Page 524 - Handbook of Modern Telecommunications

Network Organization and Governance 4-55

XDSL service:

• Number of problems
• Average duration of problem restoration
Cable networks:

• Number of problems
• Average duration of problem restoration
Packet switching service:

• Throughput rate
• Relationship: discarded packets to all packets
IP services:

• Packet delay in one direction
• Packet delay in both directions
• Packet loss in one direction
• Packet loss in both directions
• Transmission throughput

4.4.2.3 Classification of Metrics
Surveys of market research companies clearly show where customer interests lie. This interest should be
taken seriously by service providers and network operators. Customers are interested, first of all, in ser-
vice-oriented metrics that are technology independent. This means that technology-dependent metrics
need not to be included in SLAs. But they are important in computing technology-independent metrics.
The priority sequence of metrics from the perspective of customers is the following:
• Availability of all components (devices and transmission links) connected to the network
• Availability of application on the network (accessing applications)
• Availability of servers
• Network round-trip time or network delay
• Application response time during peak periods
• Availability of clients
• Server delay
• Mean application response time
• Client delay
• Median application response time
• Percentage of transactions completed within defined performance levels

4.4.2.4 General Considerations
Service availability (SA) is a percentage (SA%) that indicates the time during which the contracted ser-
vice at the respective service access point (SAP) is operational. Operational means that the customer has
the ability to use the service as specified in the SLA.
An event affecting the service at the service access point can be defined as an outage. The duration of
this specific event is the outage interval. Ordinarily this concept is used for the unavailability (UA%) and
service availability percentage (SA%) calculations as follows:

SA% = 100% − UA%

UA% = (Sum of outage intervals/Activity time) × 100%