The MPLS WG Archive

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

bin wrote:
> 
> Question: What the exact ERO in PathErr is?
> 
> In RFC3209,
>    "If there is no first subobject, the message is also in error and
>    the system SHOULD return a "Bad EXPLICIT_ROUTE object" error."
> 
>    "A node which encounters an unrecognized subobject during its normal
>    ERO processing sends a PathErr with the error code "Routing Error" and
>    error value of "Bad Explicit Route Object" toward the sender.  The
>    EXPLICIT_ROUTE object is included, truncated (on the left) to the
>    offending subobject.  The presence of an unrecognized subobject which
>    is not encountered in a node's ERO processing SHOULD be ignored.  It
>    is passed forward along with the rest of the remaining ERO stack."
> 
> I don't understand "truncated (on the left) to the offending subobject".
> Which subobject is the offending subject? What's the meaning of on the
> left?

The offending subobject is the one that is unrecognized.

"on the left" means everything prior to that object.

> In my understanding, explicit route object in Path State is not the
> original ERO sent by Sender, and the nodes along the route to this node
> are all removed from the ERO. The node should return only the
> unrecognized first subobject to the sender. Right?

It should return the entire ERO, starting from the unrecognized object.

-- David