PCE Working Group D. Dhody Internet-Draft U. Palle Intended status: Experimental Huawei Technologies India Pvt Expires: August 18, 2012 Ltd February 15, 2012 Supporting explicit-path per destination in Path Computation Element Communication Protocol (PCEP) P2MP Path Request Message. draft-dhody-pce-pcep-p2mp-per-destination-01 Abstract The ability to determine paths of point-to-multipoint (P2MP) Multiprotocol Label Switching (MPLS) and Generalized MPLS (GMPLS) Traffic Engineering Label Switched Paths (TE LSPs) is one the key requirements for Path Computation Element (PCE). [RFC6006] and [PCE-P2MP-PROCEDURES] describes these mechanisms for intra and inter domain environment. Explicit Path in this document refers to the configured list of network elements that MUST be traversed or MUST be excluded in the final path computation. This should not be confused with the RSVP terminology. Network elements can further be strict or loose hop. This document describes extensions to the PCE communication Protocol (PCEP) to define explicit-path per destination in P2MP context. 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 August 18, 2012. Copyright Notice Copyright (c) 2012 IETF Trust and the persons identified as the Dhody & Palle Expires August 18, 2012 [Page 1] Internet-Draft PER-DEST February 2012 document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of 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. Need to Define Explicit Path Per Destination . . . . . . . . . 4 3.1. Inter Domain P2MP Path Computation . . . . . . . . . . . . 4 3.2. Intra Domain P2MP Path Computation . . . . . . . . . . . . 4 3.3. Backward Compatibility . . . . . . . . . . . . . . . . . . 6 4. Detailed Description . . . . . . . . . . . . . . . . . . . . . 6 4.1. Objective . . . . . . . . . . . . . . . . . . . . . . . . 6 4.2. Request Message Format . . . . . . . . . . . . . . . . . . 7 4.3. Ordering Destinations in END-POINTS Objects . . . . . . . 7 4.3.1. Example . . . . . . . . . . . . . . . . . . . . . . . 8 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10 6. Security Considerations . . . . . . . . . . . . . . . . . . . 10 7. Manageability Considerations . . . . . . . . . . . . . . . . . 10 7.1. Control of Function and Policy . . . . . . . . . . . . . . 10 7.2. Information and Data Models . . . . . . . . . . . . . . . 11 7.3. Liveness Detection and Monitoring . . . . . . . . . . . . 11 7.4. Verify Correct Operations . . . . . . . . . . . . . . . . 11 7.5. Requirements On Other Protocols . . . . . . . . . . . . . 11 7.6. Impact On Network Operations . . . . . . . . . . . . . . . 11 8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 11 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 11 9.1. Normative References . . . . . . . . . . . . . . . . . . . 11 9.2. Informative References . . . . . . . . . . . . . . . . . . 11 Dhody & Palle Expires August 18, 2012 [Page 2] Internet-Draft PER-DEST February 2012 1. Introduction The Path Computation Element (PCE) architecture is defined in [RFC4655]. [RFC5862] mentions a P2MP PCE MUST be able to provide to the path computation a limiting set of nodes that can be used as branches for a P2MP path computation, or to provide a list of nodes that must not be used as branch points. This document mention the need to specify the branch points (or explict path) per destination. [RFC6006] describe a PCE-based path computation procedure to compute optimal constrained (G)MPLS P2MP TE LSPs. It also defines the format of path request message used in P2MP, which limits explicit path in form of IRO/XRO; to be applied to full P2MP tunnel and thus to only the common path to all leaves. This document describes the need for supporting explicit-path per destination in intra and inter-domain P2MP scenario. It further lists the path request format and mode of operations 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. Explicit-Path: Set of network elements configured by the administrator that MUST be traversed or MUST be excluded. IRO: Include Route Object. 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. P2MP: Point-to-Multipoint P2P: Point-to-Point Dhody & Palle Expires August 18, 2012 [Page 3] Internet-Draft PER-DEST February 2012 RRO: Record Route Object RSVP: Resource Reservation Protocol TE LSP: Traffic Engineering Label Switched Path. XRO: Exclude Route Object. 3. Need to Define Explicit Path Per Destination 3.1. Inter Domain P2MP Path Computation [PCE-P2MP-PROCEDURES] defines inter-domain P2MP path computation procedure, it is assumed that, the sequence of domains for a path (the path domain tree) will be known in advance. [DOMAIN-SEQ] describes the use of domain path tree in P2MP scenarios. In the Figure 1 below, the P2MP tree spans 6 domains, with D1 being the root domain. The corresponding domain sequences which are assumed known would be: D1-D3-D6, D1-D3-D5 and D1-D2-D4. D1 / \ D2 D3 / / \ D4 D5 D6 Figure 1: Domain Sequence Tree Since different destinations will have different domain sequence within the domain tree, it requires domain-sequence to be encoded in form of IRO to be attached per destination. It cannot be encoded for all destinations. So destination in domain D6, would use the domain-sequence: D1-D3-D6; destination in domain D5, would use the domain-sequence: D1-D3-D5; and destination in domain D4 would use the domain-sequence: D1-D2-D4. Thus domain-sequence encoded in form IRO Type domain-sequence (as per [DOMAIN-SEQ]) should be attached to destinations and not attached to full P2MP tree. 3.2. Intra Domain P2MP Path Computation Administrator at the source can exert stronger control by providing explicit path (include, exclude, loose etc) per destination. In Figure 2 shows the common path over which a common explicit path Dhody & Palle Expires August 18, 2012 [Page 4] Internet-Draft PER-DEST February 2012 in form of IRO and/or XRO can be set. +---+ | F | /*---+ // // // // +---+ +---+ +---+ +---* +---+ | A +--+ B +--+ C +--+ D +---------+ E | +---+ +---+ +---+ +---*\ +---+ | | \\ | | \\ | | \\ | | \\ |<-----common path------>| *---+ | | | G | | | +---+ Explicit Path Here Figure 2: Example But as shown in Figure 3, once new destinations are added and branch points are much nearer to ingress causing common path to reduce, the administrator would not be able to apply the explicit path as before. Dhody & Palle Expires August 18, 2012 [Page 5] Internet-Draft PER-DEST February 2012 +---+ +---+ | H | | F | *---+ /*---+ // // // // / // // // +---+ +---* +---+ +---* +---+ | A +--+ B +--+ C +--+ D +---------+ E | +---+ +---+ +---* +---*\ +---+ | | \\ \\ | | \\ \\ |<-------->| \\ \\ | Common | \\ \\ | path | *---+ *---+ | | | I | | G | | | +---+ +---+ | | | | Figure 3: Example 3.3. Backward Compatibility Basic MPLS TE P2MP Tunnel configurations for various operators support the configuration of explicit-path per destination. In some operators where preconfigured path must be setup, during configurations the path to each destination is configured as an explicit path and attached to each destination. It makes sense to apply explict path per destination instead of the full P2MP tree. 4. Detailed Description 4.1. Objective [RFC6006] defines Request Message Format and Objects, along with . This section introduce the concept of , and which are added to the to support 'per destination'. Use of , to carry explicit-path per destination. Use of to carry domain-sequence per destination in inter- domain scenario. Use of to carry metric value of each calculated path Dhody & Palle Expires August 18, 2012 [Page 6] Internet-Draft PER-DEST February 2012 encoded in . 4.2. Request Message Format To carry explicit path for each destination, objects need to be ordered and grouped in a way such that IRO object, XRO object, RRO object and METRIC object can be associated with each destination. The format of PCReq message is modified as follows: ::= where: ::= [] [] [] [] [] [] where: ::= [] [] [] [] [] ::=[][] ::=[] ::=[] ::=[] From [RFC6006] usage of is changed to in this document. Note that the new format is backward compatible to [RFC6006] format. 4.3. Ordering Destinations in END-POINTS Objects Multiple destinations are encoded into a single ENDPOINTS object, Each Endpoint maybe followed by multiple lists of IROs, XROs, RROs or METRICs. The first object would belong to the first Dhody & Palle Expires August 18, 2012 [Page 7] Internet-Draft PER-DEST February 2012 destination, the second object to the second destination and hence forth. The first object would belong to the first destination, the second object to the second destination and hence forth... Note that a destination (P2MP tree leaf) MAY have o both and o only o only o No explicit path To maintain the ordering between the destination and objects in the list, there MAYBE a need to divide a set of destinations into multiple ENDPOINTS, this explained in below example. 4.3.1. Example Destination 1 has include IRO1 and exclude XRO1 Destination 2 has only include IRO2 Destination 3 has only exclude XRO3 Destination 4 has only exclude XRO4 Destination 5 has none Here if we try to encode all destinations in one and objects in list, we will not map XRO3 to destination 3, the rule is to map sequentially and thus XRO3 will belong to destination 2. To avoid this we must break the set of destinations into two sets as shown below Dhody & Palle Expires August 18, 2012 [Page 8] Internet-Draft PER-DEST February 2012 +-----------------------------+ | Leaf Type | +-----------------------------+ | Source IP | +-----------------------------+ +------> | Destination 1 | | +-----------------------------+ | +-> | Destination 2 | | * +-----------------------------+ | * | Destination 5 | | * +-----------------------------+ | * | * +-----------------------------+ +----*-> | IRO1 | | * +-----------------------------+ | * | HOPI 1-1 | | * +-----------------------------+ | * | .... | | * +-----------------------------+ with 2 IRO1, IRO2 | +-> | IRO2 | | +-----------------------------+ | | HOPI 2-1 | | +-----------------------------+ | | .... | | +-----------------------------+ | | +-----------------------------+ +-----> | XRO1 | +-----------------------------+ | HOPX 1-1 | with 1 XRO1 +-----------------------------+ | .... | +-----------------------------+ ENDPOINT1 carries destination 1, 2 and 5 and corresponding and . Here Destination 1 has IRO1 and XRO1; Destination 2 has IRO2; and Destination 5 has none. Dhody & Palle Expires August 18, 2012 [Page 9] Internet-Draft PER-DEST February 2012 +-----------------------------+ | Leaf Type | +-----------------------------+ | Source IP | +-----------------------------+ +------> | Destination 3 | | +-----------------------------+ | +-> | Destination 4 | | * +-----------------------------+ | * | * +-----------------------------+ +----*-> | XRO3 | * +-----------------------------+ * | HOPX 3-1 | * +-----------------------------+ * | .... | * +-----------------------------+ with 2 XRO3, XRO4 +-> | XRO4 | +-----------------------------+ | HOPX 4-1 | +-----------------------------+ | .... | +-----------------------------+ ENDPOINT2 carries destination 3 and 4 and corresponding only. Here destination 3 maps to XRO3 and Destination 4 to XRO4. 5. IANA Considerations TBD 6. Security Considerations PCEP security mechanisms as described in [RFC6006] and [PCE-P2MP-PROCEDURES] are applicable for this document. This document does not add any new security threat. 7. Manageability Considerations 7.1. Control of Function and Policy Mechanisms defined in this document do not add any new control function/policy requirements in addition to those already listed in [RFC6006]. Dhody & Palle Expires August 18, 2012 [Page 10] Internet-Draft PER-DEST February 2012 7.2. Information and Data Models Mechanisms defined in this document do not imply any new MIB requirements in addition to those already listed in [PCE-P2MP-MIB]. 7.3. 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 [RFC6006]. 7.4. Verify Correct Operations Mechanisms defined in this document do not imply any new operation verification requirements in addition to those already listed in [RFC6006]. 7.5. Requirements On Other Protocols Mechanisms defined in this document do not imply any requirements on other protocols in addition to those already listed in [RFC6006]. 7.6. Impact On Network Operations Mechanisms defined in this document do not have any impact on network operations in addition to those already listed in [RFC6006]. 8. Acknowledgments We would like to thank Pradeep Shastry, Suresh babu, Quintin Zhao, Daniel King and Chen Huaimo for their useful comments and suggestions. 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. 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 Dhody & Palle Expires August 18, 2012 [Page 11] Internet-Draft PER-DEST February 2012 Element (PCE) Communication Protocol Generic Requirements", RFC 4657, September 2006. [RFC5440] Vasseur, JP. and JL. Le Roux, "Path Computation Element (PCE) Communication Protocol (PCEP)", RFC 5440, March 2009. [RFC5862] Yasukawa, S. and A. Farrel, "Path Computation Clients (PCC) - Path Computation Element (PCE) Requirements for Point-to-Multipoint MPLS-TE", RFC 5862, June 2010. [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. [PCE-P2MP-PROCEDURES] Zhao, Q., Dhody, D., Ali, Z., Saad,, T., Sivabalan,, S., and R. Casellas, "PCE-based Computation Procedure To Compute Shortest Constrained P2MP Inter-domain Traffic Engineering Label Switched Paths (draft-ietf- pce-pcep-inter-domain-p2mp-procedures-02)", February 2012. [PCE-P2MP-MIB] Zhao, Q., Dhody, D., Palle, U., and D. King, "Management Information Base for the PCE Communications Protocol (PCEP) When Requesting Point-to-Multipoint Services (draft-zhao-pce-pcep-p2mp-mib-03)", September 2011. [DOMAIN-SEQ] Dhody, D., Palle, U., and R. Casellas, "Standard Representation Of Domain Sequence (draft-dhody-pce-pcep-domain-sequence-02)", February 2012. Dhody & Palle Expires August 18, 2012 [Page 12] Internet-Draft PER-DEST February 2012 Authors' Addresses Dhruv Dhody Huawei Technologies India Pvt Ltd Leela Palace Bangalore, Karnataka 560008 INDIA EMail: dhruv.dhody@huawei.com Udayasree Palle Huawei Technologies India Pvt Ltd Leela Palace Bangalore, Karnataka 560008 INDIA EMail: udayasree.palle@huawei.com Dhody & Palle Expires August 18, 2012 [Page 13]