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Table Of Contents  The TCP/IP Guide
 9  TCP/IP Application Layer Protocols, Services and Applications (OSI Layers 5, 6 and 7)
      9  TCP/IP Key Applications and Application Protocols
           9  TCP/IP File and Message Transfer Applications and Protocols (FTP, TFTP, Electronic Mail, USENET, HTTP/WWW, Gopher)
                9  TCP/IP General File Transfer Protocols (FTP and TFTP)
                     9  Trivial File Transfer Protocol (TFTP)

Previous Topic/Section
TFTP Options and Option Negotiation
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Pages in Current Topic/Section
12
3
45
Next Page
TCP/IP Electronic Mail System: Concepts and Protocols (RFC 822, MIME, SMTP, POP3, IMAP)
Next Topic/Section

TFTP Message Formats
(Page 3 of 5)

Data Messages

Data blocks are sent using the simplified format shown in Table 236 and Figure 297.


Table 236: TFTP Data Message Format

Field Name

Size (bytes)

Description

Opcode

2

Operation Code: Specifies the TFTP message type. A value of 3 indicates a Data message.

Block #

2

Block Number: The number of the data block being sent.

Data

Variable

Data: 0 to 512 bytes of data.



Figure 297: TFTP Data Message Format

 


Acknowledgment Messages

Acknowledgments have the simplest format of any TFTP message, as you can see in Table 237 and Figure 298.


Table 237: TFTP Acknowledgment Message Format

Field Name

Size (bytes)

Description

Opcode

2

Operation Code: Specifies the TFTP message type. A value of 4 indicates an Acknowledgment message.

Block #

2

Block Number: The number of the data block being acknowledged; a value of 0 is used to acknowledge receipt of a write request without options, or to acknowledge receipt of an option acknowledgment.



Figure 298: TFTP Acknowledgment Message Format

 


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TFTP Options and Option Negotiation
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Pages in Current Topic/Section
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3
45
Next Page
TCP/IP Electronic Mail System: Concepts and Protocols (RFC 822, MIME, SMTP, POP3, IMAP)
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