239 lines
8.6 KiB
Plaintext
239 lines
8.6 KiB
Plaintext
Alternatives to OSI
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===================
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by Jock C. St. Martin
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University of the Outer Hebrides
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Scotland
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Following recent discussions concerning the relative merits of OSI and
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ARPA protocols, I decided to throw my hat into the ring. Furthermore,
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I believe that the ARPA protocols are not the only contenders with
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OSI, and that a number of even more "mature" mechanisms exist. I
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present seven possibilities for consideration.
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1. Bean tins and bits of string
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-------------------------------
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The use of bean tins and taut pieces of string has long been
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recognised as an effective means of communication. In fact,
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excavations from Anglo-Saxon dwellings in Nottingham show their use
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(albeit with imported coconuts as opposed to bean tins) in early
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everyday office situations.
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Bean tins and string have several advantages over OSI:
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a. They are fast, light weight and portable.
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b. They don't require the purchase of expensive computers.
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c. Complex error correction (based on the "NO - I said ..."
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principal)
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d. Uses off the supermarket shelf technology.
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e. They were not invented by the ISO.
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They also exhibit a very few trifling limitations:
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a. Poor support for "packet" switching (however, tin switching may be
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supported).
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b. Users often cut themselves on the tins.
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c. Star network topologies become more complex.
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d. They don't scale very well.
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2. Shouting from the roof tops
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------------------------------
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Shouting from the rooftops can be an effective method of optimised
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local area communication. It is based on the well understood CMSA/CD
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technology but with the notion of priority. Users can insert high
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priority traffic with the "If I might get a word in edgeways" packet.
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It is already in widespread use - e.g., the House of Commons,
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political canvassing and Speakers Corner. Naturally, a roof top is
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only necessary for high bandwidth traffic. The PTT's would probably
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assume this role. The average user would be content to shout in the
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street.
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Shouting has many advantages over OSI:
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a. It is not as "complex and obscure".
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b. Most people understand shouting.
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c. Broadcasts are easy.
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d. Its fun.
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e. It wasn't invented by the ISO
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OSI has hardly any advantages over shouting:
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3. Burning beacons on hill-tops:
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---------------------------------
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Burning beacons on hill-tops have long been used to warn of advancing
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Armadas and their like. However, the author believes that beacons may
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have wider applications than just these.
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In particular, they have the following advantages over OSI:
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a. No "dangerous checkpointing".
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b. They keep you warm.
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c. Not overly complex and obscure.
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d. A secondary use for the disposal of those nasty ISO people.
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e. Not cluttered with unnecessary functionality.
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f. Not invented by the ISO.
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Disadvantages to OSI:
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a. Not suitable for the office environment (this may really be
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an advantage in some circumstances).
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b. Low bandwidth (may also be an advantage - see 7)
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c. Error rates can be high. Arsonists, pyromaniacs and
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"Satanic Verses" burners can generate spoof packets.
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4. Semaphore
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------------
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Semaphore has been in use for many years. So why did ISO not consider
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this for international internetworking? This is difficult to
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determine, but is probably due to political motivations rather than
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any deficiencies in the protocols. Naturally there are a few rough
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edges to be addressed.
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Advantages over OSI
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a. Broadcasts are easily accommodated.
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b. Widely supported off-the-shelf infra-structure (boy scouts).
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c. Not invented by ISO
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Disadvantages over OSI
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a. Not so useful at night (but a working party on luminous
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flags is in progress).
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b. Bandwidth is rather low - but automation should help.
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5. Messages in bottles
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----------------------
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This is a low cost solution to networking. Bottles are easy to obtain
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and with a little development, this neglected backwater of
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communications technology could be a real alternative.
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Advantages over OSI
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a. High bandwidth data channels already in existence (e.g. the
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gulf stream, rivers and sewers.)
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b. Large amounts of data can be placed in the appropriate
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sized bottles.
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c. Not invented by ISO.
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Disadvantages to OSI
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a. Transit time is unpredictable (but then IP, for instance,
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does not guarantee any bounded delivery time)
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6. The Telephone
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----------------
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This might be seen as an enhancement of method 2. However, there is a
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lot to be gained from this approach. The name lookup problem is
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already solved as are routing issues. Lets face it, communications
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protocols are ultimately used for communicating between people. So why
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not just standardise the telephone. Add on services such as broadcast
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agents (commonly called gossips/operators) are easy to achieve.
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Advantages over OSI
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a. Its a mature existing technology.
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b. Directory services issues, routing and charging are
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already established.
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c. It's now available in portable form.
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d. Not invented by ISO
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Disadvantages to OSI
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a. Because it's a mature technology, there aren't so many
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interesting research areas.
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b. As a result of 2. there are few exotic conference openings.
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c. It costs money.
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7. Not communicating at all
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---------------------------
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One question I asked myself was "why communicate at all?" On
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consideration it was realised that not communicating has the following
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advantages over OSI.
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a. Low consumption of bandwidth.
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b. Cheap and easy to manage.
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c. No one disagrees with you.
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d. Without the time wasted on communication, other business
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proceeds much quicker.
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e. Not invented by the ISO
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No known disadvantages to OSI.
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The ARPA protocols.
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----------------------
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The ARPA protocols deserve consideration along with many of the above
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mentioned methods of communication. In particular, they have one
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major advantage over OSI.
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a. Not invented by the ISO
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However, despite this overwhelming advantage of the Internet protocol
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suite, the ISO proponents simply will not give in. In this section I
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therefore give a few other reasons for the superiority of the Internet
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suite - as if 1. was not enough.
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Scalability. The Internet protocols are obviously scalable as has been
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proved time and time again. All that is required is for the PTT's to
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take the sensible step of providing a network infra-structure and the
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rest can be solved. Charging is easily accommodated - the PTT's pick
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up the bills.
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Network interface. Many people have commented on how convenient it is
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to have a network address which fits into a common word size. This is
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such a advantage that the limitations are really insignificant. If the
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address space ever gets used up there is an obvious extension
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mechanism - the waiting list.
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Session layer. The Internet suite sensibly disregarded session
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services as superfluous. As has been observed, checkpointing is
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inherently dangerous as it can lead to loss of network usage and
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revenue. OSI has been influenced by the Internet community here, and
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has provided a session service complex enough that most
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implementations try and ignore it.
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Presentation layer. Again the Internet triumphs. It is quite clear
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that for the most part applications only need to exchange data
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consisting of bytes of 8, 16 and 32 bit quantities. These simple
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structures can be used as building blocks to construct almost any
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structure required. If this is not sufficient, there is a simple
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escape mechanism provided, known in the jargon as a "string encoding".
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It is quite clear that ASN.1 is just over the top - CHOICE's and
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OPTIONAL's are for quiche-eating indecisive applications.
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Application layer. Well the Internet has got this one too. Honestly,
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it's quite obvious that each application should do its own thing.
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That's what they're there for. If an application needs remote
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procedure call interface, or security, or name lookup, then it can do
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it itself rather than forcing it to use some more general service like
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ROS or directory services.
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SUMMARY
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-------
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In summary, I feel that all of the above methods are orders of
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magnitude better than OSI (which incidently, and by coincidence,
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wasn't invented here). In particular, I feel that method 7 offers the
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greatest potential and, with this in mind, WE DO NOT WELCOME ANY
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FURTHER COMMENTS YOU MIGHT HAVE!
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Author's note
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-------------
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This article is in no way connected with either Julian Onions or Steve
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Benford of the University of Nottingham beyond their role as postal
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agents for the author.
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--
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Julian Onions
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