Subject: RE: Last call on LSP Ping

From: Shahram Davari <[email-masked]>
Date: Mon, 9 Dec 2002 10:34:32 -0800

> You have not cited any technical reason for avoiding 127/8.  You have
> cited documents and tried to manipulate the interpretation to claim
> that any use of 127/8 is forbidden.

Isn't compliance to RFCs a legitimate technical reason? It is like not stopping at red light, and asking for a reason even though the traffic law says "A car SHOULD never pass a red light". SHOULD is there because ambulances could pass.

> 
> What alternate did you propose that would have the characteristics of
> never being routeable and therefore never have to potential to be
> delivered by IP rather than the intended MPLS LSP(s)?  I must have
> missed that proposal.

First of all I did propose using the egress IP address and setting the
TTL=1 in the IP header. This makes sure that the LSP-ping packet will
not get forwarded after the MPLS labels are poped. Secondly, it is
not my draft, those who have written it should find alternate methods.

> 
> Obstruction means getting in the way (of some sort of progress) for no
> other reason than to get in the way.

And how did you reach to this conclusion? (imaginations I guess !)

> 
> If you are making a point to steer us toward a better solution, that
> certainly hasn't been clear.

Ok., let me make it clear: I want LSP-ping to be improved.

> If you think some entirely alternate
> solution (Y.1711) is a better solution, then you should work on that
> solution and stay out of this discussion.
> It is like disrupting the
> ISIS WG with a constant "OSPF is better" mantra or insisting that ISIS
> do everything the OSPF way (or doing the same in the OSPF WG).

Again imaginations........ This has nothing to do with Y.1711. In fact
LSP-ping can never do the job of Y.1711, since it is more complex and
very slow. I want LSP-ping for diagnostics purpose. So I don't benefit
from stopping it. All I want is a reasonable draft, that does not behave
different in different networks.

-Shahram

> Curtis

---

From: Curtis Villamizar <[email-masked]>
Date: Mon, 09 Dec 2002 13:57:44 -0500

In message <[email-masked]
>, Shahram Davari writes:
> Isn't compliance to RFCs a legitimate technical reason?

You don't have a leg to stand on with this one.  I've already stated
why use of 127/8 to deliver packets to the loopback is the intended
purpose of 127/8 and therefore no RFC is in violation.

> not get forwarded after the MPLS labels are poped.

Glad to see this change to a technical discussion.  Took a while.

This proposal has two flaws, 1) when the label gets POPed and the
egress isn't the router you thought it should be the response is an
ICMP TTL expired, 2) no way to handle ECMP is proposed.

Please indicate how you would handle ECMP.

> Secondly, it is

They have proposed something that will work.  You have now made a
counterproposal.  You need to justify on technical grounds why not to
use their proposal, why yours will work, and why yours is better.

> Ok., let me make it clear: I want LSP-ping to be improved.

Great.  So drop the RFC1700 nonsense and lets move on.

Curtis

---

From: Kireeti Kompella <[email-masked]>
Date: Wed, 11 Dec 2002 03:12:53 -0800 (PST)

> Glad to see this change to a technical discussion.  Took a while.

:-)

> ICMP TTL expired, 2) no way to handle ECMP is proposed.

Big flaw: there ain't no such thing as *the* egress router.  Some
router "at the other end of the network" announces a label mapping
for 9/8, and this mapping makes its way to me.  How do I know who
the egress router is?  Moreover, there could be many routers announcing
9/8 ...

Kireeti.

PS: IP TTL = 1 is already in the draft.

---

From: Curtis Villamizar <[email-masked]>
Date: Wed, 11 Dec 2002 13:29:24 -0500

In message <[email-masked]>, Kireeti Kompella 
> the egress router is?  Moreover, there could be many routers announcing

For ping mode that far end router is the egress.  TTL is 255 on top
label, 1 on all other labels.  Something POPs out at the end of the
LSP.

For traceroute mode TTL starts as 1 on top.  The first packet doesn't
go far but identifies itself and returns a mapping.  TTL is
incremented, next router identifies itself and returns a mapping.
Eventually the egress is reached.

BTW- the draft only describes ping mode operation - traceroute mode is
inadequately described except for those for whom "analogous to IP
traceroute" is plenty.  Works for me, but that doesn't count.  (Unless
of course, I interpreted your intentions incorrectly.)

So there is an egress but my statement is still not entirely correct
as stated.  I should have pointed out that a packet can emerge
anywhere at the egress or at an intermediate hop when TTL expired.

> PS: IP TTL = 1 is already in the draft.

IP TTL=1 and dest is in 127/8.  No router should forward that except
for forwarding to the local loopback, exactly as specified in RFC1812.

Curtis