Re: Lossy cogent p2p experiences?

[Masataka Ohta <mohta () necom830 hpcl titech ac jp>]

Mark Tinka wrote:

> > Wrong. It can be performed only at the edges by policing total
> > incoming traffic without detecting flows.
>
> I am not talking about policing in the core, I am talking about 
> detection in the core.

I'm not talking about detection at all.

> Policing at the edge is pretty standard. You can police a 50Gbps EoMPLS 
> flow coming in from a customer port in the edge. If you've got N x 
> 10Gbps links in the core and the core is unable to detect that flow in 
> depth to hash it across all those 10Gbps links, you can end up putting 
> all or a good chunk of that 50Gbps of EoMPLS traffic into a single 
> 10Gbps link in the core, despite all other 10Gbps links having ample 
> capacity available.

Relying on hash is a poor way to offer wide bandwidth.

If you have multiple parallel links over which many slow
TCP connections are running, which should be your assumption,
the proper thing to do is to use the links with round robin
fashion without hashing. Without buffer bloat, packet
reordering probability within each TCP connection is
negligible.

Faster TCP may suffer from packet reordering during slight
congestion, but the effect is like that of RED.

Anyway, in this case, the situation is:

:Moreover, as David Hubbard wrote:
:> I've got a non-rate-limited 10gig circuit

So, if you internally have 10 parallel 1G circuits expecting
perfect hashing over them, it is not "non-rate-limited 10gig".

                                                Masataka Ohta