ICMP/ARP and General Link-Layer

ICMP/ARP and General Link-Layer

EE122 Fall 2011 Scott Shenker

Materials with thanks to Jennifer Rexford, Ion Stoica, Vern Paxson

and other colleagues at Princeton and UC Berkeley

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Announcements

? Regrades done: pick up after class ? Demo on Wednesday

? Today's lecture is in two parts....

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Questions to be answered in 2nd half

? What does the link-layer do? ? How does it do it? ? Random access will be in Wednesday's lecture

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Questions to be answered in 1st half

? What must a host know before it can operate?

? Local information ? Remote information

? How can it find this information out?

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Obtaining information involves...

? Local: Bootstrapping an end host

? Learning its own configuration parameters (DHCP) ? Learning the link-layer addresses of other nodes (ARP)

? Global: Network control messages

? Internet Control Message Protocol (ICMP) ? Exploiting ICMP for discovering Internet path properties

Different mechanisms, for different environments

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