[j-nsp] WAN-PHY or STM-64 direct

[Richard A Steenbergen]

On Wed, Oct 27, 2010 at 12:07:06PM +0200, William Jackson wrote:
> We are debating which is the better route to go.
> 
> We already have STM-64/Ethernet capable ADM's and we were considering
> which would be the best option?
> 
> 1.	Terminate the STM-64 circuits into our MX boxes using type 3
> FPC's.
> 2.	Use a 10Gig WAN-PHY setup on the MX on an Ethernet line card and
> plug into an STM-64 interface on the ADM?

>From a purely technical perspective, the STM-64 is better in pretty much 
every respect. WAN PHY adds extra overhead, since you're essentially 
transporting the Ethernet frame inside the SONET frame, and in my 
experience will leave you with somewhere around 9.0-9.2 Gbps of actual 
IP capacity on the circuit (depending on packet sizes). A true STM-64 
circuit also has much lower overhead on small packets, and can do 
something like 26Mpps (forget the exact number off the top of my head), 
while a 10GE LAN PHY can only do 14.88Mpps. I'm too lazy to do the math 
on WAN PHY overhead, but suffice to say the pps will be a fair less than 
LAN PHY.

But from a cost perspective, the STM-64 will lose badly every time, 
especially on an MX (which is a Ethernet optimized platform). Lets just 
use the old DPC pricing for comparison, to avoid any arguments of "is it 
really line rate" on the new MPCs. A 10GE WAN PHY port will cost you 
$96k (list) / 4 = $24k, and consume 1/4th of a slot (and the numbers are 
realistically much better on the new Trio cards). To go with a true 
STM-64 on MX you'll need the MX-FPC3, which is $80k list, and consumes 2 
slots in the chassis. You'll also need the PC-1OC192-SON-XFP PIC, whic 
his $165k list. You've consumed half of the MX-FPC3, so your total cost 
per port would be $40k + $165k = $205k.

You tell me, would you rather pay $24k and use 1/4th a slot, or pay 
$205k and consume 4x more realestate on the box? For the difference in 
cost, sensible people (well, those who aren't either currently or 
planning to seek bankruptcy protection in the near future at any rate 
:P) will suck it up and just use the 10GE. :)

Or the better answer to your question is "3. Get transport gear which is 
capable of doing 10.25Gbps LAN PHY". Modern gear is all OTN capable, so 
you're no longer tied to "what alarms do you see?" to troubleshoot 
issues on the circuits. There is really no point in throwing away the 
extra 10% of capacity, unless you're tied to some legacy transport gear 
for some reason.

-- 
Richard A Steenbergen <ras at e-gerbil.net>       http://www.e-gerbil.net/ras
GPG Key ID: 0xF8B12CBC (7535 7F59 8204 ED1F CC1C 53AF 4C41 5ECA F8B1 2CBC)