The MPLS WG Archive

[Steve Blake <slblake@torrentnet.com>]

Andre N. Fredette <fredette@photonex.com> wrote:

> LDP, and therefore CR-LDP, does not provide an LSP MTU discovery 
> mechanism.  The thinking (perhaps flawed) was that:
> 
> (a) Fragmentation is not usually an issue in the core of the network due to 
> the large MTUs on typical interfaces, and
> 
> (b) If it is an issue in a particular domain, the MTU can be configured on 
> the MPLS edge routers.  Note, I am aware that this is somewhat problematic 
> because the MTU is not necessarily related to the local router, but is the 
> minimum of all MTUs in the MPLS domain.
> 
> LDP and CR-LDPs are due to be released as RFCs in the next couple of weeks 
> and I don't think this is serious enough to hold them back.
> 
> I'd be happy to write an extension to LDP for MTU discovery if people think 
> it is necessary.

Those with long memories may remember that ARIS could convey the LSP path
MTU to the ingress LSR, because of the particular way that ARIS worked.
How this feature missed being added to LDP (at least as an option) is a
mystery to me.


Regards,

=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
Steven L. Blake               <steven.blake@ericsson.com>
Ericsson IP Infrastructure                  (919)472-9913