Computer Networks. Network Layer. Where are we?. Will Layer 2 Networking Suffice?. Motivation. Connect various link technologies to form a larger internetwork Universal addressing scheme required General purpose use Hides underlying technologies from end user
A router can interconnect networks that use different technologies, including different media and media access techniques, physical addressing schemes or frame formats.
Well be primarily concerned with addressing and routing
Good IP addressing tutorial: http://www.3com.com/nsc/501302.html
An IP address does not identify a specific computer. Instead, each IP address identifies a connection between a computer and a network. A computer with multiple network connections (e.g., a router) must be assigned one IP address for each connection.
Advertise 188.8.131.52/22 instead of 184.108.40.206,220.127.116.11, 18.104.22.168 and 22.214.171.124
The CIDR Report: http://www.employees.org/~tbates/cidr-report.html
Since each destination in a routing table corresponds to a network, the number of entries in a routing table is proportional to the number of networks in the internetwork. Caveat: you can use a "default" route to forward to when route is unknown or when no route specific information is available.
The destination address in a datagram header always refers to the ultimate destination. When a router forwards the datagram to another router, the address of the next hop does not appear in the datagram header.