IS-IS Traffic Engineering (TE) Metric Extensions
draft-previdi-isis-te-metric-extensions-00
The information below is for an old version of the document.
| Document | Type |
This is an older version of an Internet-Draft whose latest revision state is "Replaced".
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|---|---|---|---|
| Authors | Stefano Previdi , Spencer Giacalone , David Ward , John Drake , Alia Atlas , Clarence Filsfils | ||
| Last updated | 2011-10-10 | ||
| Replaced by | draft-ietf-isis-te-metric-extensions, RFC 7810 | ||
| RFC stream | (None) | ||
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| Stream | Stream state | (No stream defined) | |
| Consensus boilerplate | Unknown | ||
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| Send notices to | (None) |
draft-previdi-isis-te-metric-extensions-00
Network Working Group S. Previdi
Internet Draft Cisco Systems
Intended status: Proposed Standard
Expires: April 2012 S. Giacalone
Thomson Reuters
D. Ward
Juniper Networks
J. Drake
Juniper Networks
A. Atlas
Juniper Networks
C.Filsfils
Cisco Systems
October 10, 2011
IS-IS Traffic Engineering (TE) Metric Extensions
draft-previdi-isis-te-metric-extensions-00.txt
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 Express
Path 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.
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Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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Table of Contents
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1. Introduction...................................................3
2. Conventions used in this document..............................4
3. Express Path Extensions to IS-IS TE............................4
4. Sub TLV Details................................................6
4.1. Unidirectional Link Delay Sub-TLV.........................6
4.2. Unidirectional Delay Variation Sub-TLV....................6
4.3. Unidirectional Link Loss Sub-TLV..........................7
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. References...................................................12
11.1. Normative References....................................12
11.2. Informative References..................................12
12. Acknowledgments..............................................12
13. Author's Addresses...........................................12
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
[RFC5305](hereafter called "IS-IS TE Express Path"), 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 Express Path 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
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CSPF, or for other uses such as supplementing the data used by an
Alto server [Alto]. With respect to CSPF, the data distributed by IS-
IS TE Express Path 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 [Frost], or acting on it once it is
distributed are outside the scope of this document.
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 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.
3. Express Path Extensions to IS-IS TE
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 (TLV-22) defined in [RFC5305] has
nested sub-TLVs which permit the ISIS Reachability TLV to be readily
extended. This document proposes several additional sub-TLVs:
Type Length Value
TBD1 6 Unidirectional Link Delay
TBD2 6 Unidirectional Delay Variation
TBD3 6 Unidirectional Packet Loss
TBD4 6 Unidirectional Residual Bandwidth Sub TLV
TBD5 6 Unidirectional Available Bandwidth Sub TLV
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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.
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.
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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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| RESERVED | Delay |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
This sub-TLV has a type of TBD1.
The length is 6.
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 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
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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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| RESERVED | Delay Variation |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
This sub-TLV has a type of TBD2.
The length is 6.
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
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:
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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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| RESERVED | Link Loss |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
This sub-TLV has a type of TBD3.
The length is 6.
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 (defined in section Error!
Reference source not found.between two directly connected IS-IS
neighbors. The residual bandwidth advertised by this 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:
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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 | RESERVED |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Residual Bandwidth |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
This sub-TLV has a type of TBD4.
The length is 6.
"Reserved" field is reserved for future use. It MUST be set to 0 when
sent and MUST be ignored when received.
"Residual Bandwidth" is a 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
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 RFC 5305, 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 (defined in section
Error! Reference source not found.between two directly connected IS-
IS neighbors. The available bandwidth advertised by this sub-TLV MUST
be the available bandwidth from the system originating the Sub-TLV to
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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 | RESERVED |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Available Bandwidth |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
This sub-TLV has a type of TBD5.
The length is 6.
Where:
"Reserved" field is reserved for future use. It MUST be set to 0 when
sent and MUST be ignored when received.
"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-TLV that include the A bit are governed by several thresholds.
Firstly, a threshold SHOULD be implemented to govern the announcement
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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 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 TLVs should be silently ignored
9. Security Considerations
This document does not introduce security issues beyond those
discussed in [RFC3630] and [RFC5329].
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10. IANA Considerations
IANA maintains the registry for the sub-TLVs. IS-IS TE Express Path
will require one new type code per sub-TLV defined in this document.
11. References
11.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC5305] Li, T., Smit, H., "IS-IS Extensions for Traffic
Engineering", RFC 3630, September 2003.
11.2. Informative References
[RFC3031] Rosen, E., Viswanathan, A., Callon, R., "Multiprotocol
Label Switching Architecture", January 2001
[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.
[Frost] D. Frost, S. Bryant"A Packet Loss and Delay Measurement
Profile for MPLS-based Transport Networks"
[Alto] R. Alimi R. Penno Y. Yang, "ALTO Protocol"
12. Acknowledgments
The authors would like to recognize Ayman Soliman and Les Ginsberg
for their contributions.
This document was prepared using 2-Word-v2.0.template.dot.
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13. Author's Addresses
Stefano Previdi
Cisco Systems
Via Del Serafico 200
00142 Rome
Italy
Email: sprevidi@cisco.com
Spencer Giacalone
Thomson Reuters
195 Broadway
New York NY 10007, USA
Email: Spencer.giacalone@thomsonreuters.com
Dave Ward
Juniper Networks
1194 N. Mathilda Ave.
Sunnyvale, CA 94089, USA
Email: dward@juniper.net
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
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Cisco Systems
Brussels, Belgium
Email: cfilsfil@cisco.com
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