Networking Working Group S. Previdi, Ed.
Internet-Draft Cisco Systems, Inc.
Intended status: Standards Track S. Giacalone
Expires: April 11, 2013 Thomson Reuters
D. Ward
Cisco Systems, Inc.
J. Drake
A. Atlas
Juniper Networks
C. Filsfils
Cisco Systems, Inc.
October 08, 2012
IS-IS Traffic Engineering (TE) Metric Extensions
draft-previdi-isis-te-metric-extensions-02
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
This Internet-Draft is submitted in full conformance with the
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provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on April 11, 2013.
Copyright Notice
Copyright (c) 2012 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 . . . . . . . . . . . . . . . . 4
3. Interface and Neighbor Addresses . . . . . . . . . . . . . . . 6
4. Sub TLV Details . . . . . . . . . . . . . . . . . . . . . . . 6
4.1. Unidirectional Link Delay Sub-TLV . . . . . . . . . . . . 6
4.2. Unidirectional Delay Variation Sub-TLV . . . . . . . . . . 7
4.3. Unidirectional Link Loss Sub-TLV . . . . . . . . . . . . . 8
4.4. Unidirectional Residual Bandwidth Sub-TLV . . . . . . . . 8
4.5. Unidirectional Available Bandwidth Sub-TLV . . . . . . . . 9
5. Announcement Thresholds and Filters . . . . . . . . . . . . . 10
6. Announcement Suppression . . . . . . . . . . . . . . . . . . . 11
7. Network Stability and Announcement Periodicity . . . . . . . . 11
8. Compatibility . . . . . . . . . . . . . . . . . . . . . . . . 11
9. Security Considerations . . . . . . . . . . . . . . . . . . . 11
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11
11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 11
12. References . . . . . . . . . . . . . . . . . . . . . . . . . . 12
12.1. Normative References . . . . . . . . . . . . . . . . . . . 12
12.2. Informative References . . . . . . . . . . . . . . . . . . 12
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 13
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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 IS-IS TE Metric Extensions 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 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 IS-IS TE Metric Extensions can be
used to setup, fail over, and fail back data paths using protocols
such as RSVP-TE [RFC3209].
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.
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:
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Type Value
TBD1 Unidirectional Link Delay
TBD2 Unidirectional Delay Variation
TBD3 Unidirectional Packet Loss
TBD4 Unidirectional Residual Bandwidth Sub TLV
TBD5 Unidirectional Available Bandwidth Sub TLV
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 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:
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.
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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
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Delay |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
This sub-TLV has a type of TBD1.
The length is 4.
Where:
"A" represents the Anomalous (A) bit. The A bit is set when the
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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.
The "Reserved" field is reserved for future use. It MUST be set to 0
when sent and MUST be ignored when received.
"Delay Value" is a 24-bit field carries the average link delay 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.
4.2. 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|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Delay Variation |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
This sub-TLV has a type of TBD2.
The length is 4.
Where:
"A" 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.
The "Reserved" field is reserved for future use. It MUST be set to 0
when sent and MUST be ignored when received.
"Delay Variation" is a 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
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least that value and may be larger.
4.3. 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:
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Link Loss |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
This sub-TLV has a type of TBD3.
The length is 4.
Where:
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" field is reserved for future use. It MUST be set to 0
when sent and MUST be ignored when received.
"Link Loss" is a 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.
4.4. Unidirectional Residual Bandwidth Sub-TLV
This TLV advertises the residual bandwidth between two directly
connected IS-IS neighbors. The residual bandwidth advertised by this
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sub-TLV MUST be the residual bandwidth from the system originating
the sub-TLV 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |A| RESERVED | Residual |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Bandwidth |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
This sub-TLV has a type of TBD4.
The length is 5.
Where:
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.
"Residual Bandwidth" is the residual bandwidth in IEEE floating point
format in units of bytes per second. The link may be a single link,
forwarding adjacency [RFC4206], or bundled link. For a link or
forwarding adjacency, residual bandwidth is defined to be Maximum
Link Bandwidth [RFC5305] 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.
Note that although it may seem possible to calculate Residual
Bandwidth using the existing sub-TLVs in [RFC5305], this is not a
consistently reliable approach and hence the Residual Bandwidth sub-
TLV has been added here. For example, because the Maximum Reservable
Bandwidth [RFC5305] can be larger than the capacity of the link,
using it as part of an algorithm to determine the value of the
Maximum Link Bandwidth [RFC5305]minus the bandwidth currently
allocated to RSVP-TE Label Switched Paths cannot be considered
reliably accurate.
4.5. Unidirectional Available Bandwidth Sub-TLV
This TLV advertises the available bandwidth between two directly
connected IS-IS neighbors. The available bandwidth advertised in
this sub-TLV MUST be the available bandwidth from the originating
system to its neighbor. 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 | Available |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Bandwidth |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
This sub-TLV has a type of TBD5.
The length is 5.
Where:
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.
"Available Bandwidth" is a field that 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 4.4) 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.
5. Announcement Thresholds and Filters
The values advertised in all sub-TLVs MUST be controlled using an
exponential filter (i.e. a rolling average) with a configurable
measurement interval and filter coefficient.
Implementations are expected to provide separately configurable
advertisement thresholds. All thresholds MUST be configurable on a
per sub-TLV basis.
The announcement of all sub-TLVs that do not include the A bit SHOULD
be controlled by variation thresholds that govern when they are sent.
Sub-TLVs that include the A bit are governed by several thresholds.
Firstly, a threshold SHOULD be implemented to govern the announcement
of sub-TLVs that advertise a change in performance, but not an SLA
violation (i.e. when the A bit is not set). Secondly,
implementations MUST provide configurable thresholds that govern the
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announcement of sub-TLVs with the A bit set (for the indication of a
performance violation). Thirdly, implementations SHOULD provide
reuse thresholds. These thresholds govern sub-TLV re-announcement
with the A bit cleared to permit fail back.
6. Announcement Suppression
When link performance average values change, but fall under the
threshold that would cause the announcement of a sub-TLV with the A
bit set, implementations MAY suppress or throttle sub-TLV
announcements. All suppression features and thresholds SHOULD be
configurable.
7. Network Stability and Announcement Periodicity
To mitigate concerns about stability, all values (except residual
bandwidth) MUST be calculated as rolling averages where the averaging
period MUST be a configurable period of time, rather than
instantaneous measurements.
Announcements MUST also be able to be throttled using configurable
inter-update throttle timers. The minimum announcement periodicity
is 1 announcement per second.
8. Compatibility
As per [RFC5305], unrecognized Sub-TLVs should be silently ignored
9. Security Considerations
This document does not introduce security issues beyond those
discussed in [RFC3630] and [RFC5329].
10. 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
document.
11. Acknowledgements
The authors would like to recognize Ayman Soliman and Les Ginsberg
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for their contributions.
12. References
12.1. 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,
"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.
12.2. Informative References
[I-D.ietf-alto-protocol]
Alimi, R., Penno, R., and Y. Yang, "ALTO Protocol",
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draft-ietf-alto-protocol-13 (work in progress),
September 2012.
[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
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
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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
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