VoIP Explained

Updated: October 01, 2009

VOIP Explained

A white paper by Pierre Kerbage

VP of Sales & Marketing

Pierre@Zultys.com

(408) 328-5423

www.zultys.com

VoIP (Voice over Internet Protocol) phone systems can be mystifying to many people. A "system" is by definition a group of items forming a unified whole. VoIP PBX phone systems vary greatly in their features, capabilities, size, form factor, telephone carrier service connectivity, cabling, connected phone sets, etc. Although VoIP technology has evolved greatly over the past decade, such fundamentals of IP PBX systems as how they operate and what they require to perform reliably has not changed. That is the focus of this paper.

  1. And, a definition for "protocol" is that it is just a technology rule or standard, in this case for enabling the transport of voice data packets over a network. That network can be a local area network (LAN) that is within a building, a wide area network (WAN), and yes, the Internet itself.

If using the Internet, connectivity to the IP PBX is achieved through SIP (Session Initiated Protocol) trunks (lines) and the communications are managed by an Internet Service Provider (ITSP), the equivalent of the "phone company". SIP represents another industry standard protocol, and the trunks can be a broadband T1 circuit, DSL, Cable Modem, etc.). If one uses SIP trunks, does it then preclude standard connectivity to the public switched telephone network (PSTN) using analog trunks and/or a Primary Rate Interface (PRI) circuit? No. All can coexist on the PBX opening up a new world of communications capabilities and savings including remote worker communications, inter-office system integration, least cost routing of phone calls including international calling, unified communications, effective "find me" routing of calls, lower line costs, etc.

As a result, Zultys' MX line of IP PBX systems allows our customers to be able to use a variety of trunks in the most effective way. For example, a company might use PSTN trunks for most of its inbound or local outbound calls while using SIP trunks for lower-cost long distance calls. In fact, that company may use two or more ITSPs on SIP trunks. One for domestic long distance calls, one for international calls and several that have a low rate for calls to a specific country. Moreover, the Zultys MX automatically manages these least cost routings greatly reducing communications costs. IN MANY CASES, THESE SAVINGS ARE SUFFICIENT TO PAY FOR THE PHONE SYSTEM ENTIRELY!

OK. However, can you depend on SIP Trunking for providing business-level communications?

Yes. IF it is done correctly!

Briefly, the way VoIP works is that voice energy at the phone is converted to packets of digitized voice data that are transmitted over data networks and then reconverted at the destination. Each SIP conversation typically requires 84Kilobit of network bandwidth. (The use of voice compression algorithms can reduce this need.)

So, here is how to roll out CORRECTLY a VoIP phone system in your Enterprise:

1) Decide if your voice network and data network should be converged onto one network or if it would be better to keep them separate.

2) If converging the two onto one network, perform a DETAILED network analysis. Will it be able to have adequate bandwidth, can it provide for a guaranteed quality of service (QoS), is your firewall VoIP-friendly, etc? An analysis by a qualified, outside firm often is a worthy investment.

3) Ensure that your network is cabled properly for the phone sets (CAT 5e is the minimum today and CAT 6 is quickly becoming the de facto cabling standard with video communications a growing requirement. Test your cable structure. Are any cables pinched or noisy? Be sure that none of your cables exceeds 100 Meters in length.

4) NEVER daisy chain switches (switch to switch) - this piggybacking causes major slowdowns of network traffic, affects QoS and can cause unpredictable results.

5) Remove all network hubs.

6) Use single, layer 3. QoS, power over Ethernet (PoE) Switches.

7) Use enterprise-level antivirus software on all servers and client PCs.

8) Ensure that you have running a business class, server-based spam filter appliance or a hosted spam filtering solution. Hosted anti-spam systems have the advantage of filtering the spam before it enters into your network.

9) Monitor which users are abusing your network bandwidth e.g. are users running applications for downloading music or streaming video or audio all day?

10) Require DEDICATED BANDWIDTH for your SIP trunks. Some providers also allocate additional bandwidth dynamically when required, giving priority to voice traffic.

11) Ensure that QoS routers are used end to end - meaning the provider has a QoS router(s) on its end, as well.

The investment in this structure provides for a high ROI by having optimal and reliable corporate voice and data communications.

Now, let us look at the requirements you need for your single office, home office and traveling staff to connect to your phone system. Each one needs a SIP phone (or SIP Softphone) and access to a broadband connection, of course.

Most likely this broadband connection is a consumer grade DSL or cable modem service that provides asymmetrical upload/download bandwidths, Additionally, the actual bandwidth available can vary widely depending on the number of other subscribers of the provider that are using this shared network at any particular point in time and how they are using it.

To best minimize connectivity problems with remote workers:

1) Have the worker test that Internet service provider's speed by having running any of the free test tools available on the Internet. Insist that they have the ISP correct a problem. (A service speed upgrade for the service may be needed.)

2) Have them use a modern, quality router/firewall that includes QoS functionality

3) Ensure that everyone on their network is running quality malware-prevention software on all PCs and that all PCs are current with the latest security updates.

4) Finally, the PBX must be programmed to route 911 calls received from the remote worker's phone to the proper, local 911 location for that worker.

With these preparations, you will end up with a powerful, reliable, excellent communications system.

And, excellent phone communications is the hallmark of successful companies.

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