Voice over IP

1
Voice over IP

• Presenter Tony Hutchinson
• System Engineering Manager

2
Agenda

• Executive Summary
• History
• Business Case
• Services
• Convergence
• Infrastructure
• Challenges

3
Executive Summary
4
Agenda

• Executive Summary
• History
• Business Case
• Services
• Convergence
• Infrastructure
• Challenges

5
History

• There has been much experience learnt in 100
  years
• Some is so common place, it has been forgotten
• With IP some of these lessons need to be
  re-learnt
• Echo was previously just louder side-tone
• Added delays now affect conversation quality
• Network Clocks were previously well defined
• Data path wasnt lossy, with potential gaps in
  speech

6
Agenda

• Executive Summary
• History
• Business Case
• Services
• Convergence
• Infrastructure
• Challenges

7
Business Case

• So why all this interest in IP? Isnt it just
  another transport medium?
• Yes, it is another transport medium
• Its also connectionless
• Doesnt have to be constrained to a physical
  location
• Path between two user points is not pre-defined
• Bandwidth is only consumed when needed
• Its also a transport alternative to the long
  haul carriers such as ATT
• But The long haul carriers are already carrying
  data traffic in their large networks (at a lower
  cost)
• So, send voice as data and pay less!
• Moores Law
• Cheaper Processing
• More readily available

8
Business Case

• So why deploy IP rather than TDM?
• Easier and cheaper maintenance Integration of
  data and voice onto one network
• Lower operating costs Integration of remote
  offices over a common corporate data network,
  rather than through PSTN. Single Dial Plan.
• Access from anywhere Power users such as
  Teleworker and sales Road Warrior. Global
  Access
• Lower product costs Integration of a voice
  application onto a central server, e.g. voice
  mail, means reduced number of devices. The remote
  sites no longer need their own local VM.
• Security and resiliency In NY (September 11th)
  the IP infrastructure kept running the PSTN
  didnt
• Future applications will be data centric, e.g.
  Presence
• Displacement of current TDM systems and businesses

9
Business Case

• But there are still reasons for both IP and TDM
  to live together
• Legacy devices are still going to be around (for
  some time) and people will still use these
• TDM is still likely to be the connection to the
  PSTN
• Most businesses have a directory number via the
  PSTN. Not all have a fixed IP address.
• Businesses are looking for migration and backup
  to their current systems

10
Business Case

• But the cost benefits and advantages to the users
  means that many businesses are looking to migrate
  within a number of years.
• By 2010 the US market is expected to be worth
  US12Billion (Globally in excess of 32Billion!)
• Thats a big market, and competition is fierce!

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Agenda

• Executive Summary
• History
• Business Case
• Services/Content
• Convergence
• Infrastructure
• Challenges

12
Services/Content

• What services are people looking for?
• Basic hook-switch and dial tone
• Call handling features
• Advance features such as call centres, agents
• Remote location, e.g. Teleworker, Remote Agent
• Networking between sites
• Virtual Private Networks
• New features such as voice recognition
• Integration with current applications such as
  customer accounts, hotel registration, etc.
• Business Process Improvements

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Services/Content

• Today the industry is comfortable at the level
  of V1 applications
• Biggest features are Toll Bypass and Networking
• Early adopters are now taking V2 and V3
  applications
• Applications that allow remote users and dont
  require access to the office
• Remote ACD, help desks, etc
• Road Warriors - Sales
• Service Personnel

Affect on business
14
Services/Content

• Centralized Unified Messaging
• Globally Accessible
• Integrates with E-mail and mobile services
• Presence and call routing
• Integration with Microsoft Live Communication
  Server and global corporate directory
• Redirection of calls based on time, availability
  and caller to different end points
• Fixed Mobile Convergence
• One number - able to pick up calls at desk and
  mobile, or alternative number
• Switchover between mobile carrier and in-house
  Wireless LAN

• ACD and call routing
• Service is handled by same agent to give more
  personalized service
• Agents located globally - full language support
• Speech Recognition
• Redirection of calls based on user spoken words
• E-Business
• Workforce is distributed, and mobile.
• Inventory tracking, e.g. RFID tagging
• On phone Advertising, e.g. hotel

Business Process Improvement
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Agenda

• Executive Summary
• History
• Business Case
• Services
• Convergence
• Infrastructure
• Challenges

16
Convergence

• What do we mean by convergence?
• Combining of different worlds
• Different mindsets and cultures
• Different set of standards
• And why now?
• Processing power is cheaper - Moores law!
• Phones have more power today than early PCs
• PCs and phones are standard desktop tools
• Voice and data networks can be combined to ONE
• Phones can now interact directly with data devices

17
Convergence

• Four main business areas are converging
• Voice, TV, VPN and Data
• Triple Play
• Broadcast TV - 100 users
• Telephony - 100 users
• Internet - 40 users and up
• Voice is still the biggest revenue earner
• Incumbents need to grow and expand
• New players also want to grow, and replace the
  last mile of copper
• Cable TV now offers IP connectivity, how long
  before it offers voice?

Courtesy ATM Forum
18
Convergence
Replacement of Local Loop
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Convergence

• Convergence in the network is unseen by the
  user.
• What does the user see at the access point?
• Two line jacks into ONE?
• In reality, once installed, building wiring
  isnt removed
• On new installations, its cheaper to pull too
  many wires, than not enough

?
Integration of Services
20
Agenda

• Executive Summary
• History
• Business Case
• Services
• Convergence
• Infrastructure
• Challenges

21
Infrastructure

• What are the building blocks of the system and
  how are these connected?
• Common Architectures and voice media paths
• Signalling Protocols
• Network Interconnections

22
Infrastructure

• The voice media paths and switching define the
  type of system. Three main types are defined
• IP Enabled PBX
• Here a line card is simply replaced by an
  Ethernet card. Voice switching is done in TDM.
  This is not scalable and adds unnecessary delay.
• Hybrid PBX
• TDM and IP are handled equally, only traversing a
  gateway when IP and TDM devices need to connect.
• Typical in an SME/Enterprise environment
• IP-PBX
• All switching is done in IP. TDM connections are
  generally only to the PSTN via external gateway.
• Model used for Hosted services (IP-Centrex)

23
Infrastructure

• Basic VoIP system building blocks
• Gateway between IP and TDM
• Media Gateway Controller
• Call Control
• Features and Services
• End users
• Different protocols use different names, but
  functions are essentially the same
• Peer to Peer or Central Control?
• Central is good at resolving resource conflicts
• Peer to peer is resilient to network failure
• SIP can handle both aspects

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Infrastructure

• Signalling Protocols are numerous and include
• H.323
• SIP
• MGCP/Megaco
• Proprietary
• Why so many Signalling protocols?
• Different starting perspectives of the
  requirements
• They all offer some advantage for different users
• Most are evolving as new features start to roll
  out

25
Infrastructure

• H.323
• Overview specification and includes
• H.225 - Signalling
• H.245 - Media streaming
• TCP/IP and RTP/UDP/IP
• One of the early protocols
• Standards based, uses current ISDN technology,
  works well for interoperability between vendors
• Features are basic, but well proven
• Centralised call control, based on known proven
  techniques, call state aware
• Slow to evolve
• Difficult to scale to millions of users
• Central call control single point of failure
• Telephone routing biased rather than at
  application level

26
Infrastructure

• MGCP/MEGACO
• MGCP was initially a proposal to IETF for a
  stateless gateway protocol, it has similarities
  to H.323, and has the ability to evolve
• Combined forces with ITU to create MEdia GAteway
  COntrol
• Similar to H.323 in content, but reduced
  messaging
• New standard and evolving
• Allows central and distributed call control
  access to a gateway
• Was thought to be the front runner with
  Enterprise business but little is heard
• Difficulties again in scaling from a global view.
  Different gateways need different controllers
  which need to intercommunicate.

27
Infrastructure

• SIP (Session Initiation Protocol), RFC2543
• More Client Server based and allowing Peer to
  Peer interaction.
• Call control can be distributed
• End devices need to be more intelligent than
  simple phones
• Has the ability to evolve quickly, and scale to
  large numbers
• Simple protocol, but lacks certain PBX
  capabilities
• Vendor specific options provide features
• Inter-vendor working is usually determined
  through bake-off but improving as more vendors
  implement agreed solutions
• Networking features low, but improving
• Open Standards through IETF, agreed by many
  established industry leaders
• Continual proposal of new features and extensions
• SIP is the Internet Phone signalling protocol of
  choice

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Infrastructure

• Local network
• Local network management
• Common single address space
• Local QoS control
• One administration

• Global network
• Mixture of local and global adress spaces
• IPv4 Network address translation
• No guarantee of QoS
• Many global administrations

29
Infrastructure

• Firewalls
• Used to keep out unwanted access
• Restricts flow of data both ways, including voice
• Network Address Translation (NAT)
• Maps many internal private addresses to limited
  number of public Internet IP addresses
• NAT is application agnostic
• VoIP media and signalling may include internal
  private IP addresses in messages which will be
  confusing externally in public IP space
• Application Level Gateway (ALG)
• Stateful and knowledgeable of protocol, e.g. SIP
• Can translate private/public addresses within
  messages

• NAT and IPv6
• NAT and ALG will not be needed
• Any device can access any other device in both
  public and private address space
• Truly global access- one large address space

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Infrastructure
SIP Trunk Gateway
SIP ALG
SIP ALG
Border Gateway
SIP ALG

• Architecture of SIP in a large carrier deployment
• SIP ALG provides IPv4 NAT and firewall functions
  for SIP

31
Infrastructure

• With IPv6 all devices can be addressed globally
• Removes need for NAT and SIP Proxies (ALG),
  making global connections possible
• For example call control in NA, gateway in Asia,
  IP phone in Europe!
• SIP is becoming an accepted global standard for
  IP media device signalling
• SIP and IPv6 have the potential to become
  disruptive technologies in displacing the current
  (TDM) telephone network systems

32
Agenda

• Executive Summary
• History
• Business Case
• Services
• Convergence
• Infrastructure
• Challenges

33
The ChallengesMany!

• There are many
• Voice Quality
• Delay, lost data, jitter, echo
• Network issues, non deterministic, connectionless
• Bandwidth, packet overhead, queue delays
• Clock synchronisation
• Security
• Emergency Location E911
• IP address space
• All of these aspects need to be tackled from a
  System view
• e.g. End points need to use the same media format
• e.g. Security only works if applied globally

34
The ChallengesVoice Quality - Metrics

• To a User - Its a Phone!
• Voice Quality Metrics
• Toll Quality
• Mean Opinion Score (MOS) of 4.0 or better
• E-Model with R80 or better
• Output based on many inputs
• Delay
• Levels
• Echo
• Background noise
• CODEC

R88
Continued Voice Quality is expected
35
The ChallengesVoice Quality- Delay and Loss

• Voice Quality
• With good echo cancellation techniques
• End to end delays of 150ms are tolerable
• 1 packet loss with good Packet Loss Concealment
  is also tolerable
• Jitter only becomes significant when it results
  in packet loss
• Jitter buffer balance between adding delay and
  introducing packet loss

Note Above 200ms an additional 20ms delay is
worse than 1 packet loss with PLC.
Some Delay is tolerable
36
The ChallengesVoice Quality - Echo
Echo is always present, even in TDM Delays in IP
make this more noticeable
Control of Echo is important
37
The ChallengesVoice Quality - Delay

• Lets look at where delay occurs
• Fixed Delays in CODECs and filters
• Packet size delays to build a packet
• Jitter Buffer
• Network (which also introduces jitter)

Control of Delay is important
38
The ChallengesNetwork Jitter

• Where does jitter come from?
• Waiting for larger packets to transfer
• Lack of Priority means all data is treated
  equally - First in First out
• Use MTU to break up large packets and network
  priority for voice

Use QoS settings to minimize voice jitter
39
The ChallengesNetwork Jitter

• Removal of jitter
• CODECs run at a constant rate
• Too much or too little will result in a gap
• Small gaps in voice are not discernable lt60ms
• Small gaps in tones are discernable
• Jitter Buffer needed Leaky Bucket
• Packet Loss Concealment hides loss
• fill gaps with noise, silence
• remove data in fixed size, during silence

Jitter Buffer Leaky Bucket PLC Hides lost
packets
40
The ChallengesClock Slip

• Clock Slip
• The CODEC at each end may run at 64kbits/s, but
  they have a tolerance
• There is no synchronization need to add or drop
  data
• Suppose two device, each at 50ppm
• Thats 100 bits drift in 1 million bits, or
• 8 bits in 80,000 bits which 1.25 seconds _at_
  64kbits/s, or
• 1 packet (160 bytes) every 3 minutes, 20 seconds
• Clock slip buffer needs to consider this drift up
  and down
• Often, slip correction is included with jitter
  buffer control to minimise media delays and
  complexity of multiple buffers

Clock Slip needs to be considered
41
The ChallengesTransmitting Tones

• Transferring tones is problematic if jitter
  buffer discards
• A DTMF tone need only be 75ms long. Losing 20ms
  from this is significant, results in
• No digit being detected, or double digits
• Big deal? Well 91 gets you out of a PBX, double
  digits get you 9911, I.e. emergency services!
• DTMF information can be sent in-band as an RTP
  datagram using RFC2833
• Call Progression tones can also be sent as
  descriptions using RFC2833
• (New standards RFC4733 and RFC4734 supercede
  RFC2833)

RFC2833 ensures DTMF tones are transferred
correctly
42
The ChallengesFAX and Modem

• In band tone transmission
• Other devices use in band tone, such as
• FAX and MODEM
• FAX will work, but only under very controlled
  network conditions, such as packet loss
• MODEMs will work, but again under controlled
  conditions such as echo cancellation
• Alternative CODEC for FAX is T.38 (and less often
  T.37)
• Alternative CODEC for MODEM (V.150) is under
  investigation
• Proposals have been made, but due to complexity
  there is currently little enthusiasm to include
  this in gateways.
• Limited (proprietary) solutions are available.

FAX and MODEM need alternative CODECs
43
The ChallengesPacket Size

• How big a packet should be used?
• Consider bandwidth use with different payload
  size and overhead
• 10 to 50ms is a good size to use for voice
• Below 10ms more bandwidth for payload is needed
• Above 50ms voice delays cause quality issues
• Good compromise is 20-30ms, many people fixing on
  20ms.
• Some administrations using 10ms to decrease
  user-user delay
• Other issues also appear
• Smaller packets mean more Packets Per Second
  (PPS)
• Wireless connections, especially WiFi, have
  difficulty with high PPS rates
• Preference is for larger packets, but this adds
  more voice delay

20ms Packets - Good Compromise
44
The ChallengesCODEC

• So many CODECs, which one to choose?
• G.711
• This is the base level, so must be in
• G.726
• Good voice quality, but limited bandwidth
  reduction
• G.729, G.729a, G.729ab
• Good reduction in bandwidth, with good voice
  quality
• 729a is reduced MIPS in conversion
• 729ab only sends with voice activity, so even
  less bandwidth, but voice may be clipped
• Wideband (G.722 and others)
• Works especially well for conferences, offering
  8kHz voice Bandwidth

Balance of Voice Quality and Bandwidth usage
45
The ChallengesBandwidth

• How much bandwidth needed?
• Payload
• 160 Bytes with G.711
• 20 Bytes with G.729
• 81 compression in payload
• Overhead RTP, UDP, IP, MAC and Ethernet
  interpacket gaps (dead space that cant be used)

G.711 100kbits/s G.729 40kbits/s
46
The ChallengesSecurity

• Security
• How accessible is the equipment
• Put a lock on the door!
• How robust is the system to attack, DOS?
• Harden system to cater for fault conditions as
  well as normal operation.
• Authentication (Who is this?)
• Authorization (Is this action allowed?)
• Encryption (You cant see this, well not easily)
• Integrity (Did someone tamper with this?)
• Phreakers gaining access for free calls, or
  charging others
• Provide separate access, e.g. separate physical
  connection
• Remove backdoors
• Ring-back on MODEM

Lock the Door!
47
The ChallengesSecurity

• Security
• Monitoring and substitution of voice
• UDP has no ACK/NACK, can be substituted,
  redirected
• Encryption, use of public and private keys
• DES, DES-3, RC-4, AES, SSH, SSL, IP-SEC, etc.
• Legal issues and Intellectual Property in
  distribution and use of encryption
• Access through firewalls
• Open up ports, but this makes it look like a pin
  cushion
• Use a Session Border Controller, or Application
  Level Gateway
• This is a proxy that controls access around
  firewall boundary and translates between internal
  and external devices, e.g. SIP proxy (dedicated
  function and more secure than a simple firewall
  )
• VPN between sites, but not to Internet direct

But doors keep things in as well as out
48
The ChallengesRules and Regulations

• E911 (Emergency Location)
• E911 requires that a person making an emergency
  call can be physically located within a
  pre-defined area
• IP phones can move and be located globally
• These requirements are potentially in conflict
• New standards and regulations are evolving to
  maintain this capability
• Similar standards are now being discussed in
  Europe
• CALEA
• Call Tracing, Malicious call handling
• Wiretapping
• Charging for services
• Who pays? The Internet is free But, is it?

Local and Global rules need to be applied
49
The ChallengesIPv6

• IPv4 Public Address
• The current public address range is running out
• Main users are NA and Europe
• Not enough for the remainder of the world
• IPv6 Public Address
• Driver 3G wireless, internet connected
  appliances
• Already being deployed in a number of countries,
  including
• China
• Japan
• India
• Australia
• A number of European Countries

IPv6 is here! IPv4 is running out
50
Finale

• VoIP is now mainstream
• Business Process Improvement, rather than
  networking and toll bypass
• Technical challenges for voice quality are being
  overcome
• The large Telecos are changing to embrace the IP
  changes
• SIP is becoming a common communication method and
  feature interaction between vendors is improving
• IPv6 is being implemented to provide truly global
  communications
• SIP and IPv6 are disruptive communication
  technologies
• Many business and global changes expected because
  of these
• Thank You

51
Bibliography

• Thanks to the following for information used in
  the presentation
• MITEL Networks
• Infotech End user primary research report,
  2002
• Gartner Research Bob Hafner report, July 2003
• World Bank Group The drives of the information
  revolution
• ATM Forum presentation at MPLS, 2001
• http//bgp.potaroo.net/, http//www.ipv6forum.org
• More detailed reading
• Delivering Voice over IP Networks, Daniel and
  Emma Minoli, ISBN 0-471-25482-7
• IP Telephony (HP Professional Books), Bill
  Douskalis, ISBN 0-13-014118-6, www.hp.com/go/retai
  lbooks