Subject: RE: How to move forward in the HAO & ingress filter discussion

From: "Hesham Soliman (ERA)" <[email-masked]>
Date: Tue, 15 Jan 2002 13:49:00 +0100

Francis

  >    I have a proposal. But first, let me make some observations:
  >    
  >    - Most people do seem to agree that HAO reflection is an
  >       issue that needs to be dealt with somehow.
  >    
  > => we have to deal with it but we don't need a stronger solution
  > than today ingress filtering which is a BCP, i.e. something like
  > a SHOULD.

=> But how can that be true ?? Today's ingress filtering 
is clearly insufficient for HAO issues. Or perhaps you
mean we need a solution that doesn't have to be mandated
(SHOULD instead of MUST) ? If so, this is too early to discuss, 
we don't have an agreement on a solution yet. 

I haven't heard anyone answering my question as to why
reverse tunnelling by the MN thru the HA is so much 
worse than triangular routing, that we need to develop 
something new to fix the HAO problem 'only sometimes'.

Hesham

--------------------------------------------------------------------
IETF IPng Working Group Mailing List
IPng Home Page:                      http://playground.sun.com/ipng
FTP archive:                      ftp://playground.sun.com/pub/ipng
Direct all administrative requests to [email-masked]
--------------------------------------------------------------------

--------------------------------------------------------------------
IETF IPng Working Group Mailing List
IPng Home Page:                      http://playground.sun.com/ipng
FTP archive:                      ftp://playground.sun.com/pub/ipng
Direct all administrative requests to [email-masked]
--------------------------------------------------------------------

---

From: Francis Dupont <[email-masked]>
Date: Tue, 15 Jan 2002 16:04:22 +0100

In your previous mail you wrote:

   > => d(bidir tunnel) = 2 * d(MN,HA) + 2 * d(HA,CN)
   >    d(triangular) = d(MN,HA) + d(HA,CN) + d(MN,CN)
   >    d(optimization) = 2 * d(MN,CN)
   > and we always have d(MN,CN) <= d(MN,HA) + d(HA,CN)
   > so d(optimization) <= d(triangular) <= d(bidir tunnel)
   > and even stronger 2 * d(triangular) = d(optimization) + d(bidir tunnel)
   > i.e. in my poor English the cost/performance of triangular routing
   > is at the middle of bidirectional tunneling and routing optimization.
   
   In theory, yes.  But the question is, does it really make that much of a 
   difference as long as at least one way is "unoptimized"?
   
=> the same difference than when both ways are unoptimized or optimized.
Difference in distance is the same, difference in byte overhead too.
This is true for all points with one exception: protocol complexity
because triangular routing has roughly the same complexity than
bidirectional tunneling.

   Practice?  I don't think there's much difference in bidir
   tunnel/triangular routing; I doubt e.g. TCP would be able to get much
   better performance from triangular than from bi-dir (and there are goals
   like hiding your origins that triangular cannot solve).
   
=> I can't see how TCP is involved. I believe your argument is different:
if the traffic is very asymmetrical (more on one way than on the other),
you prefer to have it on the optimized way...
I am afraid the real argument against the triangular routing is this
discussion itself because the main triangular routing advantage comes
from the (future) fact that HAO is supported by every IPv6 nodes.
With enough FUD this shall never become true and the advantage shall vanish...
I'd like to get the opinion of IPv6 implementors (if they don't filter out
this boring discussion) about HAO (for it, against it, will/won't implement
it, will/won't enable it by default, etc).

Regards

[email-masked]