UK ENUM Conference

So I attended a conference today held in London to learn about and develop commercial ideas concerning ENUM.

ENUM allows businesses and individuals to publish their telephone number (fixed or mobile) within DNS records so that VoIP clients and providers may look them up and provide a more direct connection to number owners.

The initial goal is reasonably simple, and has to be to gain traction. Imagine the NHS has 500 telephone numbers that it operates as 0800 freephone numbers to allow customer (patients) to contact various local departments. The cost of each minute of every call is borne by the NHS so ultimately by the British taxpayer. Now the NHS also has VoIP connectivity and decides to advertise their 0800 numbers through DNS using ENUM. Subsequently, every time someone using VoIP decides to call any of those 0800 numbers their VoIP provider will find the 0800 number in the ENUM DNS listings for the NHS and will connect the caller to the medical department using VoIP alone – at no cost to either party (usually).

Clearly with this approach there is scope for financial savings. That said, there remains considerable work needed to achieve even this small goal, let alone the potential options further down the road.

In case you were wondering, ENUM is an international standard being implemented by individual countries separately through their respective Governments. The UK Government, through regulator OFCOM, has assigned the design, implementation and ongoing administration of the project to UKEC who, in turn, have contracted much of the work to Nominet. Nominet administer and maintain the .uk gTLD – when you buy any domain ending .uk it is ultimately sold by Nominet although almost always through a reseller (“registrar”) like GoDaddy.

So we now have a basic goal with example and a non-profit company to drive it forward. Part of the reason Nominet were awarded the contract was their intentions to market the ENUM provisioning as a resellable product. And here’s where the majority of blank faces emerged. The audience consisted of any parties interested in becoming ENUM registrars, effectively reselling the service of adding your telephone number to the DNS system. To be more accurate, the audience actually consisted mainly of people in the telecoms and ISP industry wanting to know what ENUM was and whether there was any commercial potential for them or whether it might actually screw them out of their revenue.

The message from Nominet was very clear on one matter. The end is in sight for minute revenues. This means your current fixed line telephony bill of 10p per minute connected to someone with a different geographic area code will be reduced to nothing. Your mobile network tariffs will no longer give you minutes in your bundle as calls to your mates will be free. Don’t ask for a timescale on this although the impatient amongst you could always hook up with VoIP today and extend your reach to your mobile phone provided you can install a VoIP client and connect via WiFi.

To be honest, the Marketing Director of Nominet introduced the commercialisation of ENUM as a set of current ideas rather than anything more concrete. He was, literally, waiting for suggestions from the audience. The common thread that was registration of the number would likely end up free, with registrars making their profits from value-added services. It was suggested one way would be to operator publicly accessible directories of businesses with their advertising online and a simple click to call mechanic.

There are two current matters in my mind that restrict uptake and promotion by business (registrars).

  1. You can list more than just a VoIP endpoint with your telephone number, but what else is currently undefined and may be regulated for privacy reasons. This does have potential for more far reaching consequences
  2. You still cannot obtain a telephone number for life, or extend it. The number you can register have to come from a Communications Provider (CP) like BT. If you move providers can cannot take your number, you’ll have to register your replacement number instead. And because the ENUM system converts a number into DNS (02071234567 becomes – the software will do this for you!) you should be able to extend this yourself by addition additional digits and sending these through to your local phone system just like an automatically dialed extension.
  3. Each registration must go through a verification agency to ensure the registrant really does own the telephone number being registered there will be an additional cost (read: Higher bar to entry).
No doubt business models will emerge from this but for now ENUM remains in the cot after birth, ready for the world to sit up and really take notice and exploit its full potential.

Asterisk and Amazon EC2

Given the clear advantages of cloud computing and the industry momentum (slowly) toward VoIP and complementary technologies (think XMPP) I thought it might prove an interesting exercise to install Asterisk on an Amazon EC2 instance.

My preferred operating system is Debian GNU/Linux. Instances are available with Debian (various versions) pre-installed. Theoretically it should be only a few steps to get Asterisk running.

Here’s where reality kick in. Hard. Asterisk has certain features like conferencing that are attractive and in some cases necessary to have. These features require accurate timing as normally provided by hardware except in this case where we actually have a virtual hardware machine with no telephony equipment connected. To provide a timing substitute Zaptel provide the ztdummy kernel driver.

Which means compiling Zaptel against your currently installed Linux kernel. This cannot be done under Debian. The version of the compiler (gcc) is different to that which compiled the kernel. To compile with the correct, older, gcc, you’ll need to boot the OS Amazon used to compile the kernel.

Over to Fedora Core 4 we head. Now, I managed to compile, install and actually run ztdummy on the Amazon developer image, however by this time I’d really had enough. Suffice it to say I was in no mood to start transferring kernel module files across to my Debian instance to pursue the matter.

There are a couple of people who have written up instructions on getting Asterisk to work on EC2. Neither I believe install the ztdummy kernel module. So they are essentially crippled one way or another.

Amazon: If you are listening, let us sysadmins do what we do best. Let us build our O/S including our own Linux kernel! So much time has been wasted due to this restriction!

Amazon Cloud Computing Alternatives

So there have been plenty of web sites and services affected by today’s big Amazon S3 outage. Smugmug, Twitter, and JungleDisk amongst the casualties to various degrees. Developers have been venting their frustration at seeing their applications fail because of something they relied on.

So what are the alternatives?

Any CTO will tell you that moving parts are your IT department’s weakest link in reliability terms. If you build a company on a single server will you have more, or less, moving parts that building it on a large computing farm as Amazon provides? Such an absolute measurement is of course a waste of time as that one server of course could die at any moment making you wish you’d relied on the cloud. Yet the cloud may also experience downtime.

Amazon does however have the advantage that it hides it’s redundancy from you. If you were to try to match it, you’d likely end up with RAID, and hot standard servers. Trust me, you don’t want to rely on that scenario without spending time and money testing your backup solutions.

So cloud computing might have occasional outages but at least there are engineers on hand 24×7 to fix them on your behalf. All part of the service, Sir. With your own equipment, you are on-call 24×7 shared with your colleagues. Assuming you have some.

Ultimately money can only buy you the best commercially available solutions. Amazon are not the only cloud computing service providers but as they happen to have financial muscle and experience on their side I would go so far as to say they will likely be the best overall. You mileage may vary, naturally.

Remember, Amazon use commodity hardware under the assuming that bits of their network will fail at random. They have constructed software to operate on top of this in a distributed manner to detect failures and try (as best as their programmers can code) mitigate against issues as they arise. I am sure that once analysed the software will be updated to minimise disruption caused by today’s failure as well as similar ones.

But seriously, even Amazon can only go so far. The human brain can only think up so many scenarios and code so many mitigation rules on. Oh, and testing all these situations can also be a real challenge.

It is still a damned site better than relying on your own company to build a similar system in-house.

Amazon Amateurs?

According to iehiapk: “I was under the apparently false impression that S3 was a high-availability service.  We may have to evaluate other services now.  This makes us look like a bunch of amateurs.”

I would like to ask precisely what he defines as a “high-availability service”. Five-nines? Sorry, the Amazon S3 SLA says three nines only. If they are in breach of that (which I suspect they might be now although I’ve yet to calculate or read the fine print) your recourse is a partial refund.

Either way, when you sign the service agreement you accept there will be some risk to service and where conditions are met the supplier will compensate you, all documented and accepted when you signed on.

Amazon S3 Outage (Now Back)

Well I returned to check my giant photos upload that JungleDisk was sending to my Amazon S3 account and it had stopped.

The log showed a whole pile of HTTP error codes which any self-respecting technophile will realise means a serious fault is occurring. The S3 forums document the first errors from 0858PDT although JungleDisk for me reported errors from 1642BST.

There are a few big customers impacted like the photo sharing web site SmugMug who’s displaying an outage page right now and also blogging about the incident. The Amazon Status page does at least confirm what we already know – they’re down and painfully aware of it. Smugmug’s blog says it’s “only” their 3rd outage in over two years which is to be expected. Other major brands will include several Facebook apps loading slowly or displaying errors.

Still, this will hit mainstream press and give cloud computing negative publicity. Hopefully Amazon will learn from this early experiences and continue on the road to virtually bullet-proof hosting. Not many organisations are large enough to put in the resources necessary to build such a robust service and put their brand name against it.

Incidentally, if you have an S3 account, please check their SLA for the procedure to obtain a partial refund…

Updated 2225BST: has broken images due to this, as does Twitter. Amazon report progress toward full restoration of service with internal network communications slowly coming to life.

Updated 2249BST: Amazon are bringing up their S3 web interfaces. Sites and services (like my Jungle Disk backup) should be back up soon. I look forward to their statement on what happened and how they will prevent recurrence.

Updated 2226BST: Amazon S3 EU is back… S3 USA taking a little longer due to larger size.

Updated 0017BST: It’s now Monday and Amazon S3 USA is online once more. Big, big outage.

Terraços Do Vau

It’s now nearly one month since we visited Portugal and I thought high time I ought to write my notes on it. Photographs will follow once I’ve whittled the several hundred down to a more manageable number.

terracos du vau 1

I’ll start with our hotel which is located about 0.5km inland from the beach. You you need to walk up a short road which has hardly any traffic on it and no markings to reach the main building. At the front it is the bar which in turn overlooks the patio and small pool area. Reception is just inside the doors and manned by very friendly staff with excellent English.

At this point, a quick tip: Give yourself five minutes to read the small folder to the side of reception. Useful native phrases for communication with your apartment maid held within alongside various other snippets of essential information.


The lock on our door needed encouragement to open, but once inside we were impressed by the three-star standards. A small lounge with a TV (remote did not work) and four native channels. A double bed (as requested) which wasn’t brilliant but certainly not to be complained about plus bedroom air conditioning. The kitchen had all the essentials plus washing machine, fridge freezer and even a dish washer. A gas powered oven with hobs and fume extractor is also included. Overall it was very, very clean, airy and pleasant.


There are some caveats.

You need the electronic key fob inserted to power your lights and washing machine. This saves on power included in your bill. This also means that to wash your clothes you need to be in your apartment at all times which can take a while to finish.

Lastly the kettle. It is not electric so you must boil it on a gas hob. Do not expect anything less than five minutes before it begins to whistle.


The apartment has a balcony although we only got the sunlight directly after 1900 hours. Even so, towels dried with each after only one hour. A linen horse was also supplied albeit slightly rusty and again our clothes had no trouble drying in the evening / overnight. The Portugese sun even after 1900 is pretty warm! The maids will replace your towels every few days so don’t worry too much about hygiene.

The pool was tried only once but it was clean and refreshing. Some pool toys (inflatable beds) were seen although we did not know if they were supplied or privately owned. The facilities are not large enough for things like diving boards. There are limited plastic sun beds to be found poolside.

The bar deserves a good review. The staff are very friendly and again have excellent English. Food and drink are available and hours are very flexible provided there are sufficient people to make it worthwhile. Apparently they’ll cook you a pizza at 0200 if there are people around to spend the money.

The hotel is exclusive to the Thompson group. As a result you will only likely be joined by other British tourists. Many are young families. This did not present any problems for us but we did like to go out each day. Depending on the day you arrive you’ll receive a welcome talk from (in our case Tony) the senior representative giving tips and recommending the local excursions. The talk is well worth it, although we ended up spending a small fortune on the excursions ourselves!

There were few noise problems overnight. But beware the area is prone to wild dogs between dusk and dawn (the coolest hours). One night we heard dogs barking in the early hours. Five minutes by foot down the road you’ll find two supermarkets. Well what the Portugese call supermarkets will British call corner shops. The smallest of the two is immediately to your right over the road. The larger is one minute further to your right.

Incidentally at the crossroads is where you are picked up for excursions. Beware if you pick the boat trip – you might be packed in the back of a old Land Rover which requires a suspension overhaul.

Jungle Disk Monitor

Decided to check out Amazon S3 and it’s practical uses first. This is Jungle Disk.

Jungle Disk is like traditional software in that it is downloaded and run by your desktop computer. It gives a point-and-click interface to select which files and folders to back up and over what schedule (if any). The above screenshot was taken during an (easy-peesy) initial backup of my Documents folder in version 2.02

There are a number of tweaks too such as bandwidth limiting.

Interestingly, you can also “mount” the S3 service as a disk drive. In the above picture I can double-click the JungleDisk icon on the desktop and open my S3 storage account within Mac OS X Finder.

Jungle Disk is available for Linux, too. Which means it will handle a mounted connection to S3 for your servers. Think of the possibilities…

New arrival

I have recently been looking into architecture of web applications. It follows some interest in Amazon’s EC2 and S3 products where you rent data center resources.

And as if Amazon read my mind, my pre-order of Baron Schwartz’s (et. al) High Performance MySQL (2nd Ed) arrived yesterday (Saturday). It’s certainly a thick book covering all sorts of topics. Hopefully I’ll get a chance to actually read it over the coming days…