The Jargon File (version 4.4.7, 29 Dec 2003):

Blue Glue
 n.

    [IBM; obs.] IBM's SNA (Systems Network Architecture), an incredibly losing
     and bletcherous communications protocol once widely favored at
    commercial shops that didn't know any better (like other proprietary
    networking protocols, it became obsolete and effectively disappeared after
    the Internet explosion c.1994). The official IBM definition is ?that which
    binds blue boxes together.? See fear and loathing. It may not be
    irrelevant that Blue Glue is the trade name of a 3M product that is
    commonly used to hold down the carpet squares to the removable panel floors
    common in dinosaur pens. A correspondent at U. Minn. reports that the CS
    department there has about 80 bottles of the stuff hanging about, so they
    often refer to any messy work to be done as using the blue glue.


The Free On-line Dictionary of Computing (30 December 2018):

Systems Network Architecture
Blue Glue
SNA

    (SNA) IBM's proprietary high level networking
   protocol standard, used by IBM and IBM compatible
   mainframes.

   Also referred to as "Blue Glue", SNA is a bletcherous protocol
   once widely favoured at commercial shops.  The official IBM
   definition is "that which binds blue boxes together."  It may
   be relevant that Blue Glue is also a 3M product commonly
   used to hold down carpets in dinosaur pens.

   [Jargon File]

   (1994-11-23)