CS491 Design Problem D2
Due 10/14/02


The Internet can be thought of as two principal layers: the host
computers (on which users hold accounts) and a network of
routers.  Each host computer is connected to a router and has a
unique IP address.  Each router is connected to at least two
other routers by a physical line (e.g., telephone, cable,
microwave).  Each physical line is connected to the router at a
particular port.  Within each router is a routing table that
maps a target IP address into a port number.  Thus if a packet
containing destination address d (an IP address) arrives into a
router, the router looks up d in the routing table to get a port
number p, and then it transmits the packet out through that port
p.  Design a strategy for computing routing tables.  Include in
your strategy a time-out provision so that if a port is not
responding (downed link or downed router at the other end), the
router table entry can be marked and not used.  Include diagrams
to help you explain your design.