Networking

Is your network ready for VoIP?

Switching to VoIP telephony systems is gaining momentum with consumers and businesses alike. If you are planning to make the leap, make sure your network is ready.

We may tolerate a web page loading slowly, but get irritated when the quality of an Internet telephony conversation is less than pristine. With that in mind, I would like to share a "network admin" experience with you.

A friend of mine uses Skype, a form of Voice over Internet Protocol (VoIP) telephony to talk to her daughter in France. It saves lots of money and the video option is nice. For several months now, everything has been working famously.

Every once in a while they could not understand each other during their Skype call. But, they could chat using the messaging option. So, they would suggest switching to their mobile phones. Doing so upped the cost per call significantly.

What changed

My friend finally called, explaining the problem and how it was sporadic in nature. One time everything was fine. The next, it was impossible to understand each other. They were living with it, but the outages were increasing in frequency. That's not something a concerned mother wants to deal with.

Luckily, I was somewhat prepared for this. Another friend of mine just passed the CCNA Voice. After my heart-felt congratulations, I put him to work, asking about the intermittent Skype problem. His first question: What changed? I felt somewhat smug. That was my first question as well. Trouble is he got the same answer I did: Don't know.

Test the network connection

Based on the random occurrences, he suggested testing both ends of the connection when Skype is working correctly and when it's not. Before I could ask how, he mentioned there are websites that measure network connections for VoIP quality.

Visualware is one such website. It is unique in that their online networking tests do not need to install an associated application on computers being tested. Just connect to one of their servers located around the world:

In my friend's case, she picked Paris and her daughter selected their home town in the United States.

Results

I was not able to get actual test results from my friend. Yet, I wanted to show the wealth of information obtained from the test. Below are test results when I connected to a server in Paris:

Notice the test requires choosing a codec. We used the G.729 codec. It and SILK are the codecs used by Skype.

In my case, jitter and packet loss were acceptable, but that was not the case with the daughter's test results. Both were down in the red zone when the Skype connection was unusable. The next slide depicts the results in graph form, showing jitter and packet loss information for individual packets:

It's somewhat subjective, but the Mean Opinion Score (MOS) is the best way to have a remote user convey their test results. The score range extends from 5 (perfect) to 1 (impossible to communicate). The following slide displays the test connection summary and my MOS score of 4.1:

The daughter's MOS score slid below 1.5 when the conversation was not understandable.

Now what?

The randomness had me puzzled. With mom's permission, I fired off an email to the daughter with some questions. I asked about existing bandwidth, how many were using the same Internet connection, and what it was being used for.

It turns out the apartment is part of a multi-dwelling building. An internal Ethernet network funnels all traffic to the Internet. The biggest clue was several people in her apartment complex play the same Internet game, usually at the same time to compete against each other. Guess when she was having trouble talking to her mother on Skype?

I felt it best to mention that this kind of testing cannot duplicate the exact route VoIP packets take between the two connection points. Meaning there is a chance that the problem may be missed. That said, the tests provided by Visualware are a good starting point due to their simplicity to use.

Final thoughts

If you are considering installing a VoIP telephony system, or are having problems with an existing install, the first step is to check out network performance with tests like those provided by Visualware. I also recommend reading this white paper. It explains the importance of testing for connection quality as well as connection bandwidth.

To get an idea how pervasive VoIP telephony will become, check out this link. It explains how Cisco upgraded an orbiting satellite and made the first VoIP call without the help of any terrestrial infrastructure.

About

Information is my field...Writing is my passion...Coupling the two is my mission.

58 comments
christopher_d_roberts
christopher_d_roberts

If ever there was a case of stating the bleeding obvious, this has to be it. ANY shared network can at times exhibit similar issues but the fact is that for the vast majority of home and small business users, Skype is an ideal solution. Thanks for boring me Mr Kassner, normally in these forums I expect to learn something but there isn't much I can learn from you. Chris Roberts

sma_mark
sma_mark

Does anyone know of a testing tool that will provide results over a period of time? Something that you can start and let run for 24 hours, or so, that will provide bandwidth results at specified time intervals within the test period? It seems this would be useful for individuals, or more importantly, organizations that want to test their connectivity 'prior' to making the VOIP investment. Mark

mark
mark

One thing to think about when using those tools that you linked is that 99% of the time the problem it is identifying is on your LAN network. As you stated in this case the problem was not with France's ISP, but rather with her local building's over use of their internet connection. 99% of VOIP problems are caused by network over-utilization at a local level. When you get bad test results do not be quick to point the finger at any ISP, rather check your own network and realize that you are only paying for a specific amount of width. In most situations, if you are in excess of 60% of your maximum capacity VOIP calls will have problems.

josh8888
josh8888

There is no question that setting up a wifi phone on a basic network has never been easier. We use the WP100 from YIPPZ.com in our offices in the US and Europe. You can't beat being able to call one extension to the other at absolutely no cost and with crystal-clear audio.

Michael Kassner
Michael Kassner

VoIP apps like Skype need sufficient bandwidth. If you are having problems or considering a VoIP system, make sure to check out the network. Here are a few tips on how to do that.

rickscr
rickscr

Personally I found the article rather informative as I am sure many others will. Thank you Mr. Kassner.

Oz_Media
Oz_Media

Even when bored and disinterested with a topic, you'll still take the time to read through and reply to it, whether usefully or not.

Michael Kassner
Michael Kassner

As a consultant, is it not true? Facts and situations that are obvious to you are not such for others.

Jellimonsta
Jellimonsta

One thing you could learn... Maybe a touch of humility? I believe one day, that lesson will come.

Jzoltowsky
Jzoltowsky

We have been using Solarwinds for a few years to monitor our Frame Relay lines...Yes I said Frame Relay !! You can even see what application and protocols that are being used and how much bandwidth they use at any time of day. PS..we are migrading the frame lines with dark fiber..unlimited bandwidth and QOS control.

Michael Kassner
Michael Kassner

The internal network was 100 Mb/sec. The Internet connection was 1.5 Mb/sec. I suspect it was that. But, as you say it is not the fault of the ISP.

Michael Kassner
Michael Kassner

Is one thing that every convert remarks about. I immediately noticed that when I first used VoIP. So much so, that when recording SME's statements for podcasts, I always try to use a VoIP app.

Harry44Callahan
Harry44Callahan

I'm surprised no one mentioned this. I've been using Google Voice for several months now and have had little trouble with. My network usually measures 20 Mb down and 3Mb up. I've had no interruptions or problems and the clarity is excellent. Although I'm sure Skype is better now I used it about a year ago and had problems with all of the above.

Router boy
Router boy

Avaya and it blows. We have a pretty robust network already in place but it does not handle to the load from Avaya very well. It's not uncommon to have calls drop or the phone system to randomlly kick you out. We moved to this system about a year ago to help with remote locations and telecommuting but it become more of headache than help.

Jellimonsta
Jellimonsta

I have never actually really used Skype (except for Skype chat twice a number of years ago). However, I vaguely remember reading Skype was able to adjust codec dependent upon available bandwidth. If the users were sure to only use voice chat, and not video, a 64K ISDN line should be enough bandwidth. There are a great deal of variables that could have been the cause for poor connection for the 2 parties mentioned.

harryolden
harryolden

I use it AT HOME and the person I call has a 45kbs modem connection using the vidio also and have no problem with it. With the previous messages I do agree what is obvious to me is not obvious to others Iam very mecanical minded and do all sort of things you name it I do it but to express my self to others there is a problem I have given answers in here and I get the feeling that I am a dick head because I have written it wrong and the person does not understand this, example when the hard disk came out my friend went to school for 3 weeks when he came to my place he saw that I was doing it also and I had never gone to school he was amazed about this I do not use the proper slang or term for this subject. Cheers Harry

Oz_Media
Oz_Media

If you can't say something nice, best to say it online. I am not excusing him in any way but it's better vented here than in front of his boss. Michael has been here long enough to know when to ignore people venting, me included, I'm sure. :) Plus, we never let people push TR staff around anyway, someone will always step in to set it straight.

stevesexton
stevesexton

We use a Cisco VoIP phone at work, 20 users on a metro-e line and continually have QoS issues. We are remotely hosted and the provider can't or won't make it work.

Michael Kassner
Michael Kassner

I almost included them, but they require installing a client if I remember correctly. Edit: Spelling

delphi9_1971
delphi9_1971

Voice calls with no compression using the G.711 codec (the best you can get on VoIP) will only use 64Kbps of bandwidth. Which incidentally is 1 Channel out of 24 on a 1.5 Meg T1 Circuit. So you're talking about 1/24th of your available bandwidth. The problem with VoIP is that certain types of data streams like FTP, File Transfers over HTTP, internet gaming and Video streaming tend to grab every last little bit of bandwidth. If you don't manage to that, you'll have problems. ISPs manage these traffic types with QoS methodologies. Also, home routers and switches usually don't have the same processing power or big enough packet buffers to handle real time large quantities of traffic. This is why your typical home router will only support 256 workstations and high end routers can support 10's of thousands. Both sets of gear can have 100 Mbps interfaces. So even though you have 100 Meg to your internal router, your router may not be able to handle full line speed. Especially when you have multiple people trying to use bandwidth intensive applications. When that happens you get Jitter (variable latency) and that causes problems with VoIP. The fact is that ISPs have to make sure you have your bandwidth. If you're always calling in because your connection is slow, that costs them money. So they have teams of network engineers to manage their network more than you would manage yours at home. Plus the High end gear to handle the load. So they build in capacity and performance to handle it and are actively monitoring their networks and correcting for issues. So the lack of proactive monitoring, slower performing consumer grade gear and a proliferation of highly bandwidth intensive applications will lead to this being more likely to be a problem at the LAN level rather than the ISP (Not that it can't be them, it's just not often them)

Michael Kassner
Michael Kassner

Is most likely the reason. Google Voice is on an equal footing with Skype, IMO. Well, may be not after Skype's recent extended outage.

jhoward
jhoward

Avaya is still selling premise based systems correct? In that case your issue is almost definitely network architecture or congestion. You really only have a few main components to look at here: 1. How does your PBX talk to the PSTN? * PRI(s) - this would be akin to a TDM PBX and most likely isn't an issue * SIP carrier - While cost effective too many people think their Cable/DSL or DIA circuit has plenty of bandwidth to cover this. While bandwidth is a small factor you can only control QoS over a point2point connection with your vendor and they will happily tell you the same when they refuse to help you troubleshoot call quality issues. 2. How do branch offices connect back to the PBX? * T1/DS3 - great, you control the QoS. Is it tagging packets correctly? * Cable/DSL (other) - most likely you cannot control QoS and any network congestion in the cloud between branches will cause issues. 3. Is your phone system on it's own VLAN? * Yes - Excellent! * No - most likely your voice is competing with data for scheduling on your switches. The main concern here as you can see is not bandwidth but QoS. This cannot be said enough - QoS is the key to good VoIP quality. This almost always falls on the choices the consumer makes to save money by using unmanaged switches and/or DIA circuits instead of point2point circuits.

Oz_Media
Oz_Media

When VoIP was first becoming popular, I was heavily involved in designing PBX based systems (from top end telecom companies)in businesses around the province. We had several discussions here where IT folk were all over 3-Com and Avaya systems, which I scoff at knowing their limitations as network focused systems. Companies like Nortel, NEC/Nistuko were offerig VERY expensive PBX's and were running up against cheap, low end VoIP 'wannabes'. They were not business telecom providers but network companies jumping on the business telecom bandwagon with little experience in the field at all. Many people here, most with very little knowledge of the market or the demands of business telecom, were praising cheaper systems, which just don't cut the mustard. So it's nice to hear, several years later that people in IT are catching on that these are not business telecom systemsm they do not address needs of unified messaging, bandwidth control, QOS etc. I've found the best way to go, with a 'wannabe' is by using a managed ISP (very expensive!), not the local telco or cable provider. Redundancy, guaranteed bandwidth and quality of service makes a world of difference along with a well designed PBX and dedicated PRI ISDN line.

Michael Kassner
Michael Kassner

Also, have you spoken to Avaya about this? They normally are responsive to this type of issue. Edit: Error of tense

Michael Kassner
Michael Kassner

I did not try to downplay the possibility of other issues. In my example it was the online game that consumed a large percentage of the Internet access. I also mentioned that they did use video I am not sure about the codec being variable anymore. I did not see that in the latest version. I will for sure check again. Edit: Spelling

Oz_Media
Oz_Media

Cheap VoIP system designed by a network hardware designer and not a telecom company. No access to an ISP with managed bandwidth with a guaranteed QoS, required for low end VoIP systems. PBX manufacturers have worked around the QoS issue, for the most part anyway, a single PRI ISDN line to a decent PBX would probably resolve it, but at a higher cost of course.

Jellimonsta
Jellimonsta

I would seriously attempt allocation of a new provider. Even if you are using G.711 you should still only need about 88Kbps per leg. If you are having issues it is because your provider has not correctly classified your voice UDP traffic as EF real time.

Michael Kassner
Michael Kassner

I thought my alluding to the internal/external interface was similar to your answer. Just, not as informative. Also, adding video to the mix brings it to another level. Again, thank you for your insightful response.

santeewelding
santeewelding

From which I derive great learning and benefit. Thank you, [b]gechurch[/b], Oz, and the rest of you.

gechurch
gechurch

@Oz_media PoE isn't so you can set call forwarding. That can be done from any phone line (call your provider and get them to do it) or from anywhere with an Internet connection (log in to your account and make the change yourself). PoE is for short-term power outages.

jhoward
jhoward

Natural disasters are generally area affecting and cause long term outages. POTS does not have the ability to just work the same independent of location that VoIP does without manual and timely (and potentially costly) intervention. Also as I believe I mentioned previously I am referring mostly to a hosted solution as buying a PBX these days - VoIP or otherwise - just does not make sense for just this reason. Outages WILL happen - it is not a question of "if". All I am saying is that NON premise based VoIP has the ability to be more robust than POTS. As I said - I see this every day when buildings get flooded, the gas company cuts a power line or the building catches fire etc. Your experiences may vary however this is what I see managing hundreds of sites across the nation.

Oz_Media
Oz_Media

Just so you can forward calls, if SOMEONE is able to reach the server via IP and set it to forward calls off premise the way POTS based PBX's have done for years? I guarantee that in case of a major earthquake or flood, my phone line can still work and already receives of premise calls, which I can forward or manage with the same 4 digit extension numbers to any other off premise number on the system. It's no great IT breakthrough, it's been done for years. It's just that FINALLY the IT appliance manufacturers have caught on that their VoIP products need to work like a POTS system that business are used to and depend on. Other premised based VoIP manufacturers, with business telecom experience, have had such features for 10 years already. That's why it is so easy to sell a good PBX to a client who hates their Avaya or 3-Com system.

Oz_Media
Oz_Media

People in North America keep POTS lines because they are more stable in teh event of emergency. I've worked for the enterprise divisions of several telcos also, designing fail safe systems for global business. Even the ISP's will agree that POTs will outlast their service in such cases.

Oz_Media
Oz_Media

I have a good friend hwo runs a redundant, managed ISP in BC, operating with data centers globally. He is the first to tell you that POTS is more reliable for business in the event of a natural disaster, or at least as a back up or hybrid service. A good enterprise VoIP system is premise based, that premise based equipment is more prone to failure in time of a natural disaster than a POTS service. Re: not getting to the office. if a natural disaster takes out the VoIP PBX, the phone sin teh office still work. The office phones are also set to forward incoming calls off premise, to my cell, the receptionists home phone or cell etc. anywhere in the world I may be. I can be in the UK and get calls transferred from other people working out of the office (at home, on their cell etc), by the same four digit extension number I'd use in the office, just as when I am in the office. That's the difference between buying a phone system from a provider with over 100 years business telecom experience and an IT appliance builder. So while the VoIP is inoperative, the POTS lines at teh office still function and forward calls as needed.

Oz_Media
Oz_Media

"I was of the mind that PSTN trumps VoIP in those cases, as power outages are usually involved. " It does, that's the key reason that 99.999% of businesses chose it as a backup to VoIP or why hybrid systems are far more logical until ISP's become reliable.

Michael Kassner
Michael Kassner

What is the difference? Any traffic from a redundant site will not get there. I would place my faith on PSTN staying up over any data infrastructure and have seen it real time many times here in MN.

Jellimonsta
Jellimonsta

I agree a POTS line is a great backup for little expense. However, if there is an area disaster, the whole site is out, so whether a phone can work without power is moot. In that case, a fully redundant data center design with call centers and VoIP system backup working at a warm/ hot site trumps any stability of copper lines. If you can't get into the office, working phones don't benefit you. ;)

gechurch
gechurch

The VoIP handsets I've looked at all support PoE, and running PoE is the only way I would consider using VoIP. Get a UPS for your modem/router and PoE switch and you're laughing. As jhoward said, in the event of a prolonged power outage, you log in to your account and enter the new phone number all your phone calls should divert to. This can include mobiles, so is great in the event of disaster.

Michael Kassner
Michael Kassner

Power outages? PSTN still stays up here in the US. VoIP doesn't.

Michael Kassner
Michael Kassner

I still have an old analog phone at home for when the power goes out. The only way VoIP would work is if they used PoE. Sorry, as an amateur that works with emergency preparedness teams, we love PSTN when something hits the fan.

mbbs
mbbs

VoIp can be as good as ISDN providing you take care of the conditions needed to have good quality transmission. This means dont send it over best effort based networks like the internet, where there is no quality guarantie at all if you want perfect voice quality. You don't use a substandard quality transmission media for PSTN/ISDN lines either Also the argument of data lines having less problems than voice lines is not correct. I work for a telco and we offer better SLA's on data lines than on voice lines. We have large corporations and hospitals stopping subscriptions of their traditional voice lines in favour of VoIP. The only reason why they still keep 1 or 2 analog PSTN lines is because there is a legal obligation to have direct lines (not even connected via a PBX) for alarm systems and emergency phones for elevators.

Jellimonsta
Jellimonsta

Michael, I would assume jhoward is suggesting a fully redundant data center environment. Wherein, a natural disaster in one area negates that data center and the VoIP solution/ call center in another data center takes over. With such model, and a mobile workforce, VoIP does indeed trump a PSTN environment. :)

Michael Kassner
Michael Kassner

You mentioned after natural disasters. I was of the mind that PSTN trumps VoIP in those cases, as power outages are usually involved.

jhoward
jhoward

I should preface this by saying I am an engineer for a hosted VoIP provider so I am very familiar with the short comings of VoIP vs. POTS in terms of reliability. I will also concede that I am biased against POTS because frankly there is not one carrier I have dealt with that believes customer service is a key part of business but I digress. A hosted PBX solution where the customer utilizes redundant WAN connections and has the ability to set "out of service" call flows provides better availability and more flexibility in the event of an extended location related issue than a POTS solution. I know because I deal with this stuff after blizzards, tornadoes and floods. Businesses remain up because their office isn't necessary as part of their communications platform. POTS lines and premise based PBXs are location specific and really have no business in today's mobile user, multi-site corporate culture. I consider them lead weights on the improvement of better technologies. Now, that isn't to say that at the provider level we do not use POTS lines (PRIs) as we absolutely do and frankly carrier VoIP isn't where it needs to be yet especially in terms of faxing (FoIP).

Oz_Media
Oz_Media

POTS is stable and has been around a century. This is exactly why any VoIP connection requires a POTS system too, which is mainly found in hybrid PBX's. True VoIP will be okay for the home, unless it's on fire, but not for a business. Some form of hybrid is almost imperative for such cases. While networking is still new in comparison, I'm sure it will be many decades yet (probably not in my lifetime), before they will meet or exceed the reliability of POTS.

Oz_Media
Oz_Media

I wouldn't set up even a high end, enterprise level PBX without some form of POTS connection as even the high end VoIP is completely reliant on the ISP; ISP's no matter how sound and stable will suffer downtime before the telco's copper will. Companies I've seen covert to sole VoIP systems end up calling in a panic one day when they open the doors an have no phones. Rather than deem it simple redundancy or perhaps overkill, I see it as an imperative businss practice to ensure your business can operate.

Jellimonsta
Jellimonsta

POTS has been around long enough that it should be stable and reliable. VoIP is still relatively young. Think of it like a teenager. :p

Michael Kassner
Michael Kassner

Not here, I have helped install numerous Cisco systems in MN. All the large corporations are using VoIP. Granted the article was intended for consumer issues, but we used the same test procedures at the enterprise level.

Oz_Media
Oz_Media

Networks and data lines go down like a cheap whore. I have yet to see a business VoIP system installed without at least one dedicated POTS line for backup, generally doubling as a fax or alarm overline. Phone service from the local telco is extremely reliable, which is why i is used by alarm companies, sure they all have SOME downtime but POTS is a very solid and reliable network.

Jellimonsta
Jellimonsta

QoS is key, but you still need to do meaningful capacity planning.

mbbs
mbbs

I completely second the statement that QOS is very important. I worked in a lab of a telco, an specialised in VoIP testing. Most of the issues with bad voice quality I came across were related to bad bandwidth and QOS settings on network links, and also bad alignment of call access control between PBX and network QOS, meaning that often when people increase their max simultaneous calls in the PBX, they forget to adapt their network bandwidth or QOS settings, creating a mismatch between what the PBX sends onto the WAN and what the WAN is capable of reliably carry. What I also sometimes see is people using routers not adapted to the load they have to carry. VoIp means lots of small packets that need to be transported and prioritised. This creates a heavy load on the CPU of the router. in this case the router is the bottleneck for bad VoIP quality. I have seen numerous cases of this, and they were solved by just changing the router from a low end to one with a more powerfull CPU, without changing router brand or anything to the configuration or bandwidth/QOS network settings.

Oz_Media
Oz_Media

I don't know how many business I've been called to to resolve such issues where they feel their shared ADSL or Cable connection is more than enough fo rtheir email, internet and VoIP networks. Pin up a PRI line from a managed service to a DECENT VoIP PBX and you are good to go. EDIT: Yes, Avaya (commonly the Aura system for mid to large sized businesses) is a premise based system but, in Avaya's case, very poor equipment/server design compared to most others and performance is also a common issue. They simply don't build very good telephone systems or handsets. I have removed more 3-Com and Avaya systems, to be replaced with quality hybrid VoIP PBX's, than I can remember.

Oz_Media
Oz_Media

With these most common issues regarding their systems.

Jellimonsta
Jellimonsta

Unfortunately, there is no QoS on the Internet, so little Jack's WoW session is just as important to the router as Mom's phone call. We use Vonage at home, but I have 30Mb+ down and 2.5Mb up, so we don't have too many problems. :D

Editor's Picks