🚀 go-pugleaf

> /* Written  7:04 pm  Apr  3, 1986 by djo@ptsfd.UUCP in ico:net.dcom */

> It means that they will be using some or all of the hundreds (literally) of 
> protocols ISO and/or CCITT are suggesting now or have in the past six to ten 
> years.  It also means that they want you to buy their product.
Partially true, but misleading.  There are indeed a number of
protocols definede, but they are at a number of different levels of
the reference model. 

> Find out what they mean.  A good default is (layer 1) rs-232-c/v.35; (layer
> 2) LAP B; (layer 3) X.25.  They may also support such things as X.75 but don't
> bet on it.  Layers 4 and up will be their own protocols.
Some good advice.  Anyone buying or implementing ANY protocol should
find out what they mean.  You really need to know what the standards
are for each layer.  This is true for protocols such as TCP/IP as well
(just because two vendors support TCP/IP doesn't mean that they
support the same physical media).  As far as layer 1 is concerned, ISO
has already adopted the IEEE 802.{3,4} families.  There are standards
at Layers 1-5 and Draft International Standards at layers 6 and 7.  To
be a real ISO network, you must support the standards at all layers.
Some vendors will have their own protocols at the higher layers for
services specific to that vendor.  There are also "national"
guidelines for the implementation of the various protocols to ensure
conformance between the various vendors.  For example, the National
Bureau of Standards will soon issue an X.400 product description which
specifies which options are mandator/optional/etc. for a US
implementation of X.400.  Similar specifications exist for other
protocols such as transport. 

In essence, it will be possible to build an ISO-OSI product that will
work with other vendors implementations.  The MAP and TOP
specifications are just such a set of guidelines.  TOP specifies such
things as IEEE 802.3 as the physical layer, IEEE 802.2 as the link
layer, ISO connectionless network protocol at the network layer,
ISO transport class 4 (NBS spec) for the transport layer, ISO session
(specific subsets) at the session layer, ISO ASN.1 at the presentation
layer and ISO FTAM and CASE at the application layer.  There is more
to it than just those, but this list specifies a full ISO protocol
suite at all layers.  By implementing to the specifications,
compatible implementations can be made.  The vendors are also working
together to pass conformance tests on their products.

> >What does it mean, "DECNET will conform to ISO?"
> It means DEC wants you to buy DECNET.
It also means that DEC will provide ISO transport protocols on DECNET.
They will probably provide some of the higher level protocols as well.
They have announced availability of ISO transport class 4 already.

> No.  The standards for layers 4 and up are WAY up in the middle of the air (see
> that wheel inside that other wheel?> )
Not true!  Standard protocols exist for layers 4 and 5.  Layers 6 and
7 have gone to DIS form (Draft International Standard) and are
supposed to go for 6 month ballot in June.  There should be
International Standards at all 7 layers by the end of 1986.  Standards
DIS level are also stable enough for an initial implementation.
Transport has been a standard for quite some time.  Session a little
less, but it has been about a year.