Internet DRAFT - draft-ali-pce-additional-of-and-metric
draft-ali-pce-additional-of-and-metric
CCAMP Working Group Zafar Ali
Internet Draft George Swallow
Intended status: Standard Track Clarence Filsfils
Expires: April 14, 2013 Siva Sivabalan
Stefano Previdi
Cisco Systems
Kenji Kumaki
KDDI Corporation
October 15, 2012
Additional Objective Functions and Metric Types in Path
Computation Element Communication Protocol (PCEP)
draft-ali-pce-additional-of-and-metric-00.txt
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Abstract
Network performance criteria such as latency and latency variation
are becoming critical to data path selection, especially for
networks used by financial institutions. This draft defines
additional objective functions and metrics types related to latency
and latency variation in Path Computation Element Communication
Protocol (PCEP).
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].
Table of Contents
Copyright Notice..................................................1
1. Introduction...................................................3
2. PCEP extensions................................................3
2.1. New Metric Object Types................................3
2.1.1. P2P Latency Metric................................4
2.1.2. P2P Latency Variation Metric......................4
2.1.3. P2MP Latency Metric...............................4
2.1.4. P2MP Latency Variation Metric.....................5
2.2. Handling of New Metric Object Types....................5
2.3. New Objective Functions................................5
2.3.1. Minimum Latency Path Objective Function...........6
2.3.2. Minimum Latency Variation Path Objective Function.6
2.4. Handling of New Objective Functions....................6
3. Security Considerations........................................6
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4. IANA Considerations............................................6
5. References.....................................................7
5.1. Normative References...................................7
5.2. Informative References.................................7
1. Introduction
As noted in [OSPF-TE-METRIC] and [ISIS-TE-METRIC], in certain
networks such as financial information networks (e.g. stock
market data providers), performance criteria (e.g. latency,
latency variation) are becoming critical to data path selection
along with other metrics. Such networks may require selection of
a path that minimizes end-to-end latency and/or end-to-end
latency variation. Or a path may need to be found that optimizes
some other metric, but is subjected to a latency and/or latency
variation bound(s).
The METRIC object defined in [RFC5440] allows a PCC to specify a
bounded acceptable path cost and/or optimization metric. While
[RFC5440], [RFC5541] and [RFC6006] define various Metric Types,
these RFCs do not address latency and latency variation metrics.
This document extends [RFC 5540] with four new Metric Types
namely Point-to-Point (P2P) latency metric, P2P latency variation
metric, Point-to-Multipoint (P2MP) latency metric and P2MP
latency variation metric.
[RFC5541] defines a framework to extend the PCEP to allow a PCE
to indicate the set of objective functions it supports. [RFC5541]
also define procedure so that a PCC can indicate in a path
computation request the required objective function, and a PCE
can report in a path computation reply the objective function
that was used for path computation. While [RFC5541] and [RFC6006]
define various objective functions, these documents do not define
objective functions for optimizing network performance criteria
such as latency and latency variation. This document extends the
[RFC5541] with two new objective functions namely Minimum Latency
Path (MLP) OF and Minimum Latency Variation Path (MLVP) OF.
2. PCEP extensions
This section defines PCEP extensions for requirements outlined
in Section 1.
2.1. New Metric Object Types
This document defines the following four additional types for
the <METRIC> object defined in [RFC5440}. For explanation of
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these metrics, the following terminology is used and expanded
along the way.
- A network comprises of a set of N links {Li, (i=1...N)}.
- A path P of a P2P LSP is a list of K links {Lpi,(i=1...K)}.
2.1.1. P2P Latency Metric
Link delay metric is defined in [OSPF-TE-METRIC] and [ISIS-TE-
METRIC]. P2P latency metric type of <METRIC> object in PCEP
encodes the sum of the link delay metric of all links along a
P2P Path. Specifically, extending on the above mentioned
terminology:
- Link delay metric of link L is denoted D(L).
- P2P latency metric for the Path P = Sum {D(Lpi),
(i=1...K)}.
Value for P2P latency metric type is to be assigned by IANA
(suggested value: 11).
2.1.2. P2P Latency Variation Metric
Link delay variation metric is defined in [OSPF-TE-METRIC] and
[ISIS-TE-METRIC]. P2P latency variation metric type of <METRIC>
object in PCEP encodes a function of the link delay variation
metric of all links along a P2P Path. Specifically, extending on
the above mentioned terminology:
- Latency variation of link L is denoted DV(L).
- P2P latency variation metric for the Path P = Function
{DV(Lpi), (i=1...K)}.
Specification of the "Function" used to drive latency variation
metric of a path from latency variation metrics of individual
links along the path is beyond the scope of this document.
Value for P2P latency variation metric is to be assigned by IANA
(suggested value: 12).
2.1.3. P2MP Latency Metric
P2MP latency metric type of <METRIC> object in PCEP encodes the
path latency metric for destination that observes the worst
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latency metric among all destination of the P2MP tree.
Specifically, extending on the above mentioned terminology:
- A P2MP Tree T comprises of a set of M destinations {Dest_j,
(j=1...M)}
- P2P latency metric of the Path to destination Dest_j is
denoted by LM(Dest_j).
- P2MP latency metric for the P2MP tree T = Maximum
{LM(Dest_j), (j=1...M)}.
Value for P2MP latency metric is to be assigned by IANA
(suggested value: 13).
2.1.4. P2MP Latency Variation Metric
P2MP latency variation metric type of <METRIC> object in PCEP
encodes the path latency variation metric for destination that
observes the worst latency variation metric among all destination
of the P2MP tree. Specifically, extending on the above mentioned
terminology:
- A P2MP Tree T comprises of a set of M destinations {Dest_j,
(j=1...M)}
- P2P latency variation metric of the Path to destination
Dest_j is denoted by LVM(Dest_j).
- P2MP latency variation metric for the P2MP tree T = Maximum
{LVM(Dest_j), (j=1...M)}.
Value for P2MP latency variation metric is to be assigned by IANA
(suggested value: 14).
2.2. Handling of New Metric Object Types
This document does not propose any changes to handling of Metric
object. Specifically, the new metric types defined in this
document are handled in the same fashion as metric types defined
in [RFC5440].
2.3. New Objective Functions
This document extends the [RFC 5541] with two new objective
functions namely Minimum Latency Path (MLP) OF and Minimum
Latency Variation Path (MLVP) OF. The objective function code
for each of the new objective function is also defined.
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2.3.1. Minimum Latency Path Objective Function
Minimum Latency Path (MLP) OF is defined as an objective
function where a path is computed such that latency of the path
is minimized.
Objective function code for MLP OF is to be assigned by IANA
(suggested value: 9).
2.3.2. Minimum Latency Variation Path Objective Function
Minimum Latency Variation Path (MLVP) OF is defined as an
objective function where a path is computed such that latency
variation in the path is minimized.
Objective function code for MLVP OF is to be assigned by IANA
(suggested value: 10).
2.4. Handling of New Objective Functions
This document does not propose any changes to handling of <OF>
object. Specifically, the new OF types defined in this document
are handled in the same fashion as OF types defined in
[RFC5541].
3. Security Considerations
This document does not introduce any additional security issues
beyond those identified in [RFC5440], [RFC5541] and [RFC6006].
4. IANA Considerations
This document defines the following four additional types for
the <METRIC> object defined in [RFC5440].
Value Description
----- ------------
TBA (suggest value: 11) P2P latency metric
TBA (suggest value: 12) P2P latency variation metric
TBA (suggest value: 13) P2MP latency metric
TBA (suggest value: 14) P2MP latency variation metric
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This document defines the following two objective functions
codes for the <OF> object defined in [RFC5541].
Value Description
----- ------------
TBA (suggest value: 9) Minimum Latency Path (MLP) OF
TBA (suggest value: 10) Minimum Latency Variation Path (MLVP) OF
5. References
5.1. Normative References
[RFC5440] Vasseur, JP., Ed., and JL. Le Roux, Ed., "Path
Computation Element (PCE) Communication Protocol
(PCEP)", RFC 5440, March 2009.
[RFC5541] Le Roux, JL., Vasseur, JP., and Y. Lee, "Encoding of
Objective Functions in the Path Computation Element
Communication Protocol (PCEP)", RFC 5541, June 2009.
[DRAFT-OSPF-TE-METRIC] S. Giacalone, D. Ward, J. Drake, A.
Atlas, S. Previdi, "OSPF Traffic Engineering (TE)
Metric Extensions", draft-ietf-ospf-te-metric-
extensions, work in progress.
[DRAFT-ISIS-TE-METRIC] S. Previdi, S. Giacalone, D. Ward, J.
Drake, A. Atlas, C. Filsfils, "IS-IS Traffic
Engineering (TE) Metric Extensions", draft-previdi-
isis-te-metric-extensions, work in progress.
5.2. Informative References
[RFC6006] Zhao, Q., Ed., King, D., Ed., Verhaeghe, F., Takeda,
T., Ali, Z., and J. Meuric, "Extensions to the Path
Computation Element Communication Protocol (PCEP) for
Point-to-Multipoint Traffic Engineering Label Switched
Paths", RFC 6006, September 2010.
Authors' Addresses
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Zafar Ali
Cisco Systems
Email: zali@cisco.com
George Swallow
Cisco Systems
swallow@cisco.com
Clarence Filsfils
Cisco Systems
cfilsfil@cisco.com
Siva Sivabalan
Cisco Systems
msiva@cisco.com
Stefano Previdi
Cisco Systems
sprevidi@cisco.com
Kenji Kumaki
KDDI Corporation
Email: ke-kumaki@kddi.com
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