Internet DRAFT - draft-giacalone-ospf-te-express-path
draft-giacalone-ospf-te-express-path
Network Working Group S. Giacalone
Internet Draft Thomson Reuters
Intended status: Proposed Standard
Expires: March 2012 D. Ward
Juniper Networks
J. Drake
Juniper Networks
A. Atlas
Juniper Networks
S. Previdi
Cisco Systems
September 21, 2011
OSPF Traffic Engineering (TE) Express Path
draft-giacalone-ospf-te-express-path-02.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 OSPF TE [RFC3630] such that
network performance information can be distributed and collected in a
scalable fashion. The information distributed using OSPF 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.
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
1. Introduction...................................................3
2. Conventions used in this document..............................4
3. Express Path 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
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4.1.3. A bit................................................7
4.1.4. Reserved.............................................7
4.1.5. Delay Value..........................................7
4.2. Unidirectional Delay Variation Sub-TLV....................7
4.2.1. Type.................................................7
4.2.2. Length...............................................7
4.2.3. Reserved.............................................8
4.2.4. Delay Variation......................................8
4.3. Unidirectional Link Loss Sub-TLV..........................8
4.3.1. Type.................................................8
4.3.2. Length...............................................8
4.3.3. A bit................................................8
4.3.4. Reserved.............................................9
4.3.5. Link Loss............................................9
4.4. Unidirectional Residual Bandwidth Sub-TLV.................9
4.4.1. Type.................................................9
4.4.2. Length..............................................10
4.4.3. Residual Bandwidth..................................10
4.5. Unidirectional Available Bandwidth Sub-TLV...............10
4.4.4. Type................................................10
4.4.5. Length..............................................11
4.4.6. Available Bandwidth.................................11
5. Announcement Thresholds and Filters...........................11
6. Announcement Suppression......................................11
7. Network Stability and Announcement Periodicity................12
8. Compatibility.................................................12
9. Security Considerations.......................................12
10. IANA Considerations..........................................12
11. References...................................................12
11.1. Normative References....................................12
11.2. Informative References..................................13
12. Acknowledgments..............................................13
13. Author's Addresses...........................................14
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
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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 OSPF TE (hereafter called "OSPF
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 OSPF TE OSPF 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 CSPF, or for other uses such as supplementing the
data used by an Alto server [Alto]. With respect to CSPF, the data
distributed by OSPF 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 OSPF TE
This document proposes new OSPF TE sub-TLVs that can be announced in
OSPF TE LSAs to distribute network performance information. The
extensions in this document build on the ones provided in OSPF TE
[RFC3630] and GMPLS [RFC4203].
OSPF TE LSAs [RFC3630] are opaque LSAs [RFC5250] with area flooding
scope. Each TLV has one or more nested sub-TLVs which permit the TE
LSA to be readily extended. There are two main types of OSPF TE LSA;
the Router Address or Link TE LSA. Like the extensions in GMPLS
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(RFC4203), this document proposes several additional sub-TLVs for
the Link TE LSA:
Type Length Value
TBD1 4 Unidirectional Link Delay
TBD2 4 Unidirectional Delay Variation
TBD3 4 Unidirectional Packet Loss
TBD4 4 Unidirectional Residual Bandwidth Sub TLV
TBD5 4 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).
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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
7. 1. for more information.
Consistent with existing OSPF TE specifications (RFC3630), 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.
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 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TBD1 | 4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|A| RESERVED | Delay |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
4.1.1. Type
This sub-TLV has a type of TBD1.
4.1.2. Length
The length is 4.
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4.1.3. 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 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 OSPF 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TBD2 | 4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| RESERVED | Delay Variation |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
4.2.1. Type
This sub-TLV has a type of TBD2.
4.2.2. Length
The length is 4.
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4.2.3. Reserved
This field is reserved for future use. It MUST be set to 0 when sent
and MUST be ignored when received.
4.2.4. 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.
4.3. 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 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TBD3 | 4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|A| RESERVED | Link Loss |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
4.3.1. Type
This sub-TLV has a type of TBD3
4.3.2. Length
The length is 4
4.3.3. 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
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its configured reuse threshold. If the A bit is clear, the sub-TLV
represents steady state link performance.
4.3.4. Reserved
This field is reserved for future use. It MUST be set to 0 when sent
and MUST be ignored when received.
4.3.5. 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.
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 4.4.3.
between two directly connected OSPF neighbors. The residual bandwidth
advertised by this sub-TLV MUST be the residual bandwidth from the
system originating the LSA 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TBD4 | 4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Residual Bandwidth |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
4.4.1. Type
This sub-TLV has a type of TBD4.
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4.4.2. Length
The length is 4.
4.4.3. 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.
Note that although it may seem possible to calculate Residual
Bandwidth using the existing sub-TLVs in RFC 3630, 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 [RFC3630] can be larger than the capacity of the link,
using it as part of an algorithm to determine the value of the
Maximum Bandwidth [RFC3630] minus the bandwidth currently allocated
to RSVP-TE LSPs cannot be considered reliably accurate.
4.5. Unidirectional Available Bandwidth Sub-TLV
This TLV advertises the available bandwidth (defined in section
4.4.6. ) between two directly connected OSPF neighbors. The available
bandwidth advertised by this sub-TLV MUST be the available bandwidth
from the system originating the LSA 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TBD5 | 4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Available Bandwidth |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
4.4.4. Type
This sub-TLV has a type of TBD5.
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4.4.5. Length
The length is 4.
4.4.6. 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 4.4. )
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.
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
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
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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 (RFC3630), unrecognized 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. OSPF 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.
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[RFC3630] Katz, D., Kompella, K., Yeung, D., "Traffic
Engineering (TE) Extensions to OSPF Version 2", RFC 3630,
September 2003.
11.2. Informative References
[RFC2328] Moy, J, "OSPF Version 2", RFC 2328, April 1998
[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.
[RFC5250] Berger, L., Bryskin I., Zinin, A., Coltun, R., "The OSPF
Opaque LSA Option", RFC 5250, July 2008.
[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 for his
contributions.
This document was prepared using 2-Word-v2.0.template.dot.
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13. Author's Addresses
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
Stefano Previdi
Cisco Systems
Via Del Serafico 200
00142 Rome
Italy
Email: sprevidi@cisco.com
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