This discussion is very interesting, I didn't know about this problem, it has implications to our work on routing security, thanks! On Sat, May 18, 2019 at 11:37 AM Alejandro Acosta < alejandroacostaalamo@gmail.com> wrote:
If you learn, let's say, up to /22 (v4), and someone hijacks one /21 you will learn the legitimate prefix and the hijacked prefix. Now, the owner of the legitimate prefix wants to defends their routes announcing /23 or /24, of course those prefixes won't be learnt if they are filtered.
I wonder if this really is a consideration to avoid filtering small prefixes (e.g. /24): - attackers are quite likely to do sub-prefix hijacks (or say a specific /24), so I'm not sure this `hits' defenders more than it `hits' attackers - I think we're talking only/mostly about small providers here, right? as larger providers probably will not have such problems of tables exceeding router resources.I expect such small providers normally connect thru several tier-2 or so providers... if these upper-tier providers get hijacked, the fact you've prevented this at the stub/multihome ISP may not help much - we showed how this happens with ROV in our NDSS paper on it: https://www.ndss-symposium.org/ndss2017/ndss-2017-programme/are-we-there-yet... Amir Herzberg Comcast professor for security innovation Dept. of Computer Science and Engineering, University of Connecticut Foundations of Cybersecurity: https://www.researchgate.net/project/Lecture-notes-on-Introduction-to-Cyber-... Homepage: https://sites.google.com/site/amirherzberg/home