Subject: Network Accessible Unit

From: "jim (j.) cobban" <[email-masked]>
Date: Thu, 10 Aug 1995 12:18:00 -0400

When SNA moved from the subarea model to the APPN model it was decided that
the name of the concept for which NAU was the acronym had to change.  So
instead of Network Addressable Unit, we have Network Accessible Unit.  The
new name is sort of silly, and I feel that the rationale for the change in
name is dubious.

In the subarea network, so the myth goes, every NAU had both a name and an
address.  Why do I call this a myth?  In order that every session could be
uniquely identified by a pair of "addresses" if a secondary LU had multiple
parallel sessions to a particular primary LU, the secondary LU was assigned
multiple "addresses".  A single Network "Addressable" Unit could therefore
have multiple "addresses" even though it was clearly a single entity.

In the APPN network NAUs do not have "addresses", according to this same
myth because LFSIDs are local to a particular link connection.

This is all hog-wash (and as a pig owner, I know hog-wash).  NAUs in both
APPN and subarea networks have addresses.  The address is a 3 to 17 character
string.  This name has all of the same properties as an address in any other
routing protocol.  The object which is subarea networks we called an address
is a Path-Control Layer address.  It has a different representation from the
PC layer addresses (LFSID/NCE) in APPN because a different PC implementation
is used.  But the object which we call a SNA name is simply a layer 4
address. 

APPN has a lot in common with X.25.  X.25 also uses locally significant
connection indices on each link, but it also has a global address which is
used to establish connections.  Why should it be significant that the X.25
address is composed of decimal digits, while the SNA address also contains
alphabetics?  Emphasizing this trivial detail just adds to the philosophical
isolation from the rest of the inter-networking world which APPN has built up
for itself.  Referring to the SNA name of an NAU as an address will make it
much easier to explain APPN to people who have not grown up in the IBM
stable.

So I think we should kill this politically-correct interpretation of NAU, and
go back to calling it a Network ADDRESSABLE Unit.

Jim Cobban   |  [email-masked]                        |  Phone: (613) 763-8013
BNR Ltd.     |  bnrgate.bnr.ca!bcars153!jcobban       |  FAX:   (613) 763-5199
|                                                                             |
|   The opinions expressed are those of the author and do not necessarily     |
|   represent the opinions of Bell-Northern Research or Northern Telecom.     |

---

From: [email-masked]
Date: 10 Aug 95 12:43:33 EDT

Jim - 

Although I have a great admiration for the work you're doing through the AIW to 
address some really key issues, I feel compelled to express my opinion on this 
one.

Other than Gary Schultz (the SNA Editor... for whom I also have a great deal of 
respect), I don't believe there's anyone else on this planet who cares.  In 
addition, I was wondering how you would suggest we police such violations of 
the meaning of the NAU acronym?  :-)

Regards, Dave