how much bandwidth needed

[sruzila]

The company I work for is starting to invetigate using VoIP. We have 6 offices (2 in DC, NYC, Boston, and 2 in Dayton). Each office has a T1 line(frame relay). The ttwo DC offices have about 12 people each, boston has about 24, NYC about 24, and Dayton has about 100. What is the best way to figure out the amount of bandwidth needed? Right now we have a 10/100 switched (dumby, non cisco switches) and 2620 routers. What upgrades would you recommend?

Thanks,

Steve

[s5rch]

Steve,

Are any of your offices "Call Centers"? How stable is your network today? Are you planning on purchasing additional circuits for redundancy? What IOS software are you currently using on your routers? In your company can you afford to be without voice/data for a day or a matter of hours?

[sruzila]

We don't have any call centers. We are looking into getting additional bandwidth right now. I'm not 100% sure what the IOS is on the routers (we were given them by MCI, but they were brand new when we got them 6 months ago). We can afford to be down for only brief periods (hour or so)...but would prefer 100% up time.

steve

[adignan]

1) how many active voice calls are there going to be over the WAN link , g711 takes about 88k of bandwidth per call and G729 taks about 28k per call.

2) does the telco support FRF12 on the frame relay link ( fragmentation need to fragment the packets to 840 bytes)

3) How much other realtime traffic on the WAN link

I would recommend using g729 for your voice codec over the WAN and stream MOH from the local router. Secondly, what is your CIR on your frame-relay links? Typically, with VOIP over Frame using QOS your max bandwidth will equal your CIR. So, if you have a 768 CIR but can burst to 1.5. When you add voice and QOS you will lose that bursting capability. So my second recommendation would be to add a second PVDM for voice to each location or add point to points.

As for switches, your best option is to move to Cisco powered switches. That will be the easiest option as it will power your phones and you will get the benefits from the Cisco switches.

As for Routers, the 2620 doesn't necessarily need to be upgraded but we would have to investigate upgrading memory, etc and look at the PSTN requirements for each location.

Bandwidth Calculator:

http://tools.cisco.com/Support/VBC/do/CodecCalc2.do

My .02 cents,

Andy Dignan - http://www.berbee.com

[sruzila]

My login won't allow me to use the tool (why does Cisco require a login for everything?!).

I know ZERO about IP telephony so you just blew my mind.

1). Best estimate for active calls will be 20% of the people at the office at any one time. (We have differernt sized offices).

2). Don't know...I'd have to check with MCI/UUnet.

3). The other traffice is directory syncing, file access, email (lots), and web.

Steve