Depth vs. offset in rules

[Research <research () nativemethods com>]

Hi,

In reading chapter 3 of the Snort 2.9.7.0 manual, I have a clarification question for the use of “depth” vs. “offset”.

Depth appears to specify where to start a content match in the packet payload, so if I understand correctly:

        depth:5;

…would mean begin content matching 5 bytes into the packet payload.

When compared to offset, does that mean offset relative to the depth ?  So:

        depth:5; offset:10; …

…means start at byte 5 in the packet payload and an offset from the depth as a starting location of another 10 bytes ?  
I am thinking that is correct because I note that offset can have negative values and a negative starting point for a 
packet payload would not make sense, but as an offset it would.

Thanks
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