[j-nsp] MX104 Limitations

Saku Ytti saku at ytti.fi
Wed Jun 24 14:22:35 EDT 2015

On (2015-06-24 08:08 -0500), Colton Conor wrote:


> 1.       No fabric redundancy due to fabric-less design. There is no switch
> fabric on the MX104, but there is on the rest of the MX series. Not sure if
> this is a bad or good thing?

I'd say categorically good thing. Less latency, less places for congestion,
less things to break.

> 4.       No IX chipsets for the 10G uplinks (i.e. no packet
> pre-classification, the IX chip is responsible for this function as well as
> GE to 10GE i/f adaptation)

4x10GE MICs do not have IX Chip, as they are driven directly by MQ's built-in
PHY, same goes for MX80 chassis ports.
2x10GE MICs otoh do not use MQ PHY and thus need to have IX chip.

MX104 is special, because MQ PHY cannot drive SFP+, so the chassis ports
do not connect directly MQ, as you'd expect (no one would expect IX here, as
it never happened before):

4x10GE MIC/MX80 => MQ<->physical-port
2x10GE MIC      => MQ<->IX<->physical-port
MX104 chassis   => MQ<->IX<->bcm84728<->physical-port

> 5.       QX Complex supports HQoS on MICs only, not on the integrated 4
> 10GE ports on the PMC. I.e. no HQoS support on the 10GE uplinks

This is capacity issue, QX can't really do much more than maybe 20Gbps bidir,
so it's marketing decision not to allow configuration of MQ for the chassis
ports, to avoid running to oversub. This is same as in MX80.
However Juniper does support HQoS on MQ ports, just not per-vlan, so you can
connect subrate service to chassis port and run queues inside that subrate

> 8.       BFD can be supported natively in the TRIO chipset.  On the MX104,
> it is not supported in hardware today.  BFD is run from the single core
> P2020 MPC.

I'm 99% certain that inline BFD is supported.

> 10.   MX104 operating temperature: -40 to 65C, but MX5, MX10, MX40, MX80
> and MX80-48T are all 0-40C all are TRIO based. Seems odd that the MX104
> would support a different temperature range. There are only 3 temperature
> hardened MICs for this chassis on the datasheet: (1) 16 x T1/E1 with CE,
> (2) 4 x chOC3/STM1 & 1 x chOC12/STM4 with CE, (3) 20 x 10/100/1000 Base-T.

Target market was different. MX80 was going to sit in a DC, which is properly
cooled and has deep racks. MX104 was going to sit in a telco pop, which has
shallow racks and dubious cooling.


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