complexity and degrees of freedom in network design
DESCRIPTION
Complexity and Degrees of Freedom in Network Design. Michael Sinatra University of California, Berkeley 17 July 2007 Internet2/ESCC Joint Techs. Enhanced Gratuitous Logo Slide (EGLS). http://www.simonizusa.com/default.asp. Inspirations. - PowerPoint PPT PresentationTRANSCRIPT
![Page 1: Complexity and Degrees of Freedom in Network Design](https://reader035.vdocuments.mx/reader035/viewer/2022081604/56815e09550346895dcc61e4/html5/thumbnails/1.jpg)
Complexity and Degrees of Freedom in Network Design
Michael Sinatra
University of California, Berkeley
17 July 2007
Internet2/ESCC Joint Techs
![Page 2: Complexity and Degrees of Freedom in Network Design](https://reader035.vdocuments.mx/reader035/viewer/2022081604/56815e09550346895dcc61e4/html5/thumbnails/2.jpg)
Enhanced Gratuitous Logo Slide (EGLS)
![Page 3: Complexity and Degrees of Freedom in Network Design](https://reader035.vdocuments.mx/reader035/viewer/2022081604/56815e09550346895dcc61e4/html5/thumbnails/3.jpg)
Inspirations
• Terry Gray, Scott Sagan, Charles Perrow, Todd LaPorte, Martin Landau
• Poorly-designed networks and network disruption devices
• Greg Bell, Greg Travis and everyone who sent me interesting examples after the 5-9s talk
![Page 4: Complexity and Degrees of Freedom in Network Design](https://reader035.vdocuments.mx/reader035/viewer/2022081604/56815e09550346895dcc61e4/html5/thumbnails/4.jpg)
Redundancy in Systems
• Single points of “failure”• Probabilistic analysis of redundancy
– Redundant components can reduce the chances of failure
– A component with a 10% failure probability can be made redundant with another component with a 10% failure probability and yield a 1% system-failure probability
– But there’s a BIG assumption here!
![Page 5: Complexity and Degrees of Freedom in Network Design](https://reader035.vdocuments.mx/reader035/viewer/2022081604/56815e09550346895dcc61e4/html5/thumbnails/5.jpg)
Common-mode failures
• Components must be fully redundant! Are they?
• Classic example: aircraft engines
• Can you think of some networking examples?
![Page 6: Complexity and Degrees of Freedom in Network Design](https://reader035.vdocuments.mx/reader035/viewer/2022081604/56815e09550346895dcc61e4/html5/thumbnails/6.jpg)
Common-mode failures - example
FW FWSwitch
Outside
Inside
![Page 7: Complexity and Degrees of Freedom in Network Design](https://reader035.vdocuments.mx/reader035/viewer/2022081604/56815e09550346895dcc61e4/html5/thumbnails/7.jpg)
“Difficult” Failures
• You must be this tall to really break the network.
![Page 8: Complexity and Degrees of Freedom in Network Design](https://reader035.vdocuments.mx/reader035/viewer/2022081604/56815e09550346895dcc61e4/html5/thumbnails/8.jpg)
The Jordan Baker Phenomenon
• Nick: You're a rotten driver, either you ought to be more careful or you oughtn't drive at all.
• Jordan: I am careful.• Nick: No you're not.• Jordan: Well, other people are.• Nick: What's that got to do with it?• Jordan: They'll keep out of my way, It takes two to make an • accident.• Nick: Suppose you met somebody just as careless as yourself?• Jordan: I hope I never will, I hate careless people. That's why• I like you.
![Page 9: Complexity and Degrees of Freedom in Network Design](https://reader035.vdocuments.mx/reader035/viewer/2022081604/56815e09550346895dcc61e4/html5/thumbnails/9.jpg)
The Jordan Baker Phenomenon
• The problem is, there are too many careless devices on the network!
Client Firewall Net LB Server
![Page 10: Complexity and Degrees of Freedom in Network Design](https://reader035.vdocuments.mx/reader035/viewer/2022081604/56815e09550346895dcc61e4/html5/thumbnails/10.jpg)
Virtualization risks
• Adds complexity (but reduces it too!)
• Tightens coupling!
![Page 11: Complexity and Degrees of Freedom in Network Design](https://reader035.vdocuments.mx/reader035/viewer/2022081604/56815e09550346895dcc61e4/html5/thumbnails/11.jpg)
Common-mode failures - example
Switch/FW
Hosts
Router
To border
![Page 12: Complexity and Degrees of Freedom in Network Design](https://reader035.vdocuments.mx/reader035/viewer/2022081604/56815e09550346895dcc61e4/html5/thumbnails/12.jpg)
High-reliability organizations
• Demanded by high-reliability systems
• Organizational redundancy
• Change management
• Multiple approval/sign-off
![Page 13: Complexity and Degrees of Freedom in Network Design](https://reader035.vdocuments.mx/reader035/viewer/2022081604/56815e09550346895dcc61e4/html5/thumbnails/13.jpg)
High-reliability organizations
• Organizations can be made redundant in the same way as systems…
• …with many of the same problems– Common-mode failures– Non-linear complexity– And more…
![Page 14: Complexity and Degrees of Freedom in Network Design](https://reader035.vdocuments.mx/reader035/viewer/2022081604/56815e09550346895dcc61e4/html5/thumbnails/14.jpg)
Social shirking/buck passing
• Not really an analogous concept in physical systems
• Change-management difficulties
![Page 15: Complexity and Degrees of Freedom in Network Design](https://reader035.vdocuments.mx/reader035/viewer/2022081604/56815e09550346895dcc61e4/html5/thumbnails/15.jpg)
Overcompensation
• Has to do with the way physical systems are designed and operated
• Does anycast DNS encourage bad behavior?
![Page 16: Complexity and Degrees of Freedom in Network Design](https://reader035.vdocuments.mx/reader035/viewer/2022081604/56815e09550346895dcc61e4/html5/thumbnails/16.jpg)
Conclusions
• How do we deal with all of this?– Points of failure? Really points of freedom
(and that’s a bad thing)– We need to reduce degrees of freedom in
networks, not necessarily increase redundancy!
– Networks need to get simpler, not more complex!
![Page 17: Complexity and Degrees of Freedom in Network Design](https://reader035.vdocuments.mx/reader035/viewer/2022081604/56815e09550346895dcc61e4/html5/thumbnails/17.jpg)
Conclusions
• Risks exist where we may not expect them– Five-nines mentality– Virtualization– Network disruption devices: duh!– Security
• Maybe we shouldn’t assume that the system can be made fully reliable (Travis)
![Page 18: Complexity and Degrees of Freedom in Network Design](https://reader035.vdocuments.mx/reader035/viewer/2022081604/56815e09550346895dcc61e4/html5/thumbnails/18.jpg)
Conclusions
• Need to recognize trade-offs: In complex systems, “win-win scenarios” are very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very, very RARE!
![Page 19: Complexity and Degrees of Freedom in Network Design](https://reader035.vdocuments.mx/reader035/viewer/2022081604/56815e09550346895dcc61e4/html5/thumbnails/19.jpg)
Conclusion to the Conclusions