The MPLS WG Archive

[Yuan Gu <Yuan.Gu@usa.alcatel.com>]

David:

Could you explain detailly what's the diffrent between TSPEC MTU and ASPEC
MTU? And what's the diffrent between LSP requested MTU and Path MTU?

Best Regards!
Yuan

David Charlap wrote:

> Yuan Gu wrote:
> >
> > According to section 2.6 of draft-ietf-mpls-rsvp-lsp-tunnel-08.txt
> > and RFC2210, MTU should be getten from ASPEC if Integrated Services
> > object is presented in Path msg.
>
> No.  ADSPEC is used by the transit routers to calculate the MTU along
> the path.  It says nothing about what else should be done with this
> value.
>
> The MTU requested for the LSP is in the TSPEC object.
>
> > On the other hand, ASPEC is an OPTIONAL object according to section
> > 3.1 of draft-ietf-mpls-rsvp-lsp-tunnel-08.txt.
> >
> > My quesions are:
> >
> > 1. In the case of Integrated Service Tspec is presented in Path
> > msg, is ASPEC still OPTIONAL?
>
> Yes.  The choice of service (controlled-load, guaranteed, or Null) is
> determined by what services are present in the Adspec object.  If it is
> missing, then it is up to the implementation of the egress router to
> decide.
>
> > 2. If the answer of above question is YES, how do we manage the
> > Path MTU if ASPEC is not presented in Path msg?
>
> In this case, path MTU is not computed.  The MTU requested in the TSPEC
> should be used.  If it is no good, then a router somewhere will reject
> the Resv with an admission control error.
>
> -- David

begin:vcard 
n:Gu;Yuan
tel;work:703-679-6474
x-mozilla-html:FALSE
org:Alcatel USA;CID
adr:;;15036 Conference Center Drive;Chantilly;VA;20151;
version:2.1
email;internet:Yuan.Gu@usa.alcatel.com
title:Software Engineer
fn:Yuan Gu
end:vcard