atcomsystems.ca/forum Forums VOIP Phones & IP PBX Cisco Telephones and Systems Cisco phones and bandwidth

I have also posted this in the installers thread -

I would like to ask a question that may seem stupid to most of you but here goes.... I am bidding on a wiring job in which all the wiring in the premise will be upgraded to Cat5e so they can swap out their existing Nortel MICS to a Cisco VOIP system. I don't know what model of Cisco phones, but my contact said they had a data port on them in which their PC's would be connected. How much bandwidth will the Cisco phone rob from the PC? Obviously, since the phone and the PC are sharing the same cable, the PC will not have the same bandwidth it would have if it has its own Cat5e drop.
Having read so much negative stuff about Cicso VOIP, I feel like I need to run two Cat5e to each station.

Thanks for any input,
Bill

The sites we have seen lately have been installed with separate data drops for voice and data. Probably beacause of POE concerns. I'll try to dig up more info on this subject.

I'd quote it for separate drops. Bandwidth won't really be an issue, but from a reliability standpoint hanging the PC off the phone can be problematic.

- It makes remote troubleshooting more difficult. Is the problem the phone, the link from switch to phone, or the link from phone to PC, etc.

- The failure rate for VOIP phones is not insignificant. Phones get abused. Patch cords get yanked, stretched and crushed.

- Quality switches are designed for a specific purpose. The switches built into phones are a convenience feature. Great if a visitor can't find an open port for their laptop, but not the kind of thing I'd want to rely on everyday.

Semi-funny story - A couple of weeks back we get a call that one of our sites is having serious bandwidth problems. The switch is acting crazy, can't be reached reliably via HTTP or telnet. Even the serial connection to the routers is hosed. T1 is clean and the router is OK. I'm elected to drive the 3 hours to the site and replace the switch. No change, so I have a look around, start moving desks, etc. I note a number of phones with PCs hanging off them, despite open ports in every wallplate. One phone in particular looks strange. Someone had removed the cable from phone to PC and plugged the loose end back into the wall, creating a perfect loop! The person who occupies the desk in question had left for vacation earlier in the day.

:bang:

Naturally, spanning-tree was disabled in the switch by a network admin concerned over the initial performance hit. Besides, "No user could possibly be stupid enough to do that."

Dual runs require twice the number of Ethernet ports. We have installed well over 1200 IP telephones at about 30 locations and everyone of those customers has the line run from the jack in the wall to the telephone and then to the PC.

"Dual runs require twice the number of Ethernet ports. We have installed well over 1200 IP telephones at about 30 locations and everyone of those customers has the line run from the jack in the wall to the telephone and then to the PC. "

Hope those are good phones
I was told by my previous employer to do a couple of jobs like that. Hated doing it, but only had a couple of small issues. Telrad IP.

Regardless of cabling choice, I tell customers to figure about 98 kbps per Sip call when using G.711.

Double that for remote (internet) calls that need to have remote audio forced through the server for firewall or other issues.

Here are a couple of links to help calculate bandwidth requirements for situations:

https://www.newport-networks.com/cust-docs/52-VoIP-Bandwidth.pdf

https://www.cisco.com/warp/public/788/pkt-voice-general/bwidth_consume.html