MPLS Label question

Can someone explain to me why these are locally significant and maybe give me an example of why it was designed this instead of making them global to match the originating route or whatever else you may tag?

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kpjungle

gojericho0 wrote:

Can someone explain to me why these are locally significant and maybe give me an example of why it was designed this instead of making them global to match the originating route or whatever else you may tag?

I think its because the LSR's send these to each other (to peers), so in any given network you might have the same label for two networks. I think the overhead in synchronizing the labels would be too much in a large network, because basically you would create a "link state" kind of scenario, where all routers would need to know the full topology.

gojericho0

The other reason I was thinking is that it already relies on the underlying routing protocol and CEF. There for there really is no need for it to be globally significant if the path is already there.

kpjungle

gojericho0 wrote:

The other reason I was thinking is that it already relies on the underlying routing protocol and CEF. There for there really is no need for it to be globally significant if the path is already there.

Yeah, and as far as I know, the path to a given destination network is chosen by the IGP (normal metric), so a path is "known" in advance. But I do wonder if that makes load balancing possible?