Extensions to the Path Computation Element Communication Protocol (PCEP) to compute service aware Label Switched Path (LSP).
draft-dhody-pce-pcep-service-aware-02
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 | Dhruv Dhody , Vishwas Manral | ||
| Last updated | 2011-12-14 (Latest revision 2011-09-09) | ||
| Replaced by | draft-ietf-pce-pcep-service-aware, RFC 8233 | ||
| RFC stream | (None) | ||
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| Consensus boilerplate | Unknown | ||
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| IESG | IESG state | I-D Exists | |
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draft-dhody-pce-pcep-service-aware-02
PCE Working Group D. Dhody
Internet-Draft Huawei Technologies India Pvt
Intended status: Standards Track Ltd
Expires: June 17, 2012 V. Manral
Hewlett-Packard Corp.
December 15, 2011
Extensions to the Path Computation Element Communication Protocol (PCEP)
to compute service aware Label Switched Path (LSP).
draft-dhody-pce-pcep-service-aware-02
Abstract
In certain networks like financial information network (stock/
commodity trading) and enterprises using cloud based applications,
Latency (delay), Latency-Variation (jitter) and Packet loss is
becoming a key requirement for path computation along with other
constraints and metrics. Latency, Latency-Variation and Packet Loss
is associated with the Service Level Agreement (SLA) between
customers and service providers.
[MPLS-DELAY-FWK] describes MPLS architecture to allow latency, loss
and jittering as properties. [OSPF-TE-EXPRESS] and [ISIS-TE-EXPRESS]
describes mechanisms with which network performance information is
distributed via OSPF and ISIS respectivily. This document describes
the extension to PCEP to carry Latency, Latency-Variation and Loss as
constraints for end to end path computation.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
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 June 17, 2012.
Copyright Notice
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Copyright (c) 2011 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.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Requirement for PCEP . . . . . . . . . . . . . . . . . . . . . 4
4. Objects . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
4.1. Latency (Delay) Metric . . . . . . . . . . . . . . . . . . 5
4.2. Latency Variation (Jitter) Metric . . . . . . . . . . . . 6
4.3. Packet Loss Metric . . . . . . . . . . . . . . . . . . . . 6
4.4. Non-Understanding / Non-Support of Service Aware Path
Computation . . . . . . . . . . . . . . . . . . . . . . . 7
4.5. Mode of Operation . . . . . . . . . . . . . . . . . . . . 7
4.5.1. Examples . . . . . . . . . . . . . . . . . . . . . . . 8
5. Protocol Consideration . . . . . . . . . . . . . . . . . . . . 8
5.1. Inter domain Consideration . . . . . . . . . . . . . . . . 8
5.1.1. Inter-AS Link . . . . . . . . . . . . . . . . . . . . 8
5.1.2. Inter-Layer Consideration . . . . . . . . . . . . . . 8
5.2. Reoptimization Consideration . . . . . . . . . . . . . . . 9
5.3. P2MP . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
7. Security Considerations . . . . . . . . . . . . . . . . . . . 9
8. Manageability Considerations . . . . . . . . . . . . . . . . . 9
8.1. Control of Function and Policy . . . . . . . . . . . . . . 9
8.2. Information and Data Models . . . . . . . . . . . . . . . 9
8.3. Liveness Detection and Monitoring . . . . . . . . . . . . 10
8.4. Verify Correct Operations . . . . . . . . . . . . . . . . 10
8.5. Requirements On Other Protocols . . . . . . . . . . . . . 10
8.6. Impact On Network Operations . . . . . . . . . . . . . . . 10
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 10
9.1. Normative References . . . . . . . . . . . . . . . . . . . 10
9.2. Informative References . . . . . . . . . . . . . . . . . . 10
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1. Introduction
Real time Network Performance is becoming a critical in the path
computation in some networks. There exist mechanism described in
[RFC6374] to measure latency, latency-Variation and packet loss after
the LSP has been established, which is inefficient. It's important
that latency, latency-variation and packet loss are considered during
path selection process itself.
TED is populated with network performance information like link
latency, latency variation and packet loss through [OSPF-TE-EXPRESS]
or [ISIS-TE-EXPRESS]. Path Computation Client (PCC) can request Path
Computation Element (PCE) to provide a path meeting end to end
network performance criteria. This document extends Path Computation
Element Communication Protocol (PCEP) [RFC5440] to handle network
performance constraint.
1.1. 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 RFC2119.
2. Terminology
The following terminology is used in this document.
IGP: Interior Gateway Protocol. Either of the two routing
protocols, Open Shortest Path First (OSPF) or Intermediate System
to Intermediate System (IS-IS).
IS-IS: Intermediate System to Intermediate System.
OSPF: Open Shortest Path First.
PCC: Path Computation Client: any client application requesting a
path computation to be performed by a Path Computation Element.
PCE: Path Computation Element. An entity (component, application,
or network node) that is capable of computing a network path or
route based on a network graph and applying computational
constraints.
TE: Traffic Engineering.
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3. Requirement for PCEP
End-to-end service optimization based on latency, latency-variation
and packet loss is a key requirement for service provider. Following
key requirements associated with latency, latency-variation and loss
is identified for PCEP:
1. Path Computation Element (PCE) supporting this draft MUST have
the capability to compute end-to-end path with latency, latency-
variation and packet loss constraints. It MUST also support the
combination of network performance constraint (latency, latency-
variation, loss...) with existing constraints (cost, hop-
limit...)
2. Path Computation Client (PCC) supporting this draft MUST be able
to request for network performance constraint in path request
message as the key constraint to be optimized or to suggest
boundary condition that should not be crossed.
3. PCEs are not required to support service aware path computation.
Therefore, it MUST be possible for a PCE to reject a Path
Computation Request message with a reason code that indicates no
support for service-aware path computation.
4. PCEP supporting this draft SHOULD provide a means to return end
to end network performance information of the computed path in
the reply message.
5. PCEP supporting this draft SHOULD provide mechanism to compute
multi-domain (e.g., Inter-AS, Inter-Area or Multi-Layer) service
aware paths.
It must be understood that such constraints are only meaningful if
used consistently: for instance, if the delay of a computed path
segment is exchanged between two PCEs residing in different domains,
consistent ways of defining the delay must be used.
4. Objects
This section defines PCEP extensions (see [RFC5440]) so as to support
network performance and service aware path computation.
[RFC5440] defines the optional METRIC object for several purposes.
In a PCReq message, a PCC MAY insert one or more METRIC objects to
indicate the metric that MUST be optimized or to indicate a bound on
the path that MUST NOT be exceeded for the path to be considered as
acceptable by the PCC. In a PCRep message, the METRIC object MAY be
inserted so as to provide the value for the computed path. It MAY
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also be inserted within a PCRep with the NO-PATH object to indicate
that the metric constraint could not be satisfied.
As per [RFC5440] the format of the METRIC object body is as follows:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved | Flags |C|B| T |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| metric-value |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
T (Type - 8 bits): Specifies the metric type.
Three values are currently defined:
* T=1: IGP metric
* T=2: TE metric
* T=3: Hop Counts
Based on the section 3, PCEP is extended to define new METRIC types
for network performance constraints.
4.1. Latency (Delay) Metric
The end to end Latency (Delay) for the path is represented by this
metric.
* T=13(IANA): Latency metric
PCC MAY use this latency metric In PCReq to request a path meeting
the end to end latency requirement. In this case B bit MUST be set
to suggest a bound (a maximum) for the path latency metric that must
not be exceeded for the PCC to consider the computed path as
acceptable. The path metric must be less than or equal to the value
specified in the metric-value field.
PCC MAY also use this metric to ask PCE to optimize delay during path
computation, in this case B flag will be cleared.
PCE MAY use this latency metric In PCRep along with NO-PATH object
incase PCE cannot compute a path meeting this constraint. PCE MAY
also use this metric to reply the computed end to end latency metric
to PCC.
The metric value represents the end to end Latency (delay) measured
in milliseconds.
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4.2. Latency Variation (Jitter) Metric
The end to end Latency Variation (Jitter) for the path is represented
by this metric.
* T=14(IANA): Latency Variation metric
PCC MAY use this latency variation metric In PCReq to request a path
meeting the end to end latency variation requirement. In this case B
bit MUST be set to suggest a bound (a maximum) for the path latency
variation metric that must not be exceeded for the PCC to consider
the computed path as acceptable. The path metric must be less than
or equal to the value specified in the metric-value field.
PCC MAY also use this metric to ask PCE to optimize jitter during
path computation, in this case B flag will be cleared.
PCE MAY use this latency variation metric In PCRep along with NO-PATH
object incase PCE cannot compute a path meeting this constraint. PCE
MAY also use this metric to reply the computed end to end latency
variation metric to PCC.
The metric value represents the end to end Latency variation (jitter)
measured in microseconds.
4.3. Packet Loss Metric
The end to end Packet Loss for the path is represented by this
metric.
* T=15(IANA): Packet Loss metric
PCC MAY use this packet loss metric In PCReq to request a path
meeting the end to end packet loss requirement. In this case B bit
MUST be set to suggest a bound (a maximum) for the path packet loss
metric that must not be exceeded for the PCC to consider the computed
path as acceptable. The path metric must be less than or equal to
the value specified in the metric-value field.
PCC MAY also use this metric to ask PCE to optimize packet loss
during path computation, in this case B flag will be cleared.
PCE MAY use this packet loss metric In PCRep along with NO-PATH
object incase PCE cannot compute a path meeting this constraint. PCE
MAY also use this metric to reply the computed end to end packet loss
metric to PCC.
The metric value represents the end to end packet loss measured as a
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percentage and represented in 32 bit floating point.
4.4. Non-Understanding / Non-Support of Service Aware Path Computation
If the P bit is clear in the object header and PCE doesn't understand
or doesn't support service aware path computation it SHOULD simply
ignore this METRIC.
If the P Bit is set in the object header and PCE receives new METRIC
type in path request and it understands the METRIC type, but the PCE
is not capable of service aware path computation, the PCE MUST send a
PCErr message with a PCEP-ERROR Object Error-Type = 4 (Not supported
object) [RFC5440]. The path computation request MUST then be
cancelled.
If the PCE does not understand the new METRIC type, then the PCE MUST
send a PCErr message with a PCEP-ERROR Object Error-Type = 3 (Unknown
object) [RFC5440].
4.5. Mode of Operation
As explained in [RFC5440], The METRIC object is optional and can be
used for several purposes. In a PCReq message, a PCC MAY insert one
or more METRIC objects:
o To indicate the metric that MUST be optimized by the path
computation algorithm (Latency, Latency-Variation or Loss)
o To indicate a bound on the path METRIC (Latency, Latency-Variation
or Loss) that MUST NOT be exceeded for the path to be considered
as acceptable by the PCC.
In a PCRep message, the METRIC object MAY be inserted so as to
provide the METRIC (Latency, Latency-Variation or Loss) for the
computed path. It MAY also be inserted within a PCRep with the NO-
PATH object to indicate that the metric constraint could not be
satisfied.
The path computation algorithmic aspects used by the PCE to optimize
a path with respect to a specific metric are outside the scope of
this document.
All the rules of processing METRIC object as explained in [RFC5440]
are applicable to the new metric types as well.
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4.5.1. Examples
If a PCC sends a path computation request to a PCE where the metric
to optimize is the latency and the packet loss must not exceed the
value of M, two METRIC objects are inserted in the PCReq message:
o First METRIC object with B=0, T=13, C=1, metric-value=0x0000
o Second METRIC object with B=1, T=15, metric-value=M
If a path satisfying the set of constraints can be found by the PCE
and there is no policy that prevents the return of the computed
metric, the PCE inserts one METRIC object with B=0, T=13, metric-
value= computed end to end latency. Additionally, the PCE may insert
a second METRIC object with B=1, T=15, metric-value= computed end to
end packet loss.
5. Protocol Consideration
There is no change in the message format of Path Request and Reply
Message.
5.1. Inter domain Consideration
[RFC5441] describes the BRPC procedure to compute end to end
optimized inter domain path by cooperating PCEs. The network
performance constraints can be applied end to end in similar manner
as IGP or TE cost.
All domains should have the same understanding of the METRIC
(Latency-Variation etc) for end-to-end inter-domain path computation
to make sense. Otherwise some form of Metric Normalization as
described in [RFC5441] MAY need to be applied.
5.1.1. Inter-AS Link
The IGP in each neighbor domain can advertise its inter-domain TE
link capabilities, this has been described in [RFC5316] (ISIS) and
[RFC5392] (OSPF). The network performance link properties are
described in [OSPF-TE-EXPRESS] and [ISIS-TE-EXPRESS], the same
properties must be advertised using the mechanism described in
[RFC5392] (OSPF) and [RFC5316] (ISIS).
5.1.2. Inter-Layer Consideration
PCEP supporting this draft SHOULD provide mechanism to support
differnt Metric requirements for different Layers. This is important
as the network performance metric would be different for Packet and
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Optical (TDM, LSC etc) Layers. In order to allow different Metric-
Value to be applied within different network layers, multiple METRIC
objects of the same type MAY be present. In such a case, the first
METRIC object specifies an metric for the higher-layer network, and
subsequent METRIC objects specify objection functions of the
subsequent lower-layer networks.
5.2. Reoptimization Consideration
PCC can monitor the setup LSPs and incase of degradation of network
performance constraints, it MAY ask PCE for reoptimization as per
[RFC5440].
5.3. P2MP
The scope of the network performance constraints as listed in this
document needs to be described in terms of P2MP TE LSPs.
This section needs further discussions.
6. IANA Considerations
IANA has defined a registry for new METRIC type.
Type Meaning
13(TBD) Latency (delay) metric
14(TBD) Latency Variation (jitter) metric
15(TBD) Packet Loss metric
7. Security Considerations
This document defines three new METRIC Types with does not add any
new security concerns to PCEP protocol.
8. Manageability Considerations
8.1. Control of Function and Policy
The only configurable item is the support of the new service-aware
METRICS on a PCE which MAY be controlled by a policy module. If the
new METRIC is not supported/allowed on a PCE, it MUST send a PCErr
message as specified in Section 4.4.
8.2. Information and Data Models
[PCEP-MIB] describes the PCEP MIB, there are no new MIB Objects for
this document.
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8.3. Liveness Detection and Monitoring
Mechanisms defined in this document do not imply any new liveness
detection and monitoring requirements in addition to those already
listed in [RFC5440].
8.4. Verify Correct Operations
Mechanisms defined in this document do not imply any new operation
verification requirements in addition to those already listed in
[RFC5440].
8.5. Requirements On Other Protocols
PCE requires the TED to be populated with network performance
information like link latency, latency variation and packet loss.
This mechanims is described in [OSPF-TE-EXPRESS] or
[ISIS-TE-EXPRESS].
8.6. Impact On Network Operations
Mechanisms defined in this document do not have any impact on network
operations in addition to those already listed in [RFC5440].
9. References
9.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to
Indicate Requirement Levels", BCP 14, RFC 2119,
March 1997.
[RFC5440] Vasseur, JP. and JL. Le Roux, "Path Computation
Element (PCE) Communication Protocol (PCEP)",
RFC 5440, March 2009.
9.2. Informative References
[RFC4655] Farrel, A., Vasseur, J., and J. Ash, "A Path
Computation Element (PCE)-Based Architecture",
RFC 4655, August 2006.
[RFC4657] Ash, J. and J. Le Roux, "Path Computation Element
(PCE) Communication Protocol Generic
Requirements", RFC 4657, September 2006.
[RFC5441] Vasseur, JP., Zhang, R., Bitar, N., and JL. Le
Roux, "A Backward-Recursive PCE-Based Computation
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(BRPC) Procedure to Compute Shortest Constrained
Inter-Domain Traffic Engineering Label Switched
Paths", RFC 5441, April 2009.
[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.
[RFC5392] Chen, M., Zhang, R., and X. Duan, "OSPF Extensions
in Support of Inter-Autonomous System (AS) MPLS
and GMPLS Traffic Engineering", RFC 5392,
January 2009.
[RFC6374] Frost, D. and S. Bryant, "Packet Loss and Delay
Measurement for MPLS Networks", RFC 6374,
September 2011.
[MPLS-DELAY-FWK] Fu, X., Manral, V., McDysan, D., Malis, A.,
Giacalone, S., Betts, M., Wang, Q., and J. Drake,
"Traffic Engineering architecture for services
aware MPLS
[draft-fuxh-mpls-delay-loss-te-framework]",
Oct 2011.
[OSPF-TE-EXPRESS] Giacalone, S., Ward, D., Drake, J., Atlas, A., and
V. Previdi, "OSPF Traffic Engineering (TE) Express
Path [draft-giacalone-ospf-te-express-path]",
Sept 2011.
[ISIS-TE-EXPRESS] Previdi, S., Giacalone, S., Ward, D., Drake, J.,
Atlas, A., and C. Filsfils, "IS-IS Traffic
Engineering (TE) Metric Extensions
[draft-previdi-isis-te-metric-extensions]",
Oct 2011.
[PCEP-MIB] Kiran Koushik, A S., Stephan, E., Zhao, Q., and D.
King, "PCE communication protocol(PCEP) Management
Information Base", July 2010.
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Authors' Addresses
Dhruv Dhody
Huawei Technologies India Pvt Ltd
Leela Palace
Bangalore, Karnataka 560008
INDIA
EMail: dhruv.dhody@huawei.com
Vishwas Manral
Hewlett-Packard Corp.
191111 Pruneridge Ave.
Cupertino, CA 95014
USA
EMail: vishwas.manral@hp.com
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