Input needed: Deployement questions for 40 to 100 users


My enterprise is growing pretty fast and we will be moving our office in two months. We currently have around 35 independents phone line for around 40 users. I thought that it would be a good time to review our phone system before the new offices are laid out.

I would appreciate if some of you could give me their opinion on my plan.

The system I would like to built has to be able to accommodate 40 users right now with a possibility to expand to 100 later.

My plan is to buy the following hardware:

Dell Poweredge 2950 (2x Dual core Xeon 1.6Ghz, 2 GB, 160GB RAID1)
Digium TE205P(Dual T1 card)

Subscribe to a T1 PRI, buy DIDs for all my users.

Use a mix of softphones and SIP phones.

Here are my questions:

Is my hardware powerful enough to serve 100 users? Is it an overkill?
I understand that a T1 can provide 23 lines + CID and ANI am I correct?
Will it be enough channels for 40 users?

Most important, do you think this project is to big for a first time user?
I have good linux skills and some experience with telephony (nortel courses for voip…).



Why subscribing to an isdn provider. If you really want to take advantage of all the new features of VOIP compared to traditional telephony you should subscribe to IP telephony provider.

  • You save the costs of the card

  • You safe the costs of the isdn subscription

  • You can add an external line in your dialplan and return to the next line. (try office phone for 10 seconds, try mobile phone for 10 seconds, route the incoming line to voicemail box. This will not work properly with isdn line)

  • It will keep the installation more simple. Just install asterisk, add the account info of the provider and configure the numbers.

  • It removes a single point of failure out of your system, the isdn card.

  • It will (if you choose a proper provider) give you much more flexibility if it comes to number of available lines.

  • It will lower the cpu load as long as you use internally the same codec as you provider uses. Otherwise the Asterisk server has to convert from one codec to the other and with the number of lines you are talking about that will really load your cpu.

  • It is likely that a IPT-provider is cheaper then an oldfashion telco offering isdn lines, especially when you are making lots of international calls.

  • You need proper and highquality bandwidth, this will cost.

  • You might need g.729 licenses to keep the bandwidth needed as low as possible while keeping a proper quality, this also will cost.

If you want to use all the processor power in this server some special things has to be done I heard. Maybe I’m wrong but it is sad if one processor of the 4 available is doing all the work.

thank you for you answer.

I am aware that I can use a internet provider for my connexion but if I save on the price of the ISDN connexion, the cost will only move to my Internet connexion which I will need to beef up.

About the single point of failure, I think I add more points of failure by going fully IP: ISP, VoIP provider, router, etc…

I am still evaluating a couple of avenues. I will let you know how I will do it.

Thank you,


The hardware should be enough to handle 100 users. We do more with a lot less. It might be overkill now, but when management figures out all that asterisk brings to the table, you’ll be glad you have enough “spare” power to implement it. You don’t say what your company does, so assuming “normal” office setup, a T1 should be enough. We use a 2:1 ratio of users to lines for office workers which you can push to 3:1 if call volume is low, and 1:1 for outbound sales.

I believe that a Dell 2950 comes with an option of PCI Express or PCI-X slots. The TE205P will not work with either. You need a TE210P for PCI-X or will have to go with Sangoma for PCI Express (don’t think that Digium has a PCI Express version yet). I see that Digium finally made the single port card (TE110) dual slot dual voltage (will work in both PCI and PCI-X slots but not PCI Express)so you might want to hold off until they do the same for the 2 port cards. It’s been a while since I bought a card, and new cards come out all the time so make sure I didn’t get the models reversed. Above all, make sure you get the right card for the slots in your server.

There are some very good softphones available so that’s just trial and error. For hard phones, check the boards for what others are using and why.

I’m not familiar with carriers in your area, but ANI and CID should not be a problem. Is the project too big for a first time administrator? Probably not, but go ahead and spend some quality time with your significant other(s) before you start. You will not see them for a while.


akauffmann: haha thanks for the advice concerning my GF, but that won’t be an issue, we just broke. :wink:

One company gave me a quote and said that a 1950 with a single processor would be ok for up to 100 users. They also suggested the Sangoma card.

I’m glad you think I will be able to do it by myself. I bought “the future of telephony”, “switching to voip” and “building phone systems with asterisk” I’ll read them this week and take my decision during the weekend. :smile: