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VoIP issues from Physics for the ITPG member. A gracious good morning to you...Have I reached the party to whom I am speaking?" . Physics Department March 2010. Adumbration. Terminology How your phones work now How VoIP is different “Five Nines” reliability What it takes to “VoIP”

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voip issues from physics for the itpg member

VoIP issues from Physics for theITPG member

A gracious good morning to you...Have I reached the party to whom I am speaking?"

Physics Department

March 2010

  • Terminology
  • How your phones work now
  • How VoIP is different
  • “Five Nines” reliability
  • What it takes to “VoIP”
  • What it saves
  • What it costs
  • Problems/Security/Phone company issues
glossary of terms for voip telephone systems
Glossary of Terms for VoIP Telephone Systems
  • CID - Caller Identification
    • Information transmitted between the first and second ring by phone systems which includes the caller's phone number and possibly the billing name for presentation on the station of the call receiver. On the PBX side, the information passed out for display on the other end is the CLI, or Calling Line Identity. The PBX owner decides what is sent, be it a specific DID for each station or user, or a common set of information. 
  • Dialing plan
    • Establishes the expected number and pattern of digits for a telephone number. This includes country codes, access codes, area codes and all combinations of digits dialed. For instance, the North America uses a 10-digit dial plan that includes a 3-digit area code and a 7-digit telephone number. Campus uses a 4-digit dialing plan, with internal extensions consisting of 4 digits. PBXs can support variable-length dial plans that use 3 to 11 digits. Dial plans must comply with the telephone networks to which they connect. 
  • DID - Direct Inward Dialing
    • Having a unique phone number identifier. Analog (POTS) lines are all DID, and can be reached directly by dialing the phone number assigned. A phone user or telephone station may not be DID, but may be rung through the use of a IVR from a common phone number. Another option would be stations for internal use only, not reachable from the PSTN - such as an intercom or paging system. 
  • Instance
    • Unlike POTS phones, a VoIP phone can have multiple calls at the same time being serviced by a station. Each may have the same DID and end user communicating, but not be the same call, or "instance". For example, while talking on the phone your line is not "busy", and can receive another call, at the same external number, which you could choose to answer or allow to go to voicemail. 
  • IVR - Interactive Voice Response
    • Or IVM for Interactive Voice Menu. A voice menu system that allows users to select options from their telephone keypad to direct their call to the correct user or station.
glossary of terms for voip telephone systems continued
Glossary of Terms for VoIP Telephone Systems (continued)
  • PBX - Private Branch Exchange
    • A phone switch, or "hub" of sorts owned by an entity, not part of the PSTN. The center of an entity's phone system. More than a key-system, it's an automated "switchboard operator".
  • PRI - Primary Rate Interface
    • Sometimes interchanged with the phrase "T1". A digital connection to connect to the PSTN consisting of 24 "channels", of which 23 are usable, and one is reserved for control signals. Each channel can carry a single telephone conversation between endpoints. At UCSB, Communication Services carries the connection over a single pair of wires which a department "rents" from them. They allow a minimum of 12 channels to be used, and charge the normal campus rate for a phone line for each channel activated.
  • PSTN - Public Switched Telephone Network
    • Sometimes referred to as POTS -- Plain Old Telephone System, although that term is also used to refer to the analog phone lines and instruments. Basically, the world's existing phone system, with telephone numbers we are all used to using. The public telephone (telco) companies. 
  • SIP - Session Initiation Protocol
    • A "language" standard "spoken" by PBX equipment and VoIP telephones to allow them to communicate over the Internet for the purpose of voice and video transmission. Basically, a non-proprietary standard which allows equipment and software from many vendors to exist in one system, and interoperate.
  • Softphone
    • A software program for making and receiving telephone or video calls over a network connection using a general purpose computer rather than a dedicated hardware-based telephone. Typically used with a headset that includes a microphone. 
glossary of terms for voip telephone systems continued again
Glossary of Terms for VoIP Telephone Systems (continued again)
  • Station
    • A physical unit used to make or receive telephone calls. This may be a traditional handset (phone) or a softphone. Do not confuse a station with a user, instance or DID, all of which may be synonymous in a older, analog telephone world.
  • Trunking
    • Combining of phone lines (or channels) over a single connection line or path, as in a PRI line. 
  • UC - Unified Communications (not Univ. of Calif.)
    • A trend in business to simplify and integrate all forms of communications. UC refers to real-time delivery of communications based on the preferred method and location of the recipient, not to be confused with Unified Messaging (UM) which culls messages from several sources (such as email, voice mail and faxes), but holds those messages for retrieval at a later time. The voicemail box and e-mail box may be unified when using VoIP, to provide UM, but allowing a user to choose to receive it instantly on her cell, office phone or notebook computer would be UC. 
  • User
    • A person that employs the services of the telecommunications system. Not to be confused with a station, instance or DID.
  • VoIP - Voice over Internet Protocol
    • A general term for a family of transmission technologies for delivery of voice communications over IP networks such as the Internet. A combination of elements make up a VoIP system, which may or may not connect to the PSTN.
telephone as a computer computer as a telephone what does that get you
Telephone as a computer.Computer as a telephone.What does that get you?
  • Intelligent call routing
    • Follow me, home, office, cell, caller-ID information
  • Voice mail
    • Unified Messaging, E-mail
  • Soft phones
    • Flexibility
  • Voice menus
    • Call routing, customer service
  • Faxing
  • The Internet as a call distribution system
    • International calls, “free” long distance
  • Efficient bandwidth use and cost accounting
five 9 s and reliability
Five 9’s and Reliability

99.999% uptime

The “Holy Grail” of all industries sinceAT&T created a

nationwide phone systemas a monopoly.

Users have grown toexpect this level of service.

some elements that make up uptime
Some elements that make up uptime
  • Power outages
    • Planning, generators and batteries
  • Network outages
    • Redundancy, multiple protected paths
  • Equipment failure
    • Redundancy, hot-spares
  • Staffing levels
    • 24 hrs a day, 7 days a week payroll
components of a voip phone system
Components of a VoIP phone system
  • Digital PBX
  • PSTN interface
  • Robust network
  • PoE switches
  • UPSes
  • Digital phones
  • Expertise

Redundancy in everyone of these elementsis required to hit 99.9% uptime

hardware components of a voip phone system
Hardware components of a VoIP phone system
  • Digital PBX
  • PSTN interface
  • Robust network
  • PoE switches
  • UPSes
  • Digital phones

Typical Prices

Network server with RAID-5 and voicemail storage $2000-$5000

Ethernet – PRI interface $800-$1500

PRI line transceivers $600

PoE switches ~$40.00 per port

UPSes $500 per switch location

Digital phones $120 - $250 per phone

hardware components of the physics voip phone system
Hardware components of the Physics VoIP phone system
  • Digital PBX
    • 2 x Dell PowerEdge servers, 2850 as active, 2950 as backup - both dual-homed,

one interface on VoIP VLAN and one on public net

  • PSTN interface
    • 2 x Redfone FoneBRIDGE2 dual T1/PRI "gateways“,

1 active PRI from Comm Services, using 12 channels,

1 backup PRI from Comm Services, 12 channels, currently used for testing purposes,

will be backup in future

    • Analog standby circuits – Qty 2, Digium TDM2403E cards w/2 4-port FXO modules
  • Robust network
    • Gigabit backbone, fiber-based, all switches redundantly connected to next-floor neighbors via copper.
  • PoE switches
    • HP 2610-24-PWR, 2610-48-PWR, 2650-PWR, 2626-PWR– minimum of one per wiring closet, 18 wiring closets
  • UPSes
    • APC 1500VA, 750VA with network interfaces where standby power exists.
    • APC 750VA with auxiliary batteries to assure 2hr run-time where no standby power exists.
    • All PBX and PSTN hardware on networked UPSes with standby power.
  • Digital phones
    • approximately 140 Aastra 9133i (9143i) telephone handsets

3 call appearances, speakerphone, 3-line LCD display

software components of the physics voip phone system
Software components of the Physics VoIP phone system

Digium Asterisk

PBX/call management/voicemail/SIP server

FreePBX 2.7

used for simplified "GUI" management of devices, extensions, call routing etc.


used to sync configs, voicemail directories for Asterisk, Apache etc. between active and backup server

Linux-HA (heartbeat)

used for failover - detects active server down and moves virtual IP for SIP registrations to backup server, tells Redfone to send packets to backup server

Digium Fax for Asterisk - provides incoming FAX to individual DIDs via email and beta of outgoing faxes via email attachments (PDF, Word, Excel) using Messinet Asterisk Fax Gateway (open source project)

Digium Skype for Asterisk - provides mapping of unique individual Skype usernames for your organization to incoming DIDs, IVMS etc.

campus charges on a voip phone system
Campus charges on aVoIP phone system

Campus Charges for Analog

Old analog phone lines $24-$27/mo

Campus voicemail $7.50/mo

Campus Charges for PRI

PRI line installation ~$800

PRI transceivers ~$600

PRI line $24/mo per channel – 12 channel minimum

DID numbers $1.68/mo

reasons to change
Reasons to change
  • Possible cost reductions
  • Control/Flexibility
    • Adding/Deleting extensions
    • Voice menus and call routing
    • Dialing plan based on who/what/where
  • New features
    • Your phone is a computer, or your computer is a phone – how cool!
      • Answering anywhere. Location independence.
      • Address books/directories
      • Everyone gets CID
      • Voice, video, e-mail is all the same
      • Encryption, anyone?
    • Your PBX is a computer, too. How cool!
      • Voicemail built-in
      • Voice/Fax/E-mail all in one location
      • Making “smart” call routing decisions
reasons to not change
Reasons to not change
  • Possible cost increases
    • Equipment, staffing, minimum channels
  • Redundancy and Reliability
  • Becoming a phone company
the twisted tale of campus 911
The twisted tale of campus 911
  • Keeping the database up to date
    • Check with extension 2300(ALICIA) for what they know
  • Sending caller-ID information
    • Public Safety database, “BORIS”
    • “I’m roaming”, “I’m across campus”,“I’m in Europe”, “I’m at home…”
security concerns
Security concerns
  • Your phone system is a computer!
    • Now you are a REAL target for hackers!
security concerns1
Security concerns
  • Firewall
    • Isolation limits usefulness
    • Use VLANs
    • Limit types of connectionsfrom the Internet
    • Limit to only known remotehosts

Isolated VLAN


Known external phone

legal issues
Legal Issues
  • You are a phone company.
    • Laws about wiretapping, phone recordsgo way back.
    • U.C. Electronic Communications Policy
  • E-911 liability
  • Sound quality should be as good or better
  • Echo cancellation
    • Interesting artifact of running analog phones over a single pair of wires, and high local gain
  • Heavy network traffic? Delays?
    • Only a problem with Internet based instruments


You can save money…

If you are big enough.