ISP Policies

Sun Sep 12 17:47:34 UTC 2004

RG> Date: Fri, 10 Sep 2004 11:36:58 +0530
RG> From: Rohit Gupta

RG> On a related note : Do ISPs ever tweak around with Local
RG> Prefs and weights so as to select BGP paths with greater AS
RG> 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.

RG> Would it ever make sense for a provider to chose a longer AS
RG> 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
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