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2006.06.05 NANOG-NOTES Pretty Good BGP Josh Karlin
2006.06.05 Pretty Good BGP Josh Karlin, Stephanie Forrest, Jennifer Rexford slides are at: http://www.nanog.org/mtg-0606/pdf/josh-karlin.pdf Main idea: delay suspicious routes lower the preference of suspicious routes for 24 hrs Benefits: network has a chance to stop the attack before it spreads accidental short-term routes do no harm no loss of reachability adaptive simple Algorithm Detection: monitor BGP update messages treat origin AS for prefix seen in past few days as normal new origin AS treated with suspicion for 24 hours. treat new sub-prefixes as suspicious for 24 hours. Response: suspicious prefixes given low localpref, not used or propagated suspicious sub-prefixes are temporarily ignored Example prefix hijack (without PGBGP) same specificity Example sub-prefix hijack (without PGBGP) two /9's cut from a /8 In these examples, AS 5 acted in its own self interest, but it helped protect the rest of the net beyond it. Simulations of two deployment strategies Random, and core+random. Random, with 0 deployed, half the network will be affected, better solution as higher fraction of ASes deploying it. If core of network deploys (core ASes have at least 15 peer-to-peer links) only 62 out of the 20,000 ASes. All but 2% of network protected with that. Sub-prefix hijack suppression a bit tougher, but still good results as core implements it. hijacks in the wild 1997, AS 7007 sub-prefix hijacked most of the internet for over 2 hours Dec 2005 26-95 hijackings during month jan 2006, panix's /16 stolen by conEd Feb 26, 2006, sprint and verio carried TTNET as origin AS for 4/8, 8/8, and 12/8 IAR: internet alert registry IAR verifies hijack attempts a near realtime database of suspicious routes email alerts are sent to those who opt-in for the ASes they choose to recieve alerts for operators recieve alerts only when their AS has caused the hijack or is the victim Tier1 ASs receive one hijack alert per day typically working prototype Solutions with guarantees (and lots of overhead) sBGP soBGP psBGP Anomaly dectors Whisper MOAS lists Geographic based Good Practice proper route filters Route filters protect the internet from you and your customers, not vice versa. Why pretty good BGP? maintains autonomy incrementally deployable no flag day no change to the BGP protocol Effective with a small deployment only requires a software upgrade or change in config generation. Most important, requires minimum operator intervention http://cs.unm.edu/~karlinjf/pgbgp/ Q: (someone)? from UCLA--if you delay the route for 24 hours, if the original AS withdraws it, what happens? A: you'll still end up using the new route, as it just has a lower localpref, so moves will still work. Q: Danny McPherson -- what if origin AS is spoofed to match the origin AS by the hijacker--does this stop it? A: No, that's a man-in-the-middle, or at least it looks like it, and this can't handle that, so it's only pretty good; that would be a later phase. Q: He also notes if your prefix is hijacked, your email alert is likely to get jacked as well. A: True--subscribe from multiple prefixes/domains to be safe! Q: Phil Rosenthal, ISPrime. What happens when a small ISP in south america leaks the internet to an upstream that doesn't filter them? A: Yes, those leaks suck up a lot of memory; this doesn't help because the origin AS is still correct, but the intervening paths are bogus. If the route for a sub-prefix is seen with the origin AS along the path, not seen as a hijack. Q: Jared Mauch, NTT america; follow-on point, you just have a strange AS along the path, but the rest of the origin is correct. A: No, they don't look at the whole path yet; maybe in the future Q: Sandy Murphy, Sparta--thinking of statement at the end, it handles backup routes ok. it works best where operational changes of the origin happen at a human-paced interval. There are some prefixes which seem to oscillate at a much more rapid pace. What about studying prefix behaviour over a longer period of time? Is it locked into 24 hours, or can be adjusted to match better frequency? A: Not locked at 24 hours, could be adjusted to different 'sensitivity' as needed. Q: Randy Bush, IIJ: The internet is not static, those things which relay on viewing it as static like route flap dampening can bite us. We need to enable more and more dynamic behaviour, not less, and Randy thinks this is going the wrong direction. A: That's nice, but presenter disagrees and thinks this is a helpful step in the right direction.