VoIP setupd on Cisco Network 2

[VoipNewbie]

Hey Everyone,

I am a complete newbie to VoIP. I am looking for any guidance anyone can possibly give me on where to start in planning a convergence of my NEC voice network with my Cisco Data Network. I am hoping to move everything to cisco products. Is this possible? Are there any good books anyone recommends? Any help at all will be greatly appreciated!

Thanks

 

[computerhighguy]

Not quite, but close.

You need a call processing system. So you have to have either Call Manager or Call Manager Express.

Then you need a gateway to the PSTN. That is the AS5350.

After that, it is all about IP routing. The VG248 has an ethernet connection. you would use that to connect into your network. You will need a valid route from the VG248 to the Cisco Call Manager (CCM) and to the PSTN Gateway (AS5350). The VG248 communicates via IP. There are some latency issues, but you probably won't have much to worry about. Hope that helps.


It is what it is!!
__________________________________
A+, Net+, I-Net+, Certified Web Master, MCP, MCSA, MCSE, CCNA, CCDA, and few others (I got bored one day)

 

[VoipNewbie]

So then technically i could put a VG248 into my dormitories and let the students still have an analog phone. correct? Then i just plug the vg248 into one of my existing data switches there. Then how do i bring that to talk to the AS5350? Do i just plug this box into the network?

Of course i will have this traffic on its own vlan and have it routed to go to the right places.

The call manager is more of a software than anything correct? Or is it a point where all voice traffice will pass through such as a server?

 

[computerhighguy]

I need to explain this in different terms.

In your pbx system now, everyting comes into the PBX. The phone, the PRIs and the PBX does the call processing (switching is another name).

Call Manager does basically the same thing, but instead of having one box do everything, it is a distributed architecture.

You need a gateway. The AS5350 will do. When a call comes in, there is a route list of sorts called dial-peers. Depending on the DID number, it matches a dial peer and is routed to the appropriate call processing system or gateway. Lets say that it is an incoming call for a number assigned to port 1 on the VG248. The AS5350 send the DID and call setup information to CCM. CCM then checks to see if the call is forwarded to another number, forwarded to V-mail, is the pilot point for a hunt group, etc and processes the call accordingly. Lets say that the phone on port 1 is not setup to do anything special. CCM will release the call from the AS5350 and tell it where to go. CCM, at this point, technically isn't involved anymore and the AS5350 and teh VG248 negotiate the end to end voice stream (i.e. codec to use, VAD setting, does the call require a transcoder and if so which should be used, etc). CCM does not proxy the call (unless it is transcoding the call) and just hands it off.

The cool things about VoIP, is that you no longer are concerned with distance of the phone to the PBX, but rather IP latency and quality. So, if you have a VPN connection from your house to the office, you can put a phone there and have it connect up to the CCM system.

CCM is considered a soft PBX. It does all the traditional functions of a PBX, but does it via software.


It is what it is!!
__________________________________
A+, Net+, I-Net+, Certified Web Master, MCP, MCSA, MCSE, CCNA, CCDA, and few others (I got bored one day)

 

[VoipNewbie]

Ah yea that makes alot more sense to me. You have been an extremely good resource to helping me understand this. I cant thank you enough for your time and knowledge.


Call manager basically takes place of the PBX telling the call where to go. The the AS5350 gets the call and the route and figures out which VG248 to send it to...

Can the VG248 support IP phones? or do i just plug an IP phone into my existing switch architecture?

 

[computerhighguy]

You almost got it.

The AS5350 is the gateway to the PSTN and decides how to route an out going call (which PRI) and how to route an incoming call to a call control system (i.e. CCM, an H323 gateway, another router, etc). Once CCM gets the call (well it doesn't actually get the call under most circumstances, it more than likely tells the gateway how to route the call. That can be voice mail, ring the subscriber, a conference bridge, forward back to PSTN becuase call forwarding is enabled, etc) decides how to "handle" the call within the CCM landscape.


To use an IP phone, you simply register the phone's mac address with Call Manager and pug it into the network. Well there is a bit more to it than that. The phones and the VG248 boot up and typically get a DHCP address. CCM uses DHCP option 150 to specify a TFTP server (SIP uses option 66 i blieve). The TFTP server will contain a file that has all the information for the device such as which firmware the device should be using, where the firware is lcoated, which CCM server should be the primary, which is the backup).

There is a call manager forum on Tek-tips. I would suggest posting questions on there. You will get better answers.


It is what it is!!
__________________________________
A+, Net+, I-Net+, Certified Web Master, MCP, MCSA, MCSE, CCNA, CCDA, and few others (I got bored one day)

 

[VoipNewbie]

Well thank you very much for all of your help yet again... You have given me extremely useful information. I appreciate your help and patience.