Nick Feamster, Zhuoqing Morley Mao, Jennifer Rexford
Internet Measurement Conference, Taormina, Italy, October 2004
Internet Service Providers often establish contractual ``peering''
agreements, where they agree to forward traffic to each other's
customers at no cost. Consistent route advertisement at all
peering points is a common provision in these agreements, because
it gives an AS the flexibility to select egress points for the traffic
(e.g., performing ``hot potato'' routing). Verifying ``consistent
export'' is challenging because route advertisements are exchanged at
multiple peering points and may be modified by routing policies. In
this paper, we propose two algorithms to detect inconsistent routes
using routing and configuration data from an AS's border routers. The
first algorithm requires access to all eBGP routes advertised by a
peer. Because this data is often unavailable, we propose another
algorithm that detects inconsistencies using readily available data.
We have applied our algorithms to the routes advertised by the peers
of AT\&T's commercial IP backbone. Although a peer may intentionally
send inconsistent advertisements to prevent its neighbor from
performing hot-potato routing, we also discuss several configuration
scenarios where a peer may inadvertently advertise
inconsistent routes, despite having consistent export policies.
Finally, we explain how simple modifications to the routers could make
detection of inconsistent advertisements much easier than it is today.
[PDF (160KB)] [PostScript (308KB)] [Gzipped PostScript (96KB)]
Bibtex Entry:
@inproceedings{feamster2004borderguard,
author = "Nick Feamster and Zhuoqing Morley Mao and Jennifer Rexford",
title = "{BorderGuard: Detecting Cold Potatoes from Peers}",
booktitle = {Internet Measurement Conference},
year = {2004},
month = {October},
address = {Taormina, Italy}
}