SFC WG G. Mirsky Internet-Draft ZTE Corp. Intended status: Standards Track W. Meng Expires: November 4, 2017 ZTE Corporation B. Khasnabish ZTE TX, Inc. C. Wang May 3, 2017 Multi-Layer OAM for Service Function Chains in Networks draft-wang-sfc-multi-layer-oam-07 Abstract This document discusses a multi-layer approach to the task of Operation, Administration and Maintenance (OAM) of Service Function Chains (SFCs) in networks. Based on the SFC OAM requirements, a multi-layer model is introduced. A mechanism to detect and localize defects using the multi-layer model is also described in this draft. 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 November 4, 2017. 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 Mirsky, et al. Expires November 4, 2017 [Page 1] Internet-Draft Multi-Layer OAM for SFC May 2017 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 . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . 3 2.1. Requirements Language . . . . . . . . . . . . . . . . . . 3 2.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3 3. Multi-layer Model of SFC OAM . . . . . . . . . . . . . . . . 3 4. Requirements for SFC OAM Multi-layer Model . . . . . . . . . 4 5. SFC OAM multi-layer model . . . . . . . . . . . . . . . . . . 5 6. Gap analysis . . . . . . . . . . . . . . . . . . . . . . . . 6 7. Security Considerations . . . . . . . . . . . . . . . . . . . 6 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 6 9.1. Normative References . . . . . . . . . . . . . . . . . . 6 9.2. Informative References . . . . . . . . . . . . . . . . . 6 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7 1. Introduction [RFC7665] defines components necessary to implement Service Function Chain (SFC). These include a classifier which performs classification of incoming packets. A Service Function Forwarder (SFF) is responsible for forwarding traffic to one or more connected Service Functions (SFs) according to the information carried in the SFC encapsulation. SFF also handles traffic coming back from the SF and transports the data packets to the next SFF. And the SFF serves as termination element of the Service Function Path (SFP). SF is responsible for specific treatment of received packets. Resulting from that SFC is constructed by a number of these components, there are different views from different levels of the SFC. One is the SFC, fully abstract entity, that defines an ordered set of SFs that must be applied to packets selected as a result of classification. But SFC doesn't define exact mapping between SFFs and SFs. Thus there exists another semi-abstract entity referred as SFP. SFP is the instantiation of the SFC in the network and provides a level of indirection between the fully abstract SFC and a fully specified ordered list of SFFs and SFs identities that the packet will visit when it traverses the SFC. The latter entity is being referred as Rendered Service Path (RSP). The main difference between SFP and RSP is that in the former the authority to select the SFF/SF has been delegated to the network. Mirsky, et al. Expires November 4, 2017 [Page 2] Internet-Draft Multi-Layer OAM for SFC May 2017 This document proposes the multi-layer model of SFC Operation, Administration and Maintenance (OAM) and requirements to improve the troubleshooting efficiency. 2. Conventions 2.1. 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]. 2.2. Terminology Unless explicitly specified in this document, active OAM in SFC and SFC OAM are being used interchangeably. e2e: End-to-End FM: Fault Management OAM: Operations, Administration, and Maintenance RDI: Remote Defect Indication RSP: Rendered Service Path SF: Service Function SFC: Service Function Chain SFF: Service Function Forwarder SFP: Service Function Path 3. Multi-layer Model of SFC OAM As described in [I-D.ietf-sfc-oam-framework], multiple layers come into play to realize the SFC, including the Service layer, the underlying Network layer, as well as the Link layer, which are depicted in Figure 1: o The Service layer consists of classifiers and/or service functions/SFs. o Network and Transport layers leverage various overlay network technologies interconnecting SFs to establish SFP. Mirsky, et al. Expires November 4, 2017 [Page 3] Internet-Draft Multi-Layer OAM for SFC May 2017 o The Link layer is technology specific and reflects the technology used in the underlay network. +---+ +---+ +---+ +---+ +---+ |SF1| |SF2| |SF3| |SF4| |SF5| +---+ +---+ +---+ +---+ +---+ \ / \ / | +----------+ +----+ +----+ +----+ |Classifier|-------|SFF1|---------|SFF2|--------|SFF3| +----------+ +----+ +----+ +----+ 0---------------------------------------------0 Service layer 0----------------0--------------0-------------0 Network layer 0-------------0------0-------0------0---------0 Link layer Figure 1: SFC OAM Multi-Layer model 4. Requirements for SFC OAM Multi-layer Model To perfrom the OAM task of fault management (FM) in an SFC, that inculdes failure detection, defect characterzation and localization, this document defines the multi-layer model of OAM, presented in Section 3, and set of requirements towards active OAM mechanisms to be used on an SFC. In example presented in Figure 1 the service SFP1 may be realized through two RSPs, RSP1(SF1--SF3--SF5) and RSP2(SF2--SF4--SF6). To perform end-to-end (e2e) FM SFC OAM: REQ#1: Packets of active OAM in SFC SHOULD be fate sharing with data traffic, i.e. in-band with the monitored traffic, i.e. follow exactly the same RSP, in forward direction, i.e. from ingress toward egress end point(s) of the OAM test. REQ#2: SFC OAM MUST support pro-active monitoring of any element in the SFC availability. The egress, SFF3 in example in Figure 1, is the entity that detects the failure of the SFC. It must be able to signal the new defect state to the ingress, i.e. SFF1. Hence the following requirement: REQ#3: SFC OAM MUST support Remote Defect Indication (RDI) notification by egress to the ingress, i.e. source of continuity checking. Mirsky, et al. Expires November 4, 2017 [Page 4] Internet-Draft Multi-Layer OAM for SFC May 2017 REQ#4: SFC OAM MUST support connectivity verification. Definition of mis-connectivity defect entry and exit criteria are outside the scope of this document. Once the SFF1 detects the defect objective of OAM switches from failure detection to defect characterization and localization. REQ#5: SFC OAM MUST support fault localization of Loss of Continuity check in the SFC. REQ#6: SFC OAM MUST support tracing an SFP in order to realize the RSP. It is practical, as presented in Figure 1, that several SFs share the same SFF. In such case SFP1 may be realized over two RSPs, RSP1(SF1--SF3--SF5) and RSP2(SF2--SF4--SF6). REQ#7: SFC OAM MUST have the ability to discover and exercise all available RSPs in the transport network. In process of localizing the SFC failure separating SFC OAM layers is very attractive and efficient approach. To achieve that continuity among SFFs that are part of the same SFP should be verified. Once SFFs reacheability along the particular SFP has been confirmed task of defect localization may focus on SF reacheability verification. Because reacheability of SFFs has already been verified, SFF local to the SF may be used as source. REQ#8: SFC OAM MUST be able to trigger on-demand FM with responses being directed towards initiator of such proxy request. By using the multi-layer model OAM that confirms to the above listed requirements is capable to perform efficient defect localization on an SFC. 5. SFC OAM multi-layer model Figure 2 presents a use case of applying the proposed SFC OAM multi- layer model. In this scenario operator needs to discover SFFs and SFs of the same SFC. The Layer 1 includes the SFFs that are part of the SFP. The Layer 2 - the SFs along the RSP. When trying to do SFC OAM, classifier or service nodes select and confirm which SFC OAM layering they plan to do, then encapsulate the layering information in the SFC OAM packets, and send the SFC OAM packets along the service function paths to the destination. When receiving the SFC OAM packets, service nodes analyze the layering information and then decide whether sending these packets to next SFFs directly without Mirsky, et al. Expires November 4, 2017 [Page 5] Internet-Draft Multi-Layer OAM for SFC May 2017 being processed by SFs for Layer 1 process or sending to SFs for Layer 2 process. +---+ +---+ +----+ +----+ +-----+ +-----+ +------+ +------+ |SF1|.|SFn| |SF1'|.|SFn'| |SF1''|.|SFn''| |SF1'''|.|SFn'''| +---+ +---+ +----+ +----+ +-----+ +-----+ +------+ +------+ \ / \ / | \ / \ / | +------+ +----+ +----+ | +-----+ +-----+ | |Class.|---|SFF1| ... |SFFn| | |SFF1'| ... |SFFn'| | +------+ +----+ +----+ | +-----+ +-----+ | | | | | | | | | |----|------Layer 1---------------| | | | |-------------Layer 2-------------| Figure 2: SFC OAM multi-layering model 6. Gap analysis Based on the proposed multi-layer model and the listed requirements the following new on-demand functions been defined: 7. Security Considerations It will be considered in a future revision. 8. IANA Considerations It will be considered in a future revision. 9. References 9.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . 9.2. Informative References Mirsky, et al. Expires November 4, 2017 [Page 6] Internet-Draft Multi-Layer OAM for SFC May 2017 [I-D.ietf-sfc-oam-framework] Aldrin, S., Krishnan, R., Akiya, N., Pignataro, C., and A. Ghanwani, "Service Function Chaining Operation, Administration and Maintenance Framework", draft-ietf-sfc- oam-framework-01 (work in progress), February 2016. [RFC7665] Halpern, J., Ed. and C. Pignataro, Ed., "Service Function Chaining (SFC) Architecture", RFC 7665, DOI 10.17487/RFC7665, October 2015, . Authors' Addresses Greg Mirsky ZTE Corp. Email: gregimirsky@gmail.com Wei Meng ZTE Corporation No.50 Software Avenue, Yuhuatai District Nanjing China Email: meng.wei2@zte.com.cn,vally.meng@gmail.com Bhumip Khasnabish ZTE TX, Inc. 1900 McCarthy Blvd, Suite 205 Milpitas, CA 95035 USA Email: vumip1@gmail.com, bhumip.khasnabish@ztetx.com Cui Wang Email: lindawangjoy@gmail.com Mirsky, et al. Expires November 4, 2017 [Page 7]