Part_3_Pieces_of_the_puzzle

Part_3_Pieces_of_the_puzzle - Pieces of the Puzzle EE450...

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EE450, USC, Zahid 1 Pieces of the Puzzle EE450: Introduction to Computer Networks Professor A. Zahid
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EE450, USC, Zahid 2 Burning Questions z How does a host/router get the MAC address of another host/router on the same LAN? z Answer: Address Resolution Protocol: ARP z How does a host get the IP address of another host across the Internet? z Answer : Domain Name Services: DNS z How does a host get it’s own IP address? z Answer: Dynamic Host Configuration Protocol (DHCP) z How do we distinguish between two or more applications running on the same host? z Answer: Port Numbers/Sockets
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EE450, USC, Zahid 3 223.1.1.1 223.1.1.2 223.1.1.3 223.1.1.4 223.1.2.9 223.1.2.2 223.1.2.1 223.1.3.2 223.1.3.1 223.1.3.27 A B C z A has a Packet to send to B. z A has the IP address of B and it knows that B is located on the same network. z A encapsulate the packet inside a link-layer frame destination addresses destination addresses B’s MAC addr A’s MAC addr A’s IP addr B’s IP addr IP payload Packet frame FCS
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EE450, USC, Zahid 4 Question #1: How does a Host/Router get the MAC address of another Host/Router on the same LAN?
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EE450, USC, Zahid 5 Address Resolution Protocol z Each IP node (Host, Router) on LAN has ARP module/table z ARP Cache Table: IP/MAC address mappings for some LAN nodes z Cache lifetime ~ 20 min Question: how to determine MAC address of B given B’s IP address?
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EE450, USC, Zahid 6 ARP (Continued) z Address Resolution Protocol binds an IP address to a media (link) address z ARP is a simple request-response protocol z Host “A” broadcasts a request packet containing IP address of “B”. Broadcast MAC address is FF:FF:FF:FF:FF:FF. All hosts receive the ARP inquiry z Host “B” recognizes its IP address z Host “B” sends a response (not a broadcast) packet to first host containing its MAC address z Host “A” caches address mapping for later use z ARP is a local, “Plug and Play” Protocol
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EE450, USC, Zahid 7 ARP Operation
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EE450, USC, Zahid 8 ARP Packet
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EE450, USC, Zahid 9 Four Cases of ARP use
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EE450, USC, Zahid 10 Four Cases of ARP use (Cont.)
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EE450, USC, Zahid 11 Proxy ARP
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EE450, USC, Zahid 12 Question #2: How does a Host get the IP address of another Host across the Internet?
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EE450, USC, Zahid 13 Domain Name Services (DNS) z DNS is a TCP/IP client server application protocol that allow host and name servers to
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Part_3_Pieces_of_the_puzzle - Pieces of the Puzzle EE450...

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