MPLS Header details

[TangoAlfa]

Hi All

Below is MPLS header I draw which might help others to understand well.

Now here who can explain "the unreserved value 16 to 19" 

ref: diagram attached

[M02@rt37]

Hello @TangoAlfa,

These bits are used for experimental purposes or for carrying additional information beyond the standard MPLS functions.

The unreserved field provides flexibility for network operators or researchers to experiment with new features or protocols within the MPLS network. It allows them to define their own usage for these bits, as long as it does not conflict with the standardized MPLS functionality.

Typically, network operators and equipment manufacturers agree upon specific uses or interpretations for these unreserved bits within their networks or equipment. However, the exact interpretation and usage of these bits can vary between different network implementations.

THey are not standardized and may not be universally recognized or supported by all MPLS devices or implementations.

[Harold Ritter]

Hi @TangoAlfa ,

You are confusing bit positions with label values. When RFC3032 says that "values 4-15 are reserved", it refers to the label values itself, rather than the bit positions.

According to RFC3032, label values 0 to 3 have specific purposes. Label values 4 to 15 are reserved. This means that label values 16 to 1048576 (2^20) are unreserved and therefore usable.

https://www.rfc-editor.org/rfc/rfc3032.html

Regards,

[TangoAlfa]

Hi @Harold Ritter 

Thanks for your response. Yes you are right that in this diagram making confusion on bit positions with label values. Now is this below would be right self explanatory picture? or I have to change something?

[Harold Ritter]

Hi @TangoAlfa ,

I think this new diagram makes it even more confusing. There is not concept of bit position in the label field. The label field is a 20 bit field containing label values (from 0 to 1048576).

Regards,

[TangoAlfa]

Hi @Harold Ritter 

Now is this modification made clarity?

[Harold Ritter]

Hi @TangoAlfa ,

I still see in the diagram the confusion of bit position (20 bit positions depicted at the top) and label values at the bottom. For instance label value 0 pointing to bit position 0, label value 1 pointing to bit position 1, etc.

Regards,

[TangoAlfa]

Hi @Harold Ritter. Yes the same way I also thought it should 1 to 20 but in RFC mention the same way what I mention in diagram. ref: mention below.

[Harold Ritter]

Hi @TangoAlfa ,

What I mean is that you have a direct line between the label value 0 at the bottom and bit position 0 in the label and so on. This will probably lead people looking at this document to think there is a direct correlation between the two.

Regards,

[TangoAlfa]

Hi @Harold Ritter  Thanks for your long support. You are very much right that it might create confusion. considering the below is modified. please have a review.

[Harold Ritter · Accepted solution]

Much clearer @TangoAlfa . Great work