- Common accounting interfaces;
- Common interoperability tests and test suites
if interworking between all SPs is necessary; - Etc.
Relevant information related to the management
of SLAs can be found in [GB917], where the
issues of creating SLAs and examples of manag-
ing SLAs are handled.
6.4 EURESCOM
EURESCOM has a long tradition of running
projects dealing with QoS aspects. Regarding
SLA, a common QoS framework for dealing
with QoS/NP in a multi-provider environment
was developed. The terminology harmonising
the understanding between different teams of ex-
perts included in the QoS-related work was set-
tled. In addition, the concept of “one-stop respon-
sibility” was introduced, and the applicability of
the framework is exemplified for the VoIP ser-
vice case. Some of the material included in this
document is developed with those generic prin-
ciples in mind. More details on their results can
be found in [P806-site].
The P906-GI project [P906-site] handled the
means of measuring and managing several
classes offered to different application cate-
gories. The SLA is considered as a tool to
resolve the responsibilities and achieve QoS
end-to-end of the provider’s network. The multi-
provision is handled only related to the charging
of the retail/wholesale services. The concept of
Service Offer Specification (SOS) is introduced,
where a user is offered:
- Network Parameters Level (NPL) reflecting
delay, jitter, loss; - NPL’s guarantees probability;
- Traffic profile;
- Charge/price.
The values of the parameters and their signifi-
cance are decided by the provider by relating
application categories (AC) (e.g. interactive real-
time applications) and quality categories (QC)
(different classes possible to assure by the
provider). More details on the QUASI-model,
where the (QC, AC) mapping is given, and SOS
presented in detail can be found in [P960d1],
[p906ti6].
7 Relating SLAs and SLSs
As already presented, the service description
within an SLA describes the service the cus-
tomer may expect to have delivered from the
provider. Each service should be reflected both
in a related SLA and in SLS(s). Recall that each
SLA includes the service description part and
QoS-related part (in the following called SLS for
short) as illustrated in Figure 9, where the tech-
nical aspects of the service provided are defined.Mapping between SLA related to a service on
the one hand and the corresponding SLS related
to the QoS mechanisms on the other hand is not
a simple one-to-one mapping. This is a challenge
when designing SLAs since it involves the deci-
sion on the selection and implementation of QoS
mechanisms to be used in the network, possible
ways of relating and combining them to ensure
the delivery of the service according to the
agreement. In addition to the decision of QoS
parameters, the QoS mechanisms need to be
tuned properly so the resources are efficiently
used during the service provision.The challenge gets more complex where multi-
ple providers are involved in the service provi-
sion. In that case, the primary provider (that is
responsible for the service delivery towards the
user) has to rely upon the service/QoS provided
by a network they do not have control of.Another challenge arises when a service pro-
vider provides multiple services using a single
network, which is often the case with services
offered in IP-based networks like VoIP and
Video on Demand (VoD). The SLA and SLS
may then be related in a number of ways, some
of them identified and elaborated on in the fol-
lowing:- One-to-one:Each service has a separate SLA
with a description of QoS both at the applica-
tion/service level and the network level, e.g.
including both the required QoS parameter
values at the application/service level and the
required QoS parameter values at the IP level. - Many-to-one:Each service has a separate
SLA with a description of the QoS parameters
at the application/service level. A set of ser-
vices is provided and this set of SLAs share
SLA
Service
Desription
QoS
Desription Figure 9 SLA contains both service description and
QoS description