IP Packet Switching

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Simple Network: Nodes and a Link
Node: computer
– End host: general-purpose computer, cell phone, PDA
–Network node: switch or router
• Link: physical medium connecting nodes
– Twisted pair: the wire that connects to telephones
–Coaxial cable: the wire that connects to TV sets
–Optical fiber: high-bandwidth long-distance links
– Space: propagation of radio waves, microwaves, …

Links: Delay and Bandwidth

Delay
–Latency for propagating data along the link
–Corresponds to the “length” of the link
–Typically measured in seconds
• Bandwidth
–Amount of data sent (or received) per unit time
–Corresponds to the “width” of the link
–Typically measured in bits per second

Beyond Directly-Connected Networks

• Switched network
–End hosts at the edge
–Network nodes that switch traffic
–Links between the nodes
• Multiplexing
–Many end hosts communicate over the network
–Traffic shares access to the same links