Voice over IP (VOIP) services.

1. Seminar on
VoIP SERVICES
By: Pankaj Saharan
Student ID: 77197A
Masters in Mobile Computing

2. Contents
• How VoIP came into picture?
• What is VoIP exactly?
• What are the advantages?
• How can we use it?
• What are the different standards?
• Who are the different service providers?
• What technology the leader in VoIP is using?
• What are the challenges ahead
• How is the future

3. Circuit-Switched Telephony
Traditional PSTN Approach
SCP
SS7 Signaling Network
Signaling
Class 5
Switch
Class 4
Switch
Most service logic in
local switches, rest in
SCPs
Circuit-based Trunks
64 kb/s digital voice
Typically analog “loop”,
conversion to digital at
local switch
Media stream
• Data travels over a parallel (but separate) network
Class 5
Switch

4. When was the last time you called the phone company just to say, "I am just
calling to say thank you for my phone service being so reliable?"
“The truth is phone companies work to have an uptime of 99.999%”.
Then,
VOIP ???????

5. “Voice over IP (VoIP) defines a way to carry voice calls over an IP
network including the digitization and packetization of the voice
streams. IP Telephony utilizes the VoIP standards to create a
telephony system where higher level features such as advanced call
routing, voice mail, contact centers, etc., can be utilized.”

6. What Is VoIP?
Public Switched
Telephone Network
Initially, PC to PC
voice calls over the
Internet
Gateways allow PCs to
also reach phones
PSTN
(NY)
Gateway
Multimedia
PC
Gateway
IP Network
Multimedia
PC
PSTN
(DC)
…or phones to reach
phones

7. Origins of VoIP
Lessons learned
• Internet Telephony software for multimedia PCs (1995)
• Users frustrated by poor QoS, difficulty of use, lack of interoperability
S ta nd ards a re critical f or s ucces s
Coding/de coding (c ode c) be twe en analog voic e and digi tal packe ts
L oc ati ng the par ty you want to cal l
Signali ng to s et up, m
odify, tear down the voic e c all
Acc es s to ve rtic al ser vi ces (c all forwar di ng, 3-way calling, …)
Gate ways to P N
ST
•
•
•
•
•
•

10. VoIP
Goals and Potential Benefits
• Reduced cost
• Mobility
• Consolidation of voice, data on a single network
• Simplify infrastructure, operations; provide bundled services
• Support for intelligent terminals as well as phones
• Increased flexibility
• Multiple bit rates, multiple media types, richer signaling
• Separation of service control from switching/routing
• Accelerate new service development, increase end-user control, evolve from VoIP
towards advanced services
• Expansion of competition

11. Packet Voice Transport
• Key targets for voice call service quality:
• Average packet loss: < 2%
• End-to-end (lip-to-ear) delay: < 150 ms for comfortable conversation
• Packet loss cannot be corrected by retransmission (TCP), because the
packets arrive too late to be useful
• Use RTP (Real-time Transport Protocol) over UDP (User Datagram
Protocol) for voice or video transport
• Payload ID, sequence numbers, timestamps, monitoring via RTCP
• Packet and buffer lengths limited by constraint on end-to-end delay
• Typical codes: G.711 (64 kb/s), G.729 (8 kb/s) G.723 (~ 6 kb/s)
• Transmitted bit rates depend on overheads, optional silence suppression

14. Enterprise VOIP architecture (2)

15. Wireless VoIP

16. NETGEAR- Skype WiFi Phone
• A mobile WiFi phone that enables you (without a PC) to
make free Internet calls to anyone else in the world who
has Skype.
• Makes calls wherever you have open WiFi access
• Communicates with ordinary phones worldwide for
pennies a minute
• Manages your contact list and displays who's available
to talk
• Designed to deploy Wireless Encryption Protocol
(WEP) for WiFi security.

17. Some standards used in VOIP

18. What is SIP?
“
Session Initiation Protocol - An application
layer signaling protocol that defines
initiation, modification and termination of
interactive, multimedia communication
sessions between users.
IETF RFC 2543 Session Initiation Protocol
”

19. SIP Messages – Methods and Responses
SIP components communicate by exchanging SIP messages:
•
SIP Methods:
– INVITE – Initiates a call by inviting
user to participate in session.
– ACK - Confirms that the client has
received a final response to an
INVITE request.
– BYE - Indicates termination of the
call.
– CANCEL - Cancels a pending
request.
– REGISTER – Registers the user
agent.
– OPTIONS – Used to query the
capabilities of a server.
– INFO – Used to carry out-of-bound
information, such as DTMF digits.
•
SIP Responses:
–
–
–
–
–
–
1xx - Informational Messages.
2xx - Successful Responses.
3xx - Redirection Responses.
4xx - Request Failure Responses.
5xx - Server Failure Responses.
6xx - Global Failures Responses.

20. Simplified SIP Call Setup and Teardown
Proxy Server
User Agent
INVITE
Location/Redirect Server
INVITE
302
(Moved Temporarily)
User Agent
Proxy Server
ACK
INVITE
INVITE
302
(Moved Temporarily)
ACK
Call
Setup
180 (Ringing)
200 (OK)
ACK
Media
Path
Call
Teardown
180 (Ringing)
200 (OK)
ACK
INVITE
180 (Ringing)
200 (OK)
ACK
RTP MEDIA PATH
BYE
BYE
BYE
200 (OK)
200 (OK)
200 (OK)

21. SIMPLE (SIP for IM and Presence)
Simplified Example
lts.ncsc.mil
telcordia.com
Presence
server
Proxy
SUBSCRIBE
peter@telcordia.com
Linda
SUBSCRIBE
NOTIFY
NOTIFY
Proxy
Update
Presence
Peter
Linda subscribes to notifications of changes in Peter’s status:
Off-line, on-line, busy, away, available, ...

22. SIP – Design Framework
• SIP was designed for:
• Integration with existing IETF protocols.
• Scalability and simplicity.
• Mobility.
• Easy feature and service creation.

23. What is H.323?
“
Describes terminals and other entities that provide
multimedia communications services over Packet
Based Networks (PBN) which may not provide a
guaranteed Quality of Service. H.323 entities may
provide real-time audio, video and/or data
communications.
ITU-T Recommendation H.323 Version 4
”

24. H.323 Components
Gatekeeper
Multipoint
Control Unit
Packet Based
Networks
Terminal
Circuit Switched
Networks
Gateway

25. Simplified H.323 Call Setup
– Both endpoints have previously
registered with the gatekeeper.
– Terminal A initiate the call to the
gatekeeper. (RAS messages are
exchanged).
– The gatekeeper provides
information for Terminal A to
contact Terminal B.
– Terminal A sends a SETUP message
to Terminal B.
– Terminal B responds with a Call
Proceeding message and also
contacts the gatekeeper for
permission.
– Terminal B sends a Alerting and
Connect message.
– Terminal B and A exchange H.245
messages to determine master slave,
terminal capabilities, and open
logical channels.
– The two terminals establish RTP
media paths.
Terminal A
Gatekeeper
Terminal B
1. ARQ
2. ACF
3. SETUP
4. Call Proceeding
5. ARQ
6. ACF
7.Alerting
8.Connect
H.245 Messages
RTP Media Path
RAS messages
Call Signaling Messages
Note: This diagram only illustrates a simple pointto-point call setup where call signaling is not routed
to the gatekeeper. Refer to the H.323
recommendation for more call setup scenarios.

26. Some VOIP Service providers

27. sult,
…as a re
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to fall
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expected
use Skyp
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an 41 M
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n or 1
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lazed a eek (30 May
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e has iness W
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s struck
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ström the
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2005)
again”
(30 May
ss week
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mbent
od of incu
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nc
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complace
, Daiwa (2
mes Enck
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2005)
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ee. It’
s a ph
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ewswi
re (28
April
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orld
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ost
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vira downl
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ecom ads an
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rk (1
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ry 2
005
)
“Better quality at no cost”
Jason Donahue, Meiosys (30 May 2005)
To G
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ece
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no ex
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Jeff Pulver
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y
“Every now and then a company [Skype] comes along
with an idea that’s not only good and marketable but
that captures the spirit of the moment”
FierceWireless (2005)

28. “Distributed Peer-to-Peer Overlay approach for IP
Telephony”

29. With very rich functionality
Send any kind of file
Find other Skype users
Global Directory
Make conference calls
Instant Messaging
Online Presence
Groups ($)
Wallet ($)
Contact list
Voice content market ($)
Call any phone ($)
Expressive Content ($)
Get calls from any phone on
your Skype client ($)
Forward calls to any
number ($)
Video
Leave voicemail ($)

31. With a fast-growing ecosystem
Voice Content
Marketplace
Digital Goods
Marketplace
1000+
Developers
200+ Hardware
devices labeled as
Skype-compatible
30+ partnerships
with world-class
companies
10,000+ Affiliates
150+ Skype-enabled
Applications

32. Example(2)

33. Example (3)

34. VOIP PHONES: Five of the most interesting IP telephones for VOIP

35. Top Economic and Technical Challenges for VoIP Deployment
- Which are the most critical?
Consumer
Subscription
Development/Deploy
ment
Revenue Assurance
Taxation
QoS
Standards (IETF, ITU,
ANSI/ATIS)
E911
Security
Lawful Surveillance
0.00%
10.00%
20.00%
30.00%
40.00%

36. VoIP Security Issues
VoIP…….
• Adds new access points to the corporate network
• Adds new devices that can be attacked or used to launch attacks
• Adds new protocols to be used to launch threats
• Adds a new channel for blended threats…

37. VoIP Security Axioms
• Voice networks are targets
• Data and voice segmentation is key
• Telephony devices don’t support
confidentiality
• IP-phones provide access to datavoice segments
• PC-based IP phones require open
access
• PC-based IP phones are
especially susceptible to attacks
• Controlling the voice-to-data
segment interaction is key
• Establishing identity is key
• Rogue devices pose serious
threats
• Secure and monitor all voice
servers and segments

38. VoIP Security Challenges
• Quality of Service (QoS)
• Latency
• Jitter
• Packet loss
• Security Breaches
• Access
• Disruption
• Confidentiality and privacy
• Network Elements
•
•
•
•
•
•
Denial of Service (DoS)
Power failure
Viruses, Trojan Horse
Physical security
Operating System
Life and Safety (E-911)
• 802.11
• Protocols
• H.323
• SIP

39. Issues in accessing emergency services
• Identify call as emergency call (large number of different national emergency
numbers)
• Information on the location of the caller.
• Routing emergency call to the appropriate emergency center.
• Delivering call with CLI and providing call back possibility.

41. Future Vision….

42. My Guess at the future:
• High speed wireless access
• Collaboration Age
• SIP trunks from carriers
• Large scale adoption of video
• Telecommunications Mega-Mergers
• IP TV
• P2P-SIP Hybrid Model for VoIP
• SIP Growth
What do you think ?

43. Questions…
Kiitos!!!!