NOTES: Describe the current allocation of capability bits.

Signed-off-by: Mark Wooding <mdw@distorted.org.uk>

diff --git a/NOTES b/NOTES
index f5ebc65..62b5e64 100644 (file)
--- a/NOTES
+++ b/NOTES
@@ -218,8 +218,17 @@ Capability flag bits must be in one the following two categories:
    applicable.  They may also appear in MSG1, but this is not
    guaranteed.  MSG4 must advertise the same set as MSG2.
 
    applicable.  They may also appear in MSG1, but this is not
    guaranteed.  MSG4 must advertise the same set as MSG2.
 

-No capability flags are currently defined.  Unknown capability flags
-should be treated as late ones.
+Currently, the low 16 bits are allocated for negotiating bulk-crypto
+transforms.  Bits 8 to 15 are used by Secnet as default capability
+numbers for the various kinds of transform closures: bit 8 is for the
+original CBCMAC-based transform, and bit 9 for the new EAX transform;
+bits 10 to 15 are reserved for future expansion.  The the low eight bits
+are reserved for local use, e.g., to allow migration from one set of
+parameters for a particular transform to a different, incompatible set
+of parameters for the same transform.  The high 16 bits have not yet
+been assigned a purpose.
+
+No early capability bits are currently defined.

 
 
 MTU handling
 
 
 MTU handling