IP Convergence: Beyond VoIP, Beyond Cost Savings

Interesting to see how the market is moving towards convergence applying Voice Over IP to new network models.

The folks at GigaOm have recently tested VoIP on the GoogleFi Mountain View network.

Their preliminary testing yielded good results, however is it really representative of consistent performance?

VoIP requires that a network provide deterministic performance , aka Quality of Service (QoS). Global Crossing’s network based MPLS IPVPN understands the difference between Voice packets and Data packets and insures that Voice packets get priority and the proper performance needed.

However in a Wide Area Network (WAN) , QoS begins at the WAN router connecting a site to the WAN. This router needs to understand QoS of packets by prioritizing voice packets over data and managing out going buffers as well.

The problem with WiFi is that is was designed and optimized for high bandwidth applications transporting data. The specification 802.11x defines the Media Access Control (MAC) layer as to how a transmitter transmits packets over the air. So when 2 transmitters are trying to use the same frequency there’s a chance they might collide – kinda like Laurel and Hardy trying to get through the door at the same side. But that’s ok, the MAC layer expects these occurrences and data can be retransmitted.

That is why there’s a new WiFi specification – 802.11 E, that provides a better MAC layer that understands the issues of transmitting voice packets.

I think we’ll find that VoIP on WiFi not using 802.11 E works sometimes and not others.