| RFC : | rfc1862 |
| Title: | |
| Date: | November 1995 |
| Status: | INFORMATIONAL |
Network Working Group M. McCahill
Request For Comments: 1862 University of Minnesota
Category: Informational J. Romkey, Editor
M. Schwartz
University of Colorado
K. Sollins
MIT
T. Verschuren
SURFnet
C. Weider
Bunyip Information Systems, Inc.
November 1995
Report of the IAB Workshop on Internet Information Infrastructure,
October 12-14, 1994
Status of this Memo
This memo provides information for the Internet community. This memo
does not specify an Internet standard of any kind. Distribution of
this memo is unlimited.
Abstract
This document is a report on an Internet architecture workshop,
initiated by the IAB and held at MCI on October 12-14, 1994. This
workshop generally focused on aspects of the information
infrastructure on the Internet.
1. Introduction
The Internet Architecture Board (IAB) holds occasional workshops
designed to consider long-term issues and strategies for the
Internet, and to suggest future directions for the Internet
architecture. This long-term planning function of the IAB is
complementary to the ongoing engineering efforts performed by working
groups of the Internet Engineering Task Force (IETF), under the
leadership of the Internet Engineering Steering Group (IESG) and area
directorates.
An IAB-initiated workshop on the architecture of the "information
infrastructure" of the Internet was held on October 12-14, 1994 at
MCI in Tysons Corner, Virginia.
In addition to the IAB members, attendees at this meeting included
the IESG Area Directors for the relevant areas (Applications, User
Services) and a group of other experts in the following areas:
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gopher, the World Wide Web, naming, WAIS, searching, indexing, and
library services. The IAB explicitly tried to balance the number of
attendees from each area of expertise. Logistics limited the
attendance to about 35, which unfortunately meant that many highly
qualified experts were omitted from the invitation list.
The objectives of the workshop were to explore the architecture of
"information" applications on the Internet, to provide the IESG with
a solid set of recommendations for further work, and to provide a
place for communication between the communities of people associated
with the lower and upper layers of the Internet protocol suite, as
well as allow experience to be exchanged between the communities.
The 34 attendees divided into three "breakout groups" which met for
the second half of the first day and the entire second day. Each
group wrote a report of its activities. The reports are contained in
this document, in addition to a set of specific recommendations to
the IESG and IETF community.
2. Summary
Although there were some disagreements between the groups on specific
functionalities for architectural components, there was broad
agreement on the general shape of an information architecture and on
general principles for constructing the architecture. The discussions
of the architecture generalized a number of concepts that are
currently used in deployed systems such as the World Wide Web, but
the main thrust was to define general architectural components rather
than focus on current technologies.
Research recommendations include:
- increased focus on a general caching and replication architecture
- a rapid deployment of name resolution services, and
- the articulation of a common security architecture for information
applications.
Procedural recommendations for forwarding this work in the IETF
include:
- making common identifiers such as the IANA assigned numbers
available in an on-line database
- tightening the requirements on Proposed Standards to insure that
they adequately address security
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- articulating the procedures necessary to facilitate joining IETF
working group meetings, and
- reviewing the key distribution infrastructure for use in
information applications
3. Group 1 report: The Distributed Database Problem
Elise Gerich, Tim Berners-Lee, Mark McCahill, Dave Sincoskie, Mike
Schwartz, Mitra, Yakov Rekhter, John Klensin, Steve Crocker, Ton
Verschuren
Editors: Mark McCahill, Mike Schwartz, Ton Verschuren
3.1 Problem and Needs
Because of the increasing popularity of accessing networked
information, current Internet information services are experiencing
performance, reliability, and scaling problems. These are general
problems, given the distributed nature of the Internet. Current and
future applications would benefit from much more widespread use of
caching and replication.
For instance, popular WWW and Gopher servers experience serious
overloading, as many thousands of users per day attempt to access
them simultaneously. Neither of these systems was designed with
explicit caching or replication support in the core protocol.
Moreover, because the DNS is currently the only widely deployed
distributed and replicated data storage system in the Internet, it is
often used to help support more scalable operation in this
environment -- for example, storing service-specific pointer
information, or providing a means of rotating service accesses among
replicated copies of NCSA's extremely popular WWW server. In most
cases, such uses of the DNS semantically overload the system. The
DNS may not be able to stand such "semantic extensions" and continue
to perform well. It was not designed to be a general-purpose
replicated distributed database system.
There are many examples of systems that need or would benefit from
caching or replication. Examples include key distribution for
authentication services, DHCP, multicast SD, and Internet white
pages.
To date there have been a number of independent attempts to provide
caching and replication facilities. The question we address here is
whether it might be possible to define a general service interface or
protocol, so that caches and replica servers (implemented in a
variety of ways to support a range of different situations) might
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interoperate, and so that we might reduce the amount of wasted re-
implementation effort currently being expended. Replication and
caching schemes could form a sort of network "middleware" to fulfill
a common need of distributed services.
It should be noted that it is an open question whether it would be
feasible to define a unified interface to all caching and replication
problems. For example, very different considerations must go into
providing a system to support a nationwide video service for
1,000,000 concurrent users than would be needed for supporting
worldwide accesses to popular WWW pages. We recommend research and
experimentation to address this more general issue.
3.2 Characteristics of Solutions
While on the surface caching and replication may appear to occupy two
ends of a spectrum, further analysis shows that these are two
different approaches with different characteristics. There are cases
where a combination of the two techniques is the optimal solution,
which further complicates the situation.
We can roughly characterize the two approaches as follows:
Caching:
- a cache contains a partial set of data
- a cache is built on demand
- a cache is audience-specific, since the cache is built in
response to demands of a community
Replication:
- replicated databases contain the entire data set or a
server-defined subset of a given database
- a replicated database can return an authoritative answer about
existence of an item
- data is pushed onto the replicating server rather than pulled on
demand
While there are important differences between caches and replicated
databases, there are some issues common to both, especially when
considering how updates and data consistency can be handled.
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A variety of methods can be used to update caches and replicas:
- master-slave
- peer-to-peer
- flooding techniques (such as that used by NNTP).
Which strategy one chooses influences important characteristics of
the cache or replicated database, such as:
- consistency of data
- is locking used to achieve consistency? this influences
performance...
- are there a priori guarantees of existence of an item in the
database (is the answer authoritative, do you detect conflicts
after the fact, or is there no guarantee on authoritativeness of
the answer?)
Consistency guarantees depend on the granularity of synchronization
(ms, sec, hr, day), and there are cases where it is acceptable to
trade consistency for better performance or availability. Since there
is a range of qualities of service with respect to consistency and
performance, we would like to be able to tune these parameters for a
given application. However, we recognize that this may not be
possible in all cases since it is unlikely one can implement a high
performance solution to all of these problems in a single system.
Beyond simply performing replication or caching, there is a need for
managing cache and replication servers. There are several models for
organizing groups of caches/replication servers that range from
totally adaptive to a rigidly administered, centrally controlled
model:
- a club model. Minimal administrative overhead to join the club.
Participation is a function of disk space, CPU, available
network bandwidth.
- centrally coordinated service. Here administrators can take
advantage of their knowledge of the system's topology and the
community they intend to serve. There may be scaling problems
with this model.
- hybrid combinations of the club and centrally coordinated models
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There are a couple of models for how to organize the management of a
group of cooperating servers, but this does not address the question
of what sorts of commands the manager (be it a person or a program)
issues to a cache or replicated server. A manager needs to be able to
address issues on a server such as:
- control of caching algorithms, defining how information is aged
out of the cache based on disk space, usage demands, etc. This is
where you would control time-to-live and expiry settings.
- flushing the cache. There are circumstances where the
information source has become inaccessible and the normal cache
aging strategy is inappropriate since you will not be able to
get the information again for an indeterminate amount of time.
- management control might also be a way for information providers
to control how information is pushed on servers for maintaining
data consistency, but this raises tricky problems with trust and
authentication.
Given a common set of management controls needed, a common protocol
would allow for simplified management of a collection of caching and
replicating servers since you would be able to both control them with
a single set of commands and query them about their capabilities. A
common language/protocol would also allow different implementations
to interoperate.
Replicating or caching information immediately raises issues of
billing, access control and authentication. Ignoring authentication
and access control issues simplifies the replication and caching
problem a great deal. Exactly who is running the replication or
caching server makes a big difference in how you approach this issue.
If the information publisher runs a set of servers, they can easily
handle billing and authentication. On the other hand, if an
organization is running a cache on its firewall (a boundary cache),
and purchasing information from a vendor, there are sticky issues
regarding intellectual property in this scenario.
Selecting an appropriate cache or replica of a database is simple in
the case of a captive user group (for instance a company behind a
firewall). In this case, configuring the user's software to go
through one or more boundary caches/replication servers directs the
users to the closest server. In the more general case, there are
several replicated/cached copies of an object, so you may receive
several URLs when you resolve a URN. How do you select the best URL?
Either client developers create ad hoc performance metrics or (in an
ideal world) the lower level protocols would give the client
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application some guidance about the "closest" copy of the object. In
other words, if better information about network performance was
available from lower levels of the protocol stack, applications would
not have to build ad hoc models of network topology
We did not model the functions of a cache/replication server in
detail, but we did an (incomplete) model of some of the functions
(see Figure 1). The idea here was to start work on a general form
which might include features such as a push function for use in both
maintaining consistency and in preloading information that the
information publisher believes will be requested in the near future.
Preloading information via a push command might be a function of
observed behavior patterns (when you ask for A you'll probably want B
and C). The decision about what to preload can be made either by the
information publisher or by the cache server. The cache server has
the advantage that it has better knowledge of the use patterns of its
community. The distributed nature of links to other servers also
limit the knowledge of a single information publisher. In any case,
being able to accurately predict usage patterns can result in
significant performance enhancements for caches.
Figure 1: a rough cut at functions
requests from client (in)
|
|
|
\|/
+---------------------+
| | (management)
| cache/replicated db |<--- commands from admins,
| | publishers, caches
+---------------------+
|
|
|
\|/
requests sent to information providers (out)
in: (requests from a client)
- give me meta-info about cached object (how up-to-date,
ttl, expiry, signatures/checksum, billing information )
- give me the object
- go get the object from the net
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- cache, what objects should I pre-fetch?
(this assumes that the client software believes that the
cache/replica has some knowledge of use patterns and can
predict what the user will do next)
out: (requests sent to an information publisher or a
cache further up the food chain)
- server, do I have latest copy of this object?
- give me object x and the meta data for object x
- I have a copy of object x (announcing you have a copy
of object x to other caches or URN to URL server)
- info publisher, what objects should I pre-fetch?
(this assumes that the information publisher has some
knowledge of use patterns and can predict what the user
will do next)
management: (commands from administrators, other
cooperating caches, and object publishers)
- turn parameters (e.g. consistency) on/off
- flush the cache
- there's a new version of object x, take it
3.3 Recommendations
Caching and replication are important pieces of Internet middleware,
and solutions need to be found soon. Caches and replicas have
different performance characteristics, and there are cases where a
combination of the two provides the best solution. There are also
many strategies for updating and maintaining consistency of caches
and replicated databases, and we do not believe any single
implementation can suffice for the broad range of needs in the
Internet. One possible solution would be to define a general
protocol for a replicated distributed database and for caching so
that different information application implementations can
interoperate and be managed via a common management interface. A
common protocol would provide a framework for future protocols (e.g.,
URN2URL, DHCP) or existing protocols (e.g., Gopher or WWW) that
presently lack a consistent solution.
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4. Group 2A report: Building an Information Architecture
Karen Sollins, Abel Weinrib, Barry Leiner, Clifford Neuman, Dan
LaLiberte, Erik Huizer, John Curran, John Klensin, Lixia Zhang,
Michael Mealling, Mitchell Charity, Mike St. Johns, Paul Mockapetris
This group took as its central agenda exploring an information
architecture, the services that would instantiate such an
architecture, and the functional interfaces between a realization of
such an architecture and both layers on which it would sit and the
layers that would sit on it. In order to describe an architecture,
one must describe not only what it includes, but also what it
excludes.
4.1. The core model and service structure
The general architecture has as its centerpiece objects, or as they
are known in the Uniform Resource Identifier Working Group,
resources. An object in this architecture has several
characteristics. First, it has an identifier, assigned within the
context of some namespace. Such an identifier is globally unique and
will not be reassigned to another object. Thus, it can be said to be
globally unique for a long time. Because such an identifier must
remain unique for all time, it cannot contain location-relevant
information ... locations can and will be reused. Also, since
resources may appear in zero, one, or many locations simultaneously,
location-dependent information can lead to a vast number of
identifiers for an object, which will make it difficult to identify
separately retrieved copies of an object as being the same object.
These locations are defined by the supporting layers that provide
transport and access. Therefore the definition of locations is not
within the architecture, although their existence is accepted.
Second, an object will support one or more abstract types. Further
determination beyond this statement was not made. One can conclude
from these two points that an object cannot be part of such an
architected universe without having at least one such identifier and
without supporting at least one type if it has at least one location.
In addition, the architecture contains several other components.
First, there will be a prescribed class of objects called links that
express a relationship among other objects including the nature of
that relationship. It is through links that composite objects
composed of related objects can be created and managed. Finally,
there is a need for several sorts of meta-information, both in order
to discover identifiers (e.g. for indices and in support of
searching) and to aid in the process of mapping an identifier to one
or more potential locations. Both of these sorts of meta-information
are associated with objects, although they will be used and therefore
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most likely managed differently, to support their distinctive access
and update requirements.
Given this architecture of information objects, one can identify
several boundary points. First, something that does not have an
identifier or type is outside the architecture. Second, the
architecture does not, at this point, include any statement about
computations, or communications paradigms other than second-handedly
by assuming that traversal of links will occur. Third, although
pre-fetching, caching, and replication are important, such details
may be hidden from higher level software components, and thus are not
part of the data model exposed to the application in the normal case
(though some applications may want to specify such characteristics).
Now one can ask how such a model fits into a layered network model,
how it might be modularized and realized. We envisioned this
information layer as an information "wholesale" layer. It provides
the general, broad model and provision of shared, network-based
information. Above this sit the "retailers," the marketers or
providers of information to the marketplace of applications users.
Below the "wholesalers" lie the providers of "raw materials." Here
will be the provision of supporting mechanisms and architecture from
which information objects can come.
The remainder of this group's report describes the modular
decomposition of the wholesale layer, including the interactions
among those modules, separate discussions of the interactions first
between the retail and wholesale layers and then between the
wholesale and raw material layers. The report concludes with
recommendations for where the most effective immediate efforts could
be made to provide for the wholesale layer and make it useful.
4.2. The Wholesale Layer
In order to realize the information architecture in the network a
variety of classes of services or functionality must be provided. In
each case, there will be many instances of a sort of service,
coordinating to a lesser or greater degree, but all within the
general Internet model of autonomy and loose federation. There also
may be variants of any sort of service, to provide more specialized
or constrained service. In addition, services may exist that will
provide more than one of these services, where that is deemed useful.
Each such service will reside in one or more administrative domains
and may be restricted or managed based on policies of those domains.
The list of core services is described below. Because there are many
interdependencies, there may often be forward references in
describing a service and its relationships to other services.
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* RESOURCE DISCOVERY: Much of the activity of resource discovery,
indexing and searching, will be in the domain of the retailers,
although there are supporting hooks that can be provided by the
wholesaler layer as well. A resource discovery service will hold
mappings from descriptions to identifiers of objects. They will need
to be queried. Thus there is a general functionality for a wholesale
layer service that answers queries formulated in certain ways and
responds with identifiers. The business of on what basis indices are
computed or how they are managed will be domain specific.
* NAMING or IDENTIFICATION: There are two aspects to assigning an
identifier to an object, one in the wholesale layer, and one,
arguably, in the retail layer. In the wholesale layer, one can
generate identifiers that are guaranteed to be unique. In the retail
layer one might ask the question about whether two objects are the
same or different by the rules of an identification authority that
therefore would determine whether they should bear the same or
different identification from that authority. It should be noted
that the URI Working Group has included these two functions in the
requirements document for URNs.
An identification service will obviously provide functionality to the
uniqueness authority. It will also provide identification in the
process of publication of objects, as will be discussed below, in the
management of resource discovery information, object location and
storage services, as well as cache and replication management.
* NAME or IDENTIFICATION RESOLUTION: Since identifiers are presumed
to be location independent, there is a need for a resolution service.
Such a service may sometimes return other identifiers at this same
level of abstraction (the equivalent of aliases) or location
information, the information delivered to a transport service to
access or retrieve an object.
* OBJECT RETRIEVAL: Object retrieval is tightly coupled to
resolution, because without resolution it cannot proceed. Object
retrieval provides the functionality of causing a representation of
an object to be provided locally to the requester of an object
retrieval. This may involve the functionality of object publication
(see below) and object storage, caching and replication services as
well as the supporting transport facilities.
* OBJECT PUBLICATION: When an object comes into existence in the
universe of the information infrastructure, it is said to be
"published." There will be two common scenarios in publication. One
will be the use of tools to directly enter and create the information
that comprises an object in the information infrastructure. Thus
there may be object creation tools visible to users in applications.
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In contrast there may also be tools outside the information
infrastructure (for example word processing or text editing tools)
that provide for the entry of data separately from the operation of
assigning an object an identifier and causing it to support
information infrastructure definitions of objects. Thus, there will
also be visible at the interface between the wholesale and retail
layers the ability to cause some pre-existing data to become one or
more objects. In addition to interacting with the identification
service, publication is likely to cause interaction with object
storage, and possibly caching and replication.
* DEFINITIONS: If the information infrastructure is to both survive
and evolve over a long time period, we must be prepared for a wide
variety and growing number of different sorts of information with
different functionalities that each supports. For objects available
on the net, the functionality that each provides must be exposed or
able to be learned. To do this objects must be able to indicate by
name or identifier the types of functionality they are supporting.
Given such an identifier, an object is only useful to a client, if
the client can discover the definition and perhaps a useful
implementation of the type in question. This will be acquired from a
definitions service, which will be used in conjunction with
applications themselves directly, object publication, and object
retrieval.
* ATTRIBUTE MANAGEMENT: The attributes considered here relate to
policy, although any understanding of that policy will be above the
wholesale level. There are, for example, access management and
copyright attributes. There is a question here about whether there
is or should be any access time enforcement or only after the fact
enforcement. The information is likely to be in the form of
attribute-value pairs and must be able to capture copyright knowledge
effectively.
* ACCOUNTING: An accounting service provides metering of the use of
resources. The resources wholly contained in the wholesale layer are
the services discussed here. It will also be important to provide
metering tools in the wholesale layer to be used by the retail layer
to meter usage or content access in that layer. Metering may be used
for a variety of purposes ranging from providing better utilization
or service from the resources to pricing and billing. Hence
accounting services will be used by object storage, caching and
replication, lower layer networking services, as well as pricing and
billing services. In the form of content metering it will also
interact with attribute management.
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* PRICING, BILLING and PAYMENT: Pricing and payment services straddle
two layers in the information infrastructure. Servers that maintain
account balances and with which users interact to retrieve and edit
account information are applications that will be built on top of
wholesale layer services. Pricing will be determined in the
applications environment for application level activities. However,
it must be possible for middle layer services to process payment
instruments analogous to cash, credit card slips, and checks, without
an understanding of the specific implementation of the payment
mechanism. Application programming interfaces supporting payment
should be provided, and a common tagged representation of payment
instruments should allow instruments from a variety of payment
systems to be presented within middle layer protocols.
* OBJECT STORAGE, CACHING and REPLICATION: There is a recognition
that caching and replication are important, but the discussion of
that was left to another group that had taken that as the focus of
their agenda. Object storage will take an object and put it
somewhere, while maintaining both the identity and nature of the
object. It is tightly coupled to caching and replication, as well as
accounting, often in order to determine patterns of caching and
replication. It is also tightly coupled to object publication,
translation, and provides interfaces to both supporting storage
facilities such as local file systems, as well as direct access from
applications, needing access to objects.
* TRANSLATION: A translation service allows an object to behave with
a nature different than that it would otherwise support. Thus, for
example, it might provide a WYSIWYG interface to an object whose
functionality might not otherwise support that, or it might generate
text on the fly from an audio stream. Translation services will be
used by object publication (allowing for identification of an object
including a translation of it) and with object storage, providing an
interface only within the wholesale or to the retail layers.
* SERVER AND SERVICE LOCATION: It will be necessary as part of the
infrastructure to be able to find services of the kinds described
here and the servers supporting them. This service has direct
contact with the lower layer of raw materials, in that it will
provide, in the final analysis, the addresses needed to actually
locate objects and services using lower level protocols, such as the
existing access protocols in use today, for example FTP, SMTP, HTTP,
or TCP. This service will provide functionality directly to resource
discovery as well as remote object storage services.
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* ADAPTIVE GLUE: This is not a single service as much as a
recognition that there must be a path for a flow of information
between the network layers and the applications. The application may
have constraints, based both on its own needs as well as needs of the
objects in the wholesale layer. Only the application can really know
what compromises in services provided below are acceptable to it. At
the same time, the supporting network layers understand what
qualities of service are available at what price. Hence there is the
potential for flow of information both up and down through the
wholesale layer, perhaps mediated by the wholesale layer. Hence the
adaptive glue has hooks into all three levels.
* SECURITY: Security services will be a critical piece of the
infrastructure architecture. For any real business to be conducted,
organizations must make their information available over the network,
yet they require the ability to control access to that information on
a per user and per object basis. To account properly for the use of
higher level services, organization must be able to identify and
authenticate their users accurately. Finally, payment services must
be based on security to prevent fraudulent charges, or disclosure of
compromising information.
The two biggest problems in providing security services at the
wholesale layer are poor infrastructure and multiple security
mechanisms that need to be individually integrated with applications.
The poor state of the infrastructure is the result of a lack of an
accepted certification hierarchy for authentication. A commonly held
position is that there will not be a single hierarchy, but there must
be established authorities whose assertions are widely accepted, who
indirectly certify the identities of individuals with which one has
not had prior contact.
Integration with applications is made difficult because, though
security services are themselves layered upon one another, such
services do not fit into the information architecture at a single
layer. By integrating security services with lower layers of the
information infrastructure, security can be provided to higher
layers, but some security information, such as client's identity, may
be needed at higher layers, so such support will not be completely
transparent. Further, the security requirements for each middle
layer information service, and of the application itself, must be
considered and appropriate use must be made of the middle-layer
security services applied.
Integration with applications will require user demand for security,
together with common interfaces such as the GSS-API, so that
applications and middle layer information services can utilize the
security services that are available, without understanding the
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details of the specific security mechanism that is employed.
* BOOTSTRAPPING: In order for a newly participating machine to join
the infrastructure, it must have some way of finding out about at
least one instance of many of the services described here. This can
be done either by providing it with some form of configuration
provided by the human bringing it up or by a bootstrapping service.
The bootstrapping service is more flexible and manageable; it is
included here in recognition that this information must be provided
in some form or other. The bootstrapping service will sit directly
on the raw materials layer and will have contact with all the
services described here.
This completes the description of the services as identified by this
group in the wholesale layer. Although this section suggests which
services have interfaces to the retail and raw materials layers, each
of these topics will need to be described separately as well, to
clarify the functionality expected by each layer of the layer below.
3. Interface to retail layer
The interface to the retail layer is the embodiment of the object
model and attendant services. Thus the interface provides the
application environment with a collection of objects having
identifiers for distinguishing them within the wholesale layer and
support for a typing or abstract functionality model. It provides
for the ability to create or import objects into this object world by
the publication paradigm, and allows objects to evolve to support new
or evolving functionality through the translation paradigm. Access
to the objects is provided by object storage, enhanced with caching
and replication services and mediated by the attributes managed by
attribute management and accounting or content metering. Discovery
of resources (figuring out which identifier to be chasing) is
provided by resource discovery services. Types are registered and
hence available both as definitions and perhaps in the form of
implementations from a definition service. Lastly, there is a
vertical model of providing the two-way services of adaptive glue for
quality of service negotiation and for security constraints and
requirements, with access and services at all three layers.
4. Interface to the raw materials layer
The raw materials layer falls into networking and operating systems.
Hence it provides all those services currently available from current
networking and operating systems. Wholesale services such as object
management will be dependent on local operating system support such
as a file system, as well as perhaps transport protocols. In fact,
all instances of any of the above services will be dependent on local
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storage, process management, local access control and other security
mechanisms, as well as general transport protocols for communications
both often among services of the same sort and among services
dependent on each other that may not be collocated. In addition the
group identified a set of issues that appear important for the
networking components of the raw materials layer to provide to the
wholesale layer in addition to the basic best effort transmission
services that are commonly available. These take the form of a wish
list with the recognition that they are not all equally easy or
possible.
* Connectivity: It is useful and important for the operation of
applications and the wholesale services to understand what
connectivity is currently available. The group identified four
categories of connectivity that it would be useful to know about
represented by four questions:
1) Is there a wire out of the back of my machine?
2) Am I connected to a router?
3) Am I connected to the global internet? (Can I get beyond
my own domain?)
4) Am I connected to a specific host?
These are probably in increasing difficulty of knowing.
* Connectivity forecast: Although this is recognized as either
extremely difficult or impossible to do, some form of connectivity
forecast would be very useful to the upper layers
* Bandwidth availability and reservation: It is useful for the
application to know both what bandwidth might be available to it and,
better yet, for it to be able to make some form of reservation.
* Latency availability and reservation: It is useful for the
application to know both what latency the network is experiencing
and, better yet, be able to set limits on it by means of a
reservation.
* Reliability availability and reservation: Again, reliability
constraints are important for many applications, although they may
have differing reliability constraints and may be able to adapt
differently to different circumstances. But, if the application
could make a statement (reservation) about what level of
unreliability it can tolerate, it might be able to make tradeoffs.
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* Burstiness support: Although it is unlikely that the network can
make predictions about the burstiness of its services, if the
application can predict to the network its burstiness behavior, the
network might be able to take advantage of that knowledge.
* Service envelope: It is possible that, as an alternative to the
above four issues, the raw materials layer could negotiate a whole
service envelope with the layers it is supporting.
* Security availability: In many cases, it will be important for the
upper layers to be able to know what sorts and levels of security are
available from the raw materials layer. This is true of both any
operating system support as well as transmission.
* Cost: If there is to be usage charging at other than fixed flat
rates, it will be important for applications and users to understand
what those costs or at least estimates of them will be.
* Policy routing: If it will be important for transport services to
support policy routing, it will be important for users of the
transport services to identify into which policy classes they might
fall.
4.5. Recommendations
This group has two categories of recommendations. One is those
services in the wholesale layer that will both be especially useful
and readily achieved because work is soon to be or already underway.
The other set of recommendations was a three item rank ordering of
services that are most important for the lower layer to provide to
the wholesale layer.
Within the wholesale layer, the first services that should be
provided are:
* Object retrieval,
* Name resolution,
* Caching and replication.
In addition, the group rank ordered three areas in which there would
be quick payoff if the raw materials layer could provide them. They
are:
1. Connectivity
2. Bandwidth, latency, and reliability or service envelope
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3. Security constraints on communication and transactions
5. Group 2B Report: Components of an Internet Information Architecture
Cecilia Preston, Chris Weider, Christian Huitema, Cliff Lynch, John
Romkey, Joyce Reynolds, Larry Masinter, Mitra, Jill Foster
Group 2B discussed various aspects of problems in the Internet
Information Infrastructure, thinking about recommendations to the
IESG to focus on particular areas, and also paying attention to some
of the philosophical and economic backgrounds to some of the
problems. Economics can dictate some points of architecture: one can
see economically why a publisher might bear the burden of the costs
of publishing, or a consumer might bear the burden of costs
associated with consumption, but not how some free-floating third
party would necessarily bear the costs of providing services (such as
third-party translators).
The group discussed the following topics:
access(URL)
gateways
URN resolution
definitions
updates
service location
cache & replication
security & authentication
payments, charging
presentation
search & index
metainformation
boot service
general computation
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5.1 URNs
There are several issues in the use of Uniform Resource Names and
Uniform Resource Locators. URN resolution is a database lookup that
returns the URLs associated with a URN. The architecture must take
into account not only how the lookup is performed, but how the
database is maintained. Both the lookup problem and the update
problem must be solved at the same time to allow deployment of URNs.
There are at least two problems in human interaction with unique
names. First, the notion of a unique name is a fallacy. Unique naming
cannot be enforced. Names may be forged or may simply be duplicated
due to human error. The architecture must accept this observation and
still operate in the face of it. Designing for global uniqueness, but
not requiring it, was adequate. Errors based on names not being
unique are likely to be insignificant compared to other errors.
Also, people frequently make assertions and assumptions about names
rather than the documents that are being named. Making assertions
about names is working at the wrong level of indirection. Making
assumptions about names, such as determining the contents of the
named object from the syntax of the name, can lead to nasty
surprises.
Having a single, unified naming system is vital. While it is healthy
to have multiple competing forms of other aspects of the information
architecture, the naming system is what ties it all together. There
must be only one naming system. If there is more than one, it may not
be possible to compare names or to lookup locations based on names,
and we will continue (to our detriment) to use locators rather than
names.
5.2 Global Service Location
The IANA has become the central switch point for service
identification. and recommended that numbers that are formally
defined and kept in documents for use in distributed information
systems (for instance, Assigned Numbers) should also be distributed
online in some kind of database for use by applications. This
distribution requires both an access method (perhaps multiple access
methods) and an update method.
5.3 Security
Issues involving security arose over and over again. Security
includes things like validation of authority, confidentiality,
integrity of data, integrity of services, access control. The group
agreed that, although often overlooked, confidentiality is important,
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and, more strongly: anonymity is important. It should be possible to
access documents or objects without the architecture requiring you to
leave digital fingerprints all over the place.
Security must occur on an end-to-end basis. Documents or objects used
on the Internet may not only traverse the Internet. Relying on
security mechanisms in the underlying protocol suite does not
necessarily provide end-to-end authentication or confidentiality.
Currently lower layer security is ill-defined and widely
unimplemented. Designers building information applications atop the
Internet currently receive little guidance in how to design security
features into their applications, leading to weak ad hoc or
nonexistent security in new applications. Designers are also unclear
as to how to deal with the "security considerations" section that is
mandatory in RFCs, and often fill them with boilerplate text.
Furthermore, retrofitting security into existing architectures does
not work well. The best systems are built considering security from
the very beginning. Some systems are being designed that, for
instance, have no place for a digital signature to authenticate the
data they pass. These issues apply to data management as well.
The group makes the following recommendations to the IESG regarding
security:
A. Develop and communicate a security model usable by designers of
information applications - current models are not considered usable.
B. RFC authors should be given advice on what security considerations
need to be outlined and how to write them. The IESG security area
should prepare guidelines for writing security considerations.
C. Proposed Standards should not be accepted by the IESG unless they
really consider security. This will require that recommendations A
and B have been implemented and that the guidelines have received
enough visibility to reasonably expect authors to know of their
existence.
D. Develop security modules usable by the implementors of information
clients and servers - reusable across many different, heterogeneous
applications and platforms.
E. Make clear what security services you can expect from the lower
layers.
F. Make sure that the key distribution infrastructure is reviewed for
usability by information applications.
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5.4 Search and Index
Searching is looking through directories that point to information.
Indexing is scanning information to create directories. A "unified
directory" is the result of combining several indices.
Indexing is currently done on the Internet via many mechanisms. Given
the current ad hoc nature of the indexing, information is frequently
indexed multiple times. This is wasteful, but due to the current
economics of the Internet, it tends not to cost more money. If the
Internet (or parts of thereof) transitions to usage based charging,
it may cost the information provider too much to allow the
information to be indexed. In general, the provider should have
control over how the information they control is indexed.
Above all, the architecture should not encourage a situation where
information is normally not indexed. It should encourage the
collection of indexing data only a single time. Having a local
computation of a summary which is sent to a search/index server is
vastly preferable to having that server "walk the net" to discover
information to index.
Indexing and search techniques are quite varied. It is quite likely
that index and search are too close to general computation to try to
standardize on a single protocol for either. Instead, it is important
that the architecture allow multiple search techniques. There are
currently certain types of indices that can only be generated by
humans because of their level of semantic content. There are large
differences in the quality and usability of indices that are
machine-generated vs. human generated.
Unified directories tend to combine indexing results from quite
different techniques. The architecture should constrain indexing so
that it remains possible to merge the results of two searches done by
different protocols or indexing systems. Returning information in
standard formats such as URNs can help this problem.
Vocabulary issues in search and index are very difficult. The library
and information services communities do not necessarily use
vocabulary that is consistent with the IETF community, which can lead
to difficult misunderstandings.
"Searching the Internet" is an inappropriate attempt to categorize
the information you're attempting to search. Instead, we search
certain public spaces on the Internet. The concept of public space
vs. private space on the Internet deserves further investigation.
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Indexing can run afoul of access control considerations. Access
control must be done at the object, but access control information
should be propagated through indices as well. The index should be
able to say "you're not allowed to ask that" rather than the user
attempting to retrieve the object and being denied.
An architectural point was raised that an index query should return
the same result independent of who is asking. This is an important
notion in the Domain Name System. This is inconsistent with some
real-world indexing (for instance, corporate record management
systems) which doesn't want to admit that some documents exist if
you're not allowed to read them.
5.5 Miscellaneous
Electronic mail, netnews, FTP and the web are frequently used to
access information on the net today. Each protocol seems to provide a
consistent view of the information on the Internet. In addition, the
recent popularity of multi-protocol clients such as Mosaic seem to
imply that the information content of the Internet is uniformly
retrievable and manageable. This perception is misleading because
most protocols are used for other applications than they were
originally designed for. In addition, Telnet, which has no concept of
information retrieval and management, is often used to access
information as well, for example in DIALOG and card file accesses.
Since each protocol has different access and management capabilities,
the inconsistencies show up in erratic search and retrieval results,
puzzling error messages, and a basic lack of standard techniques for
dealing with information. A consistent underlying information
architecture will go a long way towards alleviating these problems.
As the information architecture develops we should reconsider the
electronic mail and netnews architecture in terms of the new
architecture.
The group noted that there have been difficulties in scheduling joint
working group meetings and recommends that there be a clearly defined
process inside the IETF to facilitate scheduling such meetings.
6. Conclusions and Recommendations
The workshop provided an opportunity for ongoing conversations about
the architecture to continue and also provided space for focused
examination of some issues and for some new voices and experience
from other areas of Internet growth to participate in the
architectural process.
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Part of the conclusion of the workshop is a set of recommendations to
the IESG and IETF community.
Recommendations on research/implementation directions:
1. Caching and replication are important and overlooked pieces of
Internet middleware. We should do something about it as soon as
possible, perhaps by defining an architecture and service model for
common implementation.
2. Within the 'wholesale' layer, i.e. within the layer which provides
a consistent view of the information resources available on the
Internet, the first services that should be provided are:
* Object retrieval,
* Name resolution,
* Caching and replication.
3. There would be quick payoff if the raw materials layer, i.e. the
layer in which information resources are physically transmitted to
computers, could provide the following services:
* Connectivity
* Bandwidth, latency, and reliability or a service envelope
* Security constraints on communication and transactions
4. Develop security modules usable by the implementors of information
clients and servers - reusable across many different, heterogeneous
applications and platforms
Recommendations to the IESG, IETF, and IANA
1. Numbers that are formally defined and kept in documents in
distributed information systems (for instance, Assigned Numbers)
should be available in some kind of database for use by applications.
2. Develop and communicate a security model usable by designers of
information applications - current models are not considered usable
or are not widely accepted on the Internet.
3. RFC authors should be given advice on how security considerations
need to be written. The IESG security area should prepare guidelines
for writing security considerations.
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4. Proposed Standards should not be accepted by the IESG unless they
really consider security. This will require recommendations 2 and 3
to be implemented first.
5. Make clear what security services you can expect from the lower
layers.
6. Make sure that the key distribution infrastructure is reviewed for
usability by information applications.
7. There needs to be a process inside the IETF for scheduling a joint
meeting between two working groups - for example, so that the key
distribution WG can meet jointly with IIIR.
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APPENDIX A - Workshop Organization
The workshop was held at MCI's facility in Tyson Corners, Virginia.
The workshop organizers and attendees wish to thank MCI for the use
of their facilities to host the workshop.
All attendees met in joint session for the first half of October 12.
They then split into three groups. The first group considered the
"distributed database" problem which has arisen over and over again
in the design of parts of the Internet. The two other groups met to
consider a list of issues pertaining to the information
infrastructure. The groups ran independently until the morning of
October 14, when they met again in joint session.
The following people attended the workshop:
Abel Weinrib abel@bellcore.com
Barry Leiner BLeiner@ARPA.MIL
Cecilia Preston cpreston@info.berkeley.edu
Chris Weider clw@bunyip.com
Christian Huitema Christian.Huitema@SOPHIA.INRIA.FR
Cliff Lynch calur@uccmvsa.ucop.edu
Clifford Neuman bcn@isi.edu
Dan LaLiberte liberte@ncsa.uiuc.edu
Dave Sincoskie sincos@THUMPER.BELLCORE.COM
Elise Gerich epg@MERIT.EDU
Erik Huizer Erik.Huizer@SURFnet.nl
Jill Foster Jill.Foster@newcastle.ac.uk
John Curran jcurran@near.net
John Klensin klensin@infoods.mit.edu
John Romkey romkey@asylum.sf.ca.us
Joyce Reynolds jkrey@isi.edu
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Karen Sollins sollins@lcs.mit.edu
Larry Masinter masinter@parc.xerox.com
Lixia Zhang LIXIA@PARC.XEROX.COM
Mark McCahill mpm@boombox.micro.umn.edu
Michael Mealling Michael.Mealling@oit.gatech.edu
Mitchell Charity mcharity@lcs.mit.edu
Mike Schwartz schwartz@cs.colorado.edu
Mike St. Johns stjohns@DARPA.MIL
Mitra mitra@pandora.sf.ca.us
Paul Mockapetris pvm@zephyr.isi.edu
Steve Crocker Crocker@TIS.COM
Tim Berners-Lee tbl@info.cern.ch
Ton Verschuren Ton.Verschuren@surfnet.nl
Yakov Rekhter yakov@WATSON.IBM.COM
Security Considerations
This memo discusses certain aspects of security and the information
infrastructure. It contains general recommendations about security
enhancements required by information applications on the Internet.
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Authors' Addresses
Mark McCahill
University of Minnesota
room 190 Shepherd Labs
100 Union Street SE
Minneapolis, MN 55455
EMail: mpm@boombox.micro.umn.edu
John Romkey [Editor]
1770 Massachusetts Ave. #331
Cambridge, MA 02140
EMail: romkey@apocalypse.org
Michael F. Schwartz
Department of Computer Science
University of Colorado
Boulder, CO 80309-0430
EMail: schwartz@cs.colorado.edu
Karen Sollins
MIT Laboratory for Computer Science
545 Technology Square
Cambridge, MA 02139-1986
EMail: sollins@lcs.mit.edu
Ton Verschuren
SURFNet
P.O. Box 19035
3501 DA Utrecht
The Netherlands
EMail: Ton.Verschuren@surfnet.nl
Chris Weider
Bunyip Information Systems
310 St. Catherine St. West
Suite 300
Montreal, PQ H2A 2X1
CANADA
EMail: clw@bunyip.com
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