Question on peering strategies

Baldur Norddahl baldur.norddahl at gmail.com
Mon May 16 20:29:24 UTC 2016


On 16 May 2016 at 22:06, Reza Motamedi <motamedi at cs.uoregon.edu> wrote:

> With respect to my second question, I was asking if is practical/reasonable
> to keep both the connection types to same network (say AS-b) at the same
> time, i.e., connect privately over a cross-connect and keep the public
> connection over the IX.
>


Router ports are expensive, so even if cross connects were free, you would
still use the public switch fabric until you reach a traffic level that
justifies a direct connection. The point of having a IX switch is that you
can connect to many others with just one single router port.

When you have the direct cross connect, you would not usually use the IX
switch in parallel for that AS. With the cross connect you have dedicated
bandwidth to the AS and you would want to reserve the IX switch port for
traffic to the remaining networks that you do not yet have a cross connect
to.

The cross connect is not a very good redundancy setup with regard to the IX
switch. Both usually go to the same router and share the same single point
of failure (your router is a single point of failure and the peer router is
a single point of failure). A cross connect is usual very reliable. You
would plan for your router to be down or the peer router to be down, and
have a backup path through some entirely geographic separate location.

In many cases your generic IP transit service is good enough backup. Your
direct peering is an optimization and if that is down, you go back to the
transit service.

Of course everyone are playing their own game and you might see anything
happening in the real world despite the above.

Regards,

Baldur


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