Date: Mon, 17 Sep 2007 14:03:33 -0700 From: "Xin Liu" <smilerliu@gmail.com> Sender: owner-nanog@merit.edu
Dear Nanogers,
We are a bunch of academic researchers interested in Internet security. We notice that some research papers require that BGP router clocks be globally synchronized to a 5-minute granularity. If a router's clock is off by more than 5 minutes, it cannot forward packets, but there's no other side effect. From an operational point of view, do you think it is a practical requirement? If not, what are the potential problems that prevent router clocks from being loosely synchronized? If you consider 5-minute too small, what do you consider as a practical clock skew requirement for BGP routers on the Internet?
We'd appreciate your input very much. It will help us understand what's practical and what's not in our work. Please reply to us directly.
What papers? I can assure you that BGP has no such requirement. I suspect sBGP and SoBGP might have such a requirement, but that's not "real world". I had a router that lost it's NTP servers and was off by about 20 minutes. The only obvious problem was the timestamps in syslog. (That's what alarmed to cause us to notice and fix it.) -- R. Kevin Oberman, Network Engineer Energy Sciences Network (ESnet) Ernest O. Lawrence Berkeley National Laboratory (Berkeley Lab) E-mail: oberman@es.net Phone: +1 510 486-8634 Key fingerprint:059B 2DDF 031C 9BA3 14A4 EADA 927D EBB3 987B 3751