How many Tunnels [Re: Re: pTLA request]

[Simon Leinen]

Yiorgos Adamopoulos <Y.Adamopoulos@noc.ntua.gr> writes:
> I think they should be assigned the pTLA.  But, just like in our
> case (GRNET, 3FFE:2D00::), they should open more tunnels the just
> with SWITCH and SURFNET.

Yiorgos raised an interesting point here: How many tunnels should
pTLA/transit sites have to other sites.

There seems to be a tendency to build a full mesh between backbone
sites.  I think this is very undesirable, because it makes the 6bone
less realistic as a prototype for routing on a global IPv6 network:

* The diameter of the network is kept artificially small.
* Abundance of tunnels introduces an unrealistic level of redundancy,
  which reduces the pressure on sites to fix routing problems to a
  given neighbor.
* Some "single hops" over the 6bone represent many many hops over the
  IPv4 Internet, sometimes including congested subpaths.  Those
  "shortcuts" attract transit traffic that could use a different path
  consisting of several hops between 6bone neighbors that are actually
  close to each other in the IPv4 Internet topology.  This has a bad
  impact on global 6bone connectivity.

Personally I would prefer the 6bone topology to resemble the IPv4
topology closer than is the case today.  SWITCH's policy as a pTLA has
been to set up tunnels to other networks that we either peer with or
that we have good connectivity with.  In particular, we try to avoid
the "shortcuts" I mentioned above, as well as links that regularly
experience congestion.

Is there any opinion on mentioning these problems in the "6bone
Routing Practice" I-D, not as a recommendation but as a problem
statement?

Personally, I find BME-FSZ's connectivity quite sufficient - SURFNET
and SWITCH are both connected to Hungary over few hops the TEN-34
research backbone.
-- 
Simon Leinen				             simon@switch.ch
SWITCH				      http://www.switch.ch/lan/ipv6/