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rfc:rfc2552

Network Working Group M. Blinov Request for Comments: 2552 M. Bessonov Category: Informational C. Clissmann

                                                         Teltec UCD-CS
                                                               Ireland
                                                            April 1999
              Architecture for Information Brokerage
                      in the ACTS Project GAIA

Status of this Memo

 This memo provides information for the Internet community.  It does
 not specify an Internet standard of any kind.  Distribution of this
 memo is unlimited.

Copyright Notice

 Copyright (C) The Internet Society (1999).  All Rights Reserved.

Abstract

 This memo introduces a domain and supplier independent generic
 architecture for information brokerage, designed as part of the ACTS
 project GAIA (Generic Architecture for Information Availability).

1. Introduction

 Today a huge number of goods and services are offered on the
 electronic market by a large, and ever-increasing, number of
 suppliers.  However, there is still no efficient way for a customer
 to find a product or information, he/she is interested in and a
 supplier that can provide that product.  Customers and suppliers
 already can not deal with the quantity of available information by
 themselves.  The high heterogeneity of existing protocols, formats,
 and underlying networks also limits development of the electronic
 market.
 This results in a demand for brokerage systems that can work as
 intermediary entities between customers and content suppliers.
 Brokerage systems assist a customer during the trading process and
 hide the heterogeneity and distribution of information from the
 customer.  The design of domain and supplier independent generic
 architecture for such brokerage systems is an objective of the
 project GAIA (Generic Architecture for Information Availability).
 GAIA received part funding from the EU ACTS programme for Research
 and Technological Development.  The GAIA brokerage system allows a
 customer to

Blinov, et al. [Page 1] RFC 2552 GAIA April 1999

  1. search for a particular "product" (information, content or

services) that he/she is interested in

  1. locate the product, i.e. find supplier(s) from whom the product is

available

  1. order the product from the supplier
  2. receive delivery of the product by digital means
 All these actions are carried out by the broker in response to
 requests from the customer.  Broker services are accessible to the
 customer through the unified user interface.  The customer system
 does not have to support all the protocols involved in the trading
 process.
 Full specification of the GAIA Architecture is available in the GAIA
 Standard [1].  The GAIA Standard includes a description of the GAIA
 Reference Model, GAIA Functional Architecture, GAIA Standard
 Profiles, and specification of the GAIA interfaces.
 This memo does not aim to include the whole text of the GAIA
 Standard, but to present the basic ideas and concepts of this
 standard.
 The structure of this memo follows the structure of the GAIA
 Standard:
 1.  The GAIA Reference Model provides a common basis for the
     description and specification of brokerage systems, including the
     GAIA system.
 2.  The GAIA Functional Architecture defines functional elements of
     the GAIA Broker, their roles and relationships.
 3.  The GAIA Brokerage System Interfaces describes internal and
     external interfaces of the GAIA brokerage system.
 4.  The GAIA Standard Profiles specifies mandatory and optional
     profiles to which brokerage systems may conform.

2. The GAIA Reference Model

 The Generic Architecture for Information Availability (GAIA)
 Reference Model outlines the operations and actors involved in
 finding, ordering, and delivering physical and digital objects and
 services ("Products") in a global brokered distributed information
 environment.  It provides an overall view of the GAIA environment,
 and illustrates the respective roles of and relationships between its

Blinov, et al. [Page 2] RFC 2552 GAIA April 1999

 components.  Further work on standards and frameworks for individual
 components of the GAIA environment uses the model and terminology
 provided by the Reference Model.
 The GAIA environment is a collection of actors and functions that are
 combined to support a procedure for information and services
 discovery, order, and delivery.  The actors play roles in the
 procedure, including initiation and execution of the Actions which
 are combined to make up the overall transaction.  The GAIA
 architecture provides a standardised and widely applicable framework
 for the provision and implementation of the brokered search and
 retrieve applications in a large-scale networked environment.

2.1. GAIA Roles

 The GAIA model considers three principal roles that can be played by
 the GAIA actors.  These are the Customer, the Broker and the
 Supplier.  These Roles are shown in Figure 1 below.  It also
 considers a further class of active entities who play supporting
 roles in the Actions.  This latter class is known as GAIA "Helpers"
 and includes, for example, authentication and payment.  The actors
 are organisations and individuals in the supply chain.  Every GAIA
 actor plays at least one role at any given time.

2.1.1. The Customer

 The aim of the Customer is to obtain some Products or information
 about some Products.  The Customer role initiates the GAIA
 transaction by requesting one or more GAIA Actions, and receives the
 results of the transaction.  The Customer may deal with actors
 playing either of the other two roles: the Broker or the Supplier.
 These actors may themselves play the role of the Customer while
 requesting further services from other Brokers.

2.1.2. The Broker

 The Broker provides brokerage services to the Customer and the
 Supplier.  It responds to requests from the Customer to provide
 Products, or information about Products.  The Products that the
 Broker supplies to the Customer may originate from one or more
 Suppliers and/or Brokers.  The Broker's primary role is to act as a
 collector and collator of information from a number of different
 Suppliers, and to supply this information to the Customer, thus
 obviating the need for the Customer to deal with a variety of
 Suppliers.  A Broker can also be considered to act on behalf of a
 Supplier, distributing information about the Products available.  The
 actor playing the role of the Broker may play the role of a Supplier

Blinov, et al. [Page 3] RFC 2552 GAIA April 1999

 to a Customer or other Broker at the same time.  The Broker may play
 the role of a Customer while interacting with another Broker or with
 a Supplier.

2.1.3. The Supplier

 The Supplier is the source of the Product supplied to the Customer.
 The Supplier provides the Broker with information about the Product
 that it can supply.  The Supplier may supply its Product directly to
 the Customer, or to the Broker for forwarding to the Customer.  An
 actor playing the role of a Supplier may also play the role of a
 Broker.  A Supplier may deal with a large number of Brokers and
 Customers over a number of GAIA transactions.

2.1.4. Helpers

 A Helper is an application layer entity playing a supporting role in
 a GAIA transaction.  Helpers provide some service needed in the
 supply chain, but outside the core functionality of the Broker.
 Examples include a global directory service, payment service, or
 authentication service.
 The authentication Helper is concerned with facilitating the
 authentication of one actor to another.
 The payment Helper is concerned with supporting a mechanism for
 payment to one actor by another.
 In any given GAIA transaction, there will be one or more Customers
 (usually one), one or more Brokers, and one or more Suppliers.  A
 description of the Product sought by the Customer is provided by the
 Customer to the Broker.  The Broker may involve other Brokers in the
 search for the Product.  When a Supplier of the Product is discovered
 by the Broker, this information is included in the response of the
 Broker to the Customer.  During the course of the Action, it may be
 necessary to call upon the services of one or more Helpers.

2.2. GAIA Actions

 Each GAIA transaction is made up of one or more Actions.  These
 Actions are requests by the Customer to the Broker or the Supplier to
 carry out some operation and to return a response.  Four Actions are
 defined:
  1. Search
  2. Locate
  3. Order
  4. Deliver

Blinov, et al. [Page 4] RFC 2552 GAIA April 1999

 These Actions are shown in Figure 1.
 +--------+    .   .    +--------+    .   .    +-----------+
 |        |-- Search -->|        |-- Search -->|           |+
 |        |    :   :    |        |    :   :    |           ||
 |        |-- Locate -->|        |-- Locate -->|           ||
 |Customer|    :   :    | Broker |    :   :    |Supplier(s)||
 |        |-- Order --->|        |-- Order --->|           ||
 |        |    :   :    |        |    :   :    |           ||
 |        |<- Deliver --|        |<- Deliver --|           ||
 +--------+    :   :    +--------+    :   :    +-----------+|
               :   :                  :   :     +-----------+
              Helpers                Helpers
           <Authentication> <Payment> <Security>
 Figure 1 GAIA Roles and Actions

2.2.1. Search

 The Search Action is carried out when the Customer asks the Broker to
 find some information on its behalf.  To do this, the Customer
 provides the Broker with some description of the Product it requires.
 On the basis of this description, the Broker carries out a search on
 behalf of the Customer and returns the result.  The result of a
 Search Action is a set of unique identifiers referencing the Products
 matching the description provided by the Customer.

2.2.2. Locate

 The Locate Action is carried out when the Customer asks the Broker to
 provide it with information regarding the location and source of some
 Product.  To allow the Broker to do this, the Customer provides an
 unambiguous identification of the Product, which may be the result of
 a Search Action.  The Broker returns information to the Customer
 about a source or sources for the Product.  These data include the
 Terms of Availability information such as available methods of
 delivery, time of delivery, costs, etc.  However, this information
 can not be considered final since some special terms and conditions
 may apply, e.g. discounts for some categories of Customers.  The
 final version of the Terms of Availability is established during the
 negotiation phase of the Order Action.

2.2.3. Order

 The Order Action is carried out when the Customer asks the Broker to
 obtain a Product on its behalf, or asks the Supplier to sell the
 Product directly to the Customer.  To enable an Order, the Customer
 provides the Broker/Supplier with Product source information, which

Blinov, et al. [Page 5] RFC 2552 GAIA April 1999

 may be a result of a Locate Action.  The Order Action consists of a
 negotiation phase and (possibly) a purchase phase.  During the
 negotiation phase the Customer obtains the quotation that contains
 the final version of the Terms of Availability for the (batch of)
 Products he is considering purchasing.  If the Customer finds these
 conditions satisfactory, he commits to the purchase.  Alternatively,
 if the Broker or Supplier supports telepresence services for the
 human interaction with the Supplier or Broker representatives, these
 may be used during the negotiations.

2.2.4. Deliver

 The Deliver Action is carried out when the Broker provides the
 Customer with some requested Product.  The Product may be
 information, some physical object, or metadata.  The Deliver Action
 may be in response to an Order Action, a Search Action, or a Locate
 Action.
 While the Actions presented in this section may logically be taken to
 form an integrated sequence, this is not necessarily the case.
 Actions may take place independently, rather than as a part of a
 four-Action whole.  For example, Order and Deliver Actions may occur
 on the basis of information obtained by the Customer using some other
 mechanism than GAIA Search and Locate Actions.

2.3. GAIA Helper Events

 During any of the GAIA Actions outlined above, it may be necessary to
 carry out some supporting activity.  These activities are called GAIA
 Helper events.  They include, for example, authentication and
 payment.  The Helper entities are involved in the GAIA events to
 provide services, additional to the GAIA Actions, to the GAIA actors.
 Authentication
 In order to verify the identity of one GAIA actor to another, an
 authentication exchange may need to take place.  This may occur
 during any of the GAIA Actions.  The manner or method of
 authentication is outside the scope of this document.
 Payment
 It may be necessary for payment to take place during a GAIA
 transaction.  In this situation, one GAIA actor pays one or more
 other GAIA actors.  The manner or method of payment is outside the
 scope of this document.

Blinov, et al. [Page 6] RFC 2552 GAIA April 1999

 Security
 As part of any GAIA Action, it may be necessary to carry out some
 security operations, such as encryption of data, verification of
 source and content integrity of Product, or digital signature of some
 data entity or entities.  The particular security services and
 mechanisms which may be required, or the manner in which they may be
 provided, is outside the scope of this document.

3. The GAIA Functional Architecture

3.1. The Concept

 The GAIA Functional Architecture decomposes the overall functionality
 of the GAIA Broker into a number of components and describes the
 roles and relationships of these components, and the manner in which
 they interoperate.
 To work in a heterogeneous environment the GAIA Functional
 Architecture introduces three levels of abstract elements of the
 Broker: the Kernel, Functional Unit Managers (FUMs), and Functional
 Units (FUs) (see Figure 2).
     GAIA Broker:
     ------------
                    [  Kernel  ]                Kernel
                      /       \                 level
                     /         \
      [Functional Unit]     [Functional Unit]   Technology-independent
      [    Manager    ]     [    Manager    ]   action-dependent
           /    \                 /    \        level
          /      \               /      \
  [Functional][Functional] [Functional][Functional]  Technology
  [Unit      ][Unit      ] [Unit      ][Unit      ]  dependent
                                                     level
  Figure 2 Levels of the architecture
 Functional Units are the technology dependent parts of the
 architecture.  They perform required transactions in terms of a
 particular protocol.  All FUs are covered by a technology independent
 interface.  FUs are grouped according to the trading action they
 participate in, e.g. search FUs or locate FUs.  Each group of FUs is
 governed by the corresponding Functional Unit Manager.
 Functional Unit Managers contain technology independent functions for
 particular actions.  To use a particular technology an FUM uses the
 services of attached FUs.  There may be several FUs associated with
 an FUM, allowing the FUM to operate in different technology contexts.

Blinov, et al. [Page 7] RFC 2552 GAIA April 1999

 There is one FUM in the system for every area of functionality, e.g.
 search, locate, and order.  The Kernel is responsible for managing
 the activity of different FUMs (corresponding to different actions)
 and synchronising events between them.
 The GAIA Functional Architecture establishes relationships between
 the existing technologies (standards and protocols) that are combined
 in the GAIA Standard, in the context of a brokerage system.  It is to
 be expected that new technologies will evolve which will be viable
 alternatives to those selected.  The abstract and modular nature of
 the Functional Architecture allows the replacement of one technology
 with a new one without disruption to the rest of the brokerage
 system.

3.2. Functional Units

 The brokerage system provides a number of services to its users.
 These services are supported by the functions of the brokerage
 system.  These include, for example,
  1. searching
  2. ordering
  3. payment
 Each of these functions can be provided by a number of different
 candidate technologies.  However, the operations that are required to
 be carried out remain the same.  Regardless of the selected
 technologies, the functional requirements do not change.  The
 required operations are described in terms of abstract primitives,
 which can be mapped to the protocol instructions of the technology
 selected to support the function.  A mapping component, called a
 Functional Unit (FU), is defined for each candidate technology, and
 converts calls to abstract primitives into protocol instructions.
 The FU acts as an adaptor between its particular technology and the
 rest of the brokerage system.
 Functional Units are defined for each candidate technology that can
 be used to fulfil a particular functional need of the brokerage
 system.  A Functional Unit accepts abstract primitive invocations,
 and maps them to calls to the particular technology to which it is
 dedicated.  The results of these calls are translated into the
 corresponding abstract primitives and returned by the FU, as shown in
 Figure 3.

Blinov, et al. [Page 8] RFC 2552 GAIA April 1999

  • The rest of the Broker *

^

                  |  -abstract primitives
                  v
               +------------+
               | Functional |
               |    Unit    |
               +------------+
                  ^
                  |  -technology-specific commands
                  v
           * Technology functions *
 Figure 3 GAIA Functional Unit

3.3. Functional Unit Managers

 As noted above, a number of different candidate technologies can be
 used to fulfil a particular functional requirement of the brokerage
 system.  Depending on the details of the GAIA transaction (underlying
 network, Customer system capabilities, etc.), different technologies
 may be more useful during different transactions.  As a result, each
 candidate technology has its own Functional Unit, which is invoked
 when that particular technology is required.
 A number of different Functional Units can exist which fulfil the
 same functional requirement of the brokerage system.  To select the
 most appropriate FU (and technology), the brokerage system needs to
 know which is the most useful at any particular time; in general this
 is the technology supported by the target Supplier system.  This is
 the responsibility of the Functional Unit Manager, or FUM.  Each
 function of the brokerage system has a single FUM, which is invoked
 using abstract primitives by the Broker Kernel.  This FUM selects the
 most appropriate of the candidate technologies, and calls the
 corresponding FU (see Figure 4).
 The interface between the FUM and the corresponding FUs is defined
 for every FUM in an open, platform independent, and programming
 language independent manner.  These interfaces do not depend on any
 particular technology.  It allows for configuring the set of
 technologies supported by the Broker, by attaching different subsets
 of FUs.  If a new technology is to be supported by a Broker, a new FU
 implementing this technology can be created according to the
 specification of the interface, and attached to the corresponding
 FUM.

Blinov, et al. [Page 9] RFC 2552 GAIA April 1999

           +--------------------------------------+
           |       Functional Unit Manager        |
           +--------------------------------------+
                  ^                       ^
                  | -abstract primitives- |
                  v                       v
             +------------+        +------------+
             | Functional |        | Functional |
             |    Unit    |        |    Unit    |
             +------------+        +------------+
              ^                                ^
              | -technology-specific commands- |
              v                                v
            * Technology *          * Technology *
            * functions  *          * functions  *
 Figure 4 Functional Unit Manager

3.4. The Kernel

 The Kernel of the brokerage system acts as a bus for the transmission
 of abstract primitives between FUMs.  Each FUM imports a set of
 abstract primitives representing those services which the FUM expects
 to receive from some other part of the system.  The services that the
 FUM is prepared to provide to other elements of the brokerage system
 are presented in the form of exported abstract primitives.  All these
 abstract primitives are imported from, and exported to, the Kernel
 (see Figure 5).
 The Kernel is also responsible for synchronisation of different
 actions within a transaction and for maintaining a common context
 between actions.
           +-------------------------------------+
           |           Broker Kernel             |
           +-------------------------------------+
                ^            ^              ^
                | -abstract- | -primitives- |
                v            v              v
            +-------+     +-------+     +-------+
            |  FUM  |     |  FUM  |     |  FUM  |
            +-------+     +-------+     +-------+
 Figure 5 Broker Kernel

Blinov, et al. [Page 10] RFC 2552 GAIA April 1999

3.5. Description of FUMs

 The core activities of the brokerage system include:
 1.  searching for Products that fit a user description
 2.  sourcing Products the identification of which is known
 3.  allowing users to order Products
 4.  delivering information in item format
 5.  delivering information as a continuous media stream
 6.  providing a user interface to the brokerage services
 7.  alerting users as to the availability of information
 8.  interacting with external directory services
 9.  authentication of other actors
 10.  payment operations
 Each of these activities is carried out by the corresponding FUM as
 described below and shown in Figure 6.
 Search FUM
 The Search FUM accepts requests to carry out a search for Products
 that fit a particular user description.  It returns lists of
 identifiers of Products that fit the description.
 Locate FUM
 The Locate FUM accepts Product identifiers and discovers where they
 may be obtained.  It returns lists of Suppliers and locations for the
 Product.
 Order FUM
 The Order FUM manages negotiations between a Customer and a Supplier
 in order that agreement may be reached on the terms of availability
 of a particular Product or group of Products.  Following the
 negotiation phase, the Order FUM accepts purchase commitments from
 the Customer and forwards them to the Supplier.  It returns a
 notification of the status of the Order Action.

Blinov, et al. [Page 11] RFC 2552 GAIA April 1999

                      The GAIA Broker:
                      ----------------
 (Customer))   (Alerting))  (  DS   ))  (Auth))  (Payment))
 (   FUs  ))   (   FUs  ))  (  FUs  ))  ( FUs))  (  FUs  ))
 (e.g.HTTP))   (e.g. SMS))  (eg LDAP))  (    ))  (e.g.SET))
     \/            \/           \/        \/        \/
 [Customer]     [Alerting]    [ DS  ]  [ Auth ]  [Payment]
 [  FUM   ]     [  FUM   ]    [ FUM ]  [  FUM ]  [  FUM  ]
     |              |            |         |         |
  +----------------------------------------------------------+
  |                  Broker Kernel                           |
  +----------------------------------------------------------+
     |             |            |            |            |
 [ Search ]    [ Locate ]    [ Order ]   [ Stream ]   [Discrete]
 [  FUM   ]    [  FUM   ]    [  FUM  ]   [Delivery]   [Delivery]
 [        ]    [        ]    [       ]   [  FUM   ]   [  FUM   ]
     /\            /\           /\           /\           /\
 ( Search  ))  ( Locate  ))  (  Order   ))  ( SD   ))  ( DD   ))
 (   FUs   ))  (   FUs   ))  (  FUs     ))  ( FUs  ))  ( FUs  ))
 (eg Z39.50))  (eg Z39.50))  (eg ISO ILL))  (eg RTP))  (eg FTP))
 Figure 6 GAIA Functional Architecture
 Discrete Delivery FUM
 The Discrete Delivery FUM manages the delivery of discrete items to
 the Customer.
 Stream Delivery FUM
 The Stream Delivery FUM manages the delivery of real-time multimedia
 data streams to the Customer.
 Customer FUM
 The Customer FUM provides an interface to support the Customer's
 systems interaction with the brokerage system.
 Alerting FUM
 The Alerting FUM notifies Customers about changes that may interest
 them.
 Directory Services FUM
 The Directory Services FUM provides an interface between an external
 directory service and the brokerage system.

Blinov, et al. [Page 12] RFC 2552 GAIA April 1999

 Authentication FUM
 The Authentication FUM provides a mechanism that allows a user to
 prove his identity to the brokerage system.
 Payment FUM
 The Payment FUM provides a mechanism for payment from one actor to
 another.

4. GAIA Brokerage System Interfaces

 This Chapter describes the internal and external interfaces of the
 GAIA brokerage system.

4.1. Internal Interfaces

 The definition of communication between functional components within
 the GAIA Broker is based on the OMG CORBA model [2].  Interfaces
 between components are defined in the IDL language specified by OMG.
 Interface calls are passed between components by the Object Request
 Broker (ORB).
 The advantage of this approach is that the specifications of the
 interfaces are platform and programming language independent.  These
 interfaces can be implemented using different programming languages
 on different platforms.  All necessary conversions during interface
 invocations are transparently performed by an ORB.  The CORBA model
 also allows installing different functional components of the GAIA
 Broker on different computers connected by a network.  Interface
 calls will be transferred over the network by an ORB transparently
 for the application.
 The specification of the interfaces between the Kernel and FUMs and
 between each FUM and corresponding FUs is presented in the GAIA
 Standard [1].

4.2. External protocols

 The GAIA Broker can use existing protocols to communicate with other
 actors.  For example, it can use HTTP for interactions with
 Customers, Z39.50 for search, etc.  As described in the GAIA
 Functional Architecture, support for particular technologies is
 provided by FUs.  A set of supported protocols can be extended by
 attaching the corresponding new FUs to a Broker.  The GAIA Broker can
 support several protocols for each action.  The FUMs will select the
 most appropriate protocol for a transaction.  The more protocols
 supported by the Broker, the better service it can provide to

Blinov, et al. [Page 13] RFC 2552 GAIA April 1999

 Customers and Suppliers.
 The GAIA Standard does not limit the set of protocols supported by
 the Broker.  However, for the purpose of interoperability, it
 specifies several GAIA profiles.  These profiles define a common
 subset of protocols (and a common range of protocol parameters) that
 Brokers are encouraged to support in order to make communication
 between GAIA Brokers, and with GAIA-aware Suppliers and Customers,
 possible.
 Existing protocols are not the only way to contact the GAIA Broker.
 The GAIA interfaces have been designed as a generalisation of
 existing interfaces and protocols, so they provide more functionality
 than any particular protocol.  To give access to the full
 functionality of the GAIA Broker, the GAIA Standard allows users
 (Customers and other Brokers) to directly use the CORBA-defined
 Customer interface of the GAIA Broker (interface between the Customer
 FUM and FUs) as shown in Figure 7.  In this case, the Customer system
 gets access to the Customer interface of the Broker using the service
 of an underlying ORB, and can request operations by calling the
 corresponding methods of the interface.  The Customer interface of
 the GAIA Broker is specified in the GAIA Standard [1].
 Where Customer and Supplier systems are not CORBA-aware, they can
 communicate with a GAIA Broker using existing protocols.  If,
 however, they can use the service of an ORB, they are encouraged to
 communicate with a Broker by connecting to its Customer interface.
 This method allows for avoiding convergence between a particular
 protocol and the GAIA interface.  The former method makes
 interactions with all existing types of Customers and Suppliers
 possible using existing and widespread protocols.  The later method
 has been designed to achieve maximum functionality by using native
 GAIA methods for communication with Customers and Suppliers.

Blinov, et al. [Page 14] RFC 2552 GAIA April 1999

                            +----------------+
                            |Broker          |
                            |                |
                            |   --------     |
    +-----------+           |  [ Kernel ]    |
    |  Broker   |           |   --------     |
    |    or     |           |  [Customer]    |
    | Customer  |           |  [  FUM   ]    |
    |           |           |  ========== <-GAIA Customer
    |        *  |           |  *       *     | \interface
    | { O R B *}* * * * * * *{* O  R  B * }  |
    +-----------+    iiop   |            *   |         +----------+
                            |     (Customer) |         | Customer |
                            |     (   FU   ) |         |          |
                            +------------I---+         +----I-----+
                                          \      HTTP      /
                                           - - -      - - -
    Figure 7 External protocols and the GAIA Customer interface

5. GAIA Standard Profiles

 The GAIA Standard defines a number of profiles, which a Broker may
 support in order to achieve interoperability with other GAIA actors
 (Customers, Suppliers and other Brokers).  The complexity of the
 profile chosen by a Broker depends on the level and type of service
 which the Broker wishes to deliver in a GAIA-conformant manner.  The
 higher the level of service that a Broker provides to a Customer, and
 the greater the length of the supply chain which the Broker wishes to
 support, the more advanced the profile and/or the greater the number
 of extension modules the Broker must support.

5.1. Supply Chains

 The GAIA profile definition approach is based on the possible types
 of supply chain that a brokerage system can be a part of.
 The operations of a brokerage system can be broken into three
 categories:
  1. interactions with the Customer
  2. interactions with other Brokers
  3. interactions with Suppliers
 The first and last of these occur at the two ends of a supply chain,
 while interbroker operations take place at other points in the chain.
 The supply chain may take a number of different forms:

Blinov, et al. [Page 15] RFC 2552 GAIA April 1999

  1. a minimal chain, where the Customer and the Broker are the ends of

the chain and there are no intervening links. In this case, the

   Broker plays the role of Supplier to the Customer.
  1. a three-piece chain, where the Broker deals with the Customer and

the Supplier but not with any other Broker.

  1. a longer chain, with one or more interbroker operations.
    Minimal Supply Chain:
        +--------+         +-------------+
        |Customer| <=====> | Broker      |
        +--------+         |(as Supplier)|
                           +-------------+
    3-piece Supply Chain:
        +--------+       +--------+       +--------+
        |Customer| <===> | Broker | <===> |Supplier|
        +--------+       +--------+       +--------+
    Longer Supply Chain:
        +--------+       +--------+   +--------+       +--------+
        |Customer| <===> | Broker |<=>| Broker | <===> |Supplier|
        +--------+       +--------+   +--------+       +--------+
    Figure 8 Supply Chains

5.1.1. Minimal Supply Chains

 As discussed in the GAIA Reference Model, a GAIA transaction is
 composed of a number of actions, such as search, order, and delivery.
 Each transaction is initiated by the Customer who makes a request to
 the Broker.  In the event that the Broker is able to fulfil the
 request, the transaction involves no other actors.
 In this simple case, the GAIA transaction involves the Customer and
 the Broker.  The only protocol which needs to be standardised is that
 between the Customer and the Broker.  This is specified in the GAIA
 Standard Minimal profile below.

5.1.2. Longer Supply Chains

 In the event that the Broker is not able to fulfil a request, the
 action may be propagated on to other Brokers, with the original
 Broker playing the Customer role.  Each of these Brokers may in turn
 propagate the request if they cannot fulfil it.
 Eventually, if the action is successful, a Supplier will be found who
 can fulfil the request.  The supply chain is thus made up a single
 Customer, one or more Suppliers, and one or more Brokers.

Blinov, et al. [Page 16] RFC 2552 GAIA April 1999

 In order to propagate an action from one Broker to another, a
 standardised communication protocol must be defined for broker-broker
 interaction.  This is specified in the Basic profile, below.  This
 profile is based on CORBA.
 Supplier and Brokers, however, are not obliged to support the Basic
 profile of the GAIA Standard.  They may instead use another, more
 traditional, protocol such as Z39.50 for discovery, or ISO ILL for
 ordering.  The Extension Modules to the GAIA Standard specify the
 profiles to be used for various brokerage functions.

5.2. Introduction to the GAIA Standard Profiles and Modules

 The profiles specified are
  1. The Minimal profile, which is the very least to which a GAIA Broker

must conform

  1. The Basic Profile, which allows inter-broker communication
  2. A number of Extension Modules, which allow the Broker to provide

various services, and to interoperate with Suppliers, Brokers and

   Customers using protocols specified in the modules
 - A set of Interface Modules, that defines which particular
   Functional Unit CORBA interfaces are supported by the Broker
 Each Broker must conform at least to the Minimal profile to provide a
 web-based user interface.  In addition, to take part in inter-broker
 communications, the Basic profile is recommended.  For interaction
 with non-CORBA-aware entities, and for the use of advanced services,
 there are other modules of the standard to which the Broker may
 conform.  These are denoted "Extension Modules", and they
 characterise the protocols and standards in a particular area of
 functionality.  A Broker can choose an appropriate set of Extension
 Modules to conform to according to the functionality it wishes to
 achieve.
 The GAIA Standard specifies all interfaces between FUM and FUs for
 the GAIA Broker.  However, it would be too much to require every
 Broker to implement all of them.  The GAIA Standard decomposes all
 interfaces into a number of Interface Modules.  A Broker can choose a
 subset of Interface Modules that are more important in its area of
 operation, and implement interfaces defined in these modules.  These
 interfaces are important only inside the broker system and do not
 play any role in communication with other GAIA actors.  However, a
 declaration of supported interfaces is important for the
 administrator to find the areas in which the functionality of the
 Broker can be extended by attaching GAIA-conformant FUs.

Blinov, et al. [Page 17] RFC 2552 GAIA April 1999

5.3. Minimal Profile

 The minimum functionality that a Broker must support will allow it to
 provide services to the Customer as a part of a minimal chain.  In
 this case, what is required of the Broker is simply a user interface
 for the Customer.  Any further operations take place within the
 Broker, and so do not come within the scope of the standard.
 The Minimal profile requires the Broker to implement a user interface
 based on the HTTP 1.1 protocol, defined in RFC 2068 [3], and HTML
 2.0, defined in RFC 1866 [4].  It means that a Customer should be
 able to access the basic functionality of the GAIA Broker by using a
 HTTP 1.1 and HTML 2.0 conformant web-browser.
 It should be possible for Customers to locate a GAIA Broker.  Thus a
 GAIA Broker should be registered in a Directory Service using a
 schema specified in the GAIA Standard [1].
 +-------------------------------------------------+
 | Minimal Profile                                 |
 +------------------------+------------------------+
 | Customer               | HTTP 1.1 (server),     |
 |                        | HTML 2.0               |
 +------------------------+------------------------+

5.4. Basic Profile

 While the minimal functionality is sufficient to allow a Broker to
 function, an important aspect of any GAIA Broker functionality is
 dealing with other Brokers.  The goal of the Basic profile is to
 achieve federation between Brokers.  Every GAIA Broker can use the
 service of other GAIA Brokers in order to fulfil a request of a
 Customer.  That Broker in turn can use the service of the third GAIA
 Broker.  So every request can be chained by several Brokers.  This
 extends the abilities of every GAIA action (Search, Locate, Order,
 etc.).  Chained transactions are particularly important in the
 discovery phase of a transaction, where a Broker unable to fulfil a
 particular information requirement passes on the search to another
 Broker.
 The Basic profile requires the Broker to implement the GAIA Customer
 interface defined in terms of CORBA.  This interface is described in
 more detail in Section 4.2 above.  The Basic profile also requires
 the Broker to implement interface requestor procedures, i.e. to be
 able to connect to the Customer interfaces of other Brokers.  The ORB
 used by the Broker should be conformant to the CORBA 2.0
 specification [2] and use IIOP protocol for inter-ORB communications
 [2].

Blinov, et al. [Page 18] RFC 2552 GAIA April 1999

 A full specification of the GAIA Customer interface is presented in
 the GAIA Standard [1].
 A GAIA Broker should be able to find other Brokers and Suppliers.  It
 should also allow other participants to find it.  Thus a GAIA Broker
 should support a directory service.  The Basic profile includes a
 directory access protocol for this purpose.  The actual choice of
 protocol is not standardised, because the choice does not influence
 the success of the Broker's inter-operation with other Brokers.  The
 directory schema, which should be used, is specified in the GAIA
 Standard.
 The Basic profile suggested for a Broker to allow it to interoperate
 with other GAIA Brokers is as follows.
 +----------------------------------------------------------------+
 | Basic Profile                                                  |
 +------------------------+---------------------------------------+
 | Customer               | GAIA Customer interface/IIOP (server) |
 | Search and Locate      | GAIA Customer interface/IIOP (client) |
 |        (Discovery)     |                                       |
 | Order                  | GAIA Customer interface/IIOP (client) |
 | Directory              | Some directory access protocol,       |
 |                        | such as LDAP                          |
 +------------------------+---------------------------------------+

5.5. Extension Modules

 In order to allow Brokers to interoperate with other Brokers that do
 not support the Basic profile, and to allow Brokers to deal with
 Suppliers and Customers who are not CORBA-aware, as well as to allow
 delivery of items and data streams via the Broker, other open
 technologies are suggested as extensions to the Basic and Minimal
 profiles.  These technologies reflect the results of the technology
 evaluation carried out as part of the project GAIA.
 The extra protocols are grouped into Extension Modules.  Support of
 these Extension Modules is optional.  A Broker can choose an
 appropriate set of Extension Modules to conform to according to the
 functionality it wishes to achieve.  There is one Extension Module
 for each of the functional areas which are not covered by the Basic
 and Minimal Profiles, and also one Extension Module for each of the
 existing areas (Customer, Discovery, and Order) to allow the use of
 protocols other than GAIA abstract primitives.

Blinov, et al. [Page 19] RFC 2552 GAIA April 1999

 The following Extension Modules are defined.
  1. Discovery Extension Module
  2. Order Extension Module
  3. Discrete Delivery Extension Module
  4. Stream Delivery Extension Module
  5. Security Extension Module
  6. Payment Extension Module
  7. Alerting Extension Module
  8. Customer Discovery Extension Module

5.5.1. Discovery Extension Module

 The Discovery Extension Module specifies the technologies to be used
 in searching for and locating products and services.
 This Extension Module requires the Broker to support the client part
 of the Z39.50 protocol, as defined in [5].  The following subset of
 the protocol is required:
  1. Init, Search, and Present services
  2. GRS-1 record syntax
 Z39.50 protocol PDUs should be carried using TCP/IP network
 protocols.
 +-------------------------------------------------+
 | Discovery Extension Module                      |
 +------------------------+------------------------+
 | Searching,             | Z39.50 (client)        |
 | Locating               |                        |
 +------------------------+------------------------+

5.5.2. Order Extension Module

 The Order Extension Module specifies the protocols to be used to
 order products and services from a Supplier.
 This Extension Module requires the Broker to support all mandatory
 services of the client part of the ISO ILL protocol [6].  Basic
 conformance criteria should be adhered to.  ISO ILL protocol PDUs
 should be carried using TCP/IP network protocols.

Blinov, et al. [Page 20] RFC 2552 GAIA April 1999

 +-------------------------------------------------+
 | Order Extension Module                          |
 +------------------------+------------------------+
 | Order                  | ISO ILL (client)       |
 +------------------------+------------------------+

5.5.3. Discrete Delivery Extension Module

 The Discrete Delivery Extension Module specifies the protocols and
 standards to be used for the delivery of on-line products and
 services to the Customer.  There are two delivery scenarios
 considered
  1. Direct Supplier to Customer delivery

The delivery may be a single-step operation, with the Supplier

   supplying his product directly to the Customer without the
   involvement of any Broker in the delivery process.  The Broker may
   have acted to refer the Customer to the Supplier.  In this case,
   where the Broker is not involved in delivery, the Discrete Delivery
   Extension Module does not apply.
  1. Delivery over a supply chain with one or more Brokers involved

In the event of the Broker being the central link in a supply chain

   of the form of Supplier-Broker-Customer, the Broker will use the
   protocols specified in the Discrete Delivery Extension Module to
   receive the product from the Supplier, and to provide the product
   to the Customer.
 The Discrete Delivery Extension Module requires the Broker to provide
 both FTP client and FTP server functionality [7], to allow the Broker
 to receive and to transmit files using FTP.
 The Discrete Delivery Extension Module also requires the GAIA Broker
 to be able to accept and to generate e-mail messages.  The e-mail
 protocol specified is Internet e-mail, based on the SMTP protocol [8]
 and mail data formats specified in RFC 822 [9].  This protocol is
 sufficient for the creation, transmission, and management of textual
 e-mail messages.  However, for the transmission of data files of
 various types, extensions to the SMTP/RFC822 protocols are required.
 The mail extensions specified by the Discrete Delivery Extension
 Module are based on MIME (Multipurpose Internet Mail Extensions),
 defined in RFCs 2045-2049 [10].  Thus a GAIA Broker must be able to
 send and receive "simple" SMTP/RFC822 mail, and also be able to deal
 with RFC 2045-2049 MIME mail extensions.
 For electronic document delivery the Discrete Delivery Extension
 Module requires the support of GEDI version 3.0.

Blinov, et al. [Page 21] RFC 2552 GAIA April 1999

 +--------------------------------------------------------+
 | Discrete Delivery Extension Module                     |
 +------------------------+-------------------------------+
 | FTP profile            | FTP (client+server)           |
 | Email profile          | Internet e-mail [SMTP,RFC822] |
 |                        |   (receiver+sender),          |
 |                        | MIME                          |
 | Document delivery      | GEDI version 3.0              |
 +------------------------+-------------------------------+

5.5.4. Stream Delivery Extension Module

 This Extension Module is intended to support real-time delivery of
 multimedia by the GAIA Broker.
 Several scenarios of stream delivery are considered.  A stream can be
 delivered
  1. directly from a Supplier to a Customer

The Broker does not take part in the stream delivery process; this

   scenario is out of scope of this standard.
  1. from a Supplier to a Customer via a Broker

The Broker can add value to the stream delivery process by

   implementing cache algorithms, mixing streams, branching one stream
   to several Customers, etc.
  1. from a Broker to a Customer

The Broker can keep a small amount of multimedia data (e.g. audio

   examples) in its own database and deliver it to a Customer upon
   request.
 The Stream Delivery Extension Module is recommended to be implemented
 by a Broker in order to provide the last two scenarios of real-time
 multimedia delivery.
 The Stream Delivery Extension Module requires the Broker to support
 the following technologies:
  1. Compression

MPEG-2 Audio Layer 3, specified in ISO/IEC 13818-3 [11]. Only

   support of constrained parameter streams (CSPS) is required.
  1. Data transfer protocol

RTP protocol over UDP/IP, defined in RFC 1889 [12] (both client and

   server parts).  It is recommended that the full behaviour of an RTP
   application service entity ("translator" or "mixer") is supported
   but it is not required.

Blinov, et al. [Page 22] RFC 2552 GAIA April 1999

  1. Mapping

RTP payload format for MPEG Audio (MPA), defined in RFC 2250 [13].

  1. Session control protocol

RTCP, specified in RFC 1889 [12].

 This profile provides delivery of high quality audio over networks
 with non-guaranteed quality of service such as the Internet.
 +----------------------------------------------------+
 | Stream Delivery Extension Module                   |
 +--------------------------+-------------------------+
 | Compression              | MPEG-2 Audio Layer 3    |
 | Data transfer            | RTP (client+server)     |
 | Mapping                  | RFC 2250                |
 | Session control protocol | RTCP                    |
 +--------------------------+-------------------------+

5.5.5. Security Extension Module

 The basic security services required for GAIA are
  1. Authentication of users, remote servers (both as entity

authentication and as bilateral peer-to-peer authentication),

   senders and receivers in network transactions, as well as the
   authentication of documents.  Authentication is required for three
   situations: authentication at the user workstation when starting
   the session, authentication in a local environment (client/server
   authentication) and authentication in a global, open network
   (Internet).
  1. Confidentiality and integrity of all resources transferred over the

network or handled locally at application servers and user

   workstations.
  1. Control of access to services and resources.
  1. Non-repudiation of transactions, participants, and sensitive

documents.

 This module allows a Broker to secure communications with other
 participants.  It provides channel security, authentication, and
 certificate exchange.
 The Security Extension Module specifies the following protocols and
 algorithms:
  1. Privacy, integrity, non-repudiation

Blinov, et al. [Page 23] RFC 2552 GAIA April 1999

   SSL v3.0 protocol, defined in [14].
   PKCS #7, defined in [15].
  1. Remote, client/server authentication

GSS v5, specified in RFC 1508 [16].

  1. Certification services

PKIX certification protocol, specified in [17].

 +-----------------------------------------------------------+
 | Security Extension Module                                 |
 +--------------------------------------+--------------------+
 | Privacy, integrity, non-repudiation  | SSL v 3.0, PKCS #7 |
 | Remote, client/server authentication | GSS v5             |
 | Certification services               | PKIX certification |
 |                                      |      protocol      |
 +--------------------------------------+--------------------+

5.5.6. Payment Extension Module

 This module allows a Broker to perform electronic payment operations
 with Customers, Suppliers, and other Brokers.  Such operations may take
 place at any stage during a GAIA transaction, during a Search, Locate,
 Order, or Deliver Action.
 The GAIA Standard does not specify the tariffing or charging model to
 be used by a Broker; this is considered to be an internal matter.
 However, when a bill has been agreed, payment must take place in a
 secure and mutually acceptable manner.  The payment procedure specified
 in the GAIA Standard makes use of the SET specification.
 The Payment Extension Module requires a Broker to support SET v1.0
 merchant's server and SET certification protocol, specified in [18].
 +----------------------------------------------------+
 | Payment Extension Module                           |
 +------------------------+---------------------------+
 | Payment                | SET v 1.0 :               |
 |                        | 1) CA server for banks    |
 |                        | 2) Cardholder wallet      |
 |                        | 3) Merchant Server        |
 |                        | 4) Payment Gateway server |
 +------------------------+---------------------------+

Blinov, et al. [Page 24] RFC 2552 GAIA April 1999

5.5.7. Alerting Extension Module

 The Alerting Extension Module specifies the protocols to notify
 Customers about changes that can be interesting for them.
 This Extension Module requires the support of the following
 technologies:
  1. Internet e-mail, based on SMTP protocol [8],

and mail data formats specified in RFC 822 [9].

   The Broker should be able to generate and send e-mail messages.
 - SMS (Short Message Service), specified in [19].
 +-----------------------------------------------------+
 | Alerting Extension Module                           |
 +-----------+-----------------------------------------+
 | Alerting  | Internet e-mail [SMTP,RFC822] (sender), |
 |           | SMS                                     |
 +-----------+-----------------------------------------+

5.5.8. Customer Discovery Extension Module

 The Customer Discovery Extension Module allows Z39.50 clients to use
 the service of the GAIA Broker.
 This Extension Module requires the Broker to support the server part
 of the Z39.50 protocol, as defined in [5].  The following subset of
 the protocol is required:
  1. Init, Search, and Present services
  2. GRS-1 record syntax
 Z39.50 protocol PDUs should be carried using TCP/IP network
 protocols.
 +----------------------------------------------------+
 | Discovery Extension Module                         |
 +------------------------+---------------------------+
 | Searching,             | Z39.50 (server)           |
 | Locating               |                           |
 +------------------------+---------------------------+

5.6. Interface Modules

 For the purpose of conformance, all interfaces between FUMs and FUs,
 specified by the GAIA Standard, are grouped into GAIA Interface
 Modules.  These modules are recommended to be supported by a GAIA
 Broker, but they are not mandatory.  A Broker can choose a subset of

Blinov, et al. [Page 25] RFC 2552 GAIA April 1999

 Interface Modules that are more important in its area of operation,
 and implement interfaces defined in these modules.
 A full specification of the Functional Unit interfaces is presented
 in the GAIA Standard [1].
 The following table defines Interface Modules and specifies which
 interfaces have to be supported in each of them.
 +--------------------+------------------------------------+
 | Interface Module   | Interfaces that are required to be |
 |                    | supported in this module           |
 +--------------------+------------------------------------+
 | Search             | Search FU interface                |
 | Locate             | Locate FU interface                |
 | Order              | Order FU interface                 |
 | Discrete Delivery  | Discrete Delivery FU interface     |
 | Stream Delivery    | Stream Delivery FU interface       |
 | Customer           | Customer FU interface              |
 | Alerting           | Alerting FU interface              |
 | Directory Services | Directory Services FU interface    |
 | Authentication     | Authentication FU interface        |
 | Payment            | Payment FU interface               |
 +--------------------+------------------------------------+

6. Acknowledgement

 We wish to express our gratitude to all members of the GAIA
 Consortium for a very lively discussion and their valuable direct and
 indirect input in the design process of the GAIA Standard.

7. Security Considerations

 Security issues related to the electronic brokerage are discussed in
 Sections 2.1.4, 2.3 and 5.4.5.

8. References

 [1]  GAIA Consortium, Deliverable 0403, "GAIA Standard (Final)",
      December 1998, see also <http://www.syspace.co.uk/GAIA/>.
 [2]  Object Management Group, "CORBA 2.0 Specification", July 1996,
      See <ftp://ftp.omg.org/pub/docs/formal/97-02-25.pdf>.
 [3]  Fielding, R., Gettys, J., Mogul, J., Frystyk, H. and T.
      Berners-Lee, "Hypertext Transfer Protocol -- HTTP/1.1", RFC
      2068, January 1997.

Blinov, et al. [Page 26] RFC 2552 GAIA April 1999

 [4]  Berners-Lee, T. and D. Connolly, "Hypertext Markup Language -
      2.0", RFC 1866, November 1995.
 [5]  ANSI/NISO Z39.50-1995 or ISO 23950 "Information Retrieval:
      Application Service Definition and Protocol Specification".
 [6]  ISO 10161:1997 "Information and documentation -- Open Systems
      Interconnection -- Interlibrary Loan Application Protocol
      Specification".
 [7]  Postel, J. and J. Reynolds, "File Transfer Protocol", STD 9, RFC
      959, October 1985.
 [8]  Postel, J., "Simple Mail Transfer Protocol", STD 10, RFC 821,
      August 1982.
 [9]  Crocker, D., "Standard for the format of ARPA Internet text
      messages", STD 11, RFC 822, August 1982.
 [10] Freed, N., and N. Borenstein, "Multipurpose Internet Mail
      Extensions (MIME) Part One: Format of Internet Message Bodies",
      RFC 2045, November 1996.
      Freed, N., and N. Borenstein, "Multipurpose Internet Mail
      Extensions (MIME) Part Two: Media Types", RFC 2046, November
      1996.
      Moore, K., "MIME (Multipurpose Internet Mail Extensions) Part
      Three: Message Header Extensions for Non-ASCII Text", RFC 2047,
      November 1996.
      Freed, N., Klensin, J., and J. Postel, "Multipurpose Internet
      Mail Extensions (MIME) Part Four: Registration Procedures", RFC
      2048, November 1996.
      Freed, N., and N. Borenstein, "Multipurpose Internet Mail
      Extensions (MIME) Part Five: Conformance Criteria and Examples",
      RFC 2049, November 1996.
 [11] ISO/IEC IS 13818 "Information technology -- Coding of moving
      pictures and associated audio information"
      Part 1: Systems
      Part 2: Video
      Part 3: Audio
      Part 4: Conformance testing
      Part 5: Software simulation

Blinov, et al. [Page 27] RFC 2552 GAIA April 1999

 [12] Schulzrinne, H., Casner, S., Frederick, R., and V. Jacobson,
      "RTP: A Transport Protocol for Real-Time Applications", RFC
      1889, January 1996.
 [13] Hoffman, D., Fernando, G., Goyal, V. and M. Civanlar, "RTP
      Payload Format for MPEG1/MPEG2 Video", RFC 2250, January 1998.
 [14] Freier, A., Karlton, P. and P. Kocher, "The SSL Protocol -
      Version 3.0", Work in Progress, Transport Layer Security Working
      Group, November 1996, See
      <http://home.netscape.com/eng/ssl3/index.html>.
 [15] PKCS #7: Cryptographic Message Syntax Standard.  Version 1.5,
      November 1993.
 [16] Linn, J., "Generic Security Service Application Program
      Interface", RFC 1508, Geer Zolot Associate, September 1993.
 [17] Public-Key Infrastructure (X.509) IETF Working Group,
      <http://www.ietf.org/html.charters/pkix-charter.html>, July 98.
 [18] "SET Secure Electronic Transaction Specification", Version 1.0,
      MasterCard and Visa, May 97.
 [19] Digital Cellular Telecommunications System (Phase 2+): Technical
      Realization of the Short Message Service (SMS) Point-to-Point
      (PP) (GSM 3.40).  Version 5.2.0.  European Telecommunications
      Standards Institute.  May 1996.

Blinov, et al. [Page 28] RFC 2552 GAIA April 1999

9. Authors' Addresses

 Mikhail Blinov
 Computer Science Department
 University College Dublin
 Belfield, Dublin 4, Ireland
 Phone: +353 1-706-2488
 Fax:   +353 1-269-7262
 EMail: mch@net-cs.ucd.ie
 Mikhail Bessonov
 Computer Science Department
 University College Dublin
 Belfield, Dublin 4, Ireland
 Phone: +353 1-706-2488
 Fax:   +353 1-269-7262
 EMail: mikeb@net-cs.ucd.ie
 Ciaran Clissmann
 Computer Science Department
 University College Dublin
 Belfield, Dublin 4, Ireland
 Phone: +353 1-706-2488
 Fax:   +353 1-269-7262
 EMail: ciaranc@net-cs.ucd.ie

Blinov, et al. [Page 29] RFC 2552 GAIA April 1999

10. Full Copyright Statement

 Copyright (C) The Internet Society (1999).  All Rights Reserved.
 This document and translations of it may be copied and furnished to
 others, and derivative works that comment on or otherwise explain it
 or assist in its implementation may be prepared, copied, published
 and distributed, in whole or in part, without restriction of any
 kind, provided that the above copyright notice and this paragraph are
 included on all such copies and derivative works.  However, this
 document itself may not be modified in any way, such as by removing
 the copyright notice or references to the Internet Society or other
 Internet organizations, except as needed for the purpose of
 developing Internet standards in which case the procedures for
 copyrights defined in the Internet Standards process must be
 followed, or as required to translate it into languages other than
 English.
 The limited permissions granted above are perpetual and will not be
 revoked by the Internet Society or its successors or assigns.
 This document and the information contained herein is provided on an
 "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
 TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
 BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
 HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
 MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

Blinov, et al. [Page 30]

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