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Internet Engineering Task Force (IETF) S. Giacalone
Request for Comments: 7471 Unaffiliated
Category: Standards Track D. Ward
ISSN: 2070-1721 Cisco Systems
J. Drake
A. Atlas
Juniper Networks
S. Previdi
Cisco Systems
March 2015
OSPF Traffic Engineering (TE) Metric Extensions
Abstract
In 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.
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 5741.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc7471.
Giacalone, et al. Standards Track [Page 1]
RFC 7471 OSPF TE Metric Extensions March 2015
Copyright Notice
Copyright (c) 2015 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
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction ....................................................3
2. Conventions Used in This Document ...............................4
3. TE Metric Extensions to OSPF TE .................................4
4. Sub-TLV Details .................................................6
4.1. Unidirectional Link Delay Sub-TLV ..........................6
4.1.1. Type ................................................6
4.1.2. Length ..............................................6
4.1.3. Anomalous (A) Bit ...................................7
4.1.4. Reserved ............................................7
4.1.5. Delay Value .........................................7
4.2. Min/Max Unidirectional Link Delay Sub-TLV ..................7
4.2.1. Type ................................................7
4.2.2. Length ..............................................7
4.2.3. Anomalous (A) Bit ...................................8
4.2.4. Reserved ............................................8
4.2.5. Min Delay ...........................................8
4.2.6. Reserved ............................................8
4.2.7. Max Delay ...........................................8
4.3. Unidirectional Delay Variation Sub-TLV .....................9
4.3.1. Type ................................................9
4.3.2. Length ..............................................9
4.3.3. Reserved ............................................9
4.3.4. Delay Variation .....................................9
4.4. Unidirectional Link Loss Sub-TLV ...........................9
4.4.1. Type ...............................................10
4.4.2. Length .............................................10
4.4.3. Anomalous (A) Bit ..................................10
4.4.4. Reserved ...........................................10
4.4.5. Link Loss ..........................................10
Giacalone, et al. Standards Track [Page 2]
RFC 7471 OSPF TE Metric Extensions March 2015
4.5. Unidirectional Residual Bandwidth Sub-TLV .................10
4.5.1. Type ...............................................11
4.5.2. Length .............................................11
4.5.3. Residual Bandwidth .................................11
4.6. Unidirectional Available Bandwidth Sub-TLV ................11
4.6.1. Type ...............................................12
4.6.2. Length .............................................12
4.6.3. Available Bandwidth ................................12
4.7. Unidirectional Utilized Bandwidth Sub-TLV .................12
4.7.1. Type ...............................................12
4.7.2. Length .............................................13
4.7.3. Utilized Bandwidth .................................13
5. Announcement Thresholds and Filters ............................13
6. Announcement Suppression .......................................14
7. Network Stability and Announcement Periodicity .................14
8. Enabling and Disabling Sub-TLVs ................................15
9. Static Metric Override .........................................15
10. Compatibility .................................................15
11. Security Considerations .......................................15
12. IANA Considerations ...........................................16
13. References ....................................................16
13.1. Normative References .....................................16
13.2. Informative References ...................................17
Acknowledgments ...................................................18
Authors' Addresses ................................................19
1. Introduction
In 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 as
critical to data path selection as other metrics.
Because of this, using metrics such as hop count or cost as routing
metrics is becoming only tangentially important. Rather, it would be
beneficial to be able to make path selection decisions based on
network performance information (such as link propagation delay) in a
cost-effective and scalable way.
This document describes extensions to OSPFv2 and OSPFv3 TE (hereafter
called "OSPF TE Metric Extensions"), that can be used to distribute
network performance information (viz link propagation delay, delay
variation, link loss, residual bandwidth, available bandwidth, and
utilized bandwidth).
The data distributed by OSPF TE Metric Extensions is meant to be used
as part of the operation of the routing protocol (e.g., by replacing
cost with link propagation delay or considering bandwidth as well as
Giacalone, et al. Standards Track [Page 3]
RFC 7471 OSPF TE Metric Extensions March 2015
cost), by enhancing Constrained Shortest Path First (CSPF), or for
use by a PCE [RFC4655] or an Application-Layer Traffic Optimization
(ALTO) server [RFC7285]. With respect to CSPF, the data distributed
by OSPF TE Metric Extensions can be used to set up, fail over, and
fail back data paths using protocols such as RSVP-TE [RFC3209].
Note that the mechanisms described in this document only distribute
network performance information. The methods for measuring that
information or acting on it once it is distributed are outside the
scope of this document. A method for measuring loss and delay in an
MPLS network is described in [RFC6374].
While this document does not specify the method for measuring network
performance information, any measurement of link propagation delay
SHOULD NOT vary significantly based upon the offered traffic load
and, hence, SHOULD NOT include queuing delays. For a forwarding
adjacency (FA) [RFC4206], care must be taken that measurement of the
link propagation delay avoids significant queuing delay; this can be
accomplished in a variety of ways, e.g., measuring with a traffic
class that experiences minimal queuing or summing the measured link
propagation delay of the links on the FA's path.
2. Conventions Used in This Document
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].
In this document, these words should convey that interpretation only
when in ALL CAPS. Lowercase uses of these words are not to be
interpreted as carrying this significance.
3. TE Metric Extensions to OSPF TE
This document defines new OSPF TE sub-TLVs that are used to
distribute network performance information. The extensions in this
document build on the ones provided in OSPFv2 TE [RFC3630] and OSPFv3
TE [RFC5329].
OSPFv2 TE Link State Advertisements (LSAs) [RFC3630] are opaque LSAs
[RFC5250] with area flooding scope while OSPFv3 Intra-Area-TE-LSAs
have their own LSA type, also with area flooding scope; both consist
of a single TLV with one or more nested sub-TLVs. The Link TLV is
common to both and describes the characteristics of a link between
OSPF neighbors.
Giacalone, et al. Standards Track [Page 4]
RFC 7471 OSPF TE Metric Extensions March 2015
This document defines several additional sub-TLVs for the Link TLV:
Type Length Value
27 4 Unidirectional Link Delay
28 8 Min/Max Unidirectional Link Delay
29 4 Unidirectional Delay Variation
30 4 Unidirectional Link Loss
31 4 Unidirectional Residual Bandwidth
32 4 Unidirectional Available Bandwidth
33 4 Unidirectional Utilized Bandwidth
As can be seen in the list above, the sub-TLVs described in this
document carry different types of network performance information.
Many (but not all) of the sub-TLVs include a bit called the Anomalous
(or A) bit. When the A bit is clear (or when the sub-TLV does not
include an A bit), the sub-TLV describes steady state link
performance. This information could conceivably be used to construct
a steady state performance topology for initial tunnel path
computation, or to verify alternative failover paths.
When network performance violates configurable link-local thresholds
a sub-TLV with the A bit set is advertised. These sub-TLVs could be
used by the receiving node to determine whether to move traffic to a
backup path or whether to calculate an entirely new path. From an
MPLS perspective, the intent of the A bit is to permit LSP ingress
nodes to:
A) Determine whether the link referenced in the sub-TLV affects any
of the LSPs for which it is ingress. If there are, then:
B) The node determines whether those LSPs still meet end-to-end
performance objectives. If not, then:
C) The node could then conceivably move affected traffic to a pre-
established protection LSP or establish a new LSP and place the
traffic in it.
Giacalone, et al. Standards Track [Page 5]
RFC 7471 OSPF TE Metric Extensions March 2015
If link performance then improves beyond a configurable minimum value
(reuse threshold), that sub-TLV can be re-advertised with the
Anomalous bit cleared. In this case, a receiving node can
conceivably do whatever re-optimization (or failback) it wishes
(including nothing).
The A bit was intentionally omitted from some sub-TLVs to help
mitigate oscillations. See Section 7.1 for more information.
Link delay, delay variation, and link loss MUST be encoded as
integers. Consistent with existing OSPF TE specifications [RFC3630],
residual, available, and utilized bandwidth MUST be encoded in IEEE
single precision floating point [IEEE754]. Link delay and delay
variation MUST be in units of microseconds, link loss MUST be a
percentage, and bandwidth MUST be in units of bytes per second. All
values (except residual bandwidth) MUST be calculated as rolling
averages where the averaging period MUST be a configurable period of
time. See Section 5 for more information.
4. Sub-TLV Details
4.1. Unidirectional Link Delay Sub-TLV
This sub-TLV advertises the average link delay between two directly
connected OSPF neighbors. The delay advertised by this sub-TLV MUST
be the delay from the advertising node to its neighbor (i.e., the
forward path delay). The format of this sub-TLV is shown in the
following diagram:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 27 | 4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|A| RESERVED | Delay |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
4.1.1. Type
This sub-TLV has a type of 27.
4.1.2. Length
The length is 4.
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4.1.3. Anomalous (A) Bit
This field represents the Anomalous (A) bit. The A bit is set when
the measured value of this parameter exceeds its configured maximum
threshold. The A bit is cleared when the measured value falls below
its configured reuse threshold. If the A bit is clear, the sub-TLV
represents steady state link performance.
4.1.4. Reserved
This field is reserved for future use. It MUST be set to 0 when sent
and MUST be ignored when received.
4.1.5. Delay Value
This 24-bit field carries the average link delay over a configurable
interval in microseconds, encoded as an integer value. When set to
the maximum value 16,777,215 (16.777215 sec), then the delay is at
least that value, and it may be larger.
4.2. Min/Max Unidirectional Link Delay Sub-TLV
This sub-TLV advertises the minimum and maximum delay values between
two directly connected OSPF neighbors. The delay advertised by this
sub-TLV MUST be the delay from the advertising node to its neighbor
(i.e., the forward path delay). The format of this sub-TLV is shown
in the following diagram:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 28 | 8 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|A| RESERVED | Min Delay |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| RESERVED | Max Delay |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
4.2.1. Type
This sub-TLV has a type of 28.
4.2.2. Length
The length is 8.
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4.2.3. Anomalous (A) Bit
This field represents the Anomalous (A) bit. The A bit is set when
one or more measured values exceed a configured maximum threshold.
The A bit is cleared when the measured value falls below its
configured reuse threshold. If the A bit is clear, the sub-TLV
represents steady state link performance.
4.2.4. Reserved
This field is reserved for future use. It MUST be set to 0 when sent
and MUST be ignored when received.
4.2.5. Min Delay
This 24-bit field carries minimum measured link delay value (in
microseconds) over a configurable interval, encoded as an integer
value.
Implementations MAY also permit the configuration of an offset value
(in microseconds) to be added to the measured delay value to
advertise operator specific delay constraints.
When set to the maximum value 16,777,215 (16.777215 sec), then the
delay is at least that value, and it may be larger.
4.2.6. Reserved
This field is reserved for future use. It MUST be set to 0 when sent
and MUST be ignored when received.
4.2.7. Max Delay
This 24-bit field carries the maximum measured link delay value (in
microseconds) over a configurable interval, encoded as an integer
value.
Implementations may also permit the configuration of an offset value
(in microseconds) to be added to the measured delay value to
advertise operator specific delay constraints.
It is possible for min delay and max delay to be the same value.
When the delay value is set to the maximum value 16,777,215
(16.777215 sec), then the delay is at least that value, and it may be
larger.
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4.3. Unidirectional Delay Variation Sub-TLV
This sub-TLV advertises the average link delay variation between two
directly connected OSPF neighbors. The delay variation advertised by
this sub-TLV MUST be the delay from the advertising node to its
neighbor (i.e., the forward path delay variation). The format of
this sub-TLV is shown in the following diagram:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 29 | 4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| RESERVED | Delay Variation |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
4.3.1. Type
This sub-TLV has a type of 29.
4.3.2. Length
The length is 4.
4.3.3. Reserved
This field is reserved for future use. It MUST be set to 0 when sent
and MUST be ignored when received.
4.3.4. Delay Variation
This 24-bit field carries the average link delay variation over a
configurable interval in microseconds, encoded as an integer value.
When set to 0, it has not been measured. When set to the maximum
value 16,777,215 (16.777215 sec), then the delay is at least that
value, and it may be larger.
4.4. Unidirectional Link Loss Sub-TLV
This sub-TLV advertises the loss (as a packet percentage) between two
directly connected OSPF neighbors. The link loss advertised by this
sub-TLV MUST be the packet loss from the advertising node to its
neighbor (i.e., the forward path loss). The format of this sub-TLV
is shown in the following diagram:
Giacalone, et al. Standards Track [Page 9]
RFC 7471 OSPF TE Metric Extensions March 2015
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 30 | 4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|A| RESERVED | Link Loss |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
4.4.1. Type
This sub-TLV has a type of 30
4.4.2. Length
The length is 4.
4.4.3. Anomalous (A) Bit
This field represents the Anomalous (A) bit. The A bit is set when
the measured value of this parameter exceeds its configured maximum
threshold. The A bit is cleared when the measured value falls below
its configured reuse threshold. If the A bit is clear, the sub-TLV
represents steady state link performance.
4.4.4. Reserved
This field is reserved for future use. It MUST be set to 0 when sent
and MUST be ignored when received.
4.4.5. Link Loss
This 24-bit field carries link packet loss as a percentage of the
total traffic sent over a configurable interval. The basic unit is
0.000003%, where (2^24 - 2) is 50.331642%. This value is the highest
packet loss percentage that can be expressed (the assumption being
that precision is more important on high speed links than the ability
to advertise loss rates greater than this, and that high speed links
with over 50% loss are unusable). Therefore, measured values that
are larger than the field maximum SHOULD be encoded as the maximum
value.
4.5. Unidirectional Residual Bandwidth Sub-TLV
This sub-TLV advertises the residual bandwidth between two directly
connected OSPF neighbors. The residual bandwidth advertised by this
sub-TLV MUST be the residual bandwidth from the advertising node to
its neighbor.
Giacalone, et al. Standards Track [Page 10]
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The format of this sub-TLV is shown in the following diagram:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 31 | 4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Residual Bandwidth |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
4.5.1. Type
This sub-TLV has a type of 31.
4.5.2. Length
The length is 4.
4.5.3. Residual Bandwidth
This field carries the residual bandwidth on a link, forwarding
adjacency [RFC4206], or bundled link in IEEE floating point format
with units of bytes per second. For a link or forwarding adjacency,
residual bandwidth is defined to be Maximum Bandwidth [RFC3630] minus
the bandwidth currently allocated to RSVP-TE LSPs. For a bundled
link, residual bandwidth is defined to be the sum of the component
link residual bandwidths.
The calculation of Residual Bandwidth is different than that of
Unreserved Bandwidth [RFC3630]. Residual Bandwidth subtracts tunnel
reservations from Maximum Bandwidth (i.e., the link capacity)
[RFC3630] and provides an aggregated remainder across priorities.
Unreserved Bandwidth, on the other hand, is subtracted from the
Maximum Reservable Bandwidth (the bandwidth that can theoretically be
reserved) and provides per priority remainders. Residual Bandwidth
and Unreserved Bandwidth [RFC3630] can be used concurrently, and each
has a separate use case (e.g., the former can be used for
applications like Weighted ECMP while the latter can be used for call
admission control).
4.6. Unidirectional Available Bandwidth Sub-TLV
This sub-TLV advertises the available bandwidth between two directly
connected OSPF neighbors. The available bandwidth advertised by this
sub-TLV MUST be the available bandwidth from the advertising node to
its neighbor. The format of this sub-TLV is shown in the following
diagram:
Giacalone, et al. Standards Track [Page 11]
RFC 7471 OSPF TE Metric Extensions March 2015
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 32 | 4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Available Bandwidth |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
4.6.1. Type
This sub-TLV has a type of 32.
4.6.2. Length
The length is 4.
4.6.3. Available Bandwidth
This field carries the available bandwidth on a link, forwarding
adjacency, or bundled link in IEEE floating point format with units
of bytes per second. For a link or forwarding adjacency, available
bandwidth is defined to be residual bandwidth (see Section 4.5) minus
the measured bandwidth used for the actual forwarding of non-RSVP-TE
LSP packets. For a bundled link, available bandwidth is defined to
be the sum of the component link available bandwidths.
4.7. Unidirectional Utilized Bandwidth Sub-TLV
This Sub-TLV advertises the bandwidth utilization between two
directly connected OSPF neighbors. The bandwidth utilization
advertised by this sub-TLV MUST be the bandwidth from the advertising
node to its neighbor. The format of this Sub-TLV is shown in the
following diagram:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 33 | 4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Utilized Bandwidth |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
4.7.1. Type
This sub-TLV has a type of 33.
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4.7.2. Length
The length is 4.
4.7.3. Utilized Bandwidth
This field carries the bandwidth utilization on a link, forwarding
adjacency, or bundled link in IEEE floating-point format with units
of bytes per second. For a link or forwarding adjacency, bandwidth
utilization represents the actual utilization of the link (i.e., as
measured by the advertising node). For a bundled link, bandwidth
utilization is defined to be the sum of the component link bandwidth
utilizations.
5. Announcement Thresholds and Filters
The values advertised in all sub-TLVs (except min/max delay and
residual bandwidth) MUST represent an average over a period or be
obtained by a filter that is reasonably representative of an average.
For example, a rolling average is one such filter.
Min and max delay MAY be the lowest and/or highest measured value
over a measurement interval or MAY make use of a filter, or other
technique, to obtain a reasonable representation of a min and max
value representative of the interval with compensation for outliers.
The measurement interval, any filter coefficients, and any
advertisement intervals MUST be configurable for each sub-TLV.
In addition to the measurement intervals governing re-advertisement,
implementations SHOULD provide for each sub-TLV configurable
accelerated advertisement thresholds, such that:
1. If the measured parameter falls outside a configured upper bound
for all but the min delay metric (or lower bound for min delay
metric only) and the advertised sub-TLV is not already outside
that bound, or
2. If the difference between the last advertised value and current
measured value exceed a configured threshold, then
3. The advertisement is made immediately.
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4. For sub-TLVs, which include an A bit (except min/max delay), an
additional threshold SHOULD be included corresponding to the
threshold for which the performance is considered anomalous (and
sub-TLVs with the A bit are sent). The A bit is cleared when the
sub-TLV's performance has been below (or re-crosses) this
threshold for an advertisement interval(s) to permit fail back.
To prevent oscillations, only the high threshold or the low threshold
(but not both) may be used to trigger any given sub-TLV that supports
both.
Additionally, once outside of the bounds of the threshold, any re-
advertisement of a measurement within the bounds would remain
governed solely by the measurement interval for that sub-TLV.
6. Announcement Suppression
When link performance values change by small amounts that fall under
thresholds that would cause the announcement of a sub-TLV,
implementations SHOULD suppress sub-TLV re-advertisement and/or
lengthen the period within which they are refreshed.
Only the accelerated advertisement threshold mechanism described in
Section 5 may shorten the re-advertisement interval.
All suppression and re-advertisement interval back-off timer features
SHOULD be configurable.
7. Network Stability and Announcement Periodicity
Sections 5 and 6 provide configurable mechanisms to bound the number
of re-advertisements. Instability might occur in very large networks
if measurement intervals are set low enough to overwhelm the
processing of flooded information at some of the routers in the
topology. Therefore, care should be taken in setting these values.
Additionally, the default measurement interval for all sub-TLVs
should be 30 seconds.
Announcements must also be able to be throttled using configurable
inter-update throttle timers. The minimum announcement periodicity
is 1 announcement per second. The default value should be set to 120
seconds.
Implementations should not permit the inter-update timer to be lower
than the measurement interval.
Giacalone, et al. Standards Track [Page 14]
RFC 7471 OSPF TE Metric Extensions March 2015
Furthermore, it is recommended that any underlying performance
measurement mechanisms not include any significant buffer delay, any
significant buffer induced delay variation, or any significant loss
due to buffer overflow or due to active queue management.
8. Enabling and Disabling Sub-TLVs
Implementations MUST make it possible to individually enable or
disable the advertisement of each sub-TLV.
9. Static Metric Override
Implementations SHOULD permit the static configuration and/or manual
override of dynamic measurements for each sub-TLV in order to
simplify migration and to mitigate scenarios where dynamic
measurements are not possible.
10. Compatibility
As per [RFC3630], an unrecognized TLV should be silently ignored.
That is, it should not be processed but it should be included in LSAs
sent to OSPF neighbors.
11. Security Considerations
This document does not introduce security issues beyond those
discussed in [RFC3630]. OSPFv2 HMAC-SHA [RFC5709] provides
additional protection for OSPFv2. OSPFv3 IPsec [RFC4552] and OSPFv3
Authentication Trailer [RFC7166] provide additional protection for
OSPFv3.
OSPF Keying and Authentication for Routing Protocols (KARP) [RFC6863]
provides an analysis of OSPFv2 and OSPFv3 routing security, and
OSPFv2 Security Extensions [OSPFSEC] provides extensions designed to
address the identified gaps in OSPFv2.
Giacalone, et al. Standards Track [Page 15]
RFC 7471 OSPF TE Metric Extensions March 2015
12. IANA Considerations
IANA maintains the registry for the Link TLV sub-TLVs. For OSPF TE
Metric Extensions, one new type code for each sub-TLV defined in this
document has been registered, as follows:
Value Sub-TLV
27 Unidirectional Link Delay
28 Min/Max Unidirectional Link Delay
29 Unidirectional Delay Variation
30 Unidirectional Link Loss
31 Unidirectional Residual Bandwidth
32 Unidirectional Available Bandwidth
33 Unidirectional Utilized Bandwidth
13. References
13.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[RFC3630] Katz, D., Kompella, K., and D. Yeung, "Traffic Engineering
(TE) Extensions to OSPF Version 2", RFC 3630, September
2003, <http://www.rfc-editor.org/info/rfc3630>.
[RFC5329] Ishiguro, K., Manral, V., Davey, A., and A. Lindem, Ed.,
"Traffic Engineering Extensions to OSPF Version 3", RFC
5329, September 2008,
<http://www.rfc-editor.org/info/rfc5329>.
[IEEE754] Institute of Electrical and Electronics Engineers,
"Standard for Floating-Point Arithmetic", IEEE Standard
754, August 2008.
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RFC 7471 OSPF TE Metric Extensions March 2015
13.2. Informative References
[RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V.,
and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP
Tunnels", RFC 3209, December 2001,
<http://www.rfc-editor.org/info/rfc3209>.
[RFC4206] Kompella, K. and Y. Rekhter, "Label Switched Paths (LSP)
Hierarchy with Generalized Multi-Protocol Label Switching
(GMPLS) Traffic Engineering (TE)", RFC 4206, October 2005,
<http://www.rfc-editor.org/info/rfc4206>.
[RFC4552] Gupta, M. and N. Melam, "Authentication/Confidentiality
for OSPFv3", RFC 4552, June 2006,
<http://www.rfc-editor.org/info/rfc4552>.
[RFC4655] Farrel, A., Vasseur, J.-P., and J. Ash, "A Path
Computation Element (PCE)-Based Architecture", RFC 4655,
August 2006, <http://www.rfc-editor.org/info/rfc4655>.
[RFC5250] Berger, L., Bryskin, I., Zinin, A., and R. Coltun, "The
OSPF Opaque LSA Option", RFC 5250, July 2008,
<http://www.rfc-editor.org/info/rfc5250>.
[RFC5709] Bhatia, M., Manral, V., Fanto, M., White, R., Barnes, M.,
Li, T., and R. Atkinson, "OSPFv2 HMAC-SHA Cryptographic
Authentication", RFC 5709, October 2009,
<http://www.rfc-editor.org/info/rfc5709>.
[RFC6374] Frost, D. and S. Bryant, "Packet Loss and Delay
Measurement for MPLS Networks", RFC 6374, September 2011,
<http://www.rfc-editor.org/info/rfc6374>.
[RFC6863] Hartman, S. and D. Zhang, "Analysis of OSPF Security
According to the Keying and Authentication for Routing
Protocols (KARP) Design Guide", RFC 6863, March 2013,
<http://www.rfc-editor.org/info/rfc6863>.
[RFC7166] Bhatia, M., Manral, V., and A. Lindem, "Supporting
Authentication Trailer for OSPFv3", RFC 7166, March 2014,
<http://www.rfc-editor.org/info/rfc7166>.
[RFC7285] Alimi, R., Ed., Penno, R., Ed., Yang, Y., Ed., Kiesel, S.,
Previdi, S., Roome, W., Shalunov, S., and R. Woundy,
"Application-Layer Traffic Optimization (ALTO) Protocol",
RFC 7285, September 2014,
<http://www.rfc-editor.org/info/rfc7285>.
Giacalone, et al. Standards Track [Page 17]
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[OSPFSEC] Bhatia, M., Hartman, S., Zhang, D., and A. Lindem, Ed.,
"Security Extension for OSPFv2 when Using Manual Key
Management", Work in Progress, draft-ietf-ospf-security-
extension-manual-keying, November 2014.
Acknowledgments
The authors would like to recognize Nabil Bitar, Edward Crabbe, Don
Fedyk, Acee Lindem, David McDysan, and Ayman Soliman for their
contributions to this document.
The authors would also like to acknowledge Curtis Villamizar for his
significant comments and direct content collaboration.
Giacalone, et al. Standards Track [Page 18]
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Authors' Addresses
Spencer Giacalone
Unaffiliated
EMail: spencer.giacalone@gmail.com
Dave Ward
Cisco Systems
170 West Tasman Dr.
San Jose, CA 95134
United States
EMail: dward@cisco.com
John Drake
Juniper Networks
1194 N. Mathilda Ave.
Sunnyvale, CA 94089
United States
EMail: jdrake@juniper.net
Alia Atlas
Juniper Networks
1194 N. Mathilda Ave.
Sunnyvale, CA 94089
United States
EMail: akatlas@juniper.net
Stefano Previdi
Cisco Systems
Via Del Serafico 200
00142 Rome
Italy
EMail: sprevidi@cisco.com
Giacalone, et al. Standards Track [Page 19]