Design Philosophy of the
DARPA Internet Protocols
CSCI 634, Fall 2010
Fundamental goals (top-level)
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High utilization by multiplex
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Packet switching
Inter-connect heterogeneous networks
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Gateway: store and forward packets
These two determine the structure of Internet
Second level goals
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Fault-tolerance (V)
Support multiple type of services (X)
Accommodate a variety of networks (V)
Distributed resource management (V)
Cost-effective (V)
Easy host attachment (V))
Accountability (X)
Fate-sharing
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Only end-point maintains the states
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We lose the state information associated
with the end-host, only when the end-host
itself is dead
Gateways are stateless
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Tolerate any number of intermediate
failures
Much easy to engineer than replication
Type of service
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TCP supports reliable sequenced data delivery
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Virtual circuit
UDP provides the basic datagram service
Multiple services could be constructed out of
basic datagram building block
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Not as easy as expected
Lack of flexibility
Varieties of networks
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X.25 networks
Ethernet, token-ring
Satellite nets
Wireless networks
Key to flexibility: making a minimum assumptions
about the function that the net will provide
Architecture & Implementation
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Flexibility: various realization
Challenge: how to relate realization to
the proposed service ?
Performance!
Performance!!
Still Performance!!!
That is why we need networking research!
Internet Architecture:
Datagram
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No individual connection state is
maintained at routers
Datagram is a basic building block
Datagram represents the minimum
network service assumption
TCP design decision
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Flow control and acknowledgement are bytebased, not packet-based
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Insert control information into sequence space (X)
Broken into smaller packets (X)
Small packets can be gathered into one larger
packet
More accurate estimation of throughput
No EOL (End-Of-Letter) flag
Summary (many great points)
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More attention to
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Accounting
Resource management
Operations of different ASes (BGP)
Better building block than datagram
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Flow-based
Soft-state