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VOZ Y VIDEO SOBRE IP
Fundamentos de tecnologas
y servicios de comunicaciones
de voz y video.
JUAN FCO. GONZALEZ P.
Ing. en Telec. Conectividad y redes
Voice Over IP (VoIP): Internet Telephony
VoIP Definition
The use of IP networks, namely the LAN and WAN, to carry voice
Internet Telephony
The use of the Internet that was originally designed to carry computer data to carry voice
A packet switched network
Voice was originally carried over circuit switched networks PSTN
Related Issues
Voice over Frame Relay
Voice over ATM
Further Evolution
Media transmission over IP Audio
Image
Video
VoIP Basic Functions
Signaling
Database services Mapping addresses (IP to Phone numbers) etc.
Call connect and disconnect (bearer control)
CODEC operations For encapsulating voice into data packets
Some Codecs
VoIP Components
Servers For processing IP calls and manage interaction with PBX etc.
End-point devices such as phones
Media and VoIP gateways
IP network
Overcoming the Challenges
Latency
Jitter
Bandwidth
Packet loss
Reliability
Scalability
Security
Features
Interoperability
Switch over cost
Latency
Latency is the time taken for a packet to arrive at its destination Packet switching overhead
Congestion
Latency may result in voice synchronization problems
Jitter
Jitter is the delay experienced in receiving a packet when a packet is expected to arrive at the end point at a certain time
Bandwidth
When bandwidth is shared between voice and computer data, certain bandwidth may have to be allocated for voice communication on a network
Packet Loss
Packet loss in unavoidable
It can be minimally tolerated in voice transmission It should not, in the first place, distort the audio
Reliability
Because the computer network is used, the reliability of the network will have an impact on the telephony service
In the analog telephone industry, reliability of 99.999 percent uptime is required
The above is known as five nines
VoIP networks can achieve over 98 percent reliability ?
Scalability
Ability to add more telephony equipment as the company grows Network bandwidth and other issues may have an effect on scalability
Security
As VoIP uses the Internet, for example, it is vulnerable to the same type as security risks
Hacking
Denial of service
Eavesdropping
Features
IP telephony need to match and, in the long run, exceed the features provided by the PSTN
Call waiting
Three way calling etc.
Interoperability
IP telephony equipment manufactured by different vendors must be able to talk to each other
Standardized protocols are needed
Migration Cost
The cost of migrating from legacy PBX to IP PBX
Facing the Challenges
Many of the challenges listed have now been addressed by effective network performance management and standardized protocols
Network Performance Management
Addresses the following issues: Latency
Reliability
Security
Standardized Protocols
Interoperability
Migration Path
Source: Avaya
Gateways and Gatekeepers
Gateway equipment performs the task of allowing non-IP equipment to talk to IP equipment
Gatekeepers manage the calls within a particular zone
Both items will be present in a H.323 network
Other Terminology
FXS Foreign Exchange Station
FXO Foreign Exchange Office
FXS
A device that connects on one side to an analog equipment and other side to the Internet
A simple example is the ATA (Analog Telephone Adapter) that connects an analog phone to the Interent
FXO
An interface between the PSTN and the local equipment that would also connect to the Internet
An example use would be to have a telephone that connects to the Internet and, at the same time, has a connection to the PSTN as well
There are equipment that will automatically switch to the PSTN if for some reason the VoIP connection does not function
Source: QTelNet
Also known as ATA Analog Telephone Adapter
Source: QTelNet
Source: QTelNet
Source: QTelNet
Source: QTelNet
Source: QTelNet
Source: QTelNet
Source: QTelNet
Source: QTelNet
Source: QTelNet
Source: QTelNet
Modes of Internet Telephony
PC-to-PC
PC-to-Phone
Phone-to-Phone
Note: In the above listing phones can be either analog or digital phones
Case 1: PC to PC Connection
Made over the internet for voice connection
Sample product: Net2Phone
NetMeeting
Calls are free
Vendors
Skype
Earthlink
Case 2: PC to Phone Connection
Made over the Internet for connecting PC to phones
Sample Product: Net2Phone
Need to pay for the calls but they are relatively inexpensive Cheaper compared to phone to phone calls made over the Internet
Procedure
1. Download our FREE software2. Create a Username and Password3. Select the amount of money you want to add to your account4. Login to the software5. Make PC2Phone calls and send faxes
- Net2Phone
Dialing from the PC
Features
PC2PC
PC2Phone
PC2Fax
Instant messaging
Vendors
Net2Phone
Case 3: Phone to Phone Connection
Phone to phone calls are made over the Internet
A special phone will connect to a hub or switch on the network
Typical Layout
ATA
Connections
Vonage Broadband Phone Features
Voicemail Plus
Caller ID with Name
Call Waiting
Call Forwarding
3-Way Calling
In-Network Calling
Traveling with Vonage
Area Code Selection
Call Transfer
Click-2-Call
Call Return (*69)
Caller ID Block
(*67)
Repeat Dialing
International
Call Block
Ring Lists
Call Hunt
Analog Telephone Adapter (ATA) Manufacturers
CISCO
AT&T
Linksys
A Note on Implementation Problems
Some of the adapters may not work properly when used in conjunction with a NAT
Some vendors may lock the ATA meaning that it would only work with their service
A fee may have to be paid to unlock the ATA
Soft Phones
Soft phones do not require an ATA for connection
They connect through the computer It can be used for example with a notebook computer to facilitate mobility
Residential Broadband Phone Companies
Vonage
AT&T CallVantage
VoicePulse
Packet8
VocalTec
Movistar
GTD
ENTEL
CLARO
Global Crossing
IP Standard Setting Bodies
IETF Internet Engineering Task Force
ITU International Telecommunication Union
IP Telephony Standards and Protocols
H.323 ITU standard
SIP IETF standard
MGCP IETF standard
H.248 ITU standard
Megaco IETF standard
H.323
An ITU recommendation applicable to Packet-based multimedia communications systems. - CISCO
H.323 defines a distributed architecture for creating multimedia applications, including VoIP CISCO
Older and more established protocol
H.323 Components
Source: CISCO
Scope of H.323
Source: CISCO
Deployment of H.323 Network
Source: CISCO
Source: CISCO
Source: CISCO
SIP
Relatively newer protocol
Source: CISCO
Source: CISCO
Source: CISCO
Other Protocols
RTP Real-time Transport Protocol
Responsible for end-to-end delivery of real-time data such as audio and video
RTCP Real-time Transport Control Protocol
The optional companion protocol to RTP that furnishes information about the quality of data delivered by RTP
Summary
Implementations based on the three different protocols will be in use
All three will be implemented with IP as the common core
H.323 is the older implementation that may give way to SIP Backed by CISCO
Video-over-IP: Applications and
Interfaces
Video-over-IP Applications and
Interfaces
Cisco Systems estimate
By 2011, 60 percent of Internet traffic will be video traffic
Requirements for prediction to come true
Continual price drop in video-over-IP hardware
Networks must further augment capacities, reliability
Video-over-IP services categories
Streaming video, IPTV, videoconferencing
Video-over-IP transmission
Digitize audio, visual signals
Use video codecs
Streaming Video
Simplest among all video-over-IP applications
Basic computer hardware, software requirements
Video-on-demand
Files stored on video streaming server
Popular
Viewer chooses video when convenient: Web browser
Streaming video
Video issued live
Directly: source to user
Streaming video
Video issued live
Directly from source to user
Drawbacks
Content may not be edited before distribution
Viewers must connect with stream when issued
Video-on-demand benefits
Content viewed at users convenience
Viewers control viewing experience
Pausing, rewinding, fast-forwarding
Streaming Video
Streaming Video
Figure 11-9 Video-on-demand and live streaming video
Streaming Video
Considerations
Number of clients receiving each service
Point-to-point video over IP
Point-to-multipoint video over IP (not necessarily multicast transmission)
Network type classification
Private
Public
Most streaming video
Takes place over public networks
IPTV (IP Television)
Telecommunications carriers, cable companies are upgrading networks to deliver high-bandwidth
Internet connections
IPTV digital television signals is a valuable added service
Elements
Telco accepts video content at a head end
Telcos CO (central office)
Servers provide management services
Video channel assigned to multicast group
IPTV (IP Television)
Figure 11-10 A telecommunications carriers IPTV network
IPTV (IP Television)
Advantages of IPTV multicasting
Simple to manage content delivery
Issue one multicast transmission to entire group
Local loop capacity issues
Most rely on copper to home (limits throughput)
Sending all channels could overwhelming local loop
Solution: Telco transmits only content ordered
IGMP (Internet Group Management Protocol)
Manages multicasting
Routers communicate using multicast routing protocol
IPTV (IP Television)
Compressed, digital video signal travels like data signal
Over technologies like DSL or WIMAX
Advantage
Telecommunications carrier, cable company
Control connection end to end
Better monitor and adjust QoS
IPTV (IP Television)
Figure 11-11 IPTV set top
box
Set top box
Decodes video signal, issues to television
Manages delivery
Communicating with content servers
Manage services
Pay per-view, video-on-demand programming
Videoconferencing
Unidirectional video-over-IP services
Video delivered to user who only watches content
Videoconferencing
Full-duplex connections
Participants send and receive audiovisual signals
Real time
Benefits
Cost savings, convenience
Replace face-to-face business meetings
Allows collaboration
Videoconferencing
Videoconferencing uses
Telemedicine
Tele-education
Judicial proceedings
Surveillance (usually unidirectional)
Hardware, software requirements
Computer workstation
Means to generate, send, receive audiovisual signals
Video terminal, video phone
Figure 11-12 Video phone
Videoconferencing
Video Bridge
Video bridge
Manages multiple audiovisual sessions
Participants can see, hear each other
Conference server
Hardware or software
Leased Internet-accessible video bridging services
Occasional videoconference use
Video bridge depends on signaling protocols