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Protocol Problems and Architectural Issues

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Title: Protocol Problems and Architectural Issues


1
Protocol Problems and Architectural Issues
  • Steven M. Bellovin
  • ATT Labs Research
  • smb_at_research.att.com
  • http//www.research.att.com/smb

2
Different Kinds of Problems
  • Directory versus lookup
  • Surprising results
  • Chokepoints
  • Preemption

3
Directory Versus Lookup
  • A directory provides an imprecise, often
    interactive service
  • A lookup system provides reproducible,
    predictable answers, suitable for use by programs
  • The DNS was designed to be the latter

4
Surprising Results
  • Programs no longer do what you expect
  • Sometimes there is incorrect behavior sometimes,
    an error presents itself differently

5
Preemption
  • The Internet empowers the endpoints, not the
    middle
  • Endpoints applications, hosts, etc. can best
    decide how to handle error cases such as
    non-existent host name
  • Wildcards pre-empt that ability and put control
    in the center

6
What is the Internet?
  • TLD wildcards worked more-or-less adequately for
    (most) Web work and ordinary email.
  • The IAB noted that wildcards in general are
    mostly used for email only.
  • TLD wildcards do not work well for other
    protocols.
  • What is the minimum common protocol set for the
    Internet?

7
The Hourglass Model
  • Historically, the Internet architecture has been
    modeled as a hourglass Everything over IP, and
    IP over everything.
  • Is the new model Everything over HTTP?

8
Today's Hourglass
App
App
App
TCP
UDP
...
IP
...
Ethernet
Wireless
9
Tomorrow's Hourglass?
App
App
App
HTTP
TCP
IP
...
Ethernet
Wireless
10
Where Do Services Originate?
  • Most interesting new services come from the edges
  • Often, neither the ISPs nor the IETF are
    involved, most notably in the early days of the
    Web.
  • One part of the center's job is to stay out of
    the way of others' innovation we don't want to
    lock in the Internet into the mostly-http model

11
Why Wildcards Can Break Things
  • The DNS does not know what application the user
    wants
  • Is that an ancient mistake?
  • It mirrors the division of responsibility between
    IP and the upper layers
  • A service intended for one or two purposes will
    often fail for other purposes.
  • Even normal services can be complex

12
Conclusions
  • The Internet is built on a set of architectural
    assumptions
  • This architecture encouraged innovation
  • Breaking the architectural model will cause
    unforseeable failures, both in less-common
    existing software and for future ideas
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