[j-nsp] MPLS label stack limits on MX line cards

[Saku Ytti]

On (2015-06-01 21:04 +0300), Nitzan Tzelniker wrote:

Hey,

> The default limit is 3 but you can change it to 5
> http://www.juniper.net/techpubs/en_US/junos14.2/topics/task/configuration/interfaces-mpls-maximum-labels.html
>  I heard something about increasing this limit probably for segment routing
> (but it was two years ago )
> 
> BTW
> 
> I didn't find a reference how small platforms that support only 3 labels
> will be able to do traffic engineering in segment routing (ACX,QFX,ME3600

For normal forwarding and even for FRR use cases your label depth would be
modest. But as you say, for TE you would have pathological cases where stack
will be much deeper.

I'm not convinced this is a hard problem. I don't believe the stack depth
limit are inherently about byte count, but more about indirection count.  And
if we think of TE ERO as single indirection, rather than chain of hops, then
we might be able to impose multiple labels as single rewrite at one go (at
cost of inflating next-hop count)
If platform can do IPV6 tunneling, it can impose >40 bytes, it does not seem
far fetched that you could impose 10 labels instead, provided they can be
returned in single lookup/indirection.

-- 
  ++ytti