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VSAT technology and installation >> iDirect Forum: hubs and terminals >> SAT Bandwidth Usage

Message started by sushilpandey212 on May 27th, 2011 at 10:01am

Title: SAT Bandwidth Usage
Post by sushilpandey212 on May 27th, 2011 at 10:01am

I wanted to know more on the SAT BW usage in iMonitor. What does the term IP downstream/ IP Upstream, SAT Upstream & Downstream really mean?

I have seen many times the SAT BW to be higher than IP BW, but sometimes the reverse too.

I guess SAT downstream or upstream should be higher than the IP downstream or Upstream as it consists of the Data+ signalling packets.

Please explain me more on these.

Have a good day.

With Regards,


Title: Re: SAT Bandwidth Usage
Post by vydrik on May 27th, 2011 at 8:50pm
SAT Bandwidth is an IP Bandwidth + Overhead, overhead depends on the modcod your are running. I think iNTP is the easiest way to calculate the overhead.

Title: Re: SAT Bandwidth Usage
Post by bod on Jun 3rd, 2011 at 4:45am
Sushil, that is the basic understanding that everyone has but it is a little more complicated than that.

You mentioned that sometimes the IP Traffic is higher and at others, the SAT Traffic  is higher. There is a good explanation for this.

Lets first take a quick look at exactly where the traffic is being measured at. The IP Traffic Stats are collected at the entrance to the Protocol Processor or the Upstream/Internet side. The SAT Traffic Stats are collected at the output of the Protocol Processor or Tunnel side.

To explain why there is a difference and the fact that they sometimes take turns as to which one is higher. We would normally think that SAT Traffic STATS would be higher because as mentioned earlier it incorporates the IP data plus overhead/signaling packets however, in the event of a large TCP download the IP Traffic STATs are often higher due to the TCP ACKs that are sent back and forth from the Protocol Processor and the internet end point.

On the Satellite side, iDirect's TCP acceleration eliminates a large majority of these TCP ACKs thus reducing traffic flow across the satellite. In this instance the TCP ACKs on the Internet interface would be greater than the overhead/signaling packets on the satellite side.

Hope this helps.

Title: Re: SAT Bandwidth Usage
Post by sushilpandey212 on Jun 3rd, 2011 at 1:06pm
Thanks a lot bod.

Can you please provide me links or anything to understand the iMonitor in detail.

I got the usual manual, it's handy, but sometimes I need depth on some subject matters.

Have a good day.


Title: Re: SAT Bandwidth Usage
Post by dhrisht on Mar 15th, 2012 at 5:09pm

Yes this is really complecated and I would like to understand properly as it is not yet clear. I tried reading iMonitor guide but did not understand. If there is any clear explanation than it will be useful.

Thanks in advance.

Title: Re: SAT Bandwidth Usage
Post by dhrisht on Mar 15th, 2012 at 6:14pm
When I asked iDirect, I received below reply:

IP traffic is measured as traffic incoming to a PP blade destined for the particular remote being monitored, or traffic incoming to the remote from the LAN port.  This measurement is traffic before it's been processed by the QoS engine and had MIR/CIR/MIN data rates applied.  Due to this it could report higher than MIR, as MIR has not been applied.  All excess data above the MIR will get dropped.  

SAT traffic is measured after the traffic has been processed by the QoS engine, either on the remote or on the PP, and had MIR/CIR/MIN data rates applied.  This should always be at or below the configured MIR.  It may be lower than the MIR even if there is still more data to send, as the traffic may be limited due to QoS rules and how data is sent on the upstream.  For example, UDP and TCP traffic must be sent in different time slots, so if there is more TCP than UDP traffic, some of the space in UDP slots will be wasted.  

Title: Re: SAT Bandwidth Usage
Post by erico on May 12th, 2012 at 6:26pm
Hi everybody,
happy to join this discussion,I am very interested by this subject. In fact I was analyzing traffic on an infiniti network, runing software version
I have built long term bandwith report for both SAT and Ip stats. I am a bit confused as the difference between the two stats is >7Mbps in the Downstream, the SAT stats show 7Mbps more than the Ip stats, and the difference seems to be Broadcast traffic. Does anybody know what is the Bcast traffic between the PP and the remotes related to?My report is based on the all the remotes in the network.
the network has a 12mbps downstream Inforate, 0.793 FEC, but the SAT Stats for all the remotes shows peaks of 19Mbps and Bcast trafic of 7Mbps.
Waiting for comments...

Title: Re: SAT Bandwidth Usage
Post by dot on May 16th, 2012 at 9:16am
Hi Eric

Broadcast traffic on the downstream is normally related to multicast updates being sent by the NMS. This could be changes that you are applying or the revision server running.

Also when aggregating all your sites remember that the numbers are averaged which can lead to a degree of error.

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