The MPLS WG Archive

[bin <binzhou@site.uottawa.ca>]

Hi,

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?

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?

Regards,
Bin