VoIP Deployment 

Is your network ready to take on more load from technologies like VoIP? Let's find out

Friday, October 01, 2004

Deploying new applications and technologies on an enterprise network is always a challenge for the concerned managers, right from the technology officers to network administrators. They have to balance productivity with costs, and integrate it all with the existing infrastructure. Other issues that deserve priority are-troubleshooting, teething and compatibility problems during the initial stages, and performance tuning and maintenance later.

Talking about all the new application and technology deployments in one article is not possible. So we have taken the example of deploying VoIP on a network. A lot of organizations, today, are considering converging voice and data on the same network, and, therefore, need to ensure that their existing networks can take on this additional load. For this, you'd have to analyze your existing network for congestion, and in case you're planning to use VoIP over your WAN links, then you'll have to work out the bandwidth requirements for it. This analysis will also vary depending upon the level of implementation you're planning. 

How much bandwidth?
This is the most commonly asked question on a VoIP network. That's because voice is much more sensitive to traffic congestion, on the network, than data. When implementing VoIP over a LAN, you obviously have much more bandwidth at your disposal. Therefore, you can configure VoIP devices to use a more bandwidth-intensive codec, such as the G.711, which consumes up to 87.2 kbps of NEB (Nominal Ethernet Bandwidth) in one direction. This will ensure better voice quality. In addition to this, you would also need to analyze the existing traffic patterns on your network. If it's already congested with a lot of broadcast traffic or other bandwidth-intensive applications, then the response time would be higher. This in turn will affect the voice quality of VoIP calls. You might face breaks or choppy voice due to this.

You can calculate precisely how much bandwidth a VoIP call can consume from various sites on the Net

While deploying VoIP on LANs, experts recommend that you create a separate VLAN (Virtual LANs) on your network for IP telephony. This will keep the voice and data networks separate, and anything happening on one will not affect the other. For this, you'll also have to ensure that you're using manageable switches on your network, which support VLANs. Having a separate VLAN will also ensure that your VoIP network remains unaffected from security threats that might occur on the data network. A DoS attack for instance, would affect a VoIP network much more adversely than a data network. 

The key issue in deploying VoIP over WAN links is that you have limited bandwidth. So you have to start by determining how many simultaneous voice calls you'd want to hold over your WAN links. Then determine how much bandwidth would be consumed by each voice call. For this, you have to take into account the compression technique to use, the payload size of voice packets, and the type of link used for VoIP communication. There are a lot of different codecs that can be used for VoIP communication, supporting bit rates that range from 5.3 Kbps to 64 Kbps. Using the codec data along with the payload size and type of link, it's possible to calculate the amount of bandwidth required per call. You'll also find a lot of bandwidth calculators available on the Net to help you with this job. One good link for this is www.voip-calculator.com. There are also several good software tools that can help you. Check out www.ixiacom.com, which has some specific tools to help you with VoIP deployment. Plus, they even have other tools to help you calculate the response time and throughput on your network. 

Ensuring Quality of Service 
Once you have calculated the bandwidth required for VoIP, you have to ensure you're your voice calls get that much bandwidth. This is when you have to enforce the QoS policies, else, you will get poor quality reception, delays, jitters, missed speech or even dropped calls. Typically toll quality calls require at least 16-20 kbps of bandwidth. QoS is normally controlled at the router level. Therefore, you'll need a router that let's you configure QoS for VoIP packets on your WAN links. 
You can also deploy switches that support QoS for VoIP on your LAN. There are also some  bandwidth-management solutions available that support QoS policies. 

NetIQ's Qcheck is a good tool to determine the response time and throughput between two endpoints on your network. This can help determine how congested your network is

Handling power problems
This one may come as a surprise, but yes, you will have to do some power planning while deploying VoIP. For instance, unlike normal phones, most IP phones require their own power supplies. So, in case of a power cut, they would stop functioning unless you've provided power backup for them. Calculate how much additional power your VoIP equipment requires, and check whether your existing backup equipment can take on the additional load. Many IP phones also support PoE, or Power over Ethernet, in which case, additional power backup may not be required. 

Security issues
While a regular PBX is not under security threats that normally occur on a data network. However, since VoIP deployment occurs on the same data network, it's also vulnerable to similar security threats. For instance, while a circuit-switched voice network requires a PBX switch, VoIP deployment requires servers that will act as the gatekeepers or voice gateways. These would run some standard software applications, which could be vulnerable to virus attacks, or other security threats.

Therefore, these servers require the same type of care, as you'll give to other servers on the network. Subject them to the same routine maintenance, take regular backups, do security checks and install anti-virus software, etc. 

You would also need to implement VoIP performance analyzers such as 'Appmanger 6.0' from NetIQ to check for smooth functioning of VoIP.

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Technical issues in deploying VoIP

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