1. Internet Control Message Protocol (ICMP)

2. ICMP Internet Control Message Protocol –IP is the delivery standard at the TCP/IP internet layer –ICMP is the standard for supervisory messages –IP and ICMP are designed to work together; Even have adjacent RFC (standard) numbers –ICMP message is carried in the information field of an IP packet

3. ICMP Several ICMP Message Types –Error messages warn of problems –Not error correction, because there is no transmission of lost or damaged packets Error Message

4. ICMP Several ICMP Message Types –ICMP query request message asks host if it is active –Queried host sends back a query response message – Also called “Echo” and “Ping” Echo Request Echo Response

5. ICMP Several ICMP Message Types –Flow control: Source quench ICMP message asks other side to slow down Source Quench

6. Weak form of flow control When host sending packets gets source quench, it slows down If another source quench message arrives, slows down even more If source quench messages stop, slowly increases speed

7. ICMP ICMP Implements Other Supervisory Messages –We have only given a few important examples