This paper provides a general introduction to real-time applications o
ver networks operating the internet protocol. A particular issue facin
g such applications is the difficulty in consistently achieving the re
quired quality of service. This paper looks at the role of the network
, the operating system and the application environment in delivering t
he required quality of service. The main focus is an outline descripti
on of an application architecture designed to support a wide range of
real-time applications, with particular reference to audiovisual servi
ces.