atcomsystems.ca/forum Forums TDM Business Telephone Systems Mitel Telephones & Systems IP phones slow network?

Has anyone experienced a slowdown of speed on a network with IP phones on the network? (pc's are running through the phones pc port)

More of anything on the network will use bandwidth. The more devices the less bandwidth available. Voice will take priority over data.
Increase bandwidth to help resolve the problem

Are you using VLANS?

20 mbps, one building is consistently running 18-20, next door is all over the place. Cabled network all to the same switch.

Without compression, each phone will take 64K of bandwidth. That gives you a max of 24 phones on a standard T-1 or equivalent. 20 phones on a T-1 will be 5/6 of capacity. 20 phones on 20Mbps should be barely a blip.

Consider using compression, such as G.729.

Also, look for circumstances in which a call is being routed back and forth across the links. For example, comes in to PBX, is routed to remote office IP phone, forwards to voicemail, presses three for customer service back across the link, conferences with another office, etc.

Networks are fragile. The existing LAN networks are really a kludge mess of barely workable topologies that can pass data, but not very well.

Consider a typical 24 or 48 port switch. Switches can be layer 1, 2, 3, 4 or 7 of the OSI model. Most basic networks may have layer 1 or 2 switches and the better designed will have layer 3 managed switches. Just because a switch is labeled 1 Gbs or 100 Mbs does not mean 24 or 48 connected devices are simultaneously sending and receiving sustained data at 100 Mbs or 1 Gbs. These switchs use a method called load sharing which may limit the amount of bandwidth available at any given time to any or all devices.

Now, understanding the physical limitation of a local network and then throw in the WAN and maybe even another node on a WAN that you are on a network with, then you begin to see how data rates are, at best, nominal and, on a large busy network, barely able to sustain normal data traffic. Even with good, managed layer 3 switches and a really well designed LAN, you have no control over the bandwidth once the data leaves your local network.

I think VoIP is a solution looking for a problem. In my opinion, it's not really ready for prime time. Everyone wants in on the "latest and greatest" however, this isn't the "greatest" or even "good." Until one can truly control and tightly manage a network from end to end and everything in between, there is no assurance that a VoIP system will work as well or, as advertised, "better" than a wired, digital system. The KSU/PBX with digital phones running on dedicated wiring is the "best" LAN system for voice. The modern telephone systems have utilized this managed and controlled LAN for years because there was no "foreign" data to deal with on a KSU/PBX to telephone system.

If you remember the old formula, Gi=Go, you will have a better understanding of why LAN networks are poor vehicles for voice AND data traffic.

Rcaman

You should always test a existing network before adding voice.