Network Working Group S. Sivabalan, Ed.
Request for Comments: 5455 J. Parker
Category: Standards Track S. Boutros
Cisco Systems, Inc.
K. Kumaki
KDDI R&D Laboratories, Inc.
March 2009
Diffserv-Aware Class-Type Object for
the Path Computation Element Communication Protocol
Status of This Memo
This document specifies an Internet standards track protocol for the
Internet community, and requests discussion and suggestions for
improvements. Please refer to the current edition of the "Internet
Official Protocol Standards" (STD 1) for the standardization state
and status of this protocol. Distribution of this memo is unlimited.
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Abstract
This document specifies a CLASSTYPE object to support Diffserv-Aware
Traffic Engineering (DS-TE) where path computation is performed with
the aid of a Path Computation Element (PCE).
Sivabalan, et al. Standards Track [Page 1]
RFC 5455 DS Aware CT Object for PCEP March 2009
Table of Contents
1. Introduction ....................................................2
1.1. Conventions Used in This Document ..........................3
2. Terminology .....................................................3
3. CLASSTYPE Object ................................................3
3.1. Object Definition ..........................................4
3.2. Path Computation Request Message with CLASSTYPE Object .....4
3.3. Processing CLASSTYPE Object ................................5
3.4. Determination of Traffic Engineering Class (TE-Class) ......6
3.5. Significance of Class-Type and TE-Class ....................6
3.6. Error Codes for CLASSTYPE Object ...........................6
4. Security Considerations .........................................7
5. IANA Considerations .............................................7
6. Acknowledgments .................................................7
7. References ......................................................8
7.1. Normative References .......................................8
7.2. Informative References .....................................8
1. Introduction
[RFC5440] specifies the Path Computation Element Communication
Protocol (PCEP) for communications between a Path Computation Client
(PCC) and a Path Computation Element (PCE), or between two PCEs, in
compliance with [RFC4657].
Diffserv-aware MPLS Traffic Engineering (DS-TE) addresses the
fundamental requirement to be able to enforce different bandwidth
constraints for different classes of traffic. It describes
mechanisms to achieve per-class traffic engineering, rather than on
an aggregate basis across all classes by enforcing Bandwidth
Constraints (BCs) on different classes. Requirements for DS-TE and
the associated protocol extensions are specified in [RFC3564] and
[RFC4124], respectively.
As per [RFC4657], PCEP must support traffic Class-Type as an MPLS-
TE-specific constraint. However, in the present form, PCEP [RFC5440]
does not have the capability to specify the Class-Type in the path
computation request.
In this document, we define a new PCEP object called CLASSTYPE, which
carries the Class-Type of the TE LSP in the path computation request.
During path computation, a PCE uses the Class-Type to identify the
bandwidth constraint of the TE LSP.
Sivabalan, et al. Standards Track [Page 2]
RFC 5455 DS Aware CT Object for PCEP March 2009
1.1. 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].
2. Terminology
CT (Class-Type): A set of Traffic Trunks governed by a set of
bandwidth constraints. Used for the purpose of link bandwidth
allocation, constraint-based routing and admission control. A given
Traffic Trunk belongs to the same CT on all links.
DS-TE: Diffserv-Aware Traffic Engineering.
LSR: Label Switching Router.
LSP: Label Switched Path.
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.
PCEP Peer: an element involved in a PCEP session (i.e., a PCC or the
PCE).
TE-Class: A pair consisting of a Class-Type and a preemption priority
allowed for that Class-Type. An LSP transporting a Traffic Trunk
from that Class-Type can use that preemption priority as the setup
priority, the holding priority, or both.
TE LSP: Traffic Engineering Label Switched Path.
Traffic Trunk: An aggregation of traffic flows of the same class
(i.e., treated equivalently from the DS-TE perspective), which is
placed inside a TE LSP.
3. CLASSTYPE Object
The CLASSTYPE object is optional and is used to specify the Class-
Type of a TE LSP. This object is meaningful only within the path
computation request, and is ignored in the path reply message. If
the TE LSP for which the path is to be computed belongs to Class 0,
the
Sivabalan, et al. Standards Track [Page 3]
RFC 5455 DS Aware CT Object for PCEP March 2009
path computation request MUST NOT contain the CLASSTYPE object. This
allows backward compatibility with a PCE that does not support the
CLASSTYPE object.
3.1. Object Definition
The CLASSTYPE object contains a 32-bit word PCEP common object header
defined in [RFC5440] followed by another 32-bit word object body as
shown in Figure 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| PCEP common header |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved | CT |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: CLASSTYPE object format
The fields in the common object header are processed as specified in
[RFC5440]. The values of object class and object type are 22 and 1,
respectively. If included, the CLASSTYPE object must be taken into
account by the PCE. As such, the P flag MUST be set. The I flag is
ignored.
The CLASSTYPE object body contains the following fields:
CT: 3-bit field that indicates the Class-Type. Values allowed are 1,
2, ... , 7. The value of 0 is Reserved.
Reserved: 29-bit reserved field. It MUST be set to zero on
transmission and MUST be ignored on receipt.
3.2. Path Computation Request Message with CLASSTYPE Object
[RFC5440] specifies the order in which objects must be inserted in
the PCEP messages. This document specifies that the CLASSTYPE object
be inserted after the END-POINT objects as shown below:
Sivabalan, et al. Standards Track [Page 4]
RFC 5455 DS Aware CT Object for PCEP March 2009
The format of a Path Computation Request (PCReq) message is as
follows:
::=
[]
where:
::=[]
::=[]
::=
RFC, FYI, BCP