[c-nsp] eBGP square vs triangles?

[Andy Taylor]

Hi,

Hopefully a simple eBGP question:

If I have 2 edge routers in an AS, and 2 edge routers in another AS is it
best practices to have them in a square, or triangles?

By this I mean AS1 has router 1 and router 2 (running iBGP between them),
and AS 2 has the same.

Is it best practice to have an eBGP peer between AS1 router 1 <-> AS2
router 1, and AS1 router 2 <-> AS2 router 2, or:

AS1 router 1 peering with AS2 router 1 and 2, and AS1 router 2 peering
with AS2 router 1 and 2.

Either way, can somebody confirm the best practice and why?

Any help would be greatly appreciated.

All the best,

Andy