VOIP

[fs483]

Hello,

I have a client who is asking about VOIP and would like a system setup for his business. I would to know what kind of hardware is required (other than IP phones). Does the phones simply connect to a switch, which is connected to a Router, then to a CSU/DSU, then to the ISP ?

Thanks
anthony

 

[jimbopalmer]

One key to VoIP is prioritization, the traffic needs to be prioritized at switches and routers. We used 802.1p on our LAN. made high Priority VLANs for the IP phones (our phones were to dumb to do 802.1p on their own) and did IP filters on the routers. A more elborate Network would need DifServ for the routers.

This made sure the VoIP traffic alway 'won; over data traffic.

A related but seperate issue is Power Over Ethernet, you need homerun wiring with all 4 pairs.

I tried to remain child-like, all I acheived was childish.

 

[jpm121]

anthony,

You've greatly oversimplified the process, unless you're interested in a "hosted" or virtual PBX-type service.

The missing part is: how do you get dial tone? You need some way of routing calls out onto the PSTN so they could actually talk to other people, right?

 

[fs483]

jpm121,

It's been 2 years since I looked at my notes in my networking classes regarding VOIP. Indeed I forgot about the dial tone part. I'm not sure if my client is aware of all the TCO with implementing such a system. I'm not too sure if they really need it or it's just something management is saying "it would be cool to have this, whatever it is..." I guess I'm going to call up a few local companies and have them evaluate the cost. The problem is that my client and I are seperated by 2:30 drive at 100km/h ! I have a feeling they will quickly drop the idea once they realize TCO eventhough they do quite a lot of long distance calls and a gold mining business. Other than saving on long distance charges, what are the other advantages ?

anthony

 

[jimbopalmer]

JPM I am at a gold mine as well. we had gig fiber between 3 PBXs we had no t1s between, so VoIP trunking alowed better forwarding, voicemail, and the ability to bid larger 'chunks' of LD out.
we had data network some places we had no copper pairs, so IP Phones were used as needed (not wholesale)

I tried to remain child-like, all I acheived was childish.

 

[fs483]

Well my client's head quarter is in Canada, Ontario. I'm located in Canada, Montreal. The mines are in Nigeria, New Guinea, China... I think they are trying to save some money when they talk to their remote offices... So there won't be any "direct" link between the mines and their HQ. I'm not totally convinced for the need of VOIP. We will see, if they are willing to dish a lot of cash into this idea, I guess that will be satisfied.

anthony

 

[jpm121]

Ah, now we're getting somewhere... anthony, you left out the important bit about having remote sites all over the world!! That does, in fact, make a lot more sense.

jimbo sounds like he's already doing what you have in mind. To amplify a bit:

Two ways to approach this on first pass, from what I can see. If each location has a PBX or some similar CPE that can handle VOIP, then each can basically operate independently but have the system route calls over IP if they're going to HQ.

If they have an existing data-only WAN (i.e. T1s, leased lines, or whatever) then you're okay for the type of system you describe, but keep in mind that if you're talking routing voice over the public internet, you throw quality-of-service out the window and you're pretty much at the mercy of the health of the internet backbones around the world.

Finally, if you decide to pursue this, be aware that there are often unforeseen issues when dealing with phone service in foreign countries (specifically, those whose infrastructure is run by the government). I saw an article recently about a foreign government levying huge fines and threatening jail time when a company eliminated their "local" phone service and routed everything over VOIP. If I can dig it up I'll post a link...

 

[fs483]

For phone service, it's all by satellite right now. They are in remote jungles where there's no electricity at all. My partner had to go there a few times and it takes 2 days to travel by Land Rover after he arrived at the local airport! Everything is powered by large generators. They use SAT Phones when they are off the main campus and use Satellite uplink to communicate data/voice when they are on campus. I think their current link is only at 64Kbs.

Anthony

 

[jpm121]

Ugh. Sounds like an example of when NOT to do VOIP.

Seriously, Anthony, with that kind of bandwidth you'd struggle to support a single conversation, and with the latency inherent in satellite... well, it wouldn't be pretty.

 

[jimbopalmer]

Anthony what is their data network like, cause their voice is ugly already.

I tried to remain child-like, all I acheived was childish.

 

[fs483]

I don't have the details at all. I get bits and pieces of information, through a few people. The people who installed it aren't there anymore and the people who work there now don't know much about other than it works, not very fast and not always reliable. I know that on one site they had a lot of trouble with the generators. Kept on frying all the hardware even with a 50 000$US UPS. Lucky it was under warranty and they ended up putting a 100 000$US UPS. It has held up so far. I heard that when it gets stormy out there, they have a really bad connection. One thing is for sure, if they do decide to go VOIP, they will be handling that themselves and hopefully sub-contract that part out to specialized company. We are going to handle only the setup for the servers in the HQ. We won't even manage the workstations, it's not worth the 2 hour drive just to reinstall Windows 98 on a workstation ...

In the case of VOIP, should there be two different networks (one for voice and one for data) ? That way wouldn't it be much easier to guarantee QOS ?


Anthony

 

[AdmanOK]

If the only network option you have is over a satellite link then you can forget doing VOIP... the moment your latency goes over around 250ms it just stops working. If you don't have a stable, low latency network then it's just not worth your time trying to run a VOIP phone system. I guess we're just going to have to wait a few more years and hope that Teledesic makes it online in our lifetime!