Network Working Group B. Carpenter Internet-Draft Univ. of Auckland Intended status: Informational S. Jiang Expires: July 10, 2017 Huawei Technologies Co., Ltd January 6, 2017 Guidelines for Autonomic Service Agents draft-carpenter-anima-asa-guidelines-01 Abstract This document proposes guidelines for the design of Autonomic Service Agents for autonomic networks. It is based on the Autonomic Network Infrastructure outlined in the ANIMA reference model, making use of the Autonomic Control Plane and the Generic Autonomic Signaling Protocol. 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 July 10, 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 to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of Carpenter & Jiang Expires July 10, 2017 [Page 1] Internet-Draft ASA Guidelines January 2017 the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Logical Structure of an Autonomic Service Agent . . . . . . . 3 3. Interaction with the Autonomic Networking Infrastructure . . 4 3.1. Interaction with the security mechanisms . . . . . . . . 4 3.2. Interaction with the Autonomic Control Plane . . . . . . 5 3.3. Interaction with GRASP and its API . . . . . . . . . . . 5 3.4. Interaction with Intent mechanism . . . . . . . . . . . . 6 4. Design of GRASP Objectives . . . . . . . . . . . . . . . . . 6 5. Life Cycle . . . . . . . . . . . . . . . . . . . . . . . . . 7 6. Coordination . . . . . . . . . . . . . . . . . . . . . . . . 7 7. Security Considerations . . . . . . . . . . . . . . . . . . . 7 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7 9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 8 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 8 10.1. Normative References . . . . . . . . . . . . . . . . . . 8 10.2. Informative References . . . . . . . . . . . . . . . . . 8 Appendix A. Change log [RFC Editor: Please remove] . . . . . . . 9 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10 1. Introduction This document proposes guidelines for the design of Autonomic Service Agents (ASAs) in the context of an Autonomic Network (AN) based on the Autonomic Network Infrastructure (ANI) outlined in the ANIMA reference model [I-D.ietf-anima-reference-model]. This infrastructure makes use of the Autonomic Control Plane (ACP) [I-D.ietf-anima-autonomic-control-plane] and the Generic Autonomic Signaling Protocol (GRASP) [I-D.ietf-anima-grasp]. There is a considerable literature about autonomic agents with a variety of proposals about how they should be characterized. Some examples are [DeMola06], [Huebscher08], [Movahedi12] and [GANA13]. However, for the present document, the basic definitions and goals for autonomic networking given in [RFC7575] apply . According to RFC 7575, an Autonomic Service Agent is "An agent implemented on an autonomic node that implements an autonomic function, either in part (in the case of a distributed function) or whole." The reference model [I-D.ietf-anima-reference-model] expands this by adding that an ASA is "a process that makes use of the features provided by the ANI to achieve its own goals, usually including interaction with other ASAs via the GRASP protocol [I-D.ietf-anima-grasp] or otherwise. Of course it also interacts Carpenter & Jiang Expires July 10, 2017 [Page 2] Internet-Draft ASA Guidelines January 2017 with the specific targets of its function, using any suitable mechanism. Unless its function is very simple, the ASA will need to be multi-threaded so that it can handle overlapping asynchronous operations. It may therefore be a quite complex piece of software in its own right, forming part of the application layer above the ANI." A basic property of an ASA is that it is a relatively complex software component that will in many cases control and monitor simpler entities in the same host or elsewhere. For example, a device controller that manages tens or hundreds of simple devices might contain a single ASA. The remainder of this document offers guidance on the design of ASAs. 2. Logical Structure of an Autonomic Service Agent As mentioned above, all but the simplest ASAs will be multi-threaded programs. A typical ASA will have a main thread that performs various initial housekeeping actions such as: o Obtain authorization credentials. o Register the ASA with GRASP. o Acquire relevant policy Intent. o Define data structures for relevant GRASP objectives. o Register with GRASP those objectives that it will actively manage. o Launch a self-monitoring thread. o Enter its main loop. The logic of the main loop will depend on the details of the autonomic function concerned. Whenever asynchronous operations are required, extra threads will be launched. Examples of such threads include: o A background thread to repeatedly flood an objective to the AN, so that any ASA can receive the objective's latest value. o A thread to accept incoming synchronization requests for an objective managed by this ASA. Carpenter & Jiang Expires July 10, 2017 [Page 3] Internet-Draft ASA Guidelines January 2017 o A thread to accept incoming negotiation requests for an objective managed by this ASA, and then to conduct the resulting negotiation with the counterpart ASA. o A thread to manage subsidiary non-autonomic devices directly. These threads should all either exit after their job is done, or enter a wait state for new work, to avoid blocking other threads unnecessarily. Note: Possibly an 'event loop' style of implementation could be adopted in place of true multi-threading, in which case each of these threads would be implemented as an event handler. According to the degree of parallelism needed by the application, some of these threads might be launched in multiple instances. In particular, if negotiation sessions with other ASAs are expected to be long or to involve wait states, the ASA designer might allow for multiple simultaneous negotiating threads, with appropriate use of queues and locks to maintain consistency. The main loop itself could act as the initiator of synchronization requests or negotiation requests, when the ASA needs data or resources from other ASAs. In particular, the main loop should watch for changes in policy Intent that affect its operation. It should also do whatever is required to avoid unnecessary resource consumption, such as including an arbitrary wait time in each cycle of the main loop. The self-monitoring thread is of considerable importance. Autonomic service agents must never fail. To a large extent this depends on careful coding and testing, with no unhandled error returns or exceptions, but if there is nevertheless some sort of failure, the self-monitoring thread should detect it, fix it if possible, and in the worst case restart the entire ASA. 3. Interaction with the Autonomic Networking Infrastructure 3.1. Interaction with the security mechanisms An ASA by definition runs in an autonomic node. Before any normal ASAs are started, such nodes must be bootstrapped into the autonomic network's secure key infrastructure in accordance with [I-D.ietf-anima-bootstrapping-keyinfra]. This key infrastructure will be used to secure the ACP (next section) and may be used by ASAs to set up additional secure interactions with their peers, if needed. Carpenter & Jiang Expires July 10, 2017 [Page 4] Internet-Draft ASA Guidelines January 2017 Note that the secure bootstrap process itself may include special- purpose ASAs that run in a constrained insecure mode. 3.2. Interaction with the Autonomic Control Plane In a normal autonomic network, ASAs will run as clients of the ACP. It will provide a fully secured network environment for all communication with other ASAs, in most cases mediated by GRASP (next section). Note that the ACP formation process itself may include special- purpose ASAs that run in a constrained insecure mode. 3.3. Interaction with GRASP and its API GRASP [I-D.ietf-anima-grasp] is expected to run as a separate process with its API [I-D.liu-anima-grasp-api] available in user space. Thus ASAs may operate without special privilege, unless they need it for other reasons. The ASA's view of GRASP is built around GRASP objectives (Section 4), defined as data structures containing administrative information such as the objective's unique name, and its current value. The format and size of the value is not restricted by the protocol, except that it must be possible to serialise it for transmission in CBOR [RFC7049], which is no restriction at all in practice. The GRASP API offers the following features: o Registration functions, so that an ASA can register itself and the objectives that it manages. o A discovery function, by which an ASA can discover other ASAs supporting a given objective. o A negotiation request function, by which an ASA can start negotiation of an objective with a counterpart ASA. With this, there is a corresponding listening function for an ASA that wishes to respond to negotiation requests, and a set of functions to support negotiating steps. o A synchronization function, by which an ASA can request the current value of an objective from a counterpart ASA. With this, there is a corresponding listening function for an ASA that wishes to respond to synchronization requests. o A flood function, by which an ASA can cause the current value of an objective to be flooded throughout the AN so that any ASA can receive it. Carpenter & Jiang Expires July 10, 2017 [Page 5] Internet-Draft ASA Guidelines January 2017 For further details and some additional housekeeping functions, see [I-D.liu-anima-grasp-api]. This API is intended to support the various interactions expected between most ASAs, such as the interactions outlined in Section 2. However, if ASAs require additional communication between themselves, they can do so using any desired protocol. One option is to use GRASP discovery and synchronization as a rendez-vous mechanism between two ASAs, passing communication parameters such as a TCP port number as the value of a GRASP objective. As noted above, either the ACP or in special cases the autonomic key infrastructure will be used to secure such communications. 3.4. Interaction with Intent mechanism At the time of writing, the Intent mechanism for the ANI is undefined. It is expected to operate by an information distribution mechanism that can reach all autonomic nodes, and therefore every ASA. However, each ASA must be capable of operating "out of the box" in the absence of locally defined Intent, so every ASA implementation must include carefully chosen default values and settings for all parameters and choices that might depend on Intent. 4. Design of GRASP Objectives The general rules for the format of GRASP Objective options, their names, and IANA registration are given in [I-D.ietf-anima-grasp]. Additionally that document discusses various general considerations for the design of objectives, which are not repeated here. However, we emphasize that the GRASP protocol does not provide transactional integrity. In other words, if an ASA is capable of overlapping several negotiations for a given objective, then the ASA itself must use suitable locking techniques to avoid interference between these negotiations. For example, if an ASA is allocating part of a shared resource to other ASAs, it needs to ensure that the same part of the resource is not allocated twice. This might impact the design of the objective as well as the logic flow of the ASA. The actual value field of an objective is limited by the GRASP protocol definition to any data structure that can be expressed in Concise Binary Object Representation (CBOR) [RFC7049]. For some objectives, a single data item will suffice; for example an integer, a floating point number or a UTF-8 string. For more complex cases, a simple tuple structure such as [item1, item2, item3] could be used. Nothing prevents using other formats such as JSON, but this requires the ASA to be capable of parsing and generating JSON. The formats acceptable by the GRASP API will limit the options in practice. A fallback solution is for the API to accept and deliver the value Carpenter & Jiang Expires July 10, 2017 [Page 6] Internet-Draft ASA Guidelines January 2017 field in raw CBOR, with the ASA itself encoding and decoding it via a CBOR library. 5. Life Cycle Autonomic functions could be permanent, in the sense that ASAs are shipped as part of a product and persist throughout the product's life. However, a more likely situation is that ASAs need to be installed or updated dynamically, because of new requirements or bugs. Because continuity of service is fundamental to autonomic networking, the process of seamlessly replacing a running instance of an ASA with a new version needs to be part of the ASA's design. This topic is discussed in detail in "A Day in the Life of an Autonomic Function" [I-D.peloso-anima-autonomic-function]. 6. Coordination Some autonomic functions will be completely independent of each other. However, others are at risk of interfering with each other - for example, two different optimization functions might both attempt to modify the same underlying parameter in different ways. In a complete system, a method is needed of identifying ASAs that might interfere with each other and coordinating their actions when necessary. This issue is considered in "Autonomic Functions Coordination" [I-D.ciavaglia-anima-coordination]. 7. Security Considerations ASAs are intended to run in an environment that is protected by the Autonomic Control Plane [I-D.ietf-anima-autonomic-control-plane], admission to which depends on an initial secure bootstrap process [I-D.ietf-anima-bootstrapping-keyinfra]. However, this does not relieve ASAs of responsibility for security. In particular, when ASAs configure or manage network elements outside the ACP, they must use secure techniques and carefully validate any incoming information. As appropriate to their specific functions, ASAs should take account of relevant privacy considerations [RFC6973]. Authorization of ASAs is a subject for future study. 8. IANA Considerations This document makes no request of the IANA. Carpenter & Jiang Expires July 10, 2017 [Page 7] Internet-Draft ASA Guidelines January 2017 9. Acknowledgements TBD. 10. References 10.1. Normative References [I-D.ietf-anima-autonomic-control-plane] Behringer, M., Eckert, T., and S. Bjarnason, "An Autonomic Control Plane", draft-ietf-anima-autonomic-control- plane-04 (work in progress), October 2016. [I-D.ietf-anima-bootstrapping-keyinfra] Pritikin, M., Richardson, M., Behringer, M., Bjarnason, S., and K. Watsen, "Bootstrapping Remote Secure Key Infrastructures (BRSKI)", draft-ietf-anima-bootstrapping- keyinfra-04 (work in progress), October 2016. [I-D.ietf-anima-grasp] Bormann, C., Carpenter, B., and B. Liu, "A Generic Autonomic Signaling Protocol (GRASP)", draft-ietf-anima- grasp-09 (work in progress), December 2016. [RFC7049] Bormann, C. and P. Hoffman, "Concise Binary Object Representation (CBOR)", RFC 7049, DOI 10.17487/RFC7049, October 2013, . 10.2. Informative References [DeMola06] De Mola, F. and R. Quitadamo, "An Agent Model for Future Autonomic Communications", Proceedings of the 7th WOA 2006 Workshop From Objects to Agents 51-59, September 2006. [GANA13] ETSI GS AFI 002, , "Autonomic network engineering for the self-managing Future Internet (AFI): GANA Architectural Reference Model for Autonomic Networking, Cognitive Networking and Self-Management.", April 2013, . [Huebscher08] Huebscher, M. and J. McCann, "A survey of autonomic computing--degrees, models, and applications", ACM Computing Surveys (CSUR) Volume 40 Issue 3 DOI: 10.1145/1380584.1380585, August 2008. Carpenter & Jiang Expires July 10, 2017 [Page 8] Internet-Draft ASA Guidelines January 2017 [I-D.ciavaglia-anima-coordination] Ciavaglia, L. and P. Peloso, "Autonomic Functions Coordination", draft-ciavaglia-anima-coordination-01 (work in progress), March 2016. [I-D.ietf-anima-reference-model] Behringer, M., Carpenter, B., Eckert, T., Ciavaglia, L., Pierre, P., Liu, B., Nobre, J., and J. Strassner, "A Reference Model for Autonomic Networking", draft-ietf- anima-reference-model-02 (work in progress), July 2016. [I-D.liu-anima-grasp-api] Carpenter, B., Liu, B., Wang, W., and X. Gong, "Generic Autonomic Signaling Protocol Application Program Interface (GRASP API)", draft-liu-anima-grasp-api-02 (work in progress), September 2016. [I-D.peloso-anima-autonomic-function] Pierre, P. and L. Ciavaglia, "A Day in the Life of an Autonomic Function", draft-peloso-anima-autonomic- function-01 (work in progress), March 2016. [Movahedi12] Movahedi, Z., Ayari, M., Langar, R., and G. Pujolle, "A Survey of Autonomic Network Architectures and Evaluation Criteria", IEEE Communications Surveys & Tutorials Volume: 14 , Issue: 2 DOI: 10.1109/SURV.2011.042711.00078, Page(s): 464 - 490, 2012. [RFC6973] Cooper, A., Tschofenig, H., Aboba, B., Peterson, J., Morris, J., Hansen, M., and R. Smith, "Privacy Considerations for Internet Protocols", RFC 6973, DOI 10.17487/RFC6973, July 2013, . [RFC7575] Behringer, M., Pritikin, M., Bjarnason, S., Clemm, A., Carpenter, B., Jiang, S., and L. Ciavaglia, "Autonomic Networking: Definitions and Design Goals", RFC 7575, DOI 10.17487/RFC7575, June 2015, . Appendix A. Change log [RFC Editor: Please remove] draft-carpenter-anima-asa-guidelines-01, 2017-01-06: More sections filled in draft-carpenter-anima-asa-guidelines-00, 2016-09-30: Carpenter & Jiang Expires July 10, 2017 [Page 9] Internet-Draft ASA Guidelines January 2017 Initial version Authors' Addresses Brian Carpenter Department of Computer Science University of Auckland PB 92019 Auckland 1142 New Zealand Email: brian.e.carpenter@gmail.com Sheng Jiang Huawei Technologies Co., Ltd Q14, Huawei Campus, No.156 Beiqing Road Hai-Dian District, Beijing, 100095 P.R. China Email: jiangsheng@huawei.com Carpenter & Jiang Expires July 10, 2017 [Page 10]