Cell Relay Archive

[ag@eden-gardens.ee.duke.edu (Anoop Ghanwani)]

Nafez Aboulibda (nafez@igdv.fh-darmstadt.de) wrote:

: In MPLS-arch-00.txt page 16 chapter 2.15.1 loop preventing,
: < If R is not in the LSR id list, R will start a diffusion computation >
: the aim of this
: procedure to prune the tree up stream of a particular node.

: what I cannot understand is, if a node is not included in the upstream
: lsr id consequently
: there is no looping.
: Then why should the diffusion computation be done.

If R appears in the list, the path definitely has a loop and we don't
want to use it.  If R doesn't appear in the list, we know that there
isn't a loop in the partial path only (the portion of the path
originating at R).  The path is useful only if it is determined that it
is completely loop free.  The diffusion algorithm checks to see if any
of the routers in the new path originating _from_ R happen to appear in 
the portion of the paths upstream of R.

-Anoop