PCE Working Group D. Dhody Internet-Draft U. Palle Intended status: Standard Huawei Technologies India Pvt Ltd Expires: February 25, 2012 R. Casellas CTTC - Centre Tecnologic de Telecomunicacions de Catalunya August 24, 2011 Standard Representation Of Domain Sequence draft-dhody-pce-pcep-domain-sequence-01 Abstract The ability to compute shortest constrained Traffic Engineering Label Switched Paths (TE LSPs) in Multiprotocol Label Switching (MPLS) and Generalized MPLS (GMPLS) networks across multiple domains has been identified as a key requirement for P2P and P2MP scenarios. In this context, a domain is a collection of network elements within a common sphere of address management or path computational responsibility such as an IGP area or an Autonomous Systems. This document specifies a standard representation of domain sequence that can be utilized in all PCE deployment scenarios. Status of this Memo This Internet-Draft is submitted to IETF in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. 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." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on February 25, 2012. Dhody, et al. Expires February 25, 2012 [Page 1] Internet-Draft DOMAIN SEQ August 2011 Copyright Notice Copyright (c) 2010 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 (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. This Internet-Draft will expire on February 25, 2012. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Detail Description . . . . . . . . . . . . . . . . . . . . . . 4 3.1. Domains . . . . . . . . . . . . . . . . . . . . . . . . . 4 3.2. Standard Representation . . . . . . . . . . . . . . . . . 5 3.3. Deployment Scenarios . . . . . . . . . . . . . . . . . . . 6 3.3.1. Only AS . . . . . . . . . . . . . . . . . . . . . . . 6 3.3.2. Only Area . . . . . . . . . . . . . . . . . . . . . . 8 3.3.3. Mix of AS and Area . . . . . . . . . . . . . . . . . . 10 3.3.4. PCE serving multiple domains . . . . . . . . . . . . . 12 3.3.5. P2MP . . . . . . . . . . . . . . . . . . . . . . . . . 12 3.3.6. HPCE . . . . . . . . . . . . . . . . . . . . . . . . . 12 3.3.7. Domain Seq V/s PCE Seq . . . . . . . . . . . . . . . . 14 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 15 5. Security Considerations . . . . . . . . . . . . . . . . . . . 15 6. Manageability Considerations . . . . . . . . . . . . . . . . . 15 7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 15 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 15 8.1. Normative References . . . . . . . . . . . . . . . . . . . 15 8.2. Informative References . . . . . . . . . . . . . . . . . . 15 Dhody, et al. Expires February 25, 2012 [Page 2] Internet-Draft DOMAIN SEQ August 2011 1. Introduction RFC 5441 [A Backward-Recursive PCE-Based Computation (BRPC) Procedure to Compute Shortest Constrained Inter-Domain Traffic Engineering Label Switched Paths] mentions - "The sequence of domains to be traversed is either administratively predetermined or discovered by some means that is outside of the scope of this document. The PCC MAY indicate the sequence of domains to be traversed using the Include Route Object (IRO) defined in [RFC5440] so that it is available to all PCEs." This document proposes a standard way to represent domain sequence using IRO in various deployment scenarios. It further gives examples of various deployment scenario including P2P, P2MP and HPCE. The domain sequence (the set of domains traversed to reach the destination domain) is either administratively predetermined or discovered by some means (H-PCE) that is outside of the scope of this document. Here the focus is only on a standard representation of the domain sequence in all possible scenarios. 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. ABR: OSPF Area Border Router. Routers used to connect two IGP areas. AS: Autonomous System. ASBR: Autonomous System Boundary Router. BN: Boundary Node, Can be an ABR or ASBR. BRPC: Backward Recursive Path Computation Dhody, et al. Expires February 25, 2012 [Page 3] Internet-Draft DOMAIN SEQ August 2011 Domain: Any collection of network elements within a common sphere of address management or path computational responsibility. Examples of domains include Interior Gateway Protocol (IGP) areas and Autonomous Systems (ASs). Domain-Seq: The sequence of domains for a path. ERO: Explicit Route Object H-PCE: Hierarchical PCE IGP: Interior Gateway Protocol. Either of the two routing protocols, Open Shortest Path First (OSPF) or Intermediate System to Intermediate System (IS-IS). IRO: Include Route Object 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. P2MP: Point-to-Multipoint P2P: Point-to-Point TE LSP: Traffic Engineering Label Switched Path. 3. Detail Description 3.1. Domains A domain is any collection of network elements within a common sphere of address management or path computation responsibility. Examples of domains include IGP areas or Autonomous Systems (ASes). To uniquely identify a domain in the domain sequence both AS and Area-id is important. Dhody, et al. Expires February 25, 2012 [Page 4] Internet-Draft DOMAIN SEQ August 2011 3.2. Standard Representation The IRO (Include Route Object) is used to specify the domain sequence that the computed inter-domain path MUST traverse. IRO Object-Class is 10. IRO 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | // (Subobjects) // | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Sub-objects: The IRO is made of sub-objects. The following sub-object types are used. Type Sub-object 32 Autonomous system number (2 Byte) [RFC 3209] TBD Autonomous system number (4 Byte) TBD OSPF Area id TBD ISIS Area id [RFC 3209] define 2 octet AS number. To support 4 octet AS number [RFC4893] following subobject is defined: 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |L| Type | Length | Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | AS Id (4 bytes) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Since the length of Area-id is different for OSPF and ISIS, we propose different sub-objects. Dhody, et al. Expires February 25, 2012 [Page 5] Internet-Draft DOMAIN SEQ August 2011 For OSPF, the area-id is a 32 bit number. The Subobject looks 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |L| Type | Length | Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Area Id (4 bytes) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ The length if fixed. For ISIS, the area-id is of variable length and thus the length of the Subobject is variable. The Area-id is as described in ISIS by ISO standard. The Length MUST be at least 4, and MUST be a multiple of 4. 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |L| Type | Length | Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | // ISIS Area ID // | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 3.3. Deployment Scenarios 3.3.1. Only AS Considering each AS to be made of a single area, in this scenario the area MAY be skipped in the domain sequence. The domain sequence could be represented with just AS numbers. Dhody, et al. Expires February 25, 2012 [Page 6] Internet-Draft DOMAIN SEQ August 2011 +---------------------------------+ |AS 200 | | +------+ | | | | | +------------------------+ | | | +------+ | | AS 100 | | +------+ | | | | +------+ | | +------+ | | | | | +-+-----+-+ | +------+ | | | | | | | | | | +------+ | | +------+ | | +------+ | | +------+ | | | | | | | | | | | | | | | | | | +------+ | | +------+ | | | | | | +------+ | | +------+ | | | +-+-----+-+ | +------+ | | | | | | | | | | | | +------+ | | +------+ | | | | | | +------+ | | | | | | | | | | +------+ | | +------+ | | | | | | | | | | |PCE | | | |PCE | | | +------+ | | +------+ | | | | | +------------------------+ | | +---------------------------------+ Both AS are made of Area 0. Dhody, et al. Expires February 25, 2012 [Page 7] Internet-Draft DOMAIN SEQ August 2011 This could be represented as as: +---------+ +---------+ +---------+ |IRO | |Sub | |Sub | |Object | |Object As| |Object As| |Header | |100 | |200 | | | | | | | | | | | | | +---------+ +---------+ +---------+ +---------+ +---------+ +---------+ +---------+ +---------+ |IRO | |Sub | |Sub | |Sub | |Sub | |Object | |Object As| |Object | |Object As| |Object | |Header | |100 | |Area 0 | |200 | |Area 0 | | | | | | | | | | | | | | | | | | | | | +---------+ +---------+ +---------+ +---------+ +---------+ Area is optional and it MAY be skipped. PCE should be able to understand both notations. 3.3.2. Only Area Consider a case where both end of LSP belong to different area but within the same AS, this could be represented in domain sequence using the AREA sub-object. AS number MAYBE skipped. Dhody, et al. Expires February 25, 2012 [Page 8] Internet-Draft DOMAIN SEQ August 2011 +-------------------+ +-------------------+ | | | | | +--+ | | +--+ | | +--+ | | | | | | | | | | +--+ | | +--+ +--+ | | +--* + + | | | | | | +--+ | | *--+ + + | | | | | | +--+ | | +--+ | | | | | | |+--------------------------+| +--+ | | ++++ +-++ | | |||| +--+ | || | | Area 2 ++++ | | +-++ Area 4 | +-------------------+| +--+ |+-------------------+ | | | +--+ | | +--+ | | | | | | +--+ | | +--+ | | | | | | | | | | +--+ | | | | | | +--+ | +------------------+| |+--------------------+ | ++-+ +-++ | | || | | || | | ++-+ Area 0 +-++ | | |+--------------------------+| +--+ | | +--+ | | | | | | | | | | +--+ | | +--+ +--+ | | | | | | + + +--+ | | +--+ | | | | | | + + +--+ | | +--+ | | | | | | | | +--+ | | +--+ | | | | | | | | +--+ | | | | | | Area 1 | | Area 5 | +------------------+ +--------------------+ AS Number is 100. Dhody, et al. Expires February 25, 2012 [Page 9] Internet-Draft DOMAIN SEQ August 2011 This could be represented as as: +---------+ +---------+ +---------+ +---------+ |IRO | |Sub | |Sub | |Sub | |Object | |Object | |Object | |Object | |Header | |Area 2 | |Area 0 | |Area 4 | | | | | | | | | | | | | | | | | +---------+ +---------+ +---------+ +---------+ +---------+ +---------+ +---------+ +---------+ +---------+ |IRO | |Sub | |Sub | |Sub | |Sub | |Object | |Object As| |Object | |Object | |Object | |Header | |100 | |Area 2 | |Area 0 | |Area 4 | | | | | | | | | | | | | | | | | | | | | +---------+ +---------+ +---------+ +---------+ +---------+ AS is optional and it MAY be skipped. PCE should be able to understand both notations. 3.3.3. Mix of AS and Area In inter-AS case where an AS is further made up of multiple areas, both AS number and area should be a part of domain sequence. Dhody, et al. Expires February 25, 2012 [Page 10] Internet-Draft DOMAIN SEQ August 2011 | | +-------------+ +----------------+ | |Area 2 | |Area 4 | | | +--+| | +--+ | | | | || | | | | | | +--+ +--+| | +--+ +--+ | | | | | | | | | | | | *--+ | | +--+ | | | / +--+ | | +--+ | | |/ | | | | | | | | / +--+ | | +--+ +--+ | | /| +--+ |+--------------+| | | | |/ | | | ++-+ +-++ +--+ | +-------------+/ | +--+ || | | || | | /| | ++-+ +-++ | | +--*|| +-------------+| |+----------------+ | | ||| | +--+ | | +--+|| | | | | | +--+ || | +--+ | | | | || | | | +--+ || | | | || | +--+ | |+--+ || | | | | || | || | +--+ | |+--+ || | | | || | +--+ | | +--+ || +------------+ | | | |+----------------+ | | | || |Area 3 +-++ +--+ +-++ Area 5 | | +--+ || | | || | || | | || | +-++ +-++ | | +--+|| | +--+ | | Area 0 || +--+ | | | ||| | | | | +--------------+| | | | | +--*|| | +--+ | | +--+ | | \| | | | +--+ | |Area 1 |\ | +--+ | | +--+ | | | +-------------+|\ | | | | | | | +--+ | | \| +--+ +--+ | +--+ | | \ | | | | | |\ +--+ | +--+ | | | \ +--+ | | | | | | | \| | | | +--+ | | | *--+ | | | | | | | | | +------------+ +----------------+ | | As 100 | AS 200 | Dhody, et al. Expires February 25, 2012 [Page 11] Internet-Draft DOMAIN SEQ August 2011 The domain sequence can be carried in IRO as shown below: +-------+ +-------+ +-------+ +-------+ +-------+ +-------+ +-------+ |IRO | |Sub | |Sub | |Sub | |Sub | |Sub | |Sub | |Object | |Object | |Object | |Object | |Object | |Object | |Object | |Header | |As 100 | |Area 1 | |AS 200 | |Area 3 | |Area 0 | |Area 4 | | | | | | | | | | | | | | | +-------+ +-------+ +-------+ +-------+ +-------+ +-------+ +-------+ Combination of both AS and Area uniquely identify a domain in the domain sequence. 3.3.4. PCE serving multiple domains A single PCE maybe responsible for multiple domains; for example PCE function deployed on an ABR. Domain sequence should have no impact on this. PCE which can support 2 adjacent domains can internally handle this situation without any impact on the neighboring domains. 3.3.5. P2MP In case of P2MP the path domain tree is nothing but a series of Domain-Seq, as shown in the below figure: D1-D3-D6, D1-D3-D5 and D1-D2-D4. D1 / \ D2 D3 / / \ D4 D5 D6 The same domain sequence are carried in IRO as explained above. 3.3.6. HPCE Consider a case as shown below consisting of child and parent PCE. Dhody, et al. Expires February 25, 2012 [Page 12] Internet-Draft DOMAIN SEQ August 2011 +--------+ | Parent | | PCE | +--------+ +-------------------+ +-------------------+ | +--+ | | +--+ | | +--+ | | | | | | | | | | +--+ | | +--+ +--+ | | +--* + + | | | | | | +--+ | | *--+ + + | | | | | | +--+ | | +--+ | | | | | | |+--------------------------+| +--+ | | ++++ +-++ | | |||| +--+ | || | | Area 2 ++++ | | +-++ Area 4 | +-------------------+| +--+ |+-------------------+ | +--+ | | +--+ | | | | | | +--+ | | +--+ | | | | +--+ | | | | | | +--+ | +------------------+| |+--------------------+ | ++-+ +-++ | | || | | || | | ++-+ Area 0 +-++ | | |+--------------------------+| +--+ | | +--+ | | | | | | | | | | +--+ | | +--+ +--+ | | | | | | + + +--+ | | +--+ | | | | | | + + +--+ | | +--+ | | | | | | | | +--+ | | +--+ | | | | | | | | +--+ | | Area 1 | | Area 5 | +------------------+ +--------------------+ In HPCE implementation PCE(1) can request the parent PCE to determine the domain path and return in the PCRep in form of ERO. The Subobject would be AS and Area (OSPF/ISIS). So in this case, the Dhody, et al. Expires February 25, 2012 [Page 13] Internet-Draft DOMAIN SEQ August 2011 reply would carry the result as +---------+ +---------+ +---------+ +---------+ |ERO | |Sub | |Sub | |Sub | |Object | |Object | |Object | |Object | |Header | |Area 2 | |Area 0 | |Area 4 | | | | | | | | | | | | | | | | | +---------+ +---------+ +---------+ +---------+ +---------+ +---------+ +---------+ +---------+ +---------+ |ERO | |Sub | |Sub | |Sub | |Sub | |Object | |Object As| |Object | |Object | |Object | |Header | |100 | |Area 2 | |Area 0 | |Area 4 | | | | | | | | | | | | | | | | | | | | | +---------+ +---------+ +---------+ +---------+ +---------+ 3.3.7. Domain Seq V/s PCE Seq [PCE-P2MP-PROCEDURES] introduces the concept of PCE-Sequence, where a sequence of PCE based on the domain sequence should be decided and attached in the PCReq at the very beginning of path computation. It is much simpler and advantageous to carry only domain-sequence rather than PCE-Sequence. Advantages o All PCE must be aware of all other PCEs in all domain for PCE- Sequence. There is no clear method for this. In domain-sequence PCE should be aware of the domains and not all the PCEs serving the domain. PCE needs to be aware of the neighboring PCEs as done by discovery protocols. o There maybe multiple PCE in a domain, the selection of PCE shouldn't be made at the PCC/PCE(1). This decision is made only at the neighboring PCE which is completely aware of states of PCE via notification messages. o Domain sequence would be compatible to P2P inter-domain BRPC method as described in RFC 5441. There is no need for PCE-Sequence and it doesn't give any benefits over Domain Seq. Dhody, et al. Expires February 25, 2012 [Page 14] Internet-Draft DOMAIN SEQ August 2011 4. IANA Considerations IANA has defined a registry for OSPF and ISIS Area sub-object. Type Sub-object TBD AS Number (4 Byte) TBD OSPF Area id TBD ISIS Area id 5. Security Considerations This document specifies a standard representation of domain sequence, which is used in all inter-domain PCE scenarios as explained in other RFC and drafts. It does not introduce any new security considerations. 6. Manageability Considerations TBD 7. Acknowledgments We would like to thank Pradeep Shastry, Suresh babu, Quintin Zhao and Chen Huaimo for their useful comments and suggestions. 8. References 8.1. Normative References [ISO] "Intermediate System to Intermediate System Intra-Domain Routeing Exchange Protocol for use in Conjunction with the Protocol for Providing the Connectionless-mode Network Service" ISO/IEC 10589:2002 Second Edition [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", March 1997. 8.2. Informative References [PCE-HIERARCHY-FWK] King, D. and A. Farrel, "The Application of the Path Computation Element Architecture to the Determination of a Sequence of Domains in MPLS and GMPLS", September 2010. [PCE-P2MP-PROCEDURES] Zhao, Q., Ali, Z., Saad,, T., and D. King, "PCE-based Computation Procedure To Compute Shortest Constrained P2MP Inter-domain Traffic Engineering Label Switched Paths", January 2011. [RFC 3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V., and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP Tunnels", Dhody, et al. Expires February 25, 2012 [Page 15] Internet-Draft DOMAIN SEQ August 2011 December 2001. [RFC 4893] Vohra, Q. and E. Chen, "BGP Support for Four- octet AS Number Space", May 2007. [RFC5440] Ayyangar, A ., Farrel, A ., Oki, E., Atlas, A., Dolganow, A., Ikejiri, Y., Kumaki, K., Vasseur, J., and J. Roux, "Path Computation Element (PCE) communication Protocol (PCEP)", March 2009. [RFC5441] Vasseur, JP., Zhang, R., Bitar, N., and JL. Le Roux, "A Backward-Recursive PCE-Based Computation (BRPC) Procedure to Compute Shortest Constrained Inter-Domain Traffic Engineering Label Switched Paths", April 2009. Authors' Addresses Dhruv Dhody Huawei Technologies India Pvt Ltd Leela Palace Bangalore, Karnataka 560008 INDIA EMail: dhruvd@huawei.com Udayasree Palle Huawei Technologies India Pvt Ltd Leela Palace Bangalore, Karnataka 560008 INDIA EMail: udayasreepalle@huawei.com Ramon Casellas CTTC - Centre Tecnologic de Telecomunicacions de Catalunya Av. Carl Friedrich Gauss n7 Castelldefels, Barcelona 08860 SPAIN EMail: ramon.casellas@cttc.es Dhody, et al. Expires February 25, 2012 [Page 17]