Networking Working Group S. Previdi, Ed.
Internet-Draft Cisco Systems, Inc.
Intended status: Standards Track S. Giacalone
Expires: April 13, 2014 Thomson Reuters
D. Ward
Cisco Systems, Inc.
J. Drake
A. Atlas
Juniper Networks
C. Filsfils
Cisco Systems, Inc.
Q. Wu
Huawei
October 10, 2013
IS-IS Traffic Engineering (TE) Metric Extensions
draft-ietf-isis-te-metric-extensions-01
Abstract
In certain networks, such as, but not limited to, financial
information networks (e.g. stock market data providers), network
performance criteria (e.g. latency) are becoming as critical to data
path selection as other metrics.
This document describes extensions to IS-IS TE [RFC5305] such that
network performance information can be distributed and collected in a
scalable fashion. The information distributed using ISIS TE Metric
Extensions can then be used to make path selection decisions based on
network performance.
Note that this document only covers the mechanisms with which network
performance information is distributed. The mechanisms for measuring
network performance or acting on that information, once distributed,
are outside the scope of 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].
In this document, these words will appear with that interpretation
only when in ALL CAPS. Lower case uses of these words are not to be
interpreted as carrying RFC-2119 significance.
Status of this Memo
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This Internet-Draft is submitted in full conformance with the
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Internet-Drafts are draft documents valid for a maximum of six months
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This Internet-Draft will expire on April 13, 2014.
Copyright Notice
Copyright (c) 2013 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
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the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. TE Metric Extensions to IS-IS . . . . . . . . . . . . . . . . 5
3. Interface and Neighbor Addresses . . . . . . . . . . . . . . . 6
4. Sub TLV Details . . . . . . . . . . . . . . . . . . . . . . . 6
4.1. Unidirectional Link Delay Sub-TLV . . . . . . . . . . . . 7
4.2. Min/Max Unidirectional Link Delay Sub-TLV . . . . . . . . 7
4.3. Unidirectional Delay Variation Sub-TLV . . . . . . . . . . 9
4.4. Unidirectional Link Loss Sub-TLV . . . . . . . . . . . . . 9
4.5. Unidirectional Residual Bandwidth Sub-TLV . . . . . . . . 10
4.6. Unidirectional Available Bandwidth Sub-TLV . . . . . . . . 11
4.7. Unidirectional Utilized Bandwidth Sub-TLV . . . . . . . . 12
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 . . . . . . . . . . . . . . . . . . . . . 15
13. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 16
14. References . . . . . . . . . . . . . . . . . . . . . . . . . . 16
14.1. Normative References . . . . . . . . . . . . . . . . . . . 16
14.2. Informative References . . . . . . . . . . . . . . . . . . 17
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 17
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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. latency) is becoming as critical to
data path selection as other metrics.
In these networks, extremely large amounts of money rest on the
ability to access market data in "real time" and to predictably make
trades faster than the competition. 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 performance data (such as
latency) in a cost-effective and scalable way.
This document describes extensions to IS-IS Extended Reachability TLV
defined in [RFC5305] (hereafter called "IS-IS TE Metric Extensions"),
that can be used to distribute network performance information (such
as link delay, delay variation, packet loss, residual bandwidth, and
available bandwidth).
The data distributed by the TE Metric Extensions proposed in this
document is meant to be used as part of the operation of the routing
protocol (e.g. by replacing cost with latency or considering
bandwidth as well as cost), by enhancing Constrained-SPF (CSPF), or
for other uses such as supplementing the data used by an ALTO server
[I-D.ietf-alto-protocol]. With respect to CSPF, the data distributed
by ISIS TE Metric Extensions can be used to setup, fail over, and
fail back data paths using protocols such as RSVP-TE [RFC3209];
[I-D.atlas-mpls-te-express-path] describes some methods for using
this information to compute Label Switched Paths (LSPs) at the LSP
ingress.
Note that the mechanisms described in this document only disseminate
performance information. The methods for initially gathering that
performance information, such as [RFC6375], or acting on it once it
is distributed are outside the scope of this document. Example
mechanisms to measure latency, delay variation, and loss in an MPLS
network are given in [RFC6374]. While this document does not specify
how the performance information should be obtained, the measurement
of delay SHOULD NOT vary significantly based upon the offered traffic
load. Thus, queuing delays SHOULD NOT be included in the delay
measurement. For links, such as Forwarding Adjacencies, care must be
taken that measurement of the associated delay avoids significant
queuing delay; that could be accomplished in a variety of ways,
including either by measuring with a traffic class that experiences
minimal queuing or by summing the measured link delays of the
components of the link's path.
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2. TE Metric Extensions to IS-IS
This document proposes new IS-IS TE sub-TLVs that can be announced in
ISIS Extended Reachability TLV (TLV-22) to distribute network
performance information. The extensions in this document build on
the ones provided in IS-IS TE [RFC5305] and GMPLS [RFC4203].
IS-IS Extended Reachability TLV 22 (defined in [RFC5305]), Inter-AS
reachability information TLV 141 (defined in [RFC5316]) and MT-ISN
TLV 222 (defined in [RFC5120]) have nested sub-TLVs which permit the
TLVs to be readily extended. This document proposes several
additional sub-TLVs:
Type Value
-----------------------------------------------
TBA Unidirectional Link Delay
TBA Low/High Unidirectional Link Delay
TBA Unidirectional Delay Variation
TBA Unidirectional Packet Loss
TBA Unidirectional Residual Bandwidth
TBA Unidirectional Available Bandwidth
TBA Unidirectional Bandwidth Utilization
As can be seen in the list above, the sub-TLVs described in this
document carry different types of network performance information.
The new 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 fail 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:
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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) Determine 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.
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 to do
(including nothing).
Note that when a sub-TLV does not include the A bit, that sub-TLV
cannot be used for failover purposes. The A bit was intentionally
omitted from some sub-TLVs to help mitigate oscillations. See
Section 5 for more information.
Consistent with existing IS-IS TE specifications [RFC5305], the
bandwidth advertisements defined in this draft MUST be encoded as
IEEE floating point values. The delay and delay variation
advertisements defined in this draft MUST be encoded as integer
values. Delay values MUST be quantified in units of microseconds,
packet loss MUST be quantified as a percentage of packets sent, and
bandwidth MUST be sent as 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.
3. Interface and Neighbor Addresses
The use of TE Metric Extensions SubTLVs is not confined to the TE
context. In other words, IS-IS TE Metric Extensions SubTLVs defined
in this document can also be used for computing paths in the absence
of a TE subsystem.
However, as for the TE case, Interface Address and Neighbor Address
SubTLVs (IPv4 or IPv6) MUST be present. The encoding is defined in
[RFC5305] for IPv4 and in [RFC6119] for IPv6.
4. Sub TLV Details
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4.1. Unidirectional Link Delay Sub-TLV
This sub-TLV advertises the average link delay between two directly
connected IS-IS neighbors. The delay advertised by this sub-TLV MUST
be the delay from the local neighbor to the remote one (i.e. the
forward path latency). 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|A| RESERVED | Delay |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
where:
Figure 1
Type: TBA
Length: 4
A-bit. The A-bit 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.
RESERVED. This field is reserved for future use. It MUST be set to
0 when sent and MUST be ignored when received.
Delay. This 24-bit field carries the average link delay over a
configurable interval in micro-seconds, 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 may be larger. If there is no value
to send (unmeasured and not statically specified), then the sub-TLV
should not be sent or be withdrawn.
4.2. Min/Max Unidirectional Link Delay Sub-TLV
This sub-TLV advertises the minimum and maximum delay values between
two directly connected IS-IS neighbors. The delay advertised by this
sub-TLV MUST be the delay from the local neighbor to the remote one
(i.e. the forward path latency). The format of this sub-TLV is shown
in the following diagram:
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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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|A| RESERVED | Low Delay |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| RESERVED | High Delay |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
where:
Figure 2
Type: TBA
Length: 8
A-bit. The A-bit 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.
RESERVED. This field is reserved for future use. It MUST be set to
0 when sent and MUST be ignored when received.
Low Delay. This 24-bit field carries minimum measured link delay
value (in microseconds) over a configurable interval, encoded as an
integer value.
High 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 a static (non
dynamic) offset value (in microseconds) to be added to the measured
delay value, to facilitate the communication of operator specific
delay constraints.
It is possible for the high delay and low delay to be the same value.
When the delay value (Low or High) is set to maximum value 16,777,215
(16.777215 sec), then the delay is at least that value and 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 IS-IS neighbors. The delay variation advertised
by this sub-TLV MUST be the delay from the local neighbor to the
remote one (i.e. the forward path latency). 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|A| RESERVED | Delay Variation |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
where:
Figure 3
Type: TBA.
Lenght: 4.
A-bit. The A-bit 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.
RESERVED. This field is reserved for future use. It MUST be set to
0 when sent and MUST be ignored when received.
Delay Variation. This 24-bit field carries the average link delay
variation over a configurable interval in micro-seconds, 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 may be larger.
4.4. Unidirectional Link Loss Sub-TLV
This sub-TLV advertises the loss (as a packet percentage) between two
directly connected IS-IS neighbors. The link loss advertised by this
sub-TLV MUST be the packet loss from the local neighbor to the remote
one (i.e. the forward path loss). The format of this sub-TLV is
shown in the following diagram:
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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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|A| RESERVED | Link Loss |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
This sub-TLV has a type of TBD3.
The length is 4.
where:
Type: TBA.
Length: 4.
A-bit. The A-bit 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.
A-bit. The A-bit 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.
RESERVED. This field is reserved for future use. It MUST be set to
0 when sent and MUST be ignored when received.
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. When set to a value of all 1s (2^24 -
1), the link packet loss has not been measured.
4.5. Unidirectional Residual Bandwidth Sub-TLV
This TLV advertises the residual bandwidth between two directly
connected IS-IS neighbors. The residual bandwidth advertised by this
sub-TLV MUST be the residual bandwidth from the system originating
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the LSA to its neighbor.
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 |A| RESERVED |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Residual Bandwidth |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
where:
Type: TBA.
Length: 4.
A-bit. The A-bit 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.
RESERVED. This field is reserved for future use. It MUST be set to
0 when sent and MUST be ignored when received.
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 QoS classes.
Unreserved Bandwidth [RFC3630], on the other hand, is subtracted from
the Maximum Reservable Bandwidth (the bandwidth that can
theoretically be reserved) [RFC3630] and provides per-QoS-class
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 IS-IS neighbors. The available bandwidth advertised by
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this sub-TLV MUST be the available bandwidth from the system
originating this Sub-TLV. 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |A| RESERVED |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Available Bandwidth |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
where:
Figure 4
Type: TBA.
Length: 4.
A-bit. The A-bit 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.
RESERVED. This field is reserved for future use. It MUST be set to
0 when sent and MUST be ignored when received.
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
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
minus the measured bandwidth used for the actual forwarding of non-
RSVP-TE Label Switched Paths 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 IS-IS neighbors. The bandwidth utilization
advertised by this sub-TLV MUST be the bandwidth from the system
originating this Sub-TLV. The format of this Sub-TLV is shown in the
following diagram:
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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 |A| RESERVED |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Bandwidth Utilization |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
where:
Figure 5
Type: TBA.
Length: 4.
A-bit. The A-bit 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.
RESERVED. This field is reserved for future use. It MUST be set to
0 when sent and MUST be ignored when received.
Bandwidth Utilization. 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 represent the actual
utilization of the link (i.e.: as measured in the router). For a
bundled link, bandwidth utilization is defined to be the sum of the
component link bandwidth utilization.
5. Announcement Thresholds and Filters
The values advertised in all sub-TLVs (except Low/High 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.
Low or High 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 low and high
value representative of the interval with compensation for outliers.
The measurement interval, any filter coefficients, and any
advertisement intervals MUST be configurable per sub-TLV.
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In addition to the measurement intervals governing re-advertisement,
implementations SHOULD provide per sub-TLV configurable accelerated
advertisement thresholds, such that:
1. If the measured parameter falls outside a configured upper
bound for all but the low delay metric (or lower bound for
low-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.
4. For sub-TLVs which include an A-bit (except low/high
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
readvertisement 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 readvertisement and/or
lengthen the period within which they are refreshed.
Only the accelerated advertisement threshold mechanism may shorten
the re-advertisement interval. All suppression and re-advertisement
interval backoff timer features SHOULD be configurable.
7. Network Stability and Announcement Periodicity
Section 5 and Section 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
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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.
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 each sub-TLV based on configuration.
9. Static Metric Override
Implementations SHOULD permit the static configuration and/or manual
override of dynamic measurements data on a per sub-TLV, per metric
basis in order to simplify migrations and to mitigate scenarios where
measurements are not possible across an entire network.
10. Compatibility
As per [RFC5305], unrecognized Sub-TLVs should be silently ignored
11. Security Considerations
This document does not introduce security issues beyond those
discussed in [RFC3630] and [RFC5329].
12. IANA Considerations
IANA maintains the registry for the sub-TLVs. IS-IS TE Metric
Extensions will require one new type code per sub-TLV defined in this
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document.
13. Acknowledgements
The authors would like to recognize Ayman Soliman, Nabil Bitar, David
McDysan, Les Ginsberg, Edward Crabbe, Don Fedyk and Hannes Gredler
for their contributions.
The authors also recognize Curtis Villamizar for significant comments
and direct content collaboration.
14. References
14.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[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.
[RFC3630] Katz, D., Kompella, K., and D. Yeung, "Traffic Engineering
(TE) Extensions to OSPF Version 2", RFC 3630,
September 2003.
[RFC4203] Kompella, K. and Y. Rekhter, "OSPF Extensions in Support
of Generalized Multi-Protocol Label Switching (GMPLS)",
RFC 4203, October 2005.
[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.
[RFC5120] Przygienda, T., Shen, N., and N. Sheth, "M-ISIS: Multi
Topology (MT) Routing in Intermediate System to
Intermediate Systems (IS-ISs)", RFC 5120, February 2008.
[RFC5305] Li, T. and H. Smit, "IS-IS Extensions for Traffic
Engineering", RFC 5305, October 2008.
[RFC5316] Chen, M., Zhang, R., and X. Duan, "ISIS Extensions in
Support of Inter-Autonomous System (AS) MPLS and GMPLS
Traffic Engineering", RFC 5316, December 2008.
[RFC5329] Ishiguro, K., Manral, V., Davey, A., and A. Lindem,
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"Traffic Engineering Extensions to OSPF Version 3",
RFC 5329, September 2008.
[RFC6119] Harrison, J., Berger, J., and M. Bartlett, "IPv6 Traffic
Engineering in IS-IS", RFC 6119, February 2011.
[RFC6374] Frost, D. and S. Bryant, "Packet Loss and Delay
Measurement for MPLS Networks", RFC 6374, September 2011.
14.2. Informative References
[I-D.atlas-mpls-te-express-path]
Atlas, A., Drake, J., Giacalone, S., Ward, D., Previdi,
S., and C. Filsfils, "Performance-based Path Selection for
Explicitly Routed LSPs using TE Metric Extensions",
draft-atlas-mpls-te-express-path-04 (work in progress),
September 2013.
[I-D.ietf-alto-protocol]
Alimi, R., Penno, R., and Y. Yang, "ALTO Protocol",
draft-ietf-alto-protocol-20 (work in progress),
October 2013.
[RFC6375] Frost, D. and S. Bryant, "A Packet Loss and Delay
Measurement Profile for MPLS-Based Transport Networks",
RFC 6375, September 2011.
Authors' Addresses
Stefano Previdi (editor)
Cisco Systems, Inc.
Via Del Serafico 200
Rome 00191
IT
Email: sprevidi@cisco.com
Spencer Giacalone
Thomson Reuters
195 Broadway
New York, NY 10007
USA
Email: Spencer.giacalone@thomsonreuters.com
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Dave Ward
Cisco Systems, Inc.
3700 Cisco Way
SAN JOSE, CA 95134
US
Email: wardd@cisco.com
John Drake
Juniper Networks
1194 N. Mathilda Ave.
Sunnyvale, CA 94089
USA
Email: jdrake@juniper.net
Alia Atlas
Juniper Networks
1194 N. Mathilda Ave.
Sunnyvale, CA 94089
USA
Email: akatlas@juniper.net
Clarence Filsfils
Cisco Systems, Inc.
Brussels
Belgium
Email: cfilsfil@cisco.com
Qin Wu
Huawei
101 Software Avenue, Yuhua District
Nanjing, Jiangsu 210012
China
Email: sunseawq@huawei.com
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