[Ndn-interest] Ndn clock synchronization requirements

Viktor S. Wold Eide viktor.s.wold.eide at gmail.com
Tue Jun 11 07:03:27 PDT 2019

Dear list members,

The NDN Protocol design principles state that the core network protocol
operations should not depend on clock synchronization:

I do look into this from the perspective that hosts should be able to only
rely on their internal clock, that is, without depending on any kind of
network time protocol synchronization.

I have been doing some testing with the Ndn software, including the most
recent version of NLSR. From what I see, NLSR requires clocks on different
hosts to be fairly well synchronized. The clock synchronization requirement
is stated in the "Lessons from development and deployment" section in [1]
from 2016 : "... This means that the network has to be roughly time
synchronized for the protocol to work. ..."

I could not see a clock synchronization requirement listed elsewhere, but I
might have overlooked something.

I see that the testbed page notes the following :
Clock Skew Status: (As compared to UCLA Node's time: Green: < 5 secs off;
Yellow: 5 < > 30 secs; Red: > 30 seconds off). This might be interpreted as
the host clocks should be synchronized to, preferable within 5 seconds, and
at least within 30 seconds.

>From what I understand clock synchronization is currently required for the
- certificates to be within valid range
- NLSR LSA timeout handling

This leads to the following questions:

Is there anything else or in NDN core network protocol operations that
require clock synchronization? In case, to what extent?

I guess clock synchronization can be made very relaxed for certificate
validation? For example on the order of many hours clock skew.

Has anyone looked into ways to change / modify the NLSR protocol / software
in such a way that it is not dependent on clock synchronization? Or at
least not to this level of synchronization.

[1]  NDN, Technical Report NDN-0037, 2016.
Revision 1: January 26, 2016.

Best regards
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