DECADE                                                             Y. Gu
Internet-Draft                                                    Huawei
Intended status: Informational                                  D. Bryan
Expires: January 12, March 31, 2012                                    Polycom, Inc.
                                                                 Y. Yang
                                                         Yale University
                                                                R. Alimi
                                                           July 11,
                                                      September 28, 2011

                          DECADE Requirements


   The target of DECoupled Application Data Enroute (DECADE) is to
   provide an open and standard in-network storage system for
   applications, primarily P2P (peer-to-peer) applications, to store,
   retrieve and manage their data.  This draft enumerates and explains
   requirements, not only for store storage and retrieve, retrieval, 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., a protocol used to read and write data from
   the storage system).  A user of  The requirements in this document are intended
   to ensure that the DECADE as a complete architecture
   would be guaranteed complete functionality. includes all of the desired
   functionality for intended applications.

Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   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
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   This Internet-Draft will expire on January 12, March 31, 2012.

Copyright Notice

   Copyright (c) 2011 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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   ( in effect on the date of
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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  5
   2.  Terminology and Concepts . . . . . . . . . . . . . . . . . . .  5
   3.  Requirements Structure . . . . . . . . . . . . . . . . . . . .  6
   4.  Protocol Requirements  . . . . . . . . . . . . . . . . . . . .  7
     4.1.  Overall Protocol Requirements  . . . . . . . . . . . . . .  7
       4.1.1.  Metadata and Cross-platform Access . . . . . . . . . .  7
       4.1.2.  Connectivity Concerns  . . . . . . . . . . . . . . . .  7  NATs and Firewalls . . . . . . . . . . . . . . . .  7  Connections to Clients . . . . . . . . . . . . . .  8
       4.1.3.  7
       4.1.2.  Security . . . . . . . . . . . . . . . . . . . . . . .  8  7  Secure Transport . . . . . . . . . . . . . . . . .  8
       4.1.4.  7
       4.1.3.  Error and Failure Conditions . . . . . . . . . . . . .  8  Overload Condition . . . . . . . . . . . . . . . .  8  Insufficient Resources . . . . . . . . . . . . . .  8  Unavailable and Deleted Data . . . . . . . . . . .  8  Insufficient Permissions . . . . . . . . . . . . .  9  Redirection  . . . . . . . . . . . . . . . . . . .  9
     4.2.  Transfer and Latency Requirements  . . . . . . . . . . . .  9
       4.2.1.  Low-Latency Access . . . . . . . . . . . . . . . . . .  9
       4.2.2.  Data Object Size . . . . . . . . . . . . . . . . . . . 10
       4.2.3.  Communication among DECADE Servers . . . . . . . . . . 10
     4.3.  Data Access Requirements . . . . . . . . . . . . . . . . . 11
       4.3.1.  Reading/Writing Own Storage  . . . . . . . . . . . . . 11
       4.3.2.  Access by Other Users  . . . . . . . . . . . . . . . . 11
       4.3.3.  Negotiable Data Transport Protocol . . . . . . . . . . 11
       4.3.4.  Separation of Data and Control Policies  . . . . . . . 12
     4.4.  Data Management Requirements . . . . . . . . . . . . . . . 12
       4.4.1.  Agnostic of reliability  . . . . . . . . . . . . . . . 12
       4.4.2.  Data Object Attributes . . . . . . . . . . . . . . . . 12
       4.4.3.  Time-to-live for Written Data Objects  . . . . . . . . 12
       4.4.3. 13
       4.4.4.  Offline Usage  . . . . . . . . . . . . . . . . . . . . 13
     4.5.  Data Naming Requirements . . . . . . . . . . . . . . . . . 13
       4.5.1.  Unique Names . . . . . . . . . . . . . . . . . . . . . 13
     4.6.  Resource Control . . . . . . . . . . . . . . . . . . . . . 13 14
       4.6.1.  Multiple Applications  . . . . . . . . . . . . . . . . 13 14
       4.6.2.  Per-Remote-Client, Per-Data Control  . . . . . . . . . 14
       4.6.3.  Server Involvement . . . . . . . . . . . . . . . . . . 14 15
     4.7.  Authorization  . . . . . . . . . . . . . . . . . . . . . . 15
       4.7.1.  Per-Remote-Client, Per-Data Read Access  . . . . . . . 15
       4.7.2.  Per-User Write Access  . . . . . . . . . . . . . . . . 15
       4.7.3.  Default Access Permissions . . . . . . . . . . . . . . 15 16
       4.7.4.  Authorization Checks . . . . . . . . . . . . . . . . . 15 16
       4.7.5.  Cryptographic Credentials  . . . . . . . . . . . . . . 16
       4.7.6.  Server Involvement . . . . . . . . . . . . . . . . . . 16
       4.7.7.  Protocol Reuse . . . . . . . . . . . . . . . . . . . . 16
     4.8.  Non-Requirements . . . . . . . . . . . . . . . . . . . . . 17
       4.8.1.  Application-defined Properties and Metadata  . . . . . 17

   5.  Storage Requirements . . . . . . . . . . . . . . . . . . . . . 16 17
     5.1.  Immutable Data . . . . . . . . . . . . . . . . . . . . . . 16 17
     5.2.  Explicit Deletion of Data  . . . . . . . . . . . . . . . . 17
     5.3.  Multiple writing . . . . . . . . . . . . . . . . . . . . . 17 18
     5.4.  Multiple reading . . . . . . . . . . . . . . . . . . . . . 17 18
     5.5.  Reading before completely written  . . . . . . . . . . . . 18
     5.6.  Hints concerning usage of written data . . . . . . . . . . 18
     5.7.  Writing model  . . . . . . . . . . . . . . . . . . . . . . 18 19
     5.8.  Storage Status . . . . . . . . . . . . . . . . . . . . . . 18 19
   6.  Discovery Requirements . . . . . . . . . . . . . . . . . . . . 19 20
     6.1.  Requirements . . . . . . . . . . . . . . . . . . . . . . . 19 20
       6.1.1.  Locating DECADE Servers  . . . . . . . . . . . . . . . 19 20
       6.1.2.  Support for Clients Behind NATs and Firewalls  . . . . 19 20
       6.1.3.  Prefer Existing Protocols  . . . . . . . . . . . . . . 20
   7.  Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . 20
     7.1.  Non-IAP  Non-DECADE Internal Protocols  . . . . . . . . . . . . . . . . 20
     7.2.  Fairness . . . . . . . . . . . . . . . . . . . . . . . . . 20 21
     7.3.  Removal of Duplicate Data Objects  . . . . . . . . . . . . 20 21
     7.4.  Gaming of the Resource Control Mechanism . . . . . . . . . 21
   8.  Security Considerations  . . . . . . . . . . . . . . . . . . . 21
     8.1.  Authentication and Authorization . . . . . . . . . . . . . 21 22
     8.2.  Encrypted Data . . . . . . . . . . . . . . . . . . . . . . 21 22
   9.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 21 22
   10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 22
     10.1. Normative References . . . . . . . . . . . . . . . . . . . 22
     10.2. Informative References . . . . . . . . . . . . . . . . . . 22
   Appendix A.  Acknowledgments . . . . . . . . . . . . . . . . . . . 22 23
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 22 23

1.  Introduction

   The object of DECoupled Application Data Enroute (DECADE) is to
   provide an open and standard in-network storage system for content
   distribution applications, where data is typically broken in to into one or
   more chunks and then distributed.  This may already include many
   types of applications including P2P applications, IPTV (Internet
   Protocol Television), and VoD (Video on Demand).  (For a precise
   definition of the applications targeted in DECADE, see the definition
   for Target Application in Section 2.)  Instead of always transferring
   data directly from a source/owner client to a requesting client, the
   source/owner client can write to 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 read
   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 principles.
   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
   [I-D.ietf-decade-arch] 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
   writing, reading, and managing data, but also controlling access for
   particular remote clients with which it is sharing data.
   Additionally, we also consider controlling the resources used by
   remote clients when they access data as an integral part of utilizing
   the network storage.

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 content to a large number of users.

   This includes scenarios where multiple applications or entities
   cooperate, such as with P2P (peer-to-peer) / CDN (Content
   Distribution Network) P2P, CDN, and hybrid P2P/CDN architectures.
   Such applications distribute large amounts of content (e.g., a large
   file, or video stream) by dividing the content into smaller blocks
   for more flexible distribution (e.g., over multiple application-level
   paths).  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.  DECADE does not intend to 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 primary 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 combination of existing protocols and new protocol protocols 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 underlying data transport used by DECADE.  In
      this document, we use "data transport" to refer to a protocol used
      to read and write data from DECADE in-network storage.

   Note that a third category also enumerates requirements on the
   protocol used to discovery discover DECADE Servers.

   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
   not strictly requirements, are intended to provide guidance and
   highlight potential points that need to be considered by the protocol
   developers, and later by implementors.

4.  Protocol Requirements

   This section details the requirements of the DECADE IAP. protocol(s).

4.1.  Overall Protocol Requirements

4.1.1.  Metadata and Cross-platform Access

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

   RATIONALE:  If DECADE supports storing metadata (e.g., a description,
       uploaded date, object size), a possible use for the metadata is
       to help a DECADE client locate a desired data object.  Data
       objects may be written 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.

4.1.2.  Connectivity Concerns  NATs and Firewalls

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

   RATIONALE:  Firewalls and NATs are widely used in the Internet today,
       both in ISP (Internet Service Provider) and Enterprise networks
       and by consumers.  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.  Connections to Clients

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

   RATIONALE:  Many household networks and operating systems have
       firewalls and NATs configured by default to block incoming
       connections.  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


4.1.2.  Security  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

   RATIONALE:  Target Applications may wish to write 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).


4.1.3.  Error and Failure Conditions  Overload Condition

   REQUIREMENT(S):  In-network storage, which is operating close to its
       capacity limit (e.g., too busy servicing other requests), MUST be
       permitted to reject requests and not be required to generate
       responses to additional requests.  In-network storage MUST also
       be permitted to redirect requests (see Section as a
       load-shedding technique.

   RATIONALE:  Forcing the in-network storage to respond to requests
       when operating close to its capacity can impair its ability to
       service existing requests, and thus is permitted to avoid
       generating responses to additional requests.  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 write 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.  Unavailable and Deleted Data

   REQUIREMENT(S):  DECADE MUST support error conditions indicating that
       (1) data was rejected from being written, (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.  Insufficient Permissions

   REQUIREMENT(S):  DECADE MUST support error conditions indicating that
       the requesting client does not have sufficient permissions to
       access requested data objects.

   RATIONALE:  DECADE clients may request objects to which they do not
       have sufficent access permissions, and DECADE servers must be
       able to signal that this has occurred.  Note that access
       permissions may be insufficient due to a combination of the
       credentials presented by a client as well as additional policies
       defined by the storage provider.  Redirection

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

4.2.  Transfer and Latency Requirements

4.2.1.  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 low-speed uplink
       connections, even considering control overhead.

4.2.2.  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 imposed 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.  It is important
       to note that DECADE may be used to store and retrieve larger
       objects, but protocol(s) should not be designed such that usage
       with smaller data objects cannot meet the requirements of Target

4.2.3.  Communication among DECADE Servers

   REQUIREMENT(S):  DECADE SHOULD support the ability for two in-network
       storage elements in different administrative domains to write
       and/or read data directly between each other (if authorized as
       described in Section 4.7).  If such a capability is supported,
       this MAY be the same (or a subset or extension of) as the IAP DECADE
       protocol(s) 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 uploading 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 in-
       network storage can alleviate both.

4.3.  Data Access Requirements

4.3.1.  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.

4.3.2.  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 implement
       access control policies for users that may or may not be known to
       the user's storage provider.

4.3.3.  Negotiable Data Transport 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 4.3.4).

4.3.4.  Separation of Data and Control Policies

   REQUIREMENT(S):  The  DECADE IAP Protocol(s) 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.,
       read, write).  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

4.4.  Data Management Requirements

4.4.1.  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.

4.4.2.  Data Object Attributes

   REQUIREMENT(S):  DECADE MUST support the ability to associate
       attributes with data objects with a scope local to a DECADE
       server, and for DECADE clients to query these attributes.  DECADE
       protocol(s) MUST transmit any attributes using an operating
       system-independent and architecture-independent standard format.
       DECADE protocol(s) MUST be designed such that new attributes can
       be added by later protocol revisions or extensions.

   RATIONALE:  DECADE supports associating attributes (e.g., a time-to-
       live, creation timestamp, or object size) with a data object.
       These attributes are local to a data object stored by a
       particular DECADE server, and are thus not applied to any DECADE
       server or client to which the data object is copied.  These
       attributes may be used as hints to the storage system, internal
       optimizations, or as additional information queryable by DECADE

4.4.3.  Time-to-live for Written Data Objects

   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 objects written 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
       data objects (e.g., at the time they are written) 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.


4.4.4.  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

   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.

4.5.  Data Naming Requirements

4.5.1.  Unique Names

   REQUIREMENT(S):  DECADE MUST use support a naming scheme with an extremely
       large namespace and mechanisms that ensure that the name of ensures a
       data object is statistically unlikely to be the same as
       high probability of uniqueness and supports the names operation of all other data objects (globally)
       DECADE servers under diverse administrative domains with different content. no
       coordination.  DECADE SHOULD provide a mechanism (minimally
       rejection) to handle the improbable case of a collision.

   RATIONALE:  When writing a data object, a DECADE Client should be
       able to write 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).  As a result, it is wise to provide a
       collision handling mechanism, even if the probability of
       collisions is extremely low.

4.6.  Resource Control

4.6.1.  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 one or more video-on-demand
       application(s) and a live-streaming application(s) 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 within DECADE protocol(s) to identify individual
       applications.  Such identifiers can be either user-generated or
       server-generated and do not need to be registered by IANA.

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

   REQUIREMENT(S):  A DECADE client MUST be able to assign resource
       policies (bandwidth share, storage quota, and network connection
       quota) 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).

4.6.3.  Server Involvement

   REQUIREMENT(S):  A DECADE client 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


       Our preferred alternative is to let requesting users obtain
       signed resource control policies (in the form of a token) 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.

4.7.  Authorization

4.7.1.  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
       from 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
       data in in-network storage.

4.7.2.  Per-User Write Access

   REQUIREMENT(S):  A DECADE Client MUST be able to control which
       individual remote clients are authorized to write 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.

4.7.3.  Default Access Permissions

   REQUIREMENT(S):  Unless read or write access is granted by a DECADE
       Client to a remote client, the default access MUST be no access.

   RATIONALE:  The current leading proposal for an access control model
       in DECADE is via token passing, resulting in a system with little
       state on the server side.

4.7.4.  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 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.

4.7.5.  Cryptographic Credentials

   REQUIREMENT(S):  Access MUST be able to be granted using
       cryptographic credentials.

   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 cryptographic credentials, not simply by tying access to IP

4.7.6.  Server Involvement

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

   RATIONALE:  See discussion in Section 4.6.3.

4.7.7.  Protocol Reuse

   REQUIREMENT(S):  If possible, DECADE SHOULD reuse existing protocol
       and mechanisms for Authentication, Access, and Authorization

   RATIONALE:  If possible, reusing an existing AAA protocol/mechanism
       will minimize the development required by applications, and will
       maximize interoperability of the DECADE protocol with existing

4.8.  Non-Requirements

4.8.1.  Application-defined Properties and Metadata

   REQUIREMENT(S):  DECADE MUST NOT provide a mechanism for associating
       Application-defined properties (metadata) with data objects
       beyond what is provided by Section 4.4.2.

   RATIONALE:  Associating key-value pairs that are defined by Target
       Applications with data objects introduces substantial complexity
       to the DECADE protocol.  If Target Applications wish to associate
       additional metadata with a data object, possible alternatives
       include (1) managing such metadata within the Target Application
       itself, (2) storing metadata inside of the data object, or (3)
       storing metadata in a different data object at the DECADE server.

5.  Storage Requirements

   This section details the requirements of the underlying storage used
   to support the DECADE IAP. protocol(s).

5.1.  Immutable Data

   REQUIREMENT(S):  DECADE MUST provide the ability to manage data
       objects that are immutable once they are written to storage.

   RATIONALE:  Immutable data objects are an important simplification in
       DECADE.  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 write a
       new resource and then distribute the new resource instead of the
       old one.

5.2.  Explicit Deletion of Data

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

   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.

5.3.  Multiple writing

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

   RATIONALE:  This avoids data corruption in a simple way while
       remaining efficient.  Alternately, the DECADE server would need
       to either manage locking, handle write collisions, or merge data,
       all of which reduce efficiency and increase complexity.

5.4.  Multiple reading

   REQUIREMENT(S):  DECADE MUST allow for multiple simultaneous 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

5.5.  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 written).  Appropriate
       handling for error conditions (e.g., a disappearing writer) needs
       to be specified.

5.6.  Hints concerning usage of written 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). time-to-live).

   RATIONALE:  Different Target Applications may have different usage
       patterns for objects written to 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 short time-to-live, but
       read frequently.  The DECADE server may then opt to persist the
       objects in memory instead of in disk.

5.7.  Writing model

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

   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

5.8.  Storage Status

   REQUIREMENT(S):  A DECADE client MUST be able to read current
       resource usage (including list of written data objects), 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.  DECADE protocol(s) MUST support the ability
       for a DECADE client to read aggregated resource usage information
       (across all other clients to which it has authorized access), and
       MAY support the ability to request this information for each
       other authorized client.

   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.  Due to
       scalability issues, it is not required that DECADE support
       returning usage information broken down by each remote client
       which has been authorized access, but this feature may be useful
       in certain deployment scenarios.

6.  Discovery Requirements

6.1.  Requirements

6.1.1.  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 criteria, it may still read/write data a
       DECADE Server if authorized by another DECADE Client.

6.1.2.  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 that include a DECADE
       Client to be deployed behind these devices.

6.1.3.  Prefer Existing Protocols

   REQUIREMENT(S):  The DECADE Server discovery mechanism SHOULD prefer
       to use
       leverage 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.

7.  Discussion

7.1.  Non-IAP  Non-DECADE Internal Protocols

   Sometimes, several logical in-network storage systems 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). DECADE protocol(s).

7.2.  Fairness

   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

7.3.  Removal of Duplicate Data Objects

   There are actually two possible scenarios.  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, a DECADE server may implement internal mechanisms to
   monitor for duplicate objects and use internal mechanisms to prevent
   duplication in internal storage.

   The second scenario is removing duplicates across a distributed set
   of DECADE servers.  DECADE does not explicitly design for this, but
   does offer a redirection mechanism (Section that is one
   primitive that may be used to support this feature in certain
   deployment scenarios.

7.4.  Gaming of the Resource Control Mechanism

   The particular resource control policy communicated by a DECADE
   protocol and enforced by the scheduling system of a DECADE
   implementation may be open to certain gaming by clients. for example
   by specifying many small peers to increase total throughput or
   inciting overload conditions at a DECADE server.  Identifying and
   protecting against all such opportunities for gaming is outside the
   scope of this document, but DECADE protocol(s) and implementations
   SHOULD be aware that opportunities ti to game the system may be

8.  Security Considerations

   The security model is an important component of DECADE.  It is
   crucial for users to be able to manage and limit distribution of
   content to only authorized parties, and the mechanism needs to work
   on the general Internet which spans multiple administrative and
   security domains.  Previous sections have enumerated detailed
   requirements, but this section discusses the overall approach and
   other considerations that do not merit requirements.

8.1.  Authentication and Authorization

   DECADE only uses authentication when allowing a particular client to
   access its own storage at a server.  DECADE servers themselves do not
   authenticate other clients which are reading/writing a client's own
   storage.  Instead, DECADE relies on clients to authenticate others to
   access its storage, and then communicate the result of that
   authentication to the DECADE server so that the DECADE server may
   implement the necessary authorization checks.

8.2.  Encrypted Data

   DECADE Servers provide the ability to write raw data objects (subject
   to any policies instituted by the owner/administrator if of the DECADE
   server, which are outside of the scope of this document).  Thus,
   DECADE clients may opt to encrypt data before it is written to the
   DECADE Server.  However, DECADE itself does not provide encryption of
   data objects other than is provided by Section

9.  IANA Considerations

   There are no IANA considerations with this document.

10.  References

10.1.  Normative References

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

10.2.  Informative References

              Song, H., Zong, N., Yang, Y., and R. Alimi, "DECoupled
              Application Data Enroute (DECADE) Problem Statement",
              draft-ietf-decade-problem-statement-03 (work in progress),
              March 2011.

              Alimi, R., Yang, Y., Rahman, A., Kutscher, D., and H. Liu,
              "DECADE Architecture", draft-ietf-decade-arch-02 (work in
              progress), July 2011.

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

   [PPLive]   "PPLive", <>.

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, Dirk Kutscher, Akbar Rahman, Xiao Zhu,
   Yunfei Zhang, and Jin Peng for contributions and general feedback.

Authors' Addresses

   Yingjie Gu
   No. 101 Software Avenue
   Nanjing, Jiangsu Province  210012

   Phone: +86-25-56624760

   David A. Bryan
   Polycom, Inc.


   Yang Richard Yang
   Yale University


   Richard Alimi