Re: [arch-d] possible new IAB programme on Internet resilience

[Yaakov Stein <[e-mail]>]

Resilience is widely used in transport networks as a synonym for Automatic Protection Switching,
which typically replaces a failed path in less than 50 milliseconds.
So, while I agree that resilience is the ability to respond to an actual failure, it is not hypothetical or necessarily of long time duration.

Robustness is used in system design and computer science to mean the ability to avoid failure despite disturbances or unexpected inputs.
Failure is defined (e.g., G.805) as the inability to provide the service or to meet the user's expectations.
Note that unlike resilience, robustness is always with respect to some disturbance type, and that a system can be robust to X but not to Y.
For example, a network designed to be robust with respect to link failures will contain a lot of redundant links,
but then it will not be robust with respect to increasing traffic levels (and vice versa).

Y(J)S

-----Original Message-----
From: Architecture-discuss [mailto:[e-mail]] On Behalf Of Stephane Bortzmeyer
Sent: 23/12/2019 10:00
To: Stephen Farrell <[e-mail]>
Cc: [e-mail]
Subject: Re: [arch-d] possible new IAB programme on Internet resilience

On Sat, Dec 21, 2019 at 01:23:18AM +0000,  Stephen Farrell <[e-mail]> wrote  a message of 271 lines which said:

> > Indeed, the current project of charter seems to be more about 
> > robustness than about resilience.
> 
> Sorry - I'm not really following any of the above comments.  Can one 
> of you try explain some more?

Typically, robustness is the ability to withstand shocks without cracking, and resilience is the ability, once you have cracked, to restart afterwards. I suggest that the word "robustness" is a better fit for what we are trying to achieve (an Internet that will keep going, may be in degraded mode, when problems/attacks occur). "Resilience" would be adapted for a (very hypothetical) case where everything was down and we try to resume activity. (Thought
experiment: all the DNS root name servers were destroyed and we must agree on a new set, without beging able to communicate together, except by IP addresses.)

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