Dual Homed BGP

So for us, we have quite a number of on-net caches, and the fill for
them (or origin pull) is typically done via peering.

Of the 85% we consider "peering traffic", around one-third of that is
traffic from our on-net caches.


From the perspective of someone just starting out being dual homed, this will be very different. You are not going to get 7 transits and you are not going to be able to peer 85% of the traffic. That is why I advocate that it is better to buy transit from a middle tier company. Instead of getting a connection to just one so called global carrier, you get a package deal with connection to all of them and 85% peering one step removed. Plus many of the companies that the middle tier has a peering with, is something the tier 1 companies would refuse to peer (exception Hurricane Electric).

Also while your company may not need dual connections to each transit, the situation is completely different from the perspective of a small dual homed customer of yours. That is a lot of paths that are lost if this customer where to experience a disruption to the connection to your network.

This is especially true if there is an unbalance between the two chosen transit providers. Say the other provider is Cogent, which are famous for refusing to peer. That means that all those peers, unless they have a Cogent contract, they will need to find an indirect path to replace your peering.

Of course I may also recommend to simply set your expectations modestly. Dual homing will get you redundancy but unless you line up all your ducks correctly, you should expect some brownouts in the case of a link failure. Simply tell the boss, that unless he wants to pay at least double in every way, there will be expected downtime in the order of 5 minuttes in the case of a link failure.



“you are not going to be able to peer 85% of the traffic”

It depends. If you are an eyeball ISP and you join one of the major IXes, you’ll be near 85%.

Reading all the arguments one could generalize that choosing default/partial routes (instead of full feed) one is basically outsourcing all the control, convergence speed, security, etc… to upstream providers.


We are seeing about 79% currently that is with one of our new Akamai PNIs in CHI and we peer at most major IXs across the US.

Top 5 peers Netflix, Google, Akamai, Amazon and EdgeCast. (In order)

I just looked at the stats again we are actually at about 82%.


My numbers for the last 7 days:

NL-IX 2107 22%
STHIX 412 4%
Cache (netflix+akamai) 3070 32%
Telia 1118 12%
Cogent 258 3%
HE 2490 26%
= 9455 100%

The numbers being average (not peak or 95 percentile) inbound. Outbound is irrelevant for us.

I suppose that if you consider Hurricane Electric as a poor mans peering service, we would be up there as well.

This is for volumen however. Almost everything breaks if we loose the transits. It is not like you are 80% ok.



Completely agreed, as I highlighted in my post at as a response to Adam’s original query. Mark.

And this is an important point, as even if many of your on-net caches
would origin via a peering session with its owner, some origins are only
available via transit.