questions asked during network engineer interview

Wed Jul 22 09:53:30 UTC 2020

> William Herrin
> Sent: Tuesday, July 21, 2020 8:21 PM
> 
> On Mon, Jul 20, 2020 at 9:57 PM Mark Tinka <mark.tinka at seacom.com>
> wrote:
> > Suffice it to say, to this day, we still don't know what SDN means to
> > us, hehe.
> 
> Hi Mark,
> 
> The Software Defined Network concept started as, "Let's use commodity
> hardware running commodity operating systems to form the control plane
> for our network devices." The concept has expanded somewhat to: "Lets use
> commodity hardware running commodity operating systems AS our network
> devices." For example, if you build a high-rate firewall with DPDK on Linux,
> that's now considered SDN since its commodity hardware, commodity OS
> and custom packet handling (DPDK) that skips the OS.
> 
The higher level takeaway would be: 
"Modularity based on abstraction is the way things get done”
− Barbara Liskov

Abstractions -> Interfaces -> Modularity
This applies at the individual device level as well as you described above, 
however I'd say that application of these principles at the network-wide level is also very beneficial to service providers, (Device -> Network -> Service -> Product -> Offer).
This vision was first realized by AT&T in their ECOMP framework which (along with Open-O) is now morphed to ONAP. This idea has now been adopted by many service providers as well as commercial products.      

adam