spec: User-configurable Minimum Duration Between IMSI Changes
diff --git a/docs/imsi-pseudo-spec.adoc b/docs/imsi-pseudo-spec.adoc
index eaacd0c..90fec9b 100644
--- a/docs/imsi-pseudo-spec.adoc
+++ b/docs/imsi-pseudo-spec.adoc
@@ -325,10 +325,6 @@
[[sms-structure]]
==== Next Pseudonymous IMSI SMS Structure
-// FIXME
-IMPORTANT: This is a draft. The structure is likely to change after the
-reference implementation phase.
-
.Next pseudonymous IMSI SMS structure
[packetdiag]
----
@@ -342,6 +338,10 @@
}
----
+// FIXME
+IMPORTANT: This is a draft. The structure is likely to change after the
+reference implementation phase.
+
IMSI_PSEUDO_I: 32 bits::
See <<hlr-imsi-pseudo-i>>.
@@ -422,5 +422,21 @@
=== User-configurable Minimum Duration Between IMSI Changes
+It may be desirable to let subscribers configure their minimum duration between
+IMSI changes. This allows subscribers with a high privacy requirement to switch
+their pseudonymous IMSI more often, and it allows the pseudonymous IMSI change
+to happen less frequently if it is distracting to the subscriber.
+
+How distracting the pseudonymous IMSI change is, depends on the ME. The
+following examples were observed:
+
+// FIXME: might need an update after SYS#4481
+
+* A Samsung GT-I9100 Galaxy SII smartphone with Android 4.0.3 displays a
+ message at the bottom of the screen for about 5 seconds, but the user
+ interface remains usable.
+* A Samsung GT-E1200 feature phone displays a waiting screen for 16 to 17
+ seconds and is unusable during that time.
+
<<<
include::./common/chapters/gfdl.adoc[]