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Senior Member

Posts: 59
Lagos, Nigeria
Aug 22nd, 2007 at 4:48pm  
please, I want to difference between CIR/EIR/Burst Priority/Queue Size and their relationships.
At site which am supposed to have 64kbps dedicated, and am having cirtohub 34 and  maxbwtohub  68, is this a dedicated or sheared  service? please, i want to know.
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Eric Johnston
YaBB Moderator

Posts: 2109
Reply #1 - Aug 22nd, 2007 at 10:16pm  
Amongst Cisco networking people CIR means committed information rate. When the data rate exceeds the CIR, the network starts dropping packets.  Amongst satellite people CIR means continuous information rate.  In this case you will be dropping packets or blocking at your end if you push more than the link can take.  A continuous information rate may be provided by an SCPC transmission, by a dedicated regular time slot within a higher bit rate stream or by a regular sequence of bursts in a fixed time plan TDMA system.  CIR is what you get from a dedicated service.

EIR means excess information rate. This is a possible extension towards an upper limit of the data rate when no network congestion exists. The EIR specifies the data rate in excess of the Committed Information Rate (CIR) to which a circuit can burst when no network congestion exists.

So if you have a CIR of 64 kbit/s you have that dedicated to you and available all of the time.  If the EIR is 30 kbit/s then, provided that the network is not congested you will be able to go up to 94 kbit/s from time to time.

Burst Priority:  Within a particular class of traffic, e.g. VoIP, it is possible to set a guaranteed allowed bit rate.  This is getting complex as it is possible to have multiple queues of different classes of traffic (VoIP, FTP, HTTP, SNMP, TCP, ICMP etc) each with its own priority set.  Queue Size has to do with when the router will start dropping packets.

For more on these traffic matters you are welcome to study Cisco documentation.  It is a massive read and a major task to learn.   It is not easy to set up a Cisco router, to then monitor the traffic and to determine if the results are good or bad or of no effect, in terms of customer satisfaction.  The matter is of great importance as the objective must be to make the best use of the very expensive basic satellite capacity.
Anyway, you say:  64kbps dedicated, and am having cirtohub 34 and maxbwtohub 68, is this a dedicated or shared service?

If you have "cirtohub 34" then you should be able to operate all of the time at 34k.   The "maxbwtohub 68" suggests that, at times when the network is not congested, you may be able to send at up to 68k.

If you have "64k dedicated" then this means that you can send at 64k all of the time, and perhaps not at any higher rate.

Best regards, Eric.
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« Last Edit: Aug 23rd, 2007 at 11:32am by Eric Johnston »  
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