Internet DRAFT - draft-alvarez-pce-path-profiles
draft-alvarez-pce-path-profiles
Internet Engineering Task Force S. Alvarez
Internet-Draft S. Sivabalan
Intended status: Standards Track Z. Ali
Expires: May 11, 2015 Cisco Systems, Inc.
L. Tomotaki
Verizon
V. Lopez
Telefonica I+D
R. Shakir
BT
J. Tantsura
Ericsson
November 7, 2014
PCE Path Profiles
draft-alvarez-pce-path-profiles-04
Abstract
This document describes extensions to the Path Computation Element
(PCE) Communication Protocol (PCEP) to signal path profile
identifiers. A profile represents a list of path parameters or
policies that a PCEP peer may invoke on a remote peer using an opaque
identifier. When a path computation client (PCC) initiates a path
computation request, the PCC can signal profile identifiers to invoke
path parameters or policies defined on the PCE which would influence
the path computation. Similarly, when a PCE initiates or updates a
path, the PCE can signal profile identifiers to invoke path
parameters or policies defined on the PCC which would influence the
path setup.
Status of This Memo
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provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on May 11, 2015.
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Copyright Notice
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3
2. Motivation . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Path Profiles . . . . . . . . . . . . . . . . . . . . . . . . 4
4. Procedures . . . . . . . . . . . . . . . . . . . . . . . . . 4
4.1. Capability Advertisement . . . . . . . . . . . . . . . . 5
4.2. PCC-Initiated Paths . . . . . . . . . . . . . . . . . . . 5
4.2.1. Point-to-Point Paths . . . . . . . . . . . . . . . . 6
4.2.2. Point-to-Multipoint Paths . . . . . . . . . . . . . . 7
4.3. PCE-Initiated Paths . . . . . . . . . . . . . . . . . . . 7
5. Object Extensions . . . . . . . . . . . . . . . . . . . . . . 9
5.1. OPEN Object . . . . . . . . . . . . . . . . . . . . . . . 9
5.2. PATH-PROFILE Object . . . . . . . . . . . . . . . . . . . 9
6. Error Codes for PATH-PROFILE Object . . . . . . . . . . . . . 11
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 11
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11
9. Security Considerations . . . . . . . . . . . . . . . . . . . 11
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 11
10.1. Normative References . . . . . . . . . . . . . . . . . . 11
10.2. Informative References . . . . . . . . . . . . . . . . . 12
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 12
1. Introduction
[RFC4655] specifies an architecture to address path computation
requirements in large, multi-domain, multi-region and multi-layer
networks. The architecture defines two main functional nodes: a path
computation client (PCC) and a path computation element (PCE). It
includes considerations for centralized versus distributed
computation, synchronization, PCE discovery, PCE load balancing, PCE
liveness detection, PCC-PCE and PCE-PCE communication, Traffic
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Engineering Database (TED) synchronization, stateful versus stateless
PCEs, monitoring, policy, confidentiality, and evaluation metrics.
[RFC5440] specifies the PCE Protocol (PCEP) for communications
between a PCC and a PCE, or between two PCEs.
[I-D.ietf-pce-stateful-pce] specifies PCEP extensions for stateful
control of LSPs including LSP state synchronization between PCCs and
PCEs, delegation of LSP control to PCEs, and PCE control of timing
and sequence of path computations within and across PCEP sessions.
[I-D.ietf-pce-pce-initiated-lsp] introduces PCEP extensions to allow
a stateful PCE to set up, maintain and tear down LSPs without the
need for local configuration on the PCC.
This document describes PCEP extensions to signal path profile
identifiers. A profile represents a list of path parameters or
policies that a PCEP peer may invoke on a remote peer using an opaque
identifier. The PCE may be stateful or stateless. When a path
computation client (PCC) initiates a path computation request, the
PCC can signal profile identifiers to invoke path parameters or
policies defined on the PCE which would influence the path
computation. Similarly, when a PCE initiates or updates a path, the
PCE can signal profile identifiers to invoke path parameters or
policies defined on the PCC which would influence the path setup.
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 RFC 2119 [RFC2119].
2. Motivation
PCEP peers may need to specify request-specific parameters and
policies without signaling them explicitly. The signaling of one or
more path profile identifiers allows peers to make use of opaque
identifiers to implicitly communicate such information. An important
characteristic of this approach is that the transmitting peer does
not need to know the specifics of the profiles and can invoke new
functional enhancements on the receiving peer without requiring
changes to its implementation.
There are multiple reasons why the explicit communication of some
parameters and policies may not be possible or desirable. The
transmitting peer may not implement the protocol extensions required
or such extensions do not exist. The defintion of some parameters
and policies may be located on the receiving peer as a matter of
operational preference. The parameters and policies may not be
directly related to computation or instantiation of the path, but may
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be related to other functionality associated with the path (e.g.
traffic steering, accounting, monitoring, etc).
A PCC may use path profiles in numerous scenarios when requesting a
path computation. For example, a PCE may be provisioned with a
policy profile that enforces path diversity, elaborate dependencies
between paths or time-based behaviors. Alternative, a PCE may be
provisioned with a set of configuration profiles that define path
computation parameters. These policies and configuration parameters
can be centrally managed on the PCE and made effective across
multiple PCCs. A PCC does not need to know the specifics of the
profiles and is able to invoke new PCE functionality without changes
to its implementation.
Similarly, a PCE may use path profiles in numerous scenarios when
initiating or updating a path on a PCC. A PCC may be provisioned
with a set of configuration and policy profiles that may be applied
to paths. For example, those profiles could specify a policy to
steer traffic into the path or configuration parameters related to
traffic accounting, event logging, path monitoring, etc. A PCE can
invoke these policies and configuration, so the PCC can establish a
more completly configured path. A PCE does not need to know the
specifics of the profiles and is able to invoke new PCC functionality
without changes to its implementation.
3. Path Profiles
A path profile represents a list of path parameters or policies that
a PCEP peer may invoke on a remote peer using a profile identifier.
The receiving peer interprets the identifier according to a local
path profile definition. The PATH-PROFILE object defined in
Section 5.2 can signal one or more profile identifiers. PCEP carries
profile identifiers as opaque values. PCEP peers do not exchange the
details of a path profile.
Regarding policies in particular, the PCE path profile specifications
in this document enable a new type of policy realization in the PCE
architecture. They define an approach where request-specific
policies may be communicated implicitly to achieve some level of
coordination of policy between PCEP peers. [RFC4655] defines the
current policy realization options and policy types in the PCE
architecture.
4. Procedures
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4.1. Capability Advertisement
PCEP peers advertise their capability to support path profile
identifiers during the session initialization phase. They include
the PATH-PROFILE-CAPABILITY TLV defined in Section 5.1 as part of the
OPEN object. A PCEP peer can only signal path profile identifiers if
both peers advertised this capability. A peer MUST send a PCErr
message with Error-Type=4 (Not supported object), Error-value=1 (Not
supported object class) and close the session if it receives a
message with a path profile identifier, it supports the extensions in
this document and both peers did not advertise this capability.
4.2. PCC-Initiated Paths
A PCC MAY include a PATH-PROFILE object when sending a PCReq message.
The PCE uses the path profile identifiers to select path parameters
or path policies to fulfill the request. The PCE MUST process the
identifiers in the PATH-PROFILE object in the order received. The
means by which the PCC learns about a particular path profile
identifier and decides to include it in a PCReq message are outside
the scope of this document. Similarly, the means by which the PCE
selects a set of parameters or policies based on the profile
identifier for a specific request are outside the scope of this
document. The P flag of the PATH-PROFILE object MUST be set.
A PCE may receive a path computation request with one or more
unexpected path profile identifiers. The PCE sends a PCErr message
with Error-Type=[TBA] (PATH-PROFILE Error), Error-value=1 (Unknown
path profile) if the path profile identifier is not known to the PCE.
The PCE sends a PCErr message with Error-Type=[TBA] (PATH-PROFILE
Error), Error-value=2 (Invalid path profile) if the PCE knows about
the path profile identifier, but considers the request invalid. As
an example, the profile may be invalid because of the path type, the
PCEP session type or the originating PCC. The PCE sends a PCErr
message with Error-Type=[TBA] (PATH-PROFILE Error), Error-value=3
(Incompatible path profiles) if two or more path profile identifiers
are incompatible. That is, they are known and valid, but can not
occur simultanously. The PCEP-ERROR object SHOULD include the path
profile identifiers that generated the error condition.
The PCE will determine whether to consider any additional optional
objects included in a PCReq message based on policy. As illustrated
in Section 4.2.1 and Section 4.2.2, the PCC MAY include other
optional objects along with a PATH-PROFILE object as part of a path
computation request. The PCC will use the processing-rule (P) flag
in the common object header to signal whether it considers those
objects mandatory or optional when the PCE performs path computation.
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Those objects may overlap with the path parameters that the PCE
associates with the path profile identifier.
PCE policy may place different kinds of restrictions on PCReq
messages that include a PATH-PROFILE object and additional
parameters. A PCE MUST send an error message if it receives a
request with optional objects signaled as mandatory (P flag = 1) for
path computation and PCE policy does not allow such behavior from the
originating PCC. In that case, the PCE sends a PCErr message with
Error-Type=[TBA] (PATH-PROFILE Error), Error-value=3 (Unexpected
mandatory object). If the objects are signaled as optional (P flag =
0) for path computation, the PCE will decide based on policy whether
to consider them or not. When sending the PCRep message for the
request, the PCE will use the ignore (I) flag in the common object
header to indicate to the PCC whether an object was ignored.
4.2.1. Point-to-Point Paths
[RFC5440] defines the basic structure of a PCReq message for point-
to-point paths. This documents extends the message format as
follows:
<PCReq Message>::= <Common Header>
[<svec-list>]
<request-list>
where:
<svec-list>::=<SVEC>[<svec-list>]
<request-list>::=<request>[<request-list>]
<request>::= <RP>
<END-POINTS>
[<PATH-PROFILE>]
[<path-computation>]
where:
<path-computation> is the list of optional objects used for path
computation as defined initially in [RFC5440] and modified in
subsequent PCEP extensions.
If present in a PCReq message, the PATH-PROFILE object MUST be the
first optional object in the request portion of the message.
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4.2.2. Point-to-Multipoint Paths
[RFC6006] defines the basic structure of a PCReq message for point-
to-multipoint paths. This documents extends the message format as
follows:
<PCReq Message>::= <Common Header>
<request>
where:
<request>::= <RP>
<end-point-rro-pair-list>
[<PATH-PROFILE>]
[<OF>]
[<LSPA>]
[<BANDWIDTH>]
[<metric-list>]
[<IRO>]
[<LOAD-BALANCING>]
where:
<end-point-rro-pair-list>::=
<END-POINTS>[<RRO-List>][<BANDWIDTH>]
[<end-point-rro-pair-list>]
<RRO-List>::=<RRO>[<BANDWIDTH>][<RRO-List>]
<metric-list>::=<METRIC>[<metric-list>]
If present in a PCReq message, the PATH-PROFILE object MUST be the
first optional object in the request portion of the message.
4.3. PCE-Initiated Paths
A PCE MAY include a PATH-PROFILE object when sending a PCInitiate
message as defined in [I-D.ietf-pce-pce-initiated-lsp]. The PCC uses
the path profile identifiers to select path parameters or path
policies to be applied during the instantiation of the path. The PCC
MUST process the identifiers in the PATH-PROFILE object in the order
received. The means by which the PCE learns about a particular path
profile identifier and decides to include it in a PCInitiate message
are outside the scope of this document. Similarly, the means by
which the PCC selects a set of parameters or policies based on the
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profile identifier for a specific path are outside the scope of this
document.
A PCC may receive a path instantiation request with one or more
unexpected path profile identifiers. The PCC sends a PCErr message
with Error-Type=[TBA] (PATH-PROFILE Error), Error-value=1 (Unknown
path profiles) if the path profile identifier is not known to the
PCC. The PCC sends a PCErr message with Error-Type=[TBA] (PATH-
PROFILE Error), Error-value=2 (Invalid path profiles) if the PCC
knows about the path profile identifier, but considers the request
invalid. As an example, the profile may be invalid because of the
path type, the PCEP session type or the originating PCE. The PCC
sends a PCErr message with Error-Type=[TBA] (PATH-PROFILE Error),
Error-value=3 (Incompatible path profiles) if two or more path
profile identifiers are incompatible. That is, they are known and
valid, but can not occur simultanously. The PCEP-ERROR object SHOULD
include the path profile identifiers that generated the error
condition.
[I-D.ietf-pce-pce-initiated-lsp] defines the basic structure of a
PCInitiate message. This documents extends the message format as
follows:
<PCInitiate Message> ::= <Common Header>
<PCE-initiated-lsp-list>
Where:
<PCE-initiated-lsp-list> ::= <PCE-initiated-lsp-request>
[<PCE-initiated-lsp-list>]
<PCE-initiated-lsp-request> ::= (<PCE-initiated-lsp-instantiation>|
<PCE-initiated-lsp-deletion>)
<PCE-initiated-lsp-instantiation> ::= <SRP>
<LSP>
<END-POINTS>
<ERO>
[PATH-PROFILE>
[<attribute-list>]
<PCE-initiated-lsp-deletion> ::= <SRP>
<LSP>
where:
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<attribute-list> is defined in [RFC5440] and extended by PCEP
extensions.
5. Object Extensions
5.1. OPEN Object
This documents defines a new optional PATH-PROFILE-CAPABILITY TLV in
the OPEN object.
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=[TBA] | Length=4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved | Flags |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
PATH-PROFILE-CAPABILITY TLV
Figure 1
Reserved (16 bits):
MUST be set to zero on transmission and ignored on receipt.
Flags (16 bits):
Unassigned bits are considered reserved. They MUST be set to zero
on transmission and ignored on receipt. No flags are currently
defined.
5.2. PATH-PROFILE Object
The PATH-PROFILE object may be carried in PCReq, PCInitiate and PCUpd
messages.
PATH-PROFILE Object-Class is [TBA].
PATH-PROFILE Object-Type is 1.
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
// TLVs //
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
PATH-PROFILE Object
Figure 2
The PATH-PROFILE object has a variable length and contains one or
more PATH-PROFILE-ID TLVs.
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=[TBD] | Length=10 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved | Flags | Path Profile Id |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Path Profile Id (cont) | Extended Id |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Extended Id (cont) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
PATH-PROFILE-ID TLV
Figure 3
Reserved (8 bits):
MUST be set to zero on transmission and ignored on receipt.
Flags (8 bits):
0x01 (X) - Extended Id Flag
It indicates to the receiver that an extended
identifier associated with Path Profile Id is present.
Path Profile Id (32 bits):
(non-zero) unsigned path profile identifier.
Extended Id (32 bits):
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Extended identifier associated with Path Profile Id. MUST be set
to zero on transmission and ignored on receipt unless the Extended
Id flag is set.
If more than one PATH-PROFILE object is present, the first one MUST
be processed and subsequent objects ignored.
6. Error Codes for PATH-PROFILE Object
Error-Type Meaning Error-Value
<TBA> PATH-PROFILE Error 1: Unknown path profiles
2: Invalid path profiles
3: Incompatible path profiles
4: Unexpected mandatory object
7. Acknowledgements
The authors would like to thank Clarence Filsfils for his valuable
comments.
8. IANA Considerations
IANA is requested to assign the following code points.
PATH-PROFILE-CAPABILITY TLV
PATH-PROFILE Object-Class
PATH-PROFILE Object-Type
PATH-PROFILE Error-Type
9. Security Considerations
This document does not introduce new security concerns. The security
considerations in [RFC4655], [I-D.ietf-pce-stateful-pce] and
[I-D.ietf-pce-pce-initiated-lsp] remain relevant.
10. References
10.1. Normative References
[I-D.ietf-pce-pce-initiated-lsp]
Crabbe, E., Minei, I., Sivabalan, S., and R. Varga, "PCEP
Extensions for PCE-initiated LSP Setup in a Stateful PCE
Model", draft-ietf-pce-pce-initiated-lsp-00 (work in
progress), December 2013.
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[I-D.ietf-pce-stateful-pce]
Crabbe, E., Medved, J., Minei, I., and R. Varga, "PCEP
Extensions for Stateful PCE", draft-ietf-pce-stateful-
pce-08 (work in progress), February 2014.
[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.
[RFC6006] Zhao, Q., King, D., 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.
10.2. Informative References
[RFC4655] Farrel, A., Vasseur, J., and J. Ash, "A Path Computation
Element (PCE)-Based Architecture", RFC 4655, August 2006.
Authors' Addresses
Santiago Alvarez
Cisco Systems, Inc.
170 West Tasman Drive
San Jose, CA 95134
USA
Email: saalvare@cisco.com
Siva Sivabalan
Cisco Systems, Inc.
2000 Innovation Drive
Kanata, ON K2K-3E8
Canada
Email: msiva@cisco.com
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Zafar Ali
Cisco Systems, Inc.
2000 Innovation Drive
Kanata, ON K2K-3E8
Canada
Email: zali@cisco.com
Luis Tomotaki
Verizon
400 International
Richardson, TX 75081
US
Email: luis.tomotaki@verizon.com
Victor Lopez
Telefonica I+D
c/ Don Ramon de la Cruz 84
Madrid 28006
Spain
Email: vlopez@tid.es
Rob Shakir
BT
London
UK
Email: rob.shakir@bt.com
Jeff Tantsura
Ericsson
300 Holger Way
San Jose, CA 95134
US
Email: Jeff.Tantsura@ericsson.com
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