DECADE                                                             Y. Gu
Internet-Draft                                                    Huawei
Intended status: Informational                                  D. Bryan
Expires: September 15, November 18, 2011                    Cogent Force, LLC / Huawei
                                                                 Y. Yang
                                                         Yale University
                                                                R. Alimi
                                                                  Google
                                                          March 14,
                                                            May 17, 2011

                          DECADE Requirements
                       draft-ietf-decade-reqs-01
                       draft-ietf-decade-reqs-02

Abstract

   The target of DECoupled Application Data Enroute (DECADE) is to
   provide an open and standard in-network storage system for
   applications, primarily P2P applications, to store, retrieve and
   manage their data.  This draft enumerates and explains requirements,
   not only for store and retrieve, but also for data management, access
   control and resource control, that should be considered during the
   design and implementation of a DECADE system.  These are requirements
   on the entire system; some of the requirements may eventually be
   implemented by an existing protocol with/without some extensions
   (e.g., the data transport level).  A user of DECADE as a complete
   architecture would be guaranteed complete functionality.

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 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
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   This Internet-Draft will expire on September 15, November 18, 2011.

Copyright Notice

   Copyright (c) 2011 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
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   described in the BSD License.

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  5
   2.  Terminology and Concepts . . . . . . . . . . . . . . . . . . .  5
   3.  Requirements Structure . . . . . . . . . . . . . . . . . . . .  6
   4.  Protocol Requirements  . . . . . . . . . . . . . . . . . . . .  7
     4.1.  Requirements . . . . . . . . . . . . . . . . . . . . . . .  7
       4.1.1.  Overall Protocol Requirements  . . . . . . . . . . . .  7
         4.1.1.1.  Cross-platform Access  . . . . . . . . . . . . . .  7
         4.1.1.2.  Connectivity Concerns  . . . . . . . . . . . . . .  7
           4.1.1.2.1.  NATs and Firewalls . . . . . . . . . . . . . .  7
           4.1.1.2.2.  Connections to Clients . . . . . . . . . . . .  7
         4.1.1.3.  Security . . . . . . . . . . . . . . . . . . . . .  8
           4.1.1.3.1.  Secure Transport . . . . . . . . . . . . . . .  8
           4.1.1.3.2.  Connections to Clients . . . . . . . . . . . .  8
         4.1.1.4.  Error and Failure Conditions . . . . . . . . . . .  8
           4.1.1.3.1.
           4.1.1.4.1.  Overload Condition . . . . . . . . . . . . . .  8
           4.1.1.3.2.
           4.1.1.4.2.  Insufficient Resources . . . . . . . . . . . .  8
           4.1.1.3.3.
           4.1.1.4.3.  Unavailable and Deleted Data . . . . . . . . .  8
           4.1.1.3.4.  9
           4.1.1.4.4.  Redirection  . . . . . . . . . . . . . . . . .  9
       4.1.2.  Transfer and Latency Requirements  . . . . . . . . . .  9
         4.1.2.1.  Low-Latency Access . . . . . . . . . . . . . . . .  9
         4.1.2.2.  Indirect Transfer  . . . . . . . . . . . . . . . .  9 10
         4.1.2.3.  Data Object Size . . . . . . . . . . . . . . . . . 10
         4.1.2.4.  Communication among In-network Storage Elements  . 10
       4.1.3.  Data Access Requirements . . . . . . . . . . . . . . . 10 11
         4.1.3.1.  Reading/Writing Own Storage  . . . . . . . . . . . 10 11
         4.1.3.2.  Access by Other Users  . . . . . . . . . . . . . . 10 11
         4.1.3.3.  Negotiable Data Protocol . . . . . . . . . . . . . 11
         4.1.3.4.  Separation of Data Operations from Application
                   Control  . . . . . . . . . . . . . . . . . . . . . 11 12
       4.1.4.  Data Management Requirements . . . . . . . . . . . . . 12
         4.1.4.1.  Agnostic of reliability  . . . . . . . . . . . . . 12
         4.1.4.2.  Time-to-live for Stored Data . . . . . . . . . . . 12 13
         4.1.4.3.  Offline Usage  . . . . . . . . . . . . . . . . . . 12 13
       4.1.5.  Data Naming Requirements . . . . . . . . . . . . . . . 13
         4.1.5.1.  Unique Names . . . . . . . . . . . . . . . . . . . 13
       4.1.6.  Resource Control . . . . . . . . . . . . . . . . . . . 12
         4.1.5.1. 14
         4.1.6.1.  Multiple Applications  . . . . . . . . . . . . . . 12
         4.1.5.2. 14
         4.1.6.2.  Per-Remote-Client, Per-Data Control  . . . . . . . 13
         4.1.5.3. 14
         4.1.6.3.  Server Involvement . . . . . . . . . . . . . . . . 13
       4.1.6. 15
       4.1.7.  Authorization  . . . . . . . . . . . . . . . . . . . . 14
         4.1.6.1. 15
         4.1.7.1.  Per-Remote-Client, Per-Data Read Access  . . . . . 14
         4.1.6.2. 15
         4.1.7.2.  Per-User Write Access  . . . . . . . . . . . . . . 14
         4.1.6.3. 15
         4.1.7.3.  Authorization Checks . . . . . . . . . . . . . . . 15
         4.1.6.4. 16
         4.1.7.4.  Credentials Not IP-Based . . . . . . . . . . . . . 15
         4.1.6.5. 16
         4.1.7.5.  Server Involvement . . . . . . . . . . . . . . . . 15 16
   5.  Storage  Discovery Requirements . . . . . . . . . . . . . . . . . . . . . 15 16
     5.1.  Requirements . . . . . . . . . . . . . . . . . . . . . . . 15 16
       5.1.1.  Locating DECADE Servers  . . . . . . . . . . . . . . . 17
       5.1.2.  Support for Clients Behind NATs and Firewalls  . . . . 17
       5.1.3.  Prefer Existing Protocols  . . . . . . . . . . . . . . 17
   6.  Storage Requirements . . . . . . . . . . . . . . . . . . . . . 17
     6.1.  Requirements . . . . . . . . . . . . . . . . . . . . . . . 17
       6.1.1.  Explicit Deletion of Stored Data . . . . . . . . . . . 15
       5.1.2. 17
       6.1.2.  Multiple writing . . . . . . . . . . . . . . . . . . . 16
       5.1.3. 18
       6.1.3.  Multiple reading . . . . . . . . . . . . . . . . . . . 16
       5.1.4. 18
       6.1.4.  Reading before completely written  . . . . . . . . . . 16
       5.1.5. 18
       6.1.5.  Hints concerning usage stored data . . . . . . . . . . 16
       5.1.6. 18
       6.1.6.  Writing model  . . . . . . . . . . . . . . . . . . . . 17
       5.1.7. 19
       6.1.7.  Storage Status . . . . . . . . . . . . . . . . . . . . 17
     5.2. 19
     6.2.  Non-Requirements . . . . . . . . . . . . . . . . . . . . . 17
       5.2.1. 19
       6.2.1.  No ability to update . . . . . . . . . . . . . . . . . 18
   6. 20
   7.  Implementation Considerations  . . . . . . . . . . . . . . . . 18
     6.1. 20
     7.1.  Resource Scheduling  . . . . . . . . . . . . . . . . . . . 18
     6.2. 20
     7.2.  Removal of Duplicate Records . . . . . . . . . . . . . . . 18
   7. 20
   8.  Discussion and Open Issues . . . . . . . . . . . . . . . . . . 19
     7.1. 21
     8.1.  Discussion . . . . . . . . . . . . . . . . . . . . . . . . 19
     7.2. 21
     8.2.  Open Issues  . . . . . . . . . . . . . . . . . . . . . . . 19
   8. 21
   9.  Security Considerations  . . . . . . . . . . . . . . . . . . . 20
   9. 22
   10. IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 20
   10. 22
   11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 20
     10.1. 22
     11.1. Normative References . . . . . . . . . . . . . . . . . . . 20
     10.2. 22
     11.2. Informative References . . . . . . . . . . . . . . . . . . 20 22
   Appendix A.  Acknowledgments . . . . . . . . . . . . . . . . . . . 20 22
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 21 23

1.  Introduction

   The object of DECoupled Application Data Enroute (DECADE) is to
   provide an open and standard in-network storage system for
   applications, primarily applications that could be implemented using
   a content distribution paradigm, where data is broken in to one or
   more chunks and then distributed.  This may already include many
   types of applications including P2P applications, IPTV, and VoD.
   Instead of always transferring data directly from a source/owner
   client to a requesting client, the source/owner client can store and
   manage its content on its in-network storage.  The requesting client
   can get the address of the in-network storage pertaining to the
   source/owner client and retrieve data from the storage.

   This draft enumerates and explains the rationale behind SPECIFIC
   requirements on the protocol design and on any data store
   implementation that may be used to implement DECADE servers that
   should be considered during the design and implementation of a DECADE
   system.  As such, it DOES NOT include general guiding principals.
   General design considerations, explanation of the problem being
   addressed, and enumeration of the types of applications to which
   DECADE may be suited is not considered in this document.  For general
   information, please see the problem statement
   [I-D.ietf-decade-problem-statement] and architecture drafts.

   This document enumerates the requirements to enable target
   applications to utilize in-network storage.  In this context, using
   storage resources includes not only basic capabilities such as
   storing and retrieving data, and managing data, but also (1)
   controlling access for particular remote clients with which it is
   sharing data and (2) controlling the resources used by remote clients
   when they access data.

2.  Terminology and Concepts

   This document uses terms defined in
   [I-D.ietf-decade-problem-statement].  In particular, IAP refers to
   the In-network storage Access Protocol, which is the protocol used to
   communicate between a DECADE client and DECADE server (in-network
   storage) for access control and resource control.

   This document also defines additional terminology:

   Target Application: An application (typically installed at end-hosts)
   with the ability to explicitly control usage of network and/or
   storage resources to deliver contents to a large number of users.
   This includes scenarios where multiple applications or entities
   cooperate, such as with P2P/CDN hybrid architectures.  Such
   applications distribute large contents (e.g., a large file, or video
   stream) by dividing the contents into smaller blocks for more
   flexible distribution (e.g., multipath).  The distributed content is
   typically immutable (though it may be deleted).  We use the term
   Target Application to refer to the type of applications that are
   explicitly (but not exclusively) supported by DECADE.

3.  Requirements Structure

   The DECADE protocol is intended to sit between Target Applications
   and a back-end storage system.  In the development of DECADE, it must
   be made clear that the intention is to NOT develop yet another
   storage system, but rather to create a protocol that enables Target
   Applications to make use of storage within the network, leaving
   specific storage system considerations to the implementation of the
   DECADE servers as much as possible.  For this reason, we have divided
   the requirements into two categories:

   o  Protocol Requirements: Protocol requirements for Target
      Applications to make use of in-network storage within their own
      data dissemination schemes.  Development of these requirements is
      guided by a study of data access, search and management
      capabilities used by Target Applications.  These requirements may
      be met by a new protocol to be defined within the DECADE Working
      Group.

   o  Storage Requirements: Functional requirements necessary for the
      back-end storage system employed by the DECADE server.
      Development of these requirements is guided by a study of the data
      access patterns used by Target Applications.  These requirements
      should be met by the underling data transport used by DECADE.

   It should also be made clear that the approach is to make DECADE a
   simple protocol, while still enabling its usage within many Target
   Applications.  For this reason, and to further reinforce the
   distinction between DECADE and a storage system, in some cases we
   also highlight the non-requirements of the protocol.  These non-
   requirements are intended to capture behaviors that will NOT be
   assumed to be needed by DECADE's Target Applications and hence not
   present in the DECADE protocol.

   Finally, some implementation considerations are provided, which while
   strictly are not requirements, are intended to provide guidance and
   highlight potential points of concern that need to be considered by
   the protocol developers, and later by implementors.

4.  Protocol Requirements

4.1.  Requirements

4.1.1.  Overall Protocol Requirements

4.1.1.1.  Cross-platform Access

   REQUIREMENT(S):  If DECADE supports the ability to store metadata
       associated with data objects, the DECADE protocol(s) MUST
       transmit any metadata using an operating system-independent and
       architecture-independent format.

   RATIONALE:  If DECADE supports the possibility for storing metadata
       (e.g., a description, uploaded date, object size, or access
       control list), a possible use for the metadata is to help a
       DECADE client locate a desired data object.  Data objects may be
       stored by DECADE clients running on various platforms.  To enable
       metadata to be readable regardless of its source it must be
       transmitted to and from the DECADE server in a standard format.

4.1.1.2.  Connectivity Concerns

4.1.1.2.1.  NATs and Firewalls

   REQUIREMENT(S):  DECADE SHOULD be usable across firewalls and NATs
       without requiring additional network support (e.g., Application-
       level Gateways).

   RATIONALE:  Firewalls and NATs are widely used in the Internet today,
       both in ISP networks and within households.  Deployment of DECADE
       must not require modifications to such devices (beyond, perhaps,
       reconfiguration).  Note that this requirement applies to both any
       new protocol developed by the DECADE Working Group and any data
       transport used with DECADE.

4.1.1.2.2.  Connections to Clients

   REQUIREMENT(S):  DECADE SHOULD require that network connections be
       made from DECADE clients to DECADE servers (i.e., not to the
       DECADE client).

   RATIONALE:  Many household networks and operating systems have
       firewalls and NATs configured by default.  To ease deployment by
       avoiding configuration changes and help mitigate security risks,
       DECADE should not require clients to listen for any incoming
       network connections (beyond what is required by any other
       already-deployed application).

4.1.1.3.  Security

4.1.1.3.1.  Secure Transport

   REQUIREMENT(S):  DECADE MUST contain a mode in which all
       communication between a DECADE client and server is over a secure
       transport that provides confidentiality, integrity, and
       authentication.

   RATIONALE:  Target Applications may wish to store sensitive data.  To
       satisfy this use case, DECADE must provide a mode in which all
       communication between a DECADE client and server occurs over a
       secure transport protocol (e.g., SSL/TLS).

4.1.1.3.2.  Connections to Clients

   REQUIREMENT(S):  DECADE SHOULD require that network connections be
       made from DECADE clients to DECADE servers (i.e., not to the
       DECADE client).

   RATIONALE:  Many household networks and operating systems have
       firewalls and NATs configured by default.  To ease deployment by
       avoiding configuration changes and help mitigate security risks,
       DECADE should not require clients to listen for any incoming
       network connections (beyond what is required by any other
       already-deployed application).

4.1.1.4.  Error and Failure Conditions

4.1.1.3.1.

4.1.1.4.1.  Overload Condition

   REQUIREMENT(S):  In-network storage, which is operating close to its
       capacity limit (e.g., too busy servicing other requests), MUST be
       able to reject requests and not be required to generate responses
       to additional requests.

   RATIONALE:  When in-network storage is operating at a limit where it
       may not be able to process additional requests, it should not be
       required to generate responses to such additional requests.
       Forcing the in-network storage to do so can impair its ability to
       service existing requests.

4.1.1.3.2.

4.1.1.4.2.  Insufficient Resources
   REQUIREMENT(S):  DECADE MUST support an error condition indicating to
       a DECADE client that resources (e.g., storage space) were not
       available to service a request (e.g., storage quota exceeded when
       attempting to store data).

   RATIONALE:  The currently-used resource levels within the in-network
       storage are not locally-discoverable, since the resources (disk,
       network interfaces, etc) are not directly attached.  In order to
       allocate resources appropriately amongst remote clients, a client
       must be able to determine when resource limits have been reached.
       The client can then respond by explicitly freeing necessary
       resources or waiting for such resources to be freed.

4.1.1.3.3.

4.1.1.4.3.  Unavailable and Deleted Data

   REQUIREMENT(S):  DECADE MUST support error conditions indicating that
       (1) data was rejected from being stored, (2) deleted, or (3)
       marked unavailable by a storage provider.

   RATIONALE:  Storage providers may require the ability to (1) avoid
       storing, (2) delete, or (3) quarantine certain data that has been
       identified as illegal (or otherwise prohibited).  DECADE does not
       indicate how such data is identified, but applications using
       DECADE should not break if a storage provider is obligated to
       enforce such policies.  Appropriate error conditions should be
       indicated to applications.

4.1.1.3.4.

4.1.1.4.4.  Redirection

   REQUIREMENT(S):  DECADE SHOULD support the ability for a DECADE
       server to redirect requests to another DECADE server.  This may
       be in response to either an error or failure condition, or to
       support capabilities such as load balancing.

   RATIONALE:  A DECADE server may opt to redirect requests to another
       server to support capabilities such as load balancing, or if the
       implementation decides that another DECADE server is in a better
       position to handle the request due to either its location in the
       network, server status, or other consideration.

4.1.2.  Transfer and Latency Requirements

4.1.2.1.  Low-Latency Access
   REQUIREMENT(S):  DECADE SHOULD provide "low-latency" access for
       application clients.  DECADE MUST allow clients to specify at
       least two classes of services for service: lowest possible
       latency and latency non-critical.

   RATIONALE:  Some applications may have requirements on delivery time
       (e.g., live streaming [PPLive]).  The user experience may be
       unsatisfactory if the use of in-network storage results in lower
       performance than connecting directly to remote clients over a
       low-speed, possibly congested uplink.  Additionally, the overhead
       required for control-plane operations in DECADE must not cause
       the latency to be higher than for a low-speed, possibly congested
       uplink.  While it is impossible to make a guarantee that a system
       using in-network storage will always outperform a system that
       does not for every transfer, the overall performance of the
       system should be improved compared with direct connections, even
       considering control overhead.

4.1.2.2.  Indirect Transfer

   REQUIREMENT(S):  DECADE MUST allow a user's in-network storage to
       directly fetch from other user's in-network storage.

   RATIONALE:  As an example, a requesting remote client may get the
       address of the storage pertaining to the source/owner client and
       then tell its own in-network storage to fetch the content from
       the source-owner's in-network storage.  This helps to avoid extra
       transfers across ISP network links where possible.

4.1.2.3.  Data Object Size

   REQUIREMENT(S):  DECADE MUST allow for efficient data transfer of
       small objects (e.g., 16KB) between a DECADE client and in-network
       storage with minimal additional latency required by the protocol.

   RATIONALE:  Though Target Applications are frequently used to share
       large amounts of data (e.g., continuous streams or large files),
       the data itself is typically subdivided into smaller chunks that
       are transferred between clients.  Additionally, the small chunks
       may have requirements on delivery time (e.g., in a live-streaming
       application).  DECADE must enable data to be efficiently
       transferred amongst clients at this granularity.

4.1.2.4.  Communication among In-network Storage Elements
   REQUIREMENT(S):  DECADE SHOULD support the ability for two in-network
       storage elements in different administrative domains to store
       and/or retrieve data directly between each other.  If such a
       capability is supported, this MAY be the same (or a subset or
       extension of) as the IAP used by clients to access data.

   RATIONALE:  Allowing server-to-server communication can reduce
       latency in some common scenarios.  Consider a scenario when a
       DECADE client is downloading data into its own storage from
       another client's in-network storage.  One possibility is for the
       client to first download the data itself, and then upload it to
       its own storage.  However, this causes unnecessary latency and
       network traffic.  Allowing the data to be downloaded from the
       remote in-network storage into the client's own in-network
       storage can alleviate both.

4.1.3.  Data Access Requirements

4.1.3.1.  Reading/Writing Own Storage

   REQUIREMENT(S):  DECADE MUST support the ability for a DECADE client
       to read data from and write data to its own in-network storage.

   RATIONALE:  Two basic capabilities for any storage system are reading
       and writing data.  A DECADE client can read data from and write
       data to in-network storage space that it owns.

4.1.3.2.  Access by Other Users

   REQUIREMENT(S):  DECADE MUST support the ability for a user to apply
       access control policies to users other than itself for its
       storage.  The users with whom access is being shared can be under
       a different administrative domain than the user who owns the in-
       network storage.  The authorized users may read from or write to
       the user's storage.

   RATIONALE:  Endpoints in Target Applications may be located across
       multiple ISPs under multiple administrative domains.  Thus, to be
       useful by Target Applications, DECADE allows a user to specify
       access control policies for users that may or may not be known to
       the user's storage provider.

4.1.3.3.  Negotiable Data Protocol
   REQUIREMENT(S):  DECADE MUST support the ability for a DECADE client
       to negotiate with its in-network storage about which protocol it
       can use to read data from and write data to its In-network
       storage.  DECADE MUST specify at least one mandatory protocol to
       be supported by implementations; usage of a different protocol
       may be selected via negotiation.

   RATIONALE:  Since typical data transport protocols (e.g., NFS and
       WebDAV) already provide read and write operations for network
       storage, it may not be necessary for DECADE to define such
       operations in a new protocol.  However, because of the particular
       application requirements and deployment considerations, different
       applications may support different protocols.  Thus, a DECADE
       client must be able to select an appropriate protocol also
       supported by the in-network storage.  This requirement also
       follows as a result of the requirement of Separation of Control
       and Data Operations (Section 4.1.3.4).

4.1.3.4.  Separation of Data Operations from Application Control

   REQUIREMENT(S):  The DECADE IAP MUST only provide a minimal set of
       core operations to support diverse policies implemented and
       desired by Target Applications.

   RATIONALE:  Target Applications support many complex behaviors and
       diverse policies to control and distribute data, such as (e.g.,
       search, index, setting permissions/passing authorization tokens).
       Thus, to support such Target Applications, these behaviors must
       be logically separated from the data transfer operations (e.g.,
       retrieve, store).  Some minimal overlap (for example obtaining
       credentials needed to encrypt or authorize data transfer using
       control operations) may be required to be directly specified by
       DECADE.

4.1.4.  Data Management Requirements

4.1.4.1.  Agnostic of reliability

   REQUIREMENT(S):  DECADE SHOULD remain agnostic of reliability/
       fault-tolerance level offered by storage provider.

   RATIONALE:  Providers of a DECADE service may wish to offer varying
       levels of service for different applications/users.  However, a
       single compliant DECADE client should be able to use multiple
       DECADE services with differing levels of service.

4.1.4.2.  Time-to-live for Stored Data

   REQUIREMENT(S):  DECADE MUST support the ability for a DECADE client
       to indicate a time-to-live value (or expiration time) indicating
       a length of time until particular data can be deleted by the in-
       network storage element.

   RATIONALE:  Some data stored by a DECADE client may be usable only
       within a certain window of time, such as in live-streaming P2P
       applications.  Providing a time-to-live value for stored data
       (e.g., at the time it is stored) can reduce management overhead
       by avoiding many 'delete' commands sent to in-network storage.
       The in-network storage may still keep the data in cache for
       bandwidth optimization.  But this is guided by the privacy policy
       of the DECADE provider.

4.1.4.3.  Offline Usage

   REQUIREMENT(S):  DECADE MAY support the ability for a user to provide
       authorized access to its in-network storage even if the user has
       no DECADE applications actively running or connected to the
       network.

   RATIONALE:  If an application desires, it can authorize remote
       clients to access its storage even after the application exits or
       network connectivity is lost.  An example use case is mobile
       scenarios, where a client can lose and regain network
       connectivity very often.

4.1.5.  Data Naming Requirements

4.1.5.1.  Unique Names

   REQUIREMENT(S):  DECADE SHOULD use a naming scheme in which the name
       of a data object is unique from the names of all other data
       objects with different content.

   RATIONALE:  When storing a data object, a DECADE Client should be
       able to store it without being concerned over whether an object
       of the same name already exists, unless the existing object
       contains the exact same data.  Note that it may be reasonable for
       DECADE to satisfy this requirement probabilistically (e.g., using
       a hashing mechanism).

4.1.6.  Resource Control

4.1.5.1.

4.1.6.1.  Multiple Applications

   REQUIREMENT(S):  DECADE SHOULD support the ability for users to
       define resource sharing policies for multiple applications
       (DECADE clients) being run/managed by the user.

   RATIONALE:  A user may own in-network storage and share the in-
       network storage resources amongst multiple applications.  For
       example, the user may run a video-on-demand application and a
       live-streaming (or even two different live-streaming
       applications) application which both make use of the user's in-
       network storage.  The applications may be running on different
       machines and may not directly communicate.  Thus, DECADE should
       enable the user to determine resource sharing policies between
       the applications.

       One possibility is for a user to indicate the particular resource
       sharing policies between applications out-of-band (not using a
       standard protocol), but this requirement may manifest itself in
       passing values over IAP to identify individual applications.
       Such identifiers can be either user-generated or server-generated
       and do not need to be registered by IANA.

4.1.5.2.

4.1.6.2.  Per-Remote-Client, Per-Data Control

   REQUIREMENT(S):  A DECADE client MUST be able to assign resource
       quotas to individual remote clients for reading from and writing
       particular data to its in-network storage within a particular
       range of time.  The DECADE server MUST enforce these constraints.

   RATIONALE:  Target Applications can rely on control of resources on a
       per-remote-client or per-data basis.  For example, application
       policy may indicate that certain remote clients have a higher
       bandwidth share for receiving data [LLSB08].  Additionally,
       certain data (e.g., chunks) may be distributed with a higher
       priority.  As another example, when allowing a remote client to
       write data to a user's in-network storage, the remote client may
       be restricted to write only a certain amount of data.  Since the
       client may need to manage multiple clients accessing its data, it
       should be able to indicate the time over which the granted
       resources are usable.  For example, an expiration time for the
       access could be indicated to the server after which no resources
       are granted (e.g., indicate error as access denied).

4.1.5.3.

4.1.6.3.  Server Involvement

   REQUIREMENT(S):  A DECADE client MUST SHOULD be able to indicate to a
       DECADE server, without itself contacting the server, resource
       control policies for remote clients' requests.

   RATIONALE:  One important consideration for in-network storage
       elements is scalability, since a single storage element may be
       used to support many users.  Many Target Applications use small
       chunk sizes and frequent data exchanges.  If such an application
       employed resource control and contacted the in-network storage
       element for each data exchange, this could present a scalability
       challenge for the server as well as additional latency for
       clients.

       An alternative is to let requesting users get the obtain signed resource
       control policies from the owning user, and then users can then
       present the policy to the storage directly.  This can result in
       reduced messaging handled by the in-network storage.

4.1.6.

4.1.7.  Authorization

4.1.6.1.

4.1.7.1.  Per-Remote-Client, Per-Data Read Access

   REQUIREMENT(S):  A DECADE Client MUST be able to control which
       individual remote clients are authorized to read particular data
       stored on its in-network storage.

   RATIONALE:  A Target Application can control certain application-
       level policies by sending particular data (e.g., chunks) to
       certain remote clients.  It is important that remote clients not
       be able to circumvent such decisions by arbitrarily reading any
       currently-stored data in in-network storage.

4.1.6.2.

4.1.7.2.  Per-User Write Access

   REQUIREMENT(S):  A DECADE Client MUST be able to control which
       individual remote clients are authorized to store data into its
       in-network storage.

   RATIONALE:  The space managed by a user in in-network storage can be
       a limited resource.  At the same time, it can be useful to allow
       remote clients to write data directly to a user's in-network
       storage.  Thus, a DECADE client should be able to grant only
       certain remote clients this privilege.

       Note that it is not (currently) a requirement to check that a
       remote client stores a particular set of data (e.g., the check
       that a remote client writes the expected chunk of a file).
       Enforcing this as a requirement would require a client to know
       which data is expected (e.g., the full chunk itself or a hash of
       the chunk) which may not be available in all applications.
       Checking for a particular hash could be considered as a
       requirement in the future that could optionally be employed by
       applications.

4.1.6.3.

4.1.7.3.  Authorization Checks

   REQUIREMENT(S):  In-network storage MUST check the authorization of a
       client before it executes a supplied request.  The in-network
       storage MAY use optimizations to avoid such authorization checks
       as long as the enforced permissions are the the same.

   RATIONALE:  Authorization granted by a DECADE client are meaningless
       unless unauthorized requests are denied access.  Thus, the in-
       network storage element must verify the authorization of a
       particular request before it is executed.

4.1.6.4.

4.1.7.4.  Credentials Not IP-Based

   REQUIREMENT(S):  Access MUST be able to be granted on other
       credentials than the IP address

   RATIONALE:  DECADE clients may be operating on hosts without constant
       network connectivity or without a permanent attachment address
       (e.g., mobile devices).  To support access control with such
       hosts, DECADE servers must support access control policies that
       use information other than IP addresses.

4.1.6.5.

4.1.7.5.  Server Involvement

   REQUIREMENT(S):  A DECADE client MUST SHOULD be able to indicate, without
       contacting the server itself, access control policies for remote
       clients' requests.

   RATIONALE:  See discussion in Section 4.1.5.3. 4.1.6.3.

5.  Storage  Discovery Requirements

5.1.  Requirements
5.1.1.  Locating DECADE Servers

   REQUIREMENT(S):  The DECADE Discovery mechanism MUST allow a DECADE
       Client to identify one or more DECADE Servers to which it is
       authorized to read/write data and to which it may authorize other
       DECADE Clients to read/write data, or fail if no such DECADE
       Servers are available.

   RATIONALE:  A basic goal of DECADE is to allow DECADE Clients to
       read/write data for access by other DECADE Clients or itself.
       Executing the Discovery process should result in a DECADE Client
       finding a DECADE Server that it can use for these purposes.  It
       is possible that no such DECADE Servers are available.  Note that
       even if a DECADE Client may not successfully locate a DECADE
       Server that fits these critieria, it may still read/write data a
       DECADE Server if authorized by another DECADE Client.

5.1.2.  Support for Clients Behind NATs and Firewalls

   REQUIREMENT(S):  The Discovery mechanism MUST support DECADE Clients
       operating behind NATs and Firewalls without requiring additional
       network support (e.g., Application-level Gateways).

   RATIONALE:  NATs and Firewalls are prevalent in network deployments,
       and it is common for Target Applications wishing to include a
       DECADE Client to be deployed behind these devices.

5.1.3.  Prefer Existing Protocols

   REQUIREMENT(S):  The DECADE Server discovery mechanism SHOULD prefer
       to use existing mechanisms and protocols wherever possible.

   RATIONALE:  Existing protocols such as DNS and DHCP are widespread.
       Using existing protocols, or combinations of the protocols that
       have been specified in other contexts, is strictly preferred over
       developing a new discovery protocol for DECADE.

6.  Storage Requirements

6.1.  Requirements

6.1.1.  Explicit Deletion of Stored Data
   REQUIREMENT(S):  DECADE MUST support the ability for a DECADE client
       to explicitly delete data from its own in-network storage.
       DECADE MAY have an overwrite flag indicating that an object with
       the same name should be replaced.

   RATIONALE:  A DECADE client may continually be writing data to its
       in-network storage.  Since there may be a limit (e.g., imposed by
       the storage provider) to how much total storage can be used, some
       data may need to be removed to make room for additional data.  A
       DECADE client should be able to explicitly remove particular
       data.  This may be implemented using existing protocols.

5.1.2.

6.1.2.  Multiple writing

   REQUIREMENT(S):  DECADE MUST NOT allow multiple writers for the same
       object.  Implementations raise an error to one of the writers.

   RATIONALE:  This avoids data corruption in a simple way while
       remaining efficient.

5.1.3.

6.1.3.  Multiple reading

   REQUIREMENT(S):  DECADE MUST allow for multiple readers for an
       object.

   RATIONALE:  One characteristic of Target Applications is the ability
       to upload an object to multiple clients.  Thus, it is natural for
       DECADE to allow multiple readers to read the content
       concurrently.

5.1.4.

6.1.4.  Reading before completely written

   REQUIREMENT(S):  DECADE MAY allow readers to read from objects before
       they have been completely written.

   RATIONALE:  Some Target Applications (in particular, P2P streaming)
       can be sensitive to latency.  A technique to reduce latency is to
       remove store-and-forward delays for data objects (e.g., make the
       object available before it is completely stored).  Appropriate
       handling for error conditions (e.g., a disappearing writer) needs
       to be specified.

5.1.5.

6.1.5.  Hints concerning usage stored data
   REQUIREMENT(S):  DECADE MAY allow writers of new objects to indicate
       specific hints concerning how the objects are expected to be used
       (e.g., access frequency or time to live).

   RATIONALE:  Different Target Applications may have different usage
       patterns for objects stored at in-network storage.  For example,
       a P2P live streaming application may indicate to a DECADE server
       that the objects are expected to have a shore time-to-live, but
       read frequently.  The DECADE server may then opt to store the
       objects in memory instead of in disk.

5.1.6.

6.1.6.  Writing model

   REQUIREMENT(S):  DECADE MUST provide at least a writing model (while
       storing an object) that appends data to data already stored.

   RATIONALE:  Depending on the object size (e.g., chunk size) used by a
       Target Application, the application may need to send data to the
       DECADE server in multiple packets.  To keep implementation
       simple, the DECADE must at least support the ability to write the
       data sequentially in the order received.  Implementations MAY
       allow application to write data in an object out-of-order (but
       MUST NOT overwrite ranges of the object that have already been
       stored).

5.1.7.

6.1.7.  Storage Status

   REQUIREMENT(S):  A DECADE client MUST be able to retrieve current
       resource usage (including list of stored data), resource quotas,
       and access permissions for its in-network storage.  The returned
       information MUST include resource usage resulting from the
       client's own usage and usage by other clients that have been
       authorized to read/write objects or open connections to that
       client's storage.

   RATIONALE:  The resources used by a client are not directly-attached
       (e.g., disk, network interface, etc).  Thus, the client cannot
       locally determine how such resources are being used.  Before
       storing and retrieving data, a client should be able to determine
       which data is available (e.g., after an application restart).
       Additionally, a client should be able to determine resource
       availability to better allocate them to remote clients.

5.2.

6.2.  Non-Requirements
5.2.1.
6.2.1.  No ability to update

   REQUIREMENT(S):  DECADE SHOULD NOT provide ability to update existing
       objects.  That is, objects are immutable once they are stored.

   RATIONALE:  Reasonable consistency models for updating existing
       objects would significantly complicate implementation (especially
       if implementation chooses to replicate data across multiple
       servers).  If a user needs to update a resource, it can store a
       new resource and then distribute the new resource instead of the
       old one.

6.

7.  Implementation Considerations

   The intent of this section is to collect discussion items and
   implementation considerations that have been discovered as this
   requirements document has been produced.  The content of this section
   will be migrated to an appropriate place as the document and the
   Working Group progress.

6.1.

7.1.  Resource Scheduling

   The particular resource scheduling policy may have important
   ramifications on the performance of applications.  This document has
   explicitly mentioned simultaneous support for both low-latency
   applications and latency-tolerant applications.

   Denial of Service attacks may be another risk.  For example,
   rejecting new requests due to overload conditions may introduce the
   ability to perform a denial of service attack depending on a
   particular DECADE server's scheduling implementation and resource
   allocation policies.

6.2.

7.2.  Removal of Duplicate Records

   There are actually two possible scenarios here.  The first is the
   case of removing duplicates within one particular DECADE server (or
   logical server).  While not a requirement, as it does not impact the
   protocol and is technically not noticeable on message across the
   wire, a DECADE server may implement internal mechanisms to monitor
   for duplicate records and use internal mechanisms to prevent
   duplication of internal storage.

   The second scenario is removing duplicates across a distributed set
   of DECADE servers.  This is a more difficult problem, and if the
   group decides to support this capability, it may require protocol
   support.  See Section 7.2 8.2 for more details.

7.

8.  Discussion and Open Issues

7.1.

8.1.  Discussion

   Sometimes, several logical in-network storages could be deployed on
   the same physical network device.  In this case, in-network storages
   on the same physical network device can communicate and transfer data
   through internal communication messages.  However in-network storages
   deployed on different physical network devices SHOULD communicate
   with in-network storage Access Protocol (IAP).

   To provide fairness among users, the in-network storage provider
   should assign resource (e.g., storage, bandwidth, connections) quota
   for users.  This can prevent a small number of clients from occupying
   large amounts of resources on the in-network storage, while others
   starve.

7.2.

8.2.  Open Issues

   Gaming of the Resource Control Mechanism:  There has been some
       discussion of how applications may be able game the scheduling
       system by manipulating the resource control mechanism, for
       example by specifying many small peers to increase total
       throughput.  This is a serious concern, and we need to identify
       specific requirements on the protocol (hopefully independent of
       particular scheduling/resource control schemes) to help address
       this.

   Discovery:  There needs to be some mechanism for a user to discover
       that there is a DECADE service available for their use, and to
       locate that server.  This is particularly important in the case
       of mobile applications, since the actual servers that are
       available at any given time may differ.  However, the specifics
       of what mechanisms (DHCP, HTTP page, etc.) have not been
       discussed, or even if the protocol should specify one or leave it
       as an implementation detail.  This needs to be defined, and
       specific requirements formulated if needed.

   Removal of Duplicate Records Across Servers:  If the group wishes to
       allow for automated mechanisms to remove duplicates across a
       number of separate servers, some protocol support may need to be
       added.  In the case of removing duplicates within a single
       (logical) DECADE server, this is simply an implementation
       concern.  See Section 6 7 for more details.

8.

9.  Security Considerations

   Authorization for access to in-network storage is an important part
   of the requirements listed in this document.  Authorization for
   access to storage resources and the data itself is important for
   users to be able to manage and limit distribution of content.  For
   example, a user may only wish to share particular content with
   certain peers.

   If the authorization technique implemented in DECADE passes any
   private information (e.g., user passwords) over the wire, it MUST be
   passed in a secure way.

9.

10.  IANA Considerations

   There are no IANA considerations with this document.

10.

11.  References

10.1.

11.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

10.2.

11.2.  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.

   [LLSB08]   Dave   Levin, Katrina D., LaCurts, Neil K., Spring, Bobby
              Bhattacharjee., N., and B. Bhattacharjee,
              "BitTorrent is an Auction: Analyzing and Improving
              BitTorrent's Incentives", In SIGCOMM 2008, August 2008.

   [PPLive]   "PPLive", http://www.pplive.com. <http://www.pplive.com>.

Appendix A.  Acknowledgments

   We would also like to thank Haibin Song for substantial contributions
   to earlier versions of this document.  We would also like to thank
   Reinaldo Penno, Alexey Melnikov, Rich Woundy, Ning Zong, Roni Even,
   David McDysan, Boerje Ohlman and Dirk Kutscher for contributions
   (including some text used verbatim) and general feedback.

Authors' Addresses

   Yingjie Gu
   Huawei
   No. 101 Software Avenue
   Nanjing, Jiangsu Province  210012
   P.R.China

   Phone: +86-25-56624760
   Email: guyingjie@huawei.com

   David A. Bryan
   Cogent Force, LLC / Huawei

   Email: dbryan@ethernot.org

   Yang Richard Yang
   Yale University

   Email: yry@cs.yale.edu

   Richard Alimi
   Google

   Email: ralimi@google.com