review of network tech

• types of network

LAN WAN -- figures /performances see the difference

• curcuit ->packet swithcing

store-and-forward

• 2 alternative approaches to transmit packets  

virtual curcuit  :Telephone system

datagram  :Postal system

• virtual curcuit

route is established;store-and-forward sheme;vc number need to be carried by a packet

intermediate nodes contain a table created during route establishment

• datagram

independent entity, no garantee; route dynamically decide the next node

out of order; a node crashes queued packets lost; duplicate

faster,flexible,handle congestion/failed links

• delays