Is Your Network Ready for VoIP?
by Jeff Barker , Director of Product Management
Packeteer.
For years, VoIP has held the promise of enabling the next generation of voice communications within the enterprise. Unfortunately, its adoption has been slowed --- sometimes by the reality of poor performing IP-PBX systems; in other cases, by perceptions that VoIP technology is not quite ready for prime time. These problems --- both real and imagined --- have forced IT organizations and VoIP vendors to take a closer look at the technology and ensure that IP-PBX solutions deliver the features, quality, and reliability that customers demand.
With a new generation of mature, reliable solutions, VoIP is once again building market momentum. As vendors and customers begin to implement strategies to move from a traditional TDM-based circuit-switched PBX to a converged IP voice and data network, an increasing number of enterprises are trying to understand how their existing network can handle the convergence of voice and data traffic without compromising performance and reliability of existing applications. This article addresses many critical issues pertaining to VoIP's viability, regardless of which vendor's IP-PBX system is deployed across the distributed enterprise.
Considering Migration? - Think Network Assessment and QoS for VoIP and Other Applications
VoIP quality and reliability depends on a lot of things, including (but not limited to) the IP-PBX system used for voice communication, the networking equipment used to carry voice and data traffic, the amount of bandwidth available to all sites and users, network latency and jitter, and the total amount of traffic moving across the network. VoIP quality is not typically an issue within LANs where bandwidth is plentiful and latency is essentially non-existent. The most significant point of congestion and potential voice quality degradation is the LAN/WAN boundary. Here, all traffic (VoIP and data) must be monitored and controlled as it transitions from the LAN to a far more bandwidth-constrained WAN link.
It is possible that you may need to increase the size of your WAN links to support VoIP traffic, but it is not advisable to increase bandwidth without first adopting a sound Application Traffic Management strategy. Why? Because the problem typically is not overall capacity, but the transient congestion resulting from less important, more aggressive, competing traffic. The underlying protocol (IP) allows applications and/or users to consume all available bandwidth. So simply adding more bandwidth without proper visibility into traffic types and patterns and bandwidth management to control how applications are apportioned bandwidth may only result in adding more traffic and expense --- rather than improving VoIP performance.
A comprehensive Application Traffic Management system provides visibility, control, and compression to minimize voice and data traffic congestion and ensure end-to-end performance that satisfies SLA objectives.
As suggested above, before planning any VoIP deployments or making investments to upgrade WAN links, you must have adequate visibility and control of your existing WAN links to be sure that you are generating maximum performance and value. The best place to start is by understanding exactly how your WAN bandwidth is being used. Recent studies reveal that 75 percent of network managers do not have full visibility into their WAN traffic.
Without application-layer visibility, it is impossible to effectively prepare your network for voice traffic --- and that's when the problems begin. An effective Application Traffic Management system can provide this capability. The appliance-based systems auto-discover all application-level traffic running across your WAN links, including critical business applications, email, FTP file transfers, Web surfing, P2P applications, malicious traffic and more. Users are always surprised to learn that a significant portion of their WAN resources is used for recreational activity. Application Traffic Management system immediately controls and/or blocks this traffic --- a critical step toward a successful VoIP deployment. The same capabilities are also valuable in ensuring the performance of business applications, protecting them from the less important traffic like casual web browsing and music downloads.
It is also important to determine how much bandwidth is required for optimal voice quality across the WAN, users must first decide how many users VoIP will support, as well as their average call length and call volume. Well-established phone metrics usually available from VoIP vendors can help make that determination. In addition, the codec you select (discussed further below) will influence bandwidth requirements. VoIP Performance Challenges
Once you've determined bandwidth requirements and gained visibility into my WAN, there are some other critical VoIP performance challenges that need to be addressed.
