SD-WAN

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Ask questions and share experiences with SD-WAN and Session Smart Router (formerly 128T).
  • 1.  What is the behavior of traffic engineering when transmit-cap unlimited?

     
    Posted 11-02-2018 00:00
    If I have traffic engineering enabled, and I set transmit-cap to `unlimited` (or leave at the default, which I believe is `unlimited`), does it operate with effectively an unlimited cap? Seems like this would prevent TE from ever seeing congestion, effectively disabling it. Or does it derive a transmit-cap based on the negotiated, or configured link speed?


  • 2.  RE: What is the behavior of traffic engineering when transmit-cap unlimited?

    Posted 11-02-2018 00:00

    @Michael Adams, you have the answer, right?



  • 3.  RE: What is the behavior of traffic engineering when transmit-cap unlimited?

    Posted 11-02-2018 00:00

    Reid, you are correct. The 128T takes the minimum value between the configured transmit-cap and the negotiated link speed. In the case where transmit-cap is set to 'unlimited', the 128T will use the negotiated link speed as the cap.



  • 4.  RE: What is the behavior of traffic engineering when transmit-cap unlimited?

    Posted 11-27-2018 13:23
    MIke, could you clarify something please. The transmit cap defines the limit for the interface as determined by what? Physical link speed? Actual observed link speed? If I have a 10GigE interface plugged into an ISP that is providing a 50Meg Link, does unlimited mean 10GigE or 50Meg? How is the 50Meg determined? By configuration?

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    Patrick Melampy
    Chief Operating Officer
    MA
    (781) 203-8431
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  • 5.  RE: What is the behavior of traffic engineering when transmit-cap unlimited?

     
    Posted 11-27-2018 13:37
    The "transmit-cap" value is configured in our data model per device-interface. If you don't configure it, or set the value of transmit-cap to "unlimited", it will use the speed of the interface by default.

    In the example you cite with a 10Gbps interface capped at 50Mbps by your ISP, you'd need to configure the transmit-cap on that interface to 50Mbps. Otherwise the system will assume it can use all 10Gbps

    Here's an example from a 128T I have running at a cabin out in the boondocks, where the best "broadband" I can get is sloooowwww DSL:

    admin@labsystem1.fiedler# conf auth router becket node labsystem4
    admin@labsystem1.fiedler (node[name=labsystem4])# device-interface wan
    admin@labsystem1.fiedler (device-interface[name=wan])# show
    name                 wan
    description          "WAN interface"
    type                 ethernet
    pci-address          0000:01:00.0
    
    traffic-engineering
        enabled          true
        transmit-cap     2000000
        traffic-profile  ADSL
    exit
    enabled              true
    capture-filter       len>0​


    My 128T is physically plugged into a DSL modem using an ethernet cable... 100Mbps connection. But upstream from that modem, the connection is 2Mbps on a good day. So I've capped my interface to 2Mbps in configuration.



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