Question on Loosely Synchronized Router Clocks

Xin Liu smilerliu at
Mon Sep 17 21:03:33 UTC 2007

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


Xin Liu

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