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Definitions and differences between switch specifications

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  • 1.  Definitions and differences between switch specifications

    Posted 06-10-2019 13:37

    Hello community


    Could you help me with the definitions and differences between system throughput, Data rate and Backplane speed for switches?


    Best regards


    Carlos Contreras

  • 2.  RE: Definitions and differences between switch specifications
    Best Answer

    Posted 06-11-2019 00:07



    For switches, backplane speed is with respect to the Virtual chassis where the switches are connected to eachother using VCP ports. Hence, backplane speed is the capapcity of the VCP ports. /                                


    //For eg: and EX4550 can have a maximum of 4 VCP ports with each VCP port having a capacity of 64Gbps full-duplex. Hence, the maximum backplane speed for the VC is 256 Gbps full duplex.//


    //Lets try to understand the data rate and system throughput.


    Data rate: Data rate is w.r.t the network ports and can simply be defined as the maximum possible traffic that can be sent through all these ports.


    Ex: EX4550 can have a maximum of 48 10Gbps ports. That makes 480 Gbps simplex traffic and 960 Gbps full duplex non-blocking traffic and this is the maximum.//


    //When it comes to the system throughput, to define it, it is the practical value the link can acheive in real time considering the latency, additional headers in case of fragmentation and many other factors. For eg, this can be calculated as the maximum packets per second a device can handle in real time.


    For ex: EX4550 provides 14.88 Mpps of throughput per port at the minimum Ethernet frame size. With a maximum of 48 ports, the Maximum throughput it can acheive is 14.88 * 48 = 714 Mpps.


    You can refer and compare these specifications for the EX4550 at https://www.juniper.net/us/en/products-services/switching/ex-series/ex4550/specs/


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  • 3.  RE: Definitions and differences between switch specifications

    Posted 06-11-2019 12:27

    I would disagree with backplane definition.  Most switches today are build as a SOC - switch on a chip.  The backplane for these, versus say a chassis, is generally equal to the sum of the interfaces as today most switches are line-rate or non-blocking.  Where you might run into a potential blocking architecture is when the switch has multiple such chips, and therefore needs some connection/bus to interconnect the chips, which might very well NOT be able to handle the full potential data rate.  An example of this (for external switch to switch, vs internal) is VC.  Generally VC does NOT support the potential full-line rate of the switch itself, but often times the "backplane" specs are the sum of all the revenue (non-VC) interfaces.


    Since the VC interfaces can also be used instead as revenue ports for a single switch, the switches "backplane" number is generally a combination of all revenue ports, plus all VC ports, acting as revenue.  This assumes the chip itself is non-blocking, which for today's switches/chips, is true like 95+% of the time.


    For a chassis backplane, could well outperform actually "switching/fabric capacity" assuming the backplane itself is passive.



  • 4.  RE: Definitions and differences between switch specifications

    Posted 06-21-2019 07:56

    Fully agree with   that,

    Backplane - In general, passive part of chassis. (But still there are some physical restrictions).

    switching/fabric capacity - is how many pakets/bits can be threated by a chassis or slot in a chassis.


    If you need to know some specification of our devices, please, contact the marketing department or use our web site.