Upload
catharine24
View
5.412
Download
4
Embed Size (px)
Citation preview
Packet Voice Protocols and VoIP
Fall 2002 – Computer Networking
Seyed Ali Ahmadi
04/11/23 VoIP - Packet Voice Protocols 2
VoIP Technology
Identify the different generations of VoIP
Explain the basic operations of a VoIP Gateway
Describe an ITSP business case
How gateway architecture affects service providers
04/11/23 VoIP - Packet Voice Protocols 3
VoIP technology
Recent Evolution of packet voice and VoIP
VoIP technology
VoIP evolution scenarios
04/11/23 VoIP - Packet Voice Protocols 4
1- Recent Evolutions in VoIP
Describe existing voice over data architectures and name their predecessors
How an ITSP work ?
Characteristics of an Internet call
Advantages and Disadvantages of ITSP
04/11/23 VoIP - Packet Voice Protocols 5
04/11/23 VoIP - Packet Voice Protocols 6
04/11/23 VoIP - Packet Voice Protocols 7
04/11/23 VoIP - Packet Voice Protocols 8
04/11/23 VoIP - Packet Voice Protocols 9
VoFR and VoATM Are Similar to VoIP
Voice is sent as packets intermingled with other traffic types
Voice may be compressed for efficiency
Delay and Delay variation are issues
Priority for voice traffic is required for best performance
04/11/23 VoIP - Packet Voice Protocols 10
04/11/23 VoIP - Packet Voice Protocols 11
VoIP Generations
PC-to-PC
PC-to-Phone
Phone-to-Phone
Traditional PBX migration to VoIP
IP PBX
04/11/23 VoIP - Packet Voice Protocols 12
ISTP Technology
Different Types of IP calls
How ITSP deploy gateways
04/11/23 VoIP - Packet Voice Protocols 13
04/11/23 VoIP - Packet Voice Protocols 14
04/11/23 VoIP - Packet Voice Protocols 15
04/11/23 VoIP - Packet Voice Protocols 16
04/11/23 VoIP - Packet Voice Protocols 17
Generic Gateway
04/11/23 VoIP - Packet Voice Protocols 18
04/11/23 VoIP - Packet Voice Protocols 19
04/11/23 VoIP - Packet Voice Protocols 20
Dedicated Infrastructure for ITSP
Eliminate dependence on performance of the InternetCarries strictly voice traffic or Prioritize voice over dataOffers cheap long distance as initial servicePositioned as enhanced service provider from regulatory point of view
04/11/23 VoIP - Packet Voice Protocols 21
04/11/23 VoIP - Packet Voice Protocols 22
Place gateways in countries with high international tariffs or high calling volumes.These Gateways support standard end user business interfaces to PSTN T1 E1 Analog ISDN
04/11/23 VoIP - Packet Voice Protocols 23
04/11/23 VoIP - Packet Voice Protocols 24
04/11/23 VoIP - Packet Voice Protocols 25
04/11/23 VoIP - Packet Voice Protocols 26
Regulatory Status
Most of the world has taken a hands-off position in regulating the enhanced service providersIn genera ITSPs have mostly positioned them as ISPsAs a result, ITSPs typically do not pay carrier fees such as connection, access or settlement feesIP telephony is regulated in some countries and illegal in some others.
04/11/23 VoIP - Packet Voice Protocols 27
04/11/23 VoIP - Packet Voice Protocols 28
2- VoIP Protocols and Technology
04/11/23 VoIP - Packet Voice Protocols 29
A little on historyCommunication pattern shift from PSTN to VoIPWhy VoIP?Cost savingOpen standards and Multivendor
interoperability Integrated voice and Data network
04/11/23 VoIP - Packet Voice Protocols 30
VoIP Protocols
H.323
Media Gateway Control Protocol (MGCP)
Session Initiation Protocol (SIP)
H.248–Media Gateway Control (MEGACO)
04/11/23 VoIP - Packet Voice Protocols 31
Great Voice Myth
“In order to have a reliable and robust Voice network, there should be one and only one protocol for each function in packet switch network.”
This is not how we are actually doing it now!!
The VoIP networks of today and tomorrow will be constructed using the protocols and applications that best fit the associated technology and business requirements.
04/11/23 VoIP - Packet Voice Protocols 32
Protocol Terminology
ITU: International Telecommunication Union
IETF: Internet Engineering Task Force
04/11/23 VoIP - Packet Voice Protocols 33
Protocol Terminology
H.248 Gateway Control Protocol Collaboration between ITU & IETFAlso referred to as IETF RFC 2885
(MEGACO)
04/11/23 VoIP - Packet Voice Protocols 34
Protocol Terminology
H.323 ITU recommends for “ Packet based
Multimedia communication systems”.Most common VoIP protocolDistributed Architecture
04/11/23 VoIP - Packet Voice Protocols 35
Protocol Terminology
SIP: Session Initiation Protocol IETF RFC 2543 Distributed Architecture
Real-time Transport Protocol – RTP A transport protocol for real-time application IETF RFC 1889 Provides transport for audio/media of VoIP
communication Used by All of VoIP signaling protocols
04/11/23 VoIP - Packet Voice Protocols 36
Protocol Terminology
MGCP Media Gateway Control Protocol IETF RFC 2075Centralized Architecture for Multimedia
applications such as VoIP
04/11/23 VoIP - Packet Voice Protocols 37
04/11/23 VoIP - Packet Voice Protocols 38
04/11/23 VoIP - Packet Voice Protocols 39
Distributed vs. Centralized
04/11/23 VoIP - Packet Voice Protocols 40
Centralized ArchitectureMostly used in older networks
Worked well for basic telephony services
Trade off between easy management and endpoint innovation
Associated with MGCP and H.248
Intelligence focused in centralized Gateway unit (media agent)
Endpoints are relatively or completely dumb.
04/11/23 VoIP - Packet Voice Protocols 41
Centralized ArchitecturePros & Cons
Centralizes management, provisioning and call control
Simplifies call flow for legacy voice features
Stifles innovation of endpoint features
Limitations in building VoIP networks beyond legacy voice features
04/11/23 VoIP - Packet Voice Protocols 42
Distributed Architecture
Associated with H.323 and SIP protocol
Allows Network Intelligence to be distributed between endpoints and control devices.
Intelligence: Call state Calling features Calling routines … any aspect of call handling
04/11/23 VoIP - Packet Voice Protocols 43
Distributed Architecture Pros & Cons
More flexible
VoIP is treated like any other distributed IP application
Well understood by engineers who design and run IP data networks
More complex than the Centralized Architecture
04/11/23 VoIP - Packet Voice Protocols 44
H.323
Originally designed as a transport protocol for MM Apps. in LANStill used for Video ConferencingMost widely used VoIP signaling and call controlUmbrella Protocol: All aspects of call transmission From call establishment to capabilities exchange
to network resources
04/11/23 VoIP - Packet Voice Protocols 45
H.323
Defines:RAS
RegistrationAdmissionStatus
H.225 for call set-upH.245 for capabilities exchange