3. Major VoIP Components
Terminals
Packetized voice
Soft switch
Media server
Gateway
LAN
WAN
Standards and Protocols
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4. Terminals
Features Description
Protocols/Standards SIP RFC3261, SDP, TCP/IP/UDP, RTP/RTCP,
HTTP, ARP/RARP, ICMP, DNS, DHCP, PPPoE,
TFTP, NTP, STUN.
Network Interfaces Dual switched 10/1000Mbps ports with
integrated PoE
Voice codec G.711 a/u (64kbps), G.729A/B(8kbps)
Telephony Features Hold, Transfer, Forward, 3-way Conference, Call
Waiting, Multiple SIP Accounts, etc.
QoS Layer 2 (802.1Q, 802.1p) and Layer 3 (ToS,
DiffServ, MPLS) QoS
Advance Voice Silence Suppression, Jitter Buffer, Voice
Quality Features Activation Detection, Packet Loss Concealment
Operating System Linux
Example Grandstream, Dlink, Cisco, X-Lite, etc.
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7. Softswitch: A programmable network switch that can process the signaling for all
types of packet protocols.
Also called SIP Server, SIP Proxy, Call Manager, VoIP Switch, Call Agent, IP Centrex,
Hosted PBX, User Agent, Gatekeeper (H.323).
According to International Softswitch Consortium, a softswitch should be able to:
1. Control connection services for a media gateway and / or native IP endpoints
2. Select processes that can be applied to a call.
3. Providing routing for a call within the network based on signaling and customer
database information.
4. Transfer the control of the call to another element .
5. Interface to and support management functions such as provisioning, fault, billing,
etc.
The switching technology in a softswitch is in software (hence the name) rather than
in the hardware as with traditional switching center technology.
This software programmability allows it to support IP telephony protocols
(H.323, SIP, MEGACO, etc.).
Examples of Softswitch: Asterisk, 3CX, Volcatel, etc.
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8. In Summary, the two main functions of a Softswitch are:
1. Terminal Control
2. Call Control
• Registration: Authentication, directory
entry
Terminal • Admission: Permission to make / receive
Control calls
• Status: Call disposition
• Call Signaling: Address resolution, setup,
tear down
Call Control • Call routing
• Call accounting
• Call detail record
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9. Media Server or Content Server
A computer appliance, ranging from an enterprise class machine with a dedicated
software application providing contents such as voice, video, music, text, graphics.
Two interesting types of media/content:
1. Integrated Messaging
2. Video Server
Integrated Messaging Other Media
• Voicemail, Email, Fax • Web pages
• Text-to-speech, speech-to-text • Digital right management
• Web-style user interface • Music
• Google earth
Video Server • Countless applications
• Basic Cable
• Video on Demand: Movie “rentals”
• Pay-per-view, IPTV
• PVR functionality
• Game Server
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10. Gateways – Media Gateway
Gateways are Protocol Converters
Media Gateway converts traditional TDM
to RTP stream and vise versa.
TDM belongs to the PSTN world.
RTP belongs to the IP world.
Media and Signaling gateway could be a
single device or a separate device.
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11. Gateways – Signaling Gateway
Gateways are Protocol Converters
Signaling Gateway converts SIP to SS7 and
vice versa.
SIP belongs to the IP world.
SS7 belongs to the traditional PSTN world.
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12. LANs and WANs
LAN: In-building
Ethernet: 10 – 1000Mbps
Cabling: Cat5, Cat6e twisted pair
MAC Address
Power Over Ethernet
WAN: Between buildings
IP Addresses
Access: DSL, Cable, T1, Fiber, Microwave
Network Protocol: IP, Frame relay, ATM
Carrier Ethernet
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14. Where Are We Going?
Broadband IP Dial Tone.
IP-PSTN
-Internet Protocol – Packet
Switch Telephone Network.
- IP Packet to any other point
> 1Mbps
Carrier Ethernet
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15. 2. VoIP Architectures and Implementation Choices
Computer-Computer VoIP Over The Internet
Requirements:
- Computer/Mobile Phone/PDA, ……
- Internet Access.
- Software: Skype, Nimbuzz, IM, …….
- Directory, call setup/control.
- Sound card and headset or USB phone.
- Operating system: IP/UDP protocol
stack.
Considerations:
- Free (with internet connection)
- Interoperability: Standard?
- Less user-friendly than PSTN.
- Variable quality of voice
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16. Skype and IM
Proprietary technology
- Skype directory is based on Kazaa
- It uses P2P file sharing
- Good quality voice: Uses 15kbps codec
Works through NATs
- Communications encrypted
- Your computer could relay traffic
Good HMI – Human Machine Interface
Yahoo, Google, MSN, AOL, Nimbuzz.
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17. Computer to Phone
Broadband internet connection at one
end.
POTs at other end.
ITSP/VoIP Service provider in the
middle.
Variable voice quality.
E1 connection to circuit-switch PSTN.
Possibly ISP is different from the ITSP.
ITSP is located offshore.
Softphone required to connect to the
ITSP using SIP protocol.
Example of softphone: X-Lite, 3CX, etc.
Example of ITSP: Skype, Belgacom,
etc.
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18. Phone to Phone over the Internet
Broadband internet connection at one
end.
POTs at other end.
ITSP/VoIP Service provider in the
middle.
Variable voice quality.
E1 connection to circuit-switch PSTN.
Possibly, ISP is different from the ITSP.
ITSP is located offshore.
IP phone is required to connect to the
ITSP using SIP protocol.
Example of IP phone: Grandstream,
Cisco, Dlink, etc.
Example of ITSP: Skype, Belgacom,
etc.
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19. Phone to Phone over the Internet
ITSP either supplies the adapter or user
verifies compatible off-the-shelf adapter.
Broadband internet connection at one
end.
POTs at other end.
ITSP/VoIP Service provider in the
middle.
Variable voice quality.
E1 connection to circuit-switch PSTN.
Possibly, ISP is different from the ITSP.
ITSP is located offshore.
POTs connects to the adapter using the
FXS/FXO port.
The adapter acts as FX to VoIP gateway.
Example of ITSP: Skype, Belgacom,
etc.
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20. Managed-IP Telephone Service Provider
All IP end-to-end network.
Radio Access Network could be wireless
- (WiMAX, Wi-Fi, LTE), cable or fibre.
End-to-end Carrier Ethernet Network.
IP network QoS methods.
Voice quality is guarantee.
E1 connection to circuit switched PSTN.
ISP and ITSP – same company.
Provider connects with upstream ISP for
long distance call termination and www.
Provider supplies the adapter and
modem.
Example: ipNX
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21. 3. VoIP for Businesses and Organizations
VoIP-Enabled PBX
PBX provides all VoIP functions.
-Call management
- Integrated gateway
- Integrated voicemail
Supports VoIP and traditional phones
-Phased implementation of VoIP
in-building.
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23. Hosted PBX
Softswitch at Service Provider
-SIP messages over network
- Customer configuration via web portal
- IVR, ACD hosting too
Strategic Advantages
-Professional implementation
- Scalability, flexibility
- Security, reliability
Financial advantages
-Lease vs. buy: capital, maintenance
- Reduce staffing
Disadvantages
-Lack of control
- Feature set? Capacity?
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24. IP Centrex
Hosted softswitch service from the Phone
Company
-Huge Centrex customer base
Higher level of trust
-Professionalism, longevity
Multilocation benefits
-Uniform services, support
Bundled services
-Access circuit plus telephony
Seamless services
-Home-to-office VPN, telephony
Features and pricing
-Per user, per month
- Local number, DID
- Desktop, web collaboration
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25. Open-sourced IP-PBX Software
Free code updated by users
Asterisk: One of the “Oldest”
-IP PBX plus signaling server,
media gateway, analog/TDM PBX, IVR,
messaging server
Supported commercially
-30 – 50% cost of proprietary
- Asterisk (Digium)
- sipX, SIPfoundry (Pingtel)
- Others: vovida, Freeswitch
Disadvantages
-May be difficult to implement
- Requires skilled technicians
- Lack of management/support tools
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26. SO/HO IP Phone Features and Uses
Small / home office
All-in-one device
-Fast processor, jitter buffer
- Linux OS, browser, software
- SIP, MGCP
- Ethernet switch, PoE, PPPoE
- Bluetooth
- Router, DHCP, NAT, firewall
- VPN, QoS support
Dialing features – dial by:
- Phone number, SIP address,
IP address, directory, voice recognition,
softkeys, presence/location notice,…….
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