New on LowEndTalk? Please Register and read our Community Rules.
All new Registrations are manually reviewed and approved, so a short delay after registration may occur before your account becomes active.
All new Registrations are manually reviewed and approved, so a short delay after registration may occur before your account becomes active.
Comments
The direct path is still shorter as AS1 is 1000KM from you regardless of if you send the traffic directly to them or not, having an indirect path via AS2 would make it 1001KM since ultimately AS1 is your destination.
A better example is if you're peering with AS1 (1000KM from you) AS2 (1KM from you) and there's an AS3 (2KM from you) and AS1 is the only user that you are peered with that is connected to AS3 then you'd have a 2000KM+ round trip to connect to AS3 at which point it may be a better to ask AS3 if they're willing to peer.
This happens on real networks as well, it's not unheard for ISP's in the UK to send traffic over to AMS-IX even for domestic destinations, Also it used to be that if I traced my Cable line from the VDSL it would go London > Birmingham and back (London makes sense as thats where the PPP lands and where most of the IX's are, no idea why Birmingham though)
I said exactly the same ;-) The direct way should always be preferred. I dont see why peering with "near" peers should be better than direct with peers that are far away.
If you only peer with "near" peers and want to reach a "far" peer, the path would be longer as if you would peer direct with them.
You are AS1 (EU), peering with AS2 (US) and AS3 (EU). AS3(EU) is peering with AS4(EU). AS4(EU) is peering with AS5(EU). AS2 (US) is peering directly with AS5 (EU).
Now your shortest route to AS5 is AS1 - AS2 - AS5. However AS1 - AS3 - AS4 - AS5 would make more sense as the traffic doesn't go through the US.
You can always mess with the weighting manually if thats your thing.
Yes, you can use MED, Prepending, Localpref or Weight
see here: http://docwiki.cisco.com/wiki/Border_Gateway_Protocol#BGP_Path_Selection
Of course, just pointing out an example where traffic might take a detour due to weird peering.