WDIFF

draft-sun-handle-system-10.txt --> draft-sun-handle-system-11.txt

Internet Draft Sam X. Sun
Document: draft-sun-handle-system-10.txt draft-sun-handle-system-11.txt CNRI
Expires: March November 2003 Larry Lannom
CNRI
September 2002
June 2003

Handle System Overview

Status of this Memo

This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026.

Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet-
Drafts.

Internet-Drafts are draft documents valid for a maximum of six
months and may be updated, replaced, or obsoleted by other
documents at any time. It is inappropriate to use Internet-Drafts
as reference material or to cite them other than as "work in
progress."

The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html.

Abstract

This document provides an overview of the Handle System in terms of
its namespace and service architecture, as well as its relationship
to other Internet services such as DNS, LDAP/X.500, and URN. The
Handle System is a general-purpose global name service that allows
secured name resolution and administration over the public
Internet. The Handle System manages handles, which are unique names
for digital objects and other Internet resources.

Table of Contents

1. Introduction..................................................2
2. Handle Namespace..............................................5 Motivations...................................................5
3. Handle System Architecture....................................6 Namespace..............................................6
4. Handle System Architecture....................................7
5. Handle System Service and its Security........................9
5. Security.......................10
6. The Handle System and other Internet Services................10
5.1 Services................11
6.1 Domain Name Service (DNS)...................................11
5.2 (DNS)...................................12
6.2 Directory Services (X.500/LDAP).............................11
5.3 Uniform Resource Names (URN)................................12 (X.500/LDAP).............................12

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6. June 2003

6.3 Uniform Resource Identifier (URI)/Uniform Resource Name(URN) 13
7. Security Considerations......................................13
6.1 Considerations......................................14
7.1 General Security Practice...................................13
6.2 Practice...................................15
7.2 Privacy Protection..........................................14
6.3 Protection..........................................15
7.3 Caching and Proxy...........................................14
6.4 Mirroring...................................................15
6.5 Proxy...........................................16
7.4 Mirroring...................................................16
7.5 Denial of Service (DoS).....................................15
7. (DoS).....................................16
8. History of the Handle System.................................15
8. Acknowledgement..............................................15 System.................................17
9. Acknowledgement..............................................17
References and Bibliography.....................................16 Bibliography.....................................17
Author's Addresses..............................................17 Addresses..............................................19

1. Introduction

This document provides an overview of the Handle System, a
distributed information system designed to provide an efficient,
extensible, and secured global name service for use on networks
such as the Internet. The Handle System includes an open protocol,
a namespace, and a reference implementation of the protocol. The
protocol enables a distributed computer system to store names, or
handles, of digital resources and resolve those handles into the
information necessary to locate, access, and otherwise make use of
the resources. These associated values can be changed as needed to
reflect the current state of the identified resource without
changing the handle. This allows the name of the item to persist
over changes of location and other current state information. Each
handle may have its own administrator(s) and administration can be
done in a distributed environment. The Handle System supports
secured handle resolution. Security service such as data
confidentiality, service data integrity, and non-repudiation are provided
upon client's request.

The Handle System provides a confederated name service that allows
any existing local namespace to join the global handle namespace by
obtaining a unique handle system naming authority. Local names and
their value-binding(s) remain intact after joining the Handle
System. Any handle request to the local namespace may be processed
by a service interface speaking the handle system protocol.
Combined with the unique naming authority, any local name is
guaranteed unique under the global handle namespace.

There are several services that are in use today to provide name
service for Internet resources. Among these the Domain Name System
(DNS) [2,3] is the most widely used. DNS is designed "to provide a
mechanism for naming resources in such a way that the names are
mappable into IP addresses and are usable in different hosts,
networks, protocol families, internets, and administrative
organizations" [3]. The growth of the Internet has raised demands
for various extensions to DNS. There are also attempts to use DNS
as a general-purpose resource naming system. However, the

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as a general-purpose resource naming system. However, the
importance of DNS in basic network routing has led to great caution
in implementing any DNS extension or overloading the DNS for
general-purpose resource naming. An additional factor which argues
against using DNS as a general-purpose naming service is the DNS
administrative model. DNS names are typically managed by the
network administrator(s) at the DNS zone level. There is no
provision for per-name administrative structure and no facilities
for anyone other than the network administrator to create or manage
DNS names. This is appropriate for domain name administration but
less so for general-purpose resource naming.

The Handle System has been designed from the start to serve as a
general-purpose naming service. It is designed to accommodate very
large numbers of entities and to allow distributed administration
over the public Internet. The handle system data model allows
access control to be defined at the level of each handle data. Each
handle can further define its own set of administrators that are
independent from the network or host administrator.

Traditional URLs (Uniform Resource Locators) [4] allow certain
Internet resources to be named as a combination of a DNS name and
local name. The local name may be a local file path, or a reference
to some local service (e.g. a cgi-bin script). This combination of
DNS name and local name provides a flexible administrative model
for naming and managing individual Internet resources. However, the
URL practice also has some key limitations. Most URL schemes (e.g.,
http) are defined for resolution only. Any URL administration has
to be done either at the local host, or via some other network
service such as NFS. Using a URL as a name typically ties the
Internet resource to its current network location. For example, a
URL will be tied to its local file path when the file path is part
of the URL. When the resource moves from one location to another
for whatever reason, the URL breaks.

The Handle System is designed to overcome these limitations and to
add significant functionality. Specifically, the Handle System is
designed with the following objectives:

. Uniqueness: Every handle is globally unique within the Handle
System.

. Persistence: Handles may be used as persistent identifiers for
Internet resources. A handle is does not have to be derived in
any way from the entity that it names, but is assigned to it independently. names. While an existing name,
or even a mnemonic, may be included in a handle for
convenience, the only operational connection between a handle
and the entity it names is maintained within the Handle
System. This of course does not guarantee persistence, which

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is a function of administrative care. But it does allow the
same name to persist over changes of

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other state conditions. For example, when a named resource
moves from one location to another, the handle may be kept
valid by updating its value in the Handle System to reflect
the new location.

. Multiple Instances: A single handle can refer to multiple
instances of a resource, at different and possibly changing
locations in a network. Applications can take advantage of
this to increase performance and reliability. For example, a
network service may define multiple entry points for its
service with a single handle so as to distribute the service
load.

. Extensible Namespace: Existing local namespaces may join the
handle namespace by acquiring a unique handle naming
authority. This allows local namespaces to be introduced into
a global context while avoiding conflict with existing
namespaces. Use of naming authorities also allows delegation
of service, both resolution and administration, to a local
handle service.

. International Support: The handle namespace is based on
Unicode 3.0 [1], [17], which includes most of the characters
currently used around the world. This allows handles to be
used in any native environment. The handle protocol mandates
UTF-8 [5] as the encoding used for handles.

. Distributed Service Model: The Handle System defines a
hierarchical service model such that any local handle
namespace may be serviced either by a corresponding local
handle service or by the global service or by both. The global
service, known as the Global Handle Registry, can be used to
dispatch any handle service request to the responsible local
handle service. The distributed service model allows
replication of any given service into multiple service sites
and each service site may further distribute its service into
a cluster of individual servers. (Note that local here refers
only to namespace and administrative concerns. A local handle
service could in fact have many service sites distributed
across the Internet.)

. Secured Name Service: The handle system allows secured name
resolution and administration over the public Internet. The
handle system protocol defines standard mechanisms for both
client and server authentication, as well as service
authorization. It also provides security options to assure
service
data integrity and data confidentiality.

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. Distributed Administration Service: Each handle may define its
own administrator(s) or administrator group(s). Ownership of
each handle is defined in terms of its administrator or
administrator groups. This, combined with the handle system
authentication protocol, allows any handle to be managed
securely over the public network by its administrator at any
network location.

. Efficient Resolution Service: The handle protocol is designed
to allow highly efficient name resolution performance. To
avoid resolution being affected by computationally costly
administration service, separate service interfaces (i.e.,
server processes and their associated communication ports) for
handle name resolution and administration may be defined by
any handle service.

This document provides an overview of the handle namespace and
service architecture. It also compares the Handle System with other
existing Internet services, protocols, and specifications (e.g.,
DNS [2, 3], URLs [4], X.500/LDAP [6,7,8], and URN [9,10]). Details
of the handle system data and service model, as well as its
communication protocol, are specified in separate documents. They
can be found under the handle system website at
http://www.handle.net.

2. Handle Namespace

Every handle consists of two parts: its naming authority, otherwise
known as its prefix, and Motivations

Since there are a unique local name under the naming
authority, otherwise known as its suffix:

The naming authority and local number of name are separated by related projects in the ASCII
character "/". The collection of local names under a naming
authority defines Internet
community, it would be well worth defining exactly where we believe
the local handle namespace for Handle System fits. Unfortunately, that is particularly hard
because the other main approaches to naming
authority. Any local name must be unique under its local namespace.
The uniqueness take either an approach
of a naming authority and a local as an abstract services (e.g. URI/URN) or name under that
authority ensures that any handle is globally unique within the
context resolution
absent self-contained framework for reliable yet distributed
administration of the underlying databases (e.g. DNS). This makes
categorizing the Handle System.

For example, "10.1045/january99-bearman" is System difficult.

The Handle System crosses boundaries, thus if you look at it as a handle for an article
published in D-Lib magazine [12]. Its naming authority is "10.1045"
and its local
name resolution system one might compare it to DNS. If one were to
use it to implement a URI/URN namespace one might consider it to
used under any URI/URN scheme; and if one were to view it for
distributed information update and administration one might
consider it a simplified-version of distributed file system.

It is "january99-bearman". The probably best to view the handle namespace can
be considered system as superset of many local namespaces, a service with each local
namespace having a unique naming authority under the Handle System.
The naming authority identifies the administrative unit of
creation, although not necessarily continuing administration, of
the associated handles. Each naming authority
specific protocol for securely creating, updating, maintaining, and
accessing a distributed database. It is guaranteed designed to be an enabling
service for secured information and resource sharing over the
public Internet. Applications of the Handle System may include

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globally June 2003

meta-data service for digital publications, identity management
service for virtual identities, and any applications that require
resolution and/or administration of global unique within identifiers.

In the spirit of exploration, the Handle System. Any existing local
namespace can join System has been designed
to have high performance for name resolution and to push the global handle namespace by obtaining
boundaries of distributed access control and administration.
Unlike most conventional systems (even distributed systems) that
are designed to have a relatively small number of broadly empowered
administrators, the Handle System allows extremely fine granularity
of administrative control. It has a unique naming authority so self-contained
administration framework that any local name under de-couples the namespace
can be globally referenced as a combination ownership of each
handle from the naming authority system administrators and the local name allows access control be
defined upon each handle value.

It should be noted, that as shown above.

Naming authorities under with all real systems, the Handle
System are defined in is a
hierarchical fashion resembling compromise between a tree structure. Each node and
leaf number of technical and practical
concerns. There are also different opinions within IETF on where
the tree Handle System fits in relation to other existing Internet name
services. It is given with the goal of exposing a label that corresponds broader community to a naming
authority segment. The parent node presents
the parent naming
authority concepts, approach, specific decisions, tradeoffs and results
that we are writing this RFC.

3. Handle Namespace

Every handle consists of two parts: its child nodes. Unlike DNS, handle naming authorities
are constructed left to right, concatenating the labels from the
root of the tree to the node that represents authority, otherwise
known as its prefix, and a unique local name under the naming authority.
Each label is
authority, otherwise known as its suffix:

The naming authority and local name are separated by the octet used for ASCII
character "."
(0x2E). For example, "/". The collection of local names under a naming
authority for the National Digital
Library Program ("ndlp") at defines the Library of Congress ("loc") is
defined as "loc.ndlp".

Each naming authority may have many child local handle namespace for that naming authorities
registered underneath.
authority. Any child naming authority can only local name must be
registered by its parent after unique under its parent local namespace.
The uniqueness of a naming authority and a local name under that
authority ensures that any handle is
registered. However, there is no intrinsic administrative
relationship between globally unique within the namespaces represented by
context of the parent and
child Handle System.

For example, "10.1045/january99-bearman" is a handle for an article
published in D-Lib magazine [12]. Its naming authorities. The parent namespace authority is "10.1045"
and its child
namespaces may be served by different local name is "january99-bearman". The handle services, and namespace can
be considered as superset of many local namespaces, with each local
namespace having a unique naming authority under the Handle System.
The naming authority identifies the administrative unit of
creation, although not necessarily continuing administration, of
the associated handles. Each naming authority is guaranteed to be
globally unique within the Handle System. Any existing local
namespace can join the global handle namespace by obtaining a

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unique naming authority so that any local name under the namespace
can be globally referenced as a combination of the naming authority
and the local name as shown above.

Naming authorities under the Handle System are defined in a
hierarchical fashion resembling a tree structure. Each node and
leaf of the tree is given a label that corresponds to a naming
authority segment. The parent node presents the parent naming
authority of its child nodes. Unlike DNS, handle naming authorities
are constructed left to right, concatenating the labels from the
root of the tree to the node that represents the naming authority.
Each label is separated by the octet used for ASCII character "."
(0x2E). For example, a naming authority for the National Digital
Library Program ("ndlp") at the Library of Congress ("loc") is
defined as "loc.ndlp".

Each naming authority may have many child naming authorities
registered underneath. Any child naming authority can only be
registered by its parent after its parent naming authority is
registered. However, there is no intrinsic administrative
relationship between the namespaces represented by the parent and
child naming authorities. The parent namespace and its child
namespaces may be served by different handle services, and they may
or may not share any administration privileges between each other.

Handles may consist of any printable characters from the Universal
Character Set (UCS-2) of ISO/IEC 10646, which is the exact
character set defined by Unicode v2.0 [1]. [17]. The UCS-2 character set
encompasses most characters used in every major language written
today. To allow compatibility with most of the existing systems and
prevent ambiguity among different encoding, the handle system
protocol mandates UTF-8 to be the only encoding used for handles.
The UTF-8 encoding preserves any ASCII encoded names so as to allow
maximum compatibility to existing systems without causing naming
conflict. Some encoding issues over the global namespace and the
choice of UTF-8 encoding are discussed in [13].

By default, handles are case sensitive. However, a handle service
may define its namespace so that ASCII characters within any handle
under the namespace are case insensitive.

4. Handle System Architecture

The Handle System defines a hierarchical service model. The top
level consists of a single global service, known as the Global
Handle Registry (GHR). The lower level consists of all other handle
services, generically known as Local Handle Services (LHS).

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The Global Handle Registry can be used to manage any handle
namespace. It is unique from any other handle services only in that
it provides the service used to manage naming authorities, all of
which are managed as handles. The naming authority handle provides
information that clients can use to access and utilize the local
handle service for handles under the naming authority.

Local Handle Services are intended to be hosted by organizations
with administrative responsibility for handles under certain naming
authority. A Local Handle Service may be responsible for any number
of local handle namespaces, each of which identified by a unique
naming authority. The Local Handle Service and its responsible set
of local handle namespaces must be registered under the Global
Handle Registry.

One important aspect of the Handle System is its distributed
architecture. The Handle System as a whole consists of a number of
individual handle services. Each of these service may consist of
one or more service sites. Each of these service site is a complete
replication of each other, at least for handle resolution.
Additionally, a service site may also consist of one or more handle
servers. Handle requests directed at the service site may be evenly
distributed into these handle servers. The Handle System may
consist of any number of handle services. There are no design
limits on the number of sites which make up each service. Neither
there are any limits on the number of servers that make up each
site. Replication among any service sites does not require that
each site contains the same number of servers. In other words,
while each site will have the same replicated set of handles, each
site may allocate that set of handles across a different number of
servers. This distributed approach is intended to aid scalability
to accommodate any large-scale of operation and to mitigate
problems of single point failure.

Figure 3.1 illustrates a potential handle service that consists of
two service sites: one located at the US East coast and the other
at the US West coast. The East coast service site consists of four
server computers. The West coast service site, with more powerful
computers deployed, decides two servers will suffice. The number of
service sites for any handle service, as well as the number of
servers that are used by any service site, may be added or removed
dynamically depending on the service requirement.

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------------------------- ------------------
| --------- --------- | | ----- ----- |
| | | | | | | | S | | S | |
| | server1 | | server2 | | | | E | | E | |
| | | | | | | | R | | R | |
| --------- --------- | | | V | | V | |
| --------- --------- | | | E | | E | |
| | | | | | | | R | | R | |
| | Server3 | | Server4 | | | | | | | |
| | | | | | | | 1 | | 2 | |
| --------- --------- | | ----- ----- |
------------------------- ------------------

Handle Service Site 1 Handle Service Site 2
(US East Coast) (US West Coast)

Fig. 3.1: Handle service configured with two service sites

Each handle service manages a distinct sub-namespace under the
Handle System. Namespaces under different handle services may not
overlap. The sub-namespace typically consists of handles under a
number of naming authorities. The handle service is called the
"home" service of these naming authorities and is the only one that
provides resolution and administration service for handles under
these naming authorities. Before resolving a handle, a client has
to determine the "home" service of the handle in question. The
"home" service of each handle is the "home" service of its naming
authority and is registered at the Global Handle Registry. Clients
can find the "home" service for each handle by querying the naming
authority handle at the Global Handle Registry.

The Global Handle Registry maintains naming authority handles. Each
naming authority handle maintains the service information that
describes the "home" service of the naming authority. The service
information lists the service sites of the handle service, as well
as the interface to each handle server within each site. To find
the "home" service for any handle, a client can query the Global
Handle Registry for the service information associated to the
corresponding naming authority handle. The service information
provides the necessary information for clients to communicate with
the "home" service.

Figure 3.2 shows an example of a typical handle resolution process.
In this case, the "home" service is a Local Handle Service. The
client is trying to resolve the handle "cnri.dlib/july95-arms" and
has to find its "home" service from the Global Handle Registry. The
"home" service can be found by sending a query to the Global Handle
Registry for the naming authority handle for "cnri.lib". The Global
Handle Registry returns the service information of the Local Handle

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Service that is responsible for handles under the naming authority
"cnri.dlib". The service information allows the client to
communicate with the Local Handle Service to resolve the handle
"cnri.dlib/july95-arms".

------------------------
| | 4. Result of client request
| Client with global | <-------------------------------.
| service information | |
| | ----------------------------. |
------------------------ 3. Request to responsible | |
| ^ Local Handle Service | |
1. Client | | | |
query for | | | |
naming | | 2. Service information | |
authority | | for "cnri.dlib" V |
"cnri.dlib" | | ----------------------
| | | |
V | | Local Handle Service |
--------------- | responsible for the |
| | | naming authority |
| Global Handle | | "cnri.dlib" |
| Registry | | |
| | ----------------------
---------------

Fig. 3.2: Handle resolution starting with global

To improve resolution performance, any client may choose to cache
the service information returned from the Global Handle Registry
and use it for subsequent queries. A separate handle caching
server, either stand-alone or as a piece of a general caching
mechanism, may also be used to provide shared caching within a
local community. Given a cached resolution result, subsequent
queries of the same handle may be answered locally without
contacting any handle service. Given cached service information,
clients can send their requests directly to the Local Handle
Service without contacting the Global Handle Registry.

5. Handle System Service and its Security

The Handle System provides handle resolution and administration
service over the public Internet. Each handle can be assigned with
a set of values. Clients use the handle resolution service to
resolve any handle into its set of values. Each value has a data
type and a unique value index. Clients can query for specific
handle values based on data type or value index.

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The handle administration service answers requests from clients to
manage handles. These include adding handles, deleting handles or
updating their values. It also manages naming authorities via
naming authority handles. Each handle can define its own
administrator(s) and each administrator can be granted a certain
set of permissions. The handle system authentication protocol
authenticates the handle administrator before fulfilling any
administrative request.

The Handle System provides security services such as client and
server authentication, data confidentiality and integrity, as well
as service non-repudiation. By default, handle resolution service does not
require any client authentication. However, resolution request for
confidential data assigned to any handle (by its administrator), as
well as any administration request (e.g. adding or deleting handle
values) require authentication of the client for proper
authorization. Via the authorization process, the server may decide
whether the client has the permission to access those confidential
handle values, or has permissions to add or update handles and
handle values. When authentication is required, the handle server
will issue a challenge to the requesting client before carrying out
the client's request. To satisfy the authentication requirement,
the client must send back the correct response that identifies
itself as the administrator. The handle server will respond to the
initial request only after successful authentication of the client.
Handle clients may choose to use either secret key or public key
cryptography for authentication. Authentication under Handle System
can also be carried out via third party authentication services. To
ensure data integrity, clients may request digitally signed
responses from any handle server. They may also set up a secured
communication session with the handle server so that any exchanged
information can be encrypted (for data
confidentiality) using confidentiality) using the
session key. The handle server can also provide confidentiality
service by encrypting the handle data before sending them to the session key.
client.

The Handle System provides service options for secured information
exchange between client and server. This does not guarantee the
truthfulness of handle values. Incorrect values assigned to any
handle by its administrator may very well mislead clients. On the
other hand, a handle value may contain references to other handle
values to provide additional credentials. For example, a handle
value R (e.g., a claim) may contain a reference to some other
handle value that contains the digital signature (from a creditable
source) upon the value R. Clients who trust the signature could
then trust the handle value R.

6. The Handle System and other Internet Services

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There are a number of existing and proposed Internet identifier
services or specifications that by design or intent cover some of
the functionalities proposed for the Handle System. This section
briefly reviews them in relationship to the Handle System.

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5.1

6.1 Domain Name Service (DNS)

The Domain Name Service, or DNS, was originally designed and is
heavily used for mapping domain names into IP Addresses for network
routing purposes. RFC1034 [2] and RFC1035 [3] provide detailed
descriptions of its design and implementation. The growth of the
Internet has increased demands for various extensions to DNS, even
its possible use as a general purpose resource naming system.
However, any such use has the potential to slow down the network
address translation and/or affect its effectiveness in network
routing. DNS implementations typically do not scale well when large
amount of data is associated with any particular DNS name. It is
generally considered inadequate to use DNS for naming any kind of
resources over the Internet.

An additional factor that argues against using DNS as a general-
purpose naming service is the DNS administrative model. DNS names
are typically managed by the network administrator(s) at the DNS
zone level. There is with no provision for a per-name
administrative structure. No facilities are provided for anyone
other than network administrators to create or manage DNS names.
This is appropriate for domain name administration but less so for
general-purpose name administration.

The Handle System differs from DNS in its distributed
administration and service model, as well as its security features.
The handle system protocol comprise security options to assure
confidentiality and integrity during data transmission. Each handle
under the Handle System may define its own administrator that is
independent from the server administrator. The handle system
protocol allows any handle administrator to manage its handles
securely over the public network. Additionally, the Handle System
service model allows any of its service sites to dynamically
configure its service distribution among a cluster of servers to
accommodate increased service requests. This also allows less
powerful computers to be used together to support any huge number
of handles.

5.2

6.2 Directory Services (X.500/LDAP)

X.500 [6] is the OSI Directory Standard defined by ISO and the ITU.
It is designed "to provide a white pages service that would return
either the telephone numbers or X.400 O/R addresses of people", and
is "concerned mainly with providing the name server service for

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Open Systems Interconnection (OSI) applications" [7]. X.500 defines
a hierarchical data and information model with a set of protocols
to allow global name lookup and search. The protocol, however, has
proved difficult to implement and there has been difficulty in

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getting "client access integrated into existing products" [14].
LDAP (Lightweight Directory Access Protocol) [8] has overcome many
of these difficulties by making the protocol simpler, and easier to
implement. Some concern remains, however, that as LDAP is emerging
from a local directory access protocol (LDAP v2) into a distributed
service protocol (LDAP v3), it faces many issues not addressed in
its original design, resulting in new complications.

The fundamental difference between a name resolution service such
as the Handle System and a directory service such as LDAP is search
capability. The added functionality of being able to search a
directory service necessarily carries with it added complexity,
thus affects its efficiency. A pure name service, such as the
Handle System, can be designed solely around efficient resolution
of known items without addressing functions and data structures
required for discovery of unknown items based on incomplete
criteria.

Directory services such as LDAP or WHOIS++ [15,16] may be used in
tandem with the Handle System to provide reverse lookup service.
Existing corporate directory services, for example, could provide
interfaces to both services. The handle system interface would
provide a highly efficient name resolution service. The directory
service interface would provide extended search capability. Handles
could also be used in LDAP service referral. For example, a LDAP
service may be referenced as a handle. Doing so will make the
reference persistent overtime, independent from location change.

5.3

6.3 Uniform Resource Names Identifier (URI)/Uniform Resource Name(URN)

Uniform Resource Identifier (URI) [23] defines a uniform yet
extensible naming mechanism for identifying Internet resources in
web applications. Uniform Resource Name (URN)

The IETF URN Working Group [11] has defined [11], a subset of
URI, defines a syntax, possible
resolution mechanisms, and namespace registration procedure mechanism for a
resource identifier intended to cover a large array of existing and
potential namespaces. Namespaces are to be registered and assigned
unique Namespace Ids (NIDs). Any resolution services associated
with these persistent
namespaces require further registration with a
Resolution Discovery System (RDS) which clients could use to begin,
or discover, the appropriate resolution mechanisms.

The objectives and some under URI. URI/URN represents most of the approaches Internet name
services used in web applications. This section discusses the
relationship of the URN and Handle System efforts have enough in common that some observers might
think that they are in contention. This is not the case. The URN
effort is explicitly designed to accommodate multiple identifier
namespaces URI/URN and resolution systems. how applications
may utilize the Handle System within the URI/URN context.

The Handle System is one such
case. It has provides a very specific data and general-purpose name service model, along with a
protocol that supports both handle resolution and administration.
URNs and for the Handle System may interact in variety of ways. The
most obvious of which is that
Internet. Like DNS or X.500 directory service, the Handle System could handle system
defines its namespace outside of any URI/URN namespace. Handles can
be registered transcribed and resolved directly, without any URI/URN scheme as
a URN namespace. In other words, handles under prefix. For example, a library application may resolve the Handle System handle

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could June 2003

"cnri.dlib/july95-arms" directly into its set of handle values. No
URI/URN scheme will be referenced needed in this case.

The Handle System may be used for applications that require
persistent name service. The Handle System provides necessary
mechanism to allow persistent names registered as a type handles. Specific
naming authorities may be defined to host those handles that
designed to be persistent. However, the persistence of URN. handles
depends more on the administrative policies than the technology
itself. They are beyond the handle system service as described in
this set of documents.

On the other hand, it would the Handle System can also be possible used for
applications where namespace persistency is not required. These
applications may have their specific naming authorities where
handles under these naming authorities are not necessarily
persistent. Such handles may have a short life-time and they may
also be used to use identify different objects at different times.

Different web applications may be developed using the Handle System
as a type the underlying name service. Each of RDS these applications may
define its own URI/URN namespace for
other its application need. For
example, application FOO may have a URI namespace "foo:" registered
to identify any FOO services on the web. In the mean time,
application BAR may have a URN namespaces. namespace "URN:BAR" registered to
identify any BAR object that needs a persistent name. Both FOO and
BAR applications may use handles (under their perspective naming
authority) in naming and resolving their services and/or objects.
This is similar in DNS, where there are different URI schemes (e.g.
"telnet", "ftp", "mailto", etc.) defined for different
applications, all using the DNS service.

The success IETF and IRTF have discussed the Handle System in the realm of either system however, is not
dependent upon
URI-related work. There are different opinions on whether the
Handle System will fit into a specific URI or URN namespace. There
are also concerns on where the Handle System fits regarding to
other existing name services on the success Internet. Such discussions are
out of the other.

6. scope of this document and will be discussed in a
separate document.

7. Security Considerations

This section is meant to inform people of security limitations of
the Handle System, as well as precautions that should be taken by
application developers, service providers, and handle system
clients. Specific security considerations regarding the handle
system protocol [21] or its data and service model [22] are
addressed in separate documents.

6.1

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7.1 General Security Practice

The security of the Handle System depends on both client and server
host security at every step in the transaction. It assumes the
client host has not been tampered with and that client software
will reliably convey the received data to the client. The client of
any handle service must also assume that any handle servers
involved have not been compromised. To trust the Global Handle
Registry is to believe that the Global Handle Registry will
rightfully direct the client request to the responsible Local
Handle Service. To trust a Local Handle Service is to believe that
the Local Handle Service will correctly return the data that was
assigned to the handle by its administrator. A Local Handle Service
typically supports a set of naming authorities. Thus, trusting a
Local Handle Service would imply trusting those naming authorities.

The handle system service integrity of the Handle System depends heavily on the integrity
of the global service information. Invalid global service
information may mislead clients into inappropriate Local Handle
Services. It may also allow attackers to forge server signatures.
The Global Handle Registry must take extreme caution in protecting
the global service information and the public key pair used to sign
the global service information. Client applications should only
accept the global service information from the Global Handle
Registry. They should check its integrity upon each update.

For efficiency reasons, handle servers will not generate or return
digital signature for every service response unless specifically
requested by clients. To assure data integrity, clients must
explicitly ask the server to return the digital signature. To
protect sensitive data from exposure, clients may establish a
communication session with the server and ask the server to encrypt
any data using the session key.

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6.2

7.2 Privacy Protection

By default, most handle data stored in the Handle System is
publicly accessible unless otherwise specified by the handle
administrator. Handle administrators must pay attention when adding
handle values that contain private information. They may choose to
mark these handle values readable only by the handle
administrator(s), or to store these handle values encrypted, so
that these values can only be readable within a controlled set of
audience.

Log files generated by the handle server are another vulnerable
point where client privacy may be under attack. Operators of handle
servers must protect such information carefully.

6.3

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7.3 Caching and Proxy

Besides performance gains and other value-added services, both the
proxy and caching server present themselves as men-in-the-middle,
and as such are vulnerable to man-in-the-middle attacks. It is
important to know that proxy and caching servers are not part of
any handle service. They are clients of the Handle System. Service
responses from proxy and caching servers cannot be authenticated
via handle system protocol. The trust between the client and its
proxy and caching
immediate proxy/caching server has to be setup independently. independently,
regardless of the number of proxy/caching servers that are in the
middle of the communication path.

By using the proxy and caching server, clients assume that the
server will submit their request and relay any response from the
Handle System, without mishandling any of the contents. They also
assume that the server will protect any sensitive information on
their behalf.

Proxy and caching server operators should protect the systems on
which such servers are running as they would protect any system
that contains or transports sensitive information. In particular,
log information gathered at proxies often contain highly sensitive
personal information, and/or information about organizations. Such
information should be carefully guarded, and appropriate guidelines
for their use developed and followed.

Caching servers provide additional potential vulnerabilities
because the contents of the cache represents an attractive target
for malicious exploitation. Potential attacks on the cache can
reveal private data for a handle user, or information still kept
after a user believes that they have been removed from the network.
Therefore, cache contents should be protected as sensitive
information.

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6.4

7.4 Mirroring

Handle system clients should be aware of possible delays in content
replication among mirroring sites. They should consider sending
their request to the primary service site for any time-sensitive
data. Selection of mirroring sites by service administrator must be
done carefully. Each mirroring site must follow the same security
procedures in order to ensure the service data integrity. Software tools
may be applied to ensure data consistency among mirroring sites.

6.5

7.5 Denial of Service (DoS)

As with any public service, the Handle System is subject to denial
of service attack. No general solutions are available to protect

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against such attack in today's technology. Server implementations
may be developed to be aware of such attack and notify its
administrator when it happens. Stateless cookies [19, 20] are one
means to mitigate some of the effects of DoS attacks on hosts that
perform authentication, integrity, and encryption services. Server
implementations, moreover, need to be upgradeable to take advantage
of new security technologies including anti-DoS technologies as
these become available.

8. History of the Handle System

The Handle System was originally conceived and described in a paper
by Robert Kahn and Robert Wilensky [1] in 1995. It was then
developed at CNRI as part of the Computer Science Technical Reports
(CSTR) project, funded by the Defense Advanced Projects Agency
(DARPA) under Grant Number MDA-972-92-J-1029. One aspect of this
early digital library project, which was also a major factor in the
evolution of the Networked Computer Science Technical Reference
Library (NCSTRL) [18] and related activities, was to develop a
framework for the underlying infrastructure of digital libraries. It is described in
a paper by Robert Kahn and Robert Wilensky [17].
The first implementation was created at CNRI in the fall of 1994 in
an effort led by David Ely.

Early adopters of the Handle System include the Library of
Congress, the Defense Technical Information Center (DTIC), and the
International DOI Foundation (IDF). Feedback from these
organizations as well as NCSTRL, other digital library projects,
and related IETF efforts as mentioned above have all contributed to
the evolution of the Handle System. Current status and available
software, both client and server, can be found at
http://www.handle.net.

9. Acknowledgement

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This work is derived from the earlier versions of the handle system
implementation. Design ideas are based on those discussed within
the handle system development team, including David Ely, Charles
Orth, Allison Yu, Sean Reilly, Jane Euler, Catherine Rey, Stephanie
Nguyen, Jason Petrone, and Helen She. She, and Brian Boesch. Their
contributions to this work are gratefully acknowledged.

The authors also thanks and acknowledges Mark Baugher
(mbaugher@cisco.com) for his extensive review and comments of these
drafts, as well as recommendations received from other members of
the IRTF IDRM research group (http://www.idrm.org).

References and Bibliography

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[1] The Unicode Consortium, "The Unicode Standard, Version v3.0",
Addison-Wesley Pub Co; ISBN: 0201616335 R. Kahn, & R. Wilensky, "A Framework for Distributed Digital
Object Services", D-Lib Magazine, 1995

[2] P. Mockapetris, "DOMAIN NAMES - CONCEPTS AND FACILITIES",
RFC1034, November 1987

[3] P. Mockapetris, "DOMAIN NAMES - IMPLEMENTATION AND
SPECIFICATION", RFC1035, November 1987

[4] Berners-Lee, T., Masinter, L., McCahill, M., et al., "Uniform
Resource Locators (URL)", RFC1738, December 1994

[5] Yergeau, Francois, "UTF-8, A Transform Format for Unicode and
ISO10646", RFC2044, October 1996

[6] ITU-T Rec. X.500, "The Directory: Overview of Concepts, Models,
and Services", 1993. 1993

[7] D W Chadwick, "Understanding X.500 - The Directory", Chapman &
Hall ISBN: 0-412-43020-7. 0-412-43020-7

[8] Wahl, M., Howes, T., and S. Kille, "Lightweight Directory
Access Protocol (v3)", RFC 2251, December 1997

[9] Sollins, K., and L. Masinter, "Functional Requirements for
Uniform Resource Names", RFC 1737, December 1994

[10] Sollins, K. "Architectural Principles of Uniform Resource Name
Resolution", RFC 2276, January 1998

[11] IETF Uniform Resource Names (URN) Working Group, April, 1998,
http://www.ietf.org/html.charters/urn-charter.html

[12] D-Lib Magazine, http://www.dlib.org

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[13] Sam X. Sun, "Internationalization of the Handle System - A
Persistent Global Name Service", Proceeding of 12th International
Unicode Conference, April, 1998

[14] D Goodman, C Robbins, "Understanding LDAP & X.500", August
1997

[15] Deutsch P., Schoultz R., Faltstrom P., and C. Weider,
"Architecture of the Whois++ service", RFC 1835, August 1995

[16] Weider, C., J. Fullton, and S. Spero, "Architecture of the
Whois++ Index Service", RFC 1913, February 1996

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[17] Kahn, Robert and Wilensky, Robert. "A Framework for
Distributed Digital Object Services", May, 1995 The Unicode Consortium, "The Unicode Standard, Version v3.0",
Addison-Wesley Pub Co; ISBN: 0201616335

[18] The Networked Computer Science Technical Reports Library
(NCSTRL), http://www.ncstrl.org/

[19] P. Karn, W. Simpson, "Photuris: Session-Key Management
Protocol", March, 1999

[20] D. Harkins, D Carrel, "The Internet Key Exchange (IKE)",
November, 1998

[21] S. Sun, S. Reilly, L. Lannom, "Handle System Namespace and
Service Definition", IETF draft, http://www.ietf.org/internet-
drafts/draft-sun-handle-system-def-05.txt, work in progress. progress

[22] S. Sun, S. Reilly, L. Lannom, J. Petrone, "Handle System
Protocol Specification", IETF draft, http://www.ietf.org/internet-
drafts/draft-sun-handle-system-protocol-02.txt, work in progress. progress

[23] T. Berners-Lee, R. Fielding, L. Masinter, "Uniform Resource
Identifiers (URI): Generic Syntax", RFC 2396, August 1998

Author's Addresses

Sam X. Sun
Corporation for National Research Initiatives (CNRI)
1895 Preston White Dr. Suite 100
Reston, VA 20191
Phone: 703-262-5316
Email: ssun@cnri.reston.va.us

Larry Lannom
Corporation for National Research Initiatives (CNRI)
1895 Preston White Dr. Suite 100
Reston, VA 20191
Phone: 703-620-8990
Email: llannom@cnri.reston.va.us

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