Voice Over Internet Protocol (VoIP)

What is Voice over Internet Protocol? IP Network Conversion of sound into digital signal Encapsulation in IP packet Transport over network De-encapsulation and reconversion of digital signal into sound

This type of voice over IP has been around a long time. Seldom used because the cost of long distance has dropped dramatically – domestic at least Reliability and quality of transmission not high enough for business communications (or even personal use) Difficulty in set up and use

The basic components of VoIP are: Voice Processing Call Processing Packet Processing Network Management

Voice Processing Codec (Coder/Decoder) Echo Cancellation unit Voice Activity/Idle noise detector Tone Detector Tone Generator Facsimile processor Packet voice protocol processor

Call Processing PSTN interface Signaling protocol management Call establishment/teardown Telephone number mapping Feature control Other management functions Maintenance functions

Packet Processing Convert data stream from codec to packet format Compress signals as required –G.711(64Kbps), G.729(8Kbps) for example Adds appropriate transport headers Convert signaling protocols: Telephony to packet signaling

Network Management Performance monitoring Fault detection Accounting Configuration management Security management Directory access Remote access support

What does it take to make VoIP work in a business environment? Variety of set types Much greater functionality is required Interface to the Public Switched Telephone Network is required Much greater attention must be paid to network performance in order to provide an acceptable level of service

VoIP Telephone Sets IP “Hardphones” – traditional telephone sets in appearance but instead of plugging into telephone jack for connection to a PBX port, the IP Hardphone plugs into an ethernet port on the local area network. Usually multifunction phones, some now coming equipped with web browsers. Note that IP hardphones must receive their power either from a transformer near the phone or through the Ethernet port (new standard for power over Ethernet). In either case if the building power goes out, the phone will go out and be out until the power is restored and the set “reboots.” Regular telephones get their power from the telephone system which are usually powered with UPS.

IP “Softphones” – the equivalent of a telephone in an application that runs on a network connected PC. Must be equipped with multimedia card for sound and microphone. Can even be installed on wireless palm devices.

Greater functionality PBX features: Call coverage, busy indicators, hold, transfer, conference, etc. Call accounting Voice Mail/Messaging interface Call Center demands

PSTN Interface Gateways Gatekeepers Protocols

Gateways Gateways provide translation service between network. Typically between Ethernet/IP and to PCM-bus architecture. Gateways contain DSP’s which provide codec functions, jitter buffers, echo cancelation, tone detection and generation, and packet processing.

Gatekeeper The gatekeeper controls access to the gateway, address translation and parsing, and network signaling.

Protocols H.323 – an ITU standard that describes how multimedia communications occur between terminals, network equipment, and assorted services on IP networks. SIP (Session Intiated Protocol) – a competing IETF standard that performs similar functions to H.323 May see merger of these two into one

Network Implications Network design issues Traffic isolation Secured access

Network Design Issues Delay (<180ms for business quality) –Accumulation delay –Codec and packetizing delay –Jitter buffer delay –Network transit delay Jitter (delay variation - < 20ms) Packet loss (>3% will affect signaling) Reliability Interoperability QoS(Quality of Service) Switched 100Mbps to devices

Traffic Isolation Virtual Local Area Network (VLAN) is recommended to help isolate voice endpoints. –Broadcast traffic –Hackers –Denial of service attacks However, there is a maintenance burden with VLAN

Security VPN – Virtual Private Networking can protect the system, but you must be careful to avoid delay created by encryption. Hackers – VoIP components vulnerable to hackers. Extraordinary security efforts are required.

Where does VoIP make sense Remote office locations (converged T-1) Worldwide 5-digit dialing plan for remote locations Telecommuters/Remote workers Road Warriors IP Trunking of PBX’s Softphone on iPAQ’s or other wireless palmtops (campus mobilephone through )

Where does VoIP not make sense Dormitories – where students bring their own phones Critical use telephones Where there already exists a considerable investment in standard technology

What are the major cost elements? Data switch ports are relatively inexpensive ($ /port) – cheaper than PBX ports (But UPS may be required in every wiring closet to provide continuous telephone service during power failures/interruptions) IP Telephones relatively expensive depending on comparison (analog versus digital) Less copper pairs between buildings (big $ - but this can be avoided with PBX design also)

So… The jury is still out on VoIP being dramatically and generally cheaper than conventional PBX technology. There are no doubt applications where VoIP makes economic sense

What about 911? Ability to move phones to LAN ports can produce a problem in location information Locking ports down removes the advantage. Remote IP phone locations in a different 911 are must have local trunks This is something to be careful with! There are life- safety issues which should not be trivialized.

How does this work at USF? AVAYA PBX PSTN Media Processor Control LAN Router PCM Circuit Pack Router PC T Mbps Trunks

Recommendations: For those with existing PBX infrastructure, determine if the PBX can be retrofitted to be VoIP capable. –This retains the advantages and reliability of the existing system and still provides the use of VoIP where it is appropriate. –Provides for seamless administration of voice applications across the enterprise – a cost savings –Insure network is capable of supporing VoIP!

For those with Centrex, consider beginning a shift to VoIP with new facilities. –Perform cost analysis –Perform benefit analysis –Perform network analysis –Install small but expandable VoIP system and trunk between Centrex and VoIP system for seamless operation –Migrate over to VoIP capable PBX in stages

For those with new facilities: –Install a VoIP capable system, on new network infrastructure designed to support VoIP. –Design with long-term vision of how the new facility will work in a corporate VoIP scenario (in other words insure that what is put into the new facility will work seamlessly with what you are planning in the long run for your whole organization)

Some things to think about with Vendors Does the vendor have a product line that offers a full solution suite? Messaging? Call Center? Does the vendor offer open systems support for standards or do they make proprietary modifications to protocols? Does the vendor really understand the nuances of voice telephone operations? It’s not always simple! Can the system be designed to support multiple locations without administration of multiple systems?

And now a word from our Sponsors: USF is a official Business Partner of Avaya Communications and can offer consulting and the full range of Avaya products. If you have an interest in what we can do for your organization, please feel free to call USF Technology Services, Inc. at or visit our website at

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