| Rfc | 3651 |
|---|
| Title | Handle System Namespace and Service Definition |
|---|
| Author | S. Sun, S. Reilly,
L. Lannom |
|---|
| Date | November 2003 |
|---|
| Format: | TXT, HTML |
|---|
| Status: | INFORMATIONAL |
|---|
|
Network Working Group S. Sun
Request for Comments: 3651 S. Reilly
Category: Informational L. Lannom
CNRI
November 2003
Handle System Namespace and Service Definition
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 (2003). All Rights Reserved.
IESG Note
Several groups within the IETF and IRTF have discussed the Handle
System and it relationship to existing systems of identifiers. The
IESG wishes to point out that these discussions have not resulted in
IETF consensus on the described Handle System nor on how it might fit
into the IETF architecture for identifiers. Though there has been
discussion of handles as a form of URI, specifically as a URN, these
documents describe an alternate view of how namespaces and
identifiers might work on the Internet and include characterizations
of existing systems which may not match the IETF consensus view.
Abstract
The Handle System is a general-purpose global name service that
allows secured name resolution and administration over the public
Internet. This document provides a detailed description of the
Handle System namespace, and its data, service, and operation models.
The namespace definition specifies the handle syntax and its semantic
structure. The data model defines the data structures used by the
Handle System protocol and any pre-defined data types for carrying
out the handle service. The service model provides definitions of
various Handle System components and explains how they work together
over the network. Finally, the Handle System operation model
describes its service operation in terms of messages transmitted
between client and server, and the client authentication process
based on the Handle System authentication protocol.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Handle System Namespace. . . . . . . . . . . . . . . . . . . . 3
3. Handle System Data Model . . . . . . . . . . . . . . . . . . . 4
3.1. Handle Value Set . . . . . . . . . . . . . . . . . . . . 4
3.2. Pre-defined Handle Data Types. . . . . . . . . . . . . . 9
3.2.1. Handle Administrator: HS_ADMIN . . . . . . . . . 10
3.2.2. Service Site Information: HS_SITE. . . . . . . . 14
3.2.3. Naming Authority Delegation Service:
HS_NA_DELEGATE . . . . . . . . . . . . . . . . . 19
3.2.4. Service Handle: HS_SERV. . . . . . . . . . . . . 20
3.2.5. Alias Handle: HS_ALIAS . . . . . . . . . . . . . 21
3.2.6. Primary Site: HS_PRIMARY . . . . . . . . . . . . 21
3.2.7. Handle Value List: HS_VLIST. . . . . . . . . . . 22
4. Handle System Service Model. . . . . . . . . . . . . . . . . . 22
4.1. Handle System Service Components . . . . . . . . . . . . 23
4.1.1. Global Handle Registry (GHR) . . . . . . . . . . 23
4.1.2. Local Handle Service (LHS) . . . . . . . . . . . 26
4.2. Handle System Middle-Ware Components . . . . . . . . . . 27
4.2.1. Handle System Caching Service. . . . . . . . . . 27
4.2.2. Handle System Proxy Server . . . . . . . . . . . 28
4.3. Handle System Client Components. . . . . . . . . . . . . 28
5. Handle System Operation Model. . . . . . . . . . . . . . . . . 29
5.1. Handle System Service Request and Response . . . . . . . 30
5.2. Handle System Authentication Protocol. . . . . . . . . . 32
6. Security Considerations. . . . . . . . . . . . . . . . . . . . 37
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 38
8. References and Bibliography. . . . . . . . . . . . . . . . . . 38
9. Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 40
10. Full Copyright Statement . . . . . . . . . . . . . . . . . . . 41
1. Introduction
The Handle System manages handles as globally unique names for
Internet resources. It was originally conceived and described in a
paper by Robert Kahn and Robert Wilensky [22] in 1995. The Handle
System provides a general-purpose global name service that allows
handles to be resolved and administrated securely over the public
Internet. The Handle System categorizes its service into two
categories: the handle resolution service and the handle
administration service. Clients use handle resolution service to
resolve handles into their values. The handle administration service
deals with client requests to manage these handles, including adding
and deleting handles, and updating handle values.
The document "Handle System Overview" [1] provides an architectural
overview of the Handle System, and its relationship to other Internet
services such as DNS [2,3] and LDAP[4]. This document provides a
detailed description of the Handle System namespace, its data and
service model, and its operation model. It assumes that readers are
familiar with the basic concepts of the Handle System as described in
the overview document.
The namespace definition specifies the handle syntax and its semantic
structure. The data model defines the data structures used by the
Handle System protocol and any pre-defined data types for carrying
out the handle service. The service model provides definitions of
various Handle System components and explains how they work together
over the network. Finally, the Handle System operation model
describes its service operation in terms of messages transmitted
between client and server, and the client authentication process
based on the Handle System authentication protocol.
2. Handle System Namespace
Handles are character strings that may consist of a wide range of
characters. Every handle in the Handle System consists of two parts:
its naming authority, followed by a unique local name under the
naming authority. The naming authority and the local name are
separated by the ASCII character "/" (octet 0x2F). The following
table provides the handle syntax definition in ABNF [5] notation:
<Handle> = <NamingAuthority> "/" <LocalName>
<NamingAuthority> = *(<NamingAuthority> ".") <NAsegment>
<NAsegment> = 1*(%x00-2D / %x30-3F / %x41-FF )
; any octets that map to UTF-8 encoded
; Unicode 2.0 characters except
; octets '0x2E' and '0x2F' (which
; correspond to the ASCII characters '.',
; and '/').
<LocalName> = *(%x00-FF)
; any octets that map to UTF-8 encoded
; Unicode 2.0 characters
Table 2.1: Handle syntax
As shown in Table 2.1, both <NamingAuthority> and <LocalName> are
UTF-8 [6] encoded character strings. The Handle System protocol
mandates UTF-8 encoding for handles transferred over the wire. The
<LocalName> may consist of any characters from the Unicode 2.0
standard [7]. The <NamingAuthority> may use any characters from the
Unicode 2.0 standard except the ASCII character '/' (0x2F), which is
reserved to separate the <NamingAuthority> from the <LocalName>. A
<NamingAuthority> may consist of multiple non-empty <NAsegment>s,
each of which separated by the ASCII character '.' (octet 0x2E).
Naming authorities 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 (<NAsegment>). The parent
node represents the parent naming authority. 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 (or its <NAsegment>) is separated by the character '.' (octet
0x2E). For example, the naming authority for the Digital Object
Identifier (DOI) project is "10". It is a root-level naming
authority as it has no parent naming authority for itself. It can,
however, have many child naming authorities. For example, "10.1045"
is a child naming authority of "10" for the D-Lib Magazine.
By default, handles are case sensitive. However, a handle service,
global or local, may implement its namespace so that ASCII characters
under the namespace are treated as case insensitive. For example,
the global handle service, formally known as the Global Handle
Registry (GHR), is implemented such that ASCII characters are treated
as case insensitive. Since the GHR manages all handles for naming
authorities, ASCII characters in naming authorities are treated as
case insensitive.
3. Handle System Data Model
The Handle System provides a name-to-value binding service over the
public Internet. Each handle may have a set of values assigned to
it. The Handle System maintains the value set of each handle and
will return it in response to any handle resolution request. The
Handle System data model defines the conceptual data structure for
these values. The data model used by the protocol may not be the
exact physical data model used for storage in any specific
implementation. Rather, it is the data model followed by the Handle
System protocol as specified in the "Handle System Protocol
Specification" [8].
3.1. Handle Value Set
Each handle may have a set of values assigned to it. These handle
values use a common data structure for its data. For example, each
handle value has a unique index number that distinguishes it from
other values in the value set. It also has a specific data type that
defines the syntax and semantics of the data in its data field.
Besides these, each handle value contains a set of administrative
information such as TTL and permissions. Figure 3.1 shows the handle
"10.1045/may99-payette" with a set of three handle values. One of
these values (with index number set to 1) is shown in detail. (Note
that the encoding of the length for each field is not shown in Figure
3.1. Also, the empty <reference> field consists of a 4-byte integer
whose value is zero.)
Handle "10.1045/may99-payette"
|
|
V
-------------------------------------------------------------
| <index>: 3 |
------------------------------------------------------------- |
| <index>: 2 | |
------------------------------------------------------------- | |
| | | |
| <index>: 1 | | |
| <type>: URL | | |
| <data>: http://www.dlib.org/dlib... | | |
| <TTL>: {Relative: 24 hours} | | |
| <permission>: PUBLIC_READ, ADMIN_WRITE | | |
| <timestamp>: 927314334000 | | |
| <reference>: {empty} | |-
| |-
-------------------------------------------------------------
Figure 3.1: Handle "10.1045/may99-payette" and its set of values
In Figure 3.1, it shows a handle value whose its index is set to 1.
The data type for the handle value is URL. The URL data as stated in
the <data> field is "http://www.dlib.org/dlib...". The TTL (time to
live) entry suggests that the value record should be cached no more
than 24 hours before the source of the information to be consulted
again. The <permission> field grants anyone permission to read, but
only the administrator to update the value. The <reference> field is
empty. It may contain a list of references to other handle values as
credentials for this handle value.
Thus a handle value may be thought of as a record that consists of a
group of data fields. Each of these data fields is defined as
follows:
<index>
An unsigned 32-bit integer that uniquely identifies a handle value
from other handle values.
<type>
A UTF8-string that identifies the data type for the value record.
Note that throughout this document, a UTF8-string is defined as a
data structure that consists of a 4-byte unsigned integer followed
by an UTF-8 encoded character string. The integer specifies the
number of octets in the character string.
The <type> field identifies the data type that defines the syntax
and semantics of data in the next <data> field. The data type may
be registered with the Handle System to avoid potential conflicts.
The Handle System has a reserved naming authority "0.TYPE" for
registered data types. For example, "URL" (as shown in Figure
3.1) is a registered data type. It is registered as the handle
"0.TYPE/URL". The handle may have a value that explains the
syntax and semantics of the data type.
Data types under the Handle System may be hierarchical. Each
level of the hierarchy may be named in terms of a UTF8-String with
no '.' (0x2E) characters. The '.' character is used to mark the
boundary between hierarchy levels. For example, the Handle System
data type "a.b" may be considered as a sub-type "b" under the type
"a". Similarly, handle values of <type> "a.b.x", "a.b.y" and
"a.b.z" may be considered as handle values under the common type
hierarchy "a.b".
For any handle values, the UTF8-string in the <type> field may not
end with the '.' character. In other words, no Handle System data
type should end with the '.' character. However, the '.'
character may appear in the end of the <type> parameter in a
handle query. This is used to query for all handle values under a
common type hierarchy. For example, one may query for all handle
values under the type hierarchy "a.b" (e.g., handle values of
<type> "a.b.x", "a.b.y" and "a.b.z") by setting the <type>
parameter to "a.b.". Note here that the <type> parameter ends
with the '.' character. Details of the handle query operation can
be found in the Handle System protocol specification [8].
<data>
A sequence of octets (preceded by its length in a 4-byte unsigned
integer) that describes the resource identified by the handle. The
syntax and semantics of these octets are identified by the <type>
field.
<permission>
An eight-bit bit-mask for access control of the handle value.
Access control is defined in terms of read, write, and execute
permissions, applicable to either general public or handle
administrator(s). Each handle value can have its permission field
specified as any combination of the following bits:
PUBLIC_WRITE (0x01) permission that allows anyone to
modify or delete the handle value.
PUBLIC_READ (0x02) permission that allows anyone to read
the handle value.
ADMIN_WRITE (0x04) permission that allows any handle
administrator to update or delete the
handle value.
ADMIN_READ (0x08)_ permission that allows the handle
value to be read by any handle
administrator with AUTHORITIVE_READ
privilege.
PUBLIC_EXECUTE (0x10) permission that allows anyone to
execute the program identified by the
handle value on the handle host as
anonymous user. Because of the
security risks this may have brought
up, implementations may choose not to
support such permission, or provide
options so that it can be disabled at
deployment.
ADMIN_EXECUTE (0x20) permission that allows handle
administrator(s) to run the program
identified by the handle value on the
handle server. The handle server must
authenticate the handle administrator
before executing the program. The
handle administrator must have an
established account on the handle
server. The execution of the handle
value should assume the same privilege
as the one given to the account for
the handle administrator. Because of
the security risks this may have
brought up, implementations may choose
not to support such permission, or
provide options so that it can be
disabled at deployment.
Note that a handle value with no PUBLIC_READ nor ADMIN_READ
permission can not leave the handle server. It may be used, for
example, to store secret keys for authentication purposes. A
handle value with neither PUBLIC_WRITE nor ADMIN_WRITE permission
makes the handle value immutable and cannot be deleted by any
handle administrator (via the Handle System protocol).
The administrator for a given handle must specify the permission
for each handle value. Implementations may choose PUBLIC_READ and
ADMIN_WRITE as the default permission for each handle value.
Handle servers must check permissions before fulfilling any client
request.
<TTL>
An octet followed by a 4-byte integer that specifies the Time-To-
Live of the value record. It is used to describe how long the
value record can be cached before the source of the information
should again be consulted. A zero value for a TTL indicates that
the value record should only be used for the transaction in
progress and should not be cached. Any non-zero TTL is defined in
terms of a TTL type (specified in the first octet), followed by
the TTL value (the 32-bit unsigned integer that follows the TTL
type). The TTL type indicates whether the TTL value is absolute
or relative. The absolute TTL value defines the time to live in
terms of seconds since 00:00:00 UTC, January 1st 1970. A relative
TTL specifies the time to live in terms of the number of seconds
elapsed since the value was obtained by the client from any handle
server.
<timestamp>
An 8-byte (long) integer that records the last time the value was
updated at the server. The field contains elapsed time since
00:00:00 UTC, January 1970 in milliseconds. The choice of
milliseconds is to avoid potential collision when updating the
value.
<reference>
A 4-byte integer followed by a list of references to other handle
values. The integer specifies the number of references in the
list. Each reference in the list refers to another handle value
in terms of a UTF8-string and a 4-byte integer (where the UTF8-
string is the handle name and the integer is the value index).
References are generally used to add credentials to the current
handle value. For example, a handle value may make itself more
trust-worthy by referring to a digital signature issued by a
commonly trusted entity.
By default, the Handle System returns all the handle values with
public-read permission in response of any resolution request. It is
possible for a client to ask for a subset of those values with
specific data type (e.g., all URLs assigned to the handle). The
client may also ask for a specific handle value based on a specific
value index.
Each handle value can be uniquely referenced by the combination of
the handle and its value index. Care must be taken when changing the
value index as it may break an existing reference to the handle
value. For example, suppose the handle X/Y has a value whose index
is 1. That value may be referred to as X/Y:1. If the handle
administrator changes the value index from 1 to 2, the reference to
X/Y:1 will become obsolete. Any reference to the handle value will
have to change to X/Y:2.
Value records assigned to any handle may or may not have continuous
index numbers. Nor can it be assumed that the index will start with
0 or 1. A handle administrator may assign a handle value with any
index as long as each index is unique within the value set.
A handle value may be "privatized" or "disabled" by setting its
<permission> field as "authorized-read". This limits read-access to
the handle administrator only. The "privatized" value can then be
used to keep any historical data (on behalf of the handle
administrator) without exposing it to public. Such approach may also
be used to keep any obsolete handle or naming authority from being
reused accidentally.
3.2. Pre-defined Handle Data Types
Every handle value must have a data type specified in its <type>
field. The Handle System provides a type registration service that
allows organizations to register new data types for their
applications. Data types can be registered as handles under the
naming authority "0.TYPE". For example, the URL data type is
registered under the Handle System as the handle "0.TYPE/URL". The
handle may have a handle value that refers to RFC1738 [9], an IETF
standard document that defines the syntax and semantics of URL.
The Handle System pre-defines a set of data types to carry out the
handle service. For example, HS_ADMIN is a pre-defined data type
used to describe handle administrators or administrator groups.
HS_SITE is a pre-defined data type to describe the service interface
of any Handle System service component. The following sections
provide detailed descriptions of these pre-defined data types under
the Handle System.
3.2.1. Handle Administrator: HS_ADMIN
Each handle has one or more administrators. Any administrative
operation (e.g., add, delete or modify handle values) can only be
performed by the handle administrator with adequate privilege.
Handle administrators are defined in terms of HS_ADMIN values. Every
handle must have at least one HS_ ADMIN value that defines its
administrator. Each HS_ADMIN value can be used to define a set of
handle administrators sharing the same administration privilege.
Handles with multiple administrators of different privileges may have
multiple HS_ADMIN values. HS_ADMIN values are used by the Handle
System to authenticate handle administrators before fulfilling any
handle administration request.
Naming authorities, as described above, are themselves registered as
handles under the reserved naming authority "0.NA". These handles
are referred to as naming authority handles. Administrators for any
naming authority are defined as the administrators of the
corresponding naming authority handle. For example, "0.NA/10" is the
naming authority handle for the naming authority "10". Hence any
administrator for the naming authority handle "0.NA/10" is also the
administrator for the naming authority "10". Naming authority
administrators are the only ones who can create handles or sub-
naming authorities under the naming authority. A sub-naming
authority may define its own set of administrators to create handles
or further levels of sub-naming authorities. For example, the naming
authority "10.1045" may have a totally different group of
administrators from its parent naming authority "10".
An HS_ADMIN value is a handle value whose <type> field is HS_ADMIN
and whose <data> field consists of the following entries:
<AdminRef>
A reference to a handle value. The reference consists of the
handle name (a UTF8-string) followed by a 4-byte unsigned integer
for the handle value index. The handle value identifies the set
of administrators for the handle.
<AdminPermission>
A 16-bit bit-mask that defines the administration privilege of the
set of handle administrators identified by the HS_ADMIN value.
The <AdminRef> entry refers to a handle value that can be used to
authenticate the handle administrator. Such handle value is called
the handle administrator reference. The handle administrator
reference may contain the secret key, public key, or X.509
certificate [10] provided by the handle administrator. For example,
the <AdminRef> entry may contain a handle administrator reference
whose <type> field is DSS_WITH_DES_CBC_SHA and whose <data> field
contains a DES secret key [11], for use in the Cipher Block Chaining
(CBC) mode of operation [12, 13]. The secret key can be used by the
handle server to authenticate the handle administrator. For stronger
cryptographic algorithm, the handle administrator reference may
contain a set of Triple-DES keys [23] and set its <type> to be DES-
EDE3-WITH-CBC.
A single handle may be assigned with both the HS_ADMIN value and the
handle administrator reference. In other words, the <AdminRef> entry
may refer to a handle value assigned to the same handle that has the
HS_ADMIN value. In this case, authentication of the handle
administrator does not rely on any other handles. Alternatively, the
handle administrator reference may be a handle value under a
different handle. Thus HS_ADMIN values from different handles may
share a common handle administrator reference. This feature allows
sharing of handle administrators among different handles. The handle
administrator reference contains the secret key, public key, or X.509
certificate provided by the administrator of these handles.
Handle administrator reference may be of type HS_VLIST and has its
<data> field contain a list of references to other handle values.
Each of these handle values defines a handle administrator reference.
The HS_VLIST value defines an administrator group. Each handle
administrator reference from the HS_VLIST is a member of the
administrator group. Each handle value reference is defined in terms
of a <handle>:<index> pair. An administrator group may also contain
other administrator groups as its members. This allows administrator
groups to be defined in a hierarchical fashion. Care must be taken,
however, to avoid cyclic definition of administrators or
administrator groups. Multiple levels of administrator groups should
be avoided due to their lack of efficiency, but will not be signaled
as an error. Client software should be prepared to detect any
potential cyclic definition of administrators or <AdminRef> entries
that point to non-existent handle values and treat them as an error.
A handle can have multiple HS_ADMIN values, each of which defines a
different handle administrator. Different administrators can play
different roles or be granted different permissions. For example,
the naming authority handle "0.NA/10" may have two administrators,
one of which may only have permission to create new handles under the
naming authority, while the other may have permission to create new
sub-naming authorities (e.g., "10.1045"). The set of possible
permissions for a handle administrator is defined as follows:
Add_Handle (0x0001)
This permission allows naming authority administrator to create new
handles under a given naming authority.
Delete_Handle (0x0002)
This permission allows naming authority administrator to delete
handles under a given naming authority.
Add_NA (0x0004)
This permission allows the naming authority administrator to create
new sub-naming authorities.
Delete_NA (0x0008)
This permission allows naming authority administrator to delete an
existing sub-naming authority.
Modify_Value (0x0010)
This permission allows handle administrator to modify any handle
values other than HS_ADMIN values. HS_ADMIN values are used to
define handle administrators and are managed by a different set of
permissions.
Delete_Value (0x0020)
This permission allows handle administrator to delete any handle
value other than the HS_ADMIN values.
Add_Value (0x0040)
This permission allows handle administrator to add handle values
other than the HS_ADMIN values.
Modify_Admin (0x0080)
This permission allows handle administrator to modify HS_ADMIN
values.
Remove_Admin (0x0100)
This permission allows handle administrator to remove HS_ADMIN
values.
Add_Admin (0x0200)
This permission allows handle administrator to add new HS_ADMIN
values.
Authorized_Read (0x0400)
This permission grants handle administrator read-access to handle
values with the ADMIN_READ permission. Administrators without this
permission will not have access to handle values that require
authentication for read access.
LIST_Handle (0x0800)
This permission allows naming authority administrator to list
handles under a given naming authority.
LIST_NA (0x1000)
This permission allows naming authority administrator to list
immediate sub-naming authorities under a given naming authority.
Administrator permissions are encoded in the <AdminPermission> entry
in the <data> field of any HS_ADMIN value. Each permission is
encoded as a bit flag. The permission is granted if the flag is set
to 1, otherwise it is set to 0.
Figure 3.2.1 shows an example of HS_ADMIN value that defines an
administrator for the naming authority handle "0.NA/10". In figure
3.2.1, a naming authority administrator is identified by an HS_ADMIN
value assigned to the naming authority handle "0.NA/10". The
administrator can be authenticated based on the handle value
"0.NA/10":3, which is the handle value assigned to the naming
authority handle "0.NA/10" and has its index set to 3. The handle
value "0.NA/10":3 may contain the secret or public key used by the
administrator. The administrator is granted permission to add,
delete, or modify sub-naming authorities under "10", and add or
delete handles directly under the naming authority. The
administrator may also add, delete, or modify any handle values
assigned to the naming authority handle except those HS_ADMIN values.
In other words, the administrator is not allowed to add, delete, or
modify any administrators for the naming authority.
-------------------------------------------------------------
------------------------------------------------------------- |
------------------------------------------------------------- | |
| | | |
| <index>: 2 | | |
| <type>: HS_ADMIN | | |
| <data>: | | |
| <AdminRef>: "0.NA/10": 3 | | |
| <AdminPerm>: Add_NA, Delete_NA, | | |
| Add Handle, Delete_Handle, | | |
| Add_Value, Delete_Value, Modify_Value, | | |
| Authorized_Read, List_Handle, List_NA | | |
| | | |
| <TTL>: 24 hours | | |
| <permission>: PUBLIC_READ, ADMIN_WRITE | | |
| <reference>: {empty} | |-
| |-
-------------------------------------------------------------
Figure 3.2.1: Administrator for the naming authority
handle "0.NA/10"
HS_ADMIN values are used by handle servers to authenticate the handle
administrator before fulfilling any administrative requests. The
server authenticates a client by checking whether the client has
possession of the secret key (or the private key) that matches the
one in any of the handle administrator references. The
authentication is carried out via the Handle System authentication
protocol as described later in this document.
HS_ADMIN values may require authentication for read access in order
to prevent public exposure of the data. Additionally, the handle
administrator reference that contains the administrator's secret key
should have neither PUBLIC_READ nor ADMIN_READ permission to prevent
the key from leaving the server.
3.2.2. Service Site Information: HS_SITE
The Handle System consists of a single distributed global handle
service, also known as the Global Handle Registry (GHR), and
unlimited number of Local Handle Services (LHSs). Each handle
service, global or local, may be replicated into multiple service
sites. Each service site may consist of multiple server computers.
Service requests targeted at any handle service can be distributed
into different service sites, and into different server computers
within any service site. Such architecture assures that each handle
service could have the capacity to manage any large number of handles
and handle requests. It also provides ways for each handle service
to avoid any single point of failure.
Each handle service, global or local, may provide the same set of
functions for resolving and administering its collection of handles.
Handle services differ primarily in that each service is responsible
for a distinct set of handles. They are also likely to differ in the
selection, number, and configuration of their components such as the
servers used to provide handle resolution and administration.
Different handle services may be created and managed by different
organizations. Each of them may have their own goals and policies.
A service site typically consists of a cluster of server computers
residing within a local Internet domain. These computers work
together to distribute the data storage and processing load at the
site. It is possible, although not recommended, to compose a site
from servers at widely different locations. Further, it is even
possible to compose two different sites from the same set of servers.
Each service site is defined by an HS_SITE value. HS_SITE is a
pre-defined Handle System data type. An HS_SITE value defines a
service site by identifying the server computers (e.g., IP addresses)
that comprise the site along with their service configurations (e.g.,
port numbers). HS_SITE values are typically assigned to naming
authority handles. The set of HS_SITE values assigned to a naming
authority handle is called the service information for the naming
authority.
The service information is managed by the naming authority
administrator. It must reflect the configuration of the handle
service for the naming authority. Note that an additional layer of
indirection, called a service handle, can be used to allow multiple
naming authorities to reference a single set of HS_SITE values, as
described later in this document (see section 3.2.3). Clients of the
Handle System depend on the service information to locate the
responsible handle server before they can send their service
requests. The service information can also be used by clients to
authenticate any service response from the handle server.
An HS_SITE value is a handle value whose <type> field is HS_SITE and
whose <data> field consists of the following entries:
<Version>
A 2-byte value that identifies the version number of the HS_SITE.
The version number identifies the data format used by the HS_SITE
value. It is defined to allow backward compatibility over time.
This document defines the HS_SITE with version number 0.
<ProtocolVersion>
A 2-byte integer value that identifies the handle protocol version.
The higher byte of the value identifies the major version and the
lower byte the minor version. Details of the Handle System
protocol is specified in [8].
<SerialNumber>
A 2-byte integer value that increases by 1 (and may wrap around
through 0) each time the HS_SITE value gets changed. It is used in
the Handle System protocol to synchronize the HS_SITE values
between client and server.
<PrimaryMask>
An 8-bit mask that identifies the primary site(s) of the handle
service. The first bit of the octet is the <MultiPrimary> bit. It
indicates whether the handle service has multiple primary sites.
The second bit of the octet is the <PrimarySite> bit. It indicates
whether the HS_SITE value is a primary site. A primary site is the
one that supports administrative operations for its handles. A
<MultiPrimary> entry with zero value indicates that the handle
service has a single primary site and all handle administration has
to be done at that site. A non-zero <MultiPrimary> entry indicates
that the handle service has multiple primary sites. Each primary
site may be used to administrate handles managed under the handle
service. Handles managed by such service may identify its primary
sites using an HS_PRIMARY value, as described in section 3.2.5.
<HashOption>
An 8-bit octet that identifies the hash option used by the service
site to distribute handles among its servers. Valid options
include HASH_BY_NA (0x00), HASH_BY_LOCAL (0x01), or HASH_BY_HANDLE
(0x02). These options indicate whether the hash operation should
only be applied to the naming authority portion of the handle, or
only the local name portion of the handle, or the entire handle,
respectively. The standard MD5 hashing algorithm [14] is used by
each service site to distribute handles among its servers.
<HashFilter>
An UTF8-string entry reserved for future use.
<AttributeList>
A 4-byte integer followed by a list of UTF8-string pairs. The
integer indicates the number of UTF8-string pairs that follow.
Each UTF8-string pair is an <attribute>:<value> pair. They are
used to add literal explanations of the service site. For example,
if the <attribute> is "Organization", the <value> should contain a
description of the organization hosting the service site. Other
<attribute>s may be defined to help distinguish the service sites
from each other.
<NumOfServer>
A 4-byte integer that defines the number of servers in the service
site. The entry is followed by a list of <ServerRecord>s. Each
<ServerRecord> defines a handle server that is part of the service
site. Each <ServerRecord> consists of the following data fields:
<ServerRecord> ::= <ServerID>
<Address> <PublicKeyRecord> <ServiceInterface>
where each field is defined as follows:
<ServerID>
A 4-byte unsigned integer that uniquely identifies a server
process under the service site. <ServerID>s do not have to
begin with 1 and they don't have be consecutive numbers. They
are used to distinguish servers under a service site from each
other. Note that there can be multiple servers residing on any
given computer, each with a different <ServerID>.
<Address>
The 16-byte IPv6 [15, 16] address of the handle server. Any
IPv4 address should be presented as :::::FFFF:xxxx:xxxx (where
xxxx:xxxx can be any 4-byte IPv4 address).
<PublicKeyRecord>
A 4-byte integer followed by a byte-array that contains the
server's public key. The integer specifies the size of the
byte-array. The byte-array (for the publickey) consists of
three parts: a UTF8-string that describes the key type, a
two-byte option field reserved for future use, and a byte-array
that contains the public key itself. For example, the UTF8-
String "DSA_PUB_KEY" indicates that the <PublicKeyRecord>
contains a DSA public key. The storage format of the DSA key
in the byte-array could then be found from the handle
"0.type/DSA_PUB_KEY". Public key in the <PublicKeyRecord> can
be used to authenticate any service response from the handle
server.
The <PublicKeyRecord> may also contain an X.509 certificate.
This happens if the key type field contains the UTF8-String
"CERT.X509". In this case, "CERT.X509" will map to the handle
"0.TYPE/CERT.X509". The handle may contain information that
describes the syntax and semantics of the public key or its
certificate. Additional key type may also be registered (as
handles under "0.TYPE") to further distinguish different kinds
of X.509 certificates. For example, "CERT.X509.DSA" may be
used to denote X.509 certificates that contain DSA public keys.
If the key type field of a <PublicKeyRecord> declares
"CERT.X509.DSA", the <PublicKeyRecord> must contain a X.509
certificate with a DSA public key in it."
<ServiceInterface> ::= <InterfaceCounter>
* [ <ServiceType>
<TransmissionProtocol>
<PortNumber> ]
A 4-byte integer followed by an array of triplets consisting of
<ServiceType, TransmissionProtocol, PortNumber>. The 4-byte
integer specifies the number of triplets. Each triplet lists a
service interface provided by the handle server. For each
triplet, the <ServiceType> is an octet (as a bit mask) that
specifies whether the interface is for handle resolution
(0x01), handle administration (0x02), or both. The
<TransmissionProtocol> is also an octet (as a bit mask) that
specifies the transmission protocol. Possible transmission
protocols include TCP (0x01), UDP (0x02), and HTTP (0x04). The
<PortNumber> is a 4-byte unsigned integer that specifies the
port number used by the interface. The default port number is
2641.
Figure 3.2.2 shows an example of handle service site in terms of a
HS_SITE value. The HS_SITE value is assigned to the naming authority
handle "0.NA/10". The <PrimaryMask> indicates that it is the only
primary site of the handle service. The site consists of three
handle servers, as indicated in the <NumOfServer>. These servers
provide handle resolution and administration service for every handle
under the naming authority "10". The first server record (ServerID
0) shows two service interfaces, one for handle resolution and the
other for handle administration. Each interface has its own port.
Each server within a service site is responsible for a subset of
handles managed by the handle service. Clients can find the
responsible server by performing a common hash-operation. The hash-
operation will first convert all ASCII characters in the handle into
upper-case. It then applies the MD5 hashing upon the portion of the
converted handle string (according to the <HashOption> entry). The
result is a 16-byte integer. The absolute value of the integer will
be divided by the number of servers (specified in the <NumOfServer>
entry). The remainder is the sequence number (starting with zero) of
the <ServerRecord> listed in the HS_SITE value. From the
<ServerRecord>, clients can find the IP address of the handle server
for their handle requests.
------------------------------------------------------------
------------------------------------------------------------ |
----------------------------------------------------------- | |
| | | |
| <index>: 2 | | |
| <type>: HS_SITE | | |
| <data>: | | |
| Version: 0 | | |
| ProtocolVersion: 2.1 | | |
| SerialNumber: 1 | | |
| PrimaryMask: | | |
| MultiPrimary: FALSE | | |
| PrimarySite: TRUE | | |
| HashOption: HASH_BY_HANDLE | | |
| HashFilter: {empty UTF8-String} | | |
| AttributeList: 0 {followed by no attributes} | | |
| NumOfServer: 3 | | |
| {followed by a list of <ServerRecord>} | | |
| | | |
| ----------------------------------------- | | |
| ------------------------------------------ | | | |
| ------------------------------------------ || | | |
| | ServerID: 1 ||| | | |
| | Address: :FFFF:132.151.1.155 ||| | | |
| | PublicKeyRecord: HS_DSAKEY, iQCuR2R... ||| | | |
| | ServiceInterface ||| | | |
| | ServiceType: Resolution_Only ||| | | |
| | TransmissionProtocol: TCP & UDP ||| | | |
| | PortNumber: 2641 ||| | | |
| | ||| | | |
| | ServiceType: Admin only ||| | | |
| | TransmissionProtocol: TCP || | | |
| | PortNumber: 2642 | | | |
| ------------------------------------------ | | |
| | | |
| <TTL>: 24 hours | | |
| <permission>: PUBLIC_READ, ADMIN_WRITE | | |
| <reference>: {empty} | |-
| |-
-----------------------------------------------------------
Fig. 3.2.2: The primary service site for the naming authority "10"
3.2.3. Naming Authority Delegation Service: HS_NA_DELEGATE
The HS_NA_DELEGATE is a pre-defined Handle System data type. It has
the exact same format as the HS_SITE value. Like HS_SITE values,
HS_NA_DELEGATE values are used to describe service sites of a LHS.
HS_NA_DELEGATE values may be assigned to naming authority handles to
designate naming authority administration to a LHS. A naming
authority handle with a set of HS_NA_DELEGATE values indicates that
all child naming authorities of the naming authority are managed by
the LHS described by the HS_NA_DELEGATE values.
For example, suppose the naming authority "foo.bar" decides to have
its child naming authorities delegated to a LHS. To achieve this,
one may assign the naming authority handle "0.NA/foo.bar" with a set
of HS_NA_DELEGATE values that describes the LHS. The set of
HS_NA_DELEGATE values indicate that the service information of any
child naming authority of the "foo.bar", such as "foo.bar.baz", can
be found by querying the naming authority handle "0.NA/foo.bar.baz"
from the LHS.
3.2.4. Service Handle: HS_SERV
Any handle service, global or local, can be defined in terms of a set
of HS_SITE values. These HS_SITE values may be assigned directly to
the relevant naming authority handle, or an additional level of
indirection may be introduced through the use of service handles. A
service handle may be thought of as a name for a handle service. It
may be used to maintain the HS_SITE values for the handle service and
referenced from a naming authority handle via a HS_SERV value. A
HS_SERV value is a handle value whose <type> field is HS_SERV and
whose <data> field contains the reference to the service handle.
HS_SERV values are typically assigned to naming authority handles to
refer clients to the responsible handle service.
Use of service handle allows sharing of service information among
multiple naming authorities. It also allows changes to service
configuration (e.g., adding a new site) to be made in one place
rather than in every naming authority handle involved. The mechanism
may also be used to support service referral from one handle service
to another for whatever reason.
A naming authority handle may have no more than one HS_SERV value
assigned to it, otherwise it is an error. If a naming authority
handle has both a list of HS_SITE values and an HS_SERV value, the
HS_SITE values should be used as the service information for the
naming authority.
Service handles can be registered under the reserved naming authority
"0.SERV". Handles under "0.SERV" are managed by the GHR. For
example, the service handle "0.SERV/123" may be created to maintain
the service information for the handle service that manages handles
under the naming authority "123" and any of its sub-naming
authorities.
Similarly, a service handle "0.SERV/a.b.c" may be created to host the
service information for the handle service that manages handles under
the naming authority "a.b.c".
The use of service handles raises several special considerations.
Multiple levels of service handle redirection should be avoided due
to their lack of efficiency, but are not signaled as an error.
Looped reference of service handles or HS_SERV values that point to
non-existent service handles should be caught and error conditions
passed back to the user.
3.2.5. Alias Handle: HS_ALIAS
In practice, it is very possible that a digital object may have
multiple names that will identify the object. The Handle System
supports such feature via the pre-defined data type HS_ALIAS. An
HS_ALIAS value is a handle value whose <type> field is HS_ALIAS and
whose <data> field contains a reference to another handle. A handle
with a HS_ALIAS value is an alias handle to the handle referenced in
the HS_ALIAS value. An alias handle should not have any additional
handle values other than HS_ALIAS or HS_ADMIN (for administration)
values. This is necessary to prevent any inconsistency between a
handle and its aliases.
During a handle resolution, a client may get back an HS_ALIAS value.
This indicates that the handle in question is an alias handle. The
client may then retry the query against the handle specified in the
HS_ALIAS value until final results are obtained.
The use of alias handle introduces a number of special
considerations. For example, multiple levels of aliases should be
avoided for the sake of efficiency, but are not signaled as an error.
Alias loops and aliases that point to non-existent handles should be
caught and error conditions passed back to the user.
One potential use of alias handle would be to support the transfer of
ownership of any named resource. When a resource identified by a
handle transfers from one organization to another, a new handle for
the resource may be created. To avoid inconsistency and any broken
reference, the handle used before the ownership transfer may be
changed into an alias handle and point its HS_ALIAS value to the
newly created handle.
3.2.6. Primary Site: HS_PRIMARY
HS_PRIMARY is a pre-defined data type used to designate the primary
service sites for any given handle. A handle service with multiple
primary service sites is called a multi-primary service. Otherwise
it is called a single-primary service. Each handle managed by a
multi-primary handle service may specify its primary service sites in
terms of an HS_PRIMARY value. A HS_PRIMARY value is a handle value
whose <type> field is HS_PRIMARY and whose <data> field contains a
list of references to HS_SITE values. Each of these HS_SITE defines
a primary service site for the handle.
There can be at most one HS_PRIMARY value assigned to each handle.
Otherwise it is an error. A handle with no HS_PRIMARY value but
managed by a multi-primary handle service is not an error. In this
case, every primary service site of the handle service will also be
the primary site for the handle. Handles managed by a single-primary
handle service do not need any HS_PRIMARY values and any such values
should be ignored.
3.2.7. Handle Value List: HS_VLIST
HS_VLIST is a pre-defined data type that allows a handle value to be
used as a reference to a list of other handle values. An HS_VLIST
value is a handle value whose <type> is HS_VLIST and whose <data>
consists of a 4-byte unsigned integer followed by a list of
references to other handle values. The integer specifies the number
of references in the list. The references may refer to handle values
under the same handle or handle values from any other handles. Each
reference is encoded as an UTF8-string followed by a 4-byte unsigned
integer that identifies the referenced handle and its value index.
HS_VLIST values may be used to define administrator groups for
handles. In this case, each reference in the HS_VLIST defines a
member of the administrator group and the HS_VLIST value identifies
the group as a whole. Client software must be careful, however, to
avoid cyclic definition of value references.
4. Handle System Service Model
The Handle System is a distributed global name service. It consists
of a single distributed Global Handle Registry (GHR) and unlimited
number of Local Handle Services (LHS). These service components
provide the name service (both resolution and administration) on
behalf of Handle System client components. Handle System client
components may also choose to use Handle System middle-ware
components (e.g., the Handle System caching service) for efficiency.
This section describes these components and their relationships to
each other.
4.1. Handle System Service Components
The Handle System defines a hierarchical service model. At the top
level is the single distributed global handle service, also known as
the Global Handle Registry (GHR). Underneath the GHR, there can be
any number of Local Handle Services (LHSs). Each LHS must be
registered with the GHR to manage handles under a distinct set of
naming authorities. Naming authorities are managed by the GHR via
naming authority handles (i.e., handles under the naming authority
"0.NA"). A naming authority handle can also be used to locate the
service information (in terms of HS_SITE values) that describes the
handle service responsible for handles under the naming authority.
From the service information, clients can choose a service site and
locate the responsible server for their handle requests.
Handle System service components are scalable and extensible to
accommodate any large amount of service load. A handle service,
global or local, may consist of multiple service sites, replicating
each other. Each service site may also consist of a cluster of
computers working together to serve its respective namespace. Having
multiple service sites avoids any single point of failure and allows
load balancing among these service sites. Using multiple servers at
any service site distributes the service load into multiple server
processes and allows less powerful computers to be utilized for the
name service.
4.1.1. Global Handle Registry (GHR)
The Global Handle Registry (GHR) is mainly used to manage naming
authority handles and to provide service information for every naming
authority under the Handle System. The GHR may also be used to
manage and provide resolution and administration service to non-
naming-authority handles. Unlike any LHS, which mostly manages
handles under a few naming authorities, the GHR is primarily used to
register naming authorities and provide service information for every
LHS. In other words, the GHR is the single root service that
registers every LHS and provides their service information via the
use of naming authority handle(s). Every naming authority under the
Handle System must be registered under the GHR as a naming authority
handle. The naming authority handle provides the service information
of the handle service that manages all the handles under the naming
authority. The service information may be provided in terms of a set
of HS_SITE values, or an HS_SERV value that refers to a service
handle, as described earlier.
The GHR may consist of multiple service sites, each described in a
HS_SITE value. These HS_SITE values are assigned to the designated
naming authority handle "0.NA/0.NA", also called the root handle. The
root handle is the naming authority handle that maintains the service
information for GHR. Top level naming authorities can only be
created by administrators of the root handle.
In order to communicate with the GHR, client software needs the GHR
service information beforehand. The service information may be
distributed initially with the client software, or obtained from some
other secure sources (e.g., postal mail, secure web site, etc.).
Client software may keep the service information to communicate with
the GHR until the service information becomes expired (according to
its TTL). The GHR must update its service information (assigned to
the root handle) every time it changes its configuration. Client
software with out-dated service information will be notified of the
update every time it communicates with the GHR. The GHR must be
maintained in such a way that any client software with out-dated GHR
service information can still query the root handle for the latest
update.
Fig. 4.1.1 shows the GHR service information in terms of a set of
HS_SITE values. The GHR may consist of a number of service sites,
each described in a HS_SITE value. The figure shows a GHR service
site located in US East Coast, as indicated in the <AttributeList>.
------------------------------------------------------------
------------------------------------------------------------ |
----------------------------------------------------------- | |
| | | |
| <index>: 3 | | |
| <type>: HS_SITE | | |
| <data>: | | |
| Version: 1 | | |
| ProtocolVersion: 2.1 | | |
| SerialNumber: 1 | | |
| PrimaryMask: | | |
| MultiPrimary: TRUE | | |
| PrimarySite: TRUE | | |
| HashOption: HASH_BY_HANDLE | | |
| HashFilter: {empty UTF8-String} | | |
| AttributeList: 1 | | |
| Description: Service site at US East Coast | | |
| NumOfServer: 3 | | |
| | | |
| ------------------------------------------ | | |
| ------------------------------------------ | | | |
| ------------------------------------------ || | | |
| | ServerID: 1 ||| | | |
| | Address: :FFFF:132.151.2.150 ||| | | |
| | PublicKeyRecord: HS_DSAKEY, iQCuR2Rnw... ||| | | |
| | ServiceInterface ||| | | |
| | ServiceType: Resolution & Admin ||| | | |
| | TransmissionProtocol: TCP & UDP || | | |
| | PortNumber: 2641 | | | |
| ------------------------------------------ | | |
| | | |
| <TTL>: 24 hours | | |
| <permission>: PUBLIC_READ, ADMIN_WRITE | | |
| <reference>: {empty} | |-
| |-
-----------------------------------------------------------
Figure 4.1.1: GHR service information
The GHR and its service information provide an entry point for any
client software to communicate with the Handle System. For any given
handle, client software can query the GHR for its naming authority
handle. This will return the service information of the LHS that
manages every handle under the naming authority. The service
information will direct the client software to the handle server
within the LHS that manages the handle.
4.1.2. Local Handle Service (LHS)
A Local Handle Services (LHS) manages handles under given sets of
naming authorities. Each naming authority defines a "local"
namespace that consists of all of the handles under the naming
authority. Note that a LHS is not a "local" service in terms of any
network topology. It is called a "Local" Handle Service because it
typically manages a restricted (local) namespace.
A naming authority is "homed" at a LHS if all handles under the
naming authority are managed by the LHS. A LHS may be home to
multiple naming authorities. On the other hand, a naming authority
may only be "homed" at one LHS. Note that a naming authority may
also be homed at the GHR.
------------------------------------------------------------
------------------------------------------------------------ |
----------------------------------------------------------- | |
| <index>: 3 | | |
| <type>: HS_SITE | | |
| <data>: | | |
| Version: 1 | | |
| ProtocolVersion: 2.1 | | |
| SerialNumber: 1 | | |
| PrimaryMask: | | |
| MultiPrimary: FALSE | | |
| PrimarySite: TRUE | | |
| HashOption: HASH_BY_LOCALNAME | | |
| HashFilter: {empty UTF8-String} | | |
| AttributeList: 1 | | |
| Description: Local Service for "10" | | |
| NumOfServer: 2 | | |
| ----------------------------------------- | | |
| ----------------------------------------- | | | |
| | ServerID: 1 || | | |
| | Address: :FFFF:132.151.3.150 || | | |
| | PublicKeyRecord: HS_DSAKEY, iQCuR2R... || | | |
| | ServiceInteface: || | | |
| | ServiceType: Resolution & Admin || | | |
| | TransmissionProtocol: TCP & UDP || | | |
| | PortNumber: 2641 |' | | |
| -----------------------------------------' | | |
| <TTL>: 24 hours | | |
| <permission>: PUBLIC_READ, ADMIN_WRITE | |-
| <reference>: {empty} |-
-----------------------------------------------------------
Figure 4.1.2: LHS service information
Like the GHR, a LHS may also consist of many service sites with each
site described by an HS_SITE value. The set of HS_SITE values for
any LHS may be assigned to a service handle or to the relevant naming
authority handle(s). Fig. 4.1.2 shows an example of HS_SITE values
for a LHS. These HS_SITE values are assigned to the naming authority
handle "0.NA/10". This suggests that the naming authority "10" is
"homed" at the LHS specified in these HS_SITE values. Clients may
query the GHR to obtain the service information in order to
communicate with the LHS. Administrators of the naming authority
handle are responsible for maintaining the service information and
keeping it up to date.
Note that a LHS may refer its clients to another LHS in response to a
service request. This allows the LHS to further distribute its
service in a hierarchical fashion.
4.2. Handle System Middle-Ware Components
Handle System middle-ware components currently include Handle System
caching servers and Handle System proxy servers. These Handle System
middle-ware components are clients to Handle System service
components, but servers to Handle System client software. Handle
System middle-ware components are used to provide additional
interfaces to the basic handle service. For example, a Handle System
caching server may be used to share resolution results within a local
community. Additionally, a Handle System proxy server can be used to
bypass any organizational firewall via HTTP tunneling.
4.2.1. Handle System Caching Service
Handle System caching service can be used to reduce the network
traffic between Handle System clients and servers. Caching handle
data, including the service information of any LHS, allows re-use of
information obtained from earlier queries.
Each handle value contains a <TTL> (Time to Live) field that tells a
caching service how long the cached value may be regarded as valid.
A zero-value TTL indicates that the value can only be used for the
transaction in progress and should not be cached. A caching service
may obtain its data directly from a handle service, or from another
caching service that eventually gets its data from the handle
service.
A caching service may be defined in terms of an HS_SITE value and may
consist of multiple caching servers. For any given handle, clients
can find the responsible caching server within the caching service by
using the same hashing algorithm as used in locating the handle
server within any handle service.
Caching services are not part of any Handle System administration or
authentication hierarchy. The Handle System protocol does not
authenticate any response from a caching service. Clients are
responsible to set up their trust relationship with the caching
service that they select. They will also rely on the caching service
to properly authenticate any response from any handle server.
4.2.2. Handle System Proxy Server
Handle System proxy servers can be used to enable handle resolution
via other Internet protocols. For example, CNRI has built and made
available a Handle System HTTP Proxy Server that will process any
handle resolution in terms of HTTP protocol. The current DNS address
for the proxy server is at "hdl.handle.net". The proxy server allows
any handle to be resolved via a HTTP URL. The URL can be constructed
as "http://hdl.handle.net/<handle>", where <handle> can be any handle
from the Handle System. For example, the handle
"ncstrl.vatech_cs/tr-93-35" can be resolved via the HTTP URL
"http://hdl.handle.net/ncstrl.vatech_cs/tr-93-35" from any web
browser. In this case, the URL is sent to the proxy server in terms
of a HTTP request. The proxy server will query the Handle System for
the handle data and return the results in terms of HTTP response.
Using HTTP URLs allows handles to be resolved from standard web
browsers without any additional client software. However, such
reference to the handle also ties itself to the proxy server. If the
proxy server changes its DNS name or otherwise becomes invalid, the
reference (i.e., the HTTP URL) to the handle will break. Thus the
selection or use of proxy server should be carefully evaluated.
Proxy servers are not part of any Handle System administration or
authentication hierarchy. The Handle System protocol does not
authenticate any response from a proxy server. Clients are
responsible to set up their trust relationship with the proxy server
that they select. They will also rely on the proxy server to
properly authenticate any response from any handle server.
4.3. Handle System Client Components
Handle System client components are client software that communicates
with the Handle System service components. Client software may speak
the Handle System protocol and send its request directly to a service
component. The response from the service component may be the final
answer to the request, or a referral to another service component.
The client software will have to follow the referral in order to
complete the transaction.
Client software may also be configured to tunnel its request via a
middle-ware component. The middle-ware component will thus be
responsible for obtaining the final result and returning it to the
client. Unlike service components, middle-ware components will only
return final results of client's request. No service referral will
be returned from middle-ware components.
Various Handle System client components may be developed for various
applications. The CNRI Handle System Resolver [17] is one such
component. The resolver extends web browsers (e.g., Netscape or
Microsoft Internet Explorer) in such a way that handles can be
resolved directly in terms of "hdl:" Uniform Resource Identifiers
(URIs). The Grail web browser [18], a freely downloadable software
developed in Python [19], also supports the "hdl:" URI scheme and
will resolve handles accordingly. For example, the handle
"10.1045/july95-arms" may be resolved by entering its handle URI as
"hdl:10.1045/july95-arms" into any of these resolver-enabled
browsers. Details of the handle URI syntax will be specified in a
separate document.
5. Handle System Operation Model
Handle System operations can be categorized into resolution and
administration. Clients use the handle resolution service to query
for any handle values. Handle administration allows clients to
manage handles, including adding and deleting handles, and updating
their values. It also deals with naming authority administration via
naming authority handles. This section explains how various Handle
System components work together to accomplish these service
operations.
Both resolution and administration may require authentication of the
client. The authentication can be done via the Handle System
authentication protocol described later in this section. Whether
authentication is required or not depends on the kind of operation
involved and the permissions assigned to the relevant handle value,
and policies deployed by the relevant service components.
The Handle System protocol specifies the syntax and semantics of each
message exchanged between Handle System clients and its server
components. This section provides a high level overview of the
protocol used to accomplish any service operation. The exact
programmatic detail of each message (i.e., their byte layout or
syntax) is specified in a separate document [8].
5.1. Handle System Service Request and Response
The Handle System provides its service in response to client
requests. A client may send a request to any handle server to
provoke a response. The response either provides an answer to the
request, or a status code with associated information that either
refers the request to another service component, asks for client
authentication, or signals some error status.
Each handle under the Handle System is managed by its home service.
The naming authority handle provides the service information (in
terms of HS_SERV or HS_SITE values) of the handle service that
manages all handles under the naming authority. Any handle request
must be directed to the home service of the handle in question.
Clients may find the home service by querying the corresponding
naming authority handle against the GHR. Alternatively, this
information may be found in a local cache or even be part of a local
client configuration. Given the service information, clients may
select a service site and locate the responsible handle server within
the site.
To resolve the handle "ncstrl.vatech_cs/te-93-35", for example,
client software needs to know the home service for the naming
authority "ncstrl.vatech_cs". The home service can be obtained by
querying the naming authority handle "0.NA/ncstrl.vatech_cs" against
the GHR. The GHR will return the service information in terms of the
HS_SITE values assigned to the naming authority handle. From the
service information, clients can pick a service site, find the
responsible handle server within the site, and send the resolution
request to the handle server.
Clients may require digital signatures from a handle server in order
to authenticate any response from the server. The signature can be
generated using the server's private key. Clients may verify the
signature using the public key available from the service information
(refer to the <PublicKeyRecord> entry discussed in 3.2.2).
A communication session may also be established between any client
and handle server. Each session is identified by a unique session ID
managed by the server. A session may be used to manage requests that
require multiple interactions. It may also be used to share any TCP
connection or authentication information among multiple service
transactions. Each session may establish a session key and use it to
authenticate any message exchanged within the session. It may also
be used to encrypt any message between the client and the server to
achieve data confidentiality.
The following diagram shows a handle resolution process in terms of
messages exchanged between client software and Handle System service
components. In this case, the client is trying to resolve the handle
"ncstrl.vatech_cs/tr-93-35". It assumes that the client has yet
obtained the service information of the LHS "homed" by the naming
authority "ncstrl.vatech.cs". The client has to get the service
information from the naming authority handle managed by the GHR. The
service information allows the client to locate the responsible LHS
and query for the handle value.
[HS Client] ----------------------------> [Global Handle Registry]
1. ask for the service
information from the
naming authority handle
"0.NA/ncstrl.vatech_cs"
[HS Client] <---------------------------- [Global Handle Registry]
2. service information for
the naming authority
"ncstrl.vatech_cs"
[HS Client] ----------------------------> [Local Handle Service]
3. query the handle
"ncstrl.vatech_cs/tr-93-35"
against the responsible
handle server
\... ...
(optional client authentication, depending on the service request)
\... ...
[HS Client] <---------------------------- [Local Handle Service]
4. query result from the handle
server + (optional) server
signature
Figure 5.1: Handle resolution example
In Figure 5.1, the client is configured to communicate with the GHR
for any handle service. In this case, the client first queries the
GHR to find the home service for the handle's naming authority. The
GHR returns the service information of the LHS that manages every
handle under the naming authority. From the service information, the
client can find the responsible handle server and query the server
for the handle. The server may set up a session to authenticate the
client if any of the handle value requires authentication.
Otherwise, the server will simply return the handle value to the
client. The server may send a digital signature as part of its
response if required by the client.
The above procedure assumes that the client software already has the
GHR service information. That information was likely obtained from
the client software distribution. The GHR will notify the client
software if it learns that the service information used by the client
software is out of date. Client software may retrieve the latest
service information from the root handle "0.NA/0.NA". The root handle
also maintains the public key that may be used to authenticate the
service information.
Note that a client may cache the service information of any naming
authority so that subsequent queries for handles under the same
naming authority may reuse the service information and bypass the
first two steps shown in Figure 5.1. Client software may also be
configured to query a caching or proxy server directly for any
handle. In this case, the caching or proxy server will act as the
[HS Client] in Figure 5.1 before returning the query result to the
client.
Client software under certain organization may also elect to bypass
the GHR and communicate directly with a LHS managed by the
organization. Doing so may achieve quicker response for handles
managed under the LHS. The client software will be referred to the
GHR for handles not managed by the LHS.
5.2. Handle System Authentication Protocol
The Handle System supports handle administration over the public
Internet. Access controls can be defined on each handle value. The
Handle System authentication protocol is the protocol used by any
handle server to authenticate handle administrator upon any
administration request. The authentication is also necessary when
clients query for handle values that are read-only by the handle
administrator. Handle administration include adding, deleting or
modifying handle values, and adding or deleting handles. Naming
authority administrations are carried out as handle administrations
over the corresponding naming authority handles.
The Handle System authentication protocol does not perform any server
authentication. However, a client may authenticate any server
response by asking the server to sign its response with digital
signature.
By default, the Handle System authenticates clients via a challenge-
response protocol. That is, after receiving a client's request, the
server issues a challenge to the client if authentication is
necessary. To be authenticated as the administrator, the client has
to return a challenge-response, a message that demonstrates
procession of the administrator's secret. The secret may be the
private key or the secret key of the administrator. This challenge-
response allows the server to authenticate the client as the handle
administrator. Upon successful authentication, the server will
fulfill the client's request if the administrator is given sufficient
permission.
For example, suppose a client sends a request to the handle server to
add a new handle value. The server will issue a challenge to the
client in order to authenticate the client as one of the handle
administrators. If the client possesses the private key of the
administrator, she can use it to sign the server's challenge and
return the signature as part of her challenge-response. The server
will validate the signature in order to authenticate the client. The
client will be notified if the validation fails. Otherwise, the
server will further check if the administrator has the permission to
add the handle value. If so, the server will add the handle value
and report success to the client. Otherwise, a permission-denied
message will be returned.
The following diagram shows a typical authentication process in terms
of the messages exchanged between the client and the handle server.
[Client] --------------------------------> [Handle Server]
1. client request
+ (optional) client credential
[Client] <-------------------------------- [Handle Server]
2. server's challenge to client
+ (i.e., nonce + MD5 of client request)
[Client] -------------------------------> [Handle Server]
3. reference to handle administrator
+ challenge-response from client
[Client] <------------------------------- [Handle Server]
4. server acknowledgement
Figure 5.2: Handle System authentication process
In Figure 5.2, the client sends an administration request to the
handle server (along with optional credential discussed later). The
server decides that client authentication is required and issues a
challenge to the client. The client identifies itself as a handle
administrator and returns the challenge-response to the server. The
server authenticates the client as the administrator based on the
challenge-response. It also checks to see if the administrator is
authorized for the administration request. If so, the server will
fulfill the request and acknowledge the client.
Handle servers must authenticate the client before fulfilling any
request that requires administrator privilege. The exact
authentication process varies depending on whether public key or
secret key is used by the administrator. It also depends on whether
the handle used to store the administrator's key is managed by the
same handle server or not.
When public key is used, the challenge-response from the client
contains its digital signature over the server's challenge. The
server can authenticate the client by verifying the digital signature
based on the administrator's public key. If secret key is used, the
challenge-response from the client carries the Message Authenticate
Code (MAC) generated using the secret key. The server may
authenticate the client by generating the same MAC using the
administrator's secret key and comparing it against the challenge-
response.
The reference to handle administrator in Fig 5.2 is also called a
key-reference. It refers to a handle value that contains the key
used by the administrator. If the key-reference is managed by the
same handle server (e.g., a handle value assigned to the same
handle), the server may use the key directly to do the
authentication. If the key-reference is managed by some other handle
server (whether or not within the same handle service), the server
will have to send a verification-request to this other handle server,
call it the key-server, in order to authenticate the client. The
verification-request to the key-server carries both the server's
challenge and the client's challenge-response. The key-server will
return a verification-response, signed using the key-server's private
key. The content of the verification-response will depend on the
handle value referenced by the key-reference. If the key-reference
refers to a public key used by the administrator, the verification-
response will contain the public key of the administrator.
Otherwise, the key-server will verify the challenge-response on
behalf of the requesting server and return the result in the
verification-response. The following diagram shows the control flow
of the authentication process where the key-reference refers to a
handle value that contains the administrator's public (or secret) key
and the key-server is some other handle server.
-------- -------------
| | 1. client request. | |
| | -------------------------------> | |
| | | |
| | 2. session ID | |
| | + server's challenge | |
| Handle | <------------------------------- | Handle |
| System | | server |
| client | 3. session ID | receiving |
| | + response to the challenge | client |
| | + administrator reference | request |
| | --------------------------------> | |
| | | |
| | 6. server acknowledgement | |
| | <------------------------------- | |
-------- -------------
| ^
4. Verification | | 5. verifi-
request | | cation
| | response
| | (signed)
V |
--------------------------
| The handle server (the |
| key-server) that manages |
| the key referenced by |
| the key-reference |
--------------------------
Figure 5.3: Authentication process requiring verification
from a second handle server
Secret key based authentication via a second handle server, i.e., the
key server, provides a convenient way to share a common secret key
(e.g., pass phrase) among handles managed by different handle
servers. However, it should not be used to manage highly sensitive
handles or handle data. The authentication process itself is
expensive and relies on a third party, i.e., the key-server, for
proper operation. Additionally, the secret key itself is subject to
dictionary attack since the key-server cannot determine whether the
verification-request comes from a legitimate handle server. A handle
service may set its local policy so that secret key based
authentication can only be carried out if the handle server
(receiving the client request) is also the key-server.
Local handle services may define additional local policies for
authentication and/or authorization. Handle System service
components may also choose to use other Internet authentication
mechanisms such as Kerberos [20] or some Transport Layer Security
protocol [21]. Details of these will be addressed in a separate
document.
6. Security Considerations
Handle System security considerations are discussed in the "Handle
System Overview" [1] and that discussion applies equally to this
document.
The Handle System delegates handle administration to each handle
administrator who may or may not be the server administrator. Handle
administrators are allowed to choose their own public/secret keys
used for authentication. The security of Handle System
authentication depends on the proper key selection and its
maintenance by the handle administrator. Handle administrators must
choose and protect their authentication keys carefully in order to
protect the handle data. Handle server implementations may deploy
policies that regulate the selection of public/secret keys used for
authentication. For example, a handle server may require that any
authentication key must be no less than certain number of bits. It
may also prohibit the use of secret keys because of the potential
dictionary attack.
The Handle System data model supports execution permission
(PUBLIC_EXECUTE, ADMIN_EXECUTE) for each handle value. While this
allows better sharing of network resources, it also raises many
security considerations. Execution privilege should be restricted
within the permissions of certain user account (corresponding to the
handle administrator) on the server to prevent system-wide
disruption. Switching between computing platforms for the server
should also be careful to avoid any unexpected behavior.
Implementations may choose not to support the execution permission,
or provide options so that it can be disabled.
To protect against any irresponsible use of system resource, handle
servers may implement quota control. The quota control can be used
to put limits on the number of handles under a naming authority, the
number of handle values allowed for any given handle, the maximum
size of any handle value, and the number of sub-naming authorities
under a naming authority. Handle servers must report error if the
result of a handle administration violates any of these limits.
7. Acknowledgements
This work is derived from the earlier versions of the Handle System
implementation. The overall digital object architecture, including
the Handle System, was described in a paper by Robert Kahn and Robert
Wilensky [22] in 1995. Development continued 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 and MDA-972-99-1-0018. 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. Their
contributions to this work are gratefully acknowledged.
The authors also thank Russ Housley (housley@vigilsec.com), Ted
Hardie (hardie@qualcomm.com), and Mark Baugher (mbaugher@cisco.com)
for their extensive review and comments, as well as recommendations
received from other members of the IETF/IRTF community.
8. References and Bibliography
[1] Sun, S. and L. Lannom, "Handle System Overview", RFC 3650,
November 2003.
[2] Mockapetris, P., "Domain Names - Concepts and Facilities," STD
13, RFC 1034, November 1987.
[3] Mockapetris, P., "Domain Names - Implementation and
Specification", STD 13, RFC 1035, November 1987.
[4] Wahl, M., Howes, T. and S. Kille, "Lightweight Directory Access
Protocol (v3)", RFC 2251, December 1997.
[5] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", RFC 2234, November 1997.
[6] Yergeau, F., "UTF-8, A Transform Format for Unicode and
ISO10646", RFC 2279, January 1998.
[7] The Unicode Consortium, "The Unicode Standard, Version 2.0",
Addison-Wesley Developers Press, 1996. ISBN 0-201-48345-9
[8] Sun, S., Reilly, S. and L. Lannom, "Handle System Protocol (ver
2.1) Specification", RFC 3652, November 2003.
[9] Berners-Lee, T., Masinter, L. and M. McCahill, "Uniform Resource
Locators (URL)", RFC 1738, December 1994.
[10] Housley, R., Polk, W. Ford, W. and D. Solo, "Internet X.509
Public Key Infrastructure - Certificate and Certificate
Revocation List (CRL) Profile", RFC 3280, April 2002.
[11] Federal Information Processing Standards Publication (FIPS PUB)
46-1, Data Encryption Standard, Reaffirmed 1988 January 22
(supersedes FIPS PUB 46, 1977 January 15).
[12] Federal Information Processing Standards Publication (FIPS PUB)
81, DES Modes of Operation, 1980 December 2.
[13] Balenson, D., "Privacy Enhancement for Internet Electronic Mail:
Part III: Algorithms, Modes, and Identifiers", RFC 1423,
February 1993.
[14] Rivest, R., "The MD5 Message-Digest Algorithm", RFC 1321, April
1992.
[15] Deering, S. and R. Hinden, "Internet Protocol, Version 6 (IPv6)
Specification", RFC 1883, December 1995.
[16] Hinden, R. and S. Deering, "IP Version 6 Addressing
Architecture", RFC 2373, July 1998.
[17] CNRI Handle System Resolver, http://www.handle.net/resolver
[18] Grail browser home page, http://grail.sourceforge.net/
[19] Python language website, http://www.python.org/
[20] Kohl, J. and C. Neuman, "The Kerberos Network Authentication
Service (V5)", RFC 1510, September 1993.
[21] Dierks, T. and C. Allen, "The TLS Protocol Version 1.0", RFC
2246, January 1999.
[22] R. Kahn, R. Wilensky, "A Framework for Distributed Digital
Object Services, May 1995, http://www.cnri.reston.va.us/k-w.html
[23] American National Standards Institute. ANSI X9.52-1998, Triple
Data Encryption Algorithm Modes of Operation. 1998.
9. Authors' 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
Sean Reilly
Corporation for National Research Initiatives (CNRI)
1895 Preston White Dr., Suite 100
Reston, VA 20191
Phone: 703-620-8990
EMail: sreilly@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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