Design Philosophy of the DARPA Internet Protocols CSCI 634, Fall 2010

Fundamental goals (top-level)   High utilization by multiplex  Packet switching Inter-connect heterogeneous networks  Gateway: store and forward packets These two determine the structure of Internet

Second level goals        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   Only end-point maintains the states  We lose the state information associated with the end-host, only when the end-host itself is dead Gateways are stateless   Tolerate any number of intermediate failures Much easy to engineer than replication

Type of service    TCP supports reliable sequenced data delivery  Virtual circuit UDP provides the basic datagram service Multiple services could be constructed out of basic datagram building block  Not as easy as expected  Lack of flexibility

Varieties of networks     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      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  No individual connection state is maintained at routers  Datagram is a basic building block  Datagram represents the minimum network service assumption

TCP design decision   Flow control and acknowledgement are byte based, not packet-based  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)   More attention to    Accounting Resource management Operations of different ASes (BGP) Better building block than datagram   Flow-based Soft-state