The MPLS WG Archive

[David Charlap <david.charlap@marconi.com>]

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