Saturday, 20 October 2018

Transferring Data

Well, here we are continuing with our discussion on transferring data. I guess it's important because a major part of the computer system is how data is transfered from one component to another, or from one machine to another. However, before we continue, here is a bit of revision courtesy of Techquickie:

Anyway, we are going to be looking at machine to machine transfers here, which in many cases operate in a way that is similar to transfers within the machine. So, the first things we need to take into account are the types of data transfers - simplex, half-duplex, and full duplex.

Simplex: well, this is basically one way communication, much like a television. Basically the television station streams information directly to your TV set (or not quite, but you know what I mean), but your TV set, usually, doesn't send anything back. Oh, and this isn't one of those Netflix style on demand services - the only way that you have a choice is simply by changing channel.

Half-Duplex: Well, I'm not entirely sure if this exists anymore. The only example I can think of are the old walkie talkies (which many of you probably have no idea what I am talking about). Basically, while communication is two way, only one person can speak at a time. It is sort of like, say, a business meeting, were you aren't actually allowed to interrupt anybody.

Full-Duplex: All I need to do is point to a telephone as an example of full-duplex communication. This is where communication is in both directions and simultaneous, which means that you can have a full on shouting match with somebody and the only way they can stop you from talking is to terminate the call.

Now, we have already started talking about this in a previous post, but before we continue, lets mention flow and error control. Now, as we all understand, not all machines are created equal - some are slow, others not so slow. Flow control basically prevents slower machines from being overwhelmed by bigger machines, and tells the sender when they should send the next packet of data. We saw this with stop and wait, where a packet is sent, and the sender then waits for an acknowledgement. Error control we have also covered, namely what to do when the receiver receives a packet that is erroneous.

Well, one method of flow control is called the sliding window method, and the diagram below should be able to explain it:

As you can see above, the window works on a method where multiple frames are sent, but only to a set amount. When a frame is sent the window shrinks, and when the acknowledgement is received, the window then expands. A similar process occurs on the other side, where when frames are received, the window shrinks, and then expands once the acknowledgements are sent. Now, it is important to note that only one acknowledgement is sent even though multiple frames are received.

So, what happens if there is an error? Well, the windows don't expand. The thing is that while the previous frames have been sent, they still sit in the buffer. The sender can send only up to the number of frames in the buffer while waiting for an acknowledgement. If it doesn't come, then that means that there has been an error. If it does come, then the previous frames are discarded, and new frames are loaded into the buffer.

Internet Protocols

First, let's touch upon what is called the Open Systems Interconnection, or OSI, model. It is one of the more commonly used systems of data transfer. Basically it defines how data is bundled and then transferred. At the bottom of the layer, they are transferred in bits, but as we move up the layers the bits are bundled into frames, and then into packets. This diagram may help, though here we are only really interested in the Data Link layer:

Anyway, we have two types of internet protocol (IP), TCP and UDP. TCP stands for Transmission Control Protocol, and is the most commonly known, and UDP, which is User Datagram Protocol. Now, the difference really comes down to speed and accuracy. TCP is slower, but much more accurate, while UDP is faster, but error prone. This is the main reason you tend to see TCP a lot more. Honestly, you really don't want to be doing bank transactions using UDP, though you might end up finding that that is the protocol that Netflix uses to stream its videos (though actually they don't, considering that High Definition television doesn't quite meet with UDP standards - it is actually used more for live streaming and gaming). The thing is that UDP really doesn't care about errors, and will keep on pumping out packets of data despite whether they have errors or not. One thing that does use UDP, is VoIP, or voice over IP, which are basically internet telephone services. Oh, and it is also used for gaming, where time is of the essence.

In the end, the best way to remember the difference is that TCP makes sure that the packets arrive the way they were sent and the order is intact, whereas UDP just keeps on pumping out packets, and doesn't particularly care either way.

Radio Days

Now, remember the days when you have a radio, or do you? Being a child of the 80s, I have fond memories of the radio, and the classic mix tapes. That was back in the days when you would listen to the radio with a cassette inside, waiting to press 'record and play' when your favourite song hit the airwaves. Anyway, there were two ways of transmitting radio signals - FM and AM. FM stands for Frequency Modulation, and AM stands for Amplitude Modulation. One thing I remember is that I started off listening on the AM band, until I discovered SAFM, and switched over to the FM band. Now that was all well and good, until we went out bush only to discover that I couldn't pick up SAFM. Interestingly, at night, my mum would turn on the radio to the AM band and listen to a Melbourne station broadcasting the football, and Melbourne was something like 700 odd kilometers away.

So, what's the different, well, once again we turn to a trusty little chart:

So, that explains everything, doesn't it. Well, not quite. Basically both methods consist of two waves, a carrier wave and the wave that the carrier wave is carrying (namely the data, or that heaps cool song that you have been waiting for ages to listen to, you know, Deep Purple's Highway Star). So, the carrier wave doesn't change, but the data does. So, notice with the AM the frequency, or the space that the waves are apart, doesn't change (or it isn't supposed to change), and the amplitude, that is the height of the waves, does. Notice also with the FM the opposite is the case, the height stays the same while the spacing changes. That pretty much explains it in a nut shell. The letters are the beginning, pretty much tell you how the data is carried.

Why do they do this. Well, it's simple. Consider sending a message. You can write it on a piece of paper, scrunch it up into a ball, and throw it, or fold it like and aeroplane. Which will go further? Well, the one folded like an aeroplane. Well, you could go one better and put the letter on an aeroplane and it would go even further (though it might not end up where you want it to end up). Basically, what the carrier wave does is that it increases the distance that the data can travel.

Now, there is a difference between the two. First of all, remember my ramblings above, about how I couldn't hear the FM in the bush, but my Mum could pick up an AM radio station from over 700kms away. Well, there is that, AM travels much further than FM, and even further at night. However, AM is actually of a lesser quality than AM. FM is always clear and smooth, until you move out of range and the quality would drop off sharply. However, AM wasn't all that good, and was even prone to interference from stations operating on a similar frequency miles away. In fact, in some places, AM radios have to, by law, shut down at night so as not to cause problems for other stations higher up the preference ladder.

Oh, and modulation, well, that is the process of mounting the data on the carrier wave, and demodulation is basically taking it off again. Oh, and AM is cheaper (you could actually buy electronics kits to build your on AM transmitter from the local hobby shop), and it has a wider range, which means that more stations can operate on it as well. Oh, and it is less affected by physical barriers.

Le Téléphone Portable

Mobile phones operate on megahertz (or Mhz) bands, and this is important to know because not all phones operate on the same bands. Basically, for a phone to work in Australia it needs to operate on one of the Australian bands. Now, I know that I don't have an issue with my phone because it worked just fine all over Europe and Southeast Asia (as well as here in Australia), however this is something we need to be aware of when shopping for a new phone.

Basically, these should be on the phone's spec sheets, and for 3G networks you will find it under UTMS or HSPDA. Actually, come to think of it, that is probably why, in Europe, my phone only ever seemed to operate on the 3G networks, despite the sales people assuring me that they supported 4G. It is just that the European 4G networks are actually on a different bandwidth than the Australian 4G network.

Oh, and for 4G networks, you need to look at FDD LTE. While I could go into details on what frequencies are used by what company, instead of wasting your time I'll simply refer you to this website

What I will show you (not that you'll be able to read it) are the frequency allocations. The Australian government basically controls what services use what frequencies. Those in Australia might remember back when television went from analog to digital, and then radio went from analog to digital. Basically what was happening was that they were freeing up space for other services to use. The same is the case with the 2G network, which has now been shut down. However, what they also do is when space is freed up, that space is then auctioned off the the highest bidder for their use.

I might come back to this later, particularly since there is a whole heap of stuff in the lecture notes about analog and digital radio transmissions that were covered in the tutes. However, let us finish off with some networking.


Honestly, there are lots of different types of topographies, but the two main ones are bus and star. The bus is basically where you have a single cable and a number of computers connected to it, while the star topography has all of the computers connected to a central hub, or switch. Now, the bus topography is cheaper, but limited by the number of computers that can be connected to it. It is also older technology, and is generally only good for older local area networks (LANs). It can also be difficult to detect faults from a single locations, and that maintenance gets trickier over time. Oh, and the more computers you connect to it, the slower it becomes, namely because you have all these computers competing for limited space. I probably shouldn't forget to mention security issues, since all of the computers receive the signal.

Now, star topography is where the computers are all connected to a central switch. Now this is somewhat more efficient than the bus topography, particularly since a failure may only affect a single computer. However, the problems arise with the fact that it relies upon a single device, and failure with the device is an overall failure of the network. The use of the central device, a hub, router, or switch, increases the cost of the network, and also the number of devices attached to the network is also dependent upon the device.

Creative Commons License


Saturday, 13 October 2018

The Lands of the Buddha

I've been to South-East Asia three times now (not counting Singapore, though I have also been there three times, it is just that the last time I was there it was for a couple of days before heading off to Europe), or I probably should be a little more specific and indicate that two of these three times I was only in Thailand. This latest time I also visited Cambodia and Malaysia, and I also spent a lot longer than I have done on previous visits (namely because I had a bit more time to explore). Now, I have already written about my experiences in an Islamic country, though that has more to do with the cats than anything else (though there is always my travel blog). So, in this post I'm going to look at the major religion of Thailand and Cambodia - Buddhism.

Actually, when I say Buddhism I should point out that there are three major strains of Buddhism: Theravada (or as I refer to it, Indian Buddhism), Mahayana (or Chinese Buddhism), and Vajrayana (or Tibetan Buddhism). The thing with Buddhism is that it isn't so much a religion, but rather a philosophy that attaches to a religion. As such, when you wander through places like Hong Kong and Macau and visit the various temples scattered about, while they are Buddhist in nature, you will also find many of the local deities present as well. In fact the various temples are generally dedicated to the various Chinese (or Tao) gods. This is similar in Thailand, except that prior to the coming of Buddhism, Thailand (and in turn Cambodia) were Hindu, and as such you will encounter many of the Hindu deities as you wander about the area.

A Bit about Respect

Before I continue I want to point out that what I am writing here is based more upon what I discovered as I visited a number of temples in the region and observed what was going on (and also various readings of Wikipedia to get a bit more clarification). When I first visited Hong Kong, and in turn South East Asia, I was a bit concerned about going into temples, namely because of the idea that not only am I entering a non-Christian place, but that there are suggestions that there are demonic entities present there as well. I do know some Christians from Hong Kong who won't enter any of the shrines there, but that has more to do with her having grown up in that culture as opposed to being a western tourist.

I have also asked various peers as to their thoughts on the subject. One particular pastor simply brushed the whole idea off suggesting that there was nothing to worry about, and that what we are dealing with are idols that are in fact just pretty statues. However, that does raise the question of respect, because I can just picture some of these people being somewhat disrespectful to the traditions and culture of the region that they are visiting. While many Christians simply view the Buddhist statues as being simply a lifeless statue, my concern is that some are likely to actively be disrespectful to the culture.

So, the question rises as to respect. Where do we draw the line between worship and respect? Okay, some Christians won't enter these temples, though one I spoke to pointed out that he goes into banks and shopping centres, and in essence these places are cathedrals to the worship of money (I won't say capitalism because this goes beyond that). In fact Tim Keller points out in his book on idols (Counterfeit Gods) that not only is money a religion, but so is politics, and family. 

I guess in the end it comes down to where our heart lies. While I wouldn't bow before a Buddha, or burn any incense, I do think taking one's shoes off before entering the temple, remaining quiet, and respecting the traditions of the locals such as not showing your back to the Buddha, or standing over one, is not necessarily in the same category of worship. In the end the teachings of Christ are offensive enough (in that we aren't, and are never going to be, good enough to earn salvation), that we should not aggravate the situation by being another ignorant, rude, and obnoxious Westerner (and Thailand unfortunately seems to attract its fair share).

Are all Religions the Same?

One thing that I have noticed here in Australia is that for a long time the evangelical Church has been carrying on about how religions are not the same, but that has a lot to do with the secular belief that they are. To be honest, I'm not all that surprised that that is what they think because if we look at them we pretty much see the same performances dressed up in slightly different clothes. The thing is that sometimes I feel that some of these apologists are basically fighting losing battles, and in the end people don't really care about their arguments.

Look my position is no, religions aren't all the same, and this goes beyond the different clothes that they wear. For instance the eastern and western religions are vastly different, namely because religions in the west are monotheistic whereas religions in the east aren't. Secondly, Western religions are focused on the idea of getting to heaven when we die, and being good enough to earn a place there, whereas Eastern religions don't have a concept of heaven that we in the west have. In fact in the east the goal is to escape the endless cycle of death and rebirth, and to basically cease to exist - that is Nirvana. As a side note, I always find in funny how we have these westerners that carry on about how wonderful reincarnation is, when in reality it is actually something to escape. The other thing is that it is amazing the number of people who claim to be queen Nefertiti (and that nobody every claims to have been a peasant, or a slave, in a past life).

Then we have Christianity. Honestly, at face value, there is nothing about Christianity that sets it apart from the myriad of other religions out there. Many people simply treat it as such - they go to Church, tithe, don't do anything wrong, and pretty much behave as if when they die St Peter is going to be there, holding the pearly gates open and ushering them in. Sure, they believe in Jesus, but in the end they don't actually pay much attention to what he actually said, and simply view him as a good teacher. The thing is, at least in my mind, that this is not Christianity. The thing is that Christianity isn't about what we do, but rather what has been done. Further, Christianity isn't so much a religion, it is a relationship.

Yet, when I wandered into the Buddhist temples (actually, the proper term is Pagoda, so I will use that term from now on) in South East Asia, one thing I noticed is how similar they are to the churches and Cathedrals in the West. Sure, they are built differently, but if you wander through Catholic churches not just in Europe, but throughout the world, you will notice that there are things that are very much the same. For instance, in Catholic churches there are statues of the saints, and images of Jesus. The stations of the cross are positioned around the walls, and the larger churches even have shrines dedicated to specific saints. Further, in a Buddhist temple you will see people lighting incense, and praying before the statues. Guess what, they have in the churches - yep, incense, and candles. Oh, and the prayers, you can be assured that the people in Thailand are praying for exactly the same things that people in Europe are praying for - heath and wealth.

My South East Asian Discoveries

As I wandered around South East Asia I couldn't help notice that I would see Buddhist monks wandering around everywhere and it made me wonder whether they were attached to a pagoda in the way that a Christian Vicar is attached to a church, or whether they simply wander about as they wish. The reason that I queried that was that whenever I wandered into a pagoda the one thing that I noticed was that there didn't seem to be anybody there looking after it. Well, not quite because a few that I did enter did actually have people inside, it is just they didn't wear any religious garments, so I suspected that the people who look after the temples are probably just worshipers (which in many cases is the same when it comes to many of our Christian churches).

As it turned out, after some discussions, my question was answered and yes, they do tend to be attached to a pagoda, but they don't actually live there but rather quarters in the compound. For instance the Pagoda of the Emerald Buddha in Bangkok and the Silver Pagoda in Phnom Phem don't have any monks in them, namely because they are located inside the grounds of the respective palaces. Well, when I visited the Silver Pagoda I did notice some monks wandering around, but that was more because they were invited by the royal family. Interestingly, one of the kings of Cambodia actually spent a couple of years as a monk.

Anyway, the larger temples actually have quarters attached to them where the monks live. They don't actually pay to live in those quarters, but to become monks they have to be ordained - yep, as it turns out monks in Buddhism are more like priests as opposed to monks in Christianity, which is why the word monk is a little misleading. However, unlike Christianity (and Islam) there are no sermons. Rather, the monks will sit in the temple, or their quarters, and dispense wisdom to small groups and perform blessings. Mind you, they aren't supposed to have guests in their quarters, and when they do the doors have to be open - the monks live a very public life, and it is more than frowned upon for them to see people privately.

Now, you are probably wandering why it is that one of the kings of Cambodia was a monk. This surprised me as well because I thought that when one becomes a Buddhist monk one becomes one for life. Well, not quite, at least not in Theravarda Buddhism. While a lot of monks do become monks for life, this is not necessarily the case here, and in fact a number of them do so for further study, and it is particularly popular for people studying doctrates. In many cases though they become monks for a couple of years to spend time studying Buddhist scriptures. Also there are also nuns, but they tend to be quite rare, at least in Thailand and Cambodia.

Another interesting thing that is probably well known is the idea of the monks begging, yet when I think about it isn't that what happens in Christianity, yet for some reason we don't call it begging, we call in tithing. Okay, while tithing is supported biblically in that it frees up people for full time gospel work, sometimes I feel that maybe they are going a little bit too far, and I'm not necessarily speaking about pastors that live in multi-million dollar mansions. You see, one of my biggest concerns with tithing is that some churches seem to treat full time Christian work as being a rather cushy job. Well, there was a time when it was an incredibly cushy job, but that isn't the case these days.

However, sometimes I feel that there are churches where the staff are basically living off the blood, sweat, and tears of the congregation. In fact I've noticed that some people go into Christian work simply because they cannot deal with the real world, much in the same way that academics becomes academics. Sure, the smaller churches tend to struggle quite a lot, but the larger churches will have established training courses, and people will be tapped on the shoulder and be invited to consider Christian work. The thing that gets me is that they then turn around and heap praise on how this particular person has given up a lucrative a career to serve Jesus, when in reality these people are actually paid quite well (and considering some professions, it is a lot less stressful).

So, how does this relate to Buddism. Well, when we pictured Buddhist monks, we generally picture them wandering around the village and the villagers giving them food and money. Well, they wander around the city as well, or people visit the temples and leave donations. Yet for some reason we view this as begging, while we never seem to link begging with Christian gospel workers, which in the end that is what they are actually doing, yet because many of them tend to be very elegant speakers who are able to tug on our emotions, we are blinded to the reality. I was going to suggest that in Christianity some even go as far as suggesting that tithing is like investing money in the bank (well, they don't just suggest it, they outright say it), and that God's rate of return is much greater than any human financial institution could ever give us, and while they are not necessarily saying that the rewards are monetary, they know quite well that that is what their audience is thinking. However, I was then going to suggest that Buddhists give money and food to the monks (and in fact the monks get quite a lot of privileges) because it is the right thing to do, but then I realised that karma is a big thing over there, so in the end there is another similarity.

Creative Commons License
