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Network Architecture:
Design Philosophies
IS250
Spring 2010
John Chuang
[email protected]
Outline
 Design philosophy of ARPANET
- Packet switching versus circuit switching
 End-to-end design principle
 Tussles in cyberspace
 Re-designing the Internet
John Chuang IS250 UC Berkeley
2
History of the Internet
1961:
1969:
1974:
1983:
1984:
1995:
Leonard Kleinrock: queuing theory
shows effectiveness of packet switching
Dept. of Defense (ARPA) sponsors the development of a
packet-switched network, called the ARPANET. First
four nodes at UCLA, SRI, Utah, UCSB.
Vint Cerf and Bob Kahn proposes TCP/IP.
ARPANET adopts TCP/IP. At this time, the ARPANET
has 200 routers.
National Science Foundation (NSF) funds a TCP/IP
based backbone network. This backbone grows into the
NSFNET, which becomes the successor of the ARPANET.
NSF stops funding of NSFNET. The Internet is
completely commercial.
John Chuang IS250 UC Berkeley
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ARPANET Design Philosophy
 Fundamental goal:
- “Effective multiplexed utilization of interconnected
networks”
- Q: what was alternative?
 Fundamental structure of the Internet:
- “A packet switched communications facility in which a
number of distinguishable networks are connected
together using packet communications processors
called gateways which implement a store and forward
packet forwarding algorithm”
John Chuang IS250 UC Berkeley
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Packet Switching vs.
Circuit Switching
 “The technique selected for multiplexing
was packet switching. An alternative such
as circuit switching could have been
considered, but the applications being
supported, such as remote login, were
naturally served by the packet switching
paradigm”
John Chuang IS250 UC Berkeley
5
Circuit Switching
 Circuit switching
used in
traditional
telephony:
- Requires establishment and teardown of circuit
- Fixed bandwidth resources (e.g., 64kbps for voice
channel) dedicated to each call, even if actual data
transmission rate is lower
- Not efficient for ‘bursty’ traffic sources
- Low jitter (delay variations) important for real-time
John Chuangapplications
IS250 UC Berkeley
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Packet Switching
 Data transmitted in
small packets
- Single message may
be split into multiple
packets
- Every packet contains
full control info (e.g.,
destination address) in header
- Packets may take different paths
- Packets may arrive out of order
- Packets may be lost or corrupted (need recovery mechanism)
 Statistical multiplexing possible
- Works well with ‘bursty’ traffic
John Chuang IS250 UC Berkeley
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Packet Switching vs.
Circuit Switching
 “The technique selected for multiplexing
was packet switching. An alternative such
as circuit switching could have been
considered, but the applications being
supported, such as remote login, were
naturally served by the packet switching
paradigm”
John Chuang IS250 UC Berkeley
10
ARPANET Design Goals
 Fundamental goal:
- Effective multiplexed utilization of interconnected networks
 Second level goals:
-
Survivability
Support multiple types of service
Accommodate variety of networks
Permit distributed management of resources
Cost effective
Host attachment with low level of effort
Resource accountability
John Chuang IS250 UC Berkeley
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Discussion
 Did the ordering of the goals matter?
 What does ‘fate-sharing’ mean?
 What does ‘stateless packet switches’
mean?
 Can you think of additional goals not
present in the original list?
John Chuang IS250 UC Berkeley
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End-to-End Argument
 What is the E2E argument?
 What is the connection between the E2E
argument and “fate-sharing” and
“stateless switches”?
John Chuang IS250 UC Berkeley
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End-to-End Argument
 In a layered architecture, how do you
divide functionality across the layers?
Application Layer
HTTP, FTP, NNTP, SMTP,
telnet, ...
Transport Layer
TCP, UDP
Network Layer
IP
Data Link Layer
Ethernet,
FDDI, SONET
Physical Layer
coax, twisted pair, fiber,
wireless, ...
Appl
end-to-end
Appl
Trans
port
end-to-end
Trans
port
Net
work
Net
work
point-to-point
Net
work
Net
work
Link
Link
point-to-point
Link
Link
Host A
John Chuang IS250 UC Berkeley
Router 1
Router 2
Host B
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End-to-End Argument
 Think twice (or thrice) about implementing a
functionality that you think is useful for an
application at a lower layer
 What are the reasons for implementing a
functionality at a lower layer?
 What are the costs/pitfalls of implementing a
functionality at a lower layer?
 How is the E2E argument reflected (or not) in
the TCP/IP architecture?
John Chuang IS250 UC Berkeley
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Tussle in Cyberspace
 Design principles
- Design for variation in outcome
- Modularize design along tussle boundaries
- Design for choice
John Chuang IS250 UC Berkeley
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Tussle Spaces
 Economics
- Consumer choice necessary for competition
-
Address portability (minimize switching cost)
Value pricing (market segmentation; price discrimination)
Open access
User-directed routing
 Trust
- Where to implement what functionality?
- Who decides on policy?
- Identity
 Innovation
- Openness to innovation (E2E)
- Incentives for innovation (user choice)
John Chuang IS250 UC Berkeley
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Redesigning the Internet
 Why? What’s wrong with the current
Internet?
John Chuang IS250 UC Berkeley
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