I'm trying write down the big picture: Ok, so I fire up my browser and type www.google.com into the address line and press enter:
1-my computer must first resolve www.google.com into an IP address. Some sort of nslookup command is called which sends a nslookup command inside a TCP? packet to the name server. Another TCP packet is received my computer with the result: A.B.C.D 2-my computer looks at my subnet address and realizes that I am not on the same network as google's A.B.C.D, so my computer sends out a HTTP GET request (again encapsulated inside a TCP packet, which is encapsulated inside an IP packet, which gets an Ethernet header and trailer which goes out ethernet card to the local area network, through a switch to a router (gateway) to it's destination. 3-If I *was* on the same subnet as A.B.C.D my computer would have send out an ARP packet asking for the MAC address of the host with IP address A.B.C.D. that server would have replied with it's MAC address, AA:BB:CC:DD:EE:FF and then my computer would have sent out a HTTP GET request inside a TCP inside a IP inside an Ethernet packet addressed to AA:BB:CC:DD:EE:FF. Questions: Is ARP used in scenerio #2? When is the RARP protocol used? Why do we have both IP and MAC addresses? Wouldn't just one of the two do nicely? (I guess routers would have to route based on MAC address...) Ideas? Obviously, it's been a while since 460. :-) Ryan ____________________ BYU Unix Users Group http://uug.byu.edu/ ___________________________________________________________________ List Info: http://uug.byu.edu/cgi-bin/mailman/listinfo/uug-list
