Page 541 - Handbook of Modern Telecommunications

4-72 CRC Handbook of Modern Telecommunications, Second Edition

• Packet loss (network and element layers)
• Throughput (network and element layers)
Determination of views: All views are expected to be prepared in accordance with TMN layers. The result
is a hierarchy of the service layer, network layer, element management layer, and network element layer.
Determination of reports: All reports are expected to be prepared in accordance with TMN layers.
The result is a hierarchy of the service layer, network layer, element management layer, and network ele-
ment layer.
It is assumed that basic data are collected by unified collection techniques. Processing data should
follow the same unified guidelines. The minimal requirement permits accessing all data on a Web
server. Service providers and clients may access these data, and if required, they can generate reports
on their own.
Just a minimal set of standard reports are targeted. These standard reports are in accordance with the
reports agreed upon in the SLAs. These report on the following metrics:

• Availability (multiple TMN layers)
• Delays and latencies (network and element layers)
• Packet loss (network and element layers)
• Throughput (network and element layers)

4.4.6 Role of SLAs in Settlements between Service Providers
4.4.6.1 Present Difficulties
When customers are able to control the performance of service providers, their trust level toward the
service providers will increase. The same is true with service providers when they conduct business with
each other. Customer churn cannot be quantified easily, but the negative impact is obvious for business
processes and references.
Some of the difficulties may be summarized as follows:
• How is availability defined? If it is the average downtime per month, the supplier could still meet
the terms of the agreement for the month as a whole, despite one very critical day, by exceeding
the terms on all other days.
• Complex SLAs may require very time-consuming negotiations between technicians and layers.
SLAs should be as short as reasonable, and they should be off-the-shelf contracts, except in cases
where very large, customized deals are involved.
• Guaranteed SLAs over several service providers are very difficult to achieve. So-called back-to-
back SLAs, which create a kind of service level chain, would be the solution. But these are very
hard to negotiate, especially across borders in Europe, where different jurisdictions prevail.
• SLAs must be lined up with special SLAs of the customers, since many companies offer agreed
service levels to their own customers.
4.4.6.2 Carriers are Fighting for Stronger SLAs
Service providers are very much interested in their service portfolios. They use best-of-breed tools to
differentiate themselves from their competitors. They occasionally publish performance metrics about
the segments of the networks they support. Table 4.4.10 shows metrics that may also be included in
SLAs. These metrics are very important for multinational enterprises because they represent perfor-
mance guidelines in the global network. They help to set realistic goals. All values in this table may
be accepted.
The lower-level infrastructure and the role of subcontractors are not further detailed.