Voice Services over an IP Network

1
Voice Services over an IP Network

• By
• Dr. James G. Williams

2
4 Basic Technologies for VoIP

• Signaling - Call Setup
• Encoding - A/D and Quantising
• Transport - Transmission and Switching/Routing
• Gateway Control - Media Device Control
• Application Software
• Session Software

3
Standards

• Signaling - H.323 (ITU) AND SIP (IETF)
• Encoding - G.711 PCM (64000 kbps), G.722 (ADPCM),
  G.726, G.727, etc.
• Transport - RTP (Real-Time Transport Protocol
  transport voice samples), RTCP (Real-Time
  Transport Control Protocol feedback on
  Quality), RTSP (Real-Time Streaming Protocol)
• Gateway Control - MGCP (Media Gateway Control
  Protocol), H.GCP, IPDC

4
2 Major Scenarios

• Private Network, No PSTN but with or without
  Internet
• Private Network with PSTN

5
Basic Components for VoIP
H.323 Gateway e.g. Cisco 3600
H.323 Gateway e.g. Cisco 3600
H.232 Terminal (Telephone or PC)
H.232 Terminal (Telephone or PC)
Private Network
Internet
6
Call Processing

• Caller goes off hook-detected by gateway
  application
• Session issues dial tone
• Session waits for dialed digits
• Session matches dial plan pattern
• Session maps called number to an IP host to route
  to destination (may be itself)
• Session runs the H.323 protocol to establish a
  transmission and reception channel over the IP
  network
• If RSVP used, RSVP reservations are attempted to
  achieve QoS

7
Call Processing

• The CODECS (Coders and Decoders) are activated
  with parameters (Samples analog voices converts
  to digital - G.711 samples 8000 times per second
  and produces 8000 8 bit bytes 64000 bits)
• If duration of voice in a packet is 20ms, then 50
  (1280 bit) payload packets per second
• Protocol stack is RTP - UDP - IP

8
Call Processing

• Any Call Progress indicators are cut through the
  voice path as soon as audio channel established
• Signaling detected by voice ports after call
  setup are trapped by session layer and carried
  over the IP network by RTCP
• When either end hangs up, connection is torn down
  (any RSVP resources)

9
The Business Plan

• What Offerings (services, products)?
• Who are the customers?
• Who is the competition?
• How will the services be delivered?
• What technologies can be utilized?
• What is the cost of delivering service?
• What resources are required to deliver and
  support the services?

10
The Business Plan

• What system architecture is required?
• What processes, functions, procedures, etc. are
  needed?
• What are the capacities and volumes of the
  resources needed?
• What Financial Resources are Needed?
• The Economic Model

11
Company Background

• Competitive Local Exchange Carrier
  (CLEC)/(Telephone Company)
• 3 Venture Capitalists - 62 Million
• 1 Finance Company - 120 Million
• 16 markets (cities) East Coast USA
• 8 Founders
• Estimated 400 employees

12
Company Background

• New Generation Network
• Broadband Services to Businesses
• Small to Medium (6 50 employees)
• Underserved Markets
• DSL to the Premise (VoIP)
• ATM backbone (VoATM)
• All Digital Packet Switched Network to the PSTN
• Offices in each city fully staffed
• Sales (15), Customer Care(3), Technicians(3)

13
Technology Architecture
Telephone
4 16 port IAD at Customer Premise
Fax
PC/ Hub/ Router
Local Loop
ILEC Central Office
LSO with a 720 Port DSLAM (Digital Subscriber
Line Access Multiplexer)
1Central Office per market
PSTN
45 155 Mbps
Digital Switch Pathstar/5-ESS
Voice
PSAX ATM Router
GR303
ATM
911 Center
Data
Springtide Router
ILEC Central Office
LSO
NOC Network Alarms and SNMP Packets
Other Market PSAX NOC Data
Internet
14
Services

• Voice Services
• Local
• Long Distance
• Voice Mail
• Features (Call Forward, Caller ID, etc.)
• PBX and Keyset Support
• Calling Cards
• Data Services
• Internet Access (386 kbps to 2.3 mbps)
• VPN
• Email Web Hosting

15
Voice Requirements

• 7X24 service availability
• IAD must have UPS
• DSLAM must have UPS
• PSAX must have UPS
• Switch 7RE (5ESS) must have UPS
• Need fault tolerant devices
• Network Operations Center (NOC)
• Access to every component via IP network
• Uses SNMP (Simple Network Management Protocol) to
  configure and reconfigure devices via the MIB
  (Management Information Base)
• Receives Alarm messages from devices based on
  threshold settings for triggers
• Ability to test circuits (Lucents LoopCare)

16
Voice Requirements

• Quality of Service (QoS)
• Latency is critical for voice, not data
• Local loop bandwidth considerations
• Voice without compression requires 128Kb (64Kb
  for each direction)
• Maximum bandwidth is determined by length of loop
  from LSO (SDSL 18,000 ft. Max) and quality of
  the loop
• No load coils and bridged taps permitted
• Reliability
• Dial Tone always there
• Same actions, same results

17
Customer Path
IOF Circuit Terminations, IDs, Type, Channels
Central Office
LSO Facility
PSAX Slot, Port, Voice VPI/VCI, Data VPI/VCI
Pathstar Port Voice VPI/VCI IP Addresses
Stinger-DSLAM Shelf, Slot, Port, Voice
VPI/VCI, Data VPI/VCI
Springtide Port IP Address
3-COM ID Mail Accounts
ILEC Circuit (IDs, Vendor)
IP Addresses, Voice VPI/VCI, Data
VPI/VCI, Telephone Numbers, Host IP Addresses
IAD
Host PC
Telephone
Customer Premise
18
Other Players

• ILEC (Incumbent Local Exchange Carrier)
• Own local loops
• Own Telephone Numbers
• Own the Customer
• IXC Inter-exchange Carriers (Long Distance)
• 911 Emergency Management Interface
• CMDS (national database)
• Caller ID (LIDB national database)
• Ported Numbers (national database)
• 800 Numbers (national database)

19
CLEC TO BALOCAL
Call Direction
LOCAL/TOLL TRUNKS
CLEC EO
BA EO
TST
or
DT

• Usage Billing Concept
• Reciprocal Compensation

• BA Bills CLEC - Usage
• Local charges for MOUs
• TANDEM
• or
• END OFFICE

• Factors Exchange
• Required
• CLEC to BA
• PLU Factor

• BA Bills CLEC - Facilities
• Tandem Switched Transport (TST)
• Entrance Facility or Cross Connect
• Direct Trunked Transport (DT)
• Entrance Facility or Cross Connect
• Channel Milage (EO to EO)

Record Exchange Required NONE
20
CLEC TO BAINTRALATA TOLL
Call Direction
LOCAL/TOLL TRUNKS
CLEC EO
BA EO
TST
or
DT

• Usage Billing Concept
• Switched Access

• Factors Exchange
• Required
• CLEC to BA
• PLU Factor

• BA Bills CLEC - Usage
• Tandem Connection
• Local Switching
• Tandem Switching
• Tandem Transport
• Fixed
• Per Mile
• RIC
• CCL
• End Office Connection
• Local Switching
• RIC
• CCL

• BA Bills CLEC - Facilities
• Tandem Switched Transport (TST)
• Entrance Facility or Cross Connect
• Direct Trunked Transport (DT)
• Entrance Facility or Cross Connect
• Channel Milage (EO to EO)

Record Exchange Required NONE
21
BA TO CLECLOCAL
Call Direction
LOCAL/TOLL TRUNKS
CLEC EO
BA EO
TST
or
DT

• Usage Billing Concept
• Reciprocal Compensation

• CLEC Bills BA - Usage
• Local Termination charges
• for MOUs in accordance with
• CLEC tariff/agreement.

• Factors Exchange
• Required
• BA TO CLEC
• PLU Factor

• CLEC Bills BA - Facilities
• Tandem Switched Transport (TST)
• Entrance Facility
• Direct Trunked Transport (DT)
• Entrance Facility

Record Exchange Required NONE
22
BA TO CLECINTRALATA TOLL
Call Direction
LOCAL/TOLL TRUNKS
CLEC EO
BA EO
TST
or
DT

• Usage Billing Concept
• Switched Access

• CLEC Bills BA - Usage
• Switched Access Charges
• for MOUs in accordance
• with CLEC Tariff/Agreement.

• Factors Exchange
• Required
• BA to CLEC
• PLU Factor

• CLEC Bills BA - Facilities
• Tandem Switched Transport (TST)
• Entrance Facility
• Direct Trunked Transport (DT)
• Entrance Facility

Record Exchange Required NONE
23
CLEC TO AN IXC
Call Direction
IXC SUBTENDING OZZ/CIC
FGD/B
CLEC EO

• Usage Billing Concept
• Switched Access
• Meet Point Billing
• Multiple Bill/Multiple Tariff

• BA Bills IXC - Usage
• Tandem Switching
• Portion of Transport
• CLEC Bills IXC - Usage
• Switched Access Charges
• for MOUs in accordance
• with CLEC tariff/agreement.
• CLEC Bills BA - Usage
• Not Applicable

Factors Exchange Required IXC to CLEC - FGD
Factors

• Record Exchange
• Required
• CLEC makes originating
• record
• CLEC to BA
• EMR 115002

• BA Bills CLEC - Facilities
• Tandem Switched Transport (TST)
• Entrance Facility or Cross Connect

24
IXC TO A CLEC
Call Direction
IXC SUBTENDING OZZ/CIC
FGD/B
CLEC EO
Factors Exchange Required IXC to CLEC - FGD
Factors

• Usage Billing Concept
• Switched Access
• Meet Point Billing
• Multiple Bill/Multiple Tariff

• BA Bills IXC - Usage
• Tandem Switching
• Portion of Transport
• CLEC Bills IXC - Usage
• Switched Access Charges
• for MOUs in accordance with
• CLEC tariff/agreement.
• CLEC Bills BA - Usage
• Not Applicable

• Record Exchange
• Required
• BA to CLEC
• EMR 110101
• CLEC to BA
• EMR 115002

• BA Bills CLEC - Facilities
• Tandem Switched Transport (TST)
• Entrance Facility or Cross Connect

25
CLEC TO CLECLOCAL
Call Direction
LOCAL/TOLL TRUNKS
(Originating)
(Terminating)
CLEC EO
CLEC EO
Factors Exchange Required

• BA Bills Originating CLEC - Usage
• Transit Service Charges
• Recovery of Local Termination charges
• for MOUs paid by BA to Terminating CLEC.
• Terminating CLEC Bills BA - Usage
• Local Termination charges
• for MOUs in accordance with
• Terminating CLEC tariff/agreement

• Usage Billing Concept
• Transit Service

Record Exchange Required 11-01-01 to NYSP NYSP
bills Originiating CLEC for Transit
Service Charges
26
CLEC TO ITCLOCAL/INTRALATA
Call Direction
LOCAL/TOLL TRUNKS
FGC-LIKE TRUNKS
ITC EO
CLEC EO
MP
Factors Exchange Required NONE

• Usage Billing Concept
• Transit Service
• Meet Point Billing

• BA Bills CLEC - Usage
• Tandem Switching
• Tandem Transport
• - Fixed
• - Per mile from SWC to MP
• Independent Bills CLEC - Usage
• Charges for MOUs in accordance
• with tariff/agreement.

• Record Exchange
• Required
• BA to ITC
• - 110101
• ITC to BA
• - 115002

CLEC and Independent must have billing agreement.
ITC subtends a BA Access Tandem
27
CLEC TO ITCLOCAL/INTRALATA TOLL
Call Direction
MP
ITC EO
CLEC EO

• Usage Billing Concept
• Special Access

• BA Bills CLEC - Usage
• Channel Termination
• Channel Mileage
• - Fixed
• - Per mile from SWC to MP
• ITC Bills CLEC - Usage
• Charges for MOUs in
• accordance with CLEC
• tariff/agreement.

Factors Exchange Required NONE
Record Exchange Required NONE
Direct Trunk - ITC and CLEC could utilize
2-way. CLEC and Independent must have billing
agreement.
28
Billing (Arbor/BP)
Pre-Sale System (BroadStreet)
Order Management System (Arbor/OM)
Provisioning (Dset, BA)
Customer Care (Arbor/BP)
Financial Accounting System
Internet, Intranet, Extranet
E911, PIC/CARE Number Portability Other
Interfaces (Arbor/BP)
Payroll (Payroll One)
Web Site
Human Resource System (Employease)
Help Desk Trouble Ticket (Remedy)
System Components
29
Customer Inquiry
Customer Account Maintenance
Prospects, LSOs, Employees, Inventory, Maps,
Regulatory, Competition, etc.
ILEC, IXC Revenue and Payments
GL, AR, AP, Assets, Purchasing, etc.
Payroll
Arbor/BP Customer Care
Pre-Sale System
Analysis
Financial Accounting System
Services Rates Discounts Formats
Human Resources
Sales System Order Data
Network Monitoring Fault Management
Arbor//BP Billing
Customer Intelligence
Arbor/OM
Commissions
Contract, Letter
Databases
Arbor/OM Remedy Trouble Ticket
ILECs, CLECS, IXCs
Installation Configuration
Provision E-Bonding
Maintenance Tools LoopCare
Charges, Inventory, Times
BillDats Software
Notifications Customer, Sales
Customer Usage
Back Office System Flow 03/16/2000
ILEC, IXC
30
BackOffice Software Architecture
Trading Partners System Interface (EDI, CORBA)
Software Architecture
SUN SOLARIS O.S.
ILEC Provisioning ILEC Quintessent

Network Fault Management (NFM)
HPUX O.S.
Validation Quintessent
Informix DBMS
iPlanet
Web Server
OM
Arbor/BP
LoopCare
BillDats Sybase DB
Presale Sales
Remedy Trouble Ticketing
Oracle DBMS
Oracle DBMS
DSL line Qualification
Windows 2000 O.S.
Remedy Help Desk
Web Server (IIS)
Financial Asset Management
Mail Server (Exchange)
Desktop Applications
Gis System
SQLServer
BroadStreet Employees
BroadStreet Customers
Public
31
BackOffice Support Architecture
5ESS Switches
Sprint LD
3COM Messaging
CMDS
ILEC/LSR
PIC/Care
Pre-Order
Gateway Server
Mediation Servers
Remote Network Devices
DBMS
Arbor/OM and Arbor/BP Servers
Customer Care
Invoicing
NOC and Provisioning Servers
Remedy Trouble Ticket
Cajun View
Order Entry
Payments
Navis
Product Configuration
Oracle DBMS
Journals
Oracle DBMS
NFM
LoopCare
Ordering and Provisioning Data Capture
911 Service Requests
ILECs Verizon, Etc.
Windows 2000 Servers
Financials
E911
MSAG Data Updates
Desk Top Apps
Remedy Help Desk
Sprint Mgt
Inventory IPs, Tele No. IADs, Stinger
Web Server
Mail Server
SQL Server DBMS
LNP
Internet
Intranet
Extranet
LIDB
Circuits
32
Provisioning Support
Database
Stinger Table Data w- Pre-configured Path Data
Order Management
Order Queue
Update PSAX Table
Provisioning Interface For Stinger,PSAX and Switch
Provisioning Interface for The IAD
Update Circuits Table
Update Switch Table
Update 3-COM Table
Update Calling Cards
Update IAD Table
33
Intranet/Extranet VoIP

• Voice/IP is not expensive, but the initial outlay
  will depend largely on where and to what extent
  the technology is deployed.
• Some sites only want voice/IP for local telephony
  with all externals calls still going over the
  public switched telephone network (PSTN) or over
  a private voice network.
• But more commonly, voice/IP is deployed
  externally with the existing on-site telephone
  infrastructure left intact. In this case, a
  gateway is needed to route a call over a wide
  area IP network.

34
Voice Over IP

• A major technical question is where and how best
  to deploy the gateway function. This will depend
  on factors such as the size of the site, number
  of sites, location of sites, etc.
• While there are serious questions over voice/IP
  reliability and quality, analyst Gartner Group
  predicts that these are likely to fade this year.

35
Voice over IP

• At present, the quality of voice/IP almost never
  exceeds the PSTN and suffers from variability,
  even over private IP networks.
• Technology and standards to provide an end-to-end
  connection and offer guaranteed bandwidth without
  interference from other network traffic are only
  just coming into place.

36
Voice over IP

• Voice/IP is being more widely deployed over
  private IP-based intranets
• Can save money by routing conventional calls from
  existing phones over the IP backbone.
• When virtual private networks are used to carry
  IP-based voice - the quality is similar to GSM
  cellular, but may not be deemed reliable enough
  for talking to customers.

37
Voice Over IP

• London-based marketing agency Rainier implemented
  voice/IP for toll bypass using its virtual
  private IP network for calls between its London
  office and offices in Boston and San Francisco.
• Voice/IP has cut Rainier's transatlantic voice
  communications bill by 75 compared with BT's
  rates.
• The delay, about 15 to 30 seconds, is the time it
  takes to set up the fixed path through the
  end-to-end network, including the component
  provided by the ISP.

38
Voice Over IP

• One problem with using intranets or virtual
  private networks to carry voice is that it can
  become unacceptable during peak periods.
• The ideal solution would be to route calls over
  the PSTN at such times, if only you could tell in
  advance that the quality of service available
  over the IP network was inadequate.
• Networking and telecoms systems vendor Nortel
  Networks has developed a technique for monitoring
  the condition of an IP network for this
  situation.
• A company's Meridian private branch exchanges
  (PBXs) can assess the likely quality of the IP
  network on an ongoing basis by transmitting test
  packets and measuring the transit delays.
• While this delay is kept within acceptable
  bounds, the network is deemed acceptable for
  voice/IP. But if the delay falls outside the
  bounds, calls are re-routed over the PSTN.

39
Voice Over IP

• VoIP has the potential to deliver new
  applications and features not so easy to support
  over the PSTN.
• Web-enabled call centres, where voice/IP will
  enable voice calls to be opened up within an
  existing Internet session.
• Currently, some sites have 'call me' buttons, but
  the call-backs run on a separate line over the
  PSTN which is not useful if only one line exists
  and is already busy during an Internet session.
• Voice/IP will also enrich existing telephony by
  making sophisticated call-handling features more
  readily accessible.
• Modern PBXs have for years come with a huge
  sophistication of features which are largely
  inaccessible because the LCD display on handsets
  is not a useful interface

40
Voice Over IP

• Service providers may offer caller identification
  as a feature
• IP signaling, perhaps combined with caller
  identification, can also be used to facilitate
  sophisticated call conferencing of the kind
  previously only available as a specialist
  service.
• Larger conferences usually require a mediator to
  control admissions to the conference and
  introduce new participants to the others.
• The use of IP signaling combined with the PC
  interface makes it easy to perform these
  functions.

41
VoIP Applications

• On-site IP telephony allowing internal calls to
  be made over IP-based Lans.
• Corporate toll bypass where voice calls are made
  over internal IP networks or virtual private IP
  networks.
• Voice over the Net between two
  multimedia-equipped PCs.
• Fax over the Net. The cost is very cheap, and
  quality is less of an issue because communication
  is not real time and loss of bandwidth simply
  delays transmission
• IP-based public phone services. Carriers can cut
  costs by consolidating voice and data over single
  IP core networks and can deliver new features not
  possible over the PSTN such as advanced
  conferencing
• Call-centre IP telephony. This is a variant of
  voice/IP, but is a distinct application
• Voice messaging over the Internet. The Net can
  become a medium for unified messaging.
• Video-over-IP. This field unto itself is raising
  a variety of unique technical issues.

42
Voice Over IP Gateways
43
VoIP Gateways Increase in Functionality
44
Softswitch
45
SoftSwitch
46
(No Transcript)
47
VoIP Quality

• Bandwidth and transit delay affect voice quality
  during transmission over any communications link.
• Circuit-switched voice and cellular GSM, the
  voice is sampled and converted into bits at the
  rate of 64Kbps. Each sample represents an
  approximation of the sound during its sampling
  period, in this case, 1/8000 of a second.
• On the PSTN, an end-to-end path is set up, and
  this imposes a slight delay which is barely
  noticeable except over satellite links. This
  delay is very consistent and has no effect on
  quality. As the bandwidth is fixed, quality does
  not vary during the conversation.
• With voice/IP , the digital bits obtained from
  the sampling process are first packed into IP
  packets before being transmitted, and this
  imposes a slight up-front delay. But this is not
  an issue unless the voice is packed and then
  unpacked into bit streams during transmissions.

48
VoIP Quality

• IP networks do not normally provide a fixed
  end-to-end path for a whole session nor a
  guaranteed bandwidth.
• This is mitigated by stamping the packets with
  the time they were sent and using buffers to hold
  them for a second or so at the receiving end, so
  that they can be assembled in the right order and
  with the right timing.
• But the delay can only be minimal or else the
  packet will be too late to be of any use. Even
  when there are no serious delays and IP packets
  have a fixed path, bandwidth can be reduced when
  there is a surge in traffic leading to degraded
  quality.
• Instead, everything slows down, and some packets
  have to be discarded to ensure that at least a
  reduced number can arrive on time. The result is
  that there are fewer bits to represent the sound
  at the receiving end and quality degrades.
• The only way to solve these problems is to set up
  fixed paths through the network for the duration
  of a conversation and allocate a fixed amount of
  bandwidth to it. You create a tunnel through the
  network shielded from other traffic.
• This reduces the efficiency of the IP network
  because this tunnel is then reserved purely for
  the voice and cannot be re-allocated to other
  traffic even during periods of silence, until the
  parties hang up.

49
VoIP Security

• Security - a high priority for and company or
  university who relies on its computer networks
  for quick access to private or sensitive
  materials.
• Currently encryption and authentication of user
  access is only a recommendation by H.323. What
  this means is that any H.323 aware user can tap
  into any conversation on the system. And an
  employee or any outside person can monitor every
  conversation with access without ever having to
  leave his or her desk.
• Another security issue arises if a corporation
  uses VoIP technology for a remote access
  location.
• This is one of the main uses for partial VoIP
  implementation today, but it is also a serious
  security risk because of problems with firewalls.
  Currently H.323s firewall negotiation
  mechanisms require direct access into the
  corporate network. A blatant violation of most
  corporations security requirements is the
  call-set up of H.323.

50
Making VoIP Work

• Making Voice over IP function efficiently in a
  corporate enterprise network requires adequate
  bandwidth allocation and management.
• For each call to be sent across an IP network,
  17Kbps is needed of the total bandwidth. If
  properly designed and operated a companys
  network can use a 56 or 64 KBPS link to
  simultaneously share several voice calls and data
  traffic without any delays or problems.
• Whereas when using the Internet, Providers such
  as America on Line (AOL) handle too much Internet
  traffic and rout transmissions too many times to
  provide a clear and precise connection.
• In larger organizations where a large amount of
  data is carried across a network, Voice over IP
  would need a separate infrastructure in order to
  be utilized.
• Especially in companies where up to 50 phone
  lines can be used simultaneously an Intranet type
  of infrastructure will be needed to process the
  calls with PSPN quality.

51
VoIP and Convergence

• Voice, fax, data and multimedia traffic are
  transmitted over a single multipurpose network
• These advantages include
• lower recurring transmission charges,
• reduced long-term network ownership costs, and
• the ability to deploy a wide range of powerful
  voice enabled applications.
• The disadvantages are
• technology professionals are concerned with the
  quality of voice calls on the data network
• the stability of voice-over-IP (VoIP) solutions,
  and
• the consequences of being prematurely "locked-in"
  to a given vendors architecture.
• A lack of expertise and experience with VoIP
  technology
• By using an intelligent multi-path gateway switch
  that links the PBX, the data network and the
  public switched telephone network (PSTN),
  companies can effectively "hedge their bets" even
  as they move ahead with their initial VoIP
  deployments.

52
VoIP Implementations

• PBX-based gateways
• The leading manufacturers of PBX equipment are
  all introducing their own solutions to the VoIP
  challenge.
• These vendors have minimal experience in
  IP-centric data networking.
• Without strong expertise in connectionless,
  non-determinate protocols, it is unclear if they
  will be able to address the issues of voice
  signal quality in the IP world.
• A drawback to this approach is that it is tied to
  highly proprietary PBX platforms with no real
  record in open technical standards.
• Router-based gateways
• Manufacturers of routers and other data
  networking hardware are also attacking the VoIP
  market and have healthy marketshare.
• Their expertise in IP technology should also help
  them in solving voice quality problems using the
  IP quality-of-service (QoS) techniques.
• Their unfamiliarity with voice technology and
  call management hamper their ability to deliver
  corporate-class telephony solutions.

53
VoIp Implementations

• PC-based gateways
• Several vendors are bringing stand-alone gateways
  to market. These products offer a router- and
  PBX-independent solution, since they are not tied
  to a particular manufacturers platform. These
  smaller, more nimble vendors exhibit a greater
  ability to rapidly adopt and even help define
  emerging standards.
• Alternative to the above
• The multi-path switch. These devices are
  specifically designed to address the issues
  unanswered by the product categories described
  above including voice quality, network
  reliability, and vendor independence

54
VoIP SLA

• Service level agreements (SLAs) are also a major
  hindrance for uptake as they tend to be immature,
  making it harder for vendors and carriers to
  overcome potential customers' quality of service
  and security concerns.
• Phil Smith, business development director for
  Cisco, which is investing heavily in VoIP
  technologies, agreed. "It's fair comment to say
  that there is a lot of work to do to educate the
  market, and we're out there trying to do that,"
  he said.
• "SLAs are a particularly tricky area because of
  the sheer number of different players involved in
  the process of providing VoIP services, but I'm
  sure that as the market evolves, these will be
  resolved."
• Analyst group Frost Sullivan estimates sales of
  VoIP gateways at 260m in 2001, set to reach
  2.9bn in 2006.

55
QoS Standards

• Support for QoS routing can be viewed as
  consisting of three major components
• 1. Obtain the information needed to compute QoS
  paths and select a path capable of meeting the
  QoS requirements of a given request,
• 2. Establish the path selected to accommodate a
  new request,
• 3. Maintain the path assigned for use by a given
  request.

56
RFC 2676 QoS Routing

• QoS Routing Mechanisms and OSPF Extensions
• The assumption is that a flow with QoS
  requirements specifies the requirements in some
  fashion that is accessible to the routing
  protocol.
• This could correspond to the arrival of an RSVP
  RZB97 PATH message, whose TSpec is passed to
  routing together with the destination address.
• After processing such a request, the routing
  protocol returns the path that it deems the most
  suitable given the flow's requirements.
• Depending on the scope of the path selection
  process, this returned path could range from
  simply identifying the best next hop, i.e., a
  hop-by-hop path selection model, to specifying
  all intermediate nodes to the destination, i.e.,
  an explicit route model.
• In addition to the problem of selecting a QoS
  path and possibly reserving the corresponding
  resources, one should note that the successful
  delivery of QoS guarantees requires that the
  packets of the associated "QoS flow" be forwarded
  on the selected path.

57
Metrics

• Link available bandwidth
• The link physical bandwidth or some fraction
  thereof that has been set aside for QoS
  flows. Since for a link to be capable of
  accepting a new flow with given bandwidth
  requirements, at least that much bandwidth must
  be still available on the link, the relevant link
  metric is, therefore, the (current) amount of
  available
• Link propagation delay
• This quantity is meant to identify high latency
  links, e.g., satellite links, which may be
  unsuitable for real-time requests.
• This quantity also needs to be advertised as part
  of extended LSAs, although timely dissemination
  of this information is not critical as this
  parameter is unlikely to change (significantly)
  over time.
• Hop-count
• This quantity is used as a measure of the path
  cost to the network. A path with a smaller
  number of hops (that can support a requested
  connection) is typically preferable, since it
  consumes fewer network resources.

58
VoIP Standards

• H.323 suite of protocols for interworking with
  H.323 endpoints.
• This allows the system to seamlessly integrate
  H.248/Megaco-based systems with H.323-based
  voice-over-IP (VoIP) systems. H.323 is also used
  to communicate between third-party softswitches.
• SIP for interworking with SIP endpoints.
• This allows the system to seamlessly integrate
  H.248/Megaco-based systems with SIP-based VoIP
  systems. SIP is also used to communicate between
  third-party softswitches.
• H.248 Megaco device control protocols to support
  the distributed VoIP call control architecture
  needed to scale up for carrier-class deployments.
• SS7 ISUP for seamless PSTN signaling integration.
• SS7 TCAP for seamless integration with
  intelligent network-based services.

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Reminder H.323 Network Elements
H.323 MCU
H.323 Terminal
H.323 Gatekeeper
H.323 Gateway
H.323 Terminal
H.323 Terminal
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Media Gateway Control ProtocolMGCP

• MGCP is designed as an internal protocol within a
  distributed system that appears to the outside as
  a single VoIP gateway.
• It is composed of a Call Agent, that may or may
  not be distributed over several computer
  platforms, and of a set of gateways, including at
  least one "media gateway"
• Media Gateway performs the conversion of media
  signals between circuits and packets, and at
  least one "signalling gateway" when connecting
  to an SS7 controlled network.
• In a typical configuration, this distributed
  gateway system will interface on one side with
  one or more telephony (i.e. circuit) switches,
  and on the other side with H.323 conformant
  systems.