The MPLS WG Archive

[David Charlap <David.Charlap@marconi.com>]

"Bakshi, Sanjay" wrote:
> 
> Is it ok for an LDP implementation to only support a sub-set of
> 20bit label space?
> RFC3036 does not talk about it but do the LDP implementations
> available from various vendors allow such a configuration?
> thanks

With respect to the labels that you generate and send to your upstream
peer (via Label Mapping messages), you can choose to restrict yourself
to a subset if you like.

With respect to the labels you receive, I think you have to accept
whatever values you get.  The problem is that you must somehow tell the
downstream router what range is acceptible, so that it will choose a
label from that range.

If you have an ATM or Frame Relay interface, you can specify the
acceptible range using the ATM Session Parameters or FR Session
Parameters TLV.  Unfortunately, there doesn't appear to be any TLV for
signaling label range on generic interfaces.

This means that if you don't support the entire 20-bit range on a
generic interface, you will have to come up with some non-standard way
of getting the downstream router to only generate labels in your range.

-- David