DECADE R. Alimi Internet-Draft Google Intended status: Informational Y. Yang Expires: April 21, 2011 Yale University A. Rahman InterDigital Communications, LLC D. Kutscher NEC Laboratories Europe L. Chen H. Liu Yale University October 18, 2010 DECADE Architecture draft-alimi-decade-arch-00 Abstract Peer-to-peer (P2P) applications have become widely used on the Internet today and make up a large portion of the traffic in many networks. In P2P applications, one technique for reducing the total amount of P2P traffic is to introduce storage capabilities within the network. The DECADE Working Group has been formed with the goal of developing an architecture to provide this capability. This documents presents an architecture, discusses the underlying principles and identifies core components and protocols supporting the architecture. Status of this Memo This Internet-Draft is submitted to IETF in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. 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." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at Alimi, et al. Expires April 21, 2011 [Page 1] Internet-Draft DECADE Architecture October 2010 http://www.ietf.org/shadow.html. This Internet-Draft will expire on April 21, 2011. Copyright Notice Copyright (c) 2010 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 BSD License. Alimi, et al. Expires April 21, 2011 [Page 2] Internet-Draft DECADE Architecture October 2010 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Entities . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 2.1. DECADE Storage Servers . . . . . . . . . . . . . . . . . . 5 2.2. DECADE Storage Provider . . . . . . . . . . . . . . . . . 5 2.3. Content Distribution Application . . . . . . . . . . . . . 5 2.4. DECADE Content Providers . . . . . . . . . . . . . . . . . 5 2.5. DECADE Content Consumers . . . . . . . . . . . . . . . . . 5 2.6. End-Point . . . . . . . . . . . . . . . . . . . . . . . . 6 3. Architectural Principles . . . . . . . . . . . . . . . . . . . 6 3.1. Decoupled Control and Data Planes . . . . . . . . . . . . 6 3.2. Immutable Data Objects . . . . . . . . . . . . . . . . . . 7 3.3. Accessing Data Objects . . . . . . . . . . . . . . . . . . 8 3.4. Data Object Identifiers . . . . . . . . . . . . . . . . . 8 3.5. Explicit Control . . . . . . . . . . . . . . . . . . . . . 8 3.6. Resource and Data Access Control through User Delegation . . . . . . . . . . . . . . . . . . . . . . . . 8 3.6.1. Resource Allocation . . . . . . . . . . . . . . . . . 9 3.6.2. User Delegations . . . . . . . . . . . . . . . . . . . 9 4. System Components . . . . . . . . . . . . . . . . . . . . . . 9 5. Reference Architecture . . . . . . . . . . . . . . . . . . . . 10 6. Security Considerations . . . . . . . . . . . . . . . . . . . 10 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10 8. Informative References . . . . . . . . . . . . . . . . . . . . 10 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 10 Alimi, et al. Expires April 21, 2011 [Page 3] Internet-Draft DECADE Architecture October 2010 1. Introduction Peer-to-peer (P2P) applications have become widely used on the Internet today to distribute contents, and they contribute a large portion of the traffic in many networks. The DECADE Working Group has been formed with the goal of developing an architecture to introduce in-network storage to be used by such applications, to achieve more efficient content distribution. Specifically, in many subscriber networks, it is typically more expensive to upgrade network equipment in the "last-mile", because it can involve replacing equipment and upgrading wiring at individual homes, businesses, and devices such as DSLAMs and CMTSs. Thus, it can be cheaper to upgrade core infrastructure involving fewer components that are shared by many subscribers. See [I-D.ietf-decade-problem-statement] for a more complete discussion of the problem domain and general discussion of the capabilities to be provided by DECADE. This document presents a potential architecture of providing in- network storage that can be integrated into content distribution applications. The primary focus is P2P-based content distribution, but the architecture may be useful to other applications with similar characteristics and requirements. In particular, content distribution applications that may split data into smaller pieces for distribution may be able to utilize DECADE. The design philosophy of the DECADE architecture is to provide only the core functionality that is needed for applications to make use of in-network storage. With such core functionality, the protocol may be simple and easier to support by storage providers. If more complex functionality is needed by a certain application or class of applications, it may be layered on top of the DECADE protocol. The DECADE protocol will leverage existing transport and application layer protocols and will be designed to work with a small set of alternative IETF protocols. This document proceeds in two steps. First, it details the core architectural principles that can guide the DECADE design. Next, given these core principles, this document presents the core components of the DECADE architecture and identifies usage of existing protocols and where there is a need for new protocol development. This document will be updated to track the progress of the DECADE survey [I-D.ietf-decade-survey] and requirements [I-D.gu-decade-reqs] drafts. Alimi, et al. Expires April 21, 2011 [Page 4] Internet-Draft DECADE Architecture October 2010 2. Entities 2.1. DECADE Storage Servers DECADE storage servers are operated by DECADE storage providers and provide the DECADE functionality as specified in this memo, including mechanisms to store, retrieve and manage data. A storage provider will typically operate many storage servers. 2.2. DECADE Storage Provider A DECADE in-storage provider deploys and/or manages DECADE servers within a network. Storage providers may also own or manage the network in which the DECADE servers are deployed. A storage provider, possibly in cooperation with one or more network providers, determines deployment locations for DECADE servers and determines the available resources for each. 2.3. Content Distribution Application A content distribution application is developed by an Application Developer and installed on end-hosts. End-hosts may be machines managed by the Application Developer itself, a Content Provider, or an End-User. 2.4. DECADE Content Providers DECADE content providers access DECADE storage servers (by way of a DECADE client) to upload and manage data in the context of an context distribution application. A content provider can access one or more storage servers. A content provider may be a single process or a distributed application (in a P2P scenario). 2.5. DECADE Content Consumers DECADE content consumers access storage servers (by way of a DECADE client) to download data that has previously been stored by a content provider in the context of a content distribution application. A content consumer can access one more storage servers. A content consumer may be a single process or a distributed application (in a P2P scenario). An instance of a distributed application, such as a P2P application, may both provide content to and consume content from DECADE storage servers. Alimi, et al. Expires April 21, 2011 [Page 5] Internet-Draft DECADE Architecture October 2010 2.6. End-Point An End-Point is an instance of a Content Distribution Application that includes a DECADE client. A particular End-Point may be a DECADE Content Provider, DECADE Content Consumer, or both. An End-Point need not be an active member of a "swarm" to interact with the DECADE storage system. That is, an End-Point may interact with the DECADE storage servers as an offline activity. 3. Architectural Principles We identify the following key principles. 3.1. Decoupled Control and Data Planes The DECADE infrastructure is intended to support multiple content distribution applications. A complete content distribution application implements of a set of control functions including content search, indexing and collection, access control, ad insertion, replication, request routing, and QoS scheduling. Different content distribution applications can have unique considerations designing the control and signaling functions. For example, a major competitive advantage of many successful P2P systems is their substantial expertise in how to most efficiently utilize peer and infrastructural resources. Many live P2P systems have their specific algorithms in selecting the peers that behave as the more stable, higher-bandwidth sources. They continue to fine-tune such algorithms. In other words, in-network storage should export basic mechanisms and allow as much flexibility as possible to the control planes to implement specific policies. This conforms to the end-to- end systems principle and allows innovation and satisfaction of specific business goals. Specifically, in the DECADE architecture, the control plane focuses on the application-specific, complex, and/or processing intensive functions while the data plane provides storage and data transport functions. o Control plane: Signals on which data are downloaded to whom, from where, at what time, and with what quality-of-service (e.g., bandwidth). It also provides higher layer meta-data management functions such as defining the sequence of data blocks forming a higher layer content object. These are behaviors designed and implemented by the Application. Alimi, et al. Expires April 21, 2011 [Page 6] Internet-Draft DECADE Architecture October 2010 o Data plane: Stores and transfers data as instructed by the Application's Control Plane. Decoupling control plane and data plane is not new. For example, OpenFlow is an implementation of this principle for Internet routing, where the computation of the forwarding table and the application of the forwarding table are separated. Google File System applies the principle to file system design, by utilizing the Master to handle the meta-data management, and the chunk servers to handle the data plane (i.e., read and write of chunks of data). NFS4 also implements this principle. Note that applications may have different Data Plane implementations in order to support particular requirements (e.g., low latency). In order to provide interoperability, the DECADE architecture does not intend to enable arbitrary data transport protocols between DECADE servers. However, the architecture should allow for multiple data transport protocols to be used. Also note that although an application's existing control plane functions remain implemented within the application, the particular implementation may need to be adjusted to support DECADE. 3.2. Immutable Data Objects A property of bulk contents to be distributed is that they typically are immutable -- once a piece of content is generated, it is typically not modified. It is not common that bulk contents such as video frames and images need to be modified after distribution. Many content distribution applications divide content objects into blocks for two reasons: (1) different blocks may be fetched from different content sources in parallel, and (2) individual blocks may be recovered from an alternate content source. Typically, applications use a block size larger than a single packet in order to reduce control overhead. Common applications whose content matches this model include P2P streaming (live and video-on-demand) and P2P file-sharing content. However, other types of applications may additionally match this model. DECADE adopts a design in which immutable data objects may be stored at a storage server. Applications may consider existing blocks as DECADE data objects, or or they may adjust block sizes before storing in a DECADE server. Focusing on immutable data blocks in the data plane can substantially Alimi, et al. Expires April 21, 2011 [Page 7] Internet-Draft DECADE Architecture October 2010 simplify the data plane design, since consistency requirements can be relaxed. It also allows effective reuse of data blocks and de- duplication of redundant data. Note that immutable content may still be deleted. If applications require particular content to be modified, one possibility is to delete (or revoke access to) the existing content and then distribute a different version. 3.3. Accessing Data Objects The DECADE data access protocol allows clients to store and retrieve data fragments ("data objects") of arbitrary size. The DECADE architecture is agnostic to application-specific framing conventions, unfiform fragment lengths etc. 3.4. Data Object Identifiers Objects that are stored in a DECADE storage server can be accessed by DECADE content consumers by a resource identifiers that has been assigned within a certain application context. Because a DECADE content consumer can access more than one storage server within a single application context, a data object that is replicated across different storage servers managed by a DECADE storage provider, can be accessed by a single identifier. 3.5. Explicit Control To support the functions of an application's control plane, applications must be able to know and control which data is stored at particular locations. Thus, in contrast with content caches, applications are given explicit control over the placement (selection of a a DECADE server), deletion (or expiration policy), and access control for stored data. Consider deletion/expiration policy as a simple example. Applications may require a DECADE server to store content for a relatively short period of time (e.g. for live-streaming data) or may need to store content long term (e.g., for video-on-demand). 3.6. Resource and Data Access Control through User Delegation DECADE provides a shared infrastructure to be used by multiple tenants of multiple content distribution applications. Thus, it needs to provide both resource and data access control. Alimi, et al. Expires April 21, 2011 [Page 8] Internet-Draft DECADE Architecture October 2010 3.6.1. Resource Allocation There are two primary interacting entities in the DECADE architecture. First, Storage Providers control where DECADE storage servers are provisioned and their total available resources. Second, Applications executing on end-points control data transfers amongst available DECADE servers and between DECADE servers and end-points. A form of isolation is required to enable concurrently-running Applications to each explicitly manage their own content and share of resources at the available servers. Management of the resources at a server are delegated by a Storage Provider to one or more applications. Applications are able to explicitly and independently manage their own share of resources. 3.6.2. User Delegations Storage providers have the ability to explicitly manage the entities allowed to utilize the resources at a DECADE server. This capability is needed for reasons such as capacity-planning and legal considerations in certain deployment scenarios. To provide a scalable way to manage applications granted resources at a DECADE server, a layer of indirection is added. Instead of granting resources to an application, the DECADE server grants a share of the resources to a user. The user may in turn share the granted resources amongst multiple applications. The share of resources granted by a storage provider is called a User Delegation. A User Delegation may be granted to an end-user (e.g., an ISP subscriber), a Content Provider, or an Application Provider. A particular instance of an application may make use of the storage resources: o granted to the end-user (with the end-user's permission), o granted to the Content Provider (with the Content Provider's permission>, and/or o granted to the Application Provider. 4. System Components The current version of the document has primarily focused on the architectural principles. The detailed system components will be discussed in the next document revision. Alimi, et al. Expires April 21, 2011 [Page 9] Internet-Draft DECADE Architecture October 2010 5. Reference Architecture The current version of the document has primarily focused on the architectural principles. The detailed reference architecture will be discussed in the next document revision. 6. Security Considerations This document currently does not contain any security considerations beyond those mentioned in [I-D.ietf-decade-problem-statement]. 7. IANA Considerations This document does not have any IANA considerations. 8. Informative References [I-D.ietf-decade-problem-statement] Yongchao, S., Zong, N., Yang, Y., and R. Alimi, "DECoupled Application Data Enroute (DECADE) Problem Statement", draft-ietf-decade-problem-statement-00 (work in progress), August 2010. [I-D.ietf-decade-survey] Alimi, R., Rahman, A., and Y. Yang, "A Survey of In- network Storage Systems", draft-ietf-decade-survey-00 (work in progress), September 2010. [I-D.gu-decade-reqs] Yingjie, G., Bryan, D., Yang, Y., and R. Alimi, "DECADE Requirements", draft-gu-decade-reqs-05 (work in progress), July 2010. Authors' Addresses Richard Alimi Google Email: ralimi@google.com Alimi, et al. Expires April 21, 2011 [Page 10] Internet-Draft DECADE Architecture October 2010 Y. Richard Yang Yale University Email: yry@cs.yale.edu Akbar Rahman InterDigital Communications, LLC Email: akbar.rahman@interdigital.com Dirk Kutscher NEC Laboratories Europe Email: dirk.kutscher@neclab.eu Lijiang Chen Yale University Email: lijiang.chen@yale.edu Hongqiang Liu Yale University Email: hongqiang.liu@yale.edu Alimi, et al. Expires April 21, 2011 [Page 11]