Re: FW: Questions about tunneltrace

[Yakov Rekhter <yakov@juniper.net>]

Ron,

> Eric,
> 
> Thanks for your comments. See reply below....
> 
> 
> > -----Original Message-----
> > From: owner-tun-trace@ops.ietf.org
> > [mailto:owner-tun-trace@ops.ietf.org]On Behalf Of Eric Rosen
> > Sent: Tuesday, February 27, 2001 12:16 PM
> > To: tun-trace@ops.ietf.org
> > Subject: Questions about tunneltrace
> >
> >
> > From draft-bonica-tunneltrace-01:
> >
> >       9) When the tunneling technology isolates the user-plane from the
> >       control-plane, do not rely upon the control plane to discover the
> >       path.
> >
> > From draft-bonica-tunproto-00:
> >
> >    D2 receives the TraceProbe, exercises access control, and determines
> >    that it is the hop's head end device. D2 consults its FIB and
> >    determines that an IP-in-IP tunnel supports H1.
> >
> > I think this is saying that  D2 must consult its control
> > structures in order
> > to determine whether the "hop" H1  is a tunnel or not.  Doesn't
> > this violate
> > the requirement above?  In the  event of failures, D2's
> > "determination" that
> > data packets are supposed to be traveling through a tunnel
> > doesn't necessar-
> > ily mean that data packets would actually travel through that tunnel.
> 
> You have a point! Strictly speaking, I am not tracing through the
> user-plane, but bouncing back and forth between the user-plane and the
> control-plane. I have no choice but to do so.

Well, you do have a choice - use the mechanism described in
draft-bonica-icmp-mpls-02.txt. This mechanisms does trace through the
user-plane (aka data-plane).

> In order to remain in the user-plane, I would have to send a series of
> datagrams from the head-end of the top-level tunnel to the tail-end of the
> top level tunnel, causing the each datagram to self destruct at a different
> point along the path. Upon destruction, each datagram would elicit some
> feedback that would a) include tunnel details and b) be sent all the way
> back to the head-end of the top-level path.
> 
> Isn't that the kind of layer violation that we are trying to avoid?

As "we are trying to avoid" layer violation, we need to keep in
mind the problem that we are trying to solve. So, what is exactly
the problem that we are trying to solve ?

Yakov.