filtering customer BGP sessions

[John Payne <john () sackheads org>]

I thought it was now common knowledge that it is a good thing to filter 
what your customers announce via BGP.  Unfortunately, Broadwing seems to 
have missed this (broadwing -> conversent.net -> algx just isn't right):

traceroute to smoe.org (199.201.145.78), 30 hops max, 38 byte packets
1  maynard (206.229.91.130)  1.132 ms  1.089 ms  1.046 ms
2  sl-gw20-nyc-6-1-0-TS1.sprintlink.net (160.81.0.45)  28.540 ms  30.302 
ms  28.507 ms
3  sl-bb23-nyc-1-0.sprintlink.net (144.232.13.208)  28.475 ms  28.468 ms 
37.592 ms
4  sl-bb24-rly-0-0.sprintlink.net (144.232.20.183)  51.684 ms  52.427 ms 
41.497 ms
5  sl-gw21-rly-9-0.sprintlink.net (144.232.14.54)  39.972 ms  39.842 ms 
40.162 ms
6  sl-browing-11-0.sprintlink.net (160.81.98.2)  48.255 ms  48.120 ms 
48.040 ms
7  P4-2.c0.wash.broadwing.net (216.140.8.1)  48.210 ms  64.849 ms  47.813 
ms
8  p2-0.a0.nwak.broadwing.net (216.140.8.194)  60.419 ms  65.005 ms 
52.365 ms
9  65.89.249.42 (65.89.249.42)  88.852 ms  54.413 ms  81.290 ms
10  ct1-bb1-at102-50.conversent.net (199.26.223.182)  57.536 ms  55.187 ms 
55.745 ms
11  ma1-bb2-at100-52.conversent.net (206.53.1.2)  48.845 ms  48.395 ms 
49.570 ms
12  ma1-gw1-fa3-1-0.conversent.net (216.41.61.81)  56.991 ms  50.135 ms 
48.877 ms
13  26-99-41-216.wor.ma.nevd.net (216.41.99.26)  53.808 ms  51.835 ms 
80.405 ms
14  ip67-153-123-85.z123-153-67.customer.algx.net (67.153.123.85)  53.443 
ms  78.096 ms  71.467 ms
15  bos10-core1-ge-0-0-0-0.atlas.algx.net (165.117.171.1)  60.773 ms 
76.644 ms  93.462 ms
16  dca10-core2-so-7-0-0-0.atlas.algx.net (165.117.200.18)  66.975 ms 
108.967 ms  104.196 ms
17  dca10-core1-so-0-1-0-0.atlas.algx.net (165.117.192.45)  100.413 ms 
137.700 ms  90.357 ms
18  iad3-core3-pos5-0.atlas.algx.net (165.117.67.62)  96.945 ms  114.586 ms 
93.480 ms
19  iad3-core2-pos6-0.atlas.algx.net (165.117.64.5)  76.542 ms  140.544 ms 
80.533 ms
20  iad3-peer10-pos7-0.atlas.algx.net (165.117.69.165)  77.692 ms  106.074 
ms  64.825 ms
21  ash1-br1-g1-1.gnaps.net (199.232.44.34)  110.832 ms  93.490 ms  99.952 
ms
22  res1-rs1-gi-2-2.gnaps.net (64.220.44.42)  89.152 ms  65.417 ms  111.144 
ms
23  qcy1-rs1-p6-1.gnaps.net (199.232.44.26)  91.686 ms  74.041 ms  74.662 ms
24  qcy1-ar1-g1-0.gnaps.net (199.232.42.114)  77.763 ms  80.636 ms  81.436 
ms
25  link75-250.cent.net (199.232.75.250)  86.499 ms  73.475 ms  98.989 ms
26  smoe-gw-s0.smoe.org (199.201.145.237)  101.319 ms  86.022 ms  95.706 ms
27  jane.smoe.org (199.201.145.78)  83.337 ms  92.693 ms  85.427 ms