Flow based architecture in data centers(more specifically Telco Clouds)

Saku Ytti saku at ytti.fi
Mon Feb 10 09:51:26 UTC 2020


On Sun, 9 Feb 2020 at 23:09, Rod Beck <rod.beck at unitedcablecompany.com> wrote:

> I am curious about the distinction about the flow versus non-flow architecture for data centers and I am also fascinated by the separate issue of WAN architecture for these

Based on the context of the OP's question, he is talking about
architecture where some components, potentially network devices, are
flow-aware, instead of doing LPM lookup per packet, they are doing LPM
lookup per flow.
This comes up every few years in various formats, because with
flow-lookup you have one expensive LPM lookup per flow and multiple
cheap LEM lookups. However the LEM table size is unbounded and easily
abusable leading to a set of very complex problems.

There are of course a lot of variation what OP might mean. Network
might be for example entirely LEM lookup with extremely small table,
by using stack of MPLS labels, zero LPM lookups. This architecture
could be made so that when server needs to send something say video to
a client, it asks orchestration for permission, telling I need to send
x GB to DADDR K with rate at least Z and no more than Y, orchestration
could then tell the server to start sending at time T0 and impose MPLS
label stack of [l1, l2, l3, l4, l5]

Orchestration would know exactly which links traffic traverses, how
long will it be utilised and how much free capacity there is. Network
would be extremely dumb, no IP lookups ever, only thousands of MPLS
labels in FIB, so entirely on-chip lookups of trivial cost.

-- 
  ++ytti



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