PCE Working Group F. Zhang Internet-Draft Q. Zhao Intended status: Informational Huawei Technologies Expires: April 13, 2012 O. Gonzalez de Dios Telefonica I+D R. Casellas CTTC D. King Old Dog Consulting October 13, 2011 Extensions to Path Computation Element Communication Protocol (PCEP) for Hierarchical Path Computation Elements (PCE) draft-zhang-pce-hierarchy-extensions-01 Abstract The hierarchical Path Computation Element (PCE) architecture, defined in the companion framework document [I-D.ietf-pce-hierarchy-fwk], allows the selection of an optimum domain sequence and the optimum end-to-end path, to be derived through the use of a hierarchical relationship between domains. This document defines the Path Computation Element Protocol (PCEP) extensions for the purpose of implementing hierarchical PCE procedures which are described the aforementioned document. 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 April 13, 2012. Copyright Notice Copyright (c) 2011 IETF Trust and the persons identified as the Zhang, et al. Expires April 13, 2012 [Page 1] Internet-Draft PCEP Extensions for H-PCE October 2011 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 . . . . . . . . . . . . . . . . . . . . . . . . . 4 1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4 1.2. Requirements Language . . . . . . . . . . . . . . . . . . 4 2. PCEP Extension Requirements . . . . . . . . . . . . . . . . . 4 2.1. Building of parent topology . . . . . . . . . . . . . . . 5 2.2. New Objective Functions . . . . . . . . . . . . . . . . . 5 2.3. PCEP Request Qualifiers . . . . . . . . . . . . . . . . . 6 2.4. Discovery Between Parent and Child PCEs . . . . . . . . . 6 2.4.1. Parent PCE Capability Discovery . . . . . . . . . . . 6 2.4.2. PCE Domain and PCE ID Discovery . . . . . . . . . . . 7 2.5. Domain Connectivity Information Collection . . . . . . . . 7 2.6. Error Case Handling . . . . . . . . . . . . . . . . . . . 8 3. PCEP Extensions . . . . . . . . . . . . . . . . . . . . . . . 8 3.1. Extensions to OPEN object . . . . . . . . . . . . . . . . 8 3.1.1. OF Codes . . . . . . . . . . . . . . . . . . . . . . . 8 3.1.2. OPEN Object Flags . . . . . . . . . . . . . . . . . . 8 3.1.3. Domain-ID TLV . . . . . . . . . . . . . . . . . . . . 9 3.1.4. PCE-ID TLV . . . . . . . . . . . . . . . . . . . . . . 10 3.1.5. Procedures . . . . . . . . . . . . . . . . . . . . . . 10 3.2. Extensions to RP object . . . . . . . . . . . . . . . . . 11 3.2.1. RP Object Flags . . . . . . . . . . . . . . . . . . . 11 3.2.2. Domain-ID TLV . . . . . . . . . . . . . . . . . . . . 11 3.2.3. Procedures . . . . . . . . . . . . . . . . . . . . . . 11 3.3. Extensions to NOTIFICATION object . . . . . . . . . . . . 12 3.3.1. Notification Types . . . . . . . . . . . . . . . . . . 12 3.3.2. Inter-domain Link TLV . . . . . . . . . . . . . . . . 12 3.3.3. Inter-domain Node TLV . . . . . . . . . . . . . . . . 13 3.3.4. Domain-ID TLV . . . . . . . . . . . . . . . . . . . . 15 3.3.5. PCE-ID TLV . . . . . . . . . . . . . . . . . . . . . . 15 3.3.6. Procedures . . . . . . . . . . . . . . . . . . . . . . 15 3.4. Extensions to PCEP-ERROR object . . . . . . . . . . . . . 15 3.4.1. Hierarchy PCE Error-Type . . . . . . . . . . . . . . . 15 3.4.2. Procedures . . . . . . . . . . . . . . . . . . . . . . 16 Zhang, et al. Expires April 13, 2012 [Page 2] Internet-Draft PCEP Extensions for H-PCE October 2011 4. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 16 5. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 16 6. Manageability Considerations . . . . . . . . . . . . . . . . . 16 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16 7.1. Objective Function (OF) codes . . . . . . . . . . . . . . 16 7.2. OPEN Object Flags . . . . . . . . . . . . . . . . . . . . 16 7.3. RP Object Flags . . . . . . . . . . . . . . . . . . . . . 16 7.4. PCEP TLVs . . . . . . . . . . . . . . . . . . . . . . . . 17 7.5. PCEP NOTIFICATION types . . . . . . . . . . . . . . . . . 17 7.6. PCEP PCEP-ERROR types . . . . . . . . . . . . . . . . . . 17 8. Security Considerations . . . . . . . . . . . . . . . . . . . 17 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 17 9.1. Normative References . . . . . . . . . . . . . . . . . . . 17 9.2. Informative References . . . . . . . . . . . . . . . . . . 18 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 18 Zhang, et al. Expires April 13, 2012 [Page 3] Internet-Draft PCEP Extensions for H-PCE October 2011 1. Introduction [I-D.ietf-pce-hierarchy-fwk] describes a hierarchical PCE architecture which can be used for computing end-to-end paths for inter-domain MPLS Traffic Engineering (TE) and GMPLS Label Switched Paths (LSPs). In the hierarchical PCE architecture, the parent PCE can compute a multi-domain path based on the domain connectivity information and each child PCE is able to compute the intra-domain path based on its domain topology information. The end-to-end domain path computing procedures can be abstracted as follows: o A path computation client (PCC) requests its own child PCE the computation of an inter-domain path. o The child PCE forwards the request to the parent PCE. o The parent PCE computes one or multiple domain paths from the ingress domain to the egress domain. o The parent PCE sends the intra-domain path computation requests (between the domain border nodes) to the child PCEs which are responsible for the domains along the domain path(s). o The child PCEs return the intra-domain paths to the parent PCE. o The parent PCE constructs the end-to-end inter-domain path based on the intra-domain paths and returns the inter-domain path to the child PCE. o The child PCE forwards the inter-domain path to the PCC. This document defines the PCEP extensions for the purpose of implementing hierarchical PCE procedures, which are described in [I-D.ietf-pce-hierarchy-fwk]. The document also uses a number of editor notes to describe options and alternative solutions. These options and notes will be removed before publication. 1.1. Terminology This document uses the terminology defined in [RFC4655], [RFC5440] and [I-D.ietf-pce-hierarchy-fwk]. 1.2. 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. PCEP Extension Requirements Zhang, et al. Expires April 13, 2012 [Page 4] Internet-Draft PCEP Extensions for H-PCE October 2011 2.1. Building of parent topology As stated in section 5.4 of [I-D.ietf-pce-hierarchy-fwk] a parent PCE maintains a domain topology map and may contain nodes and links on its own right, maintaining a traffic engineering database (TED) for the parent domain. The parent PCE TED may be configured or learnt by the child PCEs. Editors note. A child PCE could forward the topology within PCNtf messages or any other mechanisms, without an IGP adjacency. Further discussion of the discovery mechanism and scope will be discussed in later versions of this document. 2.2. New Objective Functions For inter-domain path computation, there are three new objective functions which are defined in section 1.3.1 of [I-D.ietf-pce-hierarchy-fwk]. o Minimize the number of boundary nodes used. o Limit the number of domains crossed. o Disallow domain re-entry. During the PCEP session establishment procedure, the parent PCE needs to be capable of indicating the objective functions (OF) capability in the Open message. This information can be, in turn, announced by child PCEs and used for selecting the PCE when a PCC want a path that satisfies a certain inter-domain objective function. When a PCC requests a PCE to compute an inter-domain path, the PCC needs also to be capable of indicating the new objective functions for inter-domain path. Note that a given PCE may act as a regular PCE and as a parent PCE. For the reasons described above, new OF codes need to be defined for the new inter-domain objective functions. Then the PCE can notify its new inter-domain objective functions to the PCC by carrying them in the OF-list TLV which is carried in the OPEN object. The PCC can specify which objective function code to use, which is carried in the OF object when requesting a PCE to compute an inter-domain path. The proposed solutions may need to differentiate between the OF code that is requested at the parent level and the OF code that is requested at the intra-domain (child) level. A parent PCE needs to be able to insure homogeneity when applying OF codes for the intra-domain requests. Zhang, et al. Expires April 13, 2012 [Page 5] Internet-Draft PCEP Extensions for H-PCE October 2011 2.3. PCEP Request Qualifiers As described in section 5.8.1 of [I-D.ietf-pce-hierarchy-fwk], the H-PCE architecture will introduce new request qualifications as follows: o It MUST be possible for a child PCE to indicate that a request it sends to a parent PCE should be satisfied by a domain sequence only, that is, not by a full end-to-end path. This allows the child PCE to initiate a per-domain [RFC5152] or a backward recursive path computation (BRPC) [RFC5441]. o A parent PCE needs to be able to ask a child PCE whether a particular node address (the destination of an end-to-end path) is present in the domain that the child PCE serves. o As stated in [I-D.ietf-pce-hierarchy-fwk], section 5.5, if a PCC knows the egress domain, it can suppy this information as the path computation request. It SHOULD be possible to specify the destination domain information in a PCEP request, if it is known. To meet the above requirements, the PCEP PCReq message should be extended. 2.4. Discovery Between Parent and Child PCEs In the H-PCE architecture, the parent PCE does not need to be aware of each child domain topology. Therefore, it is possible that the parent PCE does not join the IGP instance of the child PCE domain, i.e. there is no IGP discovery mechanism between the parent PCE and child PCE. Therefore there must be a discovery mechanism for basic PCE information between the parent and child PCEs. In this case, PCEP needs to provide discovery mechanisms that do not rely on IGP announcement/discovery procedures. A simple discovery mechanism relies on the static configuration / provisioning of the parent PCE id and address, which is configured at each child PCE. 2.4.1. Parent PCE Capability Discovery As described in [I-D.ietf-pce-hierarchy-fwk], during the PCEP session establishment procedure, the child PCE needs to be capable of indicating to the parent PCE whether it requests the parent PCE capability or not. The parent PCE needs also to be capable of indicating whether its parent capability can be provided to the child PCE or not. Zhang, et al. Expires April 13, 2012 [Page 6] Internet-Draft PCEP Extensions for H-PCE October 2011 2.4.2. PCE Domain and PCE ID Discovery A PCE domain is a single domain with an associated PCE. it is possible for a PCE to manage multiple domains. The PCE domain may be an IGP area or AS. The PCE ID is an IPv4 and/or IPv6 address that is used to reach the parent/child PCE. It is RECOMMENDED to use an address that is always reachable if there is any connectivity to the PCE. The PCE ID information and PCE domain identifiers may be provided during the PCEP session establishment procedure or the domain connectivity information collection procedure. 2.5. Domain Connectivity Information Collection As described in [I-D.ietf-pce-hierarchy-fwk], the parent PCE builds the domain topology map either from configuration or from information received from each child PCE. A child PCE may report its neighbor domain connectivity to its parent PCE. It is reasonable to use PCEP PCNtf message to do this procedure. If an IGP adjacency is established between parent and children, it could be used for this purpose. There are two types of domain border for providing the domain connectivity information: o Domain border is a TE link, e.g. the inter-AS TE link which connects two ASs. o Domain border is a node, e.g. the IGP ABR which connects two IGP areas. For the inter-AS TE links, the following information needs to be notified to the parent PCE: o Identifier of advertising child PCE. o Identifier of PCE's domain. o Identifier of the link. o TE properties of the link (metrics, bandwidth). o Other properties of the link (technology-specific). o Identifier of link end-points. o Identifier of adjacent domain. For the ABR, the following information needs to be notified to the parent PCE: Zhang, et al. Expires April 13, 2012 [Page 7] Internet-Draft PCEP Extensions for H-PCE October 2011 o Identifier of the ABR. o Identifier of the IGP Area IDs. 2.6. Error Case Handling A PCE that is capable of acting as a parent PCE might not be configured or willing to act as the parent for a specific child PCE. This fact could be determined when the child sends a PCReq that requires parental activity (such as querying other child PCEs), and could result in a negative response in a PCEP Error (PCErr) message and indicate the hierarchy PCE error types. 3. PCEP Extensions 3.1. Extensions to OPEN object 3.1.1. OF Codes There are three new OF codes defined here for H-PCE: o MBN * Name: Minimize the number of Boundary Nodes used * Objective Function Code: (to be assigned by IANA, recommended 11) * Description: Find a path P such that passes through the least boundary nodes. o MTD * Name: Minimize the number of Transit Domains * Objective Function Code: (to be assigned by IANA, recommended 12) * Description: Find a path P such that passes through the least transit domains. o DDR * Name: Disallow Domain Re-entry (DDR) * Objective Function Code: (to be assigned by IANA, recommended 13) * Description: Find a path P such that does not entry a domain more than once. 3.1.2. OPEN Object Flags There are two OPEN object flags defined here for H-PCE: o Parent PCE request bit (to be assigned by IANA, recommended bit 0): if set it means the child PCE wishes to use the peer PCE as a parent PCE. Zhang, et al. Expires April 13, 2012 [Page 8] Internet-Draft PCEP Extensions for H-PCE October 2011 o Parent PCE indication bit (to be assigned by IANA, recommended bit 1): if set it means the PCE can be used as a parent PCE by the peer PCE. o Editors Note. It is possible that a parent PCE will also act as a child PCE. 3.1.3. Domain-ID TLV The type of Domain-ID TLV is to be assigned by IANA (recommended 7). The length is 8 octets. The format of this TLV is defined below: 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Domain Type | Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Domain ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 1: Domain-ID TLV Domain Type (8 bits): Indicates the domain type. There are two types of domain defined currently: o Type=1: the Domain ID field carries an IGP Area ID. o Type=2: the Domain ID field carries an AS number. Domain ID (32 bits): Indicates an IGP Area ID or AS number. An AS number may be 2 or 4 bytes long. For 2-byte AS numbers, the AS value is left-padded with 0. Editor's note: it may be necessary to support 64 bit domain IDs. Editor's note: draft-dhody-pce-pcep-domain-sequence, section 3.2 deals with the encoding of domain sequences, using ERO-subobjects. Work is ongoing to define domain identifiers for OSPF-TE areas, IS-IS area (which are variable sized), 2-byte and 4-byte AS number, and any other domain that may be defined in the future. It uses RSVP-TE subobject discriminators, rather than new type 1/ type 2. A domain sequence may be encoded as a route object. The "VALUE" part of the TLV could follow common RSVP-TE subobject format: Zhang, et al. Expires April 13, 2012 [Page 9] Internet-Draft PCEP Extensions for H-PCE October 2011 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |0| Type | Length | Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | AS Id (4 bytes) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |0| Type | Length | AS Id (2 bytes) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 2: Alternative Domain-ID TLV 3.1.4. PCE-ID TLV The type of PCE-ID TLV is to be assigned by IANA (recommended 8). The length is 8. The format of this TLV is defined below: 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Address Type | Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | // PCE IP Address // | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 3: PCE-ID TLV Address Type (16 bits): Indicates the address type of PCE IP Address. 1 means IPv4 address type, 2 means IPv6 address type. PCE IP Address: Indicates the reachable address of a PCE. Editor's note: RFC5886 already defines the PCE-ID object. If a semantically equivalent PCE-ID TLV is needed (to avoid modifying message grammars to include the object), it can align with the PCEP object: n any case, the length (4 / 16 bytes) can be used to know whether it is an IPv4 or an IPv6 PCE, the address type is not needed. 3.1.5. Procedures The OF codes defined in this document can be carried in the OF-list TLV of the OPEN object. If the OF-list TLV carries the OF codes, it Zhang, et al. Expires April 13, 2012 [Page 10] Internet-Draft PCEP Extensions for H-PCE October 2011 means that the PCE is capable of implementing the corresponding objective functions. This information can be used for selecting a proper parent PCE when a child PCE wants to get a path that satisfies a certain objective function. If a child PCE wants to use the peer PCE as a parent, it can set the parent PCE request bit in the OPEN object carried in the Open message during the PCEP session creation procedure. If the peer PCE does not want to provide the parent function to the child PCE, it must send a PCErr message to the child PCE and clear the parent PCE indication bit in the OPEN object. If the parent PCE can provide the parent function to the peer PCE, it may set the parent PCE indication bit in the OPEN object carried in the Open message during the PCEP session creation procedure. The PCE may also report its PCE ID and list of domain ID to the peer PCE by specifying them in the PCE-ID TLV and List of Domain-ID TLVs in the OPEN object carried in the Open message during the PCEP session creation procedure. 3.2. Extensions to RP object 3.2.1. RP Object Flags o Domain Path Request bit (to be assigned by IANA, recommended bit 17): if set it means the child PCE wishes to get the domain sequence. o Destination Domain Query bit (to be assigned by IANA, recommended bit 16): if set it means the parent PCE wishes to get the destination domain ID. 3.2.2. Domain-ID TLV The format of this TLV is defined in section Section 3.1.3. This TLV can be carried in an OPEN object to indicate a (list of) managed domains, or carried in a RP object to indicate the destination domain ID when a child PCE responds to the parent PCE's destination domain query by a PCRep message. Editors note. In some cases, the Parent PCE may need to allocate a node which is not necessarily the destination node. 3.2.3. Procedures If a child PCE only wants to get the domain sequence for a multi- domain path computation from a parent PCE, it can set the Domain Path Request bit in the RP object carried in a PCReq message. The parent Zhang, et al. Expires April 13, 2012 [Page 11] Internet-Draft PCEP Extensions for H-PCE October 2011 PCE which receives the PCReq message tries to compute a domain sequence for it. If the domain path computation succeeds the parent PCE sends a PCRep message which carries the domain sequence in the ERO to the child PCE . The domain sequence is specified as AS or AREA ERO sub-objects (type 32 for AS [RFC3209] or a to-be-defined IGP arrea type). Otherwise it sends a PCReq message which carries the NO-PATH object to the child PCE. The parent PCE can set the Destination Domain Query bit in a PCReq message to query the destination (which is specified in the END- POINTS objects) domain ID from a child PCE. If the child PCE knows the destination(s) domain ID, it sends a PCRep message to the parent PCE and specifies the domain ID in the Domain-ID TLV which is carried in the RP object. Otherwise it sends a PCRep message with a NO-PATH object to the parent PCE. 3.3. Extensions to NOTIFICATION object Because there will not be too many PCEP sessions between the child PCE(s) and parent PCE, it is recommended that the PCEP sessions between them keeping alive all the time . Then the child PCE can report all of the domain connectivity information to the parent PCE when the PCEP session is established successfully. It can also notify the parent PCE to update or delete the domain connectivity information when it detects the changes. 3.3.1. Notification Types There is a new notification type defined in this document: o Domain Connectivity Information notification-type (to be assigned by IANA, recommended 3). * Notification-value=0: sent from the parent to the child to query all of the domain connectivity information maintained by the child PCE. * Notification-value=1: sent from the child to the parent to update the domain connectivity information maintained by the child PCE. * Notification-value=2: sent from the child to the parent to delete the domain connectivity information maintained by the child PCE. 3.3.2. Inter-domain Link TLV IGP in each neighbor domain can advertise its inter-domain TE link capabilities [RFC5316], [RFC5392]. This information can be collected by the child PCEs and forwarded to the parent PCE. PCEP Inter-domain Link TLV is used for carrying the inter-domain TE link attributes for Zhang, et al. Expires April 13, 2012 [Page 12] Internet-Draft PCEP Extensions for H-PCE October 2011 this purpose. Each Inter-domain Link TLV can carry the attributes of one inter-domain link at the most. The type of Inter-domain Link TLV is to be assigned by IANA (recommended 9). The length is variable. The format of this TLV is defined below: 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Advertise Router ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | // sub-TLVS // | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 4: Inter-domain Link TLV Editor's note: evaluate other possibilities regarding the wrapping and encoding (LSAs / LSUs). Other fields may be needed, such as LSA age (max age methods can be used to "withdraw" or remove a link). Sub-TLVs may need to be defined in the context of a Link TLV (top TLV). Advertise Router ID (32 bits): indicates the router ID which advertises the TE LSA or LSP. Sub-TLVs: the OSPF sub-TLVs for a TE link which defined in [RFC5392] and other associated OSPF RFCs. It is noted that if the IGP is IS-IS for the child domain the sub-TLVs must be converted to the OSPF sub- TLVs format when sending this information to the parent PCE through PCEP PCNtf message. Each inter-domain link is identified by the combination of advertise router ID and the link local IP address or link local unnumbered identifier. The PCNtf message which is used for notifying the parent PCE to update or delete a inter-domain link must contain the information identifies a TE link exclusively. 3.3.3. Inter-domain Node TLV The Inter-domain Node TLV carries only the two adjacent domain ID and the router (IGP ABR) ID. The type of Inter-domain Node Information TLV is to be assigned by IANA (recommended 10). The length is variable . The format of this TLV is defined below: Zhang, et al. Expires April 13, 2012 [Page 13] Internet-Draft PCEP Extensions for H-PCE October 2011 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | ABR ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Area ID1 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Area ID2 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 5: Inter-domain Node TLV ABR ID (32 bits): indicates the domain border router ID. Area ID1 & Area ID2 (32 bits): indicates the two neighbor area IDs. Editor's note (1): a node may be an inter-domain node for more than just 2 areas, the encoding is wrong, unless we explicitly state that this TLV can be repeated and we give an example. Alternatively, we can use the generic concept of "domain id" as introduced earlier, to avoid the restriction of 4 byte areas only. Editor's note (2): do we homogenize so we also have a Advertising Router ID? would it be different from the ABR id? 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Advertise Router ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | ABR ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |0| Type | Length | Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | IS/IS area 1 ... | .. | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |0| Type | Length | Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | IS/IS area 2 ... | .. | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 6: Alternative Inter-domain Node TLV Zhang, et al. Expires April 13, 2012 [Page 14] Internet-Draft PCEP Extensions for H-PCE October 2011 3.3.4. Domain-ID TLV The format of this TLV is defined in section Section 3.1.3. This TLV can be carried in a NOTIFICATION object to indicate the domain ID of the PCE who sends the PCNtf message. Editors note. A PCE may be responsible for several domains, it may be beneficial to use a list of TLVs. 3.3.5. PCE-ID TLV The format of this TLV is defined in section Section 3.1.4. This TLV can be carried in a NOTIFICATION object to indicate the PCE ID of the PCE who sends the PCNtf message. 3.3.6. Procedures When a parent PCE establishes a PCEP session with a child PCE successfully, the parent PCE may request the child PCE to report the domain connectivity information. This procedure can be done by sending a PCNtf message from the parent to the child, setting the notification-type to 3 and notification-value to 0 in the NOTIFICATION object. When a child PCE receives the PCNtf message, it may send all of the domain connectivity information to the parent PCE by the PCNtf message(s). The notification-type is 3 and notification-value is 1 in the NOTIFICATION object. The NOTIFICATION object may carry the inter-domain link TLV and inter-domain node TLV to describe the inter-domain connectivity information. It is noted that if the child PCE dose not support this function, it will ignore the received PCNtf message and the parent PCE will not receive the response. The child PCE can also update the domain connectivity information by re-sending the PCNtf message(s) with the newly information. When the child PCE detects a deletion of domain connectivity (e.g., the inter-domain link TLV is aged out), it must notify the parent PCE to delete the inter-domain link by sending the PCNtf message. The notification-type is 3 and notification-value is 2 in the NOTIFICATION object. 3.4. Extensions to PCEP-ERROR object 3.4.1. Hierarchy PCE Error-Type A new PCEP Error-Type is allocated for hierarchy PCE (to be assigned by IANA, recommended 19): Zhang, et al. Expires April 13, 2012 [Page 15] Internet-Draft PCEP Extensions for H-PCE October 2011 +------------+------------------------------------------------------+ | Error-Type | Meaning | +------------+------------------------------------------------------+ | 19 | H-PCE error Error-value=1: parent PCE capability | | | cannot be provided | +------------+------------------------------------------------------+ Table 1: H-PCE error table 3.4.2. Procedures When a specific child PCE sends a PCReq to a peer PCE that requires parental activity and the peer PCE does not want to act as the parent for it, the peer PCE should send a PCErr message to the child PCE and specify the error-type (IANA) and error-value (1) in the PCEP-ERROR object. 4. Acknowledgements 5. Contributors TBD. 6. Manageability Considerations TBD. 7. IANA Considerations As per RFC 5226 [RFC5226], IANA is requested to create/update the following registries 7.1. Objective Function (OF) codes Value Meaning Reference 11 MBN This document 12 MTD This document 13 DDR This document 7.2. OPEN Object Flags 7.3. RP Object Flags Zhang, et al. Expires April 13, 2012 [Page 16] Internet-Draft PCEP Extensions for H-PCE October 2011 7.4. PCEP TLVs Value Meaning Reference x Interdomain Link TLV This document (section Section 3.3.2) x Interdomain Node TLV This document (section Section 3.3.3) 7.5. PCEP NOTIFICATION types Type Value Meaning P2C Notification 1 2 3 C2P Notification 1 2 3 7.6. PCEP PCEP-ERROR types Type Value Meaning H-PCE Error 19 1 parent PCE capability cannot be provided 2 TBD 3 TBD 8. Security Considerations TBD. 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. [RFC5152] Vasseur, JP., Ayyangar, A., and R. Zhang, "A Per-Domain Path Computation Method for Establishing Inter-Domain Traffic Engineering (TE) Label Switched Paths (LSPs)", RFC 5152, February 2008. [RFC5440] Vasseur, JP. and JL. Le Roux, "Path Computation Element (PCE) Communication Protocol (PCEP)", RFC 5440, 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 Zhang, et al. Expires April 13, 2012 [Page 17] Internet-Draft PCEP Extensions for H-PCE October 2011 Engineering Label Switched Paths", RFC 5441, April 2009. 9.2. Informative References [I-D.ietf-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", draft-ietf-pce-hierarchy-fwk-00 (work in progress), October 2011. [RFC2629] Rose, M., "Writing I-Ds and RFCs using XML", RFC 2629, June 1999. [RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V., and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP Tunnels", RFC 3209, December 2001. [RFC4655] Farrel, A., Vasseur, J., and J. Ash, "A Path Computation Element (PCE)-Based Architecture", RFC 4655, August 2006. [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA Considerations Section in RFCs", BCP 26, RFC 5226, May 2008. [RFC5316] Chen, M., Zhang, R., and X. Duan, "ISIS Extensions in Support of Inter-Autonomous System (AS) MPLS and GMPLS Traffic Engineering", RFC 5316, December 2008. [RFC5392] Chen, M., Zhang, R., and X. Duan, "OSPF Extensions in Support of Inter-Autonomous System (AS) MPLS and GMPLS Traffic Engineering", RFC 5392, January 2009. Authors' Addresses Fatai Zhang Huawei Technologies F3-5-B R&D Center, Huawei Base. Bantian, Longgang District Shenzhen, 518129 P.R.China Phone: +86-755-28972912 Email: zhangfatai@huawei.com Zhang, et al. Expires April 13, 2012 [Page 18] Internet-Draft PCEP Extensions for H-PCE October 2011 Quintin Zhao Huawei Technologies 125 Nagog Technology Park Acton, MA 01719 US Phone: Email: qzhao@huawei.com Oscar Gonzalez de Dios Telefonica I+D Emilio Vargas, 6 Madrid, Spain Phone: Email: ogondio@tid.es Ramon Casellas CTTC Av. Carl Friedrich Gauss n.7 Castelldefels, Barcelona Spain Phone: +34 93 645 29 00 Email: ramon.casellas@cttc.es Daniel King Old Dog Consulting Phone: Email: daniel@olddog.co.uk Zhang, et al. Expires April 13, 2012 [Page 19]