The MPLS WG Archive

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

Hong Liao wrote:
> 
> I have two questions for section 4.7.4.
> 
> 1) if the three tests mentioned in this section fail, should router send a
> patherr msg with the error code 'routing problem' or error code 'policy
> control failure'?
>  I think it should be the error code 'routing problem'.

That's what section 4.7.4 says:

	For a link to be acceptable, all three tests MUST pass.  If
	the test fails, the node SHOULD send a PathErr message with
	an error code of "Routing Problem" and an error value of
	"no route available toward destination".

> 2)  In the spec and this section, it was not clear that what kind of value
> should be put in the 'link-attr', 'exclude-any',
> 'include-any','include-any' in order to trigger the router to generate the
> patherr msg above.  I would like to know how to set the value in this
> field, and give me an example on how to create this scenario with what kind
> of value in these fields?

Every link has attributes configured.  Other routers learn them through 
routing.

If an ingress node cares about the attributes, it will generate an ERO 
that sends the LSP over links that match the required criteria.  It will 
also set the resource affinities in the session attributes so that 
transit nodes can validate the locally-configured attributes against 
those requirements.

When choosing an egress interface, a router must choose one such that 
none of the "exclude-any" bits correspond with the link's configured 
bits, at least one of the "include-any" bits corresponds with the link's 
configured bits, and all of the "include-all" bits correspond with the 
link's configured bits.

Validating a link (fetched from an ERO or from routing) against an 
interface's attribute bits is easy.  Using these bits as part of the 
criterial for choosing a link may be more complicated, depending on what 
kind of routing features your box supports.

-- David