Came across this on an internal blog and liked the description.

Think of good design in a system as a line of credit: just as purchasing new equipment for the business without generating income creates a debt against the credit line, adding features to a system without improving its design is “borrowing” against the capabilities of the system. There can be good reason to do this; after all, credit is used to improve cash flow and solvency. The danger is in thinking of this temporary loan as a permanent increase in funds. The debt must eventually be repaid.

Failure to reduce the debt (improve the design) in favor of making new purchases (adding new features) eventually results in a large portion of effort going toward interest payments (patches and bug-fixes), and reduced buying power (ability to add new features). Eventually, this can lead to a situation where all the effort is going toward interest payments (struggling to keep the system alive), and only trivial features can be added without major rework.

http://www.agilejournal.com/content/view/773/111

So last Thursday evening it was decided that I should go and collect my LadyFriend from her place of employment and transport her to my place of residence as she was not feeling well and did not need to endure the perils of public transport. The route home involves crossing the East Link bridge so I topped up my e-tag at about six thirty and headed off knowing that my vendor claims it takes up to 90 minutes to process the top up but Dublin traffic meant it would be two hours before I hit the toll bridge.

So two hours later I drive up to the toll barrier and get a lovely “account suspended” error. I had driven up to a barrier with a cash option as I feared that the 90 minute update interval was wishful thinking so I threw some cash in the basket and drove home. The next morning the LadyFriend was very much not well so after awhile I drove her back to work. At this point it was nearly midday so I was confident my top up would have been processed by then.

This was pure folly. “account suspended” flashed on the display once more. I had in a moment of misplaced faith in the NRA and NTR driven up to a barrier with no cash option and so caused some traffic delays while waiting for the Lady to come out and take my money. During this transaction a brief discussion ensued as to the length of time it takes an account update to be process. Two days is what she tells me. I am shocked. This is the kind of nonsense I expect from the banks but not from a modern system only put in place in 2007.

My gut reaction was that if someone was to propose a system design to me to implement that took more than 2 seconds to propogate updates from a tag vendor to a toll operator then something was seriously flawed with the design. I can only presume that the National Roads Authority and the various toll operators use carrier pigeons to implement their system.

After about a day of being this cocky about how I or any of the people I work with could do this much better I began to wonder how I would build it and so just to prove to myself that yes this could be done I have written up my design and included it below as it may prove of use to someone.

Only read beyond this point should you actually be interested in how I would build this system and actually think things like message queuing and distributed systems are fun.
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I was having lots of problems last night and this morning with multicast not working correctly on a linux host. As soon as I started tcpdump multicast would work. It is not fun trying to troubleshoot a problem that goes away everytime you try to debug it.

Turns out the realtek r8169 driver doesn’t handle multicast on the newer cards correctly.
Downloading the r8168 driver from Realtek and installing it resolved the issue.

This post is being made so that google will be able to help the next person with this problem.

So while attempting to copy all my photos from the Trans Canadian train journey onto my laptop it started whining about low disk space. It seems I have managed to produce somewhere in the region of 25GB of photos so far and there is another week to go. My short term plan is just to buy some blank dvds in Portland but how do people store all their photos.

After sitting through Eoin O’Dell (photo below) talking about the legal challenges facing bloggers I am tempted never to post anything on the internet ever again. Barcamp was good fun and I was sorry to have to leave early and miss some of the later talks that I was interested in. Hopefully those who came to my talk got something useful from it.

So yesterday I gave the first airing of a talk I have wanted to give for a while called The Realities of LLU in Ireland at UKNOF7. The Title is a bit silly but such is life.
I am planning to give this talk or a version of it at BarCamp Dublin in a few weeks but I have some doubts over how suitable it is for the event.

The talk covers a number of areas including brief history of irish telecoms that impacts on LLU, How an operator goes about unbundling an exchange, how do we unbundle customers to deliver services and finally what are the coming changes that will impact on LLU. The slides form a lose structure in which I talked about the nature of the ISP market in Ireland and anything else that seemed related.

John having recently joined the UKNOF Programme Committee ment that Colm from Joost and Donal from HEAnet were also giving talks which were really informative and in the case of Donal’s talk on NOC tools it gave me some interesting ideas for tools to use within Magnet.

Got my beta account today and despite Colm’s claims of how it isn’t ready etc I am very very impressed by what has been achieved in so short a time.

This may pose a significant challenge to my plans for the Colin Appreciation Channel.

Apologies that this is work related but it needs to be somewhere google can find it.
Every so often I see someone complaining on one forum or another *cough* boards.ie *cough* complaining that we do not let customers configure the firewall on their modems. There is a reason for this.

The reason we don’t let customer configure their modems firewall is that it doesn’t do anything. Our modems are not acting as NAT routers / PPPoE Clients. They are basicly switches. This means no layer 3 handling, no need to map ports. So any config a user might apply would be ignored. Also should a user put the modem into routed mode a TV stream or two and it will melt. DSL modems are not exactly high powered. The other reason we do not let users fiddle with the modem is because we have QOS settings to protect both the TV and Voice traffic.

So how does it work: You plug in your PC and it requests an IP address via DHCP. The DLSAM and the provisioning system have a quick conversation and then assign your PC an IP address. A unique Public IP address which supports any application. The only filtering we do on a customers port is some basic stuff to prevent common viruses and spam bots.

If you then plug in another PC, your friends laptop when they are visiting, that new xbox you got for your birthday they will just be assigned an IP address of their own. Magnet’s FTTH and LLU networks have been certified as suitable for use with xbox live. 95% of the tests didn’t apply to our networks because we don’t do things like NAT.

The reason we do not let users configure the firewall is that it has no function.
Anyway here ends the Rant.

So last week the DCMNR annouced a Pilot Digital Terrestrial Television service from Three Rock and Clermont Carn in Co Louth and according to media reports there will be approx 1000 Set Top Boxes given to test users during this two year pilot.

This is the kind of thing that gets me somewhat agitated about this country. The time for pilot schemes is past. Freeview is the deployed DTT solution across the UK. We should just deploy it here. The reasons are many but the most important are:

• Time to Market

  A two year pilot will run until 2008 and only then will we start trying to deploy a nationwide transmission infrastructure. Given the usual delays for procurment etc it will be 2010 before this gets anywhere. With a proposed switchoff date of 2012 for analogue services this is leaving things a little tight.

  Oh and the public don’t get the benifits of Digital TV until this is done.

• Intergration

  Most of the main channels besides RTE have already intergrated their interactive services with the freeview system. RTE would be able to utilise the BBCs experience in deploying interactive services on the freeview system.

• Consumer Cost

  There is a vibrant market for freeview set top boxes in the UK which has driven the cost of these units down to approx €50. Why pick a different platform where the benifits of volume are lost.

As someone who was involved in the early DTT work in RTE back in 1999 it is somewhat disapointing that it will have taken 10 years or more to deploy services to the public and this delay is due to the various ministers who always manage to messup even the simple things.

So I was testing our new EPG (Electronic Programme Guide, the menu system on the Set Top Box) at home and one of the nice features is you can view the channel listings with the channels sorted by popularity the data for which is gathered in real time. This is a really cute feature which shows the potential which an IP based system can deliver compared to traditional systems.

There is one downside. You get to discover that the most popular channel is showing Celebrity Big Brother. I despair for the general population, well at least 17% of them. I think I should insert lots of dummy viewers to skew the stats in favour of programmes that I know are good and therefore encourage people to watch better TV.