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Understanding VoIP - 1

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1. Components, Standards and Architectures
 The Big Picture

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 Major VoIP Components

 Terminals
 Packetized voice
 Soft switch
 Media server
 Gateway
 LAN
 WAN
 Standards and Protocols


 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.


 Packetized Voice


 Soft Switches – SIP Servers/Call Managers


 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.


 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


 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

 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.


 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.


 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


 Key VoIP Standards
 IETF
• RFC 3261 SIP
• RFC 2327 SDP
• RFC 1889 RTP
• RFC 0768 UDP
• RFC 0791 IP

 ITU-T
• H.323: Historical
• G.700: Voice coding
- G.711: 64kbps “PCM”
- Many others at lower rates
 IEEE802.3
 TIA Cable Categories


 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


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


 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.


 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.


 Phone to Phone over the Internet
 Broadband internet connection at one
end.
middle.
 Possibly, ISP is different from the ITSP.
 IP phone is required to connect to the
ITSP using SIP protocol.
 Example of IP phone: Grandstream,
Cisco, Dlink, etc.
etc.


 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.
middle.
 Possibly, ISP is different from the ITSP.
 POTs connects to the adapter using the
FXS/FXO port.
 The adapter acts as FX to VoIP gateway.
etc.


 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


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.


PBX Replacement
 Softswitch
-General purpose hardware
- Proprietary software
- Standards-based
- Additional applications:
Messaging, conferencing, IVR, IM,
presence.
 Availability and Survivability
-Redundancy and failover
- Distributed Call managers
- Distributed call control tables
- UPS in closets


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?


 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


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


 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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Understanding VoIP - 1

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