Voip Comparison

VoIP Query: Where can I get a precice and concise "In a Nut Shell" summary of VoIp functionality?

I am a trained network engineer from being in the US Air Force. I am heavy on Cisco followed by Windows etc..and multiple IT Certs.. I moved from the assignment right about when we started installing VoIP and Wireless gear but didn't get to enjoy playing with them. I am going to do a thorough review of the VoIP technologies and try out either an inexperienced capacity or an internship to bolster that. If you are aware of any of the above feel free to make me part of your social network..I need to make use of those skills on payroll be4 it's too late to be any good.. Another hurdle is that when I was doing most of my certs, the technologies were more infancy stages: However of the: CCNP, CCDP, and CCSP that I hold, CCDP had the greatest high level assessment of voip and wireless

Public Comments

1. Very good question. Let's consider the old days of telephony. Suppose we have a company with a location in CA and a location in NY. In the days of TDM before VoIP, a company may have something like 2 point to point T1 connections. One would be be strictly for voice using all 24 channels of the T1 for phone calls, one call per channel. The second T1 would be used for data traffic (1.544mbps) This worked fine until companies began to realize that maybe they never actually had 24 concurrent phone calls and maybe they never hit 1.5 mbps of throughput over their data T1 but they were paying for 2 seperate T1 lines (which definitely is not cheap, especially in our example) They realized they could use a single T1 and instead of using it for only data traffic or only voice traffic. They could say, ok we want 12 channels of the T1 for phone calls and the remaining 12 channels for data. They just took a device and did something known as drop and insert where your 12 voice channels would be dropped off to your PBX and your 12 data channels would be dropped off to your router. Again, this worked fine until companies said something like, hey, at 4 in the morning when we're doing our data back ups and all of our employees have gone home for the night (no one in the office making phone calls) we're still limited to our x amount of throughput for data since a portion of of our T1 connection is allocated for voice traffic. Why can't we just packetize our voice traffic into data as it passes over our T1 line. Enter VoIP. Take our analogue voice traffic, convert it to data using a codec like G.711 or G.729, pass it over the T1 and have a device on the other end to convert it back to an analogue signal. Taking this a step further, with VoIP, you still have your analogue phones and PBX. IP Telephony on the other hand, is a step past VoIP. Instead of analogue phones, we have IP Phones, like a Cisco 7941G for example. Instead of a PBX, we have a server to handle the call processing. We can replace a big bulky PBX with a 1RU server. In the world of Cisco, this is known as Call Manager (now known as Communications Manager). Even better, in the world of Cisco, we can have all of our call processing done on a Cisco Router with Call Manager Express. Pretty cool stuff. With an analogue phone, you're very limited to what you can do. With an IP phone however, you can check the weather, find information about your flight status, do video conferencing etc. The cost savings here is one thing but the various applications that you can do with this are a whole other story. I hope that's a helpful crash course. Jason CCNA, CSE, CCENT, Network+
2. nice crash course oalos255
3. http://communication.howstuffworks.com/ip-telephony.htm see if this helps or you could check on wikipedia.com