Networking General

[strikeforce]

I am trying to shape rate 300Mbps for 1Gbps port. In order to configure that I need to have below settings.

Committed Information Rate (CIR) (KBits/Sec)
Committed Burst Size (CBS) (Bytes)

If the burst size is configured at 600 ms with the bandwidth limit configured at 300 Mbps ie 

300 Mbps x 600 ms = around 21 Mbytes

Burst size is =22020096  Bytes  is it right?

what is CIR? as far I understood is average bandwidth. Is it 600Mbps on 1gbps port. Could you please let me know what should be the CIR setting.

Thanks

[DELL-Willy M · Accepted solution]

Here are a couple articles that define CIR (Committed information rate)

searchnetworking.techtarget.com/.../committed-information-rate

en.wikipedia.org/.../Committed_information_rate

Committed information rate or CIR in a Frame relay network is the average bandwidth for a virtual circuit guaranteed by an ISP to work under normal conditions. At any given time, the bandwidth should not fall below this committed figure. The bandwidth is usually expressed in kilobits per second (kbit/s).

Both these articles discuss how this is a feature in a Frame Relay network.  The PowerConnect series does not support frame relay as far as I understand.

In speed calculation 1 Mbps = 1000 Kbps (not 1024 Kbps), it is a common misconception to use 1024 in conversion between kbps and bps. However, if you are calculating storage it is correct to use 1 MB = 1024 KB.

Here is a unit conversion calculator to help with your calculations.

www.mediaroad.com/.../unit_convert

=600 Mbps [Megabit-per-second]=600000 Kbps [Kilobit-per-second]=75 MB/sec [Megabyte-per-second]=75000 KB/sec Kilobyte-per-second]

Hope this helps,

Keep us updated if you can.

[strikeforce]

=600 Mbps [Megabit-per-second]=600000 Kbps [Kilobit-per-second]=75 MB/sec [Megabyte-per-second]=75000 KB/sec Kilobyte-per-second]

Thanks for your clear explanation. Now it is clear about CIR. ABout CBS could you make it clear.

I want to shape bandwidth to 600 Mbps

I choosen CIR =600000 KBits/Sec

For burst I am using below formula.

Committed Burst Size (CBS) (Bytes)  =  interface media rate  x  allowable time for bursty traffic  /  8 bits 

Committed Burst Size (CBS) (Bytes)= 600000000*0.005/ 8 bits = 375000 bytes

In the above I am using allowable time 5ms=0.005 sec. 

The above calculation of burst size is right? With the above configuration can I shape traffic to 600Mbps? 

Please help me with the solution.

Thanks

[DELL-Willy M · Accepted solution]

The calculation looks to be correct based on the information that we have looked at.

Here is some further information from this wiki page on Frame Relay.

en.wikipedia.org/.../Frame_Relay

Congestion control

The Frame Relay network uses a simplified protocol at each switching node. It achieves simplicity by omitting link-by-link flow-control. As a result, the offered load has largely determined the performance of Frame Relay networks. When offered load is high, due to the bursts in some services, temporary overload at some Frame Relay nodes causes a collapse in network throughput. Therefore, frame-relay networks require some effective mechanisms to control the congestion.

Congestion control in frame-relay networks includes the following elements

1. Admission Control. This provides the principal mechanism used in Frame Relay to ensure the guarantee of resource requirement once accepted. It also serves generally to achieve high network performance. The network decides whether to accept a new connection request, based on the relation of the requested traffic descriptor and the network's residual capacity. The traffic descriptor consists of a set of parameters communicated to the switching nodes at call set-up time or at service-subscription time, and which characterizes the connection's statistical properties. The traffic descriptor consists of three elements:

2. Committed Information Rate (CIR). The average rate (in bit/s) at which the network guarantees to transfer information units over a measurement interval T. This T interval is defined as: T = Bc/CIR.

3. Committed Burst Size (BC). The maximum number of information units transmittable during the interval T.

4. Excess Burst Size (BE). The maximum number of uncommitted information units (in bits) that the network will attempt to carry during the interval.

[strikeforce]

Thanks for providing valuable answer. I configured the switch and now it is under testing. I will inform here once I am able to shape the desired traffic.

Thank you!

[strikeforce]

Switch failed to shape inbound traffic.  I want to shape the traffic on port 5 to 400Mbps but I could see in the graph that traffic crossed 400Mbps.  Below are the bandwidth settings under QoS. QoS mode is basic. I did not changed other settings. What are the settings which I need to do in order to shape inbound traffic. Waiting for the reply. 

[DELL-Willy M]

Can you provide what switch model you are trying to configure and the current firmware version?

thanks

[strikeforce]

PowerConnect 5524   SW version 4.0.1.12

Thank You

[DELL-Willy M · Accepted solution]

Here is a link to the available User Guide and CLI Guide for the 55XX switch.

support.dell.com/.../pc5524

Page 653 starts the discussion about Bandwidth QoS.

Bandwidth

The amount of traffic that can be received and transmitted on an interface

can be limited by the following:

• Ingress Rate Limit — Number of bits per second that can be received

from the ingress interface. Excess bandwidth above this limit is discarded.

• Egress Shaping Rates is defined by the following:

– Committed Information Rate (CIR) sets the average maximum

amount of data allowed to be sent on the egress interface, measured in

bits per second

– Committed Burst Shape (CBS) sets the maximum burst of data that

is allowed to be sent, even though it is above the CIR. This is defined

in number of bytes of data.

www.google.com/search

400 Mbps = 419 430 400 bits per second so if you want to limit the inbound traffic on port 5 then I would recommend inserting 419,430,400 in the ingress rate limit column for gi1/0/5.

[strikeforce]

In GUI it needs Ingress Rate Limit  in KBits/Sec. Is it right below value or the value should be in Bits/Sec?

I used the one which you referred  http://www.mediaroad.com/products/speedcheck/free_tools/unit_convert/

Ingress Rate Limit = 500000 (KBits/Sec) 

In reality what happens when the traffic on port 5 reaches threshold ie over 500Mbps. All packets are dropped over 500Mbps or it is added to token bucket? 

Thanks