Protocol Systems Design

Question 1

how is the hourglass model inaccurate?

Answer 1

kinda has two waists, one for ip4 and one for 6. tunnellling just makes waist a bit loopier

middleboxes fuck it a bit too (NAT and stuff)

Question 2

what are the two protocol success factors

Answer 2

scale and purpose
– Scale: How is it with increased usage?
– Purpose: How is it with unforeseen usage?

Example: HTTP
• Possible unintended consequences of “wildly
successful” protocols and systems.
• Side effects from original design, not considered for
unintended use, hinder future usage:
– e.g. text-based protocol for HTTP 1.0, 1.1.
• Possible performance problems:
– e.g. no pipelining in HTTP 1.0.
• Creeping functionality:
– e.g. HTTP used for firewall traversal.
• Security target:
– Attackers see successful protocols as good targets.
– Many security attacks on web services and systems.

Question 3

http is the waist of the hourglass?w hy

Answer 3

HTTP is popular for many applications:
– Mature web services infrastructure and frameworks.
– Good UI / client systems (browsers).
– Security mechanisms and protocols widely deployed.
– Web-based privacy issues, however (e.g. cookies)?
• HTTP used for firewall traversal:
– Usually not blocked by firewalls, due to popularity.
• Some existing services migrating to HTTP:
– e.g. DNS over HTTPS (DoH), RFC8484 (PS)
• Is HTTP becoming the new waist of the hourglass?[6]