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 The Business Phone Blog


Wednesday, May 23, 2012 | by Tony Dunphy


By Steve Woods from VMCN Our Alcatel PBX supplier

ISDN & VoIP - potentially a marriage made in heaven!

And by 'potentially' we imply if done right the call quality and reliability of isdn, combined with the flexibility and cost savings of VoIP offers small businesses potentially - the best of both worlds.

Some background

The ISDN or Integrated Services Digital Network is the gold standard for business communications.  It is available Australia wide and is owned, operated and fully managed by Telstra, with all services generally available via 3rd party telecommunications service providers nationally.

Integrated services refers to ISDN's ability to deliver at minimum two simultaneous connections,  in any combination of data, voice, video, and fax, over a single line. Multiple devices can be attached to the line, and used as needed. That means an ISDN line can take care of most people's  complete communications needs (apart from broadband Internet access and entertainment television) at a much higher transmission rate, without forcing the purchase of multiple analog phone lines.

Why is ISDN favoured for Business Use?

Digital by Design - Being a digital technology delivered from a fully monitored and managed network, ISDN offers superior audio quality and extremely high reliability over comparative  services such as Analog PSTN lines or GSM (Mobile Phone Lines).

Anywhere and Everywhere -  Due to the wide availability and uptake of this technology most Phone

Systems and ISDN capable premises equipment are affordable, and easily supported by a broad range of vendors and maintainers - which helps keep total communications operating costs under control.

Killer Feature - ISDN has one massive advantage over all other traditional communications  options, and this is referred to as Direct Inwards Dialling or DID. With DID, businesses rent a number of virtual phone numbers usually in blocks of 100 from their service provider. Each of these virtual numbers can be answered directly by the phone system / PABX (Private Automated Branch Exchange) and translated direct to an extension or handset.  This means that we can now have more extensions or handsets than actually phone lines (big saving) and we can  bypass reception to receive our calls direct to our own number (massive saving)!

What's the Catch ?

As mentioned earlier ISDN is the gold standard and it's priced accordingly. Because it is flexible, widely deployed and the network is owned by the incumbent telco there is not a lot of direct competition which ultimately sees this as the most reliable and expensive business public  telephone line solution. 

VoIP SIP Trunks are Cheap - I'll just flick the switch

Some background to SIP Trunking or SIP Trunk Services.

For most businesses it's neither  that simple or that easy. VoIP SIP trunks potentially ticks all of the   communications boxes for a small business in terms of flexibility and savings, however few take the time to understand the real costs, benefits, advantages, disadvantages and risks of going VoIP, which consequently sees a large percentage of VoIP deployments ending in tears.

What is VoIP ?

Voice over IP (VoIP) commonly refers to the communication protocols, technologies, methodologies,and transmission techniques involved in the delivery of voice communications and multimedia sessions over Internet Protocol (IP) networks, such as the Internet. Other terms commonly associated with VoIP are IP telephony, Internet telephony, voice over DSL (VoDSL),and SIP Trunks (Session Initiation Protocol).

How does it work ?

Basically, a VoIP telephone call requires signalling and a media channel setup, digitization of  the analog voice signal, encoding, packetization, and transmission as Internet Protocol (IP) packets over a packet-switched network. On the receiving side, similar conversion steps (usually in the reverse order) are required to reproduce the original voice (audio) stream.

Is my network up to it ?

As you might appreciate, the overall performance (Bandwidth / Speed / Load etc.) of IP networks varies  considerably between locations, directions, service providers and technologies. E.g. with ADSL and Cable networks Download Speeds are substantially higher than upload speeds i.e. 4-20meg down and .2 to 1.0 meg up. And it is this performance difference, without exception that makes or breaks a VoIP deployment for a small business. 

 While nearly all appreciate their download speeds...It is the upload speed that most forget when thinking VoIP!  IP Network performance and VoIP is further complicated and impacted upon by the activities ofusers on the networks - i.e. file sharing, web browsing, email and or FTP uploading etc. places different burdens on the network. These activities (unlike voice) are generally tolerant of each other and simply slow down as less bandwidth is available or more users are added. VoIP is not tolerant and does not play well with others.

VoIP needs a minimum  amount of bandwidth and a constant speed to deliver a phone call. IP Voice is Real Time Traffic. Furthermore, our hearing has evolved over hundreds of thousands of years to pick even the smallest of differences in pitch, tone, and cadence of audio frequencies in the spoken word range.

An example : Site A has a standard adsl with 15 meg down & 0.65 meg up and 4 or 5 users,doing light web browsing and email correspondence with few large attachments.  In this case, the network might be say 10% utilised and one or two VoIP calls via this adsl may sound reasonably good.

Now if the same users were a Graphic Design company receiving and sending large attachments, with a few users connected to a cloud based server all day - then this same network might be over 90% utilized. Even a single VoIP call in this case would have to fight for bandwidth, and assuming the call could setup (ring the other end) it's resulting poor audio quality (mostly characterized by echo, jitter, fading, periods of silence or disconnection) would inevitably frustrate both parties.   

Getting VoIP right

 In the smallest of companies, like the example above you may get away with a single adsl service supporting voice and data, however this would definitely not extend to providing a VoIP line and concurrent call for each user at almost toll (ISDN) quality while they were online going about their predominately administrative activities. One sizeable download while a call was in progress would result in some loss of call quality, with the exact impact dependant on file size, link speed, codec used, network configuration, quality of service implementation etc. etc. (will leave QOS and data networking equipment for another day) 

As a guide, we recommend a minimum of a separate adsl internet service 2-8 concurrent VoIP calls.

Any business that needs to have 8 or more VoIP calls in progress at any one time, at a quality level of GSM mobile calls or better should be looking at business grade symmetrical internet access solutions. Depending on your location Options include BDSL, SHDSL, Metro Ethernet, and or Fibre should be available and a min of 1 meg down / 1 meg up speed should be chosen to support the desired call volume and quality. A good rule of thumb is .1meg per VoIP call at analog phone line quality.

VoIP Gets Expensive with Dedicated Internet ?

As you can see, more calls need more bandwidth. There's still no free lunch! For many companies where call quality is very important and 10+ calls are constantly in progress the cost of dedicated internet access for VoIP often exceeds the costs of traditional phone lines.  Couple this with new LAN & WAN hardware (data switches & routers with QOS) IP PABXs, Gateway devices, Analog adapters (for fax and eftpos) etc. and the true cost and complexity of going VoIP starts to materialise. The savings will come, however the technology investments still need to be made up front if call quality and reliability is important to the business.

Have your cake and eat it too

While every businesses call patterns and network are different, for the most part phone calls and data traffic go both ways, with the outgoing calls and the incoming data costing the most money. We said earlier that ISDN is the gold standard, so it makes sense to maintain 'some isdn' from a call quality and phone line reliability perspective, But having too many isdn services may actually be costing you money that might be better invested in VoIP and your ip network.

Similarly, VoIP has a number of advantages over isdn in terms of reduced line and call costs and it offers additional features which help businesses work more flexibly such as easy relocation and portability, unified messaging and mobile extensions etc.

So, to have your cake and eat it to, we suggest the following general approach for businesses with 4 or more administrative users...

- Phone System Review

                  - Buy or rent a phone system if you don’t have one

                  - The system should be ISDN + Direct VoIP Trunk capable or

                  - ISDN + Analog Trunk capable  (VoIP to analog adapters are widely avail at < $50)

- Review your lines

                  - You only need enough isdn channels for the quantity of incoming calls

                  - Migrate any analog pstn lines not used for adsl or alarms to isdn

                  - Rent a direct in dial range (bypass reception, call direct - more efficient)

                  - Cancel any surplus lines

                  - Add VoIP lines for some incoming and all outgoing calls

- Review your internet Access

                  - Add a dedicated internet access for VoIP

                  - Upgrade current internet access to symmetrical

                  - Move to business grade internet and get a service guarantee

- Review your Network & Equipment

                  - Add a router with 2 WANs (1 for internet + l for VoIP)

                  - Check what users are doing on the network

                  - Identify what internet traffic is coming and going

                  - Add a firewall to manage the in/out traffic and to limit non business use

- Engage Expertise

                  - Upgrade the network

                  - Upgrade the internet access

                  - Install some VoIP lines

                  - Configure the network & phone system to suit

                  - Adjust the ISDN vs. VoIP line mix to suit

                  - Review every 3-6 mths

A common scenario relating to the above is that a small company (up to 10 staff) using 4 x ISDN2 services at approximately $350 / month + timed call costs at up to $400 mth (based on an industry average of $50 per extension per month) would be spending around $750 mth for up to 8 concurrent calls.

After upgrading and or reconfigure their equipment and changing their services mix - say, reduce the ISDN line qty to 2 x ISDN 2 (4 lines), add an additional ADSL internet access and 6 VoIP lines, their overall line rental is less, call costs are less and more lines are available - not to mention additional features becoming available such as Voicemail to email, or VoIP softphones on PCs instead of additional handsets in the business etc.

Realistic overall savings in the revised ISDN VoIP Hybrid solution above would be along the lines of:

Line rental for isdn down by up to 50% i.e. $175

Call costs down 20-30% i.e. $80-$120

(depends on call types and patterns - most VoIP providers offer lower costs on local / std / and fixed to mobile calls as well as more flexible call bundling options - such as free on net calls  etc.)

Line rental VoIP up by $0-$50 (some don't charge for numbers / lines - depending on customer call spend)

Internet access up i.e. $75 mth

Savings on a $750 current telco spend could be up to $250 ex gst or more.

Other Investments potentially required

                  - Firewall from $400

                  - Dual WAN router from $300

                  - VoIP / Analog ATA from $50

                  - Pabx / IT hardware

                  - PABX / IT tech services (2-8 hrs.)

Other benefits potentially gained

                  - Maintained the quality and reliability of ISDN

                  - Access to ISDN lines if VoIP is down or network congested

                  - Additional adsl provides redundancy (failover internet to VoIP)

                  - Unified messaging - VM to Email, fax to email etc.

                  - Direct dial into staff / extensions

                  - Portability of numbers i.e. work from home on the office phone number/easy relocation


 If done right - VoIP Works!

If added to ISDN - Business Communication Works Better !

The underlying network and internet access must be in place for VoIP to work effectively and it is at this point of under-investment where most small business VoIP deployments fail.

Furthermore, a large percentage ignore the golden rule of you get what you pay for - and further under invest in the expertise and services to "VoIP ready" their networks.

If that wasn't bad enough some after taking the time, doing the reviews and making all the right investments go with a less than reputable internet telephone service provider (ITSP) ...usually offering the world's  cheapest call rates...and the inevitable reliability and call quality issues from the network / service provider side then impact these business directly. Cheap will also mean offshore or non existent support

In maintaining ISDN with its inherent reliability and quality advantages, while migrating unused services and/or adding additional services via VoIP - business telecommunications risks and overall costs can be significantly reduced without impacting on call quality or the customers experience by phone with your organisation.

While the telephone remains one of the most powerful tools in business - getting the right balance between line types, technologies and telecommunications costs is a critical aspect of managing the modern business.

Feel free to pass the above article on to Fellow small business owners and operators who you believe may be struggling with this whole VoIP thing.

If you would like to speak to a Consultant about options for your business CLICK HERE

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