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What vexes VoIP users?
It's only an issue if you have a single gateway which is serving up multiple public addresses.
SIP is not the only traversal that breaks in this environment, but, it does choose to break in some
of the most interesting (especially to troubleshoot when you don't know that's what is causing
the problem) ways.
This was not the result of "smart nat" or ALG issues.
I will say that I have not seen a lot of environments that have a single gateway that maps clients
to a variety of external addresses and that may account for the number of colleagues that haven't
seen this issue before.
It is real. It does exist. It is all kinds of fun (not!) to troubleshoot the first time you encounter it.
(The SIP gets through the traversal just fine, but, usually one half (and not consistently the same
half) of the RTP streams don't.)
On Feb 28, 2011, at 1:00 PM, Jared Mauch wrote:
> I've found that sip alg on devices is badly broken and must be disabled. This is true of ios and various consumer electronics devices. Nat traversal for multiple devices is not an issue in any case I have seen.
> Turning off "smart nat" usually solves it.
> Jared Mauch
> On Feb 28, 2011, at 2:34 PM, Bret Palsson <bret at getjive.com> wrote:
>> Sorry I didn't include this in the last email...
>> We have large clients who have phones registered on multiples of public IPs from the same location. Works no problem. We do some trickery on our side to make that happen, but I thought all VoIP companies would do that.
>> On Feb 28, 2011, at 12:25 PM, Owen DeLong wrote:
>>> Another vexation for VOIP in the SMB environment is that it rarely works particularly
>>> well (if at all) in light of a multiple-external-address NAT pool.
>>> You simply have to map all of your VOIP phones in such a way that they consistently
>>> get the same external IP every time or shit breaks badly.
>>> On Feb 28, 2011, at 11:11 AM, Bret Palsson wrote:
>>>> Since our company is a VoIP company, I will chime in to this topic.
>>>> Let's start off with the definitions so everyone is on the same page:
>>>> vex |veks|
>>>> verb [ trans. ]
>>>> make (someone) feel annoyed, frustrated, or worried, esp. with trivial matters : the memory of the conversation still vexed him | [as adj. ] ( vexing)the most vexing questions for policymakers.]
>>>> Alright, now that that's out of the way...
>>>> I am only referring to small medium business and some enterprise (Those are all our customers, we do not do residential)
>>>> - Seemingly complex.
>>>> - Worried about the "What if the internet goes down" scenario.
>>>> - Call quality.
>>>> - Price
>>>> - Location
>>>> - Outages
>>>> - Seemingly complex... Very true. Most VoIP companies, both hosted and on premises are difficult/time consuming to setup and make work they way you want it.
>>>> - What if the internet goes down. This one is a challenge. POTS actually have issues too, but when analog phone service goes down, there is no light on the phone indicating that the phones are not working so many customers perceive there is a problem. With the FCC mandating all POTS move to a VoIP backend (which for long hauls, is mostly already true) POTS will experience the same downtime as the internet.
>>>> However as we all know, the internet is built to tolerate outages.
>>>> For most people they don't understand how the internet actually works.
>>>> - Call quality... If a VoIP company pays for good bandwidth and maintains good relationships with peers, the only concern is the last-mile(From the CO to location). Now there is much more that plays in quality, ie. codec selection, voice buffer, locality to the pbx.
>>>> - Price... Believe it or not people are worried about paying less for better service. Who would have thought?
>>>> - Location... Location is super important both in the last mile and PBX.
>>>> - Last mile:
>>>> In older locations the copper in the ground is aged, if you can't get fiber and your stuck using T1, lines, then hopefully you are in a location that keeps the copper in the ground properly maintained. If you are in older locations, which one of our offices are, there are remedies, you can contact your bandwidth provider and have them do a head to head test using a BERD (bit error rate detector) and they can find the problem. But that's a whole other topic.
>>>> Some people believe that on premise is the best location for a PBX, this may or may not be true. I happen to believe that keeping it off premise is the way to go. You get up-time, redundancy, locality, and mobility. You just plug in your phone and your phone is up and running. Move offices.. got bandwidth? Your good to go. No equipment to worry about, say a power outage happens, your voicemail still works people call in and are in call queues and have no clue you are down. Feels more like POTS with an enterprise backend.
>>>> -Outages: If the internet does fail, most providers offer WAN survivability. The customer plugs in phone lines into the router and if the internet goes down, they can make emergency calls or calls to the world limited by the number of lines the router can accept and are plugged in of course. Now in all our experience going on 7 years now, 90% of the time WAN outages happen, guess what also dies, the POTS! Who would have thought that when cables get cut, that the phone lines were also part of the cables?
>>>> There you go, some common worries, with some answers to hopefully sooth the vexed VoIP user.
>>>> Bret Palsson
>>>> Sr. Network & Systems Administrator
>>>> On Feb 28, 2011, at 11:37 AM, Valdis.Kletnieks at vt.edu wrote:
>>>>> On Mon, 28 Feb 2011 13:29:08 EST, Bret Clark said:
>>>>>> On 02/28/2011 01:17 PM, Leigh Porter wrote:
>>>>>>> VoIP at the last mile is just too niche at the moment. It's for people on this list, not my mother.
>>>>>> Baloney...if that was the case, then all these ILEC's wouldn't be
>>>>>> whining about POT's lines decreasing exponentially year over year!
>>>>> I do believe that the ILEC's are mostly losing POTS lines to cell phones, not
>>>>> to VoIP. I myself have a cell phone but no POTS service at my home address. On
>>>>> the other hand, I *am* seeing a metric ton of Vonage and Magic Jack ads on TV
>>>>> these days - if VoIP is "too niche", how are those two making any money?