An introduction to policy management
BT Technology Journal
Delivering QoS in the next generation network -- a standards perspective
BT Technology Journal
Quality of service in BT's MPLS-VPN platform
BT Technology Journal
BT Technology Journal
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Voice over IP is already widespread in enterprise private networks and is growing in public switched voice networks as manufacturers withdraw support for earlier technologies. Packet transmission of voice can introduce new impairments, including packet loss, extra sources of delay, and the use of compressed speech coding, all of which may affect voice quality delivered to the user. Factors affecting the quality of a voice telephony connection are described, concentrating on those which are changed by the move to packet transmission, including the complex area of delay. We outline subjective testing based on users' opinions of fragments of recorded audio material or of connections realised in a laboratory, and describe the abstraction of these results into transmission planning models to assist with design of networks and their QoS mechanisms. QoS requirements are stated for a packet technology to support a PSTN and ISDN service in the UK telecommunications environment.