VoIP allows users to make phone calls using an Internet connection rather than a traditional phone line. It works by converting the voice signal from analog to digital, breaking it into packets, sending it over IP, reassembling it at the destination, and converting it back to analog. VoIP has advantages like low cost and portability but disadvantages like quality issues during power outages or network instability. Major challenges include addressing latency, echo, jitter, connection problems through firewalls and NAT, and overall reliability.

1. VoIP
(Voice over Internet Protocol)
Harry Sunarsa

2. Today we will deal with:
• What is VoIP?
• Ways of using VoIP?
• Advantages & disadvantages?
2/7/2013 HS 2

3. What is VoIP?
VoIP allows you to make
telephone calls
using a computer network, over
a data network like the Internet
2/7/2013 HS 3

4. How VoIP Works
1. The voice is converted from an analog to a digital signal.
2. The digital signal is broken up into packets.
3. The packets are sent to the destination via Internet Protocol
(IP).
4. The packets are reassembled into a digital signal at the
destination.
5. The digital signal is converted to an analog signal and played
back through the receiver.
2/7/2013 HS 4

5. VoIP - Basics
Application
Server
Signaling Path
 Peer-to-peer
Call  Or client/server
VoIP Endpoint Server  SIP, H.323, or H.248
(terminal or gateway)
 …/UDP/IP or TCP/IP
IP
Analog Analog
Voice Voice
Bearer Path Control Path
 IP-end to IP-end
 Statistics on performance of
 Encoded voice
bearer “channel”
 Packetized
 RTP Control Protocol (RTCP)
 Real Time Protocol (RTP)
 RTCP/UDP/IP
 RTP/UDP/IP

6. VoIP Network
Application Application
Server Server
Call
Server
Call VoIP
Server
Border Network #2
Gateway
IP VoIP
PBX Network #1
Access Trunk
Business Border Gateway
Gateway PSTN/
Access ISDN
Gateway
GW
Home
Home
Home Home

7. Scenario 1: PC to PC
 Need a PC with sound card
 IP Telephony software(softphone): Skype,
Gtalk, YMessenger , …
 Video optional
2/7/2013 HS 7

8. Scenario 2: PC to Phone
Need a gateway that connects IP network to
phone network
2/7/2013 HS 8

9. Scenario 3: Phone to Phone
 Need more gateways that connect IP network to phone
networks
 The IP network could be dedicated intra-net or the
Internet.
 The phone networks could be intra-company PBXs or
the carrier switches
2/7/2013 HS 9

10. Advantages & Disadvantages
Advantages:
• Low cost - Leads to greater financial savings
• Portability – Not distance or location
dependent.
• Features:
– 3-way calling, call forwarding, callback services
and caller ID are usually standard features (free)
– managing address books, video Conference,
message or data file exchange
2/7/2013 HS 10

11. Advantages & Disadvantages
Disadvantages:
• No service during a power outage
• Quality and Reliability – Depends on the
internet stability
• Security
– identity and service theft, viruses and malware,
denial of service, and spamming
2/7/2013 HS 11

12. Conclusion
• Overall, VoIP is a great low cost alternative for
communication.
• Many companies that depend on international
communication are already making use of such
services in order to lower their operational costs.
• Major corporations have done some significant
research to fix the disadvantages of VoIP
service, as well as improve the overall quality.
• With all of the improvements continually going
on with VoIP, it will soon be accepted by
everyone as an acceptable alternative to PSTN.
2/7/2013 HS 12

13. QUESTIONS?
2/7/2013 HS 13

14. • Q1) Is it possible to use voip solutions in wifi
enabled cellphones?
• A1) Yes , it is possible. In many cellphone
operating systems there are many softphone
applications which enables voip usage. For
example, SJPhone is an application deployed
for Windows mobile 2005 OS

15. • Q2) Is it possible to call the PC from the phone
is used in daily life?
• A2) YES. It is possible by using DID. By the help
of the special numbers which are assigned by
the daily phone network to voip network, it is
possible to provide the transition. This
transmission is also called number of
portability. (DID Number)

16. • Q3: What do you think about the differences
in price between PSDN and VoIP?
• A3: Voip networks uses IP networks and over
these networks voice packages are
transferred. Internet can be used in terms of
IP network. So, there is no need to additional
investment. However, PSTNs performs
communication over the TDM and ATM
networks which have high cost. So, cost
advantage between them is very high and it
explains the difference in cost.

17. VoIP Challenges
• VoIP implementations face problems dealing
with latency , echo and jitter
• Echo: waving of voice
• Latency: Changing in delivery time between
voice packets
• Jitter: Changing in delivery order of voice
packets

18. VoIP Challenges
Connection Problems:
• problems behind NAT between peers.
• Echo and jitter occurs because of packet loss.
• Internet stability problems can cause
reliability problems and this discourages voip
usage.
• routing VoIP traffic through firewall may
blocks voice packets transmission.