Telektronikk 2/3.2001

1 Introduction

The telecom market is nowadays characterised

by steadily increasing complexity and dynamic

changes. There are multiple causes, like users

whose technical knowledge and demands are

increasing, applications ask for high quality of

services, the number of services and the number

of providers offering these are getting larger, a

variety of technologies are used. Also, business

models are changing in that new roles are pre-

sent and multiple providers are taking those

roles. In order to differentiate themselves in such

a market, providers are aiming at attracting the

users by offering services with assured Quality

of Service (QoS).

Traditionally, QoS is a very important element of

the service offer for users. Assuring QoS requires

a provider to study, understand and handle both

business and technical aspects in a consistent

way. It is not sufficient to understand both of

these issues separately, but they should rather be

observed and studied simultaneously. Providing

services with assured QoS to the users with ever-

increasing demands for services crossing multi-

ple domains administrated by different providers

sets challenges on these providers. Simply, in

order to fulfil users’ demands end-to-end

providers have to co-operate while at the same

time competing for the same market segment.

Hence, the need to describe principles for arrang-

ing relationships between providers is steadily

getting more pronounced. Generally speaking,

any relationship between two actors is associated

with a set of expectations as well as a set of obli-

gations. These expectations and obligations may

be implicit, but it is better to have them explicitly

agreed, especially in a business context. Various

types of agreements present in today’s telecom

market, and their relationships are discussed in

this paper, but the most pronounced type is cer-

tainly a Service Level Agreement (SLA). Briefly,

an SLA is an agreement between two parties that

deals with the level of service to be delivered.

The SLA has two main parts covering business

and technical aspects. Technical aspects and

QoS-related issues are the focus of in this paper.

The technical part of an SLA includes one or

more Service Level Specifications (SLS). An

SLS is a specification that envelopes a set of

parameters and their values that are specified for

a service provided to traffic flow. Mapping

between SLAs and SLSs is not plain and straight-

forward, as will be discussed later.

The situation where services are supported by

the infrastructure based on the Internet Protocol

(IP) technology is even more complex, since

the technology itself, i.e. different aspects and

mechanisms, are not yet mature. On the other

hand, the simplicity and transparency of the IP

allow for a high dynamics factor, that implies

e.g. a variety of services appearing very fast, a

variety of roles taken by the providers (and rela-

tionships between them) that can be changed

easily, and this situation can be described as

a multi-service multi-provider environment.

Assuring QoS in such an environment is chal-

lenging many providers – therefore, the issues

of settling SLAs is getting more pronounced.

Apart from assuring QoS, handling and assuring

SLAs in an IP-based multi-service multi-pro-

vider environment is not trivial. Some of the

issues to help better understanding and handling

of SLAs and their aspects in general and in an

IP-based environment, in particular, are addressed

in this paper.

Settling SLAs between all parties involved in the

service provision/usage enables assurance of the

QoS for user traffic crossing several domains.

Also, the process of designing SLAs is not a

trivial task for a provider. Taking perspective of

the provider (Figure 1), numerous data are rele-

vant as the input to the process of designing SLAs,

negotiating them and finally realising them.

Negotiation of an SLA can be initiated either by

the user who has their requirements, or by the

provider who is offering its services. Both par-

ties should collect relevant input information

before negotiating the SLA. As illustrated in

Figure 1, from the provider’s perspective, the

input includes the knowledge of the business

model/strategic decisions, core business descrip-

tion and focus, service portfolio description,

technical infrastructure, charging schemes,

SLA/SLS monitoring, QoS parameters, and

mechanisms locally implemented in the

provider’s domain. As the input to the negotia-

tion of the QoS-part of the SLA, the service

description and scenario have to be available, the

list of desired objectives for the particular QoS

characteristics (e.g. parameter values) has to be

indicated by the user, and a list of potential sub-

providers should be obtained. By running the

procedure1), the provider would have to make

decisions on the trade-off between the degree

of supporting the mechanisms locally in his

domain, and the degree to which service compo-

Agreements in IP-based Networks

IRENA GRGIC AND METTE RØHNE

Mette Røhne (35) is Research

Scientist at Telenor R&D, Kjeller.

Her main activities include

applied QoS, network design

and techno-economic studies,

performed both in international

and national projects. She re-

ceived her PhD degree in 1999

from the Norwegian University

of Science and Technology.

[email protected]

Irena Grgic (30) is Research

Scientist at Telenor R&D, Kjeller.

She is mainly involved in activi-

ties related to QoS and charging

for different networks and sys-

tems, and studies related to net-

work evolution, both in interna-

tional and national projects. She

holds an MSc in Electrical Engi-

neering from the University of

Zagreb in 1999. She was Task

Leader of Task 5 in EURESCOM

P806-GI.

[email protected]

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