Dear Nanog members,
I am a PhD student at University of Toronto and I am working on traffic
burstiness in data centers. In the following I am asking two questions to
raise motivation for my research. I appreciate if anyone could answer these
questions to their best knowledge. *The questions are:*
1) ‘Bursty’ is a word with no agreed meaning. How do you define a bursty
traffic?
2) If you are involved with a data center, is your data center traffic
bursty?
-- If yes,
-- Do you think that it will be useful to supress the burstiness
in your traffic? (For example by pacing the traffic into shorter bursts)
-- If no:
-- Are you already supressing the burstiness? How?
-- Would you anticipate the traffic becoming burstier in the
future?
Thanks,
Monia
Hi Monia,
'Burst' is a very broad term. It would be useful to clarify to what you are
referring.. I can think of a few possibilities:
- Data Transmission: The length of an uninterrupted flow of information.
- Traffic Engineering: The ability for traffic to temporarily exceed it's
allocated (average) bandwidth share.
- Internal Event: A backup (scheduled) or a server failure (adhoc) altering
traffic patterns.
- External Event: Marketing campaign / event coinciding with increased
traffic towards say, a website.
Perhaps -> Over what period of time is a 'Burst'..?
Cheers,
Heath
Bursty is a very relative thing. It depends on the time frame you are
considering. For example, at any given instant of time a circuit is
either carrying data or it isn't. The network is always either 100% in
use or 100% idle if you look at it in an instantaneous fashion. There
is also a misconception that bursty is bad. In very fast networks, the
systems complete their transmissions very quickly so appear bursty. In
a lower bandwidth network the system may transmit almost continuously
because there is always data queued for transmission. This would appear
as non-bursty continuous traffic. What you are really looking at here
is the value and effect of traffic shaping. You should probably repose
your question and ask about traffic shaping. In my opinion, like most
QoS mechanisms, traffic shaping is something you do as a compromise to
get the best service in a network that does not have enough bandwidth or
has high latency. The best solution is almost always more bandwidth.
The idea of suppressing bursts is not something that I think would be
optimal. What you are saying is really that a system has data to send
but I am not going to allow it to go out as fast as possible. I am
going to do some kind of traffic shaping which might be more fair to
other traffic but at the end of the day, all you can do is add delay.
Steven Naslund