On a related note : Do ISPs ever tweak around with Local Prefs and weights so as to select BGP paths with greater AS PATH length? Would it ever make sense for a provider to chose a longer AS PATH length BGP route against a shorter AS PATH length route? Rohit MTech Comp Sc. Institute of Technology Banaras Hindu University ----- Original Message ----- From: “Howard C. Berkowitz”
Yes many do -> Prefer your customer routes via customer interfaces, over
transit and peering interfaces.
Higher LP over cust interfaces = more bits = more revenue. There is nothing
wrong with this IMO, considering many of them who do this, also provide
a community for customers to override this behaviour.
-J
Date: Fri, 10 Sep 2004 11:36:58 +0530
From: Rohit Gupta
On a related note : Do ISPs ever tweak around with Local
Prefs and weights so as to select BGP paths with greater AS
PATH length?
Definitely. Case in point: I set up a network a few years ago
that included a choice between
X 1
Y Z 1
and the latter, longer AS_PATH was the lower-latency way to reach
most of AS1. A side bonus was that traffic distribution between
their upstreams was better.
Note that, as others have mentioned, such tweaks are more common
on smaller providers that have less splay.
Would it ever make sense for a provider to chose a longer AS
PATH length BGP route against a shorter AS PATH length route?
Yes. See above. Not all AS_PATH hops are created equal, just as
not all IP hops are created equal.
Eddy