Network Working Group S. Sivabalan Internet-Draft J. Medved Intended status: Standards Track C. Filsfils Expires: September 22, 2016 Cisco Systems, Inc. E. Crabbe R. Raszuk Mirantis Inc. V. Lopez Telefonica I+D J. Tantsura Ericsson W. Henderickx Alcatel Lucent J. Hardwick Metaswitch Networks March 21, 2016 PCEP Extensions for Segment Routing draft-ietf-pce-segment-routing-07.txt Abstract Segment Routing (SR) enables any head-end node to select any path without relying on a hop-by-hop signaling technique (e.g., LDP or RSVP-TE). It depends only on "segments" that are advertised by Link- State Interior Gateway Protocols (IGPs). A Segment Routed Path can be derived from a variety of mechanisms, including an IGP Shortest Path Tree (SPT), explicit configuration, or a Path Computation Element (PCE). This document specifies extensions to the Path Computation Element Protocol (PCEP) that allow a stateful PCE to compute and initiate Traffic Engineering (TE) paths, as well as a PCC to request a path subject to certain constraint(s) and optimization criteria in SR networks. 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]. Status of This Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Sivabalan, et al. Expires September 22, 2016 [Page 1] Internet-Draft PCEP Extensions for Segment Routing March 2016 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 September 22, 2016. Copyright Notice Copyright (c) 2016 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. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 3. Overview of PCEP Operation in SR Networks . . . . . . . . . . 5 4. SR-Specific PCEP Message Extensions . . . . . . . . . . . . . 7 5. Object Formats . . . . . . . . . . . . . . . . . . . . . . . 7 5.1. The OPEN Object . . . . . . . . . . . . . . . . . . . . . 7 5.1.1. The SR PCE Capability TLV . . . . . . . . . . . . . . 7 5.2. The RP/SRP Object . . . . . . . . . . . . . . . . . . . . 8 5.3. ERO Object . . . . . . . . . . . . . . . . . . . . . . . 8 5.3.1. SR-ERO Subobject . . . . . . . . . . . . . . . . . . 9 5.3.2. NAI Associated with SID . . . . . . . . . . . . . . . 11 5.3.3. ERO Processing . . . . . . . . . . . . . . . . . . . 12 5.4. RRO Object . . . . . . . . . . . . . . . . . . . . . . . 13 5.4.1. RRO Processing . . . . . . . . . . . . . . . . . . . 14 5.5. METRIC Object . . . . . . . . . . . . . . . . . . . . . . 14 6. Backward Compatibility . . . . . . . . . . . . . . . . . . . 15 7. Management Considerations . . . . . . . . . . . . . . . . . . 15 7.1. Policy . . . . . . . . . . . . . . . . . . . . . . . . . 15 7.2. The PCEP Data Model . . . . . . . . . . . . . . . . . . . 15 Sivabalan, et al. Expires September 22, 2016 [Page 2] Internet-Draft PCEP Extensions for Segment Routing March 2016 8. Security Considerations . . . . . . . . . . . . . . . . . . . 15 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 15 9.1. PCEP Objects . . . . . . . . . . . . . . . . . . . . . . 16 9.2. PCEP-Error Object . . . . . . . . . . . . . . . . . . . . 16 9.3. PCEP TLV Type Indicators . . . . . . . . . . . . . . . . 17 9.4. New Path Setup Type . . . . . . . . . . . . . . . . . . . 17 9.5. New Metric Type . . . . . . . . . . . . . . . . . . . . . 17 10. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 17 11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 17 12. References . . . . . . . . . . . . . . . . . . . . . . . . . 17 12.1. Normative References . . . . . . . . . . . . . . . . . . 18 12.2. Informative References . . . . . . . . . . . . . . . . . 19 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 19 1. Introduction SR technology leverages the source routing and tunneling paradigms. A source node can choose a path without relying on hop-by-hop signaling protocols such as LDP or RSVP-TE. Each path is specified as a set of "segments" advertised by link-state routing protocols (IS-IS or OSPF). [I-D.filsfils-rtgwg-segment-routing] provides an introduction to SR architecture. The corresponding IS-IS and OSPF extensions are specified in [I-D.ietf-isis-segment-routing-extensions] and [I-D.ietf-ospf-segment-routing-extensions], respectively. SR architecture defines a "segment" as a piece of information advertised by a link-state routing protocols, e.g. an IGP prefix or an IGP adjacency. Several types of segments are defined. A Node segment represents an ECMP-aware shortest-path computed by IGP to a specific node, and is always global within SR/IGP domain. An Adjacency Segment represents unidirectional adjacency. An Adjacency Segment is local to the node which advertises it. Both Node segments and Adjacency segments can be used for SR Traffic Engineering (SR-TE). The SR architecture can be applied to the MPLS forwarding plane without any change, in which case an SR path corresponds to an MPLS Label Switching Path (LSP). This document is relevant to only MPLS forwarding plane, and assumes that a 32-bit Segment Identifier (SID) represents an absolute value of MPLS label entry. In this document, "Node-SID" and "Adjacency-SID" denote Node Segment Identifier and Adjacency Segment Identifier respectively. A Segment Routed path (SR path) can be derived from an IGP Shortest Path Tree (SPT). SR-TE paths may not follow IGP SPT. Such paths may be chosen by a suitable network planning tool and provisioned on the source node of the SR-TE path. Sivabalan, et al. Expires September 22, 2016 [Page 3] Internet-Draft PCEP Extensions for Segment Routing March 2016 [RFC5440] describes Path Computation Element Protocol (PCEP) for communication between a Path Computation Client (PCC) and a Path Computation Element (PCE) or between one a pair of PCEs. A PCE or a PCC operating as a PCE (in hierarchical PCE environment) computes paths for MPLS Traffic Engineering LSPs (MPLS-TE LSPs) based on various constraints and optimization criteria. [I-D.ietf-pce-stateful-pce] specifies extensions to PCEP that allow a stateful PCE to compute and recommend network paths in compliance with [RFC4657] and defines objects and TLVs for MPLS-TE LSPs. Stateful PCEP extensions provide synchronization of LSP state between a PCC and a PCE or between a pair of PCEs, delegation of LSP control, reporting of LSP state from a PCC to a PCE, controlling the setup and path routing of an LSP from a PCE to a PCC. Stateful PCEP extensions are intended for an operational model in which LSPs are configured on the PCC, and control over them is delegated to the PCE. A mechanism to dynamically initiate LSPs on a PCC based on the requests from a stateful PCE or a controller using stateful PCE is specified in [I-D.ietf-pce-pce-initiated-lsp]. Such mechanism is useful in Software Driven Networks (SDN) applications, such as demand engineering, or bandwidth calendaring. It is possible to use a stateful PCE for computing one or more SR-TE paths taking into account various constraints and objective functions. Once a path is chosen, the stateful PCE can initiate an SR-TE path on a PCC using PCEP extensions specified in [I-D.ietf-pce-pce-initiated-lsp] using the SR specific PCEP extensions described in this document. Additionally, using procedures described in this document, a PCC can request an SR path from either stateful or a stateless PCE. This specification relies on the PATH-SETUP-TYPE TLV and procedures specified in [I-D.ietf-pce-lsp-setup-type]. 2. Terminology The following terminologies are used in this document: ERO: Explicit Route Object IGP: Interior Gateway Protocol IS-IS: Intermediate System to Intermediate System LSR: Label Switching Router MSD: Maximum SID Depth NAI: Node or Adjacency Identifier Sivabalan, et al. Expires September 22, 2016 [Page 4] Internet-Draft PCEP Extensions for Segment Routing March 2016 OSPF: Open Shortest Path First PCC: Path Computation Client PCE: Path Computation Element PCEP: Path Computation Element Protocol RRO: Record Route Object SID: Segment Identifier SR: Segment Routing SR-TE: Segment Routed Traffic Engineering TED: Traffic Engineering Database 3. Overview of PCEP Operation in SR Networks In SR networks, an ingress node of an SR path appends all outgoing packets with an SR header consisting of a list of SIDs (or MPLS labels in the context of this document). The header has all necessary information to guide the packets from the ingress node to the egress node of the path, and hence there is no need for any signaling protocol. In a PCEP session, LSP information is carried in the Explicit Route Object (ERO), which consists of a sequence of subobjects. Various types of ERO subobjects have been specified in [RFC3209], [RFC3473], and [RFC3477]. In SR networks, an ingress node of an SR path appends all outgoing packets with an SR header consisting of a list of SIDs (or MPLS labels in the context of this document). SR-TE LSPs computed by a PCE can be represented in one of the following forms: o An ordered set of IP address(es) representing network nodes/links: In this case, the PCC needs to convert the IP address(es) into the corresponding MPLS labels by consulting its Traffic Engineering Database (TED). o An ordered set of SID(s). o An ordered set of both MPLS label(s) and IP address(es): In this case, the PCC needs to convert the IP address(es) into the corresponding SID(s) by consulting its TED. This document defines a new ERO subobject denoted by "SR-ERO subobject" capable of carrying a SID as well as the identity of the Sivabalan, et al. Expires September 22, 2016 [Page 5] Internet-Draft PCEP Extensions for Segment Routing March 2016 node/adjacency represented by the SID. SR-capable PCEP speakers should be able to generate and/or process such ERO subobject. An ERO containing SR-ERO subobjects can be included in the PCEP Path Computation Reply (PCRep) message defined in [RFC5440], the PCEP LSP Initiate Request message (PCInitiate) defined in [I-D.ietf-pce-pce-initiated-lsp], as well as in the PCEP LSP Update Request (PCUpd) and PCEP LSP State Report (PCRpt) messages defined in defined in [I-D.ietf-pce-stateful-pce]. When a PCEP session between a PCC and a PCE is established, both PCEP speakers exchange information to indicate their ability to support SR-specific functionality. Furthermore, an LSP initially established via RSVP-TE signaling can be updated with SR-TE path. This capability is useful when a network is migrated from RSVP-TE to SR-TE technology. Similarly, an LSP initially created with SR-TE path can updated to signal the LSP using RSVP-TE if necessary. A PCC MAY include an RRO object containing the recorded LSP in PCReq and PCRpt messages as specified in [RFC5440] and [I-D.ietf-pce-stateful-pce] respectively. This document defines a new RRO subobject for SR networks. Methods used by a PCC to record SR-TE LSP are outside the scope of this document. In summary, this document: o Defines a new PCEP capability, new ERO subobject, new RRO subobject, a new TLV, and new PCEP error codes. o Specifies how two PCEP speakers can establish a PCEP session that can carry information about SR-TE paths. o Specifies processing rules of ERO subobject. o Defines a new path setup type carried in the PATH-SETUP-TYPE TLV for SR-TE LSP. The extensions specified in this document complement the existing PCEP specifications to support SR-TE path. As such, the PCEP messages (e.g., Path Computation Request, Path Computation Reply, Path Computation Report, Path Computation Update, Path Computation Initiate, etc.,) MUST be formatted according to [RFC5440], [I-D.ietf-pce-stateful-pce], [I-D.ietf-pce-pce-initiated-lsp], and any other applicable PCEP specifications. Sivabalan, et al. Expires September 22, 2016 [Page 6] Internet-Draft PCEP Extensions for Segment Routing March 2016 4. SR-Specific PCEP Message Extensions As defined in [RFC5440], a PCEP message consists of a common header followed by a variable length body made up of mandatory and/or optional objects. This document does not require any changes in the format of PCReq and PCRep messages specified in [RFC5440], PCInitiate message specified in [I-D.ietf-pce-pce-initiated-lsp], and PCRpt and PCUpd messages specified in [I-D.ietf-pce-stateful-pce]. However, PCEP messages pertaining to SR-TE LSP MUST include PATH-SETUP-TYPE TLV in the RP or SRP object to clearly identify that SR-TE LSP is intended. In other words, a PCEP speaker MUST not infer whether or not a PCEP message pertains to SR-TE LSP from any other object or TLV. 5. Object Formats 5.1. The OPEN Object This document defines a new optional TLV for use in the OPEN Object. 5.1.1. The SR PCE Capability TLV The SR-PCE-CAPABILITY TLV is an optional TLV associated with the OPEN Object to exchange SR capability of PCEP speakers. The format of the SR-PCE-CAPABILITY TLV is shown in the following figure: 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=4 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Reserved | Flags | MSD | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 1: SR-PCE-CAPABILITY TLV format The code point for the TLV type is to be defined by IANA. The TLV length is 4 octets. The 32-bit value is formatted as follows. The "Maximum SID Depth" (1 octet) field (MSD) specifies the maximum number of SIDs that a PCC is capable of imposing on a packet. The "Flags" (1 octet) and "Reserved" (2 octets) fields are currently unused, and MUST be set to zero on transmission and ignored on reception. Sivabalan, et al. Expires September 22, 2016 [Page 7] Internet-Draft PCEP Extensions for Segment Routing March 2016 5.1.1.1. Exchanging SR Capability By including the SR-PCE-CAPABILITY TLV in the OPEN message destined to a PCE, a PCC indicates that it is capable of supporting the head- end functions for SR-TE LSP. By including the TLV in the OPEN message destined to a PCC, a PCE indicates that it is capable of computing SR-TE paths. The number of SIDs that can be imposed on a packet depends on PCC's data plane's capability. An MSD value of zero means that a PCC does not impose any default limitation on the number of SIDs included in any SR-TE path coming from PCE. Once an SR-capable PCEP session is established with a non-zero MSD value, the corresponding PCE MUST NOT send SR-TE paths with SIDs exceeding that MSD value. If a PCC needs to modify the MSD value, the PCEP session MUST be closed and re- established with the new MSD value. If a PCEP session is established with a non-zero MSD value, and the PCC receives an SR-TE path containing more SIDs than specified in the MSD value, the PCC MUST send a PCErr message with Error-Type 10 (Reception of an invalid object) and Error-Value 3 (Unsupported number of Segment ERO). If a PCEP session is established with an MSD value of zero, then the PCC MAY specify an MSD for each path computation request that it sends to the PCE. The SR Capability TLV is meaningful only in the OPEN message sent from a PCC to a PCE. As such, a PCE does not need to set MSD value in outbound message to a PCC. Similarly, a PCC ignores any MSD value received from a PCE. If a PCE receives multiple SR-PCE-CAPABILITY TLVs in an OPEN message, it processes only the first TLV is processed. 5.2. The RP/SRP Object In order to setup an SR-TE LSP using SR, RP or SRP object MUST PATH- SETUP-TYPE TLV specified in [I-D.ietf-pce-lsp-setup-type]. This document defines a new Path Setup Type (PST) for SR as follows: o PST = 1: Path is setup using Segment Routing Traffic Engineering technique. 5.3. ERO Object An SR-TE path consists of one or more SID(s) where each SID MAY be associated with the identifier that represents the node or adjacency corresponding to the SID. This identifier is referred to as the 'Node or Adjacency Identifier' (NAI). As described later, a NAI can be represented in various formats (e.g., IPv4 address, IPv6 address, Sivabalan, et al. Expires September 22, 2016 [Page 8] Internet-Draft PCEP Extensions for Segment Routing March 2016 etc). Furthermore, a NAI is used for troubleshooting purposes and, if necessary, to derive SID value as described below. The ERO object specified in [RFC5440] is used to carry SR-TE path information. In order to carry SID and/or NAI, this document defines a new ERO subobject referred to as "SR-ERO subobject" whose format is specified in the following section. An ERO object carrying an SR-TE path consists of one or more ERO subobject(s), and MUST carry only SR-ERO subobject. Note that an SR-ERO subobject does not need to have both SID and NAI. However, at least one of them MUST be present. When building the MPLS label stack from ERO, a PCC MUST assume that SR-ERO subobjects are organized as a last-in-first-out stack. The first subobject relative to the beginning of ERO contains the information about the topmost label. The last subobject contains information about the bottommost label. 5.3.1. SR-ERO Subobject An SR-ERO subobject consists of a 32-bit header followed by the SID and the NAI associated with the SID. The SID is a 32-bit number. The size of the NAI depends on its respective type, as described in the following sections. 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 | ST | Flags |F|S|C|M| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | SID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ // NAI (variable) // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 2: SR-ERO Subobject format The fields in the SR-ERO Subobject are as follows: The 'L' Flag indicates whether the subobject represents a loose-hop in the LSP [RFC3209]. If this flag is unset, a PCC MUST not overwrite the SID value present in the SR-ERO subobject. Otherwise, a PCC MAY expand or replace one or more SID value(s) in the received SR-ERO based on its local policy. Type is the type of the SR-ERO subobject. This document defines the SR-ERO subobject type, and requests a new codepoint from IANA. Sivabalan, et al. Expires September 22, 2016 [Page 9] Internet-Draft PCEP Extensions for Segment Routing March 2016 Length contains the total length of the subobject in octets, including the L, Type and Length fields. Length MUST be at least 8, and MUST be a multiple of 4. As mentioned earlier, an SR-ERO subobject MUST have at least SID or NAI. The length should take into consideration SID or NAI only if they are not null. The flags described below used to indicate whether SID or NAI field is null. SID Type (ST) indicates the type of information associated with the SID contained in the object body. When ST value is 0, SID MUST NOT be null and NAI MUST be null. Other ST values are described later in this document. Flags is used to carry any additional information pertaining to SID. Currently, the following flag bits are defined: * M: When this bit is set, the SID value represents an MPLS label stack entry as specified in [RFC5462] where only the label value is specified by the PCE. Other fields (TC, S, and TTL) fields MUST be considered invalid, and PCC MUST set these fields according to its local policy and MPLS forwarding rules. * C: When this bit as well as the M bit are set, then the SID value represents an MPLS label stack entry as specified in [RFC5462], where all the entry's fields (Label, TC, S, and TTL) are specified by the PCE. However, a PCC MAY choose to override TC, S, and TTL values according its local policy and MPLS forwarding rules. * S: When this bit is set, the SID value in the subobject body is null. In this case, the PCC is responsible for choosing the SID value, e.g., by looking up its TED using the NAI which, in this case, MUST be present in the subobject. * F: When this bit is set, the NAI value in the subobject body is null. SID is the Segment Identifier. Sivabalan, et al. Expires September 22, 2016 [Page 10] Internet-Draft PCEP Extensions for Segment Routing March 2016 NAI contains the NAI associated with the SID. Depending on the value of ST, the NAI can have different format as described in the following section. 5.3.2. NAI Associated with SID This document defines the following NAIs: 'IPv4 Node ID' is specified as an IPv4 address. In this case, ST value is 1, and the Length is 8 or 12 depending on either SID or NAI or both are included in the subobject. 'IPv6 Node ID' is specified as an IPv6 address. In this case, ST and Length are 2, and Length is 8, 20, or 24 depending on either SID or NAI or both are included in the subobject. 'IPv4 Adjacency' is specified as a pair of IPv4 addresses. In this case, ST value is 3. The Length is 8, 12, or 16 depending on either SID or NAI or both are included in the subobject, and the format of the NAI is shown in the following figure: 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Local IPv4 address | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Remote IPv4 address | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 3: NAI for IPv4 Adjacency 'IPv6 Adjacency' is specified as a pair of IPv6 addresses. In this case, ST valie is 4. The Length is 8, 36 or 40 depending on whether SID or NAI or both included in the subobject,and the format of the NAI is shown in the following figure: Sivabalan, et al. Expires September 22, 2016 [Page 11] Internet-Draft PCEP Extensions for Segment Routing March 2016 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ // Local IPv6 address (16 bytes) // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ // Remote IPv6 address (16 bytes) // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 4: NAI for IPv6 adjacenc y 'Unnumbered Adjacency with IPv4 NodeIDs' is specified as a pair of Node ID / Interface ID tuples. In this case, ST value is 5. The Length is 8, 20, or 24 depending on whether SID or NAI or both included in the subobject, and the format of the NAI is shown in the following figure: 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Local Node-ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Local Interface ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Remote Node-ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Remote Interface ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 5: NAI for Unnumbered adjacency with IPv4 Node IDs Editorial Note: We are yet to decide if another SID subobject is required for unnumbered adjacency with 128 bit node ID. 5.3.3. ERO Processing A PCEP speaker that does not recognize the SR-ERO subobject in PCRep, PCInitiate, PCUpd or PCRpt messages MUST reject the entire PCEP message and MUST send a PCErr message with Error-Type=3 ("Unknown Object") and Error-Value=2 ("Unrecognized object Type") or Error- Type=4 ("Not supported object") and Error-Value=2 ("Not supported object Type"), defined in [RFC5440]. When the SID represents an MPLS label (i.e. the M bit is set), its value (20 most significant bits) MUST be larger than 15, unless it is special purpose label, such as an Entropy Label Indicator (ELI). If a PCEP speaker receives a label ERO subobject with an invalid value, Sivabalan, et al. Expires September 22, 2016 [Page 12] Internet-Draft PCEP Extensions for Segment Routing March 2016 it MUST send a PCErr message with Error-Type = 10 ("Reception of an invalid object") and Error Value = TBD ("Bad label value"). If both M and C bits of an ERO subobject are set, and if a PCEP speaker finds erroneous setting in one or more of TC, S, and TTL fields, it MUST send a PCErr message with Error-Type = 10 ("Reception of an invalid object") and Error-Value = TBD ("Bad label format"). If a PCC receives a stack of SR-ERO subobjects, and the number of stack exceeds the maximum number of SIDs that the PCC can impose on the packet, it MAY send a PCErr message with Error-Type = 10 ("Reception of an invalid object") and Error-Value = TBD ("Unsupported number of Segment ERO subobjects"). When a PCEP speaker detects that all subobjects of ERO are not identical, and if it does not handle such ERO, it MUST send a PCErr message with Error-Type = 10 ("Reception of an invalid object") and Error-Value = TBD ("Non-identical ERO subobjects"). If a PCEP speaker receives an SR-ERO subobject in which both SID and NAI are absent, it MUST consider the entire ERO object invalid and send a PCErr message with Error-Type = 10 ("Reception of an invalid object") and Error-Value = TBD ("Both SID and NAI are absent in ERO subobject"). When a PCEP speaker receives an SR-ERO subobject in which ST is 0, SID MUST be present and NAI MUST NOT be present(i.e., S-flag MUST be 0, F-flag MUST be 1, and the Length MUST be 8). Otherwise, it MUST consider the entire ERO object invalid and send a PCErr message with Error-Type = 10 ("Reception of an invalid object") and Error-Value = TBD ("Malformed object"). The PCEP speaker MAY include the malformed SR-ERO object in the PCErr message as well. 5.4. RRO Object A PCC can record SR-TE LSP and report the LSP to a PCE via RRO. An RRO object contains one or more subobjects called "SR-RRO subobjects" whose format is shown below: Sivabalan, et al. Expires September 22, 2016 [Page 13] Internet-Draft PCEP Extensions for Segment Routing March 2016 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 | Length | ST | Flags |F|S|C|M| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | SID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ // NAI (variable) // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 6: SR-RRO Subobject format The format of SR-RRO subobject is the same as that of SR-ERO subobject without L flag. A PCC MUST assume that SR-RRO subobjects are organized such that the first subobject relative to the beginning of RRO contains the information about the topmost label, and the last subobject contains information about the bottommost label of the SR-TE LSP. 5.4.1. RRO Processing Processing rules of SR-RRO subobject are identical to those of SR-ERO subobject. If a PCEP speaker receives an SR-RRO subobject in which both SID and NAI are absent, it MUST consider the entire RRO object invalid and send a PCErr message with Error-Type = 10 ("Reception of an invalid object") and Error-Value = TBD ("Both SID and NAI are absent in RRO subobject"). If a PCE detects that all subobjects of RRO are not identical, and if it does not handle such RRO, it MUST send a PCErr message with Error- Type = 10 ("Reception of an invalid object") and Error-Value = TBD ("Non-identical RRO subobjects"). 5.5. METRIC Object If a PCEP session is established with an MSD value of zero, then the PCC MAY specify the MSD for an individual path computation request using the METRIC object defined in [RFC5440]. This document defines a new type for the METRIC object to be used for this purpose as follows: o T = TBD (suggested value 11): Maximum SID Depth of the requested path. Sivabalan, et al. Expires September 22, 2016 [Page 14] Internet-Draft PCEP Extensions for Segment Routing March 2016 The PCC sets the metric-value to the MSD for this path. The PCC MUST set the B (bound) bit to 1 in the METRIC object, which specifies that the SID depth for the computed path MUST NOT exceed the metric-value. If a PCEP session is established with a non-zero MSD value, then the PCC MUST NOT send an MSD METRIC object. If the PCE receives a path computation request with an MSD METRIC object on a session with a non-zero MSD value then it MUST consider the request invalid and send a PCErr with Error-Type = 10 ("Reception of an invalid object") and Error-Value TBD ("Default MSD is specified for the PCEP session"). 6. Backward Compatibility A PCEP speaker that does not support the SR PCEP capability cannot recognize the SR-ERO or SR-RRO subobjects. As such, it MUST send a PCEP error with Error-Type = 4 (Not supported object) and Error-Value = 2 (Not supported object Type) as per [RFC5440]. 7. Management Considerations 7.1. Policy PCEP implementation: o Can enable SR PCEP capability either by default or via explicit configuration. o May generate PCEP error due to unsupported number of SR-ERO or SR- RRO subobjects either by default or via explicit configuration. 7.2. The PCEP Data Model A PCEP MIB module is defined in [I-D.ietf-pce-pcep-mib] needs be extended to cover additional functionality provided by [RFC5440] and [I-D.ietf-pce-pce-initiated-lsp]. Such extension will cover the new functionality specified in this document. 8. Security Considerations The security considerations described in [RFC5440] and [I-D.ietf-pce-pce-initiated-lsp] are applicable to this specification. No additional security measure is required. 9. IANA Considerations Sivabalan, et al. Expires September 22, 2016 [Page 15] Internet-Draft PCEP Extensions for Segment Routing March 2016 9.1. PCEP Objects This document defines a new sub-object type for the PCEP explicit route object (ERO), and a new sub-object type for the PCEP record route object (RRO). The code points for sub-object types of these objects is maintained in the RSVP parameters registry, under the EXPLICIT_ROUTE and ROUTE_RECORD objects. IANA is requested to allocate code points in the RSVP Parameters registry for each of the new sub-object types defined in this document, as follows: Object Sub-Object Sub-Object Type --------------------- -------------------------- ------------------ EXPLICIT_ROUTE SR-ERO (PCEP-specific) TBD (recommended 36) ROUTE_RECORD SR-RRO (PCEP-specific) TBD (recommended 36) 9.2. PCEP-Error Object IANA is requested to allocate code-points in the PCEP-ERROR Object Error Types and Values registry for the following new error-values: Error-Type Meaning ---------- ------- 10 Reception of an invalid object. Error-value = TBD (recommended 2): Bad label value Error-value = TBD (recommended 3): Unsupported number of Segment ERO subobjects Error-value = TBD (recommended 4): Bad label format Error-value = TBD (recommended 5): Non-identical ERO subobjects Error-value = TBD (recommended 6): Both SID and NAI are absent in ERO subobject Error-value = TBD (recommended 7): Both SID and NAI are absent in RRO subobject Error-value = TBD (recommended 9): Default MSD is specified for the PCEP session Error-value = TBD (recommended 10): Non-identical RRO subobjects Error-value = TBD (recommended 11): Malformed object Sivabalan, et al. Expires September 22, 2016 [Page 16] Internet-Draft PCEP Extensions for Segment Routing March 2016 9.3. PCEP TLV Type Indicators IANA is requested to allocate a new code point in the PCEP TLV Type Indicators registry, as follows: Value Meaning Reference ------------------------- ---------------------------- -------------- TBD (recommended 26) SR-PCE-CAPABILITY This document 9.4. New Path Setup Type [I-D.ietf-pce-lsp-setup-type] defines the PATH-SETUP-TYPE TLV and requests that IANA creates a registry to manage the value of the PATH_SETUP_TYPE TLV's PST field. IANA is requested to allocate a new code point in the PCEP PATH_SETUP_TYPE TLV PST field registry, as follows: Value Description Reference ------------------------- ---------------------------- -------------- 1 Traffic engineering path is This document setup using Segment Routing technique. 9.5. New Metric Type IANA is requested to allocate a new code point in the PCEP METRIC object T field registry, as follows: Value Description Reference ------------------------- ---------------------------- -------------- TBD (recommended 11) Segment-ID (SID) Depth. This document 10. Contributors The following people contributed to this document: - Lakshmi Sharma 11. Acknowledgements We like to thank Ina Minei, George Swallow, Marek Zavodsky and Tomas Janciga for the valuable comments. 12. References Sivabalan, et al. Expires September 22, 2016 [Page 17] Internet-Draft PCEP Extensions for Segment Routing March 2016 12.1. Normative References [I-D.filsfils-rtgwg-segment-routing] Filsfils, C., Previdi, S., Bashandy, A., Decraene, B., Litkowski, S., Horneffer, M., Milojevic, I., Shakir, R., Ytti, S., Henderickx, W., Tantsura, J., and E. Crabbe, "Segment Routing Architecture", draft-filsfils-rtgwg- segment-routing-01 (work in progress), October 2013. [I-D.ietf-isis-segment-routing-extensions] Previdi, S., Filsfils, C., Bashandy, A., Gredler, H., Litkowski, S., and J. Tantsura, "IS-IS Extensions for Segment Routing", draft-ietf-isis-segment-routing- extensions-00 (work in progress), April 2014. [I-D.ietf-ospf-segment-routing-extensions] Psenak, P., Previdi, S., Filsfils, C., Gredler, H., Shakir, R., Henderickx, W., and J. Tantsura, "OSPF Extensions for Segment Routing", draft-ietf-ospf-segment- routing-extensions-00 (work in progress), June 2014. [I-D.ietf-pce-lsp-setup-type] Sivabalan, S., Medved, J., Minei, I., Crabbe, E., and R. Varga, "Conveying path setup type in PCEP messages", draft-ietf-pce-lsp-setup-type-00 (work in progress), October 2014. [I-D.ietf-pce-pce-initiated-lsp] Crabbe, E., Minei, I., Sivabalan, S., and R. Varga, "PCEP Extensions for PCE-initiated LSP Setup in a Stateful PCE Model", draft-ietf-pce-pce-initiated-lsp-01 (work in progress), June 2014. [I-D.ietf-pce-pcep-mib] Koushik, K., Stephan, E., Zhao, Q., King, D., and J. Hardwick, "PCE communication protocol (PCEP) Management Information Base", draft-ietf-pce-pcep-mib-04 (work in progress), February 2013. [I-D.ietf-pce-stateful-pce] Crabbe, E., Medved, J., Minei, I., and R. Varga, "PCEP Extensions for Stateful PCE", draft-ietf-pce-stateful- pce-05 (work in progress), July 2013. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . Sivabalan, et al. Expires September 22, 2016 [Page 18] Internet-Draft PCEP Extensions for Segment Routing March 2016 [RFC5440] Vasseur, JP., Ed. and JL. Le Roux, Ed., "Path Computation Element (PCE) Communication Protocol (PCEP)", RFC 5440, DOI 10.17487/RFC5440, March 2009, . [RFC5462] Andersson, L. and R. Asati, "Multiprotocol Label Switching (MPLS) Label Stack Entry: "EXP" Field Renamed to "Traffic Class" Field", RFC 5462, DOI 10.17487/RFC5462, February 2009, . 12.2. Informative References [RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V., and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP Tunnels", RFC 3209, DOI 10.17487/RFC3209, December 2001, . [RFC3473] Berger, L., Ed., "Generalized Multi-Protocol Label Switching (GMPLS) Signaling Resource ReserVation Protocol- Traffic Engineering (RSVP-TE) Extensions", RFC 3473, DOI 10.17487/RFC3473, January 2003, . [RFC3477] Kompella, K. and Y. Rekhter, "Signalling Unnumbered Links in Resource ReSerVation Protocol - Traffic Engineering (RSVP-TE)", RFC 3477, DOI 10.17487/RFC3477, January 2003, . [RFC4657] Ash, J., Ed. and J. Le Roux, Ed., "Path Computation Element (PCE) Communication Protocol Generic Requirements", RFC 4657, DOI 10.17487/RFC4657, September 2006, . Authors' Addresses Siva Sivabalan Cisco Systems, Inc. 2000 Innovation Drive Kanata, Ontario K2K 3E8 Canada Email: msiva@cisco.com Sivabalan, et al. Expires September 22, 2016 [Page 19] Internet-Draft PCEP Extensions for Segment Routing March 2016 Jan Medved Cisco Systems, Inc. 170 West Tasman Dr. San Jose, CA 95134 US Email: jmedved@cisco.com Clarence Filsfils Cisco Systems, Inc. Pegasus Parc De kleetlaan 6a, DIEGEM BRABANT 1831 BELGIUM Email: cfilsfil@cisco.com Edward Crabbe Robert Raszuk Mirantis Inc. 100-615 National Ave. Mountain View, CA 94043 US Email: robert@raszuk.net Victor Lopez Telefonica I+D Don Ramon de la Cruz 82-84 Madrid 28045 Spain Email: vlopez@tid.es Jeff Tantsura Ericsson 300 Holger Way San Jose, CA 95134 USA Email: jeff.tantsura@ericsson.com Sivabalan, et al. Expires September 22, 2016 [Page 20] Internet-Draft PCEP Extensions for Segment Routing March 2016 Wim Henderickx Alcatel Lucent Copernicuslaan 50 Antwerp 2018, CA 95134 BELGIUM Email: wim.henderickx@alcatel-lucent.com Jon Hardwick Metaswitch Networks 100 Church Street Enfield, Middlesex UK Email: jon.hardwick@metaswitch.com Sivabalan, et al. Expires September 22, 2016 [Page 21]