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Throughput limits switching capacity

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  • 1.  Throughput limits switching capacity

    Posted Jan 14, 2020 03:27 PM

    Hi guys,

     

    Just to know if my understanding is correct. According to this post which makes sense to me, a switch needs to be able to forward 1488095 packets per second (1.488 million packets per second) to reach 1 Gbps per port (taking into account an Ethernet frame length of 64 bytes):

     

    https://forum.networklessons.com/t/throughput-switching-capacity-relation/3842/2

     

    According to the 2930F 24G 4SFP+ datasheet, the switching capacity is 128 Gbps, which matches (24 x 1Gbps + 4 x 10Gbps) x 2, and the throughput is 95.2 Mbps, which is OK to have the switch at full speed since (24 x 1Gbps + 4 x 10Gbps) x 1.488 = 95.2 Mpps.

     

    However, the 2930F 48G 4SFP+ datasheet says the switching capacity is 176 Gbps, which matches (48 x 1Gbps + 4 x 10Gbps) x 2, but the throughput is 112 Mpps, which is NOT OK to have the switch at full speed since (48 x 1Gbps + 4 x 10Gbps) x 1.488 = 130.9 Mpps. Then, the switch needs a throughput of 130.9 Mpps for not having problems at full speed, but the throughput is only 112 Mpps, which is less.

    2930F.png

    Does then the throughput limit the switching capacity?

     

    Regards,

    Julián



  • 2.  RE: Throughput limits switching capacity

    Posted Jan 20, 2020 08:13 AM
    Hi,

    Any idea?

    Regards,
    Julián


  • 3.  RE: Throughput limits switching capacity

    Posted Jan 21, 2020 01:48 AM

    Average packet size will be a lot larger than 64 bytes, so you will not see a network pushing gigabits per second of 64 byte packets. 



  • 4.  RE: Throughput limits switching capacity

    Posted Jan 21, 2020 09:15 AM
    @pubjohndoe wrote:

    Average packet size will be a lot larger than 64 bytes, so you will not see a network pushing gigabits per second of 64 byte packets. 

    Yes, I know the 64 bytes length is the minimum Ethernet frame length and is the worst case, it will not happen in the real world. But if I made this in a lab with Ethernet frames of 64 bytes, would the switch reach its maximum switching capacity?

     

    Regards,

    Julián