Network Working Group C. Mills
Request for Comments: 1272 BBN
D. Hirsh
Meridian Technology Corporation
G. Ruth
BBN
November 1991
INTERNET ACCOUNTING: BACKGROUND
Status of this Memo
This memo provides information for the Internet community. It does
not specify an Internet standard. Distribution of this memo is
unlimited.
1. Statement of Purpose
This document provides background information for the "Internet
Accounting Architecture" and is the first of a three document set:
Internet Accounting Background & Status (this document)
Internet Accounting Architecture (under constrUCtion)
Internet Accounting Meter Service (under construction)
The focus at this time is on defining METER SERVICES and USAGE
REPORTING which provide basic semantics for measuring network
utilization, a syntax, and a data reporting protocol. The intent is
to produce a set of standards that is of practical use for early
eXPerimentation with usage reporting as an internet accounting
mechanism.
The architecture should be expandable as additional experience is
gained. The short-term Internet Accounting solution is intended to
merge with OSI and Autonomous Network Research Group (ANRG) efforts
and be superseded by those efforts in the long term. The OSI
accounting working groups are currently defining meter syntax and
reporting protocols. The ANRG research group is currently
researching economic models and accounting tools for the Internet
environment.
Internet Accounting as described here does not wrestle with the
applications of usage reporting, such as monitoring and enforcing
network policy; nor does it recommend approaches to billing or tackle
such thorny issues as who pays for packet retransmission.
This document provides background and tutorial information on issues
surrounding the architecture, or in a sense, an explanation of
choices made in the Internet Accounting Architecture.
2. Goals for a Usage Reporting Architecture
We have adopted the accounting framework and terminology used by OSI
(ISO 7498-4 OSI Reference Model Part 4: Management Framework). This
framework defines a generalized accounting management activity which
includes calculations, usage reporting to users and providers and
enforcing various limits on the use of resources. Our own ambitions
are considerably more modest in that we are defining an architecture
to be used over the short- term (until ISO and ANRG have final
pronouncement and standards) that is limited to network USAGE
REPORTING.
The OSI accounting model defines three basic entities:
1) the METER, which performs measurements and aggregates the
results of those measurements;
2) the COLLECTOR, which is responsible for the integrity and
security of METER data in short-term storage and transit;
and
3) the APPLICATION, which processes/formats/stores METER
data. APPLICATIONS implicitly manage METERS.
This working group, then, is concerned with specifying the attributes
of METERS and COLLECTORS, with little concern at this time for
APPLICATIONS.
3. The Usage Reporting Function
3.1. Motivation for Usage Reporting
The dominant motivations for usage reporting are:
o Understanding/Influencing Behavior.
Usage reporting provides feedback for the subscriber on
his use of network resources. The subscriber can better
understand his network behavior and measure the impact of
modifications made to improve performance or reduce
costs.
o Measuring Policy Compliance.
From the perspective of the network provider, usage
reports might show whether or not a subscriber is in
compliance with the stated policies for quantity of
network usage. Reporting alone is not sufficient to
enforce compliance with policies, but reports can
indicate whether it is necessary to develop additional
methods of enforcement.
o Rational Cost Allocation/Recovery.
Economic discipline can be used to penalize inefficient
network configuration/utilization as well as to reward
the efficient. It can be used to encourage bulk transfer
at off hours. It can be used as a means to allocate
operating costs in a zero-sum budget, and even be used as
the basis for billing in a profit-making fee-for-service
operation.
The chief deterrent to usage reporting is the cost of measuring
usage, which includes:
o Reporting/collection overhead.
This offers an additional source of computational load
and network traffic due to the counting operations,
managing the reporting system, collecting the reported
data, and storing the resulting counts. Overhead
increases with the accuracy and reliability of the
accounting data.
o Post-processing overhead.
Resources are required to maintain the post-processing
tasks of maintaining the accounting database, generating
reports, and, if appropriate, distributing bills,
collecting revenue, servicing subscribers.
o Security overhead.
The use of security mechanisms will increase the overall
cost of accounting. Since accounting collects detailed
information about subscriber behavior on the network and
since these counts may also represent a flow of money, it
is necessary to have mechanisms to protect accounting
information from unauthorized disclosure or manipulation.
The balance between cost and benefit is regulated by the GRANULARITY
of accounting information collected. This balance is policy-
dependent. To minimize costs and maximize benefit, accounting detail
is limited to the minimum amount to provide the necessary information
for the research and implementation of a particular policy.
3.2. Network Policy and Usage Reporting
Accounting requirements are driven by policy. Conversely, policy is
typically influenced by the available management/reporting tools and
their cost. This section is NOT a recommendation for billing
practices, but intended to provide additional background for
understanding the problems involved in implementing a simple,
adequate usage reporting system.
Since there are few tools adequate for any form of cost recovery
and/or long-term monitoring there are few organizations that practice
proactive usage reporting in the Internet. Those that do have
generally invented their own. But far and away the most common
approach is to treat the cost of network operations as overhead with
network reports limited to short-term, diagnostic intervention. But
as the population and use of the Internet increases and diversifies,
the complexity of paying for that usage also increases. Subsidies
and funding mechanisms appropriate to non-profit organizations often
restrict commercial use or require that "for profit" use be
identified and billed separately from the non-profit use. Tax
regulations may require verification of network connection or usage.
Some portions of the Internet are distinctly "private", whereas other
Internet segments are treated as public, shared infrastructure.
The number of administrations operating in some connection with the
Internet is exploding. The network "hierarchy" (backbone, regional,
enterprise, stub network) is becoming deeper (more levels),
increasingly enmeshed (more cross-connections) and more diversified
(different charters and usage patterns). Each of these
administrations has different policies and by-laws about who may use
an individual network, who pays for it, and how the payment is
determined. Also, each administration balances the OVERHEAD costs of
accounting (metering, reporting, billing, collecting) against the
benefits of identifying usage and allocating costs.
Some members of the Internet community are concerned that the
introduction of usage reporting will encourage new billing policies
which are detrimental to the current Internet infrastructure (though
it is also reasonable to assert that the current lack of usage
reporting may be detrimental as well). Caution and experimentation
must be the watch Words as usage reporting is introduced. Well
before meters are used for active BILLING and ENFORCEMENT, they
should first be used to:
o UNDERSTAND USER BEHAVIOR
(learn to quantify and/or predict individual and
aggregate traffic patterns over the long term),
o QUANTIFY NETWORK IMPROVEMENTS,
(measure user and vendor efficiency in how network
resources are consumed to provide end-user data transport
service) and
o MEASURE COMPLIANCE WITH POLICY.
Accounting policies for network traffic already exist. But they are
usually based on network parameters which change seldom, if at all.
Such parameters require little monitoring (the line speed of a
physical connection, e.g.,Ethernet, 9600 baud, FDDI). The connection
to the network is then charged to the subscriber as a FLAT-FEE
regardless of the amount of traffic passed across the connection and
is similar to the monthly unlimited local service phone bill.
Usage-insensitive Access charges are sufficient in many cases, and
can be preferable to usage-based charging in Internet environments,
for financial, technical, and social reasons. Sample incentives for
the FLAT-FEE billing approach are:
o FINANCIAL:
Predictable monthly charges. No overhead costs for
counting packets and preparing usage-based reports.
o TECHNICAL:
Easing the sharing of resources. Eliminating the
headaches of needing another layer of accounting in proxy
servers which associate their usage with their clients'.
Examples of proxy servers which generate network traffic
on behalf of the actual user or subscriber are mail
daemons, network file servers, and print spoolers.
o SOCIAL:
Treating the network as an unregulated public
infrastructure with equal access and information sharing.
Encouraging public-spirited behavior -- contributing to
public mailing lists, information distribution, etc.
In other cases USAGE-SENSITIVE charges may be preferred or required
by a local administration's policy. Government regulations or the
wishes of subscribers with low or intermittent traffic patterns may
force the issue (note: FLAT FEES are beneficial for heavy network
users. USAGE SENSITVE charges generally benefit the low-volume
user). Where usage-sensitive accounting is used, cost ceilings and
floors may still be established by static parameters, such as "pipe
size" for fixed connections or "connection time" for dial-up
connection, to satisfy the need for some predictability.
Different billing schemes may be employed depending on network
measures of distance. For example, local network traffic may be
flat-rate and remote internet traffic may be usage-based, analogous
to the local and long distance billing policies adopted by the
telephone companies.
The ANRG is independently investigating policy models and
infrastructure economics for billing and cost recovery.
3.3. The Nature of Usage Accounting
Although the exact requirements for internet usage accounting will
vary from one network administration to the next and will depend on
policies and cost trade-offs, it is possible to characterize the
problem in some broad terms and thereby bound it. Rather than try to
solve the problem in exhaustive generality (providing for every
imaginable set of accounting requirements), some assumptions about
usage accounting are posited in order to make the problem tractable
and to render implementations feasible. Since these assumptions form
the basis for our architectural and design work, it is important to
make them explicit from the outset and hold them up to the scrutiny
of the Internet community.
3.3.1. A Model for Internet Accounting
We begin with the assumption that there is a "network administrator"
or "network administration" to whom internet accounting is of
interest. He "owns" and operates some subset of the internet (one or
more connected networks)that may be called his "administrative
domain". This administrative domain has well defined boundaries.
our domain X
-------------------
/
/ C
/ ------ /
Network A / \ /
----- (diagonals \___/____
cross admin. domain B
boundaries)
The network administrator is interested in 1) traffic within his
boundaries and 2) traffic crossing his boundaries. Within his
boundaries he may be interested in end-system to end-system
accounting or accounting at coarser granularities (e.g., department
to department).
The network administrator is usually not interested in accounting for
end-systems outside his administrative domain; his primary concern is
accounting to the level of other ADJACENT (directly connected)
administrative domains. Consider the viewpoint of the administrator
for domain X of the internet. The idea is that he will send each
adjacent administrative domain a bill (or other statement of
accounting) for its use of his resources and it will send him a bill
for his use of its resources. When he receives an aggregate bill
from Network A, if he wishes to allocate the charges to end users or
subsystems within his domain, it is HIS responsibility to collect
accounting data about how they used the resources of Network A. If
the "user" is in fact another administrative domain, B, (on whose
behalf X was using A's resources) the administrator for X just sends
his counterpart in B a bill for the part of X's bill attributable to
B's usage. If B was passing traffic for C, them B bills C for the
appropriate portion X's charges, and so on, until the charges
percolate back to the original end user, say G. Thus, the
administrator for X does not have to account for G's usage; he only
has to account for the usage of the administrative domains directly
adjacent to himself.
This paradigm of recursive accounting may, of course, be used WITHIN
an administrative domain that is (logically) comprised of sub-
administrative domains.
The discussion of the preceding paragraphs applies to a general mesh
topology, in which any Internet constituent domain may act as a
service provider for any connected domain. Although the Internet
topology is in fact such a mesh, there is a general hierarchy to its
structure and hierarchical routing (when implemented) will make it
logically hierarchical as far as traffic flow is concerned. This
logical hierarchy permits a simplification of the usage accounting
perspective.
At the bottom of the service hierarchy a service-consuming host sits
on one of many "stub" networks. These are interconnected into an
enterprise-wide extended LAN, which in turn receives Internet
service, typically from a single attachment to a regional backbone.
Regional backbones receive national transport services from national
backbones such as NSFnet, Alternet, PSInet, CERFnet, NSInet, or
Nordunet. In this scheme each level in the hierarchy has a
constituency, a group for which usage reporting is germane, in the
level underneath it. In the case of the NSFnet the natural
constituency, for accounting purposes at least, is the regional nets
(MIDnet, SURAnet,...). For the regionals it will be their member
institutions; for the institutions, their stub networks; and for the
stubs, their individual hosts.
3.3.2. Implications of the Model
The significance of the model sketched above is that Internet
accounting must be able to support accounting for adjacent
(intermediate) systems, as well as end-system accounting. Adjacent
system accounting information cannot be derived from end-system
accounting (even if complete end-system accounting were feasible)
because traffic from an end-system may reach the administrative
domain of interest through different adjacent domains, and it is the
adjacent domain through which it passes that is of interest.
The need to support accounting for adjacent intermediate systems
means that internet accounting will require information not present
in internet protocol headers (these headers contain source and
destination addresses of end-systems only). This information may
come from lower layer protocols (network or link layer) or from
configuration information for boundary components (e.g., "what system
is connected to port 5 of this IP router").
4. Meters
A METER is a process which examines a stream of packets on a
communications medium or between a pair of media. The meter records
aggregate counts of packets belonging to FLOWs between communicating
entities (hosts/processes or aggregations of communicating hosts
(domains)). The assignment of packets to flows may be done by
executing a series of rules. Meters can reasonably be implemented in
any of three environments -- dedicated monitors, in routers or in
general-purpose systems.
Meter location is a critical decision in internet accounting. An
important criterion for selecting meter location is cost, i.e.,
REDUCING ACCOUNTING OVERHEAD and MINIMIZING THE COST OF
IMPLEMENTATION.
In the trade-off between overhead (cost of accounting) and detail,
ACCURACY and RELIABILITY play a decisive role. Full accuracy and
reliability for accounting purposes require that EVERY packet must be
examined. However, if the requirement for accuracy and reliability
is relaxed, statistical sampling may be more practical and
sufficiently accurate, and DETAILED ACCOUNTING is not required at
all. Accuracy and reliability requirements may be less stringent
when the purpose of usage-reporting is solely to understand network
behavior, for network design and performance tuning, or when usage
reporting is used to approximate cost allocations to users as a
percentage of total fees.
Overhead costs are minimized by accounting at the coarsest acceptable
GRANULARITY, i.e., using the greatest amount of AGGREGATION possible
to limit the number of accounting records generated, their size, and
the frequency with which they are transmitted across the network or
otherwise stored.
The other cost factor lies in implementation. Implementation will
necessitate the development and introduction of hardware and software
components into the internet. It is important to design an
architecture that tends to minimize the cost of these new components.
4.1. Meter Placement
In the model developed above, the Internet may be viewed as a
hierarchical system of service providers and their corresponding
constituencies. In this scheme the service provider accounts for the
activity of the constituents or service consumers. Meters should be
placed to allow for optimal data collection for the relevant
constituency and technology. Meters are most needed at
administrative boundaries and data collected such that service
provider and consumer are able to reconcile their activities.
Routers (and/or bridges) are by definition and design placed
(topologically) at these boundaries and so it follows that the most
generally convenient place to position accounting meters is in or
near the router. But again this depends on the underlying transport.
Whenever the service-providing network is broadcast (e.g., bus-
based), not extended (i.e., without bridging or routing), then meter
placement is of no particular consequence. If one were generating
usage reports for a stub LAN, meters could reasonably be placed in a
router, a dedicated monitor, or a host at any point on the LAN.
Where an enterprise-wide network is a LAN, the same observation
holds. At the boundary between an enterprise and a regional network,
however, in or near a router is an appropriate location for meters
that will measure the enterprise's network activity.
Meters are placed in (or near) routers to count packets at the
Internet Protocol Level. All traffic flows through two natural
metering points: hosts and routers (Internet packet switches). Hosts
are the ultimate source and sink of all traffic. Routers monitor all
traffic which passes IN or OUT of each network. Motivations for
selecting the routers as the metering points are:
o Minimization of cost and overhead.
(by concentrating the accounting function). Centralize
and minimize in terms of number of geographical or
administrative regions, number of protocols monitored,
and number of separate implementations modified. (Hosts
are too diverse and numerous for easy standardization.
Routers concentrate traffic and are more homogeneous.)
o Traffic control.
When and if usage sensitive quotas are involved, changes
in meter status (e.g., exceeding a quota) would result in
an active influence on network traffic (the router starts
denying access). A passive measuring device cannot
control network access in response to detecting state.
o Intermediate system accounting.
As discussed above, internet accounting includes both
end-system and intermediate system accounting. Hosts see
only end-system traffic; routers see both the end-systems
(internet source and destination) and the adjacent
intermediate systems.
Therefore, meters should be placed at:
o administrative boundaries
only for measuring inter-domain traffic;
o stub networks
for measuring intra-domain traffic. For intra-domain
traffic, the requirement for performing accounting at
almost every router is a disincentive for implementing a
usage-based charging policy.
4.2. Meter Types
Four possible types of metering technology are:
o Network monitors:
These measure only traffic WITHIN a single network. They
include LAN monitors, X.25 call accounting systems and
traffic monitors in bridges.
o Line monitors:
These count packets flowing across a circuit. They would
be placed on inter-router trunks and on router ports.
o Router-integral meters:
These are meters located within a router, implemented in
software. They count packets flowing through the router.
o Router spiders:
This is a set of line monitors that surround a router,
measure traffic on all of its ports and coordinate the
results.
4.3. Meter Structure
While topology argues in favor of meters in routers, granularity and
security favor dedicated monitors. The GRANULARITY of the
accountable entity (and its attributes) affects the amount of
overhead incurred for accounting. Each entity/attribute/reporting
interval combination is a separate meter. Each individual meter
takes up local memory and requires additional memory or network
resources when the meter reports to the application. Memory is a
limited resource, and there are cost implications to expanding memory
significantly or increasing the frequency of reporting. The number
of concurrent flows open in a router is controlled by
o the granularity of the accountable entity
o the granularity of the attributes and sub-categories of
packets
o memory
(the number of flows that can be stored concurrently, a
limit which can also be expressed as the average number
of flows existing at this granularity plus some delta,
e.g., peak hour average plus one standard deviation, or
...)
o the reporting interval
(the lifetime of an individual meter)
There is a spectrum of granularity control which ranges across
the following dimensions. (Most administrations will probably
choose a granularity somewhere in the middle of the spectrum.)
ENTITY: Entities range across the spectrum from the coarsest
granularity, PORT (a local view with a unique designation for the
subscriber port through which packets enter and exit "my"
network) through NETWORK and HOST to USER (not defined here).
The port is the minimum granularity of accounting. HOST is the
finest granularity defined here. Where verification is required,
a network should be able to perform accounting at the granularity
its subscribers use. Hosts are ultimately responsible for
identifying the end user, since only the hosts have unambiguous
access to user identification. This information could be shared
with the network, but it is the host's responsibility to do so,
and there is no mechanism in place at this time (e.g., an IP
option, discussed in section 4.).
ATTRIBUTE: Each new attribute requires that an additional flow
be maintained for each entity. The coarsest granularity is NO
categorization of packets. The finest granularity would be to
maintain state information about the higher-levels protocols or
type of service being used by communicating processes across the
network.
VALUES: Values are the information which is recorded for each
entity/attribute grouping. Usually values are counters, such as
packet counts and byte counts. They may also be time stamps -
start time and stop time, or reasons for starting or stopping
reporting.
REPORTING INTERVAL: At the very finest level of granularity,
each data packet might generate a separate accounting record. To
report traffic at this level of detail would require
approximately one packet of accounting information for every data
packet sent. The reporting interval is then zero and no memory
will be needed for flow record storage. For a non-zero reporting
interval flow records must be maintained in memory. Storage for
stale (old, infrequent) flows may be recycled when their data has
been reported. As the reporting interval increases, more and
more stale records accumulate.
The feasibility of a particular group of granularities varies
with the PERFORMANCE characteristics of the network (link speed,
link bandwidth, router processing speed, router memory), as well
as the COST of accounting balanced against the requirement for
DETAIL. Since technological advances can quickly obsolete
current technical limitations, and since the policy structure and
economics of the Internet are in flux, meters will be defined
with VARYING GRANULARITY which is regulated according to the
traffic requirements of the individual network or administration
and technical limitations.
4.4. Collection Issues
There are two implicit assumptions about the nature of meters and
traffic sources that they measure, both of which have substantial
bearing on collectors.
1. The matrix of communicating entity pairs is large but
sparse and, moreover, network traffic exhibits considerable
source, destination and attribute coherence - so that lists
can be quite compact.
2. Meters can be configured to generate either a static set
of variables whose values are incremented, or a stream of
records that must be periodically transferred and removed
from the meter's memory.
Meters can generate large, unstructured amounts of information
and the essential collection issue revolves around mapping
collection activities into an SNMP framework (or, to the extent
that this is not successful, specifying other collection
paradigms).
There are three major collection concerns:
o data confidentiality
o data integrity
o local and remote collection control
The prime security concern is preserving the confidentiality of usage
data. (See ISO 7498 Part 2, "Security Architecture," for security
terminology used herein.) Given that accounting data are sensitive,
the collector should be able (or may be required) to provide
confidentiality for accounting data at the point of collection,
through transmission and up to the point where the data is delivered.
The delivery function may also require authentication of the origin
and destination and provision for connection integrity (if
connections are utilized). Other security services (e.g., measures
to counter denial of service attacks) are not deemed necessary for
internet accounting at this time. It is assumed that security
services can be provided by SNMP and its mechanisms. (This will
require further investigation.)
In order to have an accurate monitoring system, reliable delivery of
data should be assured through one or more of:
o an acknowledgement retransmission scheme;
o redundant reporting to multiple collectors;
o having backup storage located at the meter.
There is a place for both application polling and meter traps within
this scheme, but there are significant trade-offs associated with
each.
Polling means that the collection point has some control over when
accounting data is sent, so that not all meters flood the collector
at once. However, polling messages, particularly when structured
with SNMP's GET-NEXT operator, add considerable overhead to the
network. Meter traps are required in any case (whether or not
polling is the preferred collection method), so that a meter may rid
itself of data when its cache is full.
The fundamental collection trade-off will be between primary and
secondary storage at the meter, coupled with an efficient bulk-
transfer protocol, versus minimal storage at the meter and a
network-bandwidth-consuming collection discipline.
A final collection concern is whether packets should be counted on
entry into a router or upon exit from a router. It is the nature of
IP that not every packet received by a router is actually passed to
an output port. The Internet Protocol allows routers to discard
packets (e.g., in times of congestion when the router cannot handle
the offered load); it is presumed that higher level protocols (e.g.,
TCP) will provide whatever reliable delivery service the user deems
necessary (by detecting non- delivery and retransmitting).
The question arises, therefore, whether an internet accounting system
should count all packets offered to a router (since each packet
offered consumes some router resources) or just those that are
finally passed by the router to a network (why should a user pay for
undelivered packets?) Since there are good arguments for either
position, we do not attempt to resolve this issue here. (It should
be noted, however, that SMDS has chosen to count on exit only.)
Rather, we require that an internet accounting should provide ability
for counting packets either way -- on entry to or on exit from a
router.
5. Examples
Here follows a series of examples to illustrate what data may be of
interest to service providers and consumers in a number of different
scenarios. In the illustrations that follow straight lines are
interpreted as some sort of LAN. Diagonals are point- to-point
links. Diamonds are routers. We assume that we are in a homogeneous
protocol environment (IP).
5.1 A Single Segment LAN
Consumers and providers on a single LAN service can utilize the same
set of data: the contribution of individual hosts to total network
load. A network accounting system measures flows between individual
host pairs. (On a broadcast LAN, e.g., an Ethernet, this can be
accomplished by a single meter placed anywhere on the LAN.) Using
this data, costs for the network management activity can be
apportioned to individual hosts or the departments that own/manage
the hosts.
Alternately, flows can be kept by source only, rather than source-
destination pairs.
5.2 An Extended (Campus or Facility-Wide) LAN
128.252.100.X 128.252.150.X 128.253.220.X
+----------------+ +----------------+ +----------------+
/ \ / \ / 128.252.100.10 128.252.150.10 128.253.220.10
\ / \ / \ /
+--+-+----------------------+-+----------------------+-+-+
/ \ / \ / 128.252.130.10 128.252.120.10 128.253.140.10
\ / \ / \ /
+-----------------+ +-----------------+ +----------------+
128.252.130.X 128.252.120.X 128.253.140.X
This is the first example in which the information that is germane
for service provider and consumer are not identical. The service
consumers are now the individual subnets and the service provider is
the facility-wide backbone. A service provider is interested in
knowing the contribution of individual subnets to the total traffic
of the backbone. In order to ascertain this, a meter on the backbone
(the longest line in the center of the illustration) can keep track
of flows between subnet pairs. Now the communications between
individual hosts on adjacent subnets are aggregated into a single
flow that measures activity between subnets.
The service consumers, or subnets, might in turn want to keep track
of the communications between individual hosts that use the services
of the backbone. An accounting system on the backbone could be
configured to monitor traffic among individual host pairs.
Alternately an accounting system on each individual subnet could keep
track of local and "non-local" traffic. The observed data of the two
sets of meters (one for the service provider and one for the service
consumers) should have reconcilable data.
5.3 A Regional Network
116.125
+-----------------+
+
/ 116.125.10.10
\ /
/ + / / / + +
/ \ / \
128.242 ----- 128.242.10.10 128.252.10.10 ----- 128.252
\ / \ /
+ +
\ /
\ /
\ /
\ + /
/ 124.110.10.10
\ /
+
+-----------------+
124.110
In this example we have a regional network consisting of a ring of
point-to-point links that interconnect a collection of campus-wide
LANs. Again service provider and consumer have differing interests
and needs for accounting data. The service provider, the regional
network, again will be interested in the contribution of each
individual network to the total traffic on the regional network.
This interest might extend to include measure of individual link
utilization, and not just total offered load to the network as a
whole. In this latter case the service provider will require that
meters be placed at one end or the other on each link. For the
service consumer, the individual campus, relevant measures would
include the contribution of individual subnets or hosts to the total
"outbound" traffic. Meter(s) placed in (or at) the router that
connects the campus- network to the regional network can perform the
necessary measurement.
5.4 A National Backbone
__________
+
/ \
--+ 1 +--
\ /
+
/ \ /
/ + / _______ / \ _______
/ \
+ + + +
/ \ / \ / \ / \
--+ 4 +----\ / 5 \ /-----+ 2 +-
\ / + + \ /
+ \ / +
_______ \ / _______
\ /
\ + /
/ \ /
+
/ \
--+ 3 +--
\ /
+
________
In this last case, the data that the service provider will want to
collect is the traffic between regional networks. The flow that
measures a regional network, or regional network pairs, is defined as
the union of all member-campus network address spaces. This can be
arrived at by keeping multiple individual network address flows and
developing the regional network contribution as post-processing
activity, or by defining a flow that is the union of all the relevant
addresses. (This is a cpu cycles for memory trade-off.) Note that
if the service provider measures individual network contributions,
then this data is, in large
measure, the data that the service consumers would require.
6. Future Issues
This last section is the collector for ancillary issues that are as
yet undefined or out of current scope.
APPLICATIONS standards: Recommendations for storage, processing and
reporting are left out for the moment. Storage and processing of
accounting information is dependent on individual network policy.
Recommendations for standardizing billing schemes would be premature.
QUOTAS are a form of closed loop feedback that represent an
interesting extension of usage reporting. But they will have to wait
until the basic accounting technology is reasonably defined and has
been the subject of a reasonable amount of experimentation.
SESSION ACCOUNTING: Detailed auditing of individual sessions across
the internet (at level four or higher) will not be addressed by
internet accounting. Internet accounting deals only with measuring
traffic at the IP level.
APPLICATION LEVEL ACCOUNTING: Service hosts and proxy agents have to
do their own accounting for services, since the network cannot
distinguish on whose behalf they are acting. Alternately, TCP/UDP
port numbers could become an optional field in a meter, since the
conjunction of a pair of IP addresses and port numbers occurring at a
particular time uniquely identifies a pair of communicating
processes.
The USER has not yet been defined, since an IP option would have to
be added to the IP header to provide for this. This option would
probably contain two parts - a subscriber identification and a user
sub-identification - to allow for the later introduction of quota
mechanisms which have both group and individual quotas. The
subscriber is the fiscally responsible entity, for example the
manager of a research group. In any case, routers must be able to
fall back to accounting by host, since there will most certainly be
hosts on the network which do not implement a new IP option in a
timely fashion.
7. References
International Standards Organization (ISO), "Management
Framework," Part 4 of Information Processing Systems Open Systems
Interconnection Basic Reference Model,ISO 7498-4, 1984.
International Standards Organization (ISO), "Security
Architecture," Part 2 of Information Processing Systems Open
Systems Interconnection Basic Reference Model,ISO 7498-2, 1984.
Security Considerations
Security issues are discussed in sections 2, 3 and 4.
Authors' Addresses
Cyndi Mills
Bolt, Beranek, and Newman
150 Cambridge Park Drive
Cambridge, MA 02140
Phone: 617-873-4143
Email: cmills@bbn.com
Donald Hirsh
Meridian Technology Corporation
11 McBride Corporate Center Drive
Suite 250
Chesterfield, MO 63005
Phone: 314-532-7708
Email: hirsh@meridian.uucp
Gregory Ruth
Bolt, Beranek, and Newman
150 Cambridge Park Drive
Cambridge, MA 02140
Phone: 617-873-3150
Email: gruth@bbn.com
