Wireshark · Ethereal-dev: Re: [Ethereal-dev] Not understanding something in LLC

[Guy Harris <guy@xxxxxxxxxxxx>]

Eduardo Escudero Sánchez wrote:
> Hi . I have been searching in a lot of pages and in books to see if 
> there could be LLC frames other than those that have a 0x03 control 
> field value using SNAP (so they have 5 additional bytes after the LLC 
> control field) and i have found that many of them say that the control 
> field must have the 0x03 value;

I found one that doesn't.  It says:

	The LLC control field (CTL) is shown for PDU type UI, Unnumbered 
Information, which is the most commonly used PDU type in this context; 
*however, other information-carrying LLC PDU types may also be used with 
SNAP*.

(emphasis mine).

Its short title is "IEEE Std 802®-2001", and its full title is "IEEE 
Standard for Local and Metropolitan Area Networks: Overview and 
Architecture".  I'm somewhat more inclined to believe the IEEE than 
Javvin or McGraw-Hill on this matter.

> I have thought that maybe the 
> connection must be identified in the AA-LSAP-situation witha n 
> additional 5 five identifier (the SNAp of teh upper protocol)

That's what I would expect anything managing LLC Type 2 connections 
using SNAP to do.
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