In your initial VoIP analysis, consider whether your network can handle voice traffic. The rule of thumb is you need at least a QoS-capable 100-Mbps Ethernet backbone but ideally you'd have Gigabit Ethernet. If your infrastructure is built on professionally installed and certified Cat 5E or higher wiring, your network's physical layer meets the minimum VoIP requirements. If you're thinking about adding gigabit to your legacy Cat 5 wiring, you'll need to retest it to ensure it can support the upgrade.
Other things to consider: Does your data wiring exist everywhere you'd like to add a VoIP set? What vintage are your switches and routers? Does your network have the benefit of a reliable, balanced and backup-protected electrical power-distribution system that can sustain uptime during an outage? Do you have network management tools, such as NetIQ Corp.'s VoIP Manager or Brix Networks' VoIP Test Suite, that can analyze packet-level performance and detect jitter, delay and latency?
A successful VoIP operation comes with a well-planned, modern and soundly implemented network. If your network is running on hubs or geriatric 10/100 switches and Cat 3 cables, replace them before you start setting up the VoIP call-processing hardware. In our case, we ditched our Cisco Catalyst 1900 switches in favor of new Catalyst 3500s to get the QoS, VLAN and power-over-Ethernet features we needed. If you have wireless networking, check whether your wireless access points support QoS parameters so the voice traffic gets priority when it hits the network's wireless segments. This may be tricky: Few of today's wireless devices come with QoS options.
Your network may need more than new switches and data wiring. Before you buy your VoIP equipment, build redundancy, failover and high-availability power distribution into the network. Uptime is crucial for voice: If you lose a segment of the data network, at the least it's inconvenient and at the worst you lose revenue and customers. But if that same segment carries your voice service and fails, you could face liability and would certainly lose clients. How you configure the Spanning Tree protocol and self-healing on the network and in the server farm can make or break the voice-call experience--and your VoIP infrastructure.
And don't forget your staff. If your helpdesk is divided into separate voice and data support staffs, be prepared for the sensitive process of merging them.
One of the most worrisome issues we grappled with during our test implementation was how to mesh our new VoIP solution with some big-dollar applications--account provisioning, cable-plant management, departmental telephone billing and helpdesk systems--that we had rolled out prior to the IP voice pilot. Even now, we still haven't quite figured out how to integrate those systems with a large-scale VoIP rollout. Our call accounting system, for instance, is based on our legacy Nortel Networks DMS-100, so it obviously wasn't a natural fit with Cisco's Call Manager-based AVVID.
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