Re: [pacnog] Allot Netenforcer AC-401

[Franck Martin <franck@sopac.org>]

I thought trying to fix the TCP window over satellite links does not affect the total bandwidth used because hopefully you have more than one TCP stream on your satellite link. However each stream may be affected by the window... I suspect it would affect real time applications, but they usually use UDP, which does not need an ack packet to be sent back before the rest is sent.

So is it really important to fix the TCP window over satellite links?

My understanding of this window, is the number of TCP packets being sent before a TCP acknowledgment packet must be received to carry on sending TCP Packets.

Philip Smith wrote:

Hi Alex, Alo,

Alex Abraham said the following on 21/11/06 11:02:
  

There is a Cisco IOS which has a
feature to deal with Satellite latency but it requires the far end to also
have this feature enabled.  
    

Yup, you need to be in control of both ends of the link. Or have an
upstream who is friendly enough to either do it on their router, or
better still, put in a dedicated router just for you.

So then it's the case which we discussed at the last PacNOG,
investigating whether it makes financial and operational sense to get
your own colo-space at the other end of your link, and put your own
router (and web-cache, e-mail scrubber, etc) in there. I'd say it is, as
then you are in control of what goes over your very expensive satellite
connection. And that has to be a good thing.

  

I am interested in how this can be done?  What would you need on both ends
to do implement this?  Also what are the impacts?  The issue I can see is
that you can run out of bandwidth faster than if you had this not enabled.
Is this correct?
    

Well, if you are getting more efficient use of the link, it will feel
faster, so people will do more, so you will run out more quickly.

Same as any capacity upgrade. It is faster, so people will do more, so
you will run out again. Internet traffic expands to fill the available
pipes. ;-)

philip
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Franck Martin
ICT Specialist
franck@sopac.org
SOPAC, Fiji
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