[c-nsp] debug mpls packet

[Hobbs]

On Tue, Nov 17, 2009 at 8:38 PM, roy <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.