Subject: Loop detection in RFC3036

From: shen jing <[email-masked]>
Date: Fri, 02 Mar 2001 22:06:00 +0800

if it has been asked before , execuse for my stupid question please.

I'm reading rfc3036  to learn some basics of LSP building.

while in 2.8.3 , it is said   --

  "Note that in a network where only non-merge capable LSRs are present,

   Path Vectors are passed downstream from ingress to egress, and are
   not passed upstream.  Even when merge is supported, Path Vectors need

   not be passed upstream along an LSP which is known to reach the
   egress.  When an LSR experiences a change of next hop, it need pass
   Path Vectors upstream only when it cannot tell from the hop count
   that the change of next hop does not result in a loop. "

As it said MPLS just support downstream determined lable distribution,
as I think
it means any LDP packet should be first transmitted from downstream to
upstream. why here states  " Path Vectors are passed downstreams from
 ingress to egree and are not passwd upstream" ?  why is it related to
label merge ?

James shen

---

From: shen jing <[email-masked]>
Date: Mon, 05 Mar 2001 19:24:48 +0800

Thank you.

But,  why it states " Path Vectors are passed downstreams from
 ingress to egree and are not passwd upstream"?
Is that only means the  lable request  LDP message ?

> The loop detection depends on hop count, but hop count is not valid in

> the presence of label merging.
>

>
> On Fri, Mar 02, 2001 at 10:06:00PM +0800, shen jing wrote: