xkcd today- lovely.
in [UK Mac]
|
Prev: Unsupported Firefox...
Next: It's here (at last)
From: Rowland McDonnell on 23 May 2010 09:56 Tim Streater <timstreater(a)waitrose.com> wrote: > real-address-in-sig(a)flur.bltigibbet.invalid (Rowland McDonnell) wrote: > > > Mark Bestley <news{@bestley.co.uk> wrote: [snip] > > The RFCs are not where anything comes from - they are a deliberately > > hard-to-understand ueber-technical ueber-concise summary of what's what. > > > > They are impossible to understand unless you have the right background - > > that is, unless you've immersed yourself in that sort of thing, and had > > a lot of help to understand it while doing so. > > This tends to be true, unfortunately, since initially the RFC will be > written by a super-geek and intended for similar super-geeks to comment > on and improve via a dialogue between them. Even though I have some > knowledge in the field, it's quite unlikely that I'd have been able to > contribute to that sort of discussion. It does mean that at the cutting > edge of a field, hard-to-read docs are all there is. That's not the problem; the problem is that the people who do understand those docs have no interest in helping other people understand those docs. The idea is `If you don't get it, you're a lamer and we don't want to know you'. The idea is to establish a technical aristocracy. The techies like not being bothered by idiots; and the firms like it because since hardly anyone understands how to program and control computers these days, almost all of us have to buy our software from them. It's all about exclusion and exploitation - the founding principles of the USA as it happens, along with wholesale land-theft, genocide, and slavery. > It's only a bit > later,as the field takes off, that something approaching proper text > books start appearing. But such things accessible to those other than already highly skilled already well informed existing technical experts are very rare. I've read modern computer manuals - there seem to be two types. The `consumer' manuals which are little more than a poorly structured collection of tips and tricks considered `cool' by the author; and the `serious' manuals which might well be more complete but certainly are impenetrable to the layman (i.e., me). I never had this problem with old-style computer manuals, but something went wrong in the 1980s with writing that sort of thing. It got bureaucratized, did the process, and all the technical manuals I've read recently have been unfit for purpose. All of 'em. > But there's still a tendency for someone to say, > if there's any doubt about a point, "What does the RFC say?" Yeah, I know - and people need to get the hang of the idea that since RFCs are not meant to be accessible documention, then it's an obstructive thing to do, pointing someone at an RFC like that. It's not helpful, is my point. -- Remove the animal for email address: rowland.mcdonnell(a)dog.physics.org Sorry - the spam got to me http://www.mag-uk.org http://www.bmf.co.uk UK biker? Join MAG and the BMF and stop the Eurocrats banning biking
From: David Empson on 23 May 2010 09:58 Rowland McDonnell <real-address-in-sig(a)flur.bltigibbet.invalid> wrote: > David Empson <dempson(a)actrix.gen.nz> wrote: > > > Rowland McDonnell <real-address-in-sig(a)flur.bltigibbet.invalid> wrote: > > > > > David Empson <dempson(a)actrix.gen.nz> wrote: > > > > Everyone with a NAT router (hundreds of millions of people) has their > > > > own private network, about half of which will be in the 192.168.x.x > > > > range. There will be millions of people using the address 192.168.0.1, > > > > for example. > > > > > > > > None of them can talk to anything outside their own network using that > > > > address. > > > > > > But I don't know what `their own network' might mean. > > > > The set of computers connected to the same Ethernet and/or WiFi network, > > I can do IP over LocalTalk here, I think... It's understanding what > defines `their own network' that I'm short of at the mo. Again, simplifying things: for anyone with a single connection to the Internet via a broadband router, "your own network" is every device connected via either Ethernet or wirelessly on your side of the router (plus the router itself, at least the "inside" half of it). > > using a compatible set of IP addresses (e.g. all using addresses in the > > range 192.168.0/24). > > Compatible set of IP addresses? All devices on the same network must use the same subnet mask and have addresses which match for the elements indicated by one bits in the subnet mask, and have unique addresses for the elements indicated by zero bits in the subnet mask. For example, if your router uses an address of 192.168.0.1 and has a subnet mask of 255.255.255.0, then all computers on your network must use unique addresses in the range 192.168.0.2 through 192.168.0.254 and also have a subnet mask of 255.255.255.0. (This is normally taken care of by the DHCP server in your router.) Packets addressed to the same network (using the subnet mask to compare the computer's own address to the destination address) can be sent directly, not involving the router. Packets addressed to a different network must be sent to the router, which forwards them to the appropriate network, via another router at your ISP, and on through other routers as required to reach the destination network. Ultimately the final router in the chain recognises that the destination address is on its own network and delivers the packet to the appropriate computer. > > For most people with a broadband connection, that's all computers on > > "your" side of the router (plus the side of your router which is > > connected to your network). > > That makes sense. [...] > > > But how does this all work? What confidence can one have that it does > > > work as you describe? What confidence can one have that it never goes > > > wrong? > > > > Because you wouldn't get a connection to the server if the NAT routers > > didn't work or were misconfigured, and it is completely impossible for > > Internet traffic to be sent to a 192.168.x.x address because those > > addresses are not routable by any router on the Internet. > > Oh - okay. So I've been worried by something that shouldn't have > worried me, then. Correct. -- David Empson dempson(a)actrix.gen.nz
From: Ian Piper on 23 May 2010 10:30 On 2010-05-23 14:45:33 +0100, Tim Streater <timstreater(a)waitrose.com> said: >> The RFCs are not where anything comes from - they are a deliberately >> hard-to-understand ueber-technical ueber-concise summary of what's what. >> >> They are impossible to understand unless you have the right background - >> that is, unless you've immersed yourself in that sort of thing, and had >> a lot of help to understand it while doing so. > > This tends to be true, unfortunately, since initially the RFC will be > written by a super-geek and intended for similar super-geeks to comment > on and improve via a dialogue between them. Even though I have some > knowledge in the field, it's quite unlikely that I'd have been able to > contribute to that sort of discussion. It does mean that at the cutting > edge of a field, hard-to-read docs are all there is. It's only a bit > later,as the field takes off, that something approaching proper text > books start appearing. But there's still a tendency for someone to say, > if there's any doubt about a point, "What does the RFC say?" I find the same with the W3C documents: they confuse comprehensiveness with comprehensibility. They *may* achieve one of these but definitely not the other! Ian. -- Ian Piper Author of "Learn Xcode Tools for Mac OS X and iPhone Development", Apress, December 2009 Learn more here: http://learnxcodebook.com/� --�
From: Rowland McDonnell on 23 May 2010 11:28 Tim Streater <timstreater(a)waitrose.com> wrote: > real-address-in-sig(a)flur.bltigibbet.invalid (Rowland McDonnell) wrote: > > > Tim Streater <timstreater(a)waitrose.com> wrote: [snip] > > The techies like not being bothered by idiots ... > > Very often true but not always. All sweeping statements are false[1]. > > > It's only a bit > > > later,as the field takes off, that something approaching proper text > > > books start appearing. > > > > But such things accessible to those other than already highly skilled > > already well informed existing technical experts are very rare. > > > > I've read modern computer manuals - there seem to be two types. The > > `consumer' manuals which are little more than a poorly structured > > collection of tips and tricks considered `cool' by the author; and the > > `serious' manuals which might well be more complete but certainly are > > impenetrable to the layman (i.e., me). > > I'd say that's because they're meant to be textbooks. The consumer books > are a waste of space. A textbook, if competently written, is not inaccessible. These computer manuals are inaccessible. I think that they are meant to be concise reference works for the fully informed experts - not textbooks. > > I never had this problem with old-style computer manuals, but something > > went wrong in the 1980s with writing that sort of thing. It got > > bureaucratized, did the process, and all the technical manuals I've read > > recently have been unfit for purpose. All of 'em. > > Mmmm, things did get more complex, though, wouldn't you say? Erm, nope - the tech got easier to use in itself, but the manuals got worse. The manuals for my HP32E are very much smaller and more useful than the manual for my HP32S (calculators). The difference? Ten years. They do pretty much the same job: the 1970s calculator had two excellent little manuals; the HP32S one whopping great big one which (looking at the non-programming bit only) used about four times as much text to say a good deal less. The later manual is bigger, contains less information, and is very very much harder to use and to understand. Modern technical manuals are written according to a dysfunctional scheme that causes them to be created `not fit for purpose'. [snip] Rowland. [1] Yes, I know. -- Remove the animal for email address: rowland.mcdonnell(a)dog.physics.org Sorry - the spam got to me http://www.mag-uk.org http://www.bmf.co.uk UK biker? Join MAG and the BMF and stop the Eurocrats banning biking
From: Rowland McDonnell on 23 May 2010 12:07
David Empson <dempson(a)actrix.gen.nz> wrote: > Rowland McDonnell <real-address-in-sig(a)flur.bltigibbet.invalid> wrote: > > > David Empson <dempson(a)actrix.gen.nz> wrote: > > > > > Rowland McDonnell <real-address-in-sig(a)flur.bltigibbet.invalid> wrote: > > > > > > > David Empson <dempson(a)actrix.gen.nz> wrote: > > > > > Everyone with a NAT router (hundreds of millions of people) has their > > > > > own private network, about half of which will be in the 192.168.x.x > > > > > range. There will be millions of people using the address 192.168.0.1, > > > > > for example. > > > > > > > > > > None of them can talk to anything outside their own network using that > > > > > address. > > > > > > > > But I don't know what `their own network' might mean. > > > > > > The set of computers connected to the same Ethernet and/or WiFi network, > > > > I can do IP over LocalTalk here, I think... It's understanding what > > defines `their own network' that I'm short of at the mo. > > Again, simplifying things: for anyone with a single connection to the > Internet via a broadband router, "your own network" is every device > connected via either Ethernet or wirelessly on your side of the router > (plus the router itself, at least the "inside" half of it). But what defines that as `your own network'? And I know that it doesn't have to be Ethernet/WiFi to be `my own network'. Like I say, I could be using IP over LocalTalk connected to Ethernet via a LocalTalk<->Ethernet bridge, for example. It'd all be `my local network', wouldn't it? > > > using a compatible set of IP addresses (e.g. all using addresses in the > > > range 192.168.0/24). > > > > Compatible set of IP addresses? > > All devices on the same network must use the same subnet mask and have > addresses which match for the elements indicated by one bits in the > subnet mask, and have unique addresses for the elements indicated by > zero bits in the subnet mask. Okay - that makes sense. `Subnet mask' - umm, I've never really got the hang of them. The basic concept of masking bits like that, yeah, got that. But what's a subnet mask in conceptual terms and - well, what uses the things for what? > For example, if your router uses an address of 192.168.0.1 and has a > subnet mask of 255.255.255.0, Where does this subnet mask come from? > then all computers on your network must > use unique addresses in the range 192.168.0.2 through 192.168.0.254 and > also have a subnet mask of 255.255.255.0. What's wrong with 192.168.0.255 as an address? > (This is normally taken care of by the DHCP server in your router.) > > Packets addressed to the same network (using the subnet mask to compare > the computer's own address to the destination address) What's using the subnet mask to do this? And where does it get the subnet mask from? And how does anything find out where to send anything for that matter? That is, how does the software work out that IP address 192.168.0.X is `that node on the Ethernet which is my computer' or `that node on the Ethernet which is my laser printer' or whatever. > can be sent > directly, not involving the router. > > Packets addressed to a different network must be sent to the router, Yeah, but how do they get there? That is, how does a computer know where to send these packets? I get the idea that in the wider internet, there are domain name servers which contain a full map (no idea how this works) so you can always look up that sort of thing. But I don't see how that works, and I've no idea at all how it works on a local network. > which forwards them to the appropriate network, via another router at > your ISP, and on through other routers as required to reach the > destination network. Ultimately the final router in the chain recognises > that the destination address is on its own network and delivers the > packet to the appropriate computer. Yeah, obviously the packets are addressed and end up going where they need to go, but - erm, how do they know to get there? [snip] Ta, Rowland. -- Remove the animal for email address: rowland.mcdonnell(a)dog.physics.org Sorry - the spam got to me http://www.mag-uk.org http://www.bmf.co.uk UK biker? Join MAG and the BMF and stop the Eurocrats banning biking |