[j-nsp] Segment Routing Real World Deployment (was: VPC mc-lag)

[joel jaeggli]

On 7/8/18 01:34, Mark Tinka wrote:
> 
> 
> On 7/Jul/18 23:54, Aaron Gould wrote:
> 
>> Thanks Mark, I haven't been aware of any buffer deficiency in my
>> 4550's.  If something adverse is occurring, I'm not aware.
> 
> The EX4550 has only 4MB of shared buffer memory. The EX4600 has only 12MB.
> 
> You need the "set class-of-service shared-buffer percent 100" command to
> ensure some ports don't get starved of buffer space (which will manifest
> as dropped frames, e.t.c.).
> 
> The Arista 7280R series switches have 4GB of buffer space on the
> low-end, all the way to 8GB, 12GB, 16GB, 24GB and 32GB as you scale up.

As they are a matrix of cell forwarders either attached to each other or
to a fabric it's probably more proper to think of that as 4GB of packet
buffer per asic. There is in fact a small amount onboard the asic and
then the large dollop of offboard gddr5.  while memory is still shared
among the locally attached ports it's unlikely that anything is going to
starve.

> 
>>
>> Thanks for the warning about large VC... I don't really intend on
>> going past the (2) stacked.  After we outgrow it, I'll move on.
> 
> We are dropping the VC idea going forward. Simpler to just have enough
> bandwidth between a switch and the router that you can predict.
> 
> Mark.
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