WDIFF

draft-aboba-acct-00.txt --> draft-aboba-acct-01.txt

INTERNET-DRAFT Microsoft Corporation
Category: Informational Jari Arkko
<draft-aboba-acct-00.txt>
<draft-aboba-acct-01.txt> Ericsson
6 August 1998
8 June 1999

Introduction to Accounting Management

1. Status of this Memo

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The distribution of this memo is unlimited. It is filed as <draft-
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2. Copyright Notice

3. Abstract

The field of Accounting Management is concerned with the collection of
resource consumption data for the purposes of capacity and trend anal-
ysis,
analysis, cost allocation, auditing, and billing. This document
describes
the problems encountered in Accounting Management, as well as some each of these problems, and discusses the issues encountered involved in the
design of modern accounting systems. It also
reviews the state of current practice.

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3. Accounting Management 8 June 1999

Since accounting applications do not have uniform security and
reliability requirements, it is not possible to devise a single
accounting protocol and set of security services that will meet all
needs. Thus the goal of accounting management is to provide a set of
tools that can be used to meet the requirements of each application.
This document describes the currently available tools as well as the
state of the art in accounting protocol design. A companion document,
draft-brownlee-accounting-attributes-00.txt, reviews the state of the
art in accounting attributes and record formats.

4. Table of Contents

1. Status of this Memo
2. Abstract Copyright notice
3. Abstract
4. Table of Contents
4.
5. Introduction
4.1
5.1 Terminology
4.2
5.2 Accounting management architecture
4.3
5.3 Accounting management objectives
4.4
5.4 Intra-domain and inter-domain accounting
5.
5.5 Requirements summary
6. Scaling and reliability properties of accounting systems
5.1 Resource consumption
5.2
6.1 Fault resilience
5.3
6.2 Resource consumption
6.3 Data collection models
6.
7. Review of current practice
6.1 existing accounting protocols
7.1 Accounting protocols
6.2
7.2 Accounting data transfer protocols
7. Acknowledgements
8. References Security issues
9. Acknowledgements
10. References
11. Authors' Addresses
12. Copyright Statement
13. Expiration date

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4. Accounting Management 8 June 1999

5. Introduction

The field of Accounting Management is concerned with the collection of
resource consumption data for the purposes of capacity and trend anal-
ysis,
analysis, cost allocation, auditing, and billing. This document
describes each of these problems, and discusses the issues involved in
design of modern accounting systems.

4.1. Terminology

This document frequently uses the following terms:

Accounting
The act

Since accounting applications do not have uniform security and
reliability requirements, it is not possible to devise a single
accounting protocol and set of collecting information on resource usage for security services that will meet all
needs. Thus the
purpose of trend analysis, auditing, billing, or cost allo-
cation.

Rating The act goal of determining the price accounting management is to be charged for use of provide a
resource. set of
tools that can be used to meet the requirements of each application.
This document describes the currently available tools as well as the
state of the art in accounting protocol design. A companion document,
draft-brownlee-accounting-attributes-00.txt, reviews the state of the
art in accounting attributes and record formats.

5.1. Terminology

This document frequently uses the following terms:

Accounting
The collection of resource consumption data for the purposes
of capacity and trend analysis, cost allocation, auditing, and
billing. Accounting management requires that resource
consumption be measured, rated, assigned, and communicated
between appropriate parties.

Archival accounting
In archival accounting, the goal is to collect all accounting
data, to reconstruct missing entries as best as possible in
the event of data loss, and to archive data for a mandated
time period. Legal or financial requirements frequently
mandate archival accounting practices, and may often dictate
that data be kept confidential, regardless of whether it is to
be used for billing purposes or not.

Rating The act of determining the price to be charged for use of a
resource.

Billing The act of preparing an invoice.

Usage sensitive billing
A billing process that depends on usage information to prepare
an invoice can be said to be usage-sensitive. In contrast, a
process that is independent of usage information is said to be

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non-usage-sensitive.

Auditing The act of verifying the correctness of a procedure.

Cost Allocation
The act of allocating costs between entities. Note that cost
allocation and rating are fundamentally different processes.
In cost allocation the objective is typically to allocate a
known cost among several entities. In rating the objective is
to determine the amount owed. In cost allocation, the cost per
unit of resource may need to be determined; in rating, this is
typically a given.

Interim accounting
An interim accounting packet provides a snapshot of usage
during a user's session. It is typically implemented in order
to provide for partial accounting of a user's session in the
event of a device reboot or other network problem that
prevents the reception of a session summary packet or session
record.

Session record
A session record represents a summary of the resource con-
sumption
consumption of a user over the entire session. Accounting gate-
ways
gateways creating the session record may do so by processing
interim accounting events. events or accounting events from several
devices serving the same user.

Accounting Protocol
A protocol used to convey data for accounting purposes.

Intra-domain accounting
Intra-domain accounting involves the collection of informa-
tion information
on resource within an administrative domain, for use within
that domain. In intra-domain accounting, accounting packets
and session records typically do not cross adminis-
trative administrative
boundaries.

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Inter-domain accounting
Inter-domain accounting involves the collection of informa-
tion information
on resource usage of an entity with an administrative domain,
for use within another administrative domain. In inter-domain
accounting, accounting packets and session records will
typically cross administrative boundaries.

Real-time accounting
Real-time accounting involves the processing of information on
resource usage within a defined time window. Time con-
straints are typically imposed in order to constraints

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are typically imposed in order to limit financial risk.

Accounting server
The accounting server receives accounting data from devices
and translates it into session records. The accounting server
may also take responsibility for the routing of ses-
sion session
records to interested parties.

4.2.

5.2. Accounting management architecture

Accounting management requires that accounting metrics be measured,
rated, assigned, and communicated between appropriate parties.

The accounting management architecture involves interactions between
network devices, accounting servers, and billing servers. The network
device collects resource consumption data in the form of accounting
metrics. This information is then transferred to an accounting server.
Typically this is accomplished via an accounting protocol, although it
is also possible for devices to generate session records.

The accounting server then processes the accounting data received from
the network device. This processing may include summarization of interim
accounting information, elimination of duplicate data, or gen-
eration generation of
session records.

The processed accounting data is then submitted to a billing server,
which typically handles rating and invoice generation, but may also
carry out auditing, cost allocation, trend analysis or capacity plan-
ning planning
functions. Session records may be batched and compressed by the
accounting server prior to submission to the billing server in order to
reduce the volume of accounting data and the bandwidth required to
accomplish the transfer.

One of the functions of the accounting server is to distinguish between
the inter and intra-domain accounting events and to route them
appropriately. Intra-domain accounting events are typically routed to
the local billing server, while inter-domain accounting events will be
routed to accounting servers operating within other administrative
domains. While it is not required that session record formats used in
inter and intra-domain accounting transfers be the same, this such rationalization is
highly
desirable, since this it eliminates translations that would other-
wise otherwise be
required.

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The diagram below illustrates a typical the accounting management architecture:

4.3.

5.3. Accounting management objectives

Accounting Management involves the collection of resource consumption
data for the purposes of capacity and trend analysis, cost allocation,
auditing, and billing. Since each of these tasks have different relia-
bility and security
requirements, it is worthwhile to we will discuss each task in detail.

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4.3.1.

5.3.1. Trend analysis and capacity planning

In trend analysis and capacity planning, the goal is typically a fore-
cast
forecast of future usage. Since such forecasts are inherently

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imperfect,
absolute high reliability in accounting data collection is typically not
required. As a result required, and moderate data
loss can typically be tolerated
in such an application. tolerated.

In certain cases, it may be desirable to use statistical sampling
techniques to reduce data collection requirements while still provid-
ing providing
the forecast with the desired statistical accuracy. Such a sam-
pling sampling
process may be insensitive even to large amounts of packet loss as long
as bias is not introduced.

The security requirements for trend analysis and capacity planning
depend on the circumstances of data collection and the sensitivity of
the data. Generally, additional Additional security services may be required when data is
being transferred between administrative domains. For example, when
information is being collected and analyzed within the same
administrative domain, integrity protection and authentication may be
used in order to guard against collection of invalid data. In
inter-domain inter-
domain applications confidentiality it may be desirable to add
confidentiality, to guard against
snooping by third parties.

4.3.2.

5.3.2. Billing

When accounting data is used for billing purposes, the requirements
differ based
depend on whether the billing process requires information on
usage. A is usage-sensitive or not.

5.3.2.1. Non-usage sensitive billing process that does not require usage information to
prepare an invoice can be said to be non-usage-sensitive.

Since by definition, non-usage-sensitive billing does not require usage
information, in theory all accounting data can be lost without affecting
the billing process. Of course wholesale data loss will affect other
tasks such as trend analysis or auditing, so that this would still cause
problems.

5.3.2.2. Usage-sensitive billing

Since usage-sensitive billing processes depend on usage information,
packet loss may translate directly to revenue loss. As a result, the
billing process may need to meet requirements arising from financial
reporting standards, or legal requirements, and therefore an archival
accounting approach may be required. In archival accounting, the goal is to col-
lect all accounting data, to reconstruct missing entries as best as
possible in the event of data loss, and to archive data for a mandated
time period, which is typically seven years.

Usage-sensitive systems may also have additional requirements relating
to processing delay. Today credit risk is commonly managed by comput-
erized
computerized fraud detection systems that are designed to detect unusual
activity. While transfer efficiency concerns might otherwise dictate batched
transmission of accounting data, where it is desirable to min-
imize minimize

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financial risk, a different approach may be required.

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Since financial exposure increases with processing delay, it may be
necessary to transmit each event individually or to minimize batch size,
to require positive acknowledgment before providing service, or even to
utilize quality of service techniques to minimize queuing delays.

The degree of financial exposure is application-dependent. For dialup
Internet access from a local provider, charges are low and therefore the
risk of loss is small. However, in the case of dialup roaming or voice
over IP, time-based charges may be substantial and therefore the risk of
fraud is larger. In such situations it is highly desirable to quickly
detect unusual account activity, and it may be desirable for
authentication
authorization to depend on ability to pay. In situations where valu-
able valuable
resources can be reserved, or where charges can be high, very large
bills may be rung up quickly, and therefore real-time processing may be
required.

In usage-sensitive systems, accounting data may result in monetary
transfers, and as a result, the security and reliability requirements
are greater. Thus security services such as authentication and integrity
protection are frequently used, and confidentiality and non-
repudiation non-repudiation
may also be desirable.

4.3.3.

5.3.3. Auditing

With enterprise networking expenditures on the rise, interest in
auditing is increasing. Auditing, which is the act of verifying the
correctness of a procedure, commonly relies on accounting data. Audit-
ing Auditing
tasks include verifying correctness of an invoice submitted by a service
provider, or verification that usage is conforming to usage policy,
service level agreements, or security guidelines.

To permit a credible audit, the accounting data collection methods put
in place must be at least as reliable as those used by the invoicing
service provider. Similarly, security policies involved in auditing of
an invoice should be at least as stringent as those used in preparation
of the origi-
nal calculation. original invoice. Due to financial and legal requirements,
archival accounting practices are frequently required in this
application.

Where auditing procedures are used to verify conformance to usage or
security policies, security services may be desired. This typically will
include integrity protection and authentication of accounting data, as
well as confidentiality and possibly data object security. In order to
permit response to security incidents in progress, auditing applications
frequently are built to operate with low processing delay.

4.3.4.

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5.3.4. Cost allocation

The application of cost allocation and billback methods by enterprise
customers is not yet widespread. However, with the convergence of
telephony and data communications, there is increasing interest in
applying cost allocation and billback procedures to networking costs,

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is now commonly practiced with telecommunications costs.

Cost allocation models, including traditional costing mechanisms
described in [27]-[29] [21]-[23] and activity-based costing techniques described
in [30] [24] are typically based on detailed analysis of usage data, and as a
result they are almost always usage-sensitive. Whether cost alloca-
tion allocation
models are applied to allocation of costs between partners in a venture
or to allocation of costs between departments in a single firm, cost
allocation models often have profound behavioral and finan-
cial financial impacts.
As a result, systems developed for this purposes are typically as
concerned with reliable data collection and security as are billing
applications.

4.4. Due to financial and legal requirements, archival
accounting practices are frequently required in this application.

5.4. Intra-domain and inter-domain accounting

Much of the early work on accounting management focused on intra-
domain intra-domain
accounting applications. However, with the increasing deploy-
ment deployment of
services such as dialup roaming, Internet fax, Internet tele-
phony telephony and
QoS, applications requiring inter-domain accounting are becoming
increasingly common.

Intra-domain

Inter-domain accounting differs from intra-domain accounting in sev-
eral several
important ways. Intra-domain accounting involves the collection of
information on resource consumption within an administrative domain, for
use within that domain. In intra-domain accounting, accounting packets
and session records typically do not cross adminis-
trative administrative boundaries. As
a result, intra-domain accounting applications typically experience low
rates of packet loss. loss and involve transfer of data between trusted
entities.

In contrast, inter-domain accounting involves the collection of infor-
mation
information on resource consumption within an administrative domain, for
use within another administrative domain. In inter-domain accounting,
accounting packets and session records will typically cross adminis-
trative
administrative boundaries. As a result, inter-domain accounting
applications may experience substantial packet loss. In addition, the
entitities involved in the transfers cannot be assumed to trust each
other.

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Since inter-domain accounting applications involve transfers of
accounting data between domains, additional security measures may be
desirable. In addition to authentication and integrity protection, it
may be desirable to deploy security services such as confidentiality,
replay protection protection, data object integrity, or non-repudiation. In inter-domain inter-
domain accounting each involved party also typically requires a copy of
each accounting event for invoice generation and auditing.

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5.5. Requirements summary

Key
[] = optional

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6. Scaling and reliability characteristics of accounting systems

With the continuing growth of the Internet, it is important that
accounting management systems be scalable and reliable. This section
discusses the resources consumed by accounting management systems as
well as the scalability and reliability properties exhibited by vari-
ous various
data collection models.

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5.1. Resource consumption

In the process of growing

6.1. Fault resilience

As noted earlier, in applications such as usage-sensitive billing, cost
allocation and auditing, an archival approach to meet the needs of providers accounting is
frequently mandated, due to financial and cus-
tomers, legal requirements. Since in
such situations loss of accounting management systems consume data can translate directly into
revenue loss, financial incentives exist to engineer a variety high degree of resources,
including:
fault resilience. Faults which may be encountered include:

Packet loss
Accounting server failures
Network bandwidth
Memory/non-volatile storage on managed devices
State on failures
Device reboots

To date, much of the debate on accounting management system
CPU reliability has focussed on
resilience against packet loss and the management system differences between UDP and managed devices

In order to understand TCP-
based transport. However, it should be understood that resilience
against packet loss is only one aspect of the limits program required to scaling of meet
archival accounting management
systems, we examine each of these resources in turn.

5.1.1. Network bandwidth

Accounting management systems consume network bandwidth requirements.

As noted in [43], "once the trans-
ferring of accounting data. The network bandwidth consumed cable is propor-
tional to cut you don't need more
retransmissions, you need a *lot* nore voltage." Thus, the amount choice of data transferred, as well
UDP or TCP transport has no impact on resilience against faults such as required
network
overhead. Since partition, accounting data for a given event may be 100 octets server failures or less, if each event device reboots. What
does provide resilience against these faults is transferred individually, network overhead
can represent a considerable proportion non-volatile storage.

The importance of total bandwidth consump-
tion. As a result, it is often desirable to transfer accounting data non-volatile storage in batches, enabling network overhead to be spread over a larger pay-
load, and enabling efficient use design of compression.

5.1.2. Memory/non-volatile storage on managed devices

In reliable accounting
systems without non-volatile memory, accounting data
must cannot be stored in the period between when it is generated and when it
is transferred. The resulting memory consumption will depend on retry
and retransmission algorithms. Since over-emphasized. Without such storage, event-driven
systems designed for high relia-
bility will typically wish to retry for long periods, the resulting
memory consumption can be considerable.

Since accounting lose data stored in memory once the transmission timeout has been exceeded,
and polling or event-driven batching designs will typically be lost in experience data loss
once the internal memory used for event of a device reboot, or a timeout, storage has been exceeded.

Thus, it may be desirable to provide
non-volatile storage for undelivered accounting data. With the costs
of flash RAM declining rapidly, it is likely plausibly argued that network devices will
be capable of incorporating non-volatile storage within the next few
years.

5.1.3. State on the accounting management system

In order is more
important to keep track of received accounting data, reliability than network connectivity, since for
many years reliable accounting manage-
ment systems may need were implemented based solely on
physical storage, without any network connectivity. For example, phone
usage data used to keep state be stored on managed devices paper, film, or concurrent
sessions. Since the number of devices is typically much smaller than magnetic media and
carried from the number place of concurrent sessions, it is desirable collection to keep only per-
device state if possible. a central location for bill
processing.

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5.1.4. CPU requirements

CPU consumption Accounting Management 8 June 1999

6.1.1. Interim accounting

Interim accounting provides protection against loss of the managed and managing nodes will session summary
data by providing checkpoint information that can be proportional used to reconstruct
the complexity of session record in the required accounting processing. Operations
such as ASN.1 encoding and decoding, compression/decompression, event that the session summary information is
lost. This technique may be applied to any data collection model (i.e.
event-driven or polling) and
encryption/decryption can consume considerable resources, is supported in both on
accounting clients RADIUS [25] and servers.

The effect of these operations on accounting system reliability should
not be under-estimated, particularly in the case of devices with mod-
erate CPU resources. In the event that devices are over-taxed by
TACACS+ [26].

While interim accounting tasks, it is likely that overall device reliability will
suffer.

5.2. Fault can provide resilience

Given the potential importance of accounting data, it is highly desir-
able for accounting systems to be resilient against a variety of
faults, including:

Packet loss
Accounting packet loss,
server failures
Network failures
Device reboots

This section discusses each of these failure modes in turn.

5.2.1. Packet loss

As failures, short-duration network failures, or device reboot, its
applicability is limited. Since most packet loss is a fact of life on the Internet, accounting protocols
need to be resilient against such losses. Typically this Internet is accom-
plished either via implementation of a retry mechanism on top of UDP,
or use of TCP.

5.2.2. Accounting server failures

In the event of an accounting server failure, it may not be possible
for a device due
to transmit congestion, sending interim accounting data to its primary accounting
server. For protocols using TCP, opening of a connection to over the sec-
ondary accounting server wire can occur after
actually make the problem worse by increasing bandwidth usage. As a timeout or
result, on-the-wire interim accounting is best restricted to use with
high-value accounting data such as information on long-lived sessions.
To protect against loss of the pri-
mary connection, or it can occur data on expiration of a timer. For proto-
cols using UDP, transmission to such sessions, the secondary server can occur after a
number of retries or timer expiration. In either case, it interim reporting
interval is possible
for the primary and secondary accounting servers to receive typically set several standard deviations larger than the same
record, so
average session duration. This ensures that elimination of duplicates is required.

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5.2.3. Network failures

Network failures may most sessions will not
result in partial or complete loss generation of connectiv-
ity for the interim accounting client. In events and the event of partial connectivity
loss, it may not additional
bandwidth consumed by interim accounting will be possible to reach moderate.

However, as the primary interim accounting server,
in which case switchover to interval decreases toward the secondary the
average session time, the additional bandwidth consumed by interim
accounting server increases markedly, and as a result, the interval must be set
with caution. This practice is neces-
sary. In particularly suspect since it increases
use of network bandwidth in normal operation, while providing benefits
only in the event of a network partition, it may be necessary to
store accounting events in device memory or fault.

Where non-volatile storage until
connectivity is unavailable, interim accounting can be re-established.

The importance also
result in excessive consumption of non-volatile memory that could be better allocated
to storage in design of reliable account-
ing systems session data. As a result, implementors should not be under-estimated. Without such storage,
event-driven systems will lose careful
to ensure that new interim accounting data once the transmission timeout has
been exceeded, and polling or event-driven batching designs will expe-
rience overwrites previous data loss once
rather than accumulating additional interim records thereby worsening
the internal memory used for event storage has
been exceeded. As a result, network access is not by itself a guaran-
tee buffer exhaustion problem.

Given the decreasing cost of reliable data transfer, and for many years reliable accounting
systems were implemented based solely on physical storage, without any
need for network access. For example, phone usage data used to non-volatile memory, it may be
stored on paper, film, or magnetic media and carried from the place of
collection preferable
to a central location for bill processing.

5.2.4. Device reboots

In store interim accounting data in non-volatile storage. Stored interim
events are then replaced by session data when the event of a device reboot, it is desirable to minimize session completes, and
the loss
of session data on sessions in progress. This can itself be accomplished via interim
accounting, with erased once the data has been
transmitted. This approach avoids interim accounting data being transferred transmitted over
the network or kpt in non-volatile storage.

5.3. Data collection models

Several data collection models are currently wire, except in use today for the pur-
poses case of accounting data collection. These include:

Polling model
Event-driven model
Event-driven polling model
Interim accounting

5.3.1. Polling model

In the polling model, an accounting manager will poll devices for
accounting information at regular intervals. In order to ensure
against a device reboot.

6.1.2. Packet loss

As packet loss is a fact of data, life on the polling interval will Internet, accounting protocols
need to be shorter
than the maximum time that accounting data can be stored on the polled
device. For devices without non-volatile strage, this is typically
determined by available memory; for devices with non-volatile storage
the maximum polling interval resilient against such losses. This is determined by the size of non-volatile
storage. particularly important

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The polling model results Accounting Management 8 June 1999

in an accumulation of data within individual
devices, and as inter-domain accounting, where packets often pass through Network
Access Points (NAPs) where packet loss may be substantial. Resilience
against packet loss can be accomplished via implementation of a result, data is typically transferred to the retry
mechanism on top of UDP, or use of TCP. On-the-wire interim accounting manager
provides only limited benefits in mitigating the effects of packet loss.

When implementing UDP retransmission, there are a batch, resulting number of issues to
keep in an efficient transfer pro-
cess. mind:

Retry behavior
Congestion control
Timeout behavior

In terms of Accounting Manager state, polling systems scale with designing a UDP retry mechanism, it is important that the number of managed devices, and system retry
timers relate to the round-trip time, so that retransmissions will not
typically occur within the period in which acknowledgements may be
expected to arrive. Accounting bandwidth usage scales with may be significant in some
circumstances, so that the amount of added traffic due to unnecessary
retransmissions may increase congestion levels.

Congestion control in accounting data transferred.

Without transfer is a somewhat
controversial issue. Since accounting traffic is often considered
mission-critical, it has been argued that congestion control is not a
requirement; better to let other less-critical traffic back off in
response to congestion. Moreover, without non-volatile storage, the polling model results
congestive backoff in loss of accounting applications can result in data loss
due to device reboots, but buffer exhaustion.

However, there are very persuasive arguments that in modern accounting
implementations, it is possible to implement congestion control while
improving throughput and maintaining high reliability.

In circumstances where there is sustained packet loss, there simply is
not sufficient capacity to maintain existing transmission rates. Thus,
aggregate throughput will actually improve if congestive backoff is
implemented. This is due to packet loss or
network failures elimination of sufficiently short duration retransmissions and ability
to be handled within
available memory. utilize techniques such as RED to desynchronize flows. In situations where operational difficulties are
encountered, the volume of addition,
with QoS mechanisms such as differentiated services, it is possible to
mark accounting data will frequently increase packets for preferential handling so as to make data provide for
lower packet loss more likely. However, in this case the polling
model will detect if desired. Thus such choices need not be hard coded
within the problem since attempts application, but can be left to reach the managed
devices will fail.

Per-device state is typical of polling-based network management sys-
tems, which administrator.
Furthermore, systems implementing non-volatile storage allow for
backlogged accounting data to be placed in permanent storage pending
transmission so that buffer exhaustion resulting from congestive backoff
is not a concern.

Since UDP is not really a transport protocol, UDP-based accounting
protocols such as [4] often also carry out do not prescribe timeout behavior. Thus one

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implementation may throw the accounting management functions,
since network management systems need data away after 3 constant
duration retries to keep track the same server, while another may implement
exponential backoff to a given server, then switch to another server, up
to a total timeout interval of 12 hours, while storing the state untransmitted
data on non-volatile storage. The difference between these behaviors may
be of
network devices for operational purposes.

5.3.2. Event-driven model

In intense concern, since the event-driven model, a device former approach will contact not satisfy
archival accounting requirements while the latter may.

6.1.3. Accounting server failures

In the event of an accounting server
or manager when failure, it is ready may not be possible for
a device to transfer accounting data. Most event-
driven transmit accounting systems are based on RADIUS accounting, described in
[4], and transfer only one data to its primary accounting event per packet, which is inef-
ficient.

Without non-volatile storage, server.
For protocols using TCP, opening of a pure event-driven model only stores
individual connection to the secondary
accounting events that have not yet been delivered and as server can occur after a
result it has the smallest memory requirements of any timeout or loss of the models.
However, the event-driven model is also primary
connection, or it can occur on expiration of a timer. For protocols
using UDP, transmission to the least reliable, since secondary server can occur after a number
of retries or timer expiration. In either case, it is possible for the
primary and secondary accounting servers to receive the same record, so
that elimination of duplicates is required.

Since accounting server failures can result in data accumulation on
accounting clients, use of non-volatile storage can ensure against the
loss will occur of such data due to device reboots, sustained
packet loss, transmission timeouts or network buffer exhaustion.

On-the-wire interim accounting provides only limited benefits in
mitigating the effects of accounting server failures.

6.1.4. Network failures

Network failures may result in partial or complete loss of duration greater than connectivity
for the timeout
interval. Since accounting servers will client. In the event of partial connectivity loss, it
may not receive events if opera-
tional difficulties are encountered, event-driven be possible to reach the primary accounting systems
are not very useful server, in monitoring of device health.

Per-session state which
case switchover to the secondary accounting server is typical necessary. In the
event of event-driven systems without batching,
and as a result, a pure event-driven approach is to network partition, it may be avoided wher-
ever possible.

5.3.3. Event-driven polling model

In the event-driven polling model an necessary to store accounting manager will poll the
events in device for memory or non-volatile storage until connectivity can
be re-established.

As with accounting data server failures, on-the-wire interim accounting
provides only when it receives an event. The limited benefits in mitigating the effects of network
failures.

6.1.5. Device reboots

In the event
can occur at regular time intervals, or when a batch of a given size
has been gathered or both. Note that while transfer efficiency will
increase with batch size, without non-volatile storage, device reboot, it is desirable to minimize the potential
data loss from a device reboot will also increase. of
data on sessions in progress. Such losses may be significant even if the

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Without non-volatile storage, an event-driven polling model will lose
data due to device reboots, but not Accounting Management 8 June 1999

devices themselves are very reliable, due to sustained packet loss, or
network partitions of short-duration. Unless a minimum delivery
interval is set, event-driven polling systems are not useful in moni-
toring of device health.

Where batching can be implemented the state required in event-driven
polling long-lived sessions, which
can be reduced to scale with the number of active devices. If
portions of the network vary widely in usage, then this state may
actually be less than that comprise a significant fraction of the polling approach.

5.3.4. Interim accounting

Interim total resource consumption.
Sending interim accounting is in use both in RADIUS [31] and in TACACS+ [32].
It data over the wire is typically implemented
to improve accounting system reliability
and may be applied to either event-driven or polling systems. While guard against loss of these high-value sessions. When interim
accounting can in theory be used is combined with non-volatile storage it becomes possible to limit
guard against data loss due to
packet loss, short-duration network failures, or device reboot, its
applicability in much shorter sessions. This is limited possible since
interim accounting data need only be stored in non-volatile memory until
the session completes, at which time the interim data may be replaced by bandwidth consumption concerns.
the session record. As a result, interim accounting data need never be
sent over the wire, and it is most typically implemented in order possible to
avoid loss of long-duration sessions, and decrease the interim interval is typ-
ically set larger than
so as to provide a very high degree of protection against data loss.

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6.1.6. Fault resilience summary

Key
* = limited usefulness without non-volatile storage

6.2. Resource consumption

In the average session duration.This ensures that
most sessions will not result in generation process of interim accounting
events and growing to meet the additional bandwidth consumed by interim needs of providers and customers,
accounting
will be moderate.

However, as management systems consume a variety of resources, including:

Network bandwidth
Memory
Non-volatile storage
State on the interim accounting interval decreases toward the the
average session time, management system
CPU on the additional bandwidth consumed by interim
accounting increases markedly, management system and as a result, managed devices

In order to understand the interval must be
set with caution. This practice is particularly suspect since it
increases use limits to scaling of accounting management
systems, we examine each of these resources in turn.

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6.2.1. Network bandwidth

Accounting management systems consume network bandwidth in normal operation, while provid-
ing benefits only in the event
transferring of a fault. ,LP Given accounting data. The network bandwidth consumed is
proportional to the decreasing
cost amount of non-volatile memory, it data transferred, as well as required
network overhead. Since accounting data for a given event may be preferable 100
octets or less, if each event is transferred individually, overhead can
represent a considerable proportion of total bandwidth consumption. As
a result, it is often desirable to store interim transfer accounting data in batches,
enabling network overhead to be spread over a larger payload, and
enabling efficient use of compression.

6.2.2. Memory

In accounting systems without non-volatile storage. Stored interim events are
then replaced by session storage, accounting data when must
be stored in volatile memory during the session completes, period between when it is
generated and when it is transferred. The resulting memory consumption
will depend on retry and retransmission algorithms. Since systems
designed for high reliability will typically wish to retry for long
periods, or may store interim accounting data, the ses-
sion data resulting memory
consumption can itself be erased once the considerable. As a result, if non-volatile storage is
unavailable, it may be desirable to compress accounting data has been transmitted.
This approach avoids awaiting
transmission.

As noted earlier, implementors of interim accounting should take care to
ensure against excessive memory usage by overwriting older interim
accounting data being transmitted over with newer data for the wire,
except same session rather than
accumulating interim data in the case buffer.

6.2.3. Non-volatile storage

Since accounting data stored in memory will typically be lost in the
event of a device reboot.

6. Review reboot or a timeout, it may be desirable to provide
non-volatile storage for undelivered accounting data. With the costs of current practice

Accounting systems have been successfully impelemented using protocols
such as RADIUS, TACACS+, SYSLOG and SNMP. This section describes
flash RAM declining rapidly, it is likely that network devices will be
capable of incorporating non-volatile storage within the
characteristics next few years.

As described in [11], non-volatile storage may be used to store interim
or session records in a standard ASCII format. As with memory
utilization, interim accounting overwrite is desirable so as to prevent
excessive storage consumption. Note that the use of each ASCII data
representation enables use of these protocols, as well as transfer proto-
cols such highly efficient text compression
algorithms that can minimize storage requirements. Such compression
algorithms are only typically applied to session records so as HTTP, FTP, and SMTP.

6.1. Accounting protocols to enable
implementation of interim data overwrite.

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6.1.1. RADIUS

RADIUS accounting, described in [4], was developed as an add-on to Accounting Management 8 June 1999

6.2.4. State on the
RADIUS authentication protocol, described in [3]. As a result, RADIUS accounting shares the event-driven approach management system

In order to keep track of RADIUS authentication,
without support for batching received accounting data, accounting
management systems may need to keep state on managed devices or polling. As a result, RADIUS account-
ing scales with
concurrent sessions. Since the number of accounting events instead of devices is typically much
smaller than the number of devices, concurrent sessions, it is desirable to keep
only per-device state if possible.

6.2.5. CPU requirements

CPU consumption of the managed and managing nodes will be proportional
to the complexity of the required accounting transfers are inefficient. In addition,
since RADIUS accounting is based on UDP processing. Operations such
as ASN.1 encoding and timeout decoding, compression/decompression, and retry parame-
ters are
encryption/decryption can consume considerable resources, both on
accounting clients and servers.

The effect of these operations on accounting system reliability should
not specified, implementations vary widely in their approach
to reliability, with some implementations retrying until delivery or
buffer depletion, and others losing accounting data after a few
retries.

As a result, many RADIUS accounting implementations are sensitive to
packet loss or short-lived network partitions, and such deficiencies
are magnified further when RADIUS accounting is applied in inter-
domain accounting as is required in roaming, as noted be under-estimated, particularly in [1]. On the
other hand, the event-driven approach case of RADIUS devices with
moderate CPU resources. In the event that devices are over-taxed by
accounting tasks, it is well
suited to handling of likely that overall device reliability will
suffer.

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6.2.6. Efficiency measures

6.3. Data collection models

Several data object secu-
rity services are not supported, and thus systems based on RADIUS
accounting collection models are not capable of being deployed with untrusted proxies,
as noted in [2].

While currently in principle extensible with use today for the definition
purposes of new attributes,
RADIUS suffers from the very small standard attribute space (256
attributes).

6.1.2. TACACS+

TACACS+ as defined in [32] offers an accounting data collection. These include:

Polling model with start,
stop, and interim update messages. Since TACACS+ is based on TCP,
implementations are typically resilient against packet loss and short-
lived network partitions. However, given
Event-driven model
Event-driven polling model

6.3.1. Polling model

In the tradeoff between relia-
bility and delay, TACACS+ accounting is less suited to handling of polling model, an accounting events which require low processing delay.

TACACS+ provides manager will poll devices for hop-by-hop authentication and integrity protec-
tion as well as hop-by-hop confidentiality. Data object security is
not supported, and therefore systems based on TACACS+ accounting are
not deployable in the presence of untrusted proxies.

6.1.3. SNMP

SNMP-based
accounting systems, such as is described in [9] and [10]
have been successfully deployed in situations where sophisticated
security is not required and the overhead of ASN.1 encoding and information at regular intervals. In order to ensure against

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decoding is not a concern. Since Accounting Management 8 June 1999

loss of data, the polling allows data interval will need to be collected
on multiple accounting events simultaneously, such systems can store shorter than the
maximum time that accounting data up to can be stored on the limits polled device.
For devices without non-volatile stage, this is typically determined by
available memory; for devices with non-volatile storage the maximum
polling interval is determined by the size of their memory or non-volatile stor-
age, improving scaling properties storage.

The polling model results in an accumulation of data within individual
devices, and enabling efficient transfers.

Since the management agent as a result, data is able typically transferred to retry requests when the
accounting manager in a response
is not received, such batch, resulting in an efficient transfer
process. In terms of Accounting Manager state, polling systems are resilient against scale
with the number of managed devices, and system bandwidth usage scales
with the amount of data transferred.

Without non-volatile storage, the polling model results in loss of
accounting data due to device reboots, but not due to packet loss or
even short-lived
network partitions. Although with SNMP v2 it failures of sufficiently short duration to be handled within
available memory. This is also
possible because the Accounting Manager will continue
to implement such systems using confirmed notifications, we poll until the data is received. In situations where operational
difficulties are not aware of any SNMP-based accounting systems that make use encountered, the volume of
this facility. With SNMPv3, described in [12]-[14], SNMP-based accounting systems data will be capable of incorporating view-based access
controls, described in [16], as well
frequently increase so as user-based security, described to make data loss more likely. However, in [15]. As a result, SNMP v3-based systems can provide
this case the polling model will detect the problem since attempts to
reach the managed devices will fail.

The polling model is typically not appropriate for hop-by-hop
authentication and confidentiality implementation of
roaming services, including wireless data, internet telephony, QoS
provisioning or Internet access. This is because in addition order to access-
control. They cannot however provide data-object based security
required for deployment with untrusted proxies.

Where multiple administrative domains are involved, such as in retrieve
accounting data on roaming users, the
shared use networks described in [1], more sophisticated access con-
trols are often required. Since in shared use networks Accounting Management station
would need to periodically poll the same device
may be accessed by multiple organizations, it devices of all potential roaming
partners, most of which would not hold any relevant data.

Per-device state is typical of polling-based network management systems,
which often necessary to
control access to also carry out accounting data according to the user's organiza-
tion. This ensures that organizations may be given access to account-
ing data relating to their users, but not to data relating management functions, since
network management systems need to users keep track of
other organizations. This implies that the view-based access control
described in [16] is not sufficient, since access rights will depend
not only on the element being collected, but on the identity state of network
devices for operational purposes.

6.3.2. Event-driven model

In the
user to whom that data relates. As event-driven model, a result, shared-use networks rely-
ing on SNMP-based accounting have generally collected data for all
organizations and then sorted device will contact the resulting session records for deliv-
ery accounting server
or manager when it is ready to each organization. While functional, this approach will typi-
cally result in increased processing delay.

6.1.4. DIAMETER

DIAMETER transfer accounting data. Most event-
driven accounting systems, such as defined those based on RADIUS accounting,
described in [33] - [35] is currently not used for account-
ing purposes and does not have accounting messages defined.

6.2. Accounting data [4], transfer protocols

In order for session records to be transmitted between only one accounting
servers, a transfer protocol event per packet, which
is required. Transfer protocols in use
today include SMTP, FTP, and HTTP.

6.2.1. SMTP-based inefficient.

Without non-volatile storage, a pure event-driven model only stores
individual accounting record transfer

Accounting systems using SMTP events that have not yet been delivered and as an accounting data transfer mechanism
typically have access to substantial non-volatile storage. This allows
them to generate, compress if necessary, and store accounting records a
result it has the smallest memory requirements of any of the models.
However, the event-driven model is also the least reliable, since

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until they are transferred Accounting Management 8 June 1999

accounting data loss will occur due to the collection site. Using IPSEC, TLS device reboots, sustained packet
loss, or Kerberos, hop-by-hop security services such as authentication,
integrity protection and confidentiality can be provided. As
described in [18] and [20], data object security is available for
SMTP, and in addition, network failures of duration greater than the facilities described in [17] make it possi-
ble to request and timeout interval.
Since accounting servers will not receive signed receipts, which enables non-repudia-
tion as described in [17]-[23]. As a result, events if operational
difficulties are encountered, event-driven accounting systems uti-
lizing SMTP for accounting data transfer are capable not
very useful in monitoring of satisfying the
most demanding security rquirements.

6.2.2. Other transfer mechanisms

HTTP and FTP have also been device health.

The event-driven model is frequently used for implementation of roaming
services, since this model allows accounting data transfer. Given
access to sufficient non-volatile storage, be sent to the
roaming partners with low processing delay. This permits application of
fraud prevention techniques. However, because roaming accounting systems based on
record formats and transfer protocols can avoid loss events
are frequently of data due to
long-duration network partitions or in even internal faults. Since it high value, the poor reliability of this model is possible for an
issue. As a result, the transfer to event-driven polling model may be driven from the collection site,
the collector can retry transfers until successful, more
appropriate.

Per-session state is typical of event-driven systems without batching,
and as a result, a pure event-driven approach is to be avoided wherever
possible.

6.3.3. Event-driven polling model

In the event-driven polling model an accounting manager will poll the
device for accounting data only when it receives an event. The
accounting client can generate an event when a batch of a given size has
been gathered, when data of a certain type is available or after a
minimum time period has elapsed. Note that while transfer efficiency
will increase with HTTP may
even be able batch size, without non-volatile storage, the
potential data loss from a device reboot will also increase.

Without non-volatile storage, an event-driven polling model will lose
data due to restart partially completed transfers. As device reboots, but not due to packet loss, or network
partitions of short-duration. Unless a result,
file transfer-based minimum delivery interval is set,
event-driven polling systems are not useful in monitoring of device
health.

The event-driven polling model can be made highly reliable, and suitable for use in roaming
since it permits accounting data to be sent to the
batching of roaming partners with
low processing delay. At the same time non-roaming accounting records makes possible can be
handled via more efficient transfers and
application polling techniques, thereby providing the
best of both worlds.

Where batching can be implemented the state required security services in event-driven
polling can be reduced to scale with lessened overhead.
However, such systems are not typically capable the number of providing low pro-
cessing delay, although active devices. If
portions of the network vary widely in usage, then this state may
actually be addressed by less than that of the enhancements
described in [26].

7. polling approach.

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6.3.4. Data collection summary

Key
* = non-volatile storage needed to address this

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7. Review of existing accounting protocols

Accounting systems have been successfully implemented using protocols
such as RADIUS, TACACS+, and SNMP. This section describes the
characteristic of each of these protocols, as well as transfer protocols
such as HTTP, FTP, and SMTP. For a review of accounting attributes and
record formats, see [45].

7.1. Accounting protocols

7.1.1. RADIUS

RADIUS accounting, described in [4], was developed as an add-on to the
RADIUS authentication protocol, described in [3]. As a result, RADIUS
accounting shares the event-driven approach of RADIUS authentication,
without support for batching or polling. As a result, RADIUS accounting
scales with the number of accounting events instead of the number of
devices, and accounting transfers are inefficient. In addition, since
RADIUS accounting is based on UDP and timeout and retry parameters are
not specified, implementations vary widely in their approach to
reliability, with some implementations retrying until delivery or buffer
exhaustion, and others losing accounting data after a few retries.

As a result, RADIUS accounting implementations are vulnerable to packet
loss as well as network failures and device reboots. These deficiencies
are magnified when RADIUS accounting is applied in inter-domain
accounting as is required in roaming, as noted in [1] and [2]. On the
other hand, the event-driven approach of RADIUS accounting is well
suited to handling of accounting events which require low processing
delay, such as is required for credit risk management or fraud
detection.

While RADIUS accounting does provide hop-by-hop authentication and
integrity protection, and IPSEC can be employed to provide hop-by-hop
confidentiality, data object security is not supported, and thus systems
based on RADIUS accounting are not capable of being deployed with
untrusted proxies, or in situations requiring non-repudiation, as noted
in [2].

While in principle extensible with the definition of new attributes,
RADIUS suffers from the very small standard attribute space (256
attributes).

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7.1.2. TACACS+

TACACS+ as defined in [26] offers an accounting model with start, stop,
and interim update messages. Since TACACS+ is based on TCP,
implementations are typically resilient against packet loss and short-
lived network partitions, and TACACS+ scales with the number of devices.
TACACS+ does not support batching, and as a result, is suitable for
handling of accounting events that require moderate though not the
lowest processing delay, since it runs over TCP.

TACACS+ provides for hop-by-hop authentication and integrity protection
as well as hop-by-hop confidentiality. Data object security is not
supported, and therefore systems based on TACACS+ accounting are not
deployable in the presence of untrusted proxies. TACACS+ does not
support non-repudiation.

7.1.3. SNMP

SNMP, described in [27]-[41], has been widely deployed in a wide variety
of intra-domain accounting applications, typically using the polling
data collection model. Since polling allows data to be collected on
multiple accounting events simultaneously, this model results in per-
device state, and supports batch transfers for high efficiency, thus
improving scaling properties and enabling efficient transfers. Since the
management agent is able to retry requests when a response is not
received, such systems are resilient against packet loss or even short-
lived network partitions. While polling implementations without non-
volatile storage can only store accounting events up to the limits of
their memory, and thus are not robust against device reboots or network
failures, when combined with non-volatile storage, they can be made
highly reliable. Thus, addition of support for file-based storage and
subsequent transfer of SNMP-based accounting data is highly desirable.
File-based storage of SNMP data is described in [43], and an FTP MIB is
described in [44].

Although with SNMP v2 it is also possible support confirmed
notifications, so as to implement an event-driven polling model, we are
not aware of any SNMP-based accounting systems that make use of this
facility. With SNMPv3, it is possible to incorporate view-based access
controls, described in [40], as well as user-based security, described
in [38]. As a result, SNMP v3-based accounting implementations can
provide for hop-by-hop authentication, integrity and replay protection,
confidentiality and access-control. They cannot however provide data-
object based security required for deployment with untrusted proxies,
nor does SNMPv3 support non-repudiation.

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Where multiple administrative domains are involved, such as in the
shared use networks and roaming associations described in [1], more
sophisticated access controls are often required. Since in shared use
networks the same device may be accessed by multiple organizations, it
is often necessary to control access to accounting data according to the
user's organization. This ensures that organizations may be given
access to accounting data relating to their users, but not to data
relating to users of other organizations. This implies that access
rights will depend not only on the element being collected, but on the
identity of the user to whom that data relates. Through use of the
contextName, it is possible to run multiple copies of an SNMP MIB, one
for each accessing organization or context. This permits access to be
controlled using the view-based access control model described in [40].

However, as the number of network devices within the shared use or
roaming network grows, the polling model of data collection becomes
increasingly impractical since most devices will not carry data relating
to the polling organization. As a result, shared-use networks or roaming
associations relying on SNMP-based accounting have generally collected
data for all organizations and then sorted the resulting session records
for delivery to each organization. While functional, this approach will
typically result in increased processing delay as the number of
organizations and data records grows.

7.2. Accounting data transfer

In order for session records to be transmitted between accounting
servers, a transfer protocol is required. Transfer protocols in use
today include SMTP, FTP, and HTTP.

7.2.1. SMTP-based accounting record transfer

To date, few accounting management systems have been built on SMTP since
the implementation of a store-and-forward message system has
traditionally required access to non-volatile storage which has to date
not been widely available on network devices. However, an examination
of the characteristics of SMTP-based implementations reveals that they
possess many desirable characteristics.

Accounting management systems using SMTP for accounting transfer will
typically support batching so that message processing overhead will be
spread over multiple accounting records. As a result, these systems
result in per-active device state. Since accounting systems using SMTP
as a transfer mechanism have access to substantial non-volatile storage,
they can generate, compress if necessary, and store accounting records
until they are transferred to the collection site. As a result,

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accounting systems implemented using SMTP can be highly efficient and
scalable. Using IPSEC, TLS or Kerberos, hop-by-hop security services
such as authentication, integrity protection and confidentiality can be
provided.

As described in [13] and [15], data object security is available for
SMTP, and in addition, the facilities described in [12] make it possible
to request and receive signed receipts, which enables non-repudiation as
described in [12]-[18]. As a result, accounting systems utilizing SMTP
for accounting data transfer are capable of satisfying the most
demanding security requirements. However, such systems are not typically
capable of providing low processing delay, although this may be
addressed by the enhancements described in [20].

7.2.2. Other transfer mechanisms

File transfer protocols such as FTP and HTTP have been used for transfer
of accounting data. For example, Reference [9] describes a means for
representing ASN.1-based accounting data for storage on archival media.
Through the use of the Bulk File MIB, described in [43], accounting data
from an SNMP MIB can be stored in ASN.1, bulk binary or Bulk ascii
format, and then subsequently retrieved as required using the FTP Client
MIB described in [44].

Given access to sufficient non-volatile storage, accounting systems
based on record formats and transfer protocols can avoid loss of data
due to long-duration network partitions, server failures or device
reboots. Since it is possible for the transfer to be driven from the
collection site, the collector can retry transfers until successful, or
with HTTP may even be able to restart partially completed transfers. As
a result, file transfer-based systems can be made highly reliable, and
the batching of accounting records makes possible efficient transfers
and application of required security services with lessened overhead.

8. Security issues

As noted previously in this document, accounting applications vary in
their security and reliability requirements. Some uses such as capacity
planning may only require authentication, integrity and replay
protection, and modest reliability while other applications such as
inter-domain usage-sensitive billing may require the highest degree of
security and reliability, since in these cases the transfer of
accounting data will lead directly to the transfer of funds.

Since accounting applications do not have uniform security and
reliability requirements, it is not possible to devise a single

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accounting protocol and set of security services that will meet all
needs. Rather, the goal of accounting management should be to provide a
set of tools that can be used to construct accounting systems meeting
the requirements of an individual application.

As a result, it is important to analyze a given accounting application
to ensure that the methods chosen meet the security and reliability
requirements of the application. Based on the analysis given previously,
it appears that existing protocols are capable of meeting the security
requirements for capacity planning and non-usage sensitive billing
applications. For usage sensitive billing, as well as cost allocation
and auditing applications, new work is required to support the file-
based storage and transfer of bulk data needed to ensure high
reliability. For time sensitive applications such as those supporting
fraud detection or roaming, no existing protocol simultaneously meets
the requirements for high security and reliability, as well as low
processing delay. A summary is given below:

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9. Acknowledgements

The authors would like to thank Pat Calhoun (Sun Microsystems), Jan Melen (Ericsson), Jarmo Savolainen
(Ericsson), and Glen Zorn (Microsoft) for many useful discussions of

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this problem space.

10. References

[1] B. Aboba, J. Lu, J. Alsop, J. Ding, B., Lu J., Alsop J., Ding J., and W. Wang. Wang, "Review of
Roaming
Implementations." Implementations", RFC 2194, Microsoft, Aimnet, i-Pass Alliance, Asi-
ainfo, Merit, September 1997.

[2] B. Aboba, B., and G. Zorn. "Roaming Requirements." Internet draft (work
in progress), draft-ietf-roamops-roamreq-07.txt, Microsoft, March
1998. Zorn, "Criteria for Evaluating Roaming
Protocols", RFC 2477, January 1999.

[3] C. Rigney, A. C., Rubens, W. A., Simpson, S. Willens. W., Willens, S., "Remote Authenti-
cation
Authentication Dial In User Service (RADIUS)." (RADIUS)", RFC 2138, Livingston, Merit,
Daydreamer, April,
1997.

[4] C. Rigney. Rigney, C., "RADIUS Accounting." Accounting", RFC 2139, Livingston, April, April 1997.

[5] J. Gray, A. Reuter. J., Reuter, A., Transaction Processing: Concepts and Tech-
niques,
Techniques, Morgan Kaufmann Publishers, San Francisco, California,
1993.

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INTERNET-DRAFT 6 August 1998

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

[7] D. Crocker, P. Overrell. D., Overrell, P., "Augmented BNF for Syntax Specifica-
tions: ABNF."
Specifications: ABNF", RFC 2234, Internet Mail Consortium, Demon Internet
Ltd., November 1997.

[8] G. Good. Aboba, B., and M. Beadles, "The LDAP Data Interchange Format (LDIF) - Technical
Specification." Internet draft (work in progress), draft-ietf-asid-
ldif-02.txt, Netscape, July 1997. Network Access Identifier",
RFC 2486, January 1999.

[9] K. McCloghrie, J. K., Heinanen, W. J., Greene, A. Prasad. W., Prasad, A., "Accounting
Information for ATM Networks." Internet draft (work in progress),
draft-ietf-atommib-atmacct-04.txt, Cisco Systems, Telecom Finland,
MCI, November 1996. Networks", RFC 2512, February 1999.

[10] K. McCloghrie, J. K., Heinanen, W. J., Greene, A. Prasad. W., Prasad, A., "Managed
Objects for Controlling the Collection and Storage of Accounting
Information for Connection-Oriented Networks." Internet draft (work
in progress), draft-ietf-atommib-acct-04.txt, Cisco Systems, Telecom
Finland, MCI, November 1996. Networks", RFC 2513, February
1999.

[11] B. Aboba, D. Lidyard. "Accounting B., Lidyard, D., "The Accounting Data Interchange Format
(ADIF)."
(ADIF)", Internet draft (work in progress), draft-ietf-roamops-
actng-04.txt, Microsoft, Telco Research, March
actng-05.txt, November 1998.

[12] D. Harrington, R. Presuhn, B. Wijnen, "An Architecture for
Describing SNMP Management Frameworks", RFC 2271, Cabletron, BMC Soft-
ware, IBM, January 1998.

[13] J. Case, D. Harrington, R. Presuhn, B. Wijnen, "Message Process-
ing and Dispatching for the Simple Network Management Protocol
(SNMP)", RFC 2272, SNMP Research, Cabletron Systems, BMC Software,
IBM, January 1998.

[14] D. Levi, P. Meyer, B. Stewart, "SNMPv3 Applications", RFC 2273,
SNMP Research, Secure Computing Corporation, Cisco Systems, January
1998.

[15] U. Blumenthal, B. Wijnen, "User-based Security Model (USM) for
version 3 of the Simple Network Management Protocol (SNMPv3)", RFC
2274, IBM, January 1998.

[16] B. Wijnen, R. Presuhn, K. McCloghrie, "View-based Access Control
Modem (VACM) for the Simple Network Management Protocol (SNMP)", RFC
2275, IBM, BMC Software, Cisco Systems, January 1998.

[17] R. Fajman. Fajman, R., "An Extensible Message Format for Message Disposi-
tion Notifications." Internet draft (work in progress), draft-
ietf- receipt-mdn-08.txt, National Institute of Health, August Disposition
Notifications", RFC 2298, March 1998.

[18] M. Elkins.

[13] Elkins, M., "MIME Security with Pretty Good Privacy (PGP)." (PGP)", RFC
2015, The Aerospace Corporation, October, October 1996.

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INTERNET-DRAFT 6 August 1998

[19] G. Vaudreuil. Accounting Management 8 June 1999

[14] Vaudreuil, G., "The Multipart/Report Content Type for the Report-
ing Reporting
of Mail System Administrative Messages." Messages", RFC 1892, Octel Network
Services, January, January 1996.

[20] J. Galvin.,

[15] Galvin, J., et al. "Security Multiparts for MIME: Multi-
part/Signed and Multipart/Encrypted." Multipart/Encrypted", RFC 1847, Trusted Information
Systems, October, October 1995.

[21] D. Crocker.

[16] Crocker, D., "MIME Encapsulation of EDI Objects." Objects", RFC 1767, Bran-
denburg Consulting, March, March
1995.

[22] C.

[17] Shih, M. C., Jansson, R. Drummond. M., Drummond,R., "MIME-based Secure EDI." EDI",
Internet draft (work in progress), draft-ietf-ediint-
as1-05.txt, Actra, LiNK, Drummond Group, July 1997.

[23] C.
as1-09.txt, December 1998.

[18] Shih, M. C., Jansson, R. M., Drummond, R., Yarbrough, L. Yarbrough. "Requirements
for Inter-operable Internet EDI." EDI", Internet draft (work in progress),
draft-ietf-ediint-req-04.txt, Actra, LiNK, Drummond Group, July 1997.

[24] S. Bradner. "Key words for use in RFCs to Indicate Requirement
Levels." RFC 2119, Harvard University, March, 1997.

[25] in
progress), draft-ietf-ediint-req-06.txt, December 1998.

[19] Borenstein, N., Freed, N. N, "MIME (Multipurpose Internet Mail
Extensions) Part One: Mechanisms for Specifying and Describing
the Format of Internet Message Bodies", RFC 1521, Bellcore, Innosoft, December 1993.

[26] N.

[20] Joffe, D. N., Wing, L. Masinter. D., Masinter, L., "SMTP Service Extension for Imme-
diate
Immediate Delivery", Internet draft (work in progress), draft-ietf-fax-
smtp-session-02.txt, Cisco Systems, Xerox, February 1997.

[27] H. T. draft-ietf-
fax-smtp-session-04.txt, August 1998.

[21] Johnson, H. T., Kaplan, R. S. Kaplan. S., Relevance Lost: The Rise and Fall of
Management Accounting, Harvard Business School Press, Boston, Mas-
sachusetts,
Massachusetts, 1987.

[28] C. T.

[22] Horngren, G. Foster. C. T., Foster, G., Cost Accounting: A Managerial Empha-
sis.
Emphasis. Prentice Hall, Englewood Cliffs, New Jersey, 1991.

[29] R. S.

[23] Kaplan, R. S., Atkinson, Anthony A. Atkinson. A., Advanced Management Account-
ing. Prentice Hall, Englewood Cliffs, New Jersey, 1989.

[30] R. Cooper, R.
Accounting, Prentice Hall, Englewood Cliffs, New Jersey, 1989.

[24] Cooper, R., Kaplan, R. S., The Design of Cost Management Systems.
Prentice Hall, Englewood Cliffs, New Jersey, 1991.

[25] Rigney, C., Willens, S., Calhoun, P., "RADIUS Extensions", draft-
ietf-radius-ext-03.txt, Internet Draft (work in progress), January
1999.

[26] Carrel, D., Grant, L., "The TACACS+ Protocol Version 1.78",
Internet draft (work in progress), draft-grant-tacacs-02.txt,
January 1997.

[27] Harrington, D., Presuhn, R., and B. Wijnen, "An Architecture for
Describing SNMP Management Frameworks", RFC 2571, April 1999.

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INTERNET-DRAFT Accounting Management 8 June 1999

[28] Rose, M., and K. McCloghrie, "Structure and Identification of
Management Information for TCP/IP-based Internets", RFC 1155, May
1990.

[29] Rose, M., and K. McCloghrie, "Concise MIB Definitions", RFC 1212,
March 1991.

[30] M. Rose, "A Convention for Defining Traps for use with the SNMP",
RFC 1215, March 1991.

[31] Case, J., McCloghrie, K., Rose, M., and S. Waldbusser, "Structure
of Management Information for Version 2 of the Simple Network
Management Protocol (SNMPv2)", RFC 1902, January 1996.

[32] Case, J., McCloghrie, K., Rose, M., and S. Waldbusser, "Textual
Conventions for Version 2 of the Simple Network Management Protocol
(SNMPv2)", RFC 1903, January 1996.

[33] Case, J., McCloghrie, K., Rose, M., and S. Waldbusser, "Conformance
Statements for Version 2 of the Simple Network Management Protocol
(SNMPv2)", RFC 1904, January 1996.

[34] Case, J., Fedor, M., Schoffstall, M., and J. Davin, "Simple Network
Management Protocol", RFC 1157, May 1990.

[35] Case, J., McCloghrie, K., Rose, M., and S. Waldbusser,
"Introduction to Community-based SNMPv2", RFC 1901, January 1996.

[36] Case, J., McCloghrie, K., Rose, M., and S. Waldbusser, "Transport
Mappings for Version 2 of the Simple Network Management Protocol
(SNMPv2)", RFC 1906, January 1996.

[37] Case, J., Harrington D., Presuhn R., and B. Wijnen, "Message
Processing and Dispatching for the Simple Network Management
Protocol (SNMP)", RFC 2572, April 1999.

[38] Blumenthal, U., and B. Wijnen, "User-based Security Model (USM) for
version 3 of the Simple Network Management Protocol (SNMPv3)", RFC
2574, April 1999.

[39] Levi, D., Meyer, P., and B. Stewart, "SNMPv3 Applications", RFC
2573, April 1999.

[40] Wijnen, B., Presuhn, R., and K. McCloghrie, "View-based Access
Control Model (VACM) for the Simple Network Management Protocol
(SNMP)", RFC 2575, April 1999.

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INTERNET-DRAFT Accounting Management 8 June 1999

[41] Case, J., McCloghrie, K., Rose, M., and S. Kaplan. The Design Waldbusser, "Protocol
Operations for Version 2 of Cost the Simple Network Management Systems. Protocol
(SNMPv2)", RFC 1905, January 1996.

[42] Rose, M.T., The Simple Book, Second Edition, Prentice Hall, Englewood Cliffs, New Jersey, 1991.

[31] P. R. Calhoun, M. A. Beadles, A. Ratcliffe. "RADIUS Accounting
Interim Accounting Record Extension", Internet draft (work in
progress), draft-ietf-radius-acct-interim-00.txt, July 1997.

[32] D. Carrel, L. Grant. "The TACACS+ Protocool Version 1.78", Inter-
net draft (work in progress), draft-grant-tacacs-02.txt, Cisco Sys-
tems, January, 1997.

[33] P. R. Calhoun, A. Rubens. "DIAMETER Base Protocol", Upper
Saddle River, NJ, 1996.

[43] Stewart, B., "Bulk File MIB", Internet draft (work in progress), draft-calhoun-diameter-01.txt, Sun

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INTERNET-DRAFT 6 August 1998

Microsystems, Merit Networks, March,
draft-stewart-bulk-file-mib-00.txt, November 1998.

[34] P. R. Calhoun. "DIAMETER Resource Management Extensions", Inter-
net

[44] Stewart, B., "FTP Client MIB", Internet draft (work in progress), draft-calhoun-diameter-res-mgmt-00.txt,
Sun Microsystems, March,
draft-stewart-ftp-client-mib-00.txt, November 1998.

[35] P. R. Calhoun. "DIAMETER User Authentication Extensions", Inter-
net

[45] Brownlee, N., "Accounting Attributes and Record Formats", Internet
draft (work in progress), draft-calhoun-diameter-authent-01.txt,
Sun Microsystems, March, 1998.

9. Authors' draft-brownlee-accounting-
attributes-00.txt, May 1999.

11. Author's Addresses

Bernard Aboba
Microsoft Corporation
One Microsoft Way
Redmond, WA 98052

Phone: 425-936-6605
EMail: bernarda@microsoft.com

Jari Arkko
Oy LM Ericsson Ab
02420 Jorvas
Finland

Phone: +358 40 5079256
EMail: Jari.Arkko@ericsson.com

12. Full Copyright Statement

Copyright (C) The Internet Society (1999). All Rights Reserved.
This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain it or
assist in its implmentation may be prepared, copied, published and
distributed, in whole or in part, without restriction of any kind,
provided that the above copyright notice and this paragraph are included
on all such copies and derivative works. However, this document itself
may not be modified in any way, such as by removing the copyright notice
or references to the Internet Society or other Internet organizations,

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INTERNET-DRAFT Accounting Management 8 June 1999

except as needed for the purpose of developing Internet standards in
which case the procedures for copyrights defined in the Internet
Standards process must be followed, or as required to translate it into
languages other than English. The limited permissions granted above are
perpetual and will not be revoked by the Internet Society or its
successors or assigns. This document and the information contained
herein is provided on an "AS IS" basis and THE INTERNET SOCIETY AND THE
INTERNET ENGINEERING TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE."

13. Expiration Date

This memo is filed as <draft-aboba-acct-01.txt>, and expires December
1, 1999.

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