Subject: [NSIS] GIST extensibility concern (IANA considerations)

From: Henning Schulzrinne <[email-masked]>
Date: Mon, 13 Feb 2006 21:37:36 -0500

On re-reading the extensibility section in the IANA considerations, I  
have a concern that the mechanism as specified will lead to  
interoperability problems. In several cases, e.g., for object types  
and message types, there is a range for "private/experimental use".  
However, in all these cases, the range is small. For example, for  
GIST Message Type, only 8 values are available. Thus, if there are  
two experiments going on in the Internet, it is extremely likely that  
the two experiments will clash accidentally. In other words, such  
experiments are rather unsafe unless you operate a very tightly  
controlled, closed network. It certainly wouldn't be suitable for,  
say, Internet2-scale experiments or a vendor-specific experiment.

In other protocols, private extensions are usually designed so that  
it is *un*likely that two entities would pick the same identifier. As  
an example, header names (e.g., X- headers in email) are designed so  
that two parties can build new extensions, with only a modest  
likelihood of accidental collisions. DHCP also has vendor-specific  
codes that have a similar design.

I don't think we want to extend the GIST Message Type, for example,  
beyond 8 bits, as this is likely wasteful. The only alternative is to  
have an escape mechanism that adds a message type object with a long,  
random identifier (e.g., a GUID) for such private message types or  
uses the DHCP-style mechanism.

Henning

_______________________________________________
nsis mailing list
[email-masked]
https://www1.ietf.org/mailman/listinfo/nsis