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Chapter 21

Trivial FileTransfer Protocol

(TFTP)

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CONTENTSCONTENTS• MESSAGES• CONNECTION• DATA TRANSFER• UDP PORTS• TFTP EXAMPLE• TFTP OPTIONS• SECURITY• APPLICATIONS

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TFTP uses the services of UDP TFTP uses the services of UDP on the well-known port 69.on the well-known port 69.

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MESSAGES

21.121.1

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Figure 21-1

Message categories

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Figure 21-2

RRQRead request

Mode: netascii or octet

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Figure 21-3

WRQWrite request

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Figure 21-4

DATA format

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Figure 21-5

ACK format

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Figure 21-6

ERROR format

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CONNECTION

21.221.2

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Figure 21-7

Connection establishment

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DATATRANSFER

21.321.3

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Figure 21-8Sorcerer’s apprentice bug

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UDPPORTS

21.421.4

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Figure 21-9

UDP port numbers used by TFTP

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21.521.5

TFTPEXAMPLE

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Figure 21-10

TFTPexample

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TFTPOPTIONS

21.621.6

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SECURITY

21.721.7

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Figure 21-11

TELNET with FTP for security

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21.821.8

APPLICATIONS

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Figure 21-12

Use of TFTP with BOOTP