Networking Working Group L. Ginsberg
Internet-Draft P. Psenak
Intended status: Standards Track S. Previdi
Expires: December 2, 2017 Cisco Systems
W. Henderickx
Nokia
May 31, 2017
IS-IS TE Attributes per application
draft-ginsberg-isis-te-app-01.txt
Abstract
Existing traffic engineering related link attribute advertisements
have been defined and are used in RSVP-TE deployments. In cases
where multiple applications wish to 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 draft introduces new link attribute advertisements which address
both of these shortcomings. It also discusses backwards
compatibility issues and how to minimize duplicate advertisements in
the presence of routers which do not support the extensions defined
in this document.
Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].
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 http://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."
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This Internet-Draft will expire on December 2, 2017.
Copyright Notice
Copyright (c) 2017 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
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the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Requirements Discussion . . . . . . . . . . . . . . . . . . . 3
3. Legacy Advertisements . . . . . . . . . . . . . . . . . . . . 4
3.1. Legacy sub-TLVs . . . . . . . . . . . . . . . . . . . . . 4
3.2. Legacy SRLG Advertisements . . . . . . . . . . . . . . . 5
4. Advertising Application Specific Link Attributes . . . . . . 5
4.1. Application Bit Mask . . . . . . . . . . . . . . . . . . 6
4.2. Application Specific Link Attributes sub-TLV . . . . . . 7
4.3. Application Specific SRLG TLV . . . . . . . . . . . . . . 8
5. Interoperability, Backwards Compatibility and Migration
Concerns . . . . . . . . . . . . . . . . . . . . . . . . . . 9
5.1. RSVP-TE only deployments . . . . . . . . . . . . . . . . 9
5.2. Multiple Applications: Common Attributes with RSVP-TE . 9
5.3. Multiple Applications: All Attributes Not Shared w RSVP-
TE . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
5.4. Deprecating legacy advertisements . . . . . . . . . . . . 10
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10
7. Security Considerations . . . . . . . . . . . . . . . . . . . 12
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 12
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 12
9.1. Normative References . . . . . . . . . . . . . . . . . . 12
9.2. Informative References . . . . . . . . . . . . . . . . . 13
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 13
1. Introduction
Advertisement of link attributes by the Intermediate-System-to-
Intermediate-System (IS-IS) protocol in support of traffic
engineering (TE) was introduced by [RFC5305] and extended by
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[RFC5307], [RFC6119], and [RFC7810]. Use of these extensions has
been associated with deployments supporting Traffic Engineering over
Multiprotocol Label Switching (MPLS) in the presence of Resource
Reservation Protocol (RSVP) - more succinctly referred to as RSVP-TE.
Although implementations vary in their exact interpretation, it is
fair to say that the presence of any of the link attribute
advertisements currently defined (excluding link identifier
advertisements) are used by many implementations to imply the use of
that link by RSVP-TE.
In recent years new applications have been introduced which have use
cases for many of the link attributes historically used by RSVP-TE.
Such applications include Segment Routing Traffic Engineering (SR-TE)
and Loop Free Alternates (LFA). This has introduced ambiguity in
that if a deployment includes a mix of RSVP-TE support and SR-TE
support (for example) it is not possible to unambiguously indicate
which advertisements indicate support for/use by RSVP-TE and which
advertisements indicate support for/use by SR-TE. If the topologies
are fully congruent this may not be an issue, but any incongruence
leads to ambiguity.
An additional issue arises in cases where both applications are
supported on a link but the link attribute values associated with
each application differ. Current advertisements do not support
advertising application specific values for the same attribute on a
specific link.
This document defines extensions which address these issues. Also,
as evolution of use cases for link attributes can be expected to
continue in the years to come, this document defines a solution which
is easily extensible to the introduction of new applications and new
use cases.
2. Requirements Discussion
As stated previously, evolution of use cases for link attributes can
be expected to continue - so any discussion of existing use cases is
limited to requirements which are known at the time of this writing.
However, in order to determine the functionality required beyond what
already exists in IS-IS, it is only necessary to discuss use cases
which justify the key points identified in the introduction - which
are:
1. Support for indicating which applications are using the link
attribute advertisements on a link
2. Support for advertising application specific values for the same
attribute on a link
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[RFC7855] discusses use cases/requirements for SR. Included among
these use cases is SR-TE. If both RSVP-TE and SR-TE are deployed in
a network, links can be used by one or both of these applications.
As there is no requirement for the topology supported for SR-TE to be
congruent to the topology supported for RSVP-TE, there is a clear
requirement to indicate independently which applications are
associated with a given link.
If both RSVP-TE and SR-TE are enabled on a given link, it is also
possible that an attribute value such as Maximum Bandwidth to be
utilized by SR-TE may be different than/disjoint from the Maximum
Bandwidth to be utilized by RSVP-TE. This leads to the requirement
that the solution support the advertisement of unique values for a
given link/attribute/application.
As the number of applications which may wish to utilize link
attributes may grow in the future, an additional requirement is that
the extensions defined allow the association of additional
applications to link attributes without altering the format of the
advertisements or introducing new backwards compatibility issues.
Finally, there may still be many cases where a single attribute value
can be shared among multiple applications, so the solution must
minimize advertising duplicate link/attribute pairs whenever
possible.
3. Legacy Advertisements
There are existing advertisements used in support of RSVP-TE. These
advertisements include sub-TLVs for TLVs 22, 23, 141, 222, and 223
and TLVs for SRLG advertisement.
3.1. Legacy sub-TLVs
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Sub-TLVs for TLVs 22, 23, 141, 222, and 223
Code Point/Attribute Name
--------------------------
3 Administrative group (color)
9 Maximum link bandwidth
10 Maximum reservable link bandwidth
11 Unreserved bandwidth
14 Extended Administrative Group
33 Unidirectional Link Delay
34 Min/Max Unidirectional Link Delay
35 Unidirectional Delay Variation
36 Unidirectional Link Loss
37 Unidirectional Residual Bandwidth
38 Unidirectional Available Bandwidth
39 Unidirectional Utilized Bandwidth
3.2. Legacy SRLG Advertisements
TLV 138 GMPLS-SRLG
Supports links identified by IPv4 addresses and
unnumbered links
TLV 139 IPv6 SRLG
Supports links identified by IPv6 addresses
Note that [RFC6119] prohibits the use of TLV 139 when it is possible
to use TLV 138.
4. Advertising Application Specific Link Attributes
Two new code points are defined in support of Application Specific
Link Attribute Advertisements:
1) Application Specific Link Attributes sub-TLV for TLVs 22, 23, 141,
222, and 223
2)Application Specific Shared Risk Link Group (SRLG) TLV
In support of these new advertisements, an application bit mask is
defined which identifies the application(s) associated with a given
advertisement.
The following sections define the format of these new advertisements.
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4.1. Application Bit Mask
Identification of the set of applications associated with the link
attribute advertisements utilizes a bit mask where the definition of
each bit is defined in a new IANA controlled registry. This encoding
is used by both the Application Specific Link Attributes sub-TLV and
the Application Specific SRLG TLV.
Bit Mask Length: Non-zero (1 octet)
Application Bit Mask: Size is (Bit Mask Length+7)/8
The following bits are assigned/reserved:
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|L|R|S|F| | UDA Use |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
L-bit: Applications listed MUST use the legacy
advertisements for the corresponding link
found in TLVs 22, 23, 141, 222, and 223 or
TLV 138 or TLV 139 as appropriate.
R-bit: RSVP-TE
S-bit: Segment Routing Traffic Engineering
F-bit: Loop Free Alternate
UDA Use: These bits are reserved for User Defined
Application (UDA) use. These bits MUST NOT be
assigned by IANA for any standards based use.
Bits are defined/sent starting with Bit 0. Additional bit
definitions that may be defined in the future SHOULD be assigned in
ascending bit order so as to minimize the number of bits that will
need to be transmitted. Undefined bits 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.
The second octet is reserved for local use by proprietary and/or
experimental applications. These bits MUST NOT be assigned by IANA
for any standards based use. IANA owns the assignment of bits 0 - 7
and bits 16 and greater.
Note that the octet associated with UDA Use need only be transmitted
if any of the following conditions is met:
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o One of the UDA bits is set
o Bit 16 or greater is set
4.2. Application Specific Link Attributes sub-TLV
A new sub-TLV for TLVs 22, 23, 141, 222, and 223 is defined which
supports specification of the applications and application specific
attribute values.
Type: 15 (suggested value - to be assigned by IANA)
Length: Variable (1 octet)
Value:
Application Bit Mask (as defined in Section 3.1)
Link Attribute sub-sub-TLVs - format matches the
existing formats defined in [RFC5305] and [RFC7810]
When the L-bit is set in the Application Bit Mask, all of the
applications specified in the bit mask MUST use the link attribute
sub-TLV advertisements listed in Section 3.1 for the corresponding
link. Application specific link attribute sub-sub-TLVs for the
corresponding link attributes MUST NOT be advertised for the set of
applications specified in the Application Bit Mask and all such
advertisements MUST be ignored on receipt.
Multiple sub-TLVs for the same link MAY be advertised. When multiple
sub-TLVs for the same link are advertised, they SHOULD advertise non-
conflicting application/attribute pairs. In cases where there are
multiple sub-TLVs for the same link and there is a conflict in the
attribute information advertised the behavior of the receiver is
undefined.
For a given application, the setting of the L-bit MUST be the same in
all sub-TLVs for a given link. In cases where this constraint is
violated, the L-bit MUST be considered set for this application.
A new registry of sub-sub-TLVs is to be created by IANA which defines
the link attribute sub-sub-TLV code points. A sub-sub-TLV is defined
for each of the existing sub-TLVs listed in Section 3.1. Format of
the sub-sub-TLVs matches the format of the corresponding legacy sub-
TLV and IANA is requested to assign the legacy sub-TLV identifer to
the corresponding sub-sub-TLV.
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4.3. Application Specific SRLG TLV
A new TLV is defined to advertise application specific SRLGs for a
given link. Although similar in functionality to TLV 138 (defined by
[RFC5307]) and TLV 139 (defined by [RFC6119], a single TLV provides
support for IPv4, IPv6, and unnumbered identifiers for a link.
Unlike TLVs 138/139, it utilizes sub-TLVs to encode the link
identifiers in order to provide the flexible formatting required to
support multiple link identifier types.
Type: 238 (Suggested value - to be assigned by IANA)
Length: Number of octets in the value field (1 octet)
Value:
Neighbor System-ID + pseudo-node ID (7 octets)
Application Bit Mask (as defined in Section 3.1)
Length of sub-TLVs (1 octet)
Link Identifier sub-TLVs (variable)
0 or more SRLG Values (Each value is 4 octets)
The following Link Identifier sub-TLVs are defined. The type
values are suggested and will be assigned by IANA - but as
the formats are identical to existing sub-TLVs defined for
TLVs 22, 23, 141, 222, and 223 the use of the suggested sub-TLV
types is strongly encouraged.
Type Description
4 Link Local/Remote Identifiers (see [RFC5307])
6 IPv4 interface address (see [RFC5305])
8 IPv4 neighbor address (see [RFC5305])
12 IPv6 Interface Address (see [RFC6119])
13 IPv6 Neighbor Address (see [RFC6119])
At least one set of link identifiers (IPv4, IPv6, or unnumbered) MUST
be present. TLVs which do not meet this requirement MUST be ignored.
Multiple TLVs for the same link MAY be advertised.
When the L-bit is set in the Application Bit Mask, SRLG values MUST
NOT be included in the TLV. Any SRLG values which are advertised
MUST be ignored. Based on the link identifiers advertised the
corresponding legacy TLV (see Section 3.2) can be identified and the
SRLG values advertised in the legacy TLV MUST be used by the set of
applications specified in the Application Bit Mask.
For a given application, the setting of the L-bit MUST be the same in
all TLVs for a given link. In cases where this constraint is
violated, the L-bit MUST be considered set for this application.
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5. Interoperability, Backwards Compatibility and Migration Concerns
Existing deployments of RSVP-TE utilize the legacy advertisements
listed in Section 3. Routers which do not support the extensions
defined in this document will only process legacy advertisements and
are likely to infer that RSVP-TE is enabled on the links for which
legacy advertisements exist. It is expected that deployments using
the legacy advertisements will persist for a significant period of
time - therefore deployments using the extensions defined in this
document must be able to co-exist with use of the legacy
advertisements by routers which do not support the extensions defined
in this document. The following sub-sections discuss
interoperability and backwards compatibility concerns for a number of
deployment scenarios.
Note that in all cases the defined strategy can be employed on a per
link basis.
5.1. RSVP-TE only deployments
In deployments where RSVP-TE is the only application utilizing link
attribute advertisements, use of the the legacy advertisements can
continue without change.
5.2. Multiple Applications: Common Attributes with RSVP-TE
In cases where multiple applications are utilizing a given link, one
of the applications is RSVP-TE, and all link attributes for a given
link are common to the set of applications utilizing that link,
interoperability is achieved by using legacy advertisements and
sending application specific advertisements with L-bit set and no
link attribute values. This avoids duplication of link attribute
advertisements.
5.3. Multiple Applications: All Attributes Not Shared w 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, it is necessary to use application specific
advertisements as defined in this document. Attributes for
applications other than RSVP-TE MUST be advertised using application
specific advertisements which have the L-bit clear. In cases where
some link attributes are shared with RSVP-TE, this requires duplicate
advertisements for those attributes.
The discussion in this section applies to cases where RSVP-TE is NOT
enabled on a link and to cases where RSVP-TE is enabled on the link
but some link attributes cannot be shared with RSVP-TE.
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5.4. Deprecating legacy advertisements
The extensions defined in this document support RSVP-TE as one of the
supported applications - so a long term goal for deployments would be
to deprecate use of the legacy advertisements in support of RSVP-TE.
This can be done in the following step-wise manner:
1)Upgrade all routers to support extensions in this document
2)Readvertise all legacy link attributes using application specific
advertisements with L-bit clear and R-bit set.
3)Remove legacy advertisements
6. IANA Considerations
This document defines a new sub-TLV for TLVs 22, 23, 141, 222, and
223.
Type Description 22 23 141 222 223
---- --------------------- --- --- --- --- ---
15 Application Specific y y y y y
Link Attributes
This document defines one new TLV:
Type Description IIH SNP LSP Purge
---- --------------------- --- --- --- -----
238 Application Specific n n y n
SRLG
This document requests a new IANA registry be created to control the
assignment of sub-sub-TLV codepoints for the Application Specific
Link Attributes sub-TLV. The suggested name of the new registry is
"sub-sub-TLV code points for application link attributes". The
registration procedure is "Expert Review" as defined in [RFC5226].
The following assignments are made by this document:
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Type Description
---------------------------------------------------------
3 Administrative group (color)
9 Maximum link bandwidth
10 Maximum reservable link bandwidth
11 Unreserved bandwidth
14 Extended Administrative Group
33 Unidirectional Link Delay
34 Min/Max Unidirectional Link Delay
35 Unidirectional Delay Variation
36 Unidirectional Link Loss
37 Unidirectional Residual Bandwidth
38 Unidirectional Available Bandwidth
39 Unidirectional Utilized Bandwidth
This document requests a new IANA registry be created to control the
assignment of application bit identifiers. The suggested name of the
new registry is "Link Attribute Applications". The registration
procedure is "Expert Review" as defined in [RFC5226]. The following
assignments are made by this document:
Bit # Name
---------------------------------------------------------
0 Legacy Attributes (L-bit)
1 RSVP-TE (R-bit)
2 Segment Routing Traffic Engineering (S-bit)
3 Loop Free Alternate (F-bit)
4-7 Unassigned
8-15 Reserved for User Defined Application Use
This document requests a new IANA registry be created to control the
assignment of sub-TLV types for the application specific SRLG TLV.
The suggested name of the new registry is "Sub-TLVs for TLV 238".
The registration procedure is "Expert Review" as defined in
[RFC5226]. The following assignments are made by this document:
Value Description
---------------------------------------------------------
4 Link Local/Remote Identifiers (see [RFC5307])
6 IPv4 interface address (see [RFC5305])
8 IPv4 neighbor address (see [RFC5305])
12 IPv6 Interface Address (see [RFC6119])
13 IPv6 Neighbor Address (see [RFC6119])
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7. Security Considerations
Security concerns for IS-IS are addressed in [ISO10589, [RFC5304],
and [RFC5310].
8. Acknowledgements
The authors would like to thank John Drake and Acee Lindem for their
careful review and content suggestions.
9. References
9.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 5226,
DOI 10.17487/RFC5226, May 2008,
<http://www.rfc-editor.org/info/rfc5226>.
[RFC5304] Li, T. and R. Atkinson, "IS-IS Cryptographic
Authentication", RFC 5304, DOI 10.17487/RFC5304, October
2008, <http://www.rfc-editor.org/info/rfc5304>.
[RFC5305] Li, T. and H. Smit, "IS-IS Extensions for Traffic
Engineering", RFC 5305, DOI 10.17487/RFC5305, October
2008, <http://www.rfc-editor.org/info/rfc5305>.
[RFC5307] Kompella, K., Ed. and Y. Rekhter, Ed., "IS-IS Extensions
in Support of Generalized Multi-Protocol Label Switching
(GMPLS)", RFC 5307, DOI 10.17487/RFC5307, October 2008,
<http://www.rfc-editor.org/info/rfc5307>.
[RFC5310] Bhatia, M., Manral, V., Li, T., Atkinson, R., White, R.,
and M. Fanto, "IS-IS Generic Cryptographic
Authentication", RFC 5310, DOI 10.17487/RFC5310, February
2009, <http://www.rfc-editor.org/info/rfc5310>.
[RFC6119] Harrison, J., Berger, J., and M. Bartlett, "IPv6 Traffic
Engineering in IS-IS", RFC 6119, DOI 10.17487/RFC6119,
February 2011, <http://www.rfc-editor.org/info/rfc6119>.
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[RFC7810] Previdi, S., Ed., Giacalone, S., Ward, D., Drake, J., and
Q. Wu, "IS-IS Traffic Engineering (TE) Metric Extensions",
RFC 7810, DOI 10.17487/RFC7810, May 2016,
<http://www.rfc-editor.org/info/rfc7810>.
9.2. Informative References
[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, <http://www.rfc-editor.org/info/rfc7855>.
Authors' Addresses
Les Ginsberg
Cisco Systems
821 Alder Drive
Milpitas, CA 95035
USA
Email: ginsberg@cisco.com
Peter Psenak
Cisco Systems
Apollo Business Center Mlynske nivy 43
Bratislava 821 09
Slovakia
Email: ppsenak@cisco.com
Stefano Previdi
Cisco Systems
Via Del Serafico 200
Rome 0144
Italy
Email: sprevidi@cisco.com
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Wim Henderickx
Nokia
Copernicuslaan 50
Antwerp 2018 94089
Belgium
Email: wim.henderickx@nokia.com
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