10GE TOR port buffers (was Re: 10G switch recommendaton)

Fri Jan 27 16:35:16 UTC 2012

Hi,

Is there a reason switch vendors 1U TOR 10GE aggregation switches are
all cut-through and there are no models with deep buffers?
I've ben looking at all vendors I can think of and all have the same models.

TOR switches as cut-through with little buffers, and chassis based
boxes with deep buffers.

TOR:
Juniper EX4500		208KB/10GE (4MB shared per PFE)
Cisco 4900M			728KB/10GE (17.5MB shared)
Cisco Nexus 3064		140KB/10GE	(9MB shared)
Cisco Nexus 5000		680KB/10GE
Force10 S2410		I can't find it anymore, but it wasn't much
Arista 7148SX			123KB/10GE	(80KB per port plus 5MB dynamic)		
Arista 7050S			173KB/10GE (9MB shared)
Brocade VDX 6730-32	170KB/10GE
Brocade TurboIron 24X	85KB/10GE
HP 6600-24XG		4500KB/10GE	
HP 5820-24XG-SFP+	87KB/10GE	
Extreme Summit X650	375KB/10GE

Chassis:
Juniper EX8200-8XS		512MB/10GE
Cisco WS-X6708-10GE		32MB/10GE (or 24MB)
Cisco N7K-M132XP-12		36MB/10GE
Arista DCS-7548S-LC		48MB/10GE
Brocade BR-MLX-10Gx8-X	128MB/10GE (not sure)

1GE aggregation.
Force10 S60		1250MB shared
HP 5830			3000MB shared

I am at a loss why there are no 10GE TOR switches with deep buffers.
Apparently there is a need for deep buffers as the vendors make them
available in the chassis linecards.
There also are deep buffer 1GE aggregation switches.

Is there some (technical) reason for this?
I can imagine some vendors would say that you need to scale up to a
chassis if you need deep buffers, but at least one vendor should be
able to get quite some customers with a 10G deep buffer TOR switch.

I understand that flow-control should prevent loss with microbursts,
but in my customers get adverse effects, with strong negative
performance if they let flow-control do its thing.

Any pointers why this is, or if there is a solution for microburst
loss would be greatly appreciated.

Thanks,

Bas