ARP the address resolution protocol,09信管二班 第二组,ARP,The question The relationship of the physical address and the IP address The Solution,Get the physical address from the IP address,IP address is used for network layer addressing, while data link layer address is the physical address. Thats to say，the data link layer hardware does not understand internet addresses .,This caused a qusetion, How do IP addresses get mapped onto data link layer addresses，such as Ethernet ？,6,Address Resolution Protocol，RFC 826 地址解析协议：IP address MAC address,IP,LANs,MANs,WANs,ICMP,IGMP,ARP,RARP,Network Layer,Network Access Layer,Transport Layer,Application Layer,Internet Control Message Protocol,Internet Group Management Protocol,Request For Comments,Internet Protocol,Address Resolution Protocol,Reverse Address Resolution Protocol,7,Addresses,Host identifier IP addressPhysical address,Network,Name（logic）,Address（physic）,ARP,Logical address,Physical address,The first way to solve the problem,Let us start out by seeing how a user on host 1 sends a packet to a user on host 2. Let us assume the sender knows the name of the intended receiver , possibly something like maryeagle.cs.uni.edu. The first step is to find the IP address for host 2, known as eagle .cs.uni.edu This lookup is performed by the Domain Name System, which we will study in Chap.7. For the moment,we will just assume that DNS returns the IP address for host 2 (192.31.65.5).,The second,A: 192.231.49.240,E: 219.231.49.248,Im looking for the physical address of a node whose IP address is: 219.231.49.248,I am the node you are looking for, and my physical address is: 00-53-45-00-00-00,Request,Request,Request,Reply,Request,Broadcast,Unicast,B: 192.231.49.242,C: 219.231.49.244,D: 219.231.49.246,Thank you！,