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Text File | 1992-06-23 | 15.4 KB | 372 lines

AMPRNET TCP/IP Newsletter Mike Chace - G6DHU Issue 5 Volume 1 - September 1991 1. This Month Welcome to issue 5 of this newsletter for the UK TCP/IP community. If you are a beginner in the world of TCP/IP or perhaps considering taking the 'plunge' then perhaps this will be of interest to you! If you are a more experienced user reading this for the first time, then hello, and I hope you'll find something of use too. This month's topics are :- 2. IP Addressing 3. Software News 4. Network News 5. Tutorial - Datagrams and Virtual Circuits 6. 221 Closing 2. IP Addressing 2.1. Background Just as all radio amateurs worldwide can be identified by their unique callsign, TCP/IP users can be uniquely identified by their IP address. IP (the Internet Protocol) being the protocol used for routing packets amongst TCP/IP users. IP works out where to send packets amongst TCP/IP users by using the IP address just like for instance, a NET/ROM node uses the callsign of a distant node to identify where to send packets. IP addresses are also coordinated worldwide, with a huge address database being held on computers at the University of California at San Diego (UCSD). This database holds details of everyone (and everything) that uses an IP address. These users form a network (called the Internet). When blocks of addresses were being allocated to specific types of IP users, Radio Amateurs were also allocated some of these. The resulting Radio Amateur 'Internet' is known as the AMPRNET - AMateur Packet Radio NETwork. 2.2. What is an address ? Well, now I've explained a little background to the subject of addressing within TCP/IP, I suppose I'd better show you what one looks like. All Internet addresses are 32 bit numbers. That's all! The standard way of writing an address is to write it as the decimal equivalent of the 4 bytes that make up the address. For example my address would be written as 44.131.20.3 As you can guess, the point of writing addresses this way (apart from making them more humanly readable) is to convey some extra information about the address. AMPRNET addresses can be broken down as follows :- 44 = AMPRNET 131 = UK 20 = Geographical Region 20 (in UK) 3 = The third address issued in region 20 As you can see, AMPRNET was allocated the block of addresses from 44.0.0.0 to 44.255.255.255 so everybody in the Internet knows that 44 corresponds to an AMPRNET address. The AMPRNET address coordinators chose to split the block of addresses between countries and so the UK has addresses 44.131.0.0 to 44.131.255.255. Furthermore, the UK address coordinators chose to split UK addresses on an RSGB region basis which as you will see below correspond roughly to three counties. It's all very hierarchical as you can no doubt appreciate. There are lots more aspects to IP addressing not mentioned here (such as network classes) but I hope the discussion above helps beginners to appreciate a little more about addressing and how it's defined. 2.3. Getting Your Address As a beginner, you'll probably want to know how you can get hold of your IP address so that you can start experimenting with TCP/IP on the AMPRNET. Address coordination in the UK has recently changed to a more regional approach with one person in each of the 21 UK addressing regions taking responsibility for allocating addresses locally. Once a month, each of these local coordinators sends an update of newly allocated addresses to the UK AMPRNET Address Coordinator who is currently Chris, G6PWY who can be found at GB7PWY. Every few months the whole of the UK's IP addresses are published in a number of bulletins sent to TCPIP@GBR. The format of these bulletins are such that they can be used directly as input to a program than can build the file of TCP/IP stations used by the NOS software. If you are a beginner and don't know who your local IP coordinator is, you can either send mail to Chris as above, who will tell you who to contact locally, or you can see if your local mailbox has any TCP/IP information. Most mailboxes have a files area dedicated to TCP/IP and you maybe able to find your local coordinator's name and address there. Once you've found your local coordinator, you need to supply him/her with the following details :- Your Callsign (eg G6DHU) Your Christian and Surnames (eg Mike Chace) Your IARU QTH Locator (eg IO81tj) Your Nearest Postal Town (or full address) (eg Bath) Your Local Mailbox (eg GB7IMB) Within a few days (or less) you will be allocated your very own address. Please note that if you are desperate to get onto TCP/IP and know locals already on the mode, you can always agree a temporary address to tide you over before your 'official' one is allocated. Well, that's the process. Here is the list of UK IP Address coordinators together with the coverage of each of their areas. IP REGIONAL CO-ORDINATORS AUGUST 1991 REGION CALLSIGN NAME @BBS REGIONAL AREA 1 G4TUP DAVE GB7BPL Lancashire,Cheshire,Merseyside, Cumbria,Greater Manchester,I.O.M. 2 G0BSX PETER GB7BSX Humberside North of the river Humber, N. S. W. Yorkshire. 3 G1FNQ TERRY GB7SAM Hereford & Worcester, Salop,Staffordshire Warwickshire,West Midlands. 4 G4KLX JONATHAN GB7HMZ Humberside South of the river Humber, Derbyshire,Leicestershire, Lincolnshire Nottinghamshire. 5 G3NRW IAN GB7BIL Bedfordshire,Cambridgeshire, Northamptonshire. 6 G1PLT PAUL GB3XP Berkshire,Buckinghamshire, Oxfordshire 7 G8GGI BOB GB3XP Greater London south of the river Thames,Surrey. 8 G8ZHR NICK GB3XP Kent,East & West Sussex. 9 G3KFN ALAN GB7PLY Cornwall & Devon. 10 VACANT Dyfed,Gwent,Mid Glamorgan,Powys, S & W Glamorgan. 11 GW4HDR ALAN GB7OAR Clwyd,Gwynedd. 12 GM4YED ROBIN GB7EDN Grampian,Highlands,Orkneys,Shetlands, Tayside,Western Isles. 13 GM4YED ROBIN GB7EDN Borders,Fife,Lothian. 14 GM4SGB SUSAN GB7SAN Central,Dumfries & Galloway, Strathclyde 15 GI0PEZ DAVE GB7TED Northern Ireland. 16 G8KBB DAVE GB7MXM Essex,Norfolk,Suffolk. 17 G4WPT DAVE GB7BNM Dorset,Hampshire,Wiltshire. 18 G6AUC HARRY GB7NCL Cleveland,Durham,Northumberland, Tyne & Wear. 19 G8FSL ANDREW GB7HSN Greater London north of the river Thames,Hertfordshire. 20 G6DHU MIKE GB7IMB Avon,Gloucestershire,Somerset. 21 VACANT Isle of Wight,Channel Islands. 3. Software News Well, not much to report since the last newsletter I'm afraid! PA0GRI is currently taking a well earned holiday and has left his last release at v1.7h. I don't think there is anything exciting in that release just a few tweaks to the code here and there. WNOS from DB3FL is expected to be released at v2c soon. Mike Dent (G6PHF @ GB7ULV) and Neil Mercer G3UVQ have added some useful code to the G1EMM/PA0GRI baseline to allow SMTP headers to be stripped from mail that is gatewayed from TCP/IP stations to AX.25 BBSes or PMSes. Also included are a few commands to add a BBS NIC and some other information to bulletins mailed from a TCP/IP station. Please contact Mike for details. Those of you (any ?) running a Unix machine may be interested to know about some German software called WAMPES (Wuertemberg Amateur MultiProtocol Experimental Software). This runs under HP/UX and 386-IX Unix and supports :- TCP, IP, UDP, Telnet, FTP, SMTP, finger etc AX.25 with autorouting and hop2hop acknowledgment TCP convers (chat) node on port 3600 NET/ROM (L3 and L4 only) Full user access to unix shell for mail, news etc Perhaps the most interesting of the features is the TCP based convers node - a novel idea. A number of German nodes (eg DB0ID) are using this software and it seems to work well. This is the sort of thing I'd like to see in the UK but we'll need a far better RF network first! I'm still in the process of finding out about this software (despite not having the dosh for a 386, let alone Unix box :-). If you would like info, drop me a line and I'll translate the German text and pass it along but please *don't* ask me for the software - I haven't got it! 4. Network News Just a small section - this time from Chris G6PWY - about his local IP network. In his own words.... A few months ago you asked for info on TCP/IP activity in our local area, there are a number of local 24 hr stations in region 1, namely GB7PWY, GB7TCP, G0GSR, G6CRV, G6PHF, G4TUP, the only stations to take true 3rd party mail are GB7PWY and GB7TCP, both stations take mail onto the NTS network, GB7PWY operates on 144.625 (TCP/IP), 432.675 (FBB bbs with bpq node linked to 144.625 on a serial cable) on both ports I can take mail addressed to any where both national and international, with replies either on TCP/IP or NTS. I'm not sure on the setup for GB7TCP. One of the other stations G0GSR is located at a good site on top of Winter Hill, near Bolton, he can take smtp mail for almost all of region 1, if he can't get it there direct, there are other routes to use. Thanks Chris. If you would like to let others know about what your local network is doing, please drop me a line at any of the addresses at the end of the newsletter. 5. Tutorial - Datagrams and Virtual Circuits A number of users seem to be confused as to what these terms actually mean and what they are. I'll attempt to explain here! Let's think about AX.25 as we are all used to it. In case you hadn't realised, there are actually two distinct ways to send packets containing information using AX.25 at Level 2. (Note: I use the terms 'frame' and 'packet' interchangeabl here) The first way is to connect (eg CONNECT G9ZZZ) tod forth (using I (Information) frames) and these get acknowledged, ensuring that they got to the other end intact. The second method is a little less obvious. Think about all those packets you see addressed to BEACON (yechhh!), and ID. They aren't addressed to any one station but they do send information. As you probably have also seen, these kinds of packets get sent with a type of UI (Unnumbered Information). It should now be pretty obvious that the first method sets up a circuit between the two stations *before* data (information) is sent. This is the so-called Virtual Circuit. The second method is really a Broadcast and as such it conveys information *without* setting up a 'circuit' first. How does this relate to TCP/IP ? Well, since TCP/IP can use AX.25 at Level 2 (the link-layer) to send it's information it is able to exploit both these methods to send information except this time the information is of course TCP/IP data. The NOS/NET 'mode' command sets whether we will use datagrams (UI broadcasts) or virtual circuits to send TCP/IP data. That is... net> mode 144 datagram # We'll use 'broadcast' mode or net> mode 144 vc # We'll use virtual circuit mode Enough waffle - lets take a real example. G6DHU-5 is in direct range with G4WRW-5. We both set datagram mode as above and then start a telnet session. The software now just 'wraps up' TCP/IP frames addresses them to the other station and sends them out as broadcasts. So someone watching with 'trace' would see something like G6DHU-5 -> G4WRW-5 UI PID=IP data......data When we finish, there's nothing to do except close the TCP/IP connection and just stop sending the broadcasts. In the other case, we would set mode to vc and the following would happen; transparently, my software would send a connect to G4WRW-5, wait for the ack and then start sending data back and forth, so someone watching might see :- G6DHU-5 -> G4WRW-5 I S5 R7 PID=IP data....data G4WRW-5 -> G6DHU-5 RR NR=6 (the acknowledgement) When we finish, again the TCP/IP connection is closed but then (again transparently) the software disconnects at Level 2 by sending a disconnect packet to the other station. What use is all this then ? Well, you may have realised that in the case where broadcasts are used, there are no acknowledgements (at the AX.25 level). This means that using datagram mode has the advantage of being more effecient and faster over *reliable* paths (i.e when a broadcast isn't often lost). Virtual circuits are a better bet when the path is poor and we need the security of the AX.25 acknowledgements to tell us that the TCP/IP info got to the other end OK but the disadvantage is that we must always wait for AX.25 to do it's job for us and if the path is particularly poor the retries may mean a slower (but more reliable!) link. Remember that just because I've shown a direct connection between two stations, doesn't mean that you are restricted to this in either datagram or VC mode! You can use ARP to set a digipeater path between stations if necessary. 6. 221. Closing As usual, my 'TCP/IP Beginner's Information Package' is available, if you send me a disk (MSDOS 1.44M/720k 3.5inch or Atari ST) a return address label and the return postage. Back Issues of this newsletter can also be included on the same disk if you wish. Please send suggestions and articles for inclusion to me at the following addresses ; 84 Frankland Close Bath Avon BA1 4EL or via e-mail (mikec@praxis.co.uk), AMPRNET g6dhu.ampr.org [44.131.20.3] or AX.25 NTS BBS (G6DHU@GB7IMB). I can accept material on 1.44M/720k IBM/MS-DOS and Atari ST 3.5 inch format disks and if you want them back PLEASE include the return postage. All material greatfully received! 73 until next time, Mike. [End Of Newsletter]