VoIP Frequent Questions and Answers

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					                       VoIP Frequent Questions and Answers
                                                      Florida Feb, 2005

                                                      An T. Le, CTO
                                                      Planet Reach, Inc.

When Voice over Internet Protocol (VoIP)          -   Who can help me with a VoIP
was offered to the public, Many thought that          solution?
it was time to say goodbye to the PBX, and
bid a not so fond farewell to long distance    1- What is VoiP
toll charges. That dream is almost a reality
but we still await lower system costs and      It’s well known that VoIP is the technique
higher quality of service (QoS). The true      used in transferring telephone (voice) signal
key to this dream lay in the heart of IP       over the Internet by using Internet Protocol.
technology itself. VoIP service depends on     The technique actually transmits a digitized
IP service and not just its quality but its    version of your voice through IP. The
quantity as well. These issues leave some      digitized voice information is sent out over
with unanswered questions about whether        the Internet just like other data. From the
its time for them to moth-ball the old PBX     Internet’s standpoint there is no difference
and jump into VoIP. This article will          between other data and digitized voice data
attempt to address some of those questions.    unless we somehow identify the data and
                                               can recognize the data as a real time signal.
Some of the most common VoIP questions         Most Internet instant messengers (like
are:                                           Yahoo, Microsoft) allow voice chat. That’s
   - What is VoIP?                             one of the types of VoIP. If you have proper
   - What is the difference between my         interfacing devices you can use can even use
      old phone and an IP phone?               an analog phone for chat with these services.
   - What are the advantages and               While these services are technically VoIP
      disadvantages of VoIP?                   they aren’t quite what the world is looking
   - Why people complain about the QoS         for as a telecom solution, the real world of
      of VoIP?                                 VoIP is of course, more complex. Fig. 1
   - Why does VoIP take more bandwidth         illustrates some common VoIP scenarios.
      than I thought?
   - Who is the best service provider?         2- What is the difference between my old
   - What is the best VoIP solution for           phone and an IP phone?
   - Is VoIP really free?                      The traditional phone we use is an analog
The more technical questions:                  phone. It’s usually based on the Bellcore
   - What is a VoIP PBX and how does it        standard. Only two wires are needed for
      connect to a traditional phone line or   analog phones, the wire ends in an RJ-11
      local telephone service provider?        connector and set up is as simple as
   - Can I build a VoIP sever by myself?       plugging that connector into the wall. An
      What do I need?                          IP phone is very different, in fact it is a
   - What is a good solution for small         combination of two things, a digital phone
      business or home business?               and a system that converts the digital

information into chunks of information                                                                                                                            connector and unlike the analog phone, set
suitable for shipping using the IP. An IP                                                                                                                         up requires a lot more than just plugging that
phone requires 8 wires and ends in an RJ-45                                                                                                                       connector         into        the        wall.

              Gateway- Router                                                                                                                                                                                                                                                      Gateway- Router

                                LAN                                                                                                                                                                                                                                     LAN

                                                         @VODA                                                                                                                                                                                            @VODA
                                                             VoIP Server/
                  1   2   3        1 2     3                    PBX                                                                                                                                 VoIP Server/
                  4   5   6        4 5     6
                  7   8   9        7 8     9
                  *   8   #        *   8   #

       PC         IP Phone                                                                                                                                                                                                                                                              IP Phone         PC

                                                                    PSTN gateway                                                                                                    PSTN gateway


                              Analog Phone                                                                                                                                                                                                                                    Analog Phone
            Fax                                                                       Bay Networks                                                                                   Bay Networks
                                                                                                                                                 SD                                                                                             SD
                                                                                                            BayStack 650 Wireless Access Point

                                                                                                                                                                                                           BayStack 650 Wireless Access Point
                                                                       Bay Networks

                                                                                                                                                                     Bay Networks
                                                                                                                                                                                                                                                         Local Telephone Service

                                                                                                     C.O.                                                                                           C.O.

                                               Analog Phone                                                                                                                                                                                          Analog Phone
                                                              Local Telephone Service

                                                                                                                                                          Fig 1

3- What are the advantages                                                                                  and                                                   4- Why people complain about VoIP
   disadvantages of VoIP?                                                                                                                                            QoS?

   Advantages:                                                                                                                                                                      -                 Echo is one of the big issues. There
   - You can make a call anywhere the                                                                                                                                                                 is a significant amount of echo when
      Internet can reach                                                                                                                                                                              a call is bridged from VoIP to PSTN
   - Per minute cost savings and                                                                                                                                                                      (Public       Switched     Telephone
      equipment cost savings on the PBX                                                                                                                                                               Network)
   - It has more features that it has                                                                                                                                               -                 Calls can drop at any time
      adopted from Internet technologies                                                                                                                                            -                 Voice is often choppy
   - Security, all the same risks as can be                                                                                                                       5- Why VoIP uses more bandwidth than
      found with any IP technology                                                                                                                                   I thought?
   - High cost for IP phone
   - SIP phones cannot share extensions,                                                                                                                          VoIP coding and packetization result in
      one SIP phone per extension                                                                                                                                 delays greater than users typically
   - High IP bandwidth consumption                                                                                                                                experience in terrestrial switched circuit
   - Delay time, Echo                                                                                                                                             networks. Standard speech codecs are
   - May have no emergency service                                                                                                                                available for output coding rates in the
      such as 911…                                                                                                                                                approximate range of 64 to 5 kb/s. Packet
   - You require some form of IP service                                                                                                                          design involves a tradeoff between payload
      to make a phone call                                                                                                                                        efficiency (payload/total packet size) and
                                                                                                                                                                  packetization delay (the time required to fill
                                                                                                                                                                  the packet). For IPv4 (the current

technology), the RTP/UDP/IP header is 40          * Those who elect to have their telephony
bytes. At 64 kb/s, it only takes 5 ms to         services provided to them by a VoIP service
accumulate 40 bytes, but at 8 kb/s it takes 40   provider can typically expect that to have
ms to accumulate 40 bytes. A packetization       what little equipment they need provided to
delay of 40 ms is significant. Many VoIP         them as part of some time defined contract.
systems use 20-ms packets despite the low         * For one who wants to host their own VoIP
payload efficiency when using low-bit-rate       service, there are two roads that one could
codecs. For continuous speech, the call          take:
transmission capacity requirement B (the             - Two IP phones with static IP
amount of required bandwidth in kb/s) is                 addresses can act as point to point
related to the header size H (in bits), the              peers and communicate with one
codec output rate R (in kb/s) and the payload            another without anything else to
sample size S (in milliseconds) as:                      support them… of course they can
                                                         only talk to each other.
                 B= R+ H/S                           - Create a VoIP server to host yourself
                                                         and your partners. How? Take a
The bandwidth may be as big as five times                look below for more on that
of codec’s output rate. IPv6 offers some                 question. You will need some basic
significant improvements over the current                knowledge to get started but after
technology (IPv4) by reducing header size;               you have done it once you’ll
however, we will have to wait a little longer            practically be a professional by the
before we realize the promise of IPv6.                   time you finish.

6- Who is the best service provider?             8- Is VoIP really free?

After learning a few things about VoIP you       The short answer is: no and is anything free?
know a little bit more about what to look for    If you host your own VoIP service it will
in a good VoIP service provider. Customer        cost you at least the equipment you use to
service is very important for VoIP service       build your server, plus the time to put it
because it is still new and there are some       together (maybe some time to learn how to
unpredictable problems that will arise. In       do all of that in the first place). On top of
general you can choose any VoIP service          that you still need some bandwidth from
provider that you are comfortable with what      your ISP.
matters in the long run is how well they
support you.                                     9- What is a VoIP Server and how is it
                                                    connected to a traditional phone line
7- What is the best VoIP solution for               or local telephone service provider?
                                                 A VoIP Server is used to connect or switch
This is a question worth thinking about. We      your call. It works like a Telephone PBX
can actually break this down into two            (Private Brand eXchanger), it includes: a
separate situations:                             transceiver for voice, dial tone, DTMF (Dual
   - VoIP services from a service                tone multi-frequency), call ID etc... To
        provider                                 connect to PSTN, a VoIP device needs an
   - Self service                                adapter or a VoIP/PSTN gateway. Usually,
                                                 the trunk line from the VoIP device to the

C.O. (Central Office) could is a telephone     Asterisk was originally written by Mark
line (FXO- Foreign eXchange Office) or any     Spencer of Digium, Inc. Since the project
some Voice over Frame trunks like as T1 or     began more code has been contributed by
E1.                                            the open source community from people
                                               around the world. Continual testing and
A VoIP Server may also have additional         good Samaritan bug fixes have kept the
interfaces to analog phones via FXS            project going and growing by leaps and
(Foreign eXchange Station) interface(s).       bounds.

10- Can I build a VoIP sever by myself?        If you have access to a PC running some
    What do need?                              flavor of the Linux operating system you
                                               can try downloading the Asterisk source
Yes you can build a VoIP server by             code from www.asterisk.org and give it a
yourself. You will need some knowledge         go. Asterisk does not require anything more
about the Internet and PBX technology in       than a PC to function in a pure VoIP
general to set up your own VoIP server.        environment; however, for interconnection
                                               with digital or analog telephony equipment
There are many software PBX systems on         you will require some additional equipment.
the market running on everything from
UNIX to Windows. Most of these software        11- What is a good VoIP solution for
packages are commercial packages licensed          small business or home business?
based on the number of users and/or the
feature set that you require.        As an     Asterisk is known as a good solution for
alternative to these commercial software       SOHO (Small Office/ Home Office). It’s
systems you can consider Asterisk, which       also very good for developers or amateurs
has become something of a phenomenon in        who have some knowledge about how phone
the VoIP community. Asterisk is a complete     systems work and know how to work with
software VoIP PBX designed to run on           Linux. Although making Asterisk easy to
Linux and provide all the features that one    use requires some more work it is still very
would expect from a traditional PBX plus       affordable and a good SOHO solution for
some you may have never even thought           anywhere from one to one hundred users.
about. Asterisk supports VoIP in three         You can have asterisk professionals help
protocols and can interoperate with almost     you set up configuration files and features
any standards-based telephony equipment        but the price will always lower what you can
using relatively inexpensive hardware.         expect to pay for a traditional PBX Perhaps
                                               the nicest thing of all about Asterisk is that
Asterisk provides Voicemail services           you don’t have to pay licensing fees for
complete with a directory, Interactive Voice   every feature you want and every user that
Response menus, conferencing and call          you add like you do with most PBX
queuing (ACD) and the more mundane             systems.
services such as: caller ID and ADSI.
Asterisk has complete support for SIP and      12- What needs for Asterisk user?
H.323 (the most common VoIP protocols) as
both a client and a gateway.                   The toughest thing about using Asterisk is
                                               that there is no graphical user interface
                                               included with the software. Even though

there is an abundance of willing people in
the open source community available to help     References:
answer your questions plus expert
consultants who can provide professional           1- Voice & Data Internetworking – Gilbert
assistance, its no replacement for a feature           Held; McGraw-Hill – 2000
                                                   2- Comparative         analysis     of    traditional
rich GUI to assist in things like: setting up          telephone and voice-over-Internet protocol
extensions, voice mail, dial plan, billing,            (VoIP) systems - Hui Min Chong;
management. Its not fun to have to edit                Matthews, H.S.; Electronics and the
configuration files line by line to get the            Environment, 2004. Conference Record.
machine to do what you want… consider the              2004 IEEE International Symposium on
                                                       , 10-13 May 2004; Pages:106 – 111
number of lines and then what happens if           3- Implementing VoIP: a voice transmission
you make a mistake somewhere in the                    performance progress report- James, J.H.;
middle of them?                                        Bing Chen; Garrison, L.; Communications
                                                       Magazine, IEEE , Volume: 42 , Issue: 7
Planet Reach, Inc. a Florida telecom                   , July 2004; Pages:36 – 41
                                                   4- Fractal analysis and modeling of VoIP
manufacturer is one of a few companies tat             traffic- Trang Dinh Dang; Sonkoly, B.;
can provide customers with some additional             Molnar, S.; Telecommunications Network
added value packages. This can help                    Strategy      and      Planning    Symposium.
alleviate a lot of the headaches for Asterisk          NETWORKS 2004, 11th International , 13-
users and developers.          Planet Reach’s          16 June 2004; Pages:123 – 130
                                                   5- Integrated system interoperability testing
packages include:                                      with applications to VoIP- Ruibing Hao;
     - Configuration generator with a                  Lee, D.; Sinha, R.K.; Griffeth, N.;
         large of choice for Analog phone, IP          Networking, IEEE/ACM Transactions on
         phone, include PRI (Primary Rate              , Volume: 12 , Issue: 5 , Oct. 2004;
         Interface) and IAD (Integrated                Pages:823 – 836
                                                   6- Voice over Internet protocol (VoIP)- Goode,
         Access      Devices)     FXO/FXS…             B.;Proceedings of the IEEE , Volume: 90
         interfaces, with other features such          , Issue: 9 , Sept. 2002; Pages:1495 – 1517
         as DID, transfer, forwarding…             7- The performance analysis of SIP-T signaling
     - Subscriber and Billing Manager                  system in carrier class VoIP network- Jung-
     - Learning machine for voice echo                 Shyr Wu; Peir-Yuan Wang; Advanced
                                                       Information Networking and Applications,
         canceller                                     2003. AINA 2003. 17th International
     - Media plug-in                                   Conference on , 27-29 March 2003;
     - Graphic User Interfaces (GUI)                   Pages:39 – 44
     - Remote Management System (RMS)              8- Survey on QoS management of VoIP-
     - …                                               Xiuzhong Chen; Chunfeng Wang; Dong
                                                       Xuan; Zhongcheng Li; Yinghua Min; Wei
You can contact Planet Reach Inc. at 1-866-            Zhao; Computer Networks and Mobile
50-REACH or look at the company’s                      Computing, 2003. ICCNMC 2003. 2003
website at www.planetreach.com for more                International Conference on , 20-23 Oct.
information.                                           2003; Pages:69 – 77
These Planet Packages will help you have a         9- Study on appropriate voice data length of IP
                                                       packets for VoIP network adjustment-
much more enjoyable experience and get a               Oouch, H.; Takenaga, T.; Sugawara, H.;
lot more out of Asterisk. If you think you’re          Masugi, M.; Global Telecommunications
about ready to jump into VoIP make your                Conference, 2002. GLOBECOM '02. IEEE
first experience a good one and a valuable             , Volume: 2 , 17-21 Nov. 2002; Pages:1618
one so that you know that you made the                 - 1622 vol.2
                                                   10- Service drivers for selecting VoIP protocols-
right telecom decision for your company.               Chatras,           B.;        Garcin,         S.;

      Telecommunications Network Strategy and
      Planning Symposium. NETWORKS 2004,
      11th International , 13-16 June 2004;
      Pages:131 – 136
11-   QoS support for VoIP traffic to prepare
      emergency- Noro, M.; Kikuchi, T.; Baba,
      K.; Sunahara, H.; Shimojo, S.; Applications
      and the Internet Workshops, 2004. SAINT
      2004 Workshops. 2004 International
      Symposium on , 26-30 Jan. 2004; Pages:229
      – 235
12-   Evaluating semantic warnings in VoIP
      programmable services with open source
      environment- Leelaprute, P.; Nakamuraa,
      M.; Matsumoto, K.-I.; Kikuno, T.; Software
      Engineering Conference, 2003. Tenth Asia-
      Pacific , 10-12 Dec. 2003; Pages:552 – 561
13-   Analyzing end-to-end delivery delay in pure
      VoIP networks- Scheets, G.; Singh, R.;
      Parperis, M.; Circuits and Systems, 2002.
      MWSCAS-2002. The 2002 45th Midwest
      Symposium on , Volume: 2 , 4-7 Aug. 2002;
      Pages:II-517 - II-520 vol.2
14-   Design and implementation of a SIP-based
      VoIP architecture- Zeadally, S.; Siddiqui,
      F.; Advanced Information Networking and
      Applications, 2004. AINA 2004. 18th
      International Conference on , Vol:2 , 29-31
      March 2004; Pages:187 - 190 Vol.2


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