OSPF Application-Specific Link AttributesCisco SystemsEurovea Centre, Central 3Pribinova Street 10Bratislava81109Slovakiappsenak@cisco.comCisco Systems821 Alder DriveMilpitasCAUnited States of America95035ginsberg@cisco.comNokiaCopernicuslaan 50AntwerpBelgium2018 94089wim.henderickx@nokia.comApstraUnited States of Americajefftant.ietf@gmail.comJuniper Networks1194 N. Mathilda AveSunnyvaleCalifornia94089United States of Americajdrake@juniper.net
Routing
LSR Working GroupExisting traffic-engineering-related link attribute advertisements
have been defined and are used in RSVP-TE deployments. Since the
original RSVP-TE use case was defined, additional applications (e.g.,
Segment Routing Policy and Loop-Free Alternates) that also make use of the
link attribute advertisements have been defined. 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 document introduces new link attribute advertisements in OSPFv2
and OSPFv3 that address both of these shortcomings.Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by
the Internet Engineering Steering Group (IESG). Further
information on Internet Standards is available in Section 2 of
RFC 7841.
Information about the current status of this document, any
errata, and how to provide feedback on it may be obtained at
.
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Table of Contents
. Introduction
. Requirements Language
. Requirements Discussion
. Existing Advertisement of Link Attributes
. Advertisement of Link Attributes
. OSPFv2 Extended Link Opaque LSA and OSPFv3 E-Router-LSA
. Advertisement of Application-Specific Values
. Reused TE Link Attributes
. Shared Risk Link Group (SRLG)
. Extended Metrics
. Administrative Group
. Traffic Engineering Metric
. Maximum Link Bandwidth
. Considerations for Extended TE Metrics
. Local Interface IPv6 Address Sub-TLV
. Remote Interface IPv6 Address Sub-TLV
. Attribute Advertisements and Enablement
. Deployment Considerations
. Use of Legacy RSVP-TE LSA Advertisements
. Interoperability, Backwards Compatibility, and Migration Concerns
. Multiple Applications: Common Attributes with RSVP-TE
. Multiple Applications: Some Attributes Not Shared with RSVP-TE
. Interoperability with Legacy Routers
. Use of Application-Specific Advertisements for RSVP-TE
. Security Considerations
. IANA Considerations
. OSPFv2
. OSPFv3
. References
. Normative References
. Informative References
Acknowledgments
Contributors
Authors' Addresses
IntroductionAdvertisement of link attributes by the OSPFv2 and OSPFv3 protocols in support of traffic engineering (TE) was
introduced by and , respectively. It has been extended
by , , and . Use
of these extensions has been associated with deployments supporting
Traffic Engineering over Multiprotocol Label Switching (MPLS) in the
presence of the Resource Reservation Protocol (RSVP), more succinctly
referred to as RSVP-TE .For the purposes of this document, an application is a technology
that makes use of link attribute advertisements, examples of which are
listed in .In recent years, new applications have been introduced that have use
cases for many of the link attributes historically used by RSVP-TE.
Such applications include Segment Routing (SR) Policy and
Loop-Free Alternates (LFAs) . This has introduced ambiguity in that if a
deployment includes a mix of RSVP-TE support and SR Policy support, for
example, it is not possible to unambiguously indicate which
advertisements are to be used by RSVP-TE and which advertisements are
to be used by SR Policy. If the topologies are fully congruent, this
may not be an issue, but any incongruence leads to ambiguity.An example of where this ambiguity causes a problem is a network
where RSVP-TE is enabled only on a subset of its links. A link
attribute is advertised for the purpose of another application (e.g.,
SR Policy) for a link that is not enabled for RSVP-TE. As soon as the
router that is an RSVP-TE head end sees the link attribute being
advertised for that link, it assumes RSVP-TE is enabled on that link,
even though it is not. If such an RSVP-TE head-end router tries to set
up an RSVP-TE path via that link, it will result in the path setup
failure.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 that 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 that
is easily extensible for the introduction of new applications and new
use cases.Requirements LanguageThe key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in
BCP 14 when, and only when, they appear in all
capitals, as shown here.Requirements DiscussionAs stated previously, evolution of use cases for link attributes can
be expected to continue. Therefore, any discussion of existing use cases
is limited to requirements that are known at the time of this writing.
However, in order to determine the functionality required beyond what
already exists in OSPF, it is only necessary to discuss use cases that
justify the key points identified in the introduction, which are:
Support for indicating which applications are using the link
attribute advertisements on a link
Support for advertising application-specific values for the same
attribute on a link
discusses use cases and requirements for Segment Routing
(SR). Included among these use cases is SR Policy, which is defined in
. If both RSVP-TE
and SR Policy are deployed in a network, link attribute advertisements
can be used by one or both of these applications. There is no
requirement for the link attributes advertised on a given link used by
SR Policy to be identical to the link attributes advertised on that same
link used by RSVP-TE; thus, there is a clear requirement to indicate
independently which link attribute advertisements are to be used by each
application.As the number of applications that 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.Existing Advertisement of Link AttributesThere are existing advertisements used in support of RSVP-TE. These
advertisements are carried in the OSPFv2 TE Opaque Link State
Advertisement (LSA) and
OSPFv3 Intra-Area-TE-LSA . Additional RSVP-TE link attributes have been
defined by , , and .Extended Link Opaque LSAs as defined in for OSPFv2 and
E-Router-LSAs for OSPFv3 are used to advertise link
attributes that are used by applications other than RSVP-TE or GMPLS .
These LSAs were defined as generic containers for distribution of the extended link attributes.Advertisement of Link AttributesThis section outlines the solution for advertising link attributes
originally defined for RSVP-TE or GMPLS when they are used for other applications.OSPFv2 Extended Link Opaque LSA and OSPFv3 E-Router-LSAThe following are the advantages of Extended Link Opaque LSAs as defined in
for OSPFv2 and E-Router-LSAs for OSPFv3 with respect
to the advertisement of link attributes originally defined for RSVP-TE when used in packet
networks and in GMPLS:
Advertisement of the link attributes does not make the link part of the RSVP-TE topology.
It avoids any conflicts and is fully compatible with and
.
The OSPFv2 TE Opaque LSA and OSPFv3 Intra-Area-TE-LSA remain
truly opaque to OSPFv2 and OSPFv3 as originally defined in and , respectively. Their contents are not inspected
by OSPF, which instead acts as a pure transport.
There is a clear distinction between link attributes used by RSVP-TE and
link attributes used by other OSPFv2 or OSPFv3 applications.
All link attributes that are used by other applications are advertised in the Extended Link Opaque LSA in OSPFv2 or the OSPFv3
E-Router-LSA 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.The Extended Link Opaque LSA and E-Router-LSA
are used to advertise any link attributes used
for non-RSVP-TE applications in OSPFv2 or OSPFv3, respectively, including those that have
been originally defined for RSVP-TE applications (see ).TE link attributes used for RSVP-TE/GMPLS continue to use the OSPFv2 TE Opaque LSA
and OSPFv3 Intra-Area-TE-LSA .The format of the link attribute TLVs that have been defined for
RSVP-TE applications will be kept unchanged even when they are used
for non-RSVP-TE applications. Unique codepoints are allocated for
these link attribute TLVs from the "OSPFv2 Extended Link TLV Sub-TLVs"
registry and from the
"OSPFv3 Extended-LSA Sub-TLVs" registry , as specified in .Advertisement of Application-Specific ValuesTo 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 and OSPFv3 Router-Link TLV
.In addition to advertising the link attributes for standardized
applications, link attributes can be advertised for the purpose of
applications that are not standardized. We call such an
application a "user-defined application" or "UDA". These applications are
not subject to standardization and are outside of the scope
of this specification.The ASLA sub-TLV is an optional sub-TLV of the OSPFv2 Extended Link TLV and
OSPFv3 Router-Link TLV. Multiple ASLA sub-TLVs can be present in a parent
TLV when different applications want to control different link attributes or
when a different value
of the same attribute needs to be advertised by multiple applications. The ASLA sub-TLV
MUST be used for advertisement of the link attributes listed at the end of this section
if these are advertised inside the 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 in octets.
The value MUST be 0, 4, or 8.
If the Standard Application Identifier Bit Mask is not present, the SABM
Length MUST be set to 0.
UDABM Length:
User-Defined Application Identifier Bit Mask Length in octets.
The value MUST be 0, 4, or 8.
If the User-Defined Application Identifier Bit Mask is not present, the
UDABM 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 the "Link Attribute Applications"
registry, which is defined in . Current assignments are repeated here for
informational purposes:
0 1 2 3 4 5 6 7 ...
+-+-+-+-+-+-+-+-+...
|R|S|F| ...
+-+-+-+-+-+-+-+-+...
Bit 0 (R-bit):
RSVP-TE.
Bit 1 (S-bit):
Segment Routing Policy.
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 and sent starting with
bit 0. Undefined bits that are transmitted 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. Bits that are not supported by an
implementation MUST be ignored on receipt.User-Defined Application Identifier Bits have no relationship to
Standard Application Identifier Bits and are not managed by IANA or
any other standards body. It is recommended that these bits be used
starting with bit 0 so as to minimize the number of octets required
to advertise all UDAs. Undefined bits that are transmitted 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. Bits that are not
supported by an implementation MUST be ignored on receipt.If the link attribute advertisement is intended to be only 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 Identifier 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 Identifier Bit Masks part of the attribute advertisement
itself is that the format of any previously defined link attributes
can be kept and reused when advertising them in the ASLA sub-TLV.If the same attribute is advertised in more than one ASLA sub-TLVs with the application
listed in the Application Identifier Bit Masks, the application SHOULD use the first instance of
advertisement and ignore any subsequent advertisements of that attribute.If link attributes are advertised 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. If support for a new application is introduced
on any node in a network in the presence of such advertisements,
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.An application-specific advertisement (Application Identifier Bit
Mask with a matching Application Identifier Bit set) for an attribute
MUST always be preferred over the advertisement of the same attribute
with the zero-length Application Identifier Bit Masks for both
standard applications and user-defined applications on the same link.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.
Documents that define new link attributes MUST state whether the new attributes support
application-specific values and, as such, are advertised in an ASLA sub-TLV. The standard
link attributes that are advertised in ASLA sub-TLVs are:
Shared Risk Link Group
Unidirectional Link Delay
Min/Max Unidirectional Link Delay
Unidirectional Delay Variation
Unidirectional Link Loss
Unidirectional Residual Bandwidth
Unidirectional Available Bandwidth
Unidirectional Utilized Bandwidth
Administrative Group
Extended Administrative Group
TE Metric
Reused TE Link AttributesThis section defines the use case and indicates the codepoints () from the "OSPFv2 Extended Link TLV
Sub-TLVs" registry and "OSPFv3 Extended-LSA Sub-TLVs" registry for some of
the link attributes that have been originally defined for RSVP-TE or
GMPLS.Shared Risk Link Group (SRLG)The SRLG of a link can be used in OSPF-calculated IPFRR (IP Fast Reroute)
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 is used with TLV
type 11. Similarly, for OSPFv3 to advertise the SRLG in the OSPFv3 Router-Link
TLV, TLV type 12 is used.Extended Metrics defines several link bandwidth types.
defines extended link metrics that are based on link bandwidth, delay, and loss
characteristics. All of 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 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 Router-Link TLV inside
the OSPFv3 E-Router-LSA, the same format for the sub-TLVs defined in 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
Administrative Group and 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
and is used with the following TLV types:
19:
Administrative Group
20:
Extended Administrative Group
To advertise the Administrative Group and Extended Administrative Group in the OSPFv3
Router-Link TLV, the same format for the sub-TLVs defined in
and is used with the following TLV types:
20:
Administrative Group
21:
Extended Administrative Group
Traffic Engineering Metric defines the Traffic Engineering Metric.To advertise the Traffic Engineering Metric in the OSPFv2 Extended Link TLV,
the same format for the sub-TLV defined in
is used with TLV type 22. Similarly, for OSPFv3 to advertise the
Traffic Engineering Metric in the OSPFv3 Router-Link TLV, TLV type 22 is used.Maximum Link BandwidthMaximum link bandwidth is an application-independent attribute of the
link that is defined in . 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 Extended Link TLV in the Extended Link Opaque
LSA in OSPFv2 or as a sub-TLV of
the Router-Link TLV in the E-Router-LSA Router-Link TLV in OSPFv3
.To advertise the maximum link bandwidth in the OSPFv2 Extended Link TLV, the same
format for the sub-TLV defined in is used with
TLV type 23.To advertise the maximum link bandwidth in the OSPFv3 Router-Link TLV, the same
format for the sub-TLV defined in is used with
TLV type 23.Considerations for Extended TE Metrics 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. This can be done
either by explicitly specifying the applications in the Application
Identifier Bit Mask or by using a zero-length Application Identifier
Bit Mask.Local Interface IPv6 Address Sub-TLVThe Local Interface IPv6 Address sub-TLV is an application-independent attribute of the
link that is defined in . 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 Router-Link TLV inside the OSPFv3 E-Router-LSA .To advertise the Local Interface IPv6 Address sub-TLV in the OSPFv3 Router-Link TLV,
the same format for the sub-TLV defined in is used with
TLV type 24.Remote Interface IPv6 Address Sub-TLVThe Remote Interface IPv6 Address sub-TLV is an application-independent attribute of the
link that is defined in . 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 Router-Link TLV inside the OSPFv3 E-Router-LSA .To advertise the Remote Interface IPv6 Address sub-TLV in the OSPFv3 Router-Link TLV,
the same format for the sub-TLV defined in is used with
TLV type 25.Attribute Advertisements and EnablementThis document defines extensions to support the advertisement of
application-specific link attributes.There are applications where the application enablement on the link
is relevant; for example, with RSVP-TE, one needs to make sure that RSVP
is enabled on the link before sending an RSVP-TE signaling message over it.There are applications where the enablement of the application on the link is
irrelevant and has nothing to do with the fact that some link attributes are advertised
for the purpose of such application. An example of this is LFA.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 and OSPFv3 Intra-Area-TE-LSA
.In the case of SR Policy, advertisement of application-specific link
attributes does not indicate enablement of SR Policy. The advertisements
are only used to support constraints that may be applied when
specifying an explicit path. SR Policy is implicitly enabled on all links
that are part of the SR-enabled topology independent of
the existence of link attribute advertisements.In the case of LFA, the advertisement of application-specific link
attributes does not indicate enablement of LFA on that link.
Enablement is controlled by local configuration.In the future, if 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 ).
This supports the use of the link attribute by any application. In the presence of
an application where the advertisement of link attributes 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.Deployment ConsiderationsUse of Legacy RSVP-TE LSA AdvertisementsBit identifiers for standard applications are defined in .
All of the identifiers defined in this document are associated with
applications that were already deployed in some networks prior to
the writing of this document. Therefore, such applications have been
deployed using the RSVP-TE LSA advertisements. The standard applications
defined in this document may continue to use 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 SR Policy or LFA, and RSVP-TE is not deployed
anywhere in the network.
The application is SR Policy or LFA, RSVP-TE is deployed in the
network, and both the set of links on which SR Policy and/or LFA
advertisements are required and the attribute values used by SR Policy
and/or LFA on all such links are fully congruent with the links and
attribute values used by RSVP-TE.
Under the conditions defined above, implementations that support the
extensions defined in this document have the choice of using RSVP-TE LSA
advertisements or application-specific advertisements in support of
SR Policy and/or LFA. This will require implementations to provide
controls specifying which types of advertisements are to be sent and processed on receipt for these applications. Further discussion of
the associated issues can be found in .New applications that future documents define to make use of the
advertisements defined in this document MUST NOT make use of RSVP-TE LSA
advertisements. This simplifies deployment of new applications by
eliminating the need to support multiple ways to advertise attributes
for the new applications.Interoperability, Backwards Compatibility, and Migration ConcernsExisting deployments of RSVP-TE, SR Policy, and/or LFA utilize the
legacy advertisements listed in . Routers that 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 in the presence of routers that
do not support these extensions need to be able to interoperate with
the use of legacy advertisements by the legacy routers. The following subsections
discuss interoperability and backwards-compatibility concerns for a number of
deployment scenarios.Multiple Applications: Common Attributes with RSVP-TEIn 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 for RSVP-TE.
Attributes for applications other than RSVP-TE MUST be advertised using
application-specific advertisements. This results in duplicate
advertisements for those attributes.Multiple Applications: Some Attributes Not Shared with RSVP-TEIn 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
for 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 RSVP-TE, this requires duplicate advertisements for those attributes.Interoperability with Legacy RoutersFor the applications defined in this document, routers that do
not support the extensions defined in this document will send and
receive only legacy link attribute advertisements. So long as there
is any legacy router in the network that has any of the
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, SR Policy, 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 to
application-specific advertisements can be achieved via the
following steps:
Send new application-specific advertisements while continuing to
advertise using the legacy advertisement (all advertisements are
then duplicated). Receiving routers continue to use legacy advertisements.
Enable the use of the application-specific advertisements on
all routers.
Keep legacy advertisements if needed for RSVP-TE purposes.
When the migration is complete, it then becomes possible to
advertise incongruent values per application on a given link.Documents defining new applications that make use of the
application-specific advertisements defined in this document MUST
discuss interoperability and backwards-compatibility issues that
could occur in the presence of routers that do not support the new
application.Use of Application-Specific Advertisements for RSVP-TEThe extensions defined in this document support RSVP-TE as one of
the supported applications. It is, however, RECOMMENDED to advertise all
link attributes for RSVP-TE in the existing OSPFv2 TE Opaque LSA
and OSPFv3 Intra-Area-TE-LSA
to maintain backwards compatibility. RSVP-TE can eventually
utilize the application-specific advertisements for newly defined
link attributes that are defined as application specific.Link attributes that are not allowed to be advertised in the ASLA sub-TLV,
such as maximum reservable link bandwidth and unreserved bandwidth, MUST use the
OSPFv2 TE Opaque LSA and OSPFv3 Intra-Area-TE-LSA
and MUST NOT be advertised in the ASLA sub-TLV.Security ConsiderationsExisting security extensions as described in ,
, and 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 ,
, , or
SHOULD be
used.Implementations must ensure that if any of the TLVs and sub-TLVs
defined in this document are malformed, they are detected and do not
facilitate 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.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, which uses various link attributes for its path
computation. This is similar in nature to the impacts associated with,
for example, . As the
advertisements defined in this document limit the scope to specific
applications, the impact of tampering is similarly limited in scope.IANA ConsiderationsThis specification updates two existing registries:
the "OSPFv2 Extended Link TLV Sub-TLVs" registry
the "OSPFv3 Extended-LSA Sub-TLVs" registry
The new values defined in this document have been allocated using the
IETF Review procedure as described in
.OSPFv2The "OSPFv2 Extended Link TLV Sub-TLVs" registry defines sub-TLVs at any level of
nesting for OSPFv2 Extended Link TLVs. IANA has assigned the following
sub-TLV types from the "OSPFv2 Extended Link TLV 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
OSPFv3The "OSPFv3 Extended-LSA Sub-TLVs" registry defines sub-TLVs at any level of nesting for OSPFv3
Extended LSAs. IANA has assigned the following sub-TLV types from the
"OSPFv3 Extended-LSA Sub-TLVs" 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
17:
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
25:
Remote Interface IPv6 Address
ReferencesNormative ReferencesKey words for use in RFCs to Indicate Requirement LevelsIn many standards track documents several words are used to signify the requirements in the specification. These words are often capitalized. This document defines these words as they should be interpreted in IETF documents. This document specifies an Internet Best Current Practices for the Internet Community, and requests discussion and suggestions for improvements.OSPF Version 2This memo documents version 2 of the OSPF protocol. OSPF is a link- state routing protocol. [STANDARDS-TRACK]Traffic Engineering (TE) Extensions to OSPF Version 2This document describes extensions to the OSPF protocol version 2 to support intra-area Traffic Engineering (TE), using Opaque Link State Advertisements.OSPF Extensions in Support of Generalized Multi-Protocol Label Switching (GMPLS)This document specifies encoding of extensions to the OSPF routing protocol in support of Generalized Multi-Protocol Label Switching (GMPLS). [STANDARDS-TRACK]Traffic Engineering Extensions to OSPF Version 3This document describes extensions to OSPFv3 to support intra-area Traffic Engineering (TE). This document extends OSPFv2 TE to handle IPv6 networks. A new TLV and several new sub-TLVs are defined to support IPv6 networks. [STANDARDS-TRACK]OSPF for IPv6This document describes the modifications to OSPF to support version 6 of the Internet Protocol (IPv6). The fundamental mechanisms of OSPF (flooding, Designated Router (DR) election, area support, Short Path First (SPF) calculations, etc.) remain unchanged. However, some changes have been necessary, either due to changes in protocol semantics between IPv4 and IPv6, or simply to handle the increased address size of IPv6. These modifications will necessitate incrementing the protocol version from version 2 to version 3. OSPF for IPv6 is also referred to as OSPF version 3 (OSPFv3).Changes between OSPF for IPv4, OSPF Version 2, and OSPF for IPv6 as described herein include the following. Addressing semantics have been removed from OSPF packets and the basic Link State Advertisements (LSAs). New LSAs have been created to carry IPv6 addresses and prefixes. OSPF now runs on a per-link basis rather than on a per-IP-subnet basis. Flooding scope for LSAs has been generalized. Authentication has been removed from the OSPF protocol and instead relies on IPv6's Authentication Header and Encapsulating Security Payload (ESP).Even with larger IPv6 addresses, most packets in OSPF for IPv6 are almost as compact as those in OSPF for IPv4. Most fields and packet- size limitations present in OSPF for IPv4 have been relaxed. In addition, option handling has been made more flexible.All of OSPF for IPv4's optional capabilities, including demand circuit support and Not-So-Stubby Areas (NSSAs), are also supported in OSPF for IPv6. [STANDARDS-TRACK]Extended Administrative Groups in MPLS Traffic Engineering (MPLS-TE)MPLS Traffic Engineering (MPLS-TE) advertises 32 administrative groups (commonly referred to as "colors" or "link colors") using the Administrative Group sub-TLV. This is defined for OSPFv2 (RFC 3630), OSPFv3 (RFC 5329) and IS-IS (RFC 5305).This document adds a sub-TLV to the IGP TE extensions, "Extended Administrative Group". This sub-TLV provides for additional administrative groups (link colors) beyond the current limit of 32.OSPF Traffic Engineering (TE) Metric ExtensionsIn certain networks, such as, but not limited to, financial information networks (e.g., stock market data providers), network performance information (e.g., link propagation delay) is becoming critical to data path selection.This document describes common extensions to RFC 3630 "Traffic Engineering (TE) Extensions to OSPF Version 2" and RFC 5329 "Traffic Engineering Extensions to OSPF Version 3" to enable network performance information to be distributed in a scalable fashion. The information distributed using OSPF TE Metric Extensions can then be used to make path selection decisions based on network performance.Note that this document only covers the mechanisms by which network performance information is distributed. The mechanisms for measuring network performance information or using that information, once distributed, are outside the scope of this document.OSPFv2 Prefix/Link Attribute AdvertisementOSPFv2 requires functional extension beyond what can readily be done with the fixed-format Link State Advertisements (LSAs) as described in RFC 2328. This document defines OSPFv2 Opaque LSAs based on Type-Length-Value (TLV) tuples that can be used to associate additional attributes with prefixes or links. Depending on the application, these prefixes and links may or may not be advertised in the fixed-format LSAs. The OSPFv2 Opaque LSAs are optional and fully backward compatible.Ambiguity of Uppercase vs Lowercase in RFC 2119 Key WordsRFC 2119 specifies common key words that may be used in protocol specifications. This document aims to reduce the ambiguity by clarifying that only UPPERCASE usage of the key words have the defined special meanings.OSPFv3 Link State Advertisement (LSA) ExtensibilityOSPFv3 requires functional extension beyond what can readily be done with the fixed-format Link State Advertisement (LSA) as described in RFC 5340. Without LSA extension, attributes associated with OSPFv3 links and advertised IPv6 prefixes must be advertised in separate LSAs and correlated to the fixed-format LSAs. This document extends the LSA format by encoding the existing OSPFv3 LSA information in Type-Length-Value (TLV) tuples and allowing advertisement of additional information with additional TLVs. Backward-compatibility mechanisms are also described.This document updates RFC 5340, "OSPF for IPv6", and RFC 5838, "Support of Address Families in OSPFv3", by providing TLV-based encodings for the base OSPFv3 unicast support and OSPFv3 address family support.IS-IS Application-Specific Link AttributesInformative ReferencesRSVP-TE: Extensions to RSVP for LSP TunnelsThis document describes the use of RSVP (Resource Reservation Protocol), including all the necessary extensions, to establish label-switched paths (LSPs) in MPLS (Multi-Protocol Label Switching). Since the flow along an LSP is completely identified by the label applied at the ingress node of the path, these paths may be treated as tunnels. A key application of LSP tunnels is traffic engineering with MPLS as specified in RFC 2702. [STANDARDS-TRACK]Authentication/Confidentiality for OSPFv3This document describes means and mechanisms to provide authentication/confidentiality to OSPFv3 using an IPv6 Authentication Header/Encapsulating Security Payload (AH/ESP) extension header. [STANDARDS-TRACK]Basic Specification for IP Fast Reroute: Loop-Free AlternatesThis document describes the use of loop-free alternates to provide local protection for unicast traffic in pure IP and MPLS/LDP networks in the event of a single failure, whether link, node, or shared risk link group (SRLG). The goal of this technology is to reduce the packet loss that happens while routers converge after a topology change due to a failure. Rapid failure repair is achieved through use of precalculated backup next-hops that are loop-free and safe to use until the distributed network convergence process completes. This simple approach does not require any support from other routers. The extent to which this goal can be met by this specification is dependent on the topology of the network. [STANDARDS-TRACK]OSPFv2 HMAC-SHA Cryptographic AuthenticationThis document describes how the National Institute of Standards and Technology (NIST) Secure Hash Standard family of algorithms can be used with OSPF version 2's built-in, cryptographic authentication mechanism. This updates, but does not supercede, the cryptographic authentication mechanism specified in RFC 2328. [STANDARDS-TRACK]IP Fast Reroute FrameworkThis document provides a framework for the development of IP fast- reroute mechanisms that provide protection against link or router failure by invoking locally determined repair paths. Unlike MPLS fast-reroute, the mechanisms are applicable to a network employing conventional IP routing and forwarding. This document is not an Internet Standards Track specification; it is published for informational purposes.Supporting Authentication Trailer for OSPFv3Currently, OSPF for IPv6 (OSPFv3) uses IPsec as the only mechanism for authenticating protocol packets. This behavior is different from authentication mechanisms present in other routing protocols (OSPFv2, Intermediate System to Intermediate System (IS-IS), RIP, and Routing Information Protocol Next Generation (RIPng)). In some environments, it has been found that IPsec is difficult to configure and maintain and thus cannot be used. This document defines an alternative mechanism to authenticate OSPFv3 protocol packets so that OSPFv3 does not depend only upon IPsec for authentication.The OSPFv3 Authentication Trailer was originally defined in RFC 6506. This document obsoletes RFC 6506 by providing a revised definition, including clarifications and refinements of the procedures.Security Extension for OSPFv2 When Using Manual Key ManagementThe current OSPFv2 cryptographic authentication mechanism as defined in RFCs 2328 and 5709 is vulnerable to both inter-session and intra- session replay attacks when using manual keying. Additionally, the existing cryptographic authentication mechanism does not cover the IP header. This omission can be exploited to carry out various types of attacks.This document defines changes to the authentication sequence number mechanism that will protect OSPFv2 from both inter-session and intra- session replay attacks when using manual keys for securing OSPFv2 protocol packets. Additionally, we also describe some changes in the cryptographic hash computation that will eliminate attacks resulting from OSPFv2 not protecting the IP header.Source Packet Routing in Networking (SPRING) Problem Statement and RequirementsThe ability for a node to specify a forwarding path, other than the normal shortest path, that a particular packet will traverse, benefits a number of network functions. Source-based routing mechanisms have previously been specified for network protocols but have not seen widespread adoption. In this context, the term "source" means "the point at which the explicit route is imposed"; therefore, it is not limited to the originator of the packet (i.e., the node imposing the explicit route may be the ingress node of an operator's network).This document outlines various use cases, with their requirements, that need to be taken into account by the Source Packet Routing in Networking (SPRING) architecture for unicast traffic. Multicast use cases and requirements are out of scope for this document.Guidelines for Writing an IANA Considerations Section in RFCsMany protocols make use of points of extensibility that use constants to identify various protocol parameters. To ensure that the values in these fields do not have conflicting uses and to promote interoperability, their allocations are often coordinated by a central record keeper. For IETF protocols, that role is filled by the Internet Assigned Numbers Authority (IANA).To make assignments in a given registry prudently, guidance describing the conditions under which new values should be assigned, as well as when and how modifications to existing values can be made, is needed. This document defines a framework for the documentation of these guidelines by specification authors, in order to assure that the provided guidance for the IANA Considerations is clear and addresses the various issues that are likely in the operation of a registry.This is the third edition of this document; it obsoletes RFC 5226.Segment Routing Policy ArchitectureCisco SystemsCisco SystemsBell CanadaGoogle, Inc.Microsoft Segment Routing (SR) allows a headend node to steer a packet flow
along any path. Intermediate per-flow states are eliminated thanks
to source routing. The headend node steers a flow into an SR Policy.
The header of a packet steered in an SR Policy is augmented with an
ordered list of segments associated with that SR Policy. This
document details the concepts of SR Policy and steering into an SR
Policy.
Work in ProgressAcknowledgmentsThanks to for his review and comments.Thanks to for his detailed review and comments.ContributorsThe following people contributed to the content
of this document and should be considered as coauthors:Cisco Systems301 Midenhall WayCaryNC27513United States of Americaacee@cisco.comCisco Systems, Inc.Indiaketant@cisco.comRtBrick Inc.Austriahannes@rtbrick.comAuthors' AddressesCisco SystemsEurovea Centre, Central 3Pribinova Street 10Bratislava81109Slovakiappsenak@cisco.comCisco Systems821 Alder DriveMilpitasCAUnited States of America95035ginsberg@cisco.comNokiaCopernicuslaan 50AntwerpBelgium2018 94089wim.henderickx@nokia.comApstraUnited States of Americajefftant.ietf@gmail.comJuniper Networks1194 N. Mathilda AveSunnyvaleCalifornia94089United States of Americajdrake@juniper.net