Mailing List Archive

On 2019-03-14 13:40 -0400, Andrey Kostin wrote:

> Accidentally found that MX series datasheet now mentions MPC-10E with
> 400G ports
> https://www.juniper.net/assets/us/en/local/pdf/datasheets/1000597-en.pdf
[...]
> the MPC-10E protects existing investments

Gah, I hate that wording. To me it sounds like "sunk cost fallacy"
and "throwing good money after bad"... (I'm not necessarily saying
that applies to these cards. It's just that I have heard the words
"protect your investment" too many times when it would be much
cheaper and better to throw out and replace the old stuff entirely.
Seeing that in advertisments thus trigger my bullsh*t klaxons.)


> MPC10E-10C
> Modular port concentrator with 8xQSPF28 multirate
> ports (10/40/100GbE) plus 2xQSFP56-DD multirate
> ports (10/40/100/400GbE)
> MPC10E-15C
> Modular port concentrator with 12xQSPF28 multirate
> ports (10/40/100GbE) plus 3xQSFP56-DD multirate
> ports (10/40/100/400GbE)

It seems these are oversubscribed to the backplane. 8×100G + 2×400G
is 1.6 Tbit/s, and 12×100G + 3×400G is 2.4 Tbit/s, but all three of
MX240, MX480 and MX960 are listed as having 1.5 Tbit/s max per slot.
(And is that 1.5 Tbit/s in *and* out, or is that just 750 Gbit/s per
direction?)

And nothing for 400G DWDM/coherent, that I can see. I expect service
providers would like that, to run 400G on their long distance links
without having to have external transponders.

For our own use, I'm also hoping for linecards supporting 50G ports
(specifically, 50Gbase-LR) soonish. We have two MX480s as our border
routers (provided by our ISP) and currently have 100G uplinks to the
ISP, and are connecting our datacenter to the MX480s using multiple
10G links to our DC spines. We are kind of hoping to be able to up-
grade to 50G connections next year, or possibly the year after that.


/Bellman

> It seems these are oversubscribed to the backplane. 8?100G + 2?400G
> is 1.6 Tbit/s, and 12?100G + 3?400G is 2.4 Tbit/s, but all three of
> MX240, MX480 and MX960 are listed as having 1.5 Tbit/s max per slot.
> (And is that 1.5 Tbit/s in *and* out, or is that just 750 Gbit/s per
> direction?)
As I understand it, when a 400G port is enabled, 3 of the 100G ports are made un-available (not sure whether there is an option for sub-rate on the 400G port keeping more of the 100G ports available), hence there will be a limit of 1.5 Tbps per slot with no over-subscription. It is actually a 15x100G card... each group of 5 ports can enable one of its ports as 400G, thereby disabling three of its other 100G ports... there is 500Gbps of capacity per port group = available as 5 x 100G, or 1 x 400G + 1 x 100G.

The card with less capacity (ie. 2 groups of 5 ports, rather than 3 groups of 5 ports) just reduces the electronics and thereby the power consumption by 1/3.

I hope this helps

Tim.

Tim Rayner
Optical Engineer, AARNet Pty Ltd
street address: Building 9, Banks Street, YARRALUMLA ACT 2600
postal address: GPO Box 1559, CANBERRA ACT 2601
t. +61 2 6222 3575 f. +61 2 6222 3535 e. Tim.Rayner@aarnet.edu.au
w. www.aarnet.edu.au
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On Mon, Mar 18, 2019 at 10:48 PM Thomas Bellman <bellman@nsc.liu.se> wrote:

> Gah, I hate that wording. To me it sounds like "sunk cost fallacy"
> and "throwing good money after bad"... (I'm not necessarily saying
> that applies to these cards. It's just that I have heard the words
> "protect your investment" too many times when it would be much
> cheaper and better to throw out and replace the old stuff entirely.
> Seeing that in advertisments thus trigger my bullsh*t klaxons.)

Cheaper is subjective. To a small and dynamic shop CAPEX may represent
majority of cost. To an incumbent CAPEX may be entirely irrelevant,
money is cheap, but approving hardware to network may be massive
multiyear project. This is why platforms like GSR had so long tail.

--
++ytti
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On 2019-03-18 21:05 UTC, Tim Rayner wrote:

> As I understand it, when a 400G port is enabled, 3 of the 100G ports
> are made un-available (not sure whether there is an option for sub-rate
> on the 400G port keeping more of the 100G ports available), hence there
> will be a limit of 1.5 Tbps per slot with no over-subscription. It is
> actually a 15x100G card... each group of 5 ports can enable one of its
> ports as 400G, thereby disabling three of its other 100G ports... there
> is 500Gbps of capacity per port group = available as 5 x 100G, or 1 x
> 400G + 1 x 100G.

That makes sense. And I'm not opposed to oversubscribed linecards,
as long as it's clear that they are, and how the oversubscription
works (port groups, et.c). Presumably Juniper will put up a page
with more details soon, as they have for other linecards.

/Bellman

On 2019-03-18 23:24 +0200, Saku Ytti wrote:

> Cheaper is subjective. To a small and dynamic shop CAPEX may represent
> majority of cost. To an incumbent CAPEX may be entirely irrelevant,
> money is cheap, but approving hardware to network may be massive
> multiyear project. This is why platforms like GSR had so long tail.

It's just too often used even when the customer *is* capex sensitive,
to fool them into believing they are saving money on the hardware.

"Buy this chassis based switch! It costs twice as much as the fixed-
config datacenter switch, gives you half the number of ports [and the
ports are heavily oversubscribed], but four years later you can just
buy more and newer linecards [each costing as much as an entire fixed-
config switch] instead of replacing the entire switch! [.Oops, we
forgot to tell you that the new linecards will require a new super-
visor card as well.] Protecting your investment [putting *your*
money in *our* coffers] is something we are good at!"

I've seen that kind of marketing and sales techniques, concentrating
on the capex (and being misleading, if not outright lying, about it),
too many times, and people falling for it. I've kind of become allergic
to that wording...

Sorry for the rant...


/Bellman

> Thomas Bellman
> Sent: Monday, March 18, 2019 11:26 PM
>
> On 2019-03-18 23:24 +0200, Saku Ytti wrote:
>
> > Cheaper is subjective. To a small and dynamic shop CAPEX may represent
> > majority of cost. To an incumbent CAPEX may be entirely irrelevant,
> > money is cheap, but approving hardware to network may be massive
> > multiyear project. This is why platforms like GSR had so long tail.
>
> It's just too often used even when the customer *is* capex sensitive, to fool
> them into believing they are saving money on the hardware.
>
> "Buy this chassis based switch! It costs twice as much as the fixed- config
> datacenter switch, gives you half the number of ports [and the ports are
> heavily oversubscribed], but four years later you can just buy more and
> newer linecards [each costing as much as an entire fixed- config switch]
> instead of replacing the entire switch! [.Oops, we forgot to tell you that the
> new linecards will require a new super- visor card as well.] Protecting your
> investment [putting *your* money in *our* coffers] is something we are
> good at!"
>
> I've seen that kind of marketing and sales techniques, concentrating on the
> capex (and being misleading, if not outright lying, about it), too many times,
> and people falling for it. I've kind of become allergic to that wording...
>
> Sorry for the rant...
>
It's definitely one for the decentralization at the edge musing, that is big monolithic PEs vs smaller (even purpose/service specific) PEs.

adam


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