Take the 2-minute tour ×
Server Fault is a question and answer site for professional system and network administrators. It's 100% free, no registration required.

Full disclosure - This is related to a homework assignment question. I am not asking you to do my work for me, I am merely looking for some pointers and considerations to direct me in my further research.

I have an assignment I'm working on where I've been given a scenario where a business wants to look into transitioning to using "Internet Telephone" as opposed to a traditional PSTN/PBX system and I need to write a report on it. I'm after some high level pointers from people, especially anyone that has been involved in a real life transition of this nature, on what some of the most important considerations are.

These can be financial considerations, initial setup considerations, ongoing administrative considerations, quality of service considerations or anything else that is pertinent to performing such a transition.

share|improve this question
    
What is the scale of the deployment you are supposed to be modeling? The considerations for a 10 user office are greatly different from a 100 or 1000 user office. –  Zypher May 10 '10 at 6:34
    
Frustratingly, the question I'm working on provides few assumptions. However, let's assume somewhere around 100 people, though I'd also be interested to hear any other information anyone wishes to provide on how considerations would change for a smaller or larger deployment. –  Bryce Thomas May 10 '10 at 7:51
add comment

5 Answers

up vote 2 down vote accepted

There are a number of variables to take into account when looking at transitioning to a VoIP system. The first thing you have to decide is what type of system you are going to want to implement. When it comes down to it there are basically four types of office telecom systems (all terms mine).

  • Traditional - This is what you would think of the classic PBX. You have POTS lines (normally in the form of T1 or DS3 lines) comming into an office, which are then hooked up to a traditional PBX. Out of the PBX you have hard lines running to each desktop.

  • Hybrid - This is probably the most common form you will find today with VoIP installs. What this is is a normal POTS line (Normally in the form of a T or DS3 line) running into a PBX, then the traffic is converted to VoIP at the PBX. Your desk phones then connect via regular Ethernet to the PBX using VoIP.

  • VoIP Trunk - This is where your provider delivers a VoIP trunk over your internet connection or dedicated circuit. Which then connects to your PBX. Your desk phones then connect via regular Ethernet to the PBX using VoIP

  • End-to-end VoIP - This type of install is generally only seen in small offices. This is where your desk phones connect directly to a provider over the internet using VoIP.

Some things to take into consideration when deciding which way to go:

  1. How many concurrent calls will need to be made out of the system? This is going to be a peak concurrent call number so that you do not drop any calls during peak volume times
  2. What is our One time budget, what is our ongoing monthly budget
    1. One time budget Items would include: loop charges, install charges, equipment charges. (if you would like some ballpark numbers for the US on these things let me know)
    2. Monthly budget would probably just include your monthly phone bill
  3. If you are going the VoIP trunk or end-to-end design you'll want to know:
    1. Where is the provider's POP (is it down the street or in Chicago?)
    2. Do they offer dedicated bandwidth with QoS to their POP?
    3. What kind of SLA and Quality guarantees do they provide, what are the penalties for not reaching these guarantees?
    4. Is symetrical broadband available in my area?
  4. Does the provider supply the equipment on a rental basis or will you need to purchase the needed equipment outright?
  5. Does your local networking equipment provide for QoS?
    1. If you don't have dedicated links to the provider's POP then you will be at the mercy of the internet once you get out of your network.
  6. What is an acceptable call quality level? Can we accept some jitter or static on the line?

Once you have reviewed all of these things, the decision you are really going to come to is where does price and performance meet that is acceptable to the business?

Personally I still believe that the Hybrid approach offers the best of both worlds, the portability and ease of management of VoIP inside the office, with the reliability and price of traditional POTS out of the office.

I apologize if some of this is a little vague, but as you said this is homework so I'm trying to point in the right direction without giving you the answers :) If you need clarification on any of my points please let me know.

share|improve this answer
add comment

I'd suggest two routes for further investigation; the open source Asterix (Clicky) platform and Cisco's Small Business Voice System (Clicky) - they're not bad starting positions ok. In terms of basic models both of these work in a fairly similar way to a traditional PBX (central switch/es with star topology, management system, gateway to outside world, voice mail system).

share|improve this answer
add comment

I'd say the first thing you need to address is what services is the phone system expected to provide? I.e. a spec of some kind - if you don't know what the organisation and users need, then you won't be able to provide it.

share|improve this answer
add comment

Although I can't provide you with a link or a source, I heard from a colleague that Microsoft gave a presentation (might be Techdays, but could as well be something entirely different) where their Office Communications suite would provide this while the cost was a lot lower than any of their competitors'. I know it's vague, but if you think this is interesting for your assignment I guess you can try googling around a bit for recent presentations they gave on the subject, it's most likely something they like to tell people as often as they can ;)

share|improve this answer
    
The OCS VoIP connecvitity is - AFAIK - just a hook into your current VoIP infrastructure. Basically a voip softphone, or hooks into your PBX + deskphone so you can initiate calls from the office suite. –  Zypher May 10 '10 at 14:13
    
That's right, it can use a softphone, but there are "hardware softphones" (not sure what to call them), so basically a softphone with the formfactor of a regular phone. Should work fine I think! –  HannesFostie May 10 '10 at 14:42
add comment

"I have an assignment I'm working on where I've been given a scenario where a business wants to look into transitioning to using "Internet Telephone" as opposed to a traditional PSTN/PBX system and I need to write a report on it. I'm after some high level pointers from people, especially anyone that has been involved in a real life transition of this nature, on what some of the most important considerations are."

If this is a replacement of an existing PSTN / PBX / Key system then the cost will be high.

If this is a new office scenario then you can make a direct comaparison:

PBX / Key vs. VoIP Server Less wiring with VoIP Initial setup would be a wash, assuming that the person doing it had experience Quality should be a wash Assuming the maintainer of the system had no prior experience, training would be a wash Handset cost Connectivity to the PSTN

In both cases a an analysis of the amount of data traffic / connection method and voice traffic analysis needs to be done. For example, if the site has 100Mbps connections to the end-user, there are large numbers of end-users, and the end-users generate high volumes of data, you may need to upgrade the connections.

One other thing to consider. Some amount of phones should be POTS lines for disasters.

share|improve this answer
add comment

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.