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Wireless IP Phones + IP Communicator

Hello all,

I have a request to set up a whole wireless network for my company with controllers and 8 LWAPPs...and they also bought the wireless IP Phones 7921G and now that we're going to have a good wireless network, I have some people that use the IP Communicator on their laptops, which normally, they would have to plug their R45 cable, and NOW they want to use the wireless network to use it.

So my idea is:

Have 3 WLANs:

- Data WLAN for most laptops with 802.1x+WAP2 auth (we have an ACS)

- Guest WLAN without authentication and restricted to just internet (passing by a firewall)

- Voice WLAN (Hidden,No SSID Broadcast,MAC Address Filtering) JUST FOR THE IP PHONES 7921G.

Apply QoS to the Voice VLAN, (Platinium.... i think)

Now my question is.....what do i do with the laptops that HAVE IP Communicator...they would have to go in the Data WLAN...but would the WAP2 be an issue????

Please help!! i have til next week to do my design plan!!

Thanks in advance

1 REPLY
VIP Super Bronze

Re: Wireless IP Phones + IP Communicator

VoWLAN is a mess outside of the 792x phones on a dedicated SSID. The main problem is that 802.11 doesn't have the same prioritization mechanisms that Ethernet does. The 792x phones have a major amount of protocol and timing tweaks as well as ancillary protocol support, such as WMM, that is not viable for normal data SSIDs. Cisco had to do a lot to make voice viable across 802.11.

The best I believe you can do is ensure the wireless NIC in the laptop supports WMM and to enable it on the data SSID. If the laptop NIC drivers support WMM, Windows should automatically tag the voice packets. You can hedge your bets on this front by enforcing a Group Policy Object that ensures IP Communicator signaling and media packets are marked with DSCP.

You'll want to pay careful attention to what DSCP markings the packets pick up once they exit the WLC onto the network. They will likely be wrong because they arrived on the data SSID. One way to deal with this is to consider using a Trusted Relay Point for soft phone devices. The TRP will proxy the media through a MTP to ensure it gets marked properly.

PS- I strongly suggest you read the VoWLAN SRND and not stray an inch from it. Experience has taught us that they were not padding the margins when they came up with those AP densities. You really have to have amazing coverage for stable VoWLAN. If not, you'll get sporadic reports of audio interruption.

PPS- The 7925 has about a -7 to -8db lower signal reception than the 7921. Be careful with your signal strength; just because the AP can blast out doesn't mean the phone can make it back to the AP.

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