Switching

Hi,

Can any body please let me know if there any calculation to convert the Mpps values to Gbps..and also how to calculate the effective forwarding rate of a switch

regards, ruwini

Hi Ruwini,

In my opinion, you can not really calculate this, because packet sizes differ offcourse...

Of which switches are you speaking ? The EX4200 en EX3200 datasheets might help you out to determine if the capacity is enough for your goals:

EX3200 Series:

Packet Switching Capacities

24P/24T: 88 Gbps
48P/48T: 136 Gbps

Layer 2 Throughput (Mpps)

24P/24T: 65 Mpps (wire speed)
48P/48T: 101 Mpps (wire speed)

EX4200 Series:

Packet Switching Capacities

24P/24T: 88 Gbps
48P/48T: 136 Gbps
24F: 88 Gbps

Layer 2 Throughput (Mpps)

24P/24T: 65 Mpps (wire speed)
48P/48T: 101 Mpps (wire speed)
24F: 65 Mpps (wire speed)

As you can see, they claim wire speed connectivity, so is there a specific reason why you are asking ?

G's Dennis

Hi Ruwini,

You can convert Mbps to Gbps by simply dividing by 1000.  That's derived from the definitions of Mega (x 10^6) and Giga (x 10^9).  Be careful though... when referring to Bytes (rather than bits) you need to divide by 1024 to get from Megabytes to Gigabytes.

Anyway... As pointed out by dennish, calculating a throughput in packets per second is possible only when a particular packet size is used.

If we take the 65Mpps and look at a "worst case" 64byte frame, you'll need to add to that the headers (14 or 18 bytes, depending upon whether there is a VLAN tag or not) and the inter-packet gap (12 bytes, IIRC).  So, each 64 byte frame actually consumes 64+14+12 (90 bytes) or 64+18+12 (94 bytes).  

24 GE ports with 1Gbps in and 1Gbps out = 48 Gbps

(48000000000/8)/90 =~ 66Mpps

(48000000000/8)/94 =~ 64Mpps

65Mpps is a reasonable average.

Those are the Layer 2 switching capabilities of a 24 port switch based on the available capacity on the ports.  The actual switching capacity of the PFE is much higher than that (declared at 88 Gbps for the 24 port switch).  So, the PFE is capable of significantly more throughput than the interfaces can offer to it.

Rgds,

Guy 

We got a mix of terms here.

Mpps = Million packets per second

Gbps = Gigabits per second

Mbps = Megabits per second

Hi All,

Anyone please suggest me MX104 Layer-3 Switching how many maximum MAC address space supported and how much Switch has forwarding rate supported in million packets (64 Bytes) per second (MPPS)

Regards,

Yasir Shaikh