Re: [mpls] Last Call: <draft-ietf-mpls-in-udp-04.txt> (Encapsulating MPLS in UDP) to Proposed Standard

[Curtis Villamizar <[e-mail]>]

In message <[e-mail]>
Mark Tinka writes:
 
> On Monday, January 13, 2014 10:04:13 PM Curtis Villamizar
> wrote:
>  
> > Perhaps someone needs to explain to you what a FEC is and
> > how MPLS traffic is routed in most LDP networks.
>  
> Thanks for the 101, Curtis, but I think I'm doing alright
> :-).
>  
> Again, my input is rooted in operational situations that
> I've experienced, present and past (I'm neither a vendor nor
> a software developer):
>  
> J's implementation of LDP treats LDP much like a routing
> protocol (unlike C's implementation).
>  
> In such cases, LDP-derived routing has a discrete routing
> table different from the global routing table. Under certain
> conditions (design or code), there could be a mis-alignment
> between what LDP thinks is the best path vs. what the IGP
> thinks is the best path.

You need specific configuration to create the mis-alignment.  You can
also override an IP routing protocol with static routes.

> A knob exists within J's LDP implementation to synchronize
> LDP and the IGP (i.e., the LDP and IGP metric is always the
> same). Such a knob does not exist (AFAIK) with C because C
> don't treat LDP like a routing protocol. Without this LDP
> knob enabled in J's implementation (which is the default
> case), LDP routes always retain a metric of 1, regardless of
> the route and regardless of what the IGP metric is.

Both ISIS and OSPF have a TE metric and an IGP metric.  The default
AFAIK was to use the IGP metric for LDP, though if as you say J
defaults to 1 and requires you to configure a separate LDP metric.  If
so, then the LDP hop count TLV would not match the IGP cost.  Not a
problem but an odd choice for default value on J's part.

> I concede that this case may not be the norm when taking all
> vendor implementations into account, but then again, my
> experience is restricted to C and J.
>  
> Mark.

I'm not sure how any of this discussion changes anything wrt
draft-ietf-mpls-in-udp.

Is there relevance to draft-ietf-mpls-in-udp that I am missing?

Curtis