Subject: (Reply)Installing label for forwarding/switching use

From: [email-masked]
Date: Mon, 16 Aug 1999 13:02:18 +0800

Jim,

I feel that for "Send_Label" procedure
	SL.3 Install Label for forwarding/switchng use.
be changed to
	SL.3 Install Label for forwarding use when using Independent control
	 (Downstream unsolicited or DoD) only if there is no downstream mapping for FEC available
Again emphasising,
This step must be used only if the LSR
	1.Is using Independent control
	2.Doesn't have a free label mapping for FEC from downstreams
	3.Is a Transit LSR
This will make sure that packets arriving on the incomplete LSP
from upstreams will be forwarded.

Any comments? Any consequences of doing this?

cheers,
chetan

You wrote:
-----------------------------------------------------------------------------------------------------------------------------------------
While re-reading LDP-05 (I needed to fall asleep) I noticed something that 
slightly confused me.

In "LRq.12 Perform LSR Label Use procedure" step 1 says:

	Install label sent to MsgSource and label from Next
	Hop (if LSR is not egress) for forwarding/switching
	use.

But back in LRp.9, step 3 (Independent Control or Ordered Control) we executed
"Send_Label" which says:

	SL.3 Install Label for forwarding/switchng use.

Now I realize that SL.3 refers to installing an "originating" label that
the peer will use to send traffic to the LSR, and that LRq.12 is installing
both the "originating" and "terminating" labels (creating a switch path).

If we do only what's said in SL.3, we're missing the "terminating" part of a 
switch path. If we do both, we have a smaller window in which we are missing
a "terminating" part of a switch path.  If we do only what is in LRq.12, 
there is the possibility that the peer will start using the mapping we just 
sent, before we can install the switch path.

Am I missing something?
Jim

-- 
James R. Leu        |  University of Wisconsin - Madison
Network Engineer    |  Division of Information Technology
[email-masked]  |  Network Engineering Technology

---

From: "James R. Leu" <[email-masked]>
Date: Mon, 16 Aug 1999 03:23:32 -0500

See comments within:

> 	 (Downstream unsolicited or DoD) only if there is no downstream mapping for FEC available

I think we could/should take this one step further.  A the time a Label Mapping
is being given out the LSR already knows if a downstream mapping is availble.  
If it is can't it just go ahead and install the "cross connect" for this new 
mapping now?

> from upstreams will be forwarded.

I agree that special care needs to be taken for cases when a downstream mapping
is not availble.

Jim