| Internet Engineering Task Force | S. Alvarez |
| Internet-Draft | S. Sivabalan |
| Intended status: Standards Track | Z. Ali |
| Expires: September 05, 2014 | Cisco Systems, Inc. |
| L. Tomotaki | |
| Verizon | |
| V. Lopez | |
| Telefonica I+D | |
| March 04, 2014 |
PCE Path Profiles
draft-alvarez-pce-path-profiles-02
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.
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Copyright (c) 2014 IETF Trust and the persons identified as the document authors. All rights reserved.
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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].
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 4.2 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. The PCE may be stateful or stateless.
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 4.1 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.
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 3.2.1 and Section 3.2.2, 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. 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.
[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>
<svec-list>::=<SVEC>[<svec-list>]
<request-list>::=<request>[<request-list>]
<request>::= <RP>
<END-POINTS>
[<PATH-PROFILE>]
[<path-computation>]
where:
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.
[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>
<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>]
where:
If present in a PCReq message, the PATH-PROFILE object MUST be the first optional object in the request portion of the message.
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 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:
<attribute-list> is defined in [RFC5440] and extended by PCEP extensions.
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
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.
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=6 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved | Flags | Path Profile Id |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Path Profile Id (cont) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
PATH-PROFILE-ID TLV
Figure 3
If more than one PATH-PROFILE object is present, the first one MUST be processed and subsequent objects ignored.
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
The authors would like to thank Clarence Filsfils for his valuable comments.
IANA is requested to assign the following code points.
TBD
| [RFC4655] | Farrel, A., Vasseur, J.-P. and J. Ash, "A Path Computation Element (PCE)-Based Architecture", RFC 4655, August 2006. |