1 07/15/82  Common access class ceiling
 2 
 3 Facilities like the Inter-Multics File Transfer (IMFT) facility
 4 translate Access Isolation Mechanism (AIM) attributes between two
 5 systems.  For these facilities, the concept of a common access class
 6 ceiling is used to control the data which may be transferred between
 7 the systems.
 8 
 9 The common access class ceiling between two systems is defined as all
10 sensitivity levels from level 0 (usually un-named) up to but not
11 including the first level which does not have the same long and short
12 name on both systems and all access categories that have the same long
13 and short names on both systems.
14 
15 If the long and short names of sensitivity level 0 are not the same on
16 both systems, then the two systems have no common acccess ceiling and
17 are isolated from each other.
18 
19 
20 For example, if system A defines the following AIM attributes --
21 
22           level 0        *-* UN-NAMED *-*
23           level 1        unclassified        u
24           level 2        secret              s
25           level 3        top secret          ts
26 
27           category 1     SSTD                sstd
28           category 2     LISD                lisd
29           category 3     FSD                 (none)
30           category 4     Marketing           (none)
31 
32 
33 and system B defines the following attributes --
34 
35           level 0        *-* UN-NAMED *-*
36           level 1        unclassified        u
37           level 2        restricted          (none)
38 
39           category 1     MPO                 (none)
40           category 2     LISD                lisd
41           category 3     FSD                 fsd
42           category 4     SSTD                sstd
43 
44 
45 then the common access ceiling is --
46 
47           unclassified, LISD, SSTD