[c-nsp] debug mpls packet

[roy]

Hobbs wrote:
> 
> 
> On Tue, Nov 17, 2009 at 8:38 PM, roy <bandwidth.user at gmail.com 
> <mailto:bandwidth.user at gmail.com>> wrote:
> 
>     Oliver Boehmer (oboehmer) wrote:
> 
>          
> 
>                             Does anyone know what the middle number
>                             represents in a "debug
> 
>         mpls
> 
>                             packet" ( eg: {7963 6 254} )?
>                             I can't find this information anywhere.
> 
>                             7693 = Label
>                             6 = ???
>                             254 = I presume is the TTL
> 
>                             What does the 6 represent??
> 
>                         it's the EXP value. you're right about the last
>                         being the TTL.
> 
>                                oli
> 
>                     Could it be the 3-bit EXP and 1-bit Bottom of Stack
>                     Flag combined?
> 
>                 Hmm, why do you think so? Looking at the code, it only
>                 prints the 3
> 
>         exp.
> 
>                 bits.
> 
>             Cisco must have combined RFC3032 [2.1. Encoding the Label
>             Stack] into
>             one value.
> 
> 
>         still not sure what you refer to, and why you think the debug
>         discussed
>         shows the 4-bit Exp+S value rather than the 3-bit Exp only?
> 
> 
>     If I may, MPLS Fundamentals refers to the stack on Fig 2-1 as
>     Label/EXP/BoS/TTL. It then breaks this on Example 3-8 with {label
>     EXP TTL}. All things held constant; label at 20, TTL at 8, then EXP
>     must be 3+1.
> 
>     Roy
> 
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> 
> 
> Reading too much into it. It's just not showing the stack bit. The 
> output is for information. You don't need to know the stack bit, its the 
> only label. And if there were more than one, then it would show all labels.

Right on, too much reading. I didn't take the text as it is. Oli was on 
spot. Cheers!

Roy