cold-potato at L3/Chi into UU?

Sat Jan 6 19:51:00 UTC 2007

In Chicago, L3 appears to be routing some traffic to UU directly, but 
for some other UU destinations, L3 is handing-off to UU via New York:

trace from L3/Chi to 209.98.0.2 (AS8015 via 701) is carried to UU via 
New York (edited):

>  1 ae-1-53.bbr1.Chicago1.Level3.net (4.68.101.65) 8 msec
>   2 as-4-0.bbr2.NewYork1.Level3.net (64.159.0.238) 20 msec
>   4 mci-level3-te-newyork1.Level3.net (4.68.110.234) 20 msec
>   8 visi-gw.customer.ALTER.NET (157.130.98.2) [AS701 {ALTERNET}] 32 
> msec

Oddly, a L3/Chi trace to the last hop above within AS701 (157.130.98.2) 
enters UU immediately in Chicago, taking the shorter path to 
Minneapolis:

>  1 ge-7-0-0-56.edge1.Chicago1.Level3.net (4.68.101.173) 0 msec
>  2 0.so-0-3-0.BR2.CHI13.ALTER.NET (204.255.168.117) [AS701 {ALTERNET}] 
> 0 msec
>  6 visi-gw.customer.ALTER.NET (157.130.98.2) [AS701 {ALTERNET}]  8 msec

UU support has verified that AS8015 prefixes are advertised at UU's 
L3/Chi peering point; and L3 support reports this is "routing as 
designed".   I would guess that UU requires its peers to use hot-potato 
routing, so I'm at a loss as to what kind of traffic engineering is 
being used.

-- 
Bradley Urberg-Carlson
VISI Network Operations; pgp keys avaialble at http://www.keyserver.net/