[Bloat] RED against bufferbloat

[Mikael Abrahamsson]

On Wed, 25 Feb 2015, MUSCARIELLO Luca IMT/OLN wrote:

> Doing FQ in silicon is easy. It must be very easy as I did myself in a 
> MIPS Ikanos Vx185 chipset and I am not an hardware expert. This was for 
> a CPE with a 5X1Gbps ports.

I guess we have different definitions on what "silicon" is. Mine is 
"ASIC". If it has a MIPS CPU (and the CPU does forwarding), then it's not 
"silicon", then it's done in CPU.

I keep hearing from vendors that queues are expensive. The smallest FQ 
implementation that seems to be reasonable has 32 queues. Let's say we 
have 5k customers per port on a BNG, that equates to 160k queues.

Compare that to an efficient active ethernet p-t-p ETTH deployment without 
BNG at all, where the access L2 switch is the one doing policing. What 
would be the cost to equip this device with FQ per port?

> If you go a little deeper in the network and you pick an OLT you won't

I don't do PON.

> find much intelligence. A little deeper and in a local aggregation 
> router (all vendors) you'll find what you would need to implement FQ. A

If it's a BNG yes. These linecards with hundreds of thousands of queues 
are a lot more expensive than a linecard without these queues. Usually 
today there are 3-4 queues per customer, now we want to expand this to 32 
or more. What is the cost increase for this?

If you put a BNG in there with lots of intelligence then the cost of 
adding the FQ machinery might not be too bad. If you don't have the BNG at 
all, what is the cost then? I still believe it will be cheaper to try to 
do this in the CPE.

> Some "positive" view: access with Gbps (up to 1Gbps) with a range of RTT 
> (1ms to 100ms) will need smarter mechanisms in the equipment as 
> inefficiencies will be crystal clear and business consequences will be 
> substantially different.

Please elaborate. I'd say FIFO is less harmful at these speeds because of 
TCP inefficiencies meaning most end systems won't come up in high enough 
transfer rates to saturate that part of the network. Now the bottle neck 
will move elsewhere.

-- 
Mikael Abrahamsson    email: swmike at swm.pp.se