with
the following TLV types:

12 - Unidirectional Link Delay
13 - Min/Max Unidirectional Link Delay

14 - Unidirectional Delay Variation

15 - Unidirectional Link Loss

16 - Unidirectional Residual Bandwidth

17 - Unidirectional Available Bandwidth

18 - Unidirectional Utilized Bandwidth

To advertise extended link metrics in the OSPFv3 Extended LSA Router-
Link TLV, the same format for the sub-TLVs defined in [RFC7471] is
used with the following TLV types:

13 - Unidirectional Link Delay

14 - Min/Max Unidirectional Link Delay

15 - Unidirectional Delay Variation

16 - Unidirectional Link Loss

17 - Unidirectional Residual Bandwidth

18 - Unidirectional Available Bandwidth

19 - Unidirectional Utilized Bandwidth

4.3.

6.3. Administrative Group

[RFC3630] and [RFC7308] define the Administrative Group and Extended
Administrative Group sub-TLVs respectively.

To advertise the Administrative Group and Extended Administrative
Group in the OSPFv2 Extended Link TLV, the same format for the sub-
TLVs defined in [RFC3630] and [RFC7308] is used with the following
TLV types:

19 - Administrative Group

20 - Extended Administrative Group

To advertise Administrative Group and Extended Administrative Group
in the OSPFv3 Router-Link TLV, the same format for the sub-TLVs
defined in [RFC3630] and [RFC7308] is used with the following TLV
types:

20 - Administrative Group

21 - Extended Administrative Group

4.4. TE

6.4. Traffic Engineering Metric

[RFC3630] defines TE Traffic Engineering Metric.

To advertise the TE Traffic Engineering Metric in the OSPFv2 Extended
Link TLV, the same format for the sub-TLV defined in section 2.5.5 of
[RFC3630] is used and TLV type 22 is used. Similarly, for OSPFv3 to
advertise the TE Traffic Engineering Metric in the OSPFv3 Router-Link
TLV, TLV type 22 is used.

7. Maximum Link Bandwidth

Maximum link bandwidth is an application independent attribute of the
link that is defined in [RFC3630]. Because it is an application
independent attribute, it MUST NOT be advertised in ASLA sub-TLV.
Instead, it MAY be advertised as a sub-TLV of the Extended Link
Opaque LSA Extended Link TLV in OSPFv2 [RFC7684] or sub-TLV of OSPFv3
E-Router-LSA Router-Link TLV in OSPFv3 [RFC8362].

To advertise the Maximum link bandwidth in the OSPFv2 Extended Link
TLV, the same format for sub-TLV defined in [RFC3630] is used with
TLV type 23.

To advertise the Maximum link bandwidth in the OSPFv3 Router-Link
TLV, the same format for sub-TLV defined in [RFC3630] is used with
TLV type 23.

8. Considerations for Extended TE Metrics

[RFC7471] defines a number of dynamic performance metrics associated
with a link. It is conceivable that such metrics could be measured
specific to traffic associated with a specific application.
Therefore this document includes support for advertising these link
attributes specific to a given application. However, in practice it
may well be more practical to have these metrics reflect the
performance of all traffic on the link regardless of application. In
such cases, advertisements for these attributes can be associated
with all of the applications utilizing that link, for example, by
listing all applications in the Application Bit-Mask.

9. Local Interface IPv6 Address Sub-TLV

The Local Interface IPv6 Address Sub-TLV is an application
independent attribute of the link that is defined in [RFC5329].
Because it is an application independent attribute, it MUST NOT be
advertised in the ASLA sub-TLV. Instead, it MAY be advertised as a
sub-TLV of the OSPFv3 E-Router-LSA Router-Link TLV [RFC8362].

To advertise the Local Interface IPv6 Address Sub-TLV in the OSPFv3
Router-Link TLV, the same format for sub-TLV defined in [RFC5329] is
used with TLV type 24.

10. Remote Interface IPv6 Address Sub-TLV

The Remote Interface IPv6 Address Sub-TLV is an application
independent attribute of the link that is defined in [RFC5329].
Because it is an application independent attribute, it MUST NOT be
advertised in the ASLA sub-TLV. Instead, it MAY be advertised as a
sub-TLV of the OSPFv3 E-Router-LSA Router-Link TLV [RFC8362].

To advertise the Remote Interface IPv6 Address Sub-TLV in the OSPFv3
Router-Link TLV, the same format for sub-TLV defined in [RFC5329] is
used with TLV type 25.

11. Attribute Advertisements and Enablement

This document defines extensions to support the advertisement of
application specific link attributes.

Whether the presence of link attribute advertisements for a given
application indicates that the application is enabled on that link
depends upon the application. Similarly, whether the absence of link
attribute advertisements indicates that the application is not
enabled depends upon the application.

In the case of RSVP-TE, the advertisement of application specific
link attributes has no implication of RSVP-TE being enabled on that
link. The RSVP-TE enablement is solely derived from the information
carried in the OSPFv2 TE Opaque LSA [RFC3630] and OSPFv3 Intra-Area-
TE-LSA [RFC5329].

In the case of SRTE, advertisement of application specific link
attributes does NOT indicate enablement of SRTE. The advertisements
are only used to support constraints which may be applied when
specifying an explicit path. SRTE is implicitly enabled on all links
which are part of the Segment Routing enabled topology independent of
the existence of link attribute advertisements
In the case of LFA, advertisement of application specific link
attributes does NOT indicate enablement of LFA on that link.
Enablement is controlled by local configuration.

If, in the future, additional standard applications are defined to
use this mechanism, the specification defining this use MUST define
the relationship between application specific link attribute
advertisements and enablement for that application.

This document allows the advertisement of application specific link
attributes with no application identifiers i.e., both the Standard
Application Identifier Bit Mask and the User Defined Application
Identifier Bit Mask are not present (See Section 5). This supports
the use of the link attribute by any application. In the presence of
an application where the advertisement of link attribute
advertisements is used to infer the enablement of an application on
that link (e.g., RSVP-TE), the absence of the application identifier
leaves ambiguous whether that application is enabled on such a link.
This needs to be considered when making use of the "any application"
encoding.

12. Deployment Considerations

8.1.

12.1. Use of TE Legacy RSVP-TE LSA Advertisements

Bit Identifers Identifiers for Standard Applications are defined in Section 3. 5.
All of the identifiers defined in this document are associated with
applications which were already deployed in some networks prior to
the writing of this document. Therefore, such applications have been
deployed using the TE RSVP-TE LSA advertisements. The Standard
Applications defined in this document MAY continue to use TE RSVP-TE LSA
advertisements for a given link so long as at least one of the
following conditions is true:

The application is RSVP-TE

The application is SRTE or LFA and RSVP-TE is not deployed
anywhere in the network

The application is SRTE or LFA, RSVP-TE is deployed in the
network, and both the set of links on which SRTE and/or LFA
advertisements are required and the attribute values used by SRTE
and/or LFA on all such links is fully congruent with the links and
attribute values used by RSVP-TE

Under the conditions defined above, implementations which support the
extensions defined in this document have the choice of using TE RSVP-TE
LSA advertisements or application specific advertisements in support
of SRTE and/or LFA. This will require implementations to provide
controls specifying which type of advertisements are to be sent/
processed on receive for these applications. Further discussion of
the associated issues can be found in Section 10. 12.3.

New applications which future documents define to make use of the
advertisements defined in this document MUST NOT make use of TE RSVP-TE
LSA advertisements.

8.2. This simplifies deployment of new applications
by eliminating the need to support multiple ways to advertise
attributes for the new applications.

12.2. Use of Zero Length Application Identifier Bit Masks

If link attributes are advertised associated with zero length
Application Identifier Bit-Masks Bit Masks for both standard applications and
user defined applications, then any Standard Application and/or any
User Defined Application is permitted to use that set of link
attributes MAY be
used by any application. so long as there is not another set of attributes
advertised on that same link which is associated with a non-zero
length Application Identifier Bit Mask with a matching Application
Identifier Bit set. If support for a new application is introduced
on any node in a network in the presence of such advertisements,
these advertisements MAY are permitted to be used by the new application.
If this is not what is intended, then existing advertisements MUST be
readvertised with an explicit set of applications specified before a
new application is introduced.

9. Attribute Advertisements

12.3. Interoperability, Backwards Compatibility and Enablement

This document defines extensions to support the advertisement Migration Concerns

Existing deployments of
application specific link attributes.

Whether RSVP-TE, SRTE, and/or LFA utilize the presence of link attribute legacy
advertisements for a given
application indicates that listed in Section 3. Routers which do not support the application
extensions defined in this document will only process legacy
advertisements and are likely to infer that RSVP-TE is enabled on that link
depends upon the application. Similarly, whether the absence of link
attribute
links for which legacy advertisements indicates that the application exist. It is not
enabled depends upon the application.

In expected that
deployments using the case legacy advertisements will persist for a
significant period of RSVP-TE, time. Therefore deployments using the advertisement of application specific
link attributes implies that RSVP is enabled on that link. The
absence of RSVP-TE application specific link attributes
extensions defined in
combination this document must be able to co-exist with the absence use
of the legacy advertisements implies that
RSVP is NOT enabled on that link.

In by routers which do not support the case
extensions defined in this document. The following sub-sections
discuss interoperability and backwards compatibility concerns for a
number of SRTE, advertisement deployment scenarios.

12.3.1. Multiple Applications: Common Attributes with RSVP-TE

In cases where multiple applications are utilizing a given link, one
of application specific the applications is RSVP-TE, and all link attributes does NOT indicate enablement of SRTE. The advertisements for a given
link are only used common to support constraints which may be applied when
specifying an explicit path. SRTE is implicitly enabled on all links
which are part of the Segment Routing enabled topology independent of
the existence of link attribute advertisements.

In the case of LFA, advertisement of application specific link
attributes does NOT indicate enablement set of LFA on applications utilizing that link.
Enablement link,
interoperability is controlled achieved by local configuration.

If, in the future, additional standard using legacy advertisements for RSVP-
TE. Attributes for applications are defined to
use this mechanism, the specification defining this use other than RSVP-TE MUST define
the relationship between be
advertised using application specific advertisements. This results
in duplicate advertisements for those attributes.

12.3.2. Multiple Applications: Some Attributes Not Shared with RSVP-TE

In cases where one or more applications other than RSVP-TE are
utilizing a given link and one or more link attribute values are NOT
shared with RSVP-TE, interoperability is achieved by using legacy
advertisements and enablement for that application.

This document allows the advertisement of RSVP-TE. Attributes for applications other than
RSVP-TE MUST be advertised using application specific advertisements.
In cases where some link attributes are shared with no application identifiers i.e., both the Standard
Application Identifier Bit-Mask and RSVP-TE, this
requires duplicate advertisements for those attributes

12.3.3. Interoperability with Legacy Routers

For the User Defined Application Bit
Mask are applications defined in this document, routers which do not present (See Section 3). This supports the use of
support the extensions defined in this document will send and receive
only legacy link attribute by advertisements. So long as there is any application. In
legacy router in the presence network which has any of an application
where the advertisement of applications
enabled, all routers MUST continue to advertise link attributes using
legacy advertisements. In addition, the link attribute values
associated with the set of applications supported by legacy routers
(RSVP-TE, SRTE, and/or LFA) are always shared since legacy routers
have no way of advertising or processing application specific values.
Once all legacy routers have been upgraded, migration from legacy
advertisements is used to
infer application specific advertisements can be achieved
via the enablement of an following steps:

1)Send application on that link (e.g., RSVP-TE), specific advertisements while continuing to
advertise using legacy (all advertisements are then duplicated).
Receiving routers continue to use legacy advertisements.

2)Enable the absence use of the Application Identifier leaves ambiguous whether
that application specific advertisements on all
routers

3)Keep legacy advertisements if needed for RSVP-TE purposes.

When the migration is enabled complete, it then becomes possible to advertise
incongruent values per application on such a given link. This needs to be
considered when making

Documents defining new applications which make use of the "any application" encoding.

10. Backward Compatibility

Link attributes may be concurrently advertised in both the TE Opaque
LSA and the Extended Link Opaque LSA application
specific advertisements defined in OSPFv2 and the OSPFv3 Intra-
Area-TE-LSA this document MUST discuss
interoperability and OSPFv3 Extended LSA Router-Link TLV in OSPFv3.

In fact, there is at least one OSPF implementation backwards compatibility issues that utilizes the
link attributes advertised could occur
in TE Opaque LSAs [RFC3630] for Non-RSVP
TE applications. For example, this implementation the presence of LFA and remote
LFA utilizes links attributes such as Shared Risk Link Groups (SRLG)
[RFC4203] and Admin Group [[RFC3630] advertised in TE Opaque LSAs.
These applications are described in [RFC5286], [RFC7490], [RFC7916]
and [RFC8102].

When an OSPF routing domain includes routers using link attributes
from the OSPFv2 TE Opaque LSAs or which do not support the OSPFv3 Intra-Area-TE-LSA new application.

12.3.4. Use of Application Specific Advertisements for
Non-RSVP TE applications RSVP-TE

The extensions defined in this document (i.e. SRTE and
LFA), OSPF routers in that domain SHOULD continue support RSVP-TE as one of the
supported applications. It is however RECOMMENDED to advertise such all
link-attributes for RSVP-TE in the existing OSPFv2 TE Opaque LSAs or the LSA
[RFC3630] and OSPFv3 Intra-Area-TE-LSA. In such a
deployment, Intra-Area-TE-LSA [RFC5329] to maintain backward
compatibility. RSVP-TE can eventually utilize the advertised application
specific advertisements for newly defined link attributes, which are
defined as application specific.

Link attributes SHOULD that are NOT allowed to be advertised in the same ASLA
Sub-TLV, such as Maximum Reservable Link Bandwidth and Non-
RSVP application access to link attributes is a matter of local
policy.

When advertising link-attributes for any new applications other then
RSVP-TE, SRTE or LFA, OSPF routers Unreserved
Bandwidth MUST NOT use the OSPFv2 TE Opaque LSA or
OSPFv3 Intra-Area-TE-LSA. Instead, advertisement in the OSPFv2
Extended Link Attributes LSAs or [RFC3630] and OSPFv3 E-Router-LSA
Intra-Area-TE-LSA [RFC5329] and MUST NOT be used.

It is RECOMMENDED to advertise link-attributes for RSVP-TE advertised in the
existing TE LSAs.

11. ASLA Sub-
TLV.

13. Security Considerations

Existing security extensions as described in [RFC2328], [RFC5340] and
[RFC8362] apply to extensions defined in this document. While OSPF
is under a single administrative domain, there can be deployments
where potential attackers have access to one or more networks in the
OSPF routing domain. In these deployments, stronger authentication
mechanisms such as those specified in [RFC5709], [RFC7474], [RFC4552]
or [RFC7166] SHOULD be used.

Implementations MUST must assure that malformed TLV and Sub-TLV defined in
this document are detected and do not provide a vulnerability for
attackers to crash the OSPF router or routing process. Reception of
a malformed TLV or Sub-TLV SHOULD be counted and/or logged for
further analysis. Logging of malformed TLVs and Sub-TLVs SHOULD be
rate-limited to prevent a Denial of Service (DoS) attack (distributed
or otherwise) from overloading the OSPF control plane.

12.

This document defines a new way to advertise link attributes.
Tampering with the information defined in this document may have an
effect on applications using it, including impacting Traffic
Engineering. This is similar in nature to the impacts associated
with (for example) [RFC3630]. As the advertisements defined in this
document limit the scope to specific applications, the impact of
tampering is similarly limited in scope.

14. IANA Considerations

12.1.
14.1. OSPFv2

The OSPFv2 Extended Link TLV Sub-TLVs registry [RFC7684] defines sub-TLVs sub-
TLVs at any level of nesting for OSPFv2 Extended Link TLVs. This
specification updates IANA has
assigned the following Sub-TLV types from the OSPFv2 Extended Link
TLV sub-TLVs registry with
the following TLV types: Sub-TLVs Registry:

10 - Application Specific Link Attributes

11 - Shared Risk Link Group

12 - Unidirectional Link Delay

13 - Min/Max Unidirectional Link Delay

14 - Unidirectional Delay Variation

15 - Unidirectional Link Loss

16 - Unidirectional Residual Bandwidth

17 - Unidirectional Available Bandwidth

18 - Unidirectional Utilized Bandwidth

19 - Administrative Group

20 - Extended Administrative Group

22 - TE Metric

23 - Maximum Link Bandwidth

12.2.

14.2. OSPFv3

The OSPFv3 Extended LSA Sub-TLV Registry [RFC8362] defines sub-TLVs
at any level of nesting for OSPFv3 Extended LSAs. This specification
updates IANA has assigned
the following Sub-TLV types from the OSPFv3 Extended LSA Sub-TLV Registry with the following TLV
types:
Registry:

11 - Application Specific Link Attributes

12 - Shared Risk Link Group

13 - Unidirectional Link Delay

14 - Min/Max Unidirectional Link Delay
15 - Unidirectional Delay Variation

16 - Unidirectional Link Loss

16 - Unidirectional Residual Bandwidth

18 - Unidirectional Available Bandwidth

19 - Unidirectional Utilized Bandwidth

20 - Administrative Group

21 - Extended Administrative Group

22 - TE Metric

23 - Maximum Link Bandwidth

24 - Local Interface IPv6 Address Sub-TLV

25 - Remote Interface IPv6 Address Sub-TLV

13.

15. Contributors

The following people contributed to the content of this document and
should be considered as co-authors:

Acee Lindem
Cisco Systems
301 Midenhall Way
Cary, NC 27513
USA

Email: acee@cisco.com

Ketan Talaulikar
Cisco Systems, Inc.
India

Email: ketant@cisco.com

Hannes Gredler
RtBrick Inc.
Austria

Email: hannes@rtbrick.com

14.

16. Acknowledgments

Thanks to Chris Bowers for his review and comments.

15.

Thanks to Alvaro Retana for his detailed review and comments.

17. References

15.1.

17.1. Normative References

[I-D.ietf-isis-te-app]
Ginsberg, L., Psenak, P., Previdi, S., Henderickx, W., and
J. Drake, "IS-IS TE Attributes per application", draft-
ietf-isis-te-app-12 (work in progress), March 2020.

[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>.

[RFC4203] Kompella, K., Ed. and Y. Rekhter, Ed., "OSPF Extensions in
Support of Generalized Multi-Protocol Label Switching
(GMPLS)", RFC 4203, DOI 10.17487/RFC4203, October 2005,
<https://www.rfc-editor.org/info/rfc4203>.

[RFC5329] Ishiguro, K., Manral, V., Davey, A., and A. Lindem, Ed.,
"Traffic Engineering Extensions to OSPF Version 3",
RFC 5329, DOI 10.17487/RFC5329, September 2008,
<https://www.rfc-editor.org/info/rfc5329>.

[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>.

[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>.

[RFC7471] Giacalone, S., Ward, D., Drake, J., Atlas, A., and S.
Previdi, "OSPF Traffic Engineering (TE) Metric
Extensions", RFC 7471, DOI 10.17487/RFC7471, March 2015,
<https://www.rfc-editor.org/info/rfc7471>.

[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>.

[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>.

[RFC8362] Lindem, A., Roy, A., Goethals, D., Reddy Vallem, V., and
F. Baker, "OSPFv3 Link State Advertisement (LSA)
Extensibility", RFC 8362, DOI 10.17487/RFC8362, April
2018, <https://www.rfc-editor.org/info/rfc8362>.

15.2.

17.2. Informative References

[I-D.ietf-isis-te-app]
Ginsberg, L., Psenak, P., Previdi,

[I-D.ietf-spring-segment-routing-policy]
Filsfils, C., Sivabalan, S., Henderickx, W., Voyer, D., Bogdanov, A., and
J. Drake, "IS-IS TE Attributes per application",
P. Mattes, "Segment Routing Policy Architecture", draft-
ietf-isis-te-app-08
ietf-spring-segment-routing-policy-06 (work in progress), October
December 2019.

[RFC2328] Moy, J., "OSPF Version 2", STD 54, RFC 2328,
DOI 10.17487/RFC2328, April 1998,
<https://www.rfc-editor.org/info/rfc2328>.

[RFC4203] Kompella, K., Ed.

[RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V.,
and Y. Rekhter, Ed., "OSPF G. Swallow, "RSVP-TE: Extensions in
Support of Generalized Multi-Protocol Label Switching
(GMPLS)", to RSVP for LSP
Tunnels", RFC 4203, 3209, DOI 10.17487/RFC4203, October 2005,
<https://www.rfc-editor.org/info/rfc4203>. 10.17487/RFC3209, December 2001,
<https://www.rfc-editor.org/info/rfc3209>.

[RFC4552] Gupta, M. and N. Melam, "Authentication/Confidentiality
for OSPFv3", RFC 4552, DOI 10.17487/RFC4552, June 2006,
<https://www.rfc-editor.org/info/rfc4552>.

[RFC5286] Atlas, A., Ed. and A. Zinin, Ed., "Basic Specification for
IP Fast Reroute: Loop-Free Alternates", RFC 5286,
DOI 10.17487/RFC5286, September 2008,
<https://www.rfc-editor.org/info/rfc5286>.

[RFC5709] Bhatia, M., Manral, V., Fanto, M., White, R., Barnes, M.,
Li, T., and R. Atkinson, "OSPFv2 HMAC-SHA Cryptographic
Authentication", RFC 5709, DOI 10.17487/RFC5709, October
2009, <https://www.rfc-editor.org/info/rfc5709>.

[RFC5714] Shand, M. and S. Bryant, "IP Fast Reroute Framework",
RFC 5714, DOI 10.17487/RFC5714, January 2010,
<https://www.rfc-editor.org/info/rfc5714>.

[RFC7166] Bhatia, M., Manral, V., and A. Lindem, "Supporting
Authentication Trailer for OSPFv3", RFC 7166,
DOI 10.17487/RFC7166, March 2014,
<https://www.rfc-editor.org/info/rfc7166>.

[RFC7474] Bhatia, M., Hartman, S., Zhang, D., and A. Lindem, Ed.,
"Security Extension for OSPFv2 When Using Manual Key
Management", RFC 7474, DOI 10.17487/RFC7474, April 2015,
<https://www.rfc-editor.org/info/rfc7474>.

[RFC7490] Bryant, S., Filsfils, C., Previdi, S., Shand, M., and N.
So, "Remote Loop-Free Alternate (LFA) Fast Reroute (FRR)",
RFC 7490, DOI 10.17487/RFC7490, April 2015,
<https://www.rfc-editor.org/info/rfc7490>.

[RFC7855] Previdi, S., Ed., Filsfils, C., Ed., Decraene, B.,
Litkowski, S., Horneffer, M., and R. Shakir, "Source
Packet Routing in Networking (SPRING) Problem Statement
and Requirements", RFC 7855, DOI 10.17487/RFC7855, May
2016, <https://www.rfc-editor.org/info/rfc7855>.

[RFC7916] Litkowski, S., Ed., Decraene, B., Filsfils, C., Raza, K.,
Horneffer, M., and P. Sarkar, "Operational Management of
Loop-Free Alternates", RFC 7916, DOI 10.17487/RFC7916,
July 2016, <https://www.rfc-editor.org/info/rfc7916>.

[RFC8102] Sarkar, P., Ed., Hegde, S., Bowers, C., Gredler, H., and
S. Litkowski, "Remote-LFA Node Protection and
Manageability", RFC 8102, DOI 10.17487/RFC8102, March
2017, <https://www.rfc-editor.org/info/rfc8102>.

Authors' Addresses
Peter Psenak (editor)
Cisco Systems
Eurovea Centre, Central 3
Pribinova Street 10
Bratislava 81109
Slovakia

Email: ppsenak@cisco.com

Les Ginsberg
Cisco Systems
821 Alder Drive
MILPITAS, CA 95035
USA

Email: ginsberg@cisco.com

Wim Henderickx
Nokia
Copernicuslaan 50
Antwerp, 2018 94089
Belgium

Email: wim.henderickx@nokia.com

Jeff Tantsura
Apstra
US

Email: jefftant.ietf@gmail.com

John Drake
Juniper Networks
1194 N. Mathilda Ave
Sunnyvale, California 94089
USA

Email: jdrake@juniper.net