March R. Smith - University of St Thomas - Minnesota QMCS Class Today Working the InternetWorking the Internet RoutingRouting Firewalling in generalFirewalling in general NATNAT

March R. Smith - University of St Thomas - Minnesota Working the Internet Layers againLayers again –What layers are needed? Division of laborDivision of labor –What part does the Internet itself do? –What jobs fall on host computers? –End-to-end concept; smart vs dumb

March R. Smith - University of St Thomas - Minnesota Routing How it happensHow it happens Routing tablesRouting tables Setting up routing tablesSetting up routing tables Persistence, “time to live”Persistence, “time to live”

March R. Smith - University of St Thomas - Minnesota Firewalls Firewall objectivesFirewall objectives –Provide outbound Internet access –Restrict/forbid inbound connections –Detect and block malicious traffic Types of firewall traffic controlTypes of firewall traffic control –Service control (allow specific protocols) –Direction control (in/out) –User control (source/destination) –Behavior control (bandwidth, application specific) 3 types of firewall filtering3 types of firewall filtering –Packet filtering –Connection filtering –Application filtering

March R. Smith - University of St Thomas - Minnesota Network Address Translation Original purpose: more hosts & addressesOriginal purpose: more hosts & addresses –Let “insiders” use restricted addresses –Translate them on the way out A ‘multiplexing’ mechanismA ‘multiplexing’ mechanism –Users share a “real” Internet address

March R. Smith - University of St Thomas - Minnesota Firewalls and LAN support Provide a few standard LAN servicesProvide a few standard LAN services –Router connection –DHCP

March R. Smith - University of St Thomas - Minnesota That’s it Questions?Questions? Creative Commons License This work is licensed under the Creative Commons Attribution-Share Alike 3.0 United States License. To view a copy of this license, visit or send a letter to Creative Commons, 171 Second Street, Suite 300, San Francisco, California, 94105, USA.