Voice over IP overview
Matthias Gries, UC Berkeley
Oct. 2002
¿ VoIP context
¿ Int. Telecomm. Union (ITU) VoIP framework
¿ Key computation: audio codec
¿ Optimization goals and constraints
¿ IETF activities
¿ Available tools/libraries and products
¿ VoIP platforms
¿ Implications on a CSA for VoIP
Why use VoIP?
¿ Better bandwidth utilization by:
• Using compression
• Exploiting silence periods during conversations
• Sharing of equipment for voice and data traffic
(unified processing)
¿ Introduction of new services:
• Conferences, distance learning, etc.
VoIP application scenarios
gateway
gateway
gateway
router
router
gatekeeper
H.323
terminals
MCU
PSTN
wireless
Internet
gateway
gatekeeper
router
H.323
terminals
ISDN
Elements of a VoIP network
¿ Terminals: LAN-based communication end-points
¿ Gateway (media and/or signaling):
• Interface between packet- and circuit-switched networks
? Media gateway: voice transcoding, protocol conversion
? Media gateway controller: call handling, call state
? Signaling gateway: signaling mediation
¿ Gatekeeper:
• Admission control, SNMP services, address translation
¿ MCU: Multipoint Control Unit:
• Handling of broadcasts / conference calls
