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