Using VoIP to Connect Phones Between Offices?

virtualPhoneWire asks: "My office is expanding to include a new facility which is just a few hundred feet just across the parking lot. The building is just far enough away to make running cable a pain in the neck, so to get data over there, we're setting up an 802.11b link, and a couple of simple Linux routers to handle the traffic, no problem. Now, the people in this new building are going to need access to our phone system, a simple Avaya Partner II key system. I would like to think that there is a way that I can patch them into our switch using some kind of VoIP technology. The ideal being that we can issue a couple of IP phones that plug into the Ethernet back-bone, take their queue from my DHCP server, and linkup with a device on the other end that ties them into switch thus giving them access like any other phone. As an after thought, being able to give other people on our network, both inside the building and via our VPN, access to this gateway to make calls would be a real bonus. We're considering an upgrade to a real PBX, but we would like to do this without blowing the pension plan. We would like to having something scaleable, and open source, if possible. Any thoughts?"

Comments

Hardwire it

[ka9dgx]

Let's face it, the only reliable way to get the phone service there is good old fashioned copper (or fiber). While I could support the idea of networking via 802.11b for a non-critical service such as networking, you really want honest to goodness cabling involved when you need to call 911, etc.

--Mike--

Re:Hardwire it

[davidu]

He wants to connect to their voicemail/psuedo-pbx setup.

There's no reason they can't/won't be able to get a landline from the phone company for like a fax or local/emergency line.

Lots of offices have the occasional _seperate_ line for things like faxes, local calling and/or 911.

-davidu

Re:Hardwire it

[Dark Fire]

Good point. If the power goes out and the wireless equipment/VoIP phones are not on a UPS, the phone system to that whole building goes down.

Re:Hardwire it

[mosch]

Nearly all office phones stop working once the UPS on the PBX goes out anyway. If you need to call 911, the phones will probably be working, and if they're not, odds are good that every single person in the office has a cell phone anyway.

Wha? Huh?

[Anonymous Coward]

The building is just far enough away to make running cable a pain in the neck, so to get data over there, we're setting up an 802.11b link, and a couple of simple Linux routers to handle the traffic, no problem.

What's with all this cabling talk? Never heard of a WAN?

Now, the people in this new building are going to need access to our phone system, a simple Avaya Partner II key system.

So how much would it cost for your phone co to hook this up?

I would like to think that there is a way that I can patch them into our switch using some kind of VoIP technology. The ideal being that we can issue a couple of IP phones that plug into the Ethernet back-bone, take their queue from my DHCP server, and linkup with a device on the other end that ties them into switch thus giving them access like any other phone. As an after thought, being able to give other people on our network, both inside the building and via our VPN, access to this gateway to make calls would be a real bonus.

You want to become your own phone company? Besides the initial investment costs, do you have the money to hire someone on to babysit the phone system?

We're considering an upgrade to a real PBX, but we would like to do this without blowing the pension plan.

Are your employees aware of how little money you have? Seriously, if you are expanding at a rate that requires you to lease new office space across multiple buildings, maybe you have enough money to leave this to the pros.

We would like to having something scaleable, and open source, if possible. Any thoughts?

Yeah. Don't skimp on the communications.

VoIP Bandwidth and Leased Line Alternative

[jpkazarian]

Something to keep in mind: For real time speech quality, wireline TDM bandwidth = 0.15 * IP Bandwidth. Meaning that a 100 Mbps Ethernet link can support approximately 10 T1 lines worth of voice calls (120 simultaneous full duplex conversations). This is based on Ethernet realizing a 33% average throughput on shared media plus allowing 100% headroom for equivalent quality after IP packetization and quantization.

If the throughput of wireless Ethernet is the same as wireline, and by throughput we're not talking about the burst speed of the link, then an 802.11b link should be able to support one T1 worth of voice channels, or twelve simultaneous conversations. If RF interference reduces the throughput, your mileage may vary.

Another alternative is to lease a T1 qualified two twisted pair copper line between the two buildings from the phone company. Other posts are mentioning using channel banks at either end of the line. With leasing, the cost and pain of digging et al belongs to the local phone company. It may be worth the monthly rate for 100 feet to avoid that.

Re:call your system vendor

[dreamt]

Well, I'm not sure what the Avaya Key system is, but I know that Avaya has a native add-in card for their G3 line, which handles native (avaya hardware) IP phones, as well as "softphones" (install Avaya software on Win2k machine, it acts like a real phone). The phones act just like a real extension from the switch side. It works fine from long distances (our dev switch is in Boston, we have a remote offices in Dallas and Miami who use IP phones over a T1) so probably would do fine over wireless ethernet. The phones even have a "mini" hub built in. Plug phone into ethernet, then can plug a PC into the phone so you don't even need an extra network port. Only annoying thing is that the phones need power (although they support Power over Ethernet) and have a massive power brick.

Again, I don't know what your phone system is, but this might work if it can support these phones.

Re:Wha? Huh?

[afidel]

Clueless person alert!

What's with all this cabling talk? Never heard of a WAN?

MAN not WAN and 802.11b bridges are a pretty good way to do this in a campus environment where ripping up pavement isn't an option.

So how much would it cost for your phone co to hook this up?

How much would it cost in monthly interoffice calls each month is the more important question

You want to become your own phone company? Besides the initial investment costs, do you have the money to hire someone on to babysit the phone system?

It's called a PBX and since the majority of most offices traffic is internal it saves huge cash over POTS lines.

Are your employees aware of how little money you have? Seriously, if you are expanding at a rate that requires you to lease new office space across multiple buildings, maybe you have enough money to leave this to the pros.

PBX's often have large upfront costs that can be prohibitive for a small business because the chasis are designed for a much larger size then the client needs.