Wireshark · Wireshark-dev: Re: [Wireshark-dev] [PATCH] UMTS Frame Protocol: more K12/K15 support, Spare Extension fields

[Kriang Lerdsuwanakij <lerdsuwa@xxxxxxxxxxxxxxxxxxxxx>]

Martin Mathieson wrote:

> One of the reasons I hadn't added Spare Extension before if that I've 
> never seen it appear in frames in practice, and it sounds as though 
> you had to fake it in order to test your patch?  It'll be good to have 
> it for completeness though!  Do you happen to know of any equipment 
> that does write out Spare Extension bytes?

I think this Spare Extension is useful to detect when there is a 
mismatch between the
version of FP assumed by dissector and the version actually captured. 
Looking at
Release 7 specification, for example, there is a new field Ext. 
Propagation Delay added
to RACH DATA FRAME (TS 25.425 Figure 9). Using Release 6 dissector this 
should
show up as Spare Extension.  (This could be either mean that user hasn't 
upgrade Wireshark to latest version, or we haven't update FP dissector 
code to handle newer releases yet.) Such field is flagged as warning in 
expert information by the patch.

I am not aware of any equipment producing these right now. And yes, the 
test example
has been edited by hand. But it should be useful down the road.

Best regards

Kriang Lerdsuwanakij