Question on Loosely Synchronized Router Clocks

From Tue Sep 18 10:57:15 2007
Date: Tue, 18 Sep 2007 08:55:19 -0700
From: "Xin Liu" <>
To: "Bora Akyol" <>
Subject: Re: Question on Loosely Synchronized Router Clocks

Ideally, yes, a protocol should not rely on clock synchronization at
all. However, to ensure freshness of messages, we don't have many
choices, and clock synchronization seems to be the least painful one.
So we asked about router clocks on the current Internet. If normally
router clocks are synchronized and we have a mechanism to detect and
fix out-of-sync clocks, is it reasonable to assume clock
synchronization in the rest of our design?

You are free to "assume" anything you feel like in the design of a new

The greater the divergennce between your 'assumptions' and *UNIVERSALLY*
IMPLEMENTED conditions in the real world, the more barriers there are to
acceptance and deployment.

Within a single administrative domain, routers are 'usually' -- but *NOT*
"almost always" -- moderately closely synchronized. Across different
administrative domainns, any such synchronization is 'happy accident',
nothing more.

As far as 'assuming clock synchronization' goes, one of the other subscribers
to this list has a _very_ applicable remark: "I encourage my competitors to
design like this." <grin>