draft-ietf-isis-te-app-13.txt   draft-ietf-isis-te-app-14.txt 
Networking Working Group L. Ginsberg Networking Working Group L. Ginsberg
Internet-Draft P. Psenak Internet-Draft P. Psenak
Intended status: Standards Track Cisco Systems Intended status: Standards Track Cisco Systems
Expires: November 19, 2020 S. Previdi Expires: December 5, 2020 S. Previdi
Huawei Huawei
W. Henderickx W. Henderickx
Nokia Nokia
J. Drake J. Drake
Juniper Networks Juniper Networks
May 18, 2020 June 3, 2020
IS-IS TE Attributes per application IS-IS TE Attributes per application
draft-ietf-isis-te-app-13 draft-ietf-isis-te-app-14
Abstract Abstract
Existing traffic engineering related link attribute advertisements Existing traffic engineering related link attribute advertisements
have been defined and are used in RSVP-TE deployments. Since the have been defined and are used in RSVP-TE deployments. Since the
original RSVP-TE use case was defined, additional applications (e.g., original RSVP-TE use case was defined, additional applications (e.g.,
Segment Routing Traffic Engineering, Loop Free Alternate) have been Segment Routing Traffic Engineering, Loop Free Alternate) have been
defined which also make use of the link attribute advertisements. In defined which also make use of the link attribute advertisements. In
cases where multiple applications wish to make use of these link cases where multiple applications wish to make use of these link
attributes the current advertisements do not support application attributes the current advertisements do not support application
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/. Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on November 19, 2020. This Internet-Draft will expire on December 5, 2020.
Copyright Notice Copyright Notice
Copyright (c) 2020 IETF Trust and the persons identified as the Copyright (c) 2020 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of (https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Requirements Discussion . . . . . . . . . . . . . . . . . . . 4 2. Requirements Discussion . . . . . . . . . . . . . . . . . . . 4
3. Legacy Advertisements . . . . . . . . . . . . . . . . . . . . 4 3. Legacy Advertisements . . . . . . . . . . . . . . . . . . . . 4
3.1. Legacy sub-TLVs . . . . . . . . . . . . . . . . . . . . . 5 3.1. Legacy sub-TLVs . . . . . . . . . . . . . . . . . . . . . 5
3.2. Legacy SRLG Advertisements . . . . . . . . . . . . . . . 5 3.2. Legacy SRLG Advertisements . . . . . . . . . . . . . . . 5
4. Advertising Application Specific Link Attributes . . . . . . 6 4. Advertising Application Specific Link Attributes . . . . . . 6
4.1. Application Identifier Bit Mask . . . . . . . . . . . . . 6 4.1. Application Identifier Bit Mask . . . . . . . . . . . . . 6
4.2. Application Specific Link Attributes sub-TLV . . . . . . 8 4.2. Application Specific Link Attributes sub-TLV . . . . . . 8
4.2.1. Special Considerations for Maximum Link Bandwidth . . 9 4.2.1. Special Considerations for Maximum Link Bandwidth . . 10
4.2.2. Special Considerations for Reservable/Unreserved 4.2.2. Special Considerations for Reservable/Unreserved
Bandwidth . . . . . . . . . . . . . . . . . . . . . . 10 Bandwidth . . . . . . . . . . . . . . . . . . . . . . 10
4.2.3. Considerations for Extended TE Metrics . . . . . . . 10 4.2.3. Considerations for Extended TE Metrics . . . . . . . 10
4.3. Application Specific SRLG TLV . . . . . . . . . . . . . . 10 4.3. Application Specific SRLG TLV . . . . . . . . . . . . . . 11
5. Attribute Advertisements and Enablement . . . . . . . . . . . 11 5. Attribute Advertisements and Enablement . . . . . . . . . . . 12
6. Deployment Considerations . . . . . . . . . . . . . . . . . . 12 6. Deployment Considerations . . . . . . . . . . . . . . . . . . 13
6.1. Use of Legacy Advertisements . . . . . . . . . . . . . . 12 6.1. Use of Legacy Advertisements . . . . . . . . . . . . . . 13
6.2. Use of Zero Length Application Identifier Bit Masks . . . 13 6.2. Use of Zero Length Application Identifier Bit Masks . . . 13
6.3. Interoperability, Backwards Compatibility and Migration 6.3. Interoperability, Backwards Compatibility and Migration
Concerns . . . . . . . . . . . . . . . . . . . . . . . . 14 Concerns . . . . . . . . . . . . . . . . . . . . . . . . 14
6.3.1. Multiple Applications: Common Attributes with RSVP- 6.3.1. Multiple Applications: Common Attributes with RSVP-
TE . . . . . . . . . . . . . . . . . . . . . . . . . 14 TE . . . . . . . . . . . . . . . . . . . . . . . . . 14
6.3.2. Multiple Applications: All Attributes Not Shared with 6.3.2. Multiple Applications: All Attributes Not Shared with
RSVP-TE . . . . . . . . . . . . . . . . . . . . . . . 14 RSVP-TE . . . . . . . . . . . . . . . . . . . . . . . 14
6.3.3. Interoperability with Legacy Routers . . . . . . . . 14 6.3.3. Interoperability with Legacy Routers . . . . . . . . 15
6.3.4. Use of Application Specific Advertisements for RSVP- 6.3.4. Use of Application Specific Advertisements for RSVP-
TE . . . . . . . . . . . . . . . . . . . . . . . . . 15 TE . . . . . . . . . . . . . . . . . . . . . . . . . 15
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 15 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16
7.1. Application Specific Link Attributes sub-TLV . . . . . . 16 7.1. Application Specific Link Attributes sub-TLV . . . . . . 16
7.2. Application Specific SRLG TLV . . . . . . . . . . . . . . 16 7.2. Application Specific SRLG TLV . . . . . . . . . . . . . . 16
7.3. Application Specific Link Attributes sub-sub-TLV Registry 16 7.3. Application Specific Link Attributes sub-sub-TLV Registry 16
7.4. Link Attribute Application Identifier Registry . . . . . 17 7.4. Link Attribute Application Identifier Registry . . . . . 17
7.5. SRLG sub-TLVs . . . . . . . . . . . . . . . . . . . . . . 18 7.5. SRLG sub-TLVs . . . . . . . . . . . . . . . . . . . . . . 18
8. Security Considerations . . . . . . . . . . . . . . . . . . . 18 8. Security Considerations . . . . . . . . . . . . . . . . . . . 18
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 19 9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 19
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 19 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 19
10.1. Normative References . . . . . . . . . . . . . . . . . . 19 10.1. Normative References . . . . . . . . . . . . . . . . . . 19
10.2. Informative References . . . . . . . . . . . . . . . . . 20 10.2. Informative References . . . . . . . . . . . . . . . . . 20
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already exists in IS-IS, it is only necessary to discuss use cases already exists in IS-IS, it is only necessary to discuss use cases
which justify the key points identified in the introduction - which which justify the key points identified in the introduction - which
are: are:
1. Support for indicating which applications are using the link 1. Support for indicating which applications are using the link
attribute advertisements on a link attribute advertisements on a link
2. Support for advertising application specific values for the same 2. Support for advertising application specific values for the same
attribute on a link attribute on a link
[RFC7855] discusses use cases/requirements for SR. Included among [RFC7855] discusses use cases/requirements for Segment Routing (SR).
these use cases is SRTE which is defined in Included among these use cases is SRTE which is defined in
[I-D.ietf-spring-segment-routing-policy]. If both RSVP-TE and SRTE [I-D.ietf-spring-segment-routing-policy]. If both RSVP-TE and SRTE
are deployed in a network, link attribute advertisements can be used are deployed in a network, link attribute advertisements can be used
by one or both of these applications. As there is no requirement for by one or both of these applications. As there is no requirement for
the link attributes advertised on a given link used by SRTE to be the link attributes advertised on a given link used by SRTE to be
identical to the link attributes advertised on that same link used by identical to the link attributes advertised on that same link used by
RSVP-TE, there is a clear requirement to indicate independently which RSVP-TE, there is a clear requirement to indicate independently which
link attribute advertisements are to be used by each application. link attribute advertisements are to be used by each application.
As the number of applications which may wish to utilize link As the number of applications which may wish to utilize link
attributes may grow in the future, an additional requirement is that attributes may grow in the future, an additional requirement is that
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Finally, there may still be many cases where a single attribute value Finally, there may still be many cases where a single attribute value
can be shared among multiple applications, so the solution must can be shared among multiple applications, so the solution must
minimize advertising duplicate link/attribute pairs whenever minimize advertising duplicate link/attribute pairs whenever
possible. possible.
3. Legacy Advertisements 3. Legacy Advertisements
There are existing advertisements used in support of RSVP-TE. These There are existing advertisements used in support of RSVP-TE. These
advertisements include sub-TLVs for TLVs 22, 23, 25, 141, 222, and advertisements include sub-TLVs for TLVs 22, 23, 25, 141, 222, and
223 and TLVs for Shared Risk Link Group(SRLG) advertisement. 223 and TLVs for Shared Risk Link Group (SRLG) advertisement.
Sub-TLV values are defined in https://www.iana.org/assignments/isis- Sub-TLV values are defined in https://www.iana.org/assignments/isis-
tlv-codepoints/isis-tlv-codepoints.xhtml#isis-tlv-codepoints- tlv-codepoints/isis-tlv-codepoints.xhtml#isis-tlv-codepoints-
22-23-25-141-222-223 and https://www.iana.org/assignments/isis-tlv- 22-23-25-141-222-223 and https://www.iana.org/assignments/isis-tlv-
codepoints/isis-tlv-codepoints.xhtml . codepoints/isis-tlv-codepoints.xhtml .
3.1. Legacy sub-TLVs 3.1. Legacy sub-TLVs
Sub-TLVs for TLVs 22, 23, 25, 141, 222, and 223 Sub-TLVs for TLVs 22, 23, 25, 141, 222, and 223
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| ... | ...
+-+-+-+-+-+-+-+-+... +-+-+-+-+-+-+-+-+...
This field is omitted if UDABM Length is 0. This field is omitted if UDABM Length is 0.
NOTE: SABM/UDABM Length is arbitrarily limited to 8 octets in order NOTE: SABM/UDABM Length is arbitrarily limited to 8 octets in order
to insure that sufficient space is left to advertise link attributes to insure that sufficient space is left to advertise link attributes
without overrunning the maximum length of a sub-TLV. without overrunning the maximum length of a sub-TLV.
Standard Application Identifier Bits are defined/sent starting with Standard Application Identifier Bits are defined/sent starting with
Bit 0. Undefined bits MUST be transmitted as 0 and MUST be ignored Bit 0. Undefined bits which are transmitted MUST be transmitted as 0
on receipt. Bits that are NOT transmitted MUST be treated as if they and MUST be ignored on receipt. Bits that are not transmitted MUST
are set to 0 on receipt. Bits that are not supported by an be treated as if they are set to 0 on receipt. Bits that are not
implementation MUST be ignored on receipt. supported by an implementation MUST be ignored on receipt.
User Defined Application Identifier Bits have no relationship to User Defined Application Identifier Bits have no relationship to
Standard Application Identifier Bits and are NOT managed by IANA or Standard Application Identifier Bits and are not managed by IANA or
any other standards body. It is recommended that bits are used any other standards body. It is recommended that bits are used
starting with Bit 0 so as to minimize the number of octets required starting with Bit 0 so as to minimize the number of octets required
to advertise all UDAs. to advertise all UDAs.
4.2. Application Specific Link Attributes sub-TLV 4.2. Application Specific Link Attributes sub-TLV
A new sub-TLV for TLVs 22, 23, 25, 141, 222, and 223 is defined which A new sub-TLV for TLVs 22, 23, 25, 141, 222, and 223 is defined which
supports specification of the applications and application specific supports specification of the applications and application specific
attribute values. attribute values.
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Length: Variable (1 octet) Length: Variable (1 octet)
Value: Value:
Application Identifier Bit Mask Application Identifier Bit Mask
(as defined in Section 4.1) (as defined in Section 4.1)
Link Attribute sub-sub-TLVs - format matches the Link Attribute sub-sub-TLVs - format matches the
existing formats defined in [RFC5305], [RFC7308], existing formats defined in [RFC5305], [RFC7308],
and [RFC8570] and [RFC8570]
If the SABM or UDABM length in the Application Identifer Bit Mask is
greater than 8, the entire sub-TLV MUST be ignored.
When the L-flag is set in the Application Identifier Bit Mask, all of When the L-flag is set in the Application Identifier Bit Mask, all of
the applications specified in the bit mask MUST use the legacy the applications specified in the bit mask MUST use the legacy
advertisements for the corresponding link found in TLVs 22, 23, 25, advertisements for the corresponding link found in TLVs 22, 23, 25,
141, 222, and 223 or TLV 138 or TLV 139 as appropriate. Link 141, 222, and 223 or TLV 138 or TLV 139 as appropriate. Link
attribute sub-sub-TLVs for the corresponding link attributes MUST NOT attribute sub-sub-TLVs for the corresponding link attributes MUST NOT
be advertised for the set of applications specified in the Standard/ be advertised for the set of applications specified in the Standard/
User Application Identifier Bit Masks and all such advertisements User Application Identifier Bit Masks and all such advertisements
MUST be ignored on receipt. MUST be ignored on receipt.
Multiple Application Specific Link Attribute sub-TLVs for the same Multiple Application Specific Link Attribute sub-TLVs for the same
link MAY be advertised. When multiple sub-TLVs for the same link are link MAY be advertised. When multiple sub-TLVs for the same link are
advertised, they SHOULD advertise non-conflicting application/ advertised, they SHOULD advertise non-conflicting application/
attribute pairs. A conflict exists when the same application is attribute pairs. A conflict exists when the same application is
associated with two different values of the same link attribute for a associated with two different values of the same link attribute for a
given link. In cases where conflicting values for the same given link. In cases where conflicting values for the same
application/attribute/link are advertised all the conflicting values application/attribute/link are advertised all the conflicting values
MUST be ignored. MUST be ignored by the specified application.
For a given application, the setting of the L-flag MUST be the same For a given application, the setting of the L-flag MUST be the same
in all sub-TLVs for a given link. In cases where this constraint is in all sub-TLVs for a given link. In cases where this constraint is
violated, the L-flag MUST be considered set for this application. violated, the L-flag MUST be considered set for this application.
If link attributes are advertised associated with zero length
Application Identifier 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 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.
A new registry of sub-sub-TLVs is to be created by IANA which defines A new registry of sub-sub-TLVs is to be created by IANA which defines
the link attribute sub-sub-TLV code points. This document defines a the link attribute sub-sub-TLV code points. This document defines a
sub-sub-TLV for each of the existing sub-TLVs listed in Section 3.1 sub-sub-TLV for each of the existing sub-TLVs listed in Section 3.1
except as noted below. The format of the sub-sub-TLVs matches the except as noted below. The format of the sub-sub-TLVs matches the
format of the corresponding legacy sub-TLV and IANA is requested to format of the corresponding legacy sub-TLV and IANA is requested to
assign the legacy sub-TLV identifier to the corresponding sub-sub- assign the legacy sub-TLV identifier to the corresponding sub-sub-
TLV. TLV.
4.2.1. Special Considerations for Maximum Link Bandwidth 4.2.1. Special Considerations for Maximum Link Bandwidth
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Whether the presence of link attribute advertisements for a given Whether the presence of link attribute advertisements for a given
application indicates that the application is enabled on that link application indicates that the application is enabled on that link
depends upon the application. Similarly, whether the absence of link depends upon the application. Similarly, whether the absence of link
attribute advertisements indicates that the application is not attribute advertisements indicates that the application is not
enabled depends upon the application. enabled depends upon the application.
In the case of RSVP-TE, the advertisement of application specific In the case of RSVP-TE, the advertisement of application specific
link attributes implies that RSVP is enabled on that link. The link attributes implies that RSVP is enabled on that link. The
absence of RSVP-TE application specific link attributes in absence of RSVP-TE application specific link attributes in
combination with the absence of legacy advertisements implies that combination with the absence of legacy advertisements implies that
RSVP is NOT enabled on that link. RSVP is not enabled on that link.
In the case of SRTE, advertisement of application specific link In the case of SRTE, advertisement of application specific link
attributes does NOT indicate enablement of SRTE. The advertisements attributes does not indicate enablement of SRTE on that link. The
are only used to support constraints which may be applied when advertisements are only used to support constraints which may be
specifying an explicit path. SRTE is implicitly enabled on all links applied when specifying an explicit path. SRTE is implicitly enabled
which are part of the Segment Routing enabled topology independent of on all links which are part of the Segment Routing enabled topology
the existence of link attribute advertisements independent of the existence of link attribute advertisements
In the case of LFA, advertisement of application specific link In the case of LFA, advertisement of application specific link
attributes does NOT indicate enablement of LFA on that link. attributes does not indicate enablement of LFA on that link.
Enablement is controlled by local configuration. Enablement is controlled by local configuration.
If, in the future, additional standard applications are defined to If, in the future, additional standard applications are defined to
use this mechanism, the specification defining this use MUST define use this mechanism, the specification defining this use MUST define
the relationship between application specific link attribute the relationship between application specific link attribute
advertisements and enablement for that application. advertisements and enablement for that application.
This document allows the advertisement of application specific link This document allows the advertisement of application specific link
attributes with no application identifiers i.e., both the Standard attributes with no application identifiers i.e., both the Standard
Application Identifier Bit Mask and the User Defined Application Application Identifier Bit Mask and the User Defined Application
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the associated issues can be found in Section 6.3. the associated issues can be found in Section 6.3.
New applications which future documents define to make use of the New applications which future documents define to make use of the
advertisements defined in this document MUST NOT make use of legacy advertisements defined in this document MUST NOT make use of legacy
advertisements. This simplifies deployment of new applications by advertisements. This simplifies deployment of new applications by
eliminating the need to support multiple ways to advertise attributes eliminating the need to support multiple ways to advertise attributes
for the new applications. for the new applications.
6.2. Use of Zero Length Application Identifier Bit Masks 6.2. Use of Zero Length Application Identifier Bit Masks
If link attributes are advertised associated with zero length Link attribute advertisements associated with zero length Application
Application Identifier Bit Masks for both standard applications and Identifier Bit Masks for both standard applications and user defined
user defined applications, then any Standard Application and/or any applications are usable by any application, subject to the
User Defined Application is permitted to use that set of link restrictions specified in Section 4.2. If support for a new
attributes so long as there is not another set of attributes application is introduced on any node in a network in the presence of
advertised on that same link which is associated with a non-zero such advertisements, these advertisements are permitted to be used by
length Application Identifier Bit Mask with a matching Application the new application. If this is not what is intended, then existing
Identifier Bit set. If support for a new application is introduced advertisements MUST be readvertised with an explicit set of
on any node in a network in the presence of such advertisements, applications specified before a new application is introduced.
these advertisements 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.
6.3. Interoperability, Backwards Compatibility and Migration Concerns 6.3. Interoperability, Backwards Compatibility and Migration Concerns
Existing deployments of RSVP-TE, SRTE, and/or LFA utilize the legacy Existing deployments of RSVP-TE, SRTE, and/or LFA utilize the legacy
advertisements listed in Section 3. Routers which do not support the advertisements listed in Section 3. Routers which do not support the
extensions defined in this document will only process legacy extensions defined in this document will only process legacy
advertisements and are likely to infer that RSVP-TE is enabled on the advertisements and are likely to infer that RSVP-TE is enabled on the
links for which legacy advertisements exist. It is expected that links for which legacy advertisements exist. It is expected that
deployments using the legacy advertisements will persist for a deployments using the legacy advertisements will persist for a
significant period of time. Therefore deployments using the significant period of time. Therefore deployments using the
extensions defined in this document must be able to co-exist with use extensions defined in this document in the presence of routers which
of the legacy advertisements by routers which do not support the do not support these extensions need to be able to interoperate with
extensions defined in this document. The following sub-sections the use of legacy advertisements by the legacy routers. The
discuss interoperability and backwards compatibility concerns for a following sub-sections discuss interoperability and backwards
number of deployment scenarios. compatibility concerns for a number of deployment scenarios.
6.3.1. Multiple Applications: Common Attributes with RSVP-TE 6.3.1. Multiple Applications: Common Attributes with RSVP-TE
In cases where multiple applications are utilizing a given link, one In cases where multiple applications are utilizing a given link, one
of the applications is RSVP-TE, and all link attributes for a given of the applications is RSVP-TE, and all link attributes for a given
link are common to the set of applications utilizing that link, link are common to the set of applications utilizing that link,
interoperability is achieved by using legacy advertisements and interoperability is achieved by using legacy advertisements and
sending application specific advertisements with L-flag set and no sending application specific advertisements with L-flag set and no
link attribute values. This avoids duplication of link attribute link attribute values. This avoids duplication of link attribute
advertisements. advertisements.
6.3.2. Multiple Applications: All Attributes Not Shared with RSVP-TE 6.3.2. Multiple Applications: All Attributes Not Shared with RSVP-TE
In cases where one or more applications other than RSVP-TE are 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 utilizing a given link and one or more link attribute values are not
shared with RSVP-TE, it is necessary to use application specific shared with RSVP-TE, it is necessary to use application specific
advertisements as defined in this document. Attributes for advertisements as defined in this document. Attributes for
applications other than RSVP-TE MUST be advertised using application applications other than RSVP-TE MUST be advertised using application
specific advertisements which have the L-flag clear. In cases where specific advertisements which have the L-flag clear. In cases where
some link attributes are shared with RSVP-TE, this requires duplicate some link attributes are shared with RSVP-TE, this requires duplicate
advertisements for those attributes. advertisements for those attributes.
The discussion in this section applies to cases where RSVP-TE is NOT The discussion in this section applies to cases where RSVP-TE is not
using any advertised attributes on a link and to cases where RSVP-TE using any advertised attributes on a link and to cases where RSVP-TE
is using some link attribute advertisements on the link but some link is using some link attribute advertisements on the link but some link
attributes cannot be shared with RSVP-TE. attributes cannot be shared with RSVP-TE.
6.3.3. Interoperability with Legacy Routers 6.3.3. Interoperability with Legacy Routers
For the applications defined in this document, routers which do not For the applications defined in this document, routers which do not
support the extensions defined in this document will send and receive support the extensions defined in this document will send and receive
only legacy link attribute advertisements. So long as there is any only legacy link attribute advertisements. So long as there is any
legacy router in the network which has any of the applications legacy router in the network which has any of the applications
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