[j-nsp] M10i FPC PIC Throughput Questions

[Matt Bentley]

Thanks very much.  So confirm, there is nothing that says one PIC will get
a certain amount at minimum right?

What determines what is dropped when there is contention on the bus?  Are
there any commands I could use to see whether a bus is/was congested and
how much of what was dropped?

On Sat, Feb 23, 2013 at 9:37 PM, Christopher E. Brown <
chris.brown at acsalaska.net> wrote:

>
> Bus is _shared_, with CFEB you have guaranteed 3.2Gbit shared by up to 4
> PICs, with E-CFEB is non issue single PIC limit is 1G and E-CFEB will do
> full 1G per no matter what.
>
> If you try to handle more than 3.2Gbit on a CFEB bus (X-0/X/X or
> X-1/X/X) you may see bus contention depending on packet size.
>
> Load 4xGE and maybe.  Load 3xGE + 4xDS3 is pushing limit but OK.
>
> With E-CFEB, non issue.
>
> With CFEB summ the bandwith make make sure is 3200Mbit or less, and 3200
> is shared by all 4 PICs.
>
>
> On 2/23/13 6:51 PM, Matt Bentley wrote:
> > Thanks!  So it would be correct to say you should NEVER see
> > oversubscription on a channelized DS3 card right?  Obviously, you can
> > overdrive a single T1, but you'd never see drops due to the PIC itself?
> >  I guess what I'm asking is whether or not the bandwidth availalble on a
> > FPC is allocated equally per PIC, or if everyone sort of shares it.
> >
> > On Sat, Feb 23, 2013 at 8:13 PM, Christopher E. Brown
> > <chris.brown at acsalaska.net <mailto:chris.brown at acsalaska.net>> wrote:
> >
> >
> >     With the std cfeb after internal overhead per bus capacity is
> 3.2Gbit of
> >     traffic, this is worst case minimum small packets, etc.
> >
> >     Raw bus capacity is IIRC ~ 4Gbit, difference is overhead.
> >
> >     Unless you are doing all small packet, actual limit is higher than
> 3.2.
> >
> >     Enhanced CFEB bumps the raw bus capacity to something around 5Gbit,
> and
> >     the after all overheads forwarding capacity to 4Gbit (based on the 1G
> >     per PIC limit).
> >
> >     Summ...
> >
> >     CFEB
> >             Up to 1Gbit per PIC, 3.2Gbit per bus _worst case small
> packet_
> >
> >     E-CFEB
> >             Up to 1Gbit per PIC
> >
> >
> >     These figures are
> >     On 2/23/13 6:01 PM, Matt Bentley wrote:
> >     > OK - so there has been a lot of discussion around this that I've
> >     seen, but
> >     > I've searched for hours and still can't find concrete answers.
> >      Can someone
> >     > help?
> >     >
> >     > 1.  Does the 3.2 Gbps throughput limitation include overhead?  In
> >     other
> >     > words, Is the "raw" throughput 4 Gbps with effective throughput of
> 3.2
> >     > Gbps?  Or is it 3.2 Gbps of raw throughput with effective
> >     throughput of 2.5
> >     > Gbps?
> >     > 2.  Is this throughput per PIC on the FPC?  So let's say I have
> >     three 4x
> >     > GigE IQ2 PICs and one channelized DS3 IQ PIC.  Does each PIC get
> >     bandwidth
> >     > allocated equally between them?  So is it 800 Mbps per PIC, and
> >     the PICs
> >     > can't "steal" bandwidth from another one?
> >     > 3.  Where, and based on what, is traffic dropped with  Juniper
> >     head of line
> >     > blocking (ie where multiple high speed input interfaces try to go
> >     out the
> >     > same lower speed exit interface)?
> >     >
> >     > Thanks very much!
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> >     >
> >
> >
> >     --
> >
> ------------------------------------------------------------------------
> >     Christopher E. Brown   <chris.brown at acsalaska.net
> >     <mailto:chris.brown at acsalaska.net>>   desk (907) 550-8393
> >     <tel:%28907%29%20550-8393>
> >                                                          cell (907)
> >     632-8492 <tel:%28907%29%20632-8492>
> >     IP Engineer - ACS
> >
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>
> --
> ------------------------------------------------------------------------
> Christopher E. Brown   <chris.brown at acsalaska.net>   desk (907) 550-8393
>                                                      cell (907) 632-8492
> IP Engineer - ACS
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>