[sdnog] Quad9 node in Sudan :-)

[Nishal Goburdhan]

On 10 Sep 2018, at 12:11, Reham Abdalla Ahmed wrote:

> Hello all,
>
> As I know every ISP must have direct link with SIXP to route their 
> traffic to other ISPs, in this case Sudren should have direct link 
> with SIXP,

i know that sudren used to have a direct link to SIXP.  i do not know if 
that is still true.  i went to www.sixp.sd to find out more information, 
but there is just a single sentence on the front page about current 
peers (which does include SUIN);  the links to the looking glass don’t 
work for me so i could not validate this.


> Sudatel will not route other ISPs traffic to SIXP, only Sudatel 
> traffic will be routed to SIXP ,
> but other ISPs traffic through Sudatel will be routed directly to 
> upstream provider.

well, this is where we might disagree.  from the earlier traceroute that 
i posted earlier, it looks like there is a purchaser <-> supplier 
relationship between sudren and sudatel, where sudren buys IP transit 
from sudatel.

if this is true, then, ie. sudatel is the transit/upstream provider for 
sudren, and sudren is their client, then it’s sudatel’s 
responsibility to advertise their clients’ address space to any and 
all external BGP parties, unless otherwise requested, but the client.  
this means that the upstream would typically advertise the client 
address space to:
# their transit providers
# their downstream clients
# their peers at any IXP(s)e

in your message above, “only Sudatel traffic will be routed to SIXP” 
is a misnomer, since “Sudatel traffic” is actually the sum of all 
traffic that might be originated inside the sudatel asn, *AS WELL AS* 
their client’s traffic  (ie.  all of it!).   it is a common mistake 
for a transit provider to not advertise all their client address space 
at IXPs;  but it’s still a mistake :-)
the easy way to think about this is :
# you pay your upstream for a service  (ie. internet access)
# your upstream delivers this to you, by announcing your address space 
at places where they interconnect, and routing the relevant return 
traffic to you

as the upstream, you try to connect to as many places as possible, to 
ensure that traffic for your network (which includes all your clients) 
comes to you directly, and not via *your* transit provider.  that’s 
why successful ISPs peer in many places..
as a client, you don’t normally care where and how your upstream 
provider connects.  but you do care about failover.  in the case you 
describe, let’s assume that sudren has a failure on their link to 
SIXP;  if it were true that sudatel should not advertise the sudren 
prefixes to SIXP, then there could be no re-routing of traffic, and this 
would all go overseas, defeating the point of the IXP.  and that’s not 
what you want ..

under normal circumstances, *both* client and transit will advertise the 
client address space;  regarding “other ISPs traffic” .. path 
selection for a third ISP at the IX, would be done by the remote network 
(let’s say ISP C) based on criteria that the ISP-C determines eg. 
shorter as path.  (normally, neither the client, nor the “upstream” 
network will be able to influence this .. )

tl;dr - if transit providers did not advertise their client address 
space at IXPs, then the internet would be a very, very broken place  :-)
—n.