Re: [mpls] entropy label indicator label indraft-kompella-mpls-entropy-label

[Curtis Villamizar <[e-mail]>]

In message <[e-mail]>
Shane Amante writes:
>  
>  
> Lucy,
>  
> On Jul 27, 2010, at 17:06 GMT+02:00, Yong Lucy wrote:
> > Hi John,
> > I don=92t get it. If egress LSR asks ingress LSR to place ELI on the =
> stack, the ingress can insert a unique ELI label on the stack followed =
> by entropy label. When packet arrives to egress LSR, the LSR will find =
> ELI on the stack. Why is it important for egress LSP to allocate a value =
> for ELI instead of using standardized value?
>  
> I think John already answered this question, but I'll give it a try, as =
> well.  It's really a design choice on the part of the co-authors, in an =
> attempt to avoid asking the MPLS WG to allocate a reserved label from =
> the very scarce reserved label space.  I would note that there are only =
> 8 reserved MPLS label values that are currently unassigned:
> =
> http://www.iana.org/assignments/mpls-label-values/mpls-label-values.xhtml
>  
> So, if we believe it's "sound engineering" to use an ELI instead of a =
> reserved label -- certainly a judgement call -- then, I believe, we =
> should NOT request a reserved label in order that future applications =
> that have a legitimate use (or, said differently, may not be able to =
> function properly without a reserved label value) have an ability to =
> acquire one.
>  
> -shane


Whether it is reserved or not, the ingress needs to verify that the
egress understands it so there is little additional change having the
egress provide its own reserved value.  This avoids using a scarse
resource for no good reason.

Curtis