[Cerowrt-devel] routers you can throw off the back of a truck

Michael Richardson mcr at sandelman.ca
Mon Jan 18 20:06:26 EST 2016

Jonathan Morton <chromatix99 at gmail.com> wrote:
    >> Jonathan Morton <chromatix99 at gmail.com> wrote:
    >>> I haven’t yet found a robust way to automatically sense link capacity from
    >>> the upstream side.  You’ll therefore need to set a conservative static
    >>> value for the uplink capacity.
    >> As the maintainer of a PPPoE concentrator, and operator of some networks,
    >> I've been considering whether one can estimate the bandwidth using round
    >> trip PPP IPCP keep alives.   Clearly, if both ends participate in time
    >> stamping then it is much better, but I've been wondering if we can do some
    >> incremental deployment on one side or the other.
    >> Sadly, I mostly just think about this while cycling; I haven't written any
    >> code yet.

    > In most PPPoE deployments I know about, there is also a modem from
    > which the actual, precise link rates can usually be queried.  Where
    > that’s not the case, IPCP (or is it LPCP?) probes would be a reasonable
    > workaround, but it must still be understood that the signal it provides
    > is only valid under saturating traffic, which complicates
    > implementation.

Yes, you are rtight, I want to do LPCP echo requests.

The modem might know what speed it has with the tower/DSLAM, but won't know how
congested the backhaul link is.   There are some third party/white label 3G
arrangements in Canada that use PPP/L2TP back to the third-party provider,
but most route the IPv4 (only) packets via IPsec or MPLS.

]               Never tell me the odds!                 | ipv6 mesh networks [
]   Michael Richardson, Sandelman Software Works        | network architect  [
]     mcr at sandelman.ca  http://www.sandelman.ca/        |   ruby on rails    [

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