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Re: Vulnerbilities of Interconnection

  • From: Stephen J. Wilcox
  • Date: Fri Sep 13 04:44:45 2002


On Thu, 12 Sep 2002, John M. Brown wrote:

> 
> Yet, it is reasonable that people expect x % of their traffic to
> use IX's.  If those IX"s are gone then they will need to find another
> path, and may need to upgrade alternate paths.
> 
> I guess the question is.
> 
> At what point does one build redundancy into the network. 

No, it doesnt necessarily use IX's, in the event of there being no peered path
across an IX traffic will flow from the originator to their upstream
"tier1" over a private transit link, then that "tier1" will peer with the
destination's upstream "tier1" over a private fat pipe then that will go to the
destination via their transit private link.

I'm only aware of a few providers who transit across IX's and I think the
consensus is that its a bad thing so it tends to be just small people for whom
the cost of the private link is relatively high.

I suspect the catch would be that in the event of major switching nodes being
taken out there would be considerable congestion on the transit links and most
likely on the private peering of the tier1's also.

> I suspect its a balancing act between reducancy, survival (network)
> and costs vs revenues.

I imagine in todays capitalist world its not so much balanced as weighted
heavily in economics and how best to not spend the cash!

> not sure I'd call it a "poor job"  for not planning all possible
> failure modes, or for not having links in place for them.

Well the trouble is in the real world we cant have the budgets we'd like to
implement our plans and end up compromising.. theres the catch.


Note however that the email below is a mix of IX's and data centres, and the two
are not the same. Here we are discussing IX's.

I think its a different matter if we lose a data centre as you then risk losing
the aforementioned private transit/peer links which will probably go through
that location. Then you'd see more disruption.

With that in mind consider last years outage at 60 Hudson.. the main areas it
affected was switching IP/calls in New York (but that was hosed anyway) and
probably the next area was Europe with lots of the East Coast cable landings
going through their, I know most people I spoke to were seeing congestion and
outages going to US locations. But hey, things still worked!

Steve

> 
> 
> On Wed, Sep 11, 2002 at 06:00:40PM +0200, Kurt Erik Lindqvist wrote:
> > 
> > 
> > On fredag, sep 6, 2002, at 21:57 Europe/Stockholm, Tim Thorne wrote:
> > 
> > > OK, what if 60 Hudson, 25 Broadway, LinX and AmsIX were all put out of
> > > commission?
> > 
> > To some extent - nothing for the above...if design right. The major 
> > networks should have designed their networks to route around this. If 
> > not - they have done a poor job. For others, the exchange points should 
> > be a way merely to off-load their transit connections.
> > 
> > However - there is a point in what you are saying, from a national 
> > point of view - the exchange points should independently take care of 
> > traffic in the case a nation is isolated. But I don't think any of the 
> > above are designed for that in the first place...
> > 
> > 
> > - kurtis -
> > 
> 





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