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Telektronikk 2/3.2001

work operator, content provider, content hosting

provider, retailer, application service provider,

etc. One role can be played by many actors and

it is common for an actor/organisation to play

several roles, e.g. the roles of a network provider

and a service provider, the roles of a customer

and user, and so on. An actor should be consid-

ered as a company playing a set of roles on the

market.

The business model considered in the project is

depicted in Figure 2. The model illustrates the

relations between various roles, i.e. SP, Network

Operator (NO) and user. Each business relation

may involve some form of the agreement be-

tween the corresponding parties. For simplicity,

it is assumed that the user also plays the role of

the customer, and the number of roles is limited

so it can be focused on the issues relevant for the

QUASI-model. Furthermore, in the general case,

the SP can have business relations with other

SPs, and with more than one NO. The same

holds for the NO, which can have business

relations with other NOs.

The relationship between a user and a SP is that

of a consumer-supplier model. A similar rela-

tionship, but on a wholesale basis, exists be-

tween the SP and the NP. The two interfaces

shown in Figure 2 include the following:

• User-SP: The service provided over this inter-
  face is typically an end service, such as Inter-
  net access or access to a particular application
  (e.g. IP telephony), and is provided on a retail
  basis. The service to be provided and the
  description of its quality are described in the
  Service Level Agreement (SLA) made be-
  tween the user and the SP. Naturally, SLA
  contains other information, e.g. pricing, legal,
  etc. Details of the underlying transport service
  required for delivering the service might or
  might not be transparent to the user.


• SP-NO: The NO provides, on wholesale basis,
  network connectivity services to SP. SP needs
  these services, since they are necessary for
  delivering the end service to users. The con-
  nectivity service enables the transport of bits,
  and is typically defined in terms of an SLA
  which, similar as above, specifies the rights
  and obligations of both the NO and its user,
  i.e. SP. The NO agrees to provide a certain
  NPL to the SP, and the SP agrees on the char-
  acteristics of the traffic that he is allowed to
  send. The latter is given by the traffic profile
  of the SLA. Other issues (e.g. pricing informa-
  tion, legal issues) could be included in the
  SLA as well.

Note that the lines in Figure 2 represent a direct

business relationship, i.e. flow of business infor-

mation and payments. The actual delivery of the

service can follow a different path – for exam-

ple, the provisioning of IP telephony to the user

by the IP Telephony Service Provider (ITSP)

that has a business relationship will be agreed in

the SLA, while the actual service delivery will

be realised via a network operator providing

Internet access.

Having both physical reference and logical busi-

ness models, the QUASI-model principles are as

described in the following. The user requires a

certain Quality Class (QC) from the SP for the

application/service used. Applications are classi-

fied according to their requirements on the IP

service (e.g. real time, non-real time, etc.) into

Application Categories (ACs). The SP maps QC

and AC and gets NPLs necessary to support the

user’s requirements. An NPL includes a set of

NP parameters (NPPs) with related level and

guarantees. Then SP has to agree with the NO

for provision of the network connectivity service

with the performance values as specified in the

NPLs for the traffic aggregated per QC. The NO

maps the NPLs to adequate quality classes on

the network level and applies proper control

mechanisms in order to provide the requested

performance levels. Naturally, the business

between SP and NO has to be described in the

SLA made between them for the network con-

nectivity with NPL offered to the user. In addi-

tion, the user and SP will make the SLA where

the mapping between QC and AC will be stated

in the language understandable to the user.

3 QUASI-model Mappings

The relationship between different QCs and

ACs, as to be mapped by the SP, are given in

a matrix form (Table 1).

Vasilios Siris (34) is a Re-
searcher at the Institute of Com-
puter Science of the Foundation
for Research and Technology –
Hellas (FORTH), and visiting
Professor at the Dept. of Com-
puter Science of the University
of Crete, Greece. His research
interests include measurement
and analysis of network traffic,
flexible charging schemes
based on resource usage for
Service Level Agreements, and
service differentiation using
weighted end-to-end congestion
control mechanisms. Dr. Siris
obtained his PhD in Computer
Science from the University of
Crete, in 1998, his MS degree in
Computer Science from North-
eastern University, Boston, USA
in 1992, and his BS degree in
Physics from the University of
Athens, Greece in 1990.

[email protected]

Figure 2 Business model considered for the

QUASIMODO project

User OperatorNetwork

point

A or B

Service

Provider

Retail

Wholesale

Business Relation

Physical Connection

Interface

SLA

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