Table of Contents:

Definition and Overview

1. Introduction

2. Why Are SLAs Important?

3. What Are the Basic Components of Frame Relay SLAs?

4. What Service Levels, by Components, Should Be Negotiated with the Service Provider?

5. Carrier Compensation: What Does It Mean?

6. How Can We Ensure That the Service Provider Is Meeting the Agreed-upon Service Levels?

7. What Are the Next Steps in Implementing and Monitoring Frame Relay–Service Levels with the Service Provider?

Self-Test

Glossary

PDF of this tutorial

Frame relay SLAs currently encompass a number of key network system parameters, above and beyond what typical signaling network management protocol (SNMP)–managed systems are able to monitor. These parameters may cover the network as a whole, as individual sites, or even as a single PVC. The level to which the SLA is defined depends on the criticality of the network to a business. SLAs covering individual components allow less downtime than those covering entire networks do. Frame-relay service-level components include the following:

• network availability—measured over a month as a calculation of the following:
(hours in a day) x (days in a month) x (number of sites) – (network outage time)
--------------------------------------------------------------------------------
(hours in a day) x (days in a month) x (number of sites)

• PVC availability—measured over a month as a calculation of the following:
  (hours in a day) x (days in a month) x (number of PVCs) – (PVC outage time)
  --------------------------------------------------------------------------
  (hours in a day) x (days in a month) x (number of PVCs)

• average round-trip network delay—measured over a month as a calculation of the following:
  (cumulative samples of end-to-end, roundtrip delay for all PVCs)
  ----------------------------------------------------------------
  (number of samples)

• average round-trip PVC delay—measured over a month as a calculation of the following:
  (cumulative samples of end-to-end, roundtrip delay for the PVC)
  ---------------------------------------------------------------
  (number of samples)

• effective PVC throughput (frame delivery ratio)—measured over a month as a calculation of the following:
  (egress frame count)
  ---------------------------------------------------------------------------------
  (ingress frame count) – (frames above committed burst size) - (excess burst size)

• mean time to respond—measured as a monthly average of the time from inception of trouble ticket until repair personnel is on site as follows:
  (total time in hours to respond)
  ---------------------------------
  (total number of trouble tickets)

• mean time to repair or restore—measured as a monthly average of the time from inception of trouble ticket until outage is repaired to customer satisfaction as follows:
  (total outage time in hours)
  ---------------------------------
  (total number of trouble tickets)

These SLA components, although calculated in a fairly standard manner among carriers, are implemented inconsistently. When working with a carrier to determine service levels, it is important to understand in detail the meaning of each of those measurements.