PCE Working Group X. Xu Internet-Draft Huawei Intended status: Standards Track J. You Expires: January 4, 2018 S. Sivabalan Cisco H. Shah Ciena L. Contreras Telefonica I+D D. Bernier Bell Canada S. Ma Juniper July 3, 2017 PCEP Extensions for Unifed Source Routing-based SFC draft-xu-pce-sr-sfc-05 Abstract MPLS-SPRING (a.k.a., MPLS Segment Routing) could be leveraged to realize a unified source routing mechanism across MPLS, IPv4 and IPv6 data planes by using a unified source routing instruction set while preserving backward compatibility with MPLS-SPRING. More specifically, the source routing instruction set information contained in a source routed packet could be uniformly encoded as an MPLS label stack no matter the underlay is IPv4, IPv6 or MPLS. The unified source routing mechanism could be leveraged to realize a transport-independent service function chaining by encoding the service function path information or service function chain information as an MPLS label stack. This document describes extensions to the Path Computation Element Protocol (PCEP) that allow a PCE to compute and instantiate service function paths in the unifed source routing based service function chaining context. The extensions specified in this document are applicable to both the stateless PCE model and the stateful PCE model. 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 RFC 2119 [RFC2119]. Xu, et al. Expires January 4, 2018 [Page 1] Internet-Draft July 2017 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 January 4, 2018. Copyright Notice Copyright (c) 2017 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 . . . . . . . . . . . . . . . . . . . . . . . . . 5 3. PCEP Message Extensions for MPLS Source Routing-based SFC . . 5 3.1. PCReq Message . . . . . . . . . . . . . . . . . . . . . . 5 3.2. PCRep Message . . . . . . . . . . . . . . . . . . . . . . 5 3.3. PCUpd Message . . . . . . . . . . . . . . . . . . . . . . 6 3.4. PCRpt Message . . . . . . . . . . . . . . . . . . . . . . 6 4. Object Formats . . . . . . . . . . . . . . . . . . . . . . . 6 4.1. OPEN Object . . . . . . . . . . . . . . . . . . . . . . . 6 4.1.1. SR-SFC PCE Capability TLV . . . . . . . . . . . . . . 6 4.2. RP/SRP Object . . . . . . . . . . . . . . . . . . . . . . 7 4.3. Include Route Object . . . . . . . . . . . . . . . . . . 7 4.4. SR-SFC-ERO Object . . . . . . . . . . . . . . . . . . . . 8 4.4.1. SR-SFC-ERO Subobject . . . . . . . . . . . . . . . . 8 Xu, et al. Expires January 4, 2018 [Page 2] Internet-Draft July 2017 4.4.2. NSI Associated with SID . . . . . . . . . . . . . . . 10 4.4.3. SR-SFC-ERO Processing . . . . . . . . . . . . . . . . 10 5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 10 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10 6.1. PCEP Objects . . . . . . . . . . . . . . . . . . . . . . 10 6.2. PCEP-Error Object . . . . . . . . . . . . . . . . . . . . 10 6.3. PCEP TLV Type Indicators . . . . . . . . . . . . . . . . 10 6.4. New Path Setup Type . . . . . . . . . . . . . . . . . . . 10 6.5. New IRO Sub-object Type . . . . . . . . . . . . . . . . . 11 7. Security Considerations . . . . . . . . . . . . . . . . . . . 11 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 11 8.1. Normative References . . . . . . . . . . . . . . . . . . 11 8.2. Informative References . . . . . . . . . . . . . . . . . 11 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 12 1. Introduction Service Function Chaining [RFC7665] provides a flexible way to construct services. When applying a particular Service Function Chain (SFC) to the traffic classified by the Classifier, the traffic needs to be steered through an ordered set of Service Function Forwarders (SFF) and Service Functions (SF) in the network. This ordered set of SFFs and SFs in the network, referred to as a Service Function Path (SFP), is an instantiation of the SFC in the network. For example, as shown in Figure 1, an SFP corresponding to the SFC of {SF1, SF3} can be expressed as {SFF1, SF1, SFF2, SF3}. Xu, et al. Expires January 4, 2018 [Page 3] Internet-Draft July 2017 +-------+ +--+ PCE | | +-------+ | | | | +-------------------------------------------------+ | | MPLS-SR Netowrks | | | +-----+ +-----+ | | | | SF1 | | SF2 | | | | +--+--+ +--+--+ | | | | | | | | ^ | | | | | (2)| +---+ +---+ | | | +--+ | | | ++---------+ | | | +--------------+ | | +----+| V | | | +-----+ | | | |PCC || (1) +---+-+----+ (3) | | SF3 | | | --> |SFC +----+|----> | SFF1 |---->| +-----+ |----> ----+Classifier+------+ +-----+ SFF2 +-------- +----------+ +----------+ +--------------+ | | | +-------------------------------------------------+ Figure 1: PCE-based Service Function Chaining in MPLS-SR Network MPLS-SPRING (a.k.a., MPLS Segment Routing) could be leveraged to realize a unified source routing mechanism across MPLS, IPv4 and IPv6 data planes by using a unified source routing instruction set while preserving backward compatibility with MPLS-SPRING as descried in [I-D.xu-mpls-unified-source-routing-instruction]. More specifically, the source routing instruction set information contained in a source routed packet could be uniformly encoded as an MPLS label stack no matter the underlay is IPv4, IPv6 or MPLS. The unified source routing mechanism in turn could be leveraged to realize a transport- independent service function chaining by encoding the service function path information or service function chain information as an MPLS label stack as described in [I-D.xu-mpls-service-chaining]. This document describes extensions to the Path Computation Element Protocol (PCEP) that allow a PCE to compute and instantiate service function paths in the MPLS source routing based service function chaining context. More specifically, the PCC provides an ordered list of SF IDs to the PCE and indicates to the PCE that what type SFs and paths are requested (e.g., an SFP, or a compact SFP, or an SR- specific SFP, or a compact SR-specific SFP) through the path computation request message, and then the PCE responds with a corresponding path through the path computation response message. Xu, et al. Expires January 4, 2018 [Page 4] Internet-Draft July 2017 The extensions specified in this document are applicable to both the stateless PCE model [RFC5440] and the stateful PCE model [I-D.ietf-pce-stateful-pce]. 2. Terminology This memo makes use of the terms defined in [RFC5440], [I-D.ietf-pce-segment-routing] and [I-D.xu-mpls-service-chaining]. In addition, this memo defines the following two additional terms: Compact SFP: An ordered list of SFFs. SR-specific SFP: An ordered list of node SIDs (representing SFFs) and Service Function SIDs. Compact SR-specific SFP: An ordered list of node SIDs (representing SFFs). 3. PCEP Message Extensions for MPLS Source Routing-based SFC 3.1. PCReq Message This document does not specify any changes to the PCReq message format. This document requires the PATH-SETUP-TYPE TLV [I-D.ietf-pce-lsp-setup-type] to be carried in the RP Object in order for a PCC to request a particular type of path. Four new Path Setup Types need to be defined for MPLS source routing-based SFC (see Section 4.2). This document also requires the Include Route Object (IRO) to be carried in the PCReq message in order for a PCC to specify an SFC. A new IRO sub-object type needs to be defined for SF (see Section 4.3). 3.2. PCRep Message This document defines the format of the PCRep message carrying an SFP. The message is sent by a PCE to a PCC in response to a previously received PCReq message, where the PCC requested an SFP. The format of the SFC-specific PCRep message is defined as follows: ::= Where: ::=[] ::= [] [] Where: ::=[] Xu, et al. Expires January 4, 2018 [Page 5] Internet-Draft July 2017 The RP and NO-PATH Objects are defined in [RFC5440]. The object contains an SFP and is defined in Section 4.4. 3.3. PCUpd Message This document defines the format of the PCUpd message carrying an SFP update. The message is sent forwardly by a PCE to a PCC to update an previously computed SFP. The format of the PCUpd message is defined as follows: ::= Where: ::=[] ::= Where: ::=[] 3.4. PCRpt Message PCPRpt message sent from a PCC to PCE as a respond to a PCUpd message or in an unsolicited manner (e.g., during state synchronization). The format of the PCUpd message is defined as follows: ::= Where: ::=[] ::=[] Where: ::=[] 4. Object Formats 4.1. OPEN Object This document defines a new optional TLV for use in the OPEN Object. 4.1.1. SR-SFC PCE Capability TLV The SR-SFC-PCE-CAPABILITY TLV is an optional TLV for use in the OPEN Object to negotiate SR-SFC capability on the PCEP session. The format of the SR-SFC-PCE-CAPABILITY TLV is shown in the following Figure 2: Xu, et al. Expires January 4, 2018 [Page 6] Internet-Draft July 2017 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 2: SR-SFC-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 and ignored on receipt. 4.1.1.1. Negotiating SR-SFC Capability The SR-SFC capability TLV is contained in the OPEN object. By including the TLV in the OPEN message to a PCE, a PCC indicates its support for SFPs. By including the TLV in the OPEN message to a PCC, a PCE indicates that it is capable of computing SFPs. 4.2. RP/SRP Object In order to setup an SFP, the RP or SRP object MUST carry a PATH- SETUP-TYPE TLV specified in [I-D.ietf-pce-lsp-setup-type]. This document defines four new Path Setup Types (PST) for SR-SFC as follows: PST = 2: The path is an SFP. PST = 3: The path is a compact SFP. PST = 4: The path is an SR-specific SFP. PST = 5: The path is a compact SR-specific SFP. 4.3. Include Route Object The IRO (Include Route Object) MUST be carried within PCReq messages to indicate a particular SFC. Furthermore, the IRO MAY be carried in PCRep messages. When carried within a PCRep message with the NO-PATH object, the IRO indicates the set of service functions that cause the PCE to fail to find a path. This document defines a new sub-object type for the SR-SFC as follows: Xu, et al. Expires January 4, 2018 [Page 7] Internet-Draft July 2017 Type Sub-object 5 Service Function ID 4.4. SR-SFC-ERO Object Generally speaking, an SR-SFC-ERO object consists of one or more ERO subobjects described in the following sub-sections to represent a particular type of service function path. In the ERO subobject, each SID is associated with an identifier that represents either an SFF or an SF. This identifier is referred to as the 'Node or Service Identifier' (NSI). As described later, an NSI can be represented in various formats (e.g., IPv4 address, IPv6 address, SF identifier, etc). Specifically, in the SFP case, the NSI of every ERO subobject contained in the SR-SFC-ERO object represents an SFF or an SF while the SID of each ERO subobject is set to null. In the compact SFP case, the NSI of every ERO subobject contained in the SR-SFC-ERO object only represents an SFF meanwhile the SID of every ERO subobject is set to null. In the SR-specific SFP, the NSI of every ERO subobject contained in the SR-SFC-ERO object represents an SFF or an SF while the SID of every ERO subject MUST NOT be null. In the compact SR-specific SFP, the NSI of every ERO subobject contained in the SR-SFC-ERO object represents an SFF meanwhile the SID of every ERO subobject MUST NOT be null. 4.4.1. SR-SFC-ERO Subobject An SR-SFC-ERO subobject (as shown in Figure 3) consists of a 32-bit header followed by the SID and the NSI associated with the SID. The SID is a 32-bit or 128 bit number. The size of the NSI depends on its respective type, as described in the following sub-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 | NSIT | Flags |P|F|S|C|M| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ // SID (variable:4 or 16 octets) // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ // NSI (variable) // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 3: SR-SFC-ERO Subobject Format 'L' Flag: indicates whether the subobject represents a loose-hop in the explicit route [RFC3209]. If this flag is unset, a PCC MUST not overwrite the SID value present in the SR-SFC-ERO Xu, et al. Expires January 4, 2018 [Page 8] Internet-Draft July 2017 subobject. Otherwise, a PCC MAY expand or replace one or more SID value(s) in the received SR-SFC-ERO based on its local policy. Type: is the type of the SR-SFC-ERO Subobject. This document defines the SR-SFC-ERO Subobject type. A new code point will be requested for the SR-SFC-ERO Subobject from IANA. Length: contains the total length of the subobject in octets, including the L, Type and Length fields. Length MUST be at least 4, and MUST be a multiple of 4. NSI Type (NSIT): indicates the type of NSI associated with the SID. The NSI-Type 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 Traffic Engineering Database (TED) using node/service identifier in the subobject body. F: When this bit is set, the NSI value in the subobject body is null.// When will the NSI value is null? P: When this bit is set, the SID value represents an IPv6 address. SID: is the 4-octect or 16-octect Segment Identifier. NSI: contains the NSI associated with the SID. Depending on the value of NSIT, the NSI can have different format as described in the following sub-section. Xu, et al. Expires January 4, 2018 [Page 9] Internet-Draft July 2017 4.4.2. NSI Associated with SID This document defines the following NSIs: 'IPv4 Node ID': is specified as an IPv4 address. In this case, NSIT and Length are 1 and 12 respectively. 'IPv6 Node ID': is specified as an IPv6 address. In this case, NSIT and Length are 2 and 24 respectively. 'Service Function ID': is specified as an SF ID. In this case, NSIT and Length are TBD. 4.4.3. SR-SFC-ERO Processing TBD 5. Acknowledgements TBD. 6. IANA Considerations 6.1. PCEP Objects IANA is requested to allocate an ERO subobject type (recommended value= 6) for the SR-SFC-ERO subobject. 6.2. PCEP-Error Object TBD 6.3. PCEP TLV Type Indicators This document defines the following new PCEP TLV: Value Meaning Reference 27 SR-SFC-PCE-CAPABILITY This document 6.4. New Path Setup Type This document defines the following four new setup types for the PATH-SETUP-TYPE TLV: Xu, et al. Expires January 4, 2018 [Page 10] Internet-Draft July 2017 Value Description Reference 2 The path is an SFP. This document 3 The path is a compact SFP. This document 4 The path is an SR-specific SFP. This document 5 The path is a compact SR-specific SFP. This document 6.5. New IRO Sub-object Type This document defines a new IRO sub-object type for SFC as follows: Type Sub-object 5 Service Function ID 7. Security Considerations This document does not introduce any new security considerations. 8. References 8.1. Normative References [I-D.ietf-pce-stateful-pce] Crabbe, E., Minei, I., Medved, J., and R. Varga, "PCEP Extensions for Stateful PCE", draft-ietf-pce-stateful- pce-21 (work in progress), June 2017. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC5440] Vasseur, JP., Ed. and JL. Le Roux, Ed., "Path Computation Element (PCE) Communication Protocol (PCEP)", RFC 5440, DOI 10.17487/RFC5440, March 2009, . 8.2. Informative References Xu, et al. Expires January 4, 2018 [Page 11] Internet-Draft July 2017 [I-D.ietf-pce-lsp-setup-type] Sivabalan, S., Tantsura, J., Minei, I., Varga, R., and J. Hardwick, "Conveying path setup type in PCEP messages", draft-ietf-pce-lsp-setup-type-04 (work in progress), April 2017. [I-D.ietf-pce-segment-routing] Sivabalan, S., Filsfils, C., Tantsura, J., Henderickx, W., and J. Hardwick, "PCEP Extensions for Segment Routing", draft-ietf-pce-segment-routing-09 (work in progress), April 2017. [I-D.ietf-spring-segment-routing-mpls] Filsfils, C., Previdi, S., Bashandy, A., Decraene, B., Litkowski, S., and R. Shakir, "Segment Routing with MPLS data plane", draft-ietf-spring-segment-routing-mpls-10 (work in progress), June 2017. [I-D.xu-mpls-service-chaining] Xu, X., Bryant, S., Assarpour, H., Shah, H., Contreras, L., daniel.bernier@bell.ca, d., jefftant@gmail.com, j., Ma, S., and M. Vigoureux, "Service Chaining using Unified Source Routing Instructions", draft-xu-mpls-service- chaining-03 (work in progress), June 2017. [I-D.xu-mpls-unified-source-routing-instruction] Xu, X., Bryant, S., Raszuk, R., Chunduri, U., Contreras, L., Jalil, L., Assarpour, H., Velde, G., Tantsura, J., and S. Ma, "Unified Source Routing Instruction using MPLS Label Stack", draft-xu-mpls-unified-source-routing- instruction-02 (work in progress), June 2017. [RFC7665] Halpern, J., Ed. and C. Pignataro, Ed., "Service Function Chaining (SFC) Architecture", RFC 7665, DOI 10.17487/RFC7665, October 2015, . Authors' Addresses Xiaohu Xu Huawei Email: xuxiaohu@huawei.com JIanjie You Email: jianjie.you@gmail.com Xu, et al. Expires January 4, 2018 [Page 12] Internet-Draft July 2017 Siva Sivabalan Cisco Email: msiva@cisco.com Himanshu Shah Ciena Email: hshah@ciena.com Luis M. Contreras Telefonica I+D Ronda de la Comunicacion, s/n Sur-3 building, 3rd floor Madrid, 28050 Spain Email: luismiguel.contrerasmurillo@telefonica.com URI: http://people.tid.es/LuisM.Contreras/ Daniel Bernier Bell Canada Email: daniel.bernier@bell.ca Shaowen Ma Juniper Email: mashaowen@gmail.com Xu, et al. Expires January 4, 2018 [Page 13]